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139-477: Belugas are common in its waters. This Chukotka Autonomous Okrug location article is a stub . You can help Misplaced Pages by expanding it . This article related to a river in the Russian Far East is a stub . You can help Misplaced Pages by expanding it . Beluga (whale) The beluga whale ( / b ɪ ˈ l uː ɡ ə / ; Delphinapterus leucas ) is an Arctic and sub-Arctic cetacean . It

278-570: A marine mammal buried beneath the fields of rural Vermont. The remains were found to be preserved in the sediments of the Champlain Sea , an extension of the Atlantic Ocean within the continent resulting from the rise in sea level at the end of the ice ages some 12,000 years ago. Today, the Charlotte whale is the official Vermont State Fossil (making Vermont the only state whose official fossil

417-456: A prion . The benefits of identification, however, are often greatly outweighed by the cost, as often there is no specific treatment, the cause is obvious, or the outcome of an infection is likely to be benign . The diagnosis is aided by the presenting symptoms in any individual with an infectious disease, yet it usually needs additional diagnostic techniques to confirm the suspicion. Some signs are specifically characteristic and indicative of

556-422: A runny nose . In certain cases, infectious diseases may be asymptomatic for much or even all of their course in a given host. In the latter case, the disease may only be defined as a "disease" (which by definition means an illness) in hosts who secondarily become ill after contact with an asymptomatic carrier . An infection is not synonymous with an infectious disease, as some infections do not cause illness in

695-417: A beluga to "talk" by using these sounds to identify three different objects, offering hope that humans may one day be able to communicate effectively with sea mammals. A similar observation has been made by Canadian researchers, where a beluga which died in 2007 "talked" when he was still a subadult. Another example is NOC , a beluga whale that could mimic the rhythm and tone of human language. Beluga whales in

834-431: A beluga's life expectancy was rarely more than 30 years. The method used to calculate the age of a beluga is based on counting the layers of dentine and dental cement in a specimen's teeth, which were originally thought to be deposited once or twice a year. The layers can be readily identified as one layer consists of opaque dense material and the other is transparent and less dense. It is therefore possible to estimate

973-421: A calf or if they are pregnant. After giving birth, dominant females will return the calf back to their mother. Additionally, male calves will temporarily leave their mothers to interact with an adult male who can serve as a role model for the calf, before they return to their mothers. Male calves are also frequently seen interacting with each other. Belugas are slower swimmers than the other toothed whales, such as

1112-401: A calf. Experts consider this interaction with the objects to be a substitute behavior . In captivity, mothering behavior among belugas depends on the individual. Some mothers are extremely attentive while other mothers are so blasé, that they have actually lost their calves. In aquaria, there have been cases where dominant females have stolen calves from mothers, particularly if they have lost

1251-425: A colonization is often only a matter of circumstance. Non-pathogenic organisms can become pathogenic given specific conditions, and even the most virulent organism requires certain circumstances to cause a compromising infection. Some colonizing bacteria, such as Corynebacteria sp. and Viridans streptococci , prevent the adhesion and colonization of pathogenic bacteria and thus have a symbiotic relationship with

1390-605: A discontinuous circumpolar distribution in Arctic and sub-Arctic waters. During the summer, they can mainly be found in deep waters ranging from 76°N to 80°N , particularly along the coasts of Alaska , northern Canada, western Greenland and northern Russia. The southernmost extent of their range includes isolated populations in the St. Lawrence River in the Atlantic, and the Amur River delta,

1529-469: A disease and are called pathognomonic signs; but these are rare. Not all infections are symptomatic. In children the presence of cyanosis , rapid breathing, poor peripheral perfusion, or a petechial rash increases the risk of a serious infection by greater than 5 fold. Other important indicators include parental concern, clinical instinct, and temperature greater than 40 °C. Many diagnostic approaches depend on microbiological culture to isolate

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1668-399: A disease. This amplification of nucleic acid in infected tissue offers an opportunity to detect the infectious agent by using PCR. Third, the essential tools for directing PCR, primers , are derived from the genomes of infectious agents, and with time those genomes will be known if they are not already. Thus, the technological ability to detect any infectious agent rapidly and specifically

1807-436: A dive, these animals will reduce their heart rate from 100 beats a minute to between 12 and 20. Blood flow is diverted away from certain tissues and organs and towards the brain , heart and lungs , which require a constant oxygen supply. The amount of oxygen dissolved in the blood is 5.5%, which is greater than that found in land-based mammals and is similar to that of Weddell seals (a diving marine mammal). One study found

1946-541: A female beluga had 16.5 L of oxygen dissolved in her blood. Lastly, the beluga's muscles contain high levels of the protein myoglobin , which stores oxygen in muscle. Myoglobin concentrations in belugas are several times greater than for terrestrial mammals, which help prevent oxygen deficiency during dives. Beluga whales often accompany bowhead whales , for curiosity and to secure polynya feasibility to breathe as bowheads are capable of breaking through ice from underwater by headbutting. Belugas play an important role in

2085-400: A few centimetres behind their eyes; each hole communicates with an external auditory conduit and an eardrum . It is not known if these organs are functional or simply vestigial . Belugas are able to see within and outside of water, but their vision is relatively poor when compared to dolphins. Their eyes are especially adapted to seeing under water, although when they come into contact with

2224-426: A few days be hundreds of miles away from that pod. Beluga whale pods can be grouped into three categories, nurseries (which consist of mother and calves), bachelors (which consist of all males) and mixed groups. Mixed groups contain animals of both sexes. Many hundreds and even thousands of individuals can be present when the pods join in river estuaries during the summer. This can represent a significant proportion of

2363-410: A few hours after birth; thereafter, they feed at intervals around an hour. Studies of captive females have indicated their milk composition varies between individuals and with the stage of lactation; it has an average content of 28% fat, 11% protein, 60.3% water, and less than 1% residual solids. The milk contains about 92 cal per ounce . The calves remain dependent on their mothers for nursing for

2502-423: A hospital stay. Lastly, a community-acquired infection is one in which the infection is acquired from a whole community. One manner of proving that a given disease is infectious, is to satisfy Koch's postulates (first proposed by Robert Koch ), which require that first, the infectious agent be identifiable only in patients who have the disease, and not in healthy controls, and second, that patients who contract

2641-524: A host with depressed resistance ( immunodeficiency ) or if they have unusual access to the inside of the body (for example, via trauma ). Opportunistic infection may be caused by microbes ordinarily in contact with the host, such as pathogenic bacteria or fungi in the gastrointestinal or the upper respiratory tract , and they may also result from (otherwise innocuous) microbes acquired from other hosts (as in Clostridioides difficile colitis ) or from

2780-502: A host. As bacterial and viral infections can both cause the same kinds of symptoms, it can be difficult to distinguish which is the cause of a specific infection. Distinguishing the two is important, since viral infections cannot be cured by antibiotics whereas bacterial infections can. There is a general chain of events that applies to infections, sometimes called the chain of infection or transmission chain . The chain of events involves several steps – which include

2919-450: A large frontal prominence. Another distinctive characteristic it possesses is the melon is malleable; its shape is changed during the emission of sounds. The beluga is able to change the shape of its head by blowing air around its sinuses to focus the emitted sounds. This organ contains fatty acids , mainly isovaleric acid (60.1%) and long-chain branched acids (16.9%), a very different composition from its body fat, and which could play

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3058-434: A link between virulence and transmissibility. Diagnosis of infectious disease sometimes involves identifying an infectious agent either directly or indirectly. In practice most minor infectious diseases such as warts , cutaneous abscesses , respiratory system infections and diarrheal diseases are diagnosed by their clinical presentation and treated without knowledge of the specific causative agent. Conclusions about

3197-486: A maximum frequency of 100 to 120 kHz when transferred to Kaneohe Bay in Hawaii . The difference in frequencies is thought to be a response to the difference in environmental noise in the two areas. In special circumstances, beluga whale sounds have been reported to resemble human speech. These animals communicate using sounds of high frequency; their calls can sound like bird songs, so belugas were nicknamed "canaries of

3336-403: A mechanism for regulating body temperature , as the arteries feeding the fin's muscles are surrounded by veins that dilate or contract to gain or lose heat. The tailfin is flat with two oar-like lobes, it does not have any bones, and is made up of hard, dense, fibrous connective tissue. The tailfin has a distinctive curvature along the lower edge. The longitudinal muscles of the back provide

3475-518: A number of basic dyes due to the electrostatic attraction between negatively charged cellular molecules and the positive charge on the dye. A cell is normally transparent under a microscope, and using a stain increases the contrast of a cell with its background. Staining a cell with a dye such as Giemsa stain or crystal violet allows a microscopist to describe its size, shape, internal and external components and its associations with other cells. The response of bacteria to different staining procedures

3614-404: A particular pathogen at all (no matter how little) but also is often used in a sense implying a clinically apparent infection (in other words, a case of infectious disease). This fact occasionally creates some ambiguity or prompts some usage discussion; to get around this it is common for health professionals to speak of colonization (rather than infection ) when they mean that some of

3753-493: A pathogen from the appropriate clinical specimen. In a microbial culture, a growth medium is provided for a specific agent. A sample taken from potentially diseased tissue or fluid is then tested for the presence of an infectious agent able to grow within that medium. Many pathogenic bacteria are easily grown on nutrient agar , a form of solid medium that supplies carbohydrates and proteins necessary for growth, along with copious amounts of water. A single bacterium will grow into

3892-429: A pathogen. A fluorescence microscope is then used to detect fluorescently labeled antibodies bound to internalized antigens within clinical samples or cultured cells. This technique is especially useful in the diagnosis of viral diseases, where the light microscope is incapable of identifying a virus directly. Other microscopic procedures may also aid in identifying infectious agents. Almost all cells readily stain with

4031-432: A patient's blood or other body fluids for antigens or antibodies that indicate presence of a specific pathogen that the doctor suspects. Other techniques (such as X-rays , CAT scans , PET scans or NMR ) are used to produce images of internal abnormalities resulting from the growth of an infectious agent. The images are useful in detection of, for example, a bone abscess or a spongiform encephalopathy produced by

4170-525: A period up to 475 days (15.8 months). During the mating season, the testes of belugas double in weight. Testosterone levels increase, but seems to be independent of copulation. Copulation typically takes place between 3 and 4 AM. Calves are born over a protracted period that varies by location. In the Canadian Arctic, calves are born between March and September, while in Hudson Bay , the peak calving period

4309-470: A persistent infection by infecting different cells of the body. Some viruses once acquired never leave the body. A typical example is the herpes virus, which tends to hide in nerves and become reactivated when specific circumstances arise. Persistent infections cause millions of deaths globally each year. Chronic infections by parasites account for a high morbidity and mortality in many underdeveloped countries. For infecting organisms to survive and repeat

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4448-403: A result of an infectious disease with immunosuppressive activity (such as with measles , malaria or HIV disease ). Primary pathogens may also cause more severe disease in a host with depressed resistance than would normally occur in an immunosufficient host. While a primary infection can practically be viewed as the root cause of an individual's current health problem, a secondary infection

4587-471: A result of their presence or activity within the normal, healthy host, and their intrinsic virulence (the severity of the disease they cause) is, in part, a necessary consequence of their need to reproduce and spread. Many of the most common primary pathogens of humans only infect humans, however, many serious diseases are caused by organisms acquired from the environment or that infect non-human hosts. Opportunistic pathogens can cause an infectious disease in

4726-466: A role in its echolocation system. Unlike many dolphins and whales, the seven vertebrae in the neck are not fused together, allowing the animal to turn its head laterally without needing to rotate its body. This gives the head a lateral manoeuvrability that allows an improved field of view and movement and helps in catching prey and evading predators in deep water. The rostrum has about eight to ten small, blunt and slightly curved teeth on each side of

4865-411: A severe illness affecting the brain, remain undiagnosed, despite extensive testing using the standard of care ( microbiological culture ) and state-of-the-art clinical laboratory methods. Metagenomic sequencing-based diagnostic tests are currently being developed for clinical use and show promise as a sensitive, specific, and rapid way to diagnose infection using a single all-encompassing test. This test

5004-417: A specific identification of an infectious agent only when such identification can aid in the treatment or prevention of the disease, or to advance knowledge of the course of an illness prior to the development of effective therapeutic or preventative measures. For example, in the early 1980s, prior to the appearance of AZT for the treatment of AIDS , the course of the disease was closely followed by monitoring

5143-500: A variety of fish species including saffron cod, rainbow smelt , walleye pollock, Pacific salmon , Pacific herring and several species of flounder and sculpin. The primary invertebrate consumed is shrimp. The primary prey item in regard to fish species for belugas in Bristol Bay appears to be the five species of salmon, with sockeye being the most prevalent. Smelt is also another common fish family eaten by belugas in this region. Shrimp

5282-432: A visible mound on the surface of the plate called a colony , which may be separated from other colonies or melded together into a "lawn". The size, color, shape and form of a colony is characteristic of the bacterial species, its specific genetic makeup (its strain ), and the environment that supports its growth. Other ingredients are often added to the plate to aid in identification. Plates may contain substances that permit

5421-405: A way of preserving heat. The crest is hard and, along with the head, can be used to open holes in ice up to 8 cm (3.1 in) thick. The beluga has a very specialised sense of hearing and its auditory cortex is highly developed. It can hear sounds within the range of 1.2 to 120  kHz , with the greatest sensitivity between 10 and 75 kHz, where the average hearing range for humans

5560-545: A wide range of pathogens , most prominently bacteria and viruses . Hosts can fight infections using their immune systems . Mammalian hosts react to infections with an innate response, often involving inflammation , followed by an adaptive response. Specific medications used to treat infections include antibiotics , antivirals , antifungals , antiprotozoals , and antihelminthics . Infectious diseases resulted in 9.2 million deaths in 2013 (about 17% of all deaths). The branch of medicine that focuses on infections

5699-420: A wide range of movement while they are searching for food on the ocean floor. Some animals have been observed to suck up water and then forcefully expel it to uncover their prey hidden in the silt on the seabed. As their teeth are neither large nor sharp, belugas must use suction to bring their prey into their mouths; it also means their prey has to be consumed whole, which in turn means it cannot be too large or

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5838-508: Is Coho salmon ( Oncorhynchus kisutch ). In general, the diets of these cetaceans consist mainly of fish; apart from those previously mentioned, other fish they feed on include capelin ( Mallotus villosus ), smelt , sole , flounder , herring , sculpin and other types of salmon . They also consume a great quantity of invertebrates, such as shrimp , squid , crabs , clams , octopus , sea snails , bristle worms and other deep-sea species. Belugas feed mainly in winter as their blubber

5977-429: Is debate as to whether cetacean vocalizations can constitute a language. A study conducted in 2015 determined that European beluga signals share physical features comparable to vowels. These sounds were found to be stable throughout time, but varied among different geographical locations. The further away the populations were from each other, the more varied the sounds were in relation to one another. The beluga inhabits

6116-404: Is 0.02 to 20 kHz. The majority of sounds are most probably received by the lower jaw and transmitted towards the middle ear . In the toothed whales, the lower jawbone is broad with a cavity at its base, which projects towards the place where it joins the cranium . A fatty deposit inside this small cavity connects to the middle ear. Toothed whales also possess a small external auditory hole

6255-509: Is a sequela or complication of that root cause. For example, an infection due to a burn or penetrating trauma (the root cause) is a secondary infection. Primary pathogens often cause primary infection and often cause secondary infection. Usually, opportunistic infections are viewed as secondary infections (because immunodeficiency or injury was the predisposing factor). Other types of infection consist of mixed, iatrogenic , nosocomial , and community-acquired infection. A mixed infection

6394-463: Is a member of the family Monodontidae , which is in turn part of the parvorder Odontoceti (toothed whales). The Irrawaddy dolphin was once placed in the same family, though recent genetic evidence suggests these dolphins belong to the family Delphinidae . The narwhal is the only other species within the Monodontidae. A skull has been discovered with intermediate characteristics supporting

6533-511: Is a slight difference on the sexual maturation period between males and females. The male beluga whales take seven to nine years to become sexually mature, while the females take four to seven years. Female belugas typically give birth to one calf every three years. Most mating occurs from February to May, but some occurs at other times of year. The beluga may have delayed implantation . Gestation has been estimated to last 12.0 to 14.5 months, but information derived from captive females suggests

6672-500: Is active but does not produce noticeable symptoms may be called inapparent, silent, subclinical , or occult . An infection that is inactive or dormant is called a latent infection . An example of a latent bacterial infection is latent tuberculosis . Some viral infections can also be latent, examples of latent viral infections are any of those from the Herpesviridae family. The word infection can denote any presence of

6811-439: Is adapted to life in the Arctic, with anatomical and physiological characteristics that differentiate it from other cetaceans. Amongst these are its all-white colour and the absence of a dorsal fin , which allows it to swim under ice with ease. It possesses a distinctive protuberance at the front of its head which houses an echolocation organ called the melon , which in this species is large and deformable. The beluga's body size

6950-404: Is also seen in other mammals, may be present in belugas in the wild. Hybrids have been documented between the beluga and the narwhal (specifically offspring conceived by a beluga father and a narwhal mother), as one, perhaps even as many as three, such hybrids were killed and harvested during a sustenance hunt. Whether or not these hybrids could breed remains unknown. The unusual dentition seen in

7089-423: Is an infection that is caused by two or more pathogens. An example of this is appendicitis , which is caused by Bacteroides fragilis and Escherichia coli . The second is an iatrogenic infection. This type of infection is one that is transmitted from a health care worker to a patient. A nosocomial infection is also one that occurs in a health care setting. Nosocomial infections are those that are acquired during

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7228-422: Is an initial site of infection from which organisms travel via the bloodstream to another area of the body. Among the many varieties of microorganisms , relatively few cause disease in otherwise healthy individuals. Infectious disease results from the interplay between those few pathogens and the defenses of the hosts they infect. The appearance and severity of disease resulting from any pathogen depend upon

7367-482: Is between that of a dolphin and a true whale, with males growing up to 5.5 m (18 ft) long and weighing up to 1,600 kg (3,530 lb). This whale has a stocky body. Like many cetaceans, a large percentage of its weight is blubber (subcutaneous fat). Its sense of hearing is highly developed and its echolocation allows it to move about and find breathing holes under sheet ice. Belugas are gregarious and form groups of 10 animals on average, although during

7506-510: Is currently available. The only remaining blockades to the use of PCR as a standard tool of diagnosis are in its cost and application, neither of which is insurmountable. The diagnosis of a few diseases will not benefit from the development of PCR methods, such as some of the clostridial diseases ( tetanus and botulism ). These diseases are fundamentally biological poisonings by relatively small numbers of infectious bacteria that produce extremely potent neurotoxins . A significant proliferation of

7645-504: Is in late June, and in Cumberland Sound , most calves are born from late July to early August. Births usually take place in bays or estuaries where the water is between 10 and 15 °C. Newborns are about 1.5 m (4 ft 11 in) long, weigh about 80 kg (180 lb), and are grey in colour. They are able to swim alongside their mothers immediately after birth. The newborn calves nurse under water and initiate lactation

7784-503: Is injured. All multicellular organisms are colonized to some degree by extrinsic organisms, and the vast majority of these exist in either a mutualistic or commensal relationship with the host. An example of the former is the anaerobic bacteria species, which colonizes the mammalian colon , and an example of the latter are the various species of staphylococcus that exist on human skin . Neither of these colonizations are considered infections. The difference between an infection and

7923-467: Is not an enzyme and has no metabolic function. Serological methods are highly sensitive, specific and often extremely rapid tests used to identify microorganisms. These tests are based upon the ability of an antibody to bind specifically to an antigen. The antigen, usually a protein or carbohydrate made by an infectious agent, is bound by the antibody. This binding then sets off a chain of events that can be visibly obvious in various ways, dependent upon

8062-411: Is one of two members of the family Monodontidae , along with the narwhal , and the only member of the genus Delphinapterus . It is also known as the white whale , as it is the only cetacean to regularly occur with this colour; the sea canary , due to its high-pitched calls; and the melonhead , though that more commonly refers to the melon-headed whale , which is an oceanic dolphin . The beluga

8201-399: Is rarely mistaken for any other species, because it is completely white or whitish-grey in colour. Calves are usually born grey, and by the time they are a month old, have turned dark grey or blue grey. They then start to progressively lose their pigmentation until they attain their distinctive white colouration, at the age of seven years in females and nine in males. The white colouration of

8340-425: Is referred to as infectious diseases . Infections are caused by infectious agents ( pathogens ) including: The signs and symptoms of an infection depend on the type of disease. Some signs of infection affect the whole body generally, such as fatigue , loss of appetite, weight loss, fevers , night sweats, chills, aches and pains. Others are specific to individual body parts, such as skin rashes , coughing , or

8479-404: Is referred to as colonization. Most humans are not easily infected. Those with compromised or weakened immune systems have an increased susceptibility to chronic or persistent infections. Individuals who have a suppressed immune system are particularly susceptible to opportunistic infections . Entrance to the host at host–pathogen interface , generally occurs through the mucosa in orifices like

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8618-501: Is similar to current PCR tests; however, an untargeted whole genome amplification is used rather than primers for a specific infectious agent. This amplification step is followed by next-generation sequencing or third-generation sequencing , alignment comparisons , and taxonomic classification using large databases of thousands of pathogen and commensal reference genomes . Simultaneously, antimicrobial resistance genes within pathogen and plasmid genomes are sequenced and aligned to

8757-608: Is stocky and fusiform (cone-shaped with the point facing backwards), and they frequently have folds of fat, particularly along the ventral surface. Between 40% and 50% of their body weight is fat, which is a higher proportion than for cetaceans that do not inhabit the Arctic, where fat only represents 30% of body weight. The fat forms a layer that covers all of the body except the head, and it can be up to 15 cm (5.9 in) thick. It acts as insulation in waters with temperatures between 0 and 18 °C, as well as being an important reserve during periods without food. The adult beluga

8896-439: Is that microbial colonization is very common even in environments that humans think of as being nearly sterile . Because it is normal to have bacterial colonization, it is difficult to know which chronic wounds can be classified as infected and how much risk of progression exists. Despite the huge number of wounds seen in clinical practice, there are limited quality data for evaluated symptoms and signs. A review of chronic wounds in

9035-432: Is that of a still extant animal). Its body is round, particularly when well fed, and tapers less smoothly to the head than the tail. The sudden tapering to the base of its neck gives it the appearance of shoulders, unique among cetaceans. The tail-fin grows and becomes increasingly and ornately curved as the animal ages. The flippers are broad and short—making them almost square-shaped. Preliminary investigations suggested

9174-617: Is the most prevalent invertebrate prey item. The most common prey items for belugas in Cook Inlet appear to be salmon, cod and smelt. Animals in captivity eat 2.5% to 3.0% of their body weight per day, which equates to 18.2 to 27.2 kg (40 to 60 lb). Like their wild counterparts, captive belugas were found to eat less in the fall. Foraging on the seabed typically takes place at depths between 20 and 40 m (66 and 131 ft), although they can dive to depths of 700 m (2,300 ft) in search of food. Their flexible necks provide

9313-556: Is thickest in later winter and early spring, and thinnest in the fall. Inuit observation has led scientists to believe that belugas do not hunt during migration, at least in Hudson Bay. The diet of Alaskan belugas is quite diverse and varies depending on season and migratory behavior. Belugas in the Beaufort Sea mainly feed on staghorn and shorthorn sculpin, walleye pollock , Arctic cod , saffron cod and Pacific sand lance . Shrimp are

9452-492: Is thought to number around 200,000. They are migratory and the majority of groups spend the winter around the Arctic ice cap ; when the sea ice melts in summer, they move to warmer river estuaries and coastal areas. Some populations are sedentary and do not migrate over great distances during the year. The native peoples of North America and Russia have hunted belugas for many centuries. They were also hunted by non-natives during

9591-456: Is unclear as to whether belugas receive a different number of layers per year depending on the age of the animal (for example young belugas may only receive an additional one layer per year), or simply just one layer per year or every other year. The species presents a moderate degree of sexual dimorphism , as the males are 25% longer than the females and are sturdier. Adult male belugas can range from 3.5 to 5.5 m (11 to 18 ft), while

9730-577: Is used in the taxonomic classification of microbes as well. Two methods, the Gram stain and the acid-fast stain, are the standard approaches used to classify bacteria and to diagnosis of disease. The Gram stain identifies the bacterial groups Bacillota and Actinomycetota , both of which contain many significant human pathogens. The acid-fast staining procedure identifies the Actinomycetota genera Mycobacterium and Nocardia . Biochemical tests used in

9869-588: The Journal of the American Medical Association 's "Rational Clinical Examination Series" quantified the importance of increased pain as an indicator of infection. The review showed that the most useful finding is an increase in the level of pain [likelihood ratio (LR) range, 11–20] makes infection much more likely, but the absence of pain (negative likelihood ratio range, 0.64–0.88) does not rule out infection (summary LR 0.64–0.88). Disease can arise if

10008-618: The Shantar Islands and the waters surrounding Sakhalin Island in the Sea of Okhotsk . Infectious disease An infection is the invasion of tissues by pathogens , their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease , also known as a transmissible disease or communicable disease , is an illness resulting from an infection. Infections can be caused by

10147-468: The oral cavity , nose, eyes, genitalia, anus, or the microbe can enter through open wounds. While a few organisms can grow at the initial site of entry, many migrate and cause systemic infection in different organs. Some pathogens grow within the host cells (intracellular) whereas others grow freely in bodily fluids. Wound colonization refers to non-replicating microorganisms within the wound, while in infected wounds, replicating organisms exist and tissue

10286-447: The polymerase chain reaction (PCR) method will become nearly ubiquitous gold standards of diagnostics of the near future, for several reasons. First, the catalog of infectious agents has grown to the point that virtually all of the significant infectious agents of the human population have been identified. Second, an infectious agent must grow within the human body to cause disease; essentially it must amplify its own nucleic acids to cause

10425-403: The "strep test", they can be inexpensive. Complex serological techniques have been developed into what are known as immunoassays . Immunoassays can use the basic antibody – antigen binding as the basis to produce an electro-magnetic or particle radiation signal, which can be detected by some form of instrumentation. Signal of unknowns can be compared to that of standards allowing quantitation of

10564-939: The 19th century and part of the 20th century. Hunting of belugas is not controlled by the International Whaling Commission , and each country has developed its own regulations in different years. Currently, some Inuit in Canada and Greenland, Alaska Native groups and Russians are allowed to hunt belugas for consumption as well as for sale, as aboriginal whaling is excluded from the International Whaling Commission 1986 moratorium on hunting. The numbers have dropped substantially in Russia and Greenland, but not in Alaska and Canada. Other threats include natural predators ( polar bears and killer whales ), contamination of rivers (as with polychlorinated biphenyl (PCBs) which bioaccumulate up

10703-534: The St. Lawrence River are listed as endangered. Belugas are one of the most commonly kept cetaceans in captivity and are housed in aquariums, dolphinariums and wildlife parks in North America, Europe and Asia. They are considered charismatic because of their docile demeanour and characteristic smile, communicative nature, and supple, graceful movement. The beluga was first described in 1776 by Peter Simon Pallas . It

10842-435: The ability of that pathogen to damage the host as well as the ability of the host to resist the pathogen. However, a host's immune system can also cause damage to the host itself in an attempt to control the infection. Clinicians, therefore, classify infectious microorganisms or microbes according to the status of host defenses – either as primary pathogens or as opportunistic pathogens . Primary pathogens cause disease as

10981-423: The age of the individual by extrapolating the number of layers identified and the estimated frequency with which the deposits are laid down. A 2006 study using radiocarbon dating of the dentin layers showed the deposit of this material occurs with a lesser frequency (once per year) than was previously thought. The study therefore estimated belugas can live for 70 or 80 years. However, recent studies suggest that it

11120-440: The air, the crystalline lens and the cornea adjust to overcome the associated myopia (the range of vision under water is short). A beluga's retina has cones and rods , which also suggests they can see in low light. The presence of cone cells indicates they can see colours, although this suggestion has not been confirmed. Glands located in the medial corner of their eyes secrete an oily, gelatinous substance that lubricates

11259-486: The ascending and descending movement of the tailfin, which has a similar thermoregulation mechanism to the pectoral fins. Belugas have a dorsal ridge, rather than a dorsal fin . The absence of the dorsal fin is reflected in the genus name of the species— apterus the Greek word for "wingless". The evolutionary preference for a dorsal ridge rather than a fin is believed to be an adaptation to under-ice conditions, or possibly as

11398-458: The basis of a biochemical diagnosis of an infectious disease. For example, humans can make neither RNA replicases nor reverse transcriptase , and the presence of these enzymes are characteristic., of specific types of viral infections. The ability of the viral protein hemagglutinin to bind red blood cells together into a detectable matrix may also be characterized as a biochemical test for viral infection, although strictly speaking hemagglutinin

11537-494: The beam of sound. They use this ability when moving around thick Arctic ice sheets, to find areas of unfrozen water for breathing, or air pockets trapped under the ice. Some evidence indicates that belugas are highly sensitive to noise produced by humans. In one study, the maximum frequencies produced by an individual located in San Diego Bay , California , were between 40 and 60 kHz. The same individual produced sounds with

11676-416: The beluga's mammalian ancestors, and are firmly bound together by connective tissue . The fins are small in relation to the size of the body, rounded and oar-shaped and slightly curled at the tips. These versatile extremities are mainly used as a rudder to control direction, to work in synchrony with the tailfin and for agile movement in shallow waters up to 3 m (9.8 ft) deep. The fins also contain

11815-596: The beluga's range varied with that of the polar ice packs expanding during ice ages and contracting when the ice retreated. Counter-evidence to this theory comes from the finding in 1849 of fossilised beluga bones in Vermont in the United States, 240 km (150 mi) from the Atlantic Ocean. The bones were discovered during construction of the first railroad between Rutland and Burlington in Vermont, when workers unearthed

11954-440: The belugas run the risk of it getting stuck in their throats. They also join into coordinated groups of five or more to feed on shoals of fish by steering the fish into shallow water, where the belugas then attack them. For example, in the estuary of the Amur River , where they mainly feed on salmon, groups of six or eight individuals join to surround a shoal of fish and prevent their escape. Individuals then take turns feeding on

12093-406: The bones of a mysterious animal in Charlotte . Buried nearly 10 ft (3.0 m) below the surface in a thick blue clay , these bones were unlike those of any animal previously discovered in Vermont. Experts identified the bones as those of a beluga. Because Charlotte is over 150 mi (240 km) from the nearest ocean, early naturalists were at a loss to explain the presence of the bones of

12232-463: The case of viral identification, a region of dead cells results from viral growth, and is called a "plaque". Eukaryotic parasites may also be grown in culture as a means of identifying a particular agent. In the absence of suitable plate culture techniques, some microbes require culture within live animals. Bacteria such as Mycobacterium leprae and Treponema pallidum can be grown in animals, although serological and microscopic techniques make

12371-472: The causative agent, Trypanosoma cruzi in a patient, which therefore makes it difficult to definitively make a diagnosis. In this case, xenodiagnosis involves the use of the vector of the Chagas agent T. cruzi , an uninfected triatomine bug, which takes a blood meal from a person suspected of having been infected. The bug is later inspected for growth of T. cruzi within its gut. Another principal tool in

12510-436: The cause of the disease are based upon the likelihood that a patient came in contact with a particular agent, the presence of a microbe in a community, and other epidemiological considerations. Given sufficient effort, all known infectious agents can be specifically identified. Diagnosis of infectious disease is nearly always initiated by medical history and physical examination. More detailed identification techniques involve

12649-431: The composition of patient blood samples, even though the outcome would not offer the patient any further treatment options. In part, these studies on the appearance of HIV in specific communities permitted the advancement of hypotheses as to the route of transmission of the virus. By understanding how the disease was transmitted, resources could be targeted to the communities at greatest risk in campaigns aimed at reducing

12788-484: The culture of infectious agents isolated from a patient. Culture allows identification of infectious organisms by examining their microscopic features, by detecting the presence of substances produced by pathogens, and by directly identifying an organism by its genotype. Many infectious organisms are identified without culture and microscopy. This is especially true for viruses, which cannot grow in culture. For some suspected pathogens, doctors may conduct tests that examine

12927-400: The destruction of the virus. Instrumentation can be used to read extremely small signals created by secondary reactions linked to the antibody – antigen binding. Instrumentation can control sampling, reagent use, reaction times, signal detection, calculation of results, and data management to yield a cost-effective automated process for diagnosis of infectious disease. Technologies based upon

13066-428: The diagnosis of infectious disease is microscopy . Virtually all of the culture techniques discussed above rely, at some point, on microscopic examination for definitive identification of the infectious agent. Microscopy may be carried out with simple instruments, such as the compound light microscope , or with instruments as complex as an electron microscope . Samples obtained from patients may be viewed directly under

13205-477: The early Pliocene (3–5 million years ago). Fossil evidence from Baja California and Virginia indicate the family once inhabited warmer waters. A fossil of the monodontid Casatia thermophila , from five million years ago, provides the strongest evidence that monodontids once inhabited warmer waters, as the fossil was found alongside fossils of tropical species such as bull and tiger sharks. The fossil record also indicates that, in comparatively recent times,

13344-445: The environment as a result of traumatic introduction (as in surgical wound infections or compound fractures ). An opportunistic disease requires impairment of host defenses, which may occur as a result of genetic defects (such as chronic granulomatous disease ), exposure to antimicrobial drugs or immunosuppressive chemicals (as might occur following poisoning or cancer chemotherapy ), exposure to ionizing radiation , or as

13483-426: The expression of symptoms is often atypical, making a clinical diagnosis based on presentation more difficult. Thirdly, diagnostic methods that rely on the detection of antibodies are more likely to fail. A rapid, sensitive, specific, and untargeted test for all known human pathogens that detects the presence of the organism's DNA rather than antibodies is therefore highly desirable. There is usually an indication for

13622-465: The eye and helps flush out foreign bodies. This substance forms a film that protects the cornea and the conjunctiva from pathogenic organisms. Studies on captive animals show they seek frequent physical contact with other belugas. Areas in the mouth have been found that could act as chemoreceptors for different tastes, and they can detect the presence of blood in water, which causes them to react immediately by displaying typical alarm behaviour. Like

13761-429: The females measure 3 to 4.1 m (9.8 to 13.5 ft). Males weigh between 1,100 and 1,600 kg (2,430 and 3,530 lb), and occasionally up to 1,900 kg (4,190 lb) while females weigh between 700 and 1,200 kg (1,540 and 2,650 lb). They rank as mid-sized species among toothed whales. Individuals of both sexes reach their maximum size by the time they are 10 years old. The beluga's body shape

13900-494: The first year, when their teeth appear. After this, they start to supplement their diets with shrimp and small fish. The majority of the calves continue nursing until they are 20 months old, although occasionally lactation can continue for more than two years, and lactational anoestrus may not occur. Alloparenting (care by females different from the mother) has been observed in captive belugas, including spontaneous and long-term milk production. This suggests this behaviour, which

14039-510: The fish. Estimations of the age of sexual maturity for beluga whales vary considerably; the majority of authors estimate males reach sexual maturity when they are between nine and fifteen years old, and females reach maturity between eight and fourteen years old. The average age at which females first give birth is 8.5 years and fertility begins to decrease when they are 25, eventually undergoing menopause, and ceasing reproductive potential with no births recorded for females older than 41. There

14178-570: The food chain), climate change and infectious diseases . The beluga was placed on the International Union for Conservation of Nature 's Red List in 2008 as being "near threatened"; the subpopulation from the Cook Inlet in Alaska is considered critically endangered and is under the protection of the United States' Endangered Species Act . Of all seven extant Canadian beluga populations, those inhabiting eastern Hudson Bay , Ungava Bay , and

14317-555: The former is now more popular. The English name comes from the Russian белу́га, which derives from the word белый ( bélyj ), meaning "white". Nowadays the word белу́га in Russian refers to the beluga sturgeon , while the whale is called almost similarly - белу́ха ("belúha"). The whale is also colloquially known as the "sea canary" on account of its high-pitched squeaks, squeals, clucks, and whistles. A Japanese researcher claimed that he taught

14456-451: The genome of a beluga whale was sequenced, comprising 2.327 Gbp of assembled genomic sequence that encoded 29,581 predicted genes. The authors estimated that the genome-wide sequence similarity between beluga whales and killer whales is 97.87%. The beluga's earliest known distinctive ancestors include the prehistoric Denebola brachycephala from the late Miocene epoch (9–10 million years ago), and Bohaskaia monodontoides , from

14595-403: The growth of some bacteria and not others, or that change color in response to certain bacteria and not others. Bacteriological plates such as these are commonly used in the clinical identification of infectious bacterium. Microbial culture may also be used in the identification of viruses : the medium, in this case, being cells grown in culture that the virus can infect, and then alter or kill. In

14734-484: The host's protective immune mechanisms are compromised and the organism inflicts damage on the host. Microorganisms can cause tissue damage by releasing a variety of toxins or destructive enzymes. For example, Clostridium tetani releases a toxin that paralyzes muscles, and staphylococcus releases toxins that produce shock and sepsis . Not all infectious agents cause disease in all hosts. For example, less than 5% of individuals infected with polio develop disease. On

14873-598: The host, preventing infection and speeding wound healing . The variables involved in the outcome of a host becoming inoculated by a pathogen and the ultimate outcome include: As an example, several staphylococcal species remain harmless on the skin, but, when present in a normally sterile space, such as in the capsule of a joint or the peritoneum , multiply without resistance and cause harm. An interesting fact that gas chromatography–mass spectrometry , 16S ribosomal RNA analysis, omics , and other advanced technologies have made more apparent to humans in recent decades

15012-463: The hypothesis that hybridisation is possible between these two species. The name of the genus , Delphinapterus , means "dolphin without fin" (from the Greek δελφίν ( delphin ), dolphin and απτερος ( apteros ), without fin) and the species name leucas means "white" (from the Greek λευκας ( leukas ), white). The Red List of Threatened Species gives both beluga and white whale as common names, though

15151-532: The identification of infectious agents include the detection of metabolic or enzymatic products characteristic of a particular infectious agent. Since bacteria ferment carbohydrates in patterns characteristic of their genus and species , the detection of fermentation products is commonly used in bacterial identification. Acids , alcohols and gases are usually detected in these tests when bacteria are grown in selective liquid or solid media. The isolation of enzymes from infected tissue can also provide

15290-413: The infection cycle in other hosts, they (or their progeny) must leave an existing reservoir and cause infection elsewhere. Infection transmission can take place via many potential routes: The relationship between virulence versus transmissibility is complex; with studies have shown that there were no clear relationship between the two. There is still a small number of evidence that partially suggests

15429-399: The infectious agent does not occur, this limits the ability of PCR to detect the presence of any bacteria. Given the wide range of bacterial, viral, fungal, protozoal, and helminthic pathogens that cause debilitating and life-threatening illnesses, the ability to quickly identify the cause of infection is important yet often challenging. For example, more than half of cases of encephalitis ,

15568-402: The infectious agent, reservoir, entering a susceptible host, exit and transmission to new hosts. Each of the links must be present in a chronological order for an infection to develop. Understanding these steps helps health care workers target the infection and prevent it from occurring in the first place. Infection begins when an organism successfully enters the body, grows and multiplies. This

15707-412: The jaw and a total of 36 to 40 teeth. Belugas do not use their teeth to chew, but for catching hold of their prey; they then tear them up and swallow them nearly whole. Belugas only have a single spiracle , which is located on the top of the head behind the melon, and has a muscular covering, allowing it to be completely sealed. Under normal conditions, the spiracle is closed and an animal must contract

15846-410: The killer whale and the common bottlenose dolphin , because they are less hydrodynamic and have limited movement of their tail-fins, which produce the greatest thrust. They frequently swim at speeds between 3 and 9 km/h (1.9 and 5.6 mph), although they are able to maintain a speed of 22 km/h for up to 15 min. Unlike most cetaceans, they are capable of swimming backwards. Belugas swim on

15985-425: The light microscope, and can often rapidly lead to identification. Microscopy is often also used in conjunction with biochemical staining techniques, and can be made exquisitely specific when used in combination with antibody based techniques. For example, the use of antibodies made artificially fluorescent (fluorescently labeled antibodies) can be directed to bind to and identify a specific antigens present on

16124-527: The most common invertebrate eaten, with octopus, amphipods and echiurids being other sources of invertebrate prey. The most common prey species for belugas in the Eastern Chukchi Sea appears to be shrimp, echiurid worms, cephalopods and polychaetes . The largest prey item consumed by beluga whales in the Eastern Chukchi Sea seems to be saffron cod. Beluga whales in the Eastern Bering Sea feed on

16263-416: The muscular covering to open the spiracle. A beluga's thyroid gland is larger than that of terrestrial mammals —weighing three times more than that of a horse—which helps it to maintain a greater metabolism during the summer when it lives in river estuaries. It is the marine cetacean that most frequently develops hyperplastic and neoplastic lesions of the thyroid. The fins retain the bony vestiges of

16402-531: The number of new infections. The specific serological diagnostic identification, and later genotypic or molecular identification, of HIV also enabled the development of hypotheses as to the temporal and geographical origins of the virus, as well as a myriad of other hypothesis. The development of molecular diagnostic tools have enabled physicians and researchers to monitor the efficacy of treatment with anti-retroviral drugs . Molecular diagnostics are now commonly used to identify HIV in healthy people long before

16541-455: The onset of illness and have been used to demonstrate the existence of people who are genetically resistant to HIV infection. Thus, while there still is no cure for AIDS, there is great therapeutic and predictive benefit to identifying the virus and monitoring the virus levels within the blood of infected individuals, both for the patient and for the community at large. Symptomatic infections are apparent and clinical , whereas an infection that

16680-514: The other hand, some infectious agents are highly virulent. The prion causing mad cow disease and Creutzfeldt–Jakob disease invariably kills all animals and people that are infected. Persistent infections occur because the body is unable to clear the organism after the initial infection. Persistent infections are characterized by the continual presence of the infectious organism, often as latent infection with occasional recurrent relapses of active infection. There are some viruses that can maintain

16819-425: The other one popped them. There have also been reports of beluga whales copying and imitating one another, similar to a game of Simon-says. There have also been reports of them displaying physical affection, via mouth to mouth contact. They also show a great deal of curiosity towards humans and frequently approach the windows in the tanks to observe them. Belugas also show a great degree of curiosity towards humans in

16958-450: The other toothed whales, their brains lack olfactory bulbs and olfactory nerves, which suggests they do not have a sense of smell. These cetaceans are highly sociable and they regularly form small groups, or pods, that may contain between two and 25 individuals, with an average of 10 members. Pods tend to be unstable, meaning individuals tend to move from pod to pod. Radio tracking has even shown belugas can start out in one pod and within

17097-539: The pathogens are present but that no clinically apparent infection (no disease) is present. Different terms are used to describe how and where infections present over time. In an acute infection, symptoms develop rapidly; its course can either be rapid or protracted. In chronic infection, symptoms usually develop gradually over weeks or months and are slow to resolve. In subacute infections, symptoms take longer to develop than in acute infections but arise more quickly than those of chronic infections. A focal infection

17236-551: The sea". Like the other toothed whales, belugas do not possess vocal cords and the sounds are probably produced by the movement of air between the nasal sacks, which are located near to the blowhole. Belugas are among the most vocal cetaceans. They use their vocalisations for echolocation, during mating and for communication. They possess a large repertoire, emitting up to 11 different sounds, such as cackles, whistles, trills and squawks. They make sounds by grinding their teeth or splashing, but they rarely use body language. There

17375-418: The single remaining skull indicates the hybrid hunted on the seabed, much as walruses do, indicating feeding habits different from those of either parent species. Belugas use sounds and echolocation for movement, communication, to find breathing holes in the ice, and to hunt in dark or turbid waters. They produce a rapid sequence of clicks that pass through the melon, which acts as an acoustic lens to focus

17514-411: The skin is an adaptation to life in the Arctic that allows belugas to camouflage themselves in the polar ice caps as protection against their main predators, polar bears and killer whales . Unlike other cetaceans, the belugas seasonally shed their skin. During the winter, the epidermis thickens and the skin can become yellowish, mainly on the back and fins. When they migrate to the estuaries during

17653-430: The sounds into a beam that is projected forward through the surrounding water. These sounds spread through the water at a speed of nearly 1.6 km per second, some four times faster than the speed of sound in air. The sound waves reflect from objects and return as echoes that are heard and interpreted by the animal. This enables them to determine the distance, speed, size, shape and the object's internal structure within

17792-673: The structure and function of marine resources in the Arctic Ocean , as they are the most abundant toothed whales in the region. They are opportunistic feeders; their feeding habits depend on their locations and the season. For example, when they are in the Beaufort Sea , they mainly eat Arctic cod ( Boreogadus saida ) and the stomachs of belugas caught near Greenland were found to contain rose fish ( Sebastes marinus ), Greenland halibut ( Reinhardtius hippoglossoides ) and northern shrimp ( Pandalus borealis ), while in Alaska their staple diet

17931-435: The summer, they can gather in the hundreds or even thousands in estuaries and shallow coastal areas. They are slow swimmers, but can dive to 700 m (2,300 ft) below the surface. They are opportunistic feeders and their diets vary according to their locations and the season. The majority of belugas live in the Arctic Ocean and the seas and coasts around North America, Russia, and Greenland; their worldwide population

18070-410: The summer, they rub themselves on the gravel of the riverbeds to remove the cutaneous covering. Like most toothed whales , the beluga has a compartment found at the centre of the forehead that contains an organ used for echolocation called a melon , which contains fatty tissue. The shape of the beluga's head is unlike that of any other cetacean, as the melon is extremely bulbous, lobed and visible as

18209-449: The surface between 5% and 10% of the time, while for the rest of the time they swim at a depth sufficient enough to cover their bodies. They do not jump out of the water like dolphins or killer whales. These animals usually only dive to depths to 20 m (66 ft), although they are capable of diving to greater depths. Individual captive animals have been recorded at depths between 400 and 647 m below sea level, while animals in

18348-457: The target antigen. To aid in the diagnosis of infectious diseases, immunoassays can detect or measure antigens from either infectious agents or proteins generated by an infected organism in response to a foreign agent. For example, immunoassay A may detect the presence of a surface protein from a virus particle. Immunoassay B on the other hand may detect or measure antibodies produced by an organism's immune system that are made to neutralize and allow

18487-559: The taxonomically classified pathogen genomes to generate an antimicrobial resistance profile – analogous to antibiotic sensitivity testing – to facilitate antimicrobial stewardship and allow for the optimization of treatment using the most effective drugs for a patient's infection. Metagenomic sequencing could prove especially useful for diagnosis when the patient is immunocompromised . An ever-wider array of infectious agents can cause serious harm to individuals with immunosuppression, so clinical screening must often be broader. Additionally,

18626-503: The test. For example, " Strep throat " is often diagnosed within minutes, and is based on the appearance of antigens made by the causative agent, S. pyogenes , that is retrieved from a patient's throat with a cotton swab. Serological tests, if available, are usually the preferred route of identification, however the tests are costly to develop and the reagents used in the test often require refrigeration . Some serological methods are extremely costly, although when commonly used, such as with

18765-545: The total population and is when they are most vulnerable to being hunted. They are cooperative animals and frequently hunt in coordinated groups. The animals in a pod are very sociable and often chase each other as if they are playing or fighting, and they often rub against each other. Often individuals will surface and dive together in a synchronized manner, in a behavior known as milling. In captivity, they can be seen to be constantly playing, vocalising and swimming around each other. In one case, one whale blew bubbles, while

18904-411: The use of live animals unnecessary. Viruses are also usually identified using alternatives to growth in culture or animals. Some viruses may be grown in embryonated eggs. Another useful identification method is Xenodiagnosis, or the use of a vector to support the growth of an infectious agent. Chagas disease is the most significant example, because it is difficult to directly demonstrate the presence of

19043-600: The wild have been recorded as diving to a depth of more than 700 m, with the greatest recorded depth being over 900 m. A dive normally lasts 3 to 5 minutes, but can last up to over 20 minutes. In the shallower water of the estuaries, a diving session may last around two minutes; the sequence consists of five or six rapid, shallow dives followed by a deeper dive lasting up to one minute. The average number of dives per day varies between 31 and 51. All cetaceans, including belugas, have physiological adaptations designed to conserve oxygen while they are under water. During

19182-492: The wild have been reported to imitate human voices. Mitochondrial DNA studies have shown modern cetaceans last shared a common ancestor between 25 and 34 million years ago The superfamily Delphinoidea (which contains monodontids, dolphins and porpoises) split from other toothed whales, odontoceti, between 11 and 15 million years ago. Monodontids then split from dolphins (Delphinidae) and later from porpoises (Phocoenidae), their closest relatives in evolutionary terms. In 2017

19321-477: The wild, and frequently swim alongside boats. They also play with objects they find in the water; in the wild, they do this with wood, plants, dead fish and bubbles they have created. During the breeding season, adults have been observed carrying objects such as plants, nets, and even the skeleton of a dead reindeer on their heads and backs. Captive females have also been observed displaying this behavior, carrying items such as floats and buoys, after they have lost

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