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Tuesday, September 3, 2024

Rabies

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Rabies

Rabies
A man suffering from rabies tied to a hospital bed.
A man with rabies, 1958
SpecialtyInfectious disease
SymptomsFever, extreme aversion to water, confusion, excessive salivary secretion, hallucinations, disrupted sleep, paralysis, coma, hyperactivity, headache, nausea, vomiting, anxiety
CausesRabies virus, Australian bat lyssavirus
PreventionRabies vaccine, animal control, rabies immunoglobulin
TreatmentSupportive care
MedicationIncurable
Prognosis~100% fatal after onset of symptoms
Deaths59,000 per year worldwide

Rabies is a viral disease that causes encephalitis in humans and other mammals. It was historically referred to as hydrophobia ("fear of water") due to the symptom of panic when presented with liquids to drink. Early symptoms can include fever and abnormal sensations at the site of exposure. These symptoms are followed by one or more of the following symptoms: nausea, vomiting, violent movements, uncontrolled excitement, fear of water, an inability to move parts of the body, confusion, and loss of consciousness. Once symptoms appear, the result is virtually always death. The time period between contracting the disease and the start of symptoms is usually one to three months but can vary from less than one week to more than one year. The time depends on the distance the virus must travel along peripheral nerves to reach the central nervous system.

Rabies is caused by lyssaviruses, including the rabies virus and Australian bat lyssavirus. It is spread when an infected animal bites or scratches a human or other animals. Saliva from an infected animal can also transmit rabies if the saliva comes into contact with the eyes, mouth, or nose. Globally, dogs are the most common animal involved. In countries where dogs commonly have the disease, more than 99% of rabies cases in humans are the direct result of dog bites. In the Americas, bat bites are the most common source of rabies infections in humans, and less than 5% of cases are from dogs. Rodents are very rarely infected with rabies. The disease can be diagnosed only after the start of symptoms.

Animal control and vaccination programs have decreased the risk of rabies from dogs in a number of regions of the world. Immunizing people before they are exposed is recommended for those at high risk, including those who work with bats or who spend prolonged periods in areas of the world where rabies is common. In people who have been exposed to rabies, the rabies vaccine and sometimes rabies immunoglobulin are effective in preventing the disease if the person receives the treatment before the start of rabies symptoms. Washing bites and scratches for 15 minutes with soap and water, povidone-iodine, or detergent may reduce the number of viral particles and may be somewhat effective at preventing transmission. As of 2016, only fourteen people were documented to have survived a rabies infection after showing symptoms. However, research conducted in 2010 among a population of people in Peru with a self-reported history of one or more bites from vampire bats (commonly infected with rabies), found that out of 73 individuals reporting previous bat bites, seven people had rabies virus-neutralizing antibodies (rVNA). Since only one member of this group reported prior vaccination for rabies, the findings of the research suggest previously undocumented cases of infection and viral replication followed by an abortive infection. This could indicate that people may have an exposure to the virus without treatment and develop natural antibodies as a result.

Rabies causes about 59,000 deaths worldwide per year, about 40% of which are in children under the age of 15. More than 95% of human deaths from rabies occur in Africa and Asia. Rabies is present in more than 150 countries and on all continents but Antarctica. More than 3 billion people live in regions of the world where rabies occurs. A number of countries, including Australia and Japan, as well as much of Western Europe, do not have rabies among dogs. Many Pacific islands do not have rabies at all. It is classified as a neglected tropical disease.

The global cost of rabies is estimated to be around US$ 8.6 billion per year including lost lives and livelihoods, medical care and associated costs, as well as uncalculated psychological trauma.

Etymology

The name rabies is derived from the Latin rabies, "madness". The Greeks derived the word lyssa, from lud or "violent"; this root is used in the genus name of the rabies virus, Lyssavirus.

Signs and symptoms

Animals with "dumb" rabies appear depressed, lethargic, and uncoordinated

The period between infection and the first symptoms (incubation period) is typically one to three months in humans. This period may be as short as four days or longer than six years, depending on the location and severity of the wound and the amount of virus introduced. Initial symptoms of rabies are often nonspecific such as fever and headache. As rabies progresses and causes inflammation of the brain and meninges, symptoms can include slight or partial paralysis, anxiety, insomnia, confusion, agitation, abnormal behavior, paranoia, terror, and hallucinations. The person may also have fear of water.

The symptoms eventually progress to delirium, and coma. Death usually occurs two to ten days after first symptoms. Survival is almost unknown once symptoms have presented, even with intensive care.

Rabies has also occasionally been referred to as hydrophobia ("fear of water") throughout its history. It refers to a set of symptoms in the later stages of an infection in which the person has difficulty swallowing, shows panic when presented with liquids to drink, and cannot quench their thirst. Saliva production is greatly increased, and attempts to drink, or even the intention or suggestion of drinking, may cause excruciatingly painful spasms of the muscles in the throat and larynx. Since the infected individual cannot swallow saliva and water, the virus has a much higher chance of being transmitted, because it multiplies and accumulates in the salivary glands and is transmitted through biting.

Hydrophobia is commonly associated with furious rabies, which affects 80% of rabies-infected people. This form of rabies causes irrational aggression in the host, which aids in the spreading of the virus through animal bites; a "foaming at the mouth" effect, caused by the accumulation of saliva, is also commonly associated with rabies in the public perception and in popular culture. The remaining 20% may experience a paralytic form of rabies that is marked by muscle weakness, loss of sensation, and paralysis; this form of rabies does not usually cause fear of water.

Cause

Rabies is caused by a number of lyssaviruses including the rabies virus and Australian bat lyssavirus. Duvenhage lyssavirus may cause a rabies-like infection.

The rabies virus is the type species of the Lyssavirus genus, in the family Rhabdoviridae, order Mononegavirales. Lyssavirions have helical symmetry, with a length of about 180 nm and a cross-section of about 75 nm. These virions are enveloped and have a single-stranded RNA genome with negative sense. The genetic information is packed as a ribonucleoprotein complex in which RNA is tightly bound by the viral nucleoprotein. The RNA genome of the virus encodes five genes whose order is highly conserved: nucleoprotein (N), phosphoprotein (P), matrix protein (M), glycoprotein (G), and the viral RNA polymerase (L).

To enter cells, trimeric spikes on the exterior of the membrane of the virus interact with a specific cell receptor, the most likely one being the acetylcholine receptor. The cellular membrane pinches in a procession known as pinocytosis and allows entry of the virus into the cell by way of an endosome. The virus then uses the acidic environment, which is necessary, of that endosome and binds to its membrane simultaneously, releasing its five proteins and single-strand RNA into the cytoplasm.

Once within a muscle or nerve cell, the virus undergoes replication. The L protein then transcribes five mRNA strands and a positive strand of RNA all from the original negative strand RNA using free nucleotides in the cytoplasm. These five mRNA strands are then translated into their corresponding proteins (P, L, N, G and M proteins) at free ribosomes in the cytoplasm. Some proteins require post-translational modifications. For example, the G protein travels through the rough endoplasmic reticulum, where it undergoes further folding, and is then transported to the Golgi apparatus, where a sugar group is added to it (glycosylation).

When there are enough viral proteins, the viral polymerase will begin to synthesize new negative strands of RNA from the template of the positive-strand RNA. These negative strands will then form complexes with the N, P, L and M proteins and then travel to the inner membrane of the cell, where a G protein has embedded itself in the membrane. The G protein then coils around the N-P-L-M complex of proteins taking some of the host cell membrane with it, which will form the new outer envelope of the virus particle. The virus then buds from the cell.

From the point of entry, the virus is neurotropic, traveling along the neural pathways into the central nervous system. The virus usually first infects muscle cells close to the site of infection, where they are able to replicate without being 'noticed' by the host's immune system. Once enough virus has been replicated, they begin to bind to acetylcholine receptors at the neuromuscular junction. The virus then travels through the nerve cell axon via retrograde transport, as its P protein interacts with dynein, a protein present in the cytoplasm of nerve cells. Once the virus reaches the cell body it travels rapidly to the central nervous system (CNS), replicating in motor neurons and eventually reaching the brain. After the brain is infected, the virus travels centrifugally to the peripheral and autonomic nervous systems, eventually migrating to the salivary glands, where it is ready to be transmitted to the next host.

Transmission

All warm-blooded species, including humans, may become infected with the rabies virus and develop symptoms. Birds were first artificially infected with rabies in 1884; however, infected birds are largely, if not wholly, asymptomatic, and recover. Other bird species have been known to develop rabies antibodies, a sign of infection, after feeding on rabies-infected mammals.

The virus has also adapted to grow in cells of cold-blooded vertebrates. Most animals can be infected by the virus and can transmit the disease to humans. Worldwide, about 99% of human rabies cases come from domestic dogs. Other sources of rabies in humans include bats, monkeys, raccoons, foxes, skunks, cattle, wolves, coyotes, cats, and mongooses (normally either the small Asian mongoose or the yellow mongoose).

Rabies may also spread through exposure to infected bears, domestic farm animals, groundhogs, weasels, and other wild carnivorans. However, lagomorphs, such as hares and rabbits, and small rodents, such as chipmunks, gerbils, guinea pigs, hamsters, mice, rats, and squirrels, are almost never found to be infected with rabies and are not known to transmit rabies to humans. Bites from mice, rats, or squirrels rarely require rabies prevention because these rodents are typically killed by any encounter with a larger, rabid animal, and would, therefore, not be carriers. The Virginia opossum (a marsupial, unlike the other mammals named in this paragraph, which are all eutherians/placental), has a lower internal body temperature than the rabies virus prefers and therefore is resistant but not immune to rabies. Marsupials, along with monotremes (platypuses and echidnas), typically have lower body temperatures than similarly sized eutherians. In 2024, reports emerged that rabies is spreading in South African seals, the outbreak may be the first ever documented in marine mammals.

The virus is usually present in the nerves and saliva of a symptomatic rabid animal. The route of infection is usually, but not always, by a bite. In many cases, the infected animal is exceptionally aggressive, may attack without provocation, and exhibits otherwise uncharacteristic behavior. This is an example of a viral pathogen modifying the behavior of its host to facilitate its transmission to other hosts. After a typical human infection by bite, the virus enters the peripheral nervous system. It then travels retrograde along the efferent nerves toward the central nervous system. During this phase, the virus cannot be easily detected within the host, and vaccination may still confer cell-mediated immunity to prevent symptomatic rabies. When the virus reaches the brain, it rapidly causes encephalitis, the prodromal phase, which is the beginning of the symptoms. Once the patient becomes symptomatic, treatment is almost never effective and mortality is over 99%. Rabies may also inflame the spinal cord, producing transverse myelitis.

Although it is theoretically possible for rabies-infected humans to transmit it to others by biting or otherwise, no such cases have ever been documented, because infected humans are usually hospitalized and necessary precautions taken. Casual contact, such as touching a person with rabies or contact with non-infectious fluid or tissue (urine, blood, feces), does not constitute an exposure and does not require post-exposure prophylaxis. But as the virus is present in sperm and vaginal secretions, it might be possible for rabies to spread through sex. There are only a small number of recorded cases of human-to-human transmission of rabies, and all occurred through organ transplants, most frequently with corneal transplantation, from infected donors.

Diagnosis

Rabies can be difficult to diagnose because, in the early stages, it is easily confused with other diseases or even with a simple aggressive temperament. The reference method for diagnosing rabies is the fluorescent antibody test (FAT), an immunohistochemistry procedure, which is recommended by the World Health Organization (WHO). The FAT relies on the ability of a detector molecule (usually fluorescein isothiocyanate) coupled with a rabies-specific antibody, forming a conjugate, to bind to and allow the visualisation of rabies antigen using fluorescent microscopy techniques. Microscopic analysis of samples is the only direct method that allows for the identification of rabies virus-specific antigen in a short time and at a reduced cost, irrespective of geographical origin and status of the host. It has to be regarded as the first step in diagnostic procedures for all laboratories. Autolysed samples can, however, reduce the sensitivity and specificity of the FAT. The RT PCR assays proved to be a sensitive and specific tool for routine diagnostic purposes, particularly in decomposed samples or archival specimens. The diagnosis can be reliably made from brain samples taken after death. The diagnosis can also be made from saliva, urine, and cerebrospinal fluid samples, but this is not as sensitive or reliable as brain samples. Cerebral inclusion bodies called Negri bodies are 100% diagnostic for rabies infection but are found in only about 80% of cases. If possible, the animal from which the bite was received should also be examined for rabies.

Some light microscopy techniques may also be used to diagnose rabies at a tenth of the cost of traditional fluorescence microscopy techniques, allowing identification of the disease in less-developed countries. A test for rabies, known as LN34, is easier to run on a dead animal's brain and might help determine who does and does not need post-exposure prevention. The test was developed by the Centers for Disease Control and Prevention (CDC) in 2018.

The differential diagnosis in a case of suspected human rabies may initially include any cause of encephalitis, in particular infection with viruses such as herpesviruses, enteroviruses, and arboviruses such as West Nile virus. The most important viruses to rule out are herpes simplex virus type one, varicella zoster virus, and (less commonly) enteroviruses, including coxsackieviruses, echoviruses, polioviruses, and human enteroviruses 68 to 71.

New causes of viral encephalitis are also possible, as was evidenced by the 1999 outbreak in Malaysia of 300 cases of encephalitis with a mortality rate of 40% caused by Nipah virus, a newly recognized paramyxovirus. Likewise, well-known viruses may be introduced into new locales, as is illustrated by the outbreak of encephalitis due to West Nile virus in the eastern United States.

Prevention

Almost all human exposure to rabies was fatal until a vaccine was developed in 1885 by Louis Pasteur and Émile Roux. Their original vaccine was harvested from infected rabbits, from which the virus in the nerve tissue was weakened by allowing it to dry for five to ten days. Similar nerve tissue-derived vaccines are still used in some countries, as they are much cheaper than modern cell culture vaccines.

The human diploid cell rabies vaccine was started in 1967. Less expensive purified chicken embryo cell vaccine and purified vero cell rabies vaccine are now available. A recombinant vaccine called V-RG has been used in Belgium, France, Germany, and the United States to prevent outbreaks of rabies in undomesticated animals. Immunization before exposure has been used in both human and nonhuman populations, where, as in many jurisdictions, domesticated animals are required to be vaccinated.

A young girl about to receive PEP after being bitten by an animal thought to be rabid

The Missouri Department of Health and Senior Services Communicable Disease Surveillance 2007 Annual Report states the following can help reduce the risk of contracting rabies:

  • Vaccinating dogs, cats, and ferrets against rabies
  • Keeping pets under supervision
  • Not handling wild animals or strays
  • Contacting an animal control officer upon observing a wild animal or a stray, especially if the animal is acting strangely
  • If bitten by an animal, washing the wound with soap and water for 10 to 15 minutes and contacting a healthcare provider to determine if post-exposure prophylaxis is required

28 September is World Rabies Day, which promotes the information, prevention, and elimination of the disease.

In Asia and in parts of the Americas and Africa, dogs remain the principal host. Mandatory vaccination of animals is less effective in rural areas. Especially in developing countries, pets may not be privately kept and their destruction may be unacceptable. Oral vaccines can be safely distributed in baits, a practice that has successfully reduced rabies in rural areas of Canada, France, and the United States. In Montreal, Quebec, Canada, baits are successfully used on raccoons in the Mount-Royal Park area. Vaccination campaigns may be expensive, but cost-benefit analysis suggests baits may be a cost-effective method of control. In Ontario, a dramatic drop in rabies was recorded when an aerial bait-vaccination campaign was launched.

The number of recorded human deaths from rabies in the United States has dropped from 100 or more annually in the early 20th century to one or two per year due to widespread vaccination of domestic dogs and cats and the development of human vaccines and immunoglobulin treatments. Most deaths now result from bat bites, which may go unnoticed by the victim and hence untreated.

Treatment

After exposure

Treatment after exposure can prevent the disease if given within 10 days. The rabies vaccine is 100% effective if given before symptoms of rabies appear. Every year, more than 15 million people get vaccinated after potential exposure. While this works well, the cost is significant. In the US it is recommended people receive one dose of human rabies immunoglobulin (HRIG) and four doses of rabies vaccine over a 14-day period. HRIG is expensive and makes up most of the cost of post-exposure treatment, ranging as high as several thousand dollars. In the UK, one dose of HRIG costs the National Health Service £1,000, although this is not flagged as a "high-cost medication". A full course of vaccine costs £120–180. As much as possible of HRIG should be injected around the bites, with the remainder being given by deep intramuscular injection at a site distant from the vaccination site.

People who have previously been vaccinated against rabies do not need to receive the immunoglobulin—only the postexposure vaccinations on days 0 and 3. The side effects of modern cell-based vaccines are similar to the side effects of flu shots. The old nerve-tissue-based vaccination required multiple injections into the abdomen with a large needle but is inexpensive. It is being phased out and replaced by affordable World Health Organization intradermal-vaccination regimens. In children less than a year old, the lateral thigh is recommended.

Thoroughly washing the wound as soon as possible with soap and water for approximately five minutes is effective in reducing the number of viral particles. Povidone-iodine or alcohol is then recommended to reduce the virus further.

Awakening to find a bat in the room, or finding a bat in the room of a previously unattended child or mentally disabled or intoxicated person, is an indication for post-exposure prophylaxis (PEP). The recommendation for the precautionary use of PEP in bat encounters where no contact is recognized has been questioned in the medical literature, based on a cost–benefit analysis. However, a 2002 study has supported the protocol of precautionary administration of PEP where a child or mentally compromised individual has been alone with a bat, especially in sleep areas, where a bite or exposure may occur with the victim being unaware.

After onset

Once rabies develops, death almost certainly follows. Palliative care in a hospital setting is recommended with administration of large doses of pain medication, and sedatives in preference to physical restraint. Ice fragments can be given by mouth for thirst, but there is no good evidence intravenous hydration is of benefit.

A treatment known as the Milwaukee protocol, which involves putting a person into a chemically induced coma and using antiviral medications, has been proposed. It initially came into use in 2003, following Jeanna Giese, a teenage girl from Wisconsin, becoming the first person known to have survived rabies without preventive treatments before symptom onset. The protocol has been tried multiple times since, but has been assessed as an ineffective treatment, and concerns were raised about the costs and ethics of its use.

Prognosis

Vaccination after exposure, PEP, is highly successful in preventing rabies. In unvaccinated humans, rabies is almost certainly fatal after neurological symptoms have developed.

Epidemiology

Map of rabies-free countries and territories

In 2010, an estimated 26,000 people died from rabies, down from 54,000 in 1990. The majority of the deaths occurred in Asia and Africa. As of 2015, India (approximately 20,847), followed by China (approximately 6,000) and the Democratic Republic of the Congo (5,600), had the most cases. A 2015 collaboration between the World Health Organization, World Organization of Animal Health (OIE), Food and Agriculture Organization of the United Nation (FAO), and Global Alliance for Rabies Control has a goal of eliminating deaths from rabies by 2030.

India

India has the highest rate of human rabies in the world, primarily because of stray dogs, whose number has greatly increased since a 2001 law forbade the killing of dogs. Effective control and treatment of rabies in India is hindered by a form of mass hysteria known as puppy pregnancy syndrome (PPS). Dog bite victims with PPS, male as well as female, become convinced that puppies are growing inside them, and often seek help from faith healers rather than medical services. An estimated 20,000 people die every year from rabies in India, more than a third of the global total.

Australia

Australia has an official rabies-free status, although Australian bat lyssavirus (ABLV), discovered in 1996, is a rabies-causing virus related to the rabies virus prevalent in Australian native bat populations.

United States

Rabies cases in humans and domestic animals – United States, 1938–2018

Canine-specific rabies has been eradicated in the United States, but rabies is common among wild animals, and an average of 100 dogs become infected from other wildlife each year.

Due to high public awareness of the virus, efforts at vaccination of domestic animals and curtailment of feral populations, and availability of postexposure prophylaxis, incidence of rabies in humans is very rare in the United States. From 1960 to 2018, a total of 125 human rabies cases were reported in the United States; 36 (28%) were attributed to dog bites during international travel. Among the 89 infections acquired in the United States, 62 (70%) were attributed to bats. The most recent rabies death in the United States was in November 2021, where a Texas child was bitten by a bat in late August 2021 but his parents failed to get him treatment. He died less than three months later.

Europe

Either no or very few cases of rabies are reported each year in Europe; cases are contracted both during travel and in Europe.

In Switzerland the disease was virtually eliminated after scientists placed chicken heads laced with live attenuated vaccine in the Swiss Alps. Foxes, proven to be the main source of rabies in the country, ate the chicken heads and became immunized.

Italy, after being declared rabies-free from 1997 to 2008, has witnessed a reemergence of the disease in wild animals in the Triveneto regions (Trentino-Alto Adige/Südtirol, Veneto and Friuli-Venezia Giulia), due to the spreading of an epidemic in the Balkans that also affected Austria. An extensive wild animal vaccination campaign eliminated the virus from Italy again, and it regained the rabies-free country status in 2013, the last reported case of rabies being reported in a red fox in early 2011.

The United Kingdom has been free of rabies since the early 20th century except for a rabies-like virus (EBLV-2) in a few Daubenton's bats. There has been one fatal case of EBLV-2 transmission to a human. There have been four deaths from rabies, transmitted abroad by dog bites, since 2000. The last infection in the UK occurred in 1922, and the last death from indigenous rabies was in 1902.

Sweden and mainland Norway have been free of rabies since 1886. Bat rabies antibodies (but not the virus) have been found in bats. On Svalbard, animals can cross the arctic ice from Greenland or Russia.

Mexico

Mexico was certified by the World Health Organization as being free of dog-transmitted rabies in 2019 because no case of dog-human transmission had been recorded in two years.

Asian countries

Despite rabies being preventable and the many successes of the years from countries such as North America, South Korea and Western Europe, Rabies remains endemic in many Southeast Asian countries including Cambodia, Bangladesh, Bhutan, North Korea, India, Indonesia, Myanmar Nepal, Shi Lanka, and Thailand. Half the global rabies deaths occur in southeast Asia- approx. 26,000 per year.

Much of what prevents Asia from implementing the same measures as other countries is cost. Known knowledge suggests treating wild canines is the primary source of resolving rabies, however it costs 10 times more than treating individuals as they come with bites. Rabies research and treatment in general is so expensive that India and other surrounding countries are simply unable to apply many preventative measures due to financial restrictions.

Thailand

In 2013 human rabies was nearly eradicated in the state of Thailand due to new measures put into place requiring the vaccination of all domestic dogs as well as programs seeking to vaccinate wild dogs and large animals. however due to neighboring countries – Cambodia, Laos, and Myanmar – and their inability to financially combat rabies, infected animals continue to pass the border and infect the Thai people leading to ~100 cases a year. These areas around the border are called Rabies Red areas and are where Thailand continuously struggles with eradication and will do so until something is done in the surrounding countries.

Thailand has the resources and medicine necessary to tackle rabies such as implementing regulations that require all children to receive a rabies vaccination before attending schools and having clinics available for those bit or scratched by a possible rabid animal. However, it is up to the individual to take themselves to the clinic, and 10 people per year die due to their own refusal.

Cambodia

Cambodia has about 800 cases of human rabies per year making Cambodia one of the top countries in human rabies incidences. Much of this falls on their lack of animal care, Cambodia has hundreds of thousands of animals infected with rabies, another global high, yet little surveillance of said animals and few laws requiring pets and other household animals to be vaccinated. What's striking about this is Cambodia’s national net worth, they are considered a wealthy nation with the funds capable of combating rabies and vaccinating all consenting citizens. In recent years Cambodia has improved significantly in their human rabies medical practices, with clinics all over the countries being made with treatments and vaccination on hand as well as rabies related education in school classes. However, they are still lacking in terms of animal surveillance and treatment which leads to bleeding into surrounding countries.

History

Rabies has been known since around 2000 BC. The first written record of rabies is in the Mesopotamian Codex of Eshnunna (c. 1930 BC), which dictates that the owner of a dog showing symptoms of rabies should take preventive measures against bites. If another person were bitten by a rabid dog and later died, the owner was heavily fined.

In Ancient Greece, rabies was supposed to be caused by Lyssa, the spirit of mad rage.

Ineffective folk remedies abounded in the medical literature of the ancient world. The physician Scribonius Largus prescribed a poultice of cloth and hyena skin; Antaeus recommended a preparation made from the skull of a hanged man.

Rabies appears to have originated in the Old World, the first epizootic in the New World occurring in Boston in 1768.

Rabies was considered a scourge for its prevalence in the 19th century. In France and Belgium, where Saint Hubert was venerated, the "St Hubert's Key" was heated and applied to cauterize the wound. By an application of magical thinking, dogs were branded with the key in hopes of protecting them from rabies.

It was not uncommon for a person bitten by a dog merely suspected of being rabid to commit suicide or to be killed by others.

In ancient times the attachment of the tongue (the lingual frenulum, a mucous membrane) was cut and removed, as this was where rabies was thought to originate. This practice ceased with the discovery of the actual cause of rabies. Louis Pasteur's 1885 nerve tissue vaccine was successful, and was progressively improved to reduce often severe side-effects.

In modern times, the fear of rabies has not diminished, and the disease and its symptoms, particularly agitation, have served as an inspiration for several works of zombie or similarly themed fiction, often portraying rabies as having mutated into a stronger virus which fills humans with murderous rage or incurable illness, bringing about a devastating, widespread pandemic.

Other animals

Two dogs with the paralytic, or dumb, form of rabies
Rabies is infectious to mammals; three stages of central nervous system infection are recognized. The clinical course is often shorter in animals than in humans, but result in similar symptoms and almost always death. The first stage is a one- to three-day period characterized by behavioral changes and is known as the prodromal stage. The second is the excitative stage, which lasts three to four days. This stage is often known as "furious rabies" for the tendency of the affected animal to be hyper-reactive to external stimuli and bite or attack anything near. In some cases, animals skip the excitative stage and develop paralysis, as in the third phase; the paralytic phase. This stage develops due to damage to motor neurons. Incoordination is seen, owing to rear limb paralysis, and drooling and difficulty swallowing is caused by paralysis of facial and throat muscles. Death is usually caused by respiratory arrest.

Man-eater

From Wikipedia, the free encyclopedia

A man-eater is an individual animal or being that preys on humans as a pattern of hunting behavior. This does not include the scavenging of corpses, a single attack born of opportunity or desperate hunger, or the incidental eating of a human that the animal has killed in self-defense. However, all three cases (especially the last two) may habituate an animal to eating human flesh or to attacking humans, and may foster the development of man-eating behavior.

Although humans can be attacked by many kinds of non-human animals, man-eaters are those that have incorporated human flesh into their usual diet and actively hunt and kill humans. Most reported cases of man-eaters have involved lions, tigers, leopards, polar bears, and large crocodilians. However, they are not the only predators that will attack humans if given the chance; a wide variety of species have also been known to adopt humans as usual prey, including various bears, spotted and striped hyenas, and Komodo dragons.

Felids

Tigers

The man-eater of Segur, a young man-eating male Bengal tiger who killed 5 people in the Nilgiri Hills of Tamil Nadu state in South India.

Tigers are recorded to have killed more people than any other big cat, and have been responsible for more human deaths through direct attack than any other wild mammal. About 1,000 people were reportedly killed each year in India during the early 1900s, with one individual Bengal tigress killing 436 people in India. Tigers killed 129 people in the Sundarbans mangrove forest from 1969 to 1971. Unlike leopards and lions, man-eating tigers rarely enter human habitations to acquire prey. The majority of victims were reportedly in the tiger's territory when the attack took place. Additionally, tiger attacks mostly occur during daylight hours, unlike those involving leopards and lions. The Sundarbans is home to approximately 600 royal Bengal tigers who before modern times used to "regularly kill 50 or 60 people a year". In 2008, a loss of habitat due to the Cyclone Sidr led to an increase in the number of attacks on humans in the Indian side of the Sundarbans, as tigers were crossing over to the Indian side from Bangladesh.

A theory promoted to explain this increase in attacks suggests that, since tigers drink fresh water, the salinity of the area waters serve as a destabilizing factor in the diet and life of tigers of Sundarbans, keeping them in constant discomfort and making them extremely aggressive. Other theories include the sharing of their habitat with humans and the consumption of human corpses during floods.

Lions

The Tsavo maneaters on display in the Field Museum of Natural History in Chicago.

Man-eating lions have been recorded to actively enter human villages at night as well as during the day to acquire prey. This greater assertiveness usually makes man-eating lions easier to dispatch than tigers. Lions typically become man-eaters for the same reasons as tigers: starvation, old age, and illness, though as with tigers, some man-eaters were reportedly in perfect health.

The most notorious case of man-eating lions ever documented happened in 1898 in what was then known as British East Africa, now Kenya. During the construction of a rail bridge over the Tsavo River (part of the Uganda Railway) in modern-day Tsavo East National Park, two enormous maneless male Tsavo lions terrorized the railway workers, most of them imported from India, and were believed to have killed or devoured over 130 men. The entire railway project had to be halted as the then British prime minister sounded the alarm. They were eventually tracked and killed by the project's chief engineer and required eight men to carry each to camp.

Man-eating lions studies indicate that African lions eat humans as a supplement to other food, not as a last resort. In July 2018, a South African news website reported that three rhino poachers were mauled and eaten by lions at Sibuya Game Reserve in Eastern Cape province, South Africa.

Leopards

Man-eating leopards are a small percentage of all leopards, but have undeniably been a menace in some areas; one leopard in India killed over 200 people. Jim Corbett was noted to have stated that unlike tigers, which usually became man-eaters because of infirmity, leopards more commonly did so after scavenging on human corpses. In the area that Corbett knew well, dead people are usually cremated completely, but when there is a bad disease epidemic, the death rate outruns the supply of cremation pyre wood and people burn the body a little and throw it over the edge of the burning ghat. In Asia, man-eating leopards usually attack at night, and have been reported to break down doors and thatched roofs in order to reach human prey. Attacks in Africa are reported less often, though there have been occasions where attacks occurred in daylight. Both Corbett and Kenneth Anderson have written that hunting the man-eating panther presented more challenges than any other animal. In 2019 in India, an infant was stolen and decapitated by a leopard.

Jaguars

Jaguar attacks on humans are rare nowadays. In the past, they were more frequent, at least after the arrival of Conquistadors in the Americas. The risk to humans would likely increase if the number of capybaras, the jaguar's primary prey, decreased.

Cougars

Due to the expanding human population, cougar ranges increasingly overlap with areas inhabited by humans. Attacks on humans are very rare, as cougar prey recognition is a learned behavior and they do not generally recognize humans as prey. Attacks on people, livestock, and pets may occur when a puma habituates to humans or is in a condition of severe starvation. Attacks are most frequent during late spring and summer, when juvenile cougars leave their mothers and search for new territory. Unlike other big cat man-eaters, cougars do not kill humans as a result of old age or food preference, but in defense of their territory. Such behavior has been documented in hunts by humans, where the cougar is flushed out by dogs which it either outruns or mauls some distance away. Then, the cougar circles around and mauls the hunter in ambush attack.

Canids

Wolves

Two of the Wolves of Périgord, responsible for the deaths of 18 people in February 1766, on display at the chateau of Razac in Thiviers

Contrasted to other carnivorous mammals known to attack humans for food, the frequency with which wolves have been recorded to kill people is rather low, indicating that, though potentially dangerous, wolves are among the least threatening for their size and predatory potential, except for the dog which poses lethal hazards for reasons other than predation. In the rare cases in which man-eating wolf attacks occur, the majority of victims are children. Habituation is a known factor contributing to some man-eating wolf attacks which results from living close to human habitations, causing wolves to lose their fear of humans and consequently approach too closely, much like urban coyotes. Habituation can also happen when people intentionally encourage wolves to approach them, usually by offering them food, or unintentionally, when people do not sufficiently intimidate them. This is corroborated by accounts demonstrating that wolves in protected areas are more likely to show boldness toward humans than ones in areas where they are actively hunted.

Dingoes

Attacks on humans by dingoes are rare, with only two recorded fatalities in Australia. Dingoes are normally shy of humans and avoid encounters with them. The most famous record of a dingo attack was the 1980 disappearance of nine-week-old Azaria Chamberlain. Her parents reported that they both saw a dingo taking Azaria out of their tent when she and her family were out on a camping trip to Uluru. In 2019, a father saved his 14-month-old child from a dingo which had dragged it away.

Domestic dogs

Although dogs have many of the characteristics of bears and big cats, they are unlikely to act as man-eaters themselves. More often humans can be bitten to death by packs of stray dogs, but not eaten. Such attacks often occur in the countries of Eastern Europe, ex-USSR countries, and some South Asian countries, such as India.

Coyotes

Almost all known predatory coyote attacks on humans have failed. To date, other than the Kelly Keen coyote attack and the Taylor Mitchell coyote attack, all known victims have survived by fighting, fleeing, or being rescued, and only in the latter case was the victim partially eaten, although that case occurred in Nova Scotia where the local animals are eastern coyotes (coywolves).

Jackals

In June 2019, a nine-year-old boy was killed by jackals in Farakka, West Bengal, India. This was witnessed by a neighbor, who saw the child's half-eaten body being dragged by the pack of seven jackals.

Bears

Polar bears

Polar bears, particularly young and undernourished ones, will hunt people for food. Although bears rarely attack humans, bear attacks often cause devastating injuries due to the size and immense strength of the giant land and shoreline carnivores. As with dogs, predatory intent is not necessary; territorial disputes and protection of cubs can result in death by bear attack. Truly man-eating bear attacks are uncommon, but are known to occur when the animals are diseased or natural prey is scarce, often leading them to attack and eat anything they are able to kill.

Brown bears

Brown bears are known to sometimes hunt hikers and campers for food in North America. For example, Lance Crosby, 63, of Billings, Montana, was hiking alone and without bear spray in Yellowstone National Park in August 2015 when he was attacked by a 259-pound (117 kg) grizzly bear. The park rules say people should hike in groups and always carry bear spray – a form of pepper spray that is used to deter aggressive bears. His body was found in the Lake Village section of the park in northwest Wyoming. Timothy Treadwell and his girlfriend Amie Huguenard were killed and almost fully eaten by a 28-year-old brown bear on October 5, 2003. The bear's stomach was later found to contain human remains and clothing. In July 2008, dozens of starving brown bears killed two geologists working at a salmon hatchery in Kamchatka. After the partially eaten remains of the two workers were discovered, authorities responded by dispatching hunters to cull or disperse the bears.

American black bears

While American black bears rarely attack people, lone, predatory black bears are responsible for most fatal black bear attacks on humans in the United States and Canada, according to a study from 2011. Unlike female bears, motivated to attack humans to protect cubs, male black bears may display predatory behavior toward humans and view them as a potential food source. The same study cautioned that the chances of a black bear attacking a human were small, writing, "Each year, millions of interactions between people and black bears occur without any injury to a person, although by 2 years of age most black bears have the physical capacity to kill a person."

Other bear species

Though usually shy and cautious animals, Asian black bears are more aggressive toward humans than the brown bears of Eurasia. In some areas of India and Burma, sloth bears are more feared than tigers, due to their unpredictable temperament.

Other mammals

Hyenas

Although hyenas readily feed upon human corpses, they are generally very wary of humans and less dangerous than the big cats whose territory overlaps with theirs. Nonetheless, both the spotted hyena and the smaller striped hyena are powerful predators quite capable of killing an adult human, and are known to attack people when food is scarce. Like most predators, hyena attacks tend to target women, children, and infirm men, though both species can and do attack healthy adult males on occasion. The spotted hyena is the more dangerous of the two species, being larger, more predatory, and more aggressive than the striped hyena. The brown hyena and aardwolf are not known to prey on humans.

Pigs

Pigs are competent predators and can kill and eat helpless humans unable to escape them. Numerous animal trials in the Middle Ages involved pigs accused of eating children. In 2019, a woman was attacked and killed by a herd of feral hogs in rural Texas. She died due to exsanguination (i.e. bled to death) from bite wounds.

Wild pigs are opportunistic omnivores that can function as aggressive predators. Being scavengers, wild pigs have been specifically documented to feed on human corpses or remains in post-combat, rural accident (e.g., plane crash) and crime (e.g., homicide) situations. In addition, there is at least one instance on record of a wild pig in southern France that became a confirmed repeated man-eater. In four of the attacks reviewed in a study, the wild pig either partially or mostly consumed the remains of the human victim that had been fatally injured by that animal in the attack. Three of the four attacks were explicitly characterized by the investigating authorities as being predatory. In two additional attacks, the pig's motivation was also described by either the victim or the victim's companion as predatory; of those, one victim survived with serious injuries while the other was fatally injured. In a 2009 attack in India, a 3-year old girl, walking on a trail with her father, was grabbed by a wild pig, which then tried to flee with the child in its mouth. The father chased the animal, fighting with it until his daughter was released. Both the father and daughter were seriously injured during the attack; the child later died of her injuries. Although attacks by wild pigs are primarily defensive in nature, the potential for an attack of a predatory nature cannot be completely discounted.

Primates

The only documented man-eaters among the great apes are humans themselves and chimpanzees. As humans encroach further on chimpanzee habitat, the occurrence of chimpanzees killing human children has allegedly become more common.

Rats

Despite small individual size, rats in large numbers can kill helpless people by eating them alive.

Rat torture has been documented by Amnesty International. Large sized rats (some as big as a small cat) have been seen to feed upon human corpses in mortuaries in India.

Reptiles

The Nile crocodile is one of the species involved in the most unprovoked fatal attacks on humans.

Crocodiles

Crocodile attacks on people are common in places where crocodiles are native. The saltwater and Nile crocodiles are responsible for more attacks and more deaths than any other wild predator that attacks humans for food. Each year, hundreds of deadly attacks are attributed to the Nile crocodile within sub-Saharan Africa. Because many relatively healthy populations of Nile crocodiles occur in East Africa, their proximity to people living in poverty and/or without infrastructure has made it likely that the Nile crocodile is responsible for more attacks on humans than all other species combined. One notorious man-eating crocodilian was Gustave. In Australia, crocodiles have also been responsible for several deaths in the tropical north of the country. The mugger crocodile is another man-eater that kills many people in Asia each year, although not to the same level as the saltwater and Nile crocodiles. All crocodile species are also dangerous to humans, but most do not actively prey on them.

Alligators

Despite their manifest ability to kill prey similar to or larger than humans in size and their commonness in an area of dense human settlement (the southeastern United States, especially Florida), American alligators rarely prey upon humans. Even so, there have been several notable instances of alligators opportunistically attacking humans, especially the careless, small children, and elderly. Unlike the far more dangerous saltwater and Nile crocodiles, the majority of alligators avoid contact with humans if possible, especially if they have been hunted. Incidents have happened, and they may not all have been predatory in nature.

Snakes

Only very few species of snakes are physically capable of swallowing an adult human. Although quite a few claims have been made about giant snakes swallowing adult humans, only a limited number have been confirmed. Various species of pythons are the most commonly recorded perpetrators. In 2017 in Indonesia, an adult male was discovered inside a 7-metre-long (23 ft) python. On 14 June 2018 a 54-year-old woman named Wa Tiba was eaten by a reticulated python, which had slithered into her garden at her home. A 45-year-old woman farmer in Indonesia, who had been missing since the day before, was found dead inside a 5-metre-long (16 ft) python in June 2024.

Large constricting snakes will sometimes constrict and kill prey that are too large to swallow. Also, multiple cases are documented of medium-sized (3 to 4 m [10 to 13 ft]) captive Burmese pythons constricting and killing humans, including several nonintoxicated, healthy adult men, one of whom was a "student" zookeeper. In the zookeeper case, the python was attempting to swallow the zookeeper's head when other keepers intervened. In addition, at least one Burmese python as small as 2.7 m (8.9 ft) constricted and killed an intoxicated adult man.

A large constricting snake may constrict or swallow an infant or a small child, a threat that is legitimate and empirically proven. Cases of python attacks on children have been recorded for the green anaconda, the African rock python, and the Burmese python.

In the Philippines, more than a quarter of Aeta men (a modern forest-dwelling hunter-gatherer group) have reported surviving reticulated python predation attempts. Pythons are nonvenomous ambush predators, and both the Aeta and pythons hunt deer, wild pigs, and monkeys, making them competitors and prey.

In South Africa in 2002, a 10-year-old boy was swallowed whole by a 6-metre-long (20 ft) African rock python, but cases like these are empirically observed and recorded but not entirely confirmed unlike the cases mentioned above.

In Australia there has been one recorded case of an amethystine python attempting to consume an adult human.

Lizards

Large Komodo dragons are the only known lizard species to occasionally attack and consume humans. Because they live on remote islands, attacks are infrequent and may go unreported. Despite their large size, attacks on people are often unsuccessful and the victims manage to escape with their lives, albeit severely wounded.

Birds

Some evidence supports the contention that the African crowned eagle occasionally views human children as prey, with a witness account of one attack (in which the victim, a seven-year-old boy, survived and the eagle was killed), and the discovery of part of a human child skull in a nest. This would make it the only living bird known to prey on humans, although other birds such as ostriches and cassowaries have killed humans in self-defense and a lammergeier might have killed the ancient Greek playwright Aeschylus by accident. Various large raptors like golden eagles are reported attacking humans, but it is unclear if they intend to eat them or if they have ever been successful in killing one.

A series of incidents in which a martial eagle attacked and killed one human child as well as injuring two others was recorded in Ethiopia in 2019.

Some fossil evidence indicates large birds of prey occasionally preyed on prehistoric hominids. The Taung Child, an Australopithecus africanus found in Africa, is believed to have been killed by an eagle-like bird similar to the crowned eagle. The extinct Haast's eagle may have preyed on humans in New Zealand, and this conclusion would be consistent with Maori folklore. Leptoptilos robustus might have preyed on both Homo floresiensis and anatomically modern humans, and the Malagasy crowned eagle, teratorns, Woodward's eagle and Caracara major are similar in size to the Haast's eagle, implying that they similarly could pose a threat to a human being.

Fish

Sharks

Sign warning swimmers of the danger of shark attacks

Contrary to popular belief, only a limited number of shark species are known to pose a serious threat to humans. The species that are most dangerous can be indiscriminate and will take any potential meal they happen to come across (as an oceanic whitetip might eat a person floating in the water after a shipwreck), or may bite out of curiosity or mistaken identity (as with a great white shark attacking a human on a surfboard possibly because it resembles its favoured prey, a seal).

Of more than 568 shark species, only four have been involved in a significant number of fatal unprovoked attacks on humans: the great white shark, tiger shark, bull shark, and the oceanic whitetip shark. These sharks, being large, powerful predators, may sometimes attack and kill humans; it is worth noting that they have all been filmed in open water by unprotected divers. One of the most notorious and well known incidents of shark predation came with the sinking of the USS Indianapolis (CA-35), where sharks believed to be oceanic whitetips fed on an estimated 150 of the survivors who were stranded for days.

More recently, on 8 June 2023, due to the popularity of social media the fatal tiger shark attack on Vladmir Popov off the coast of Hurghada, Egypt, in the Red Sea has also gained significant notoriety as almost the entire attack was caught on film before going viral.

Piranhas

Attacks by piranhas resulting in deaths have occurred in the Amazon basin. In 2011, a drunk 18-year-old boy was attacked and killed in Rosario del Yata, Bolivia. In 2012, a five-year-old Brazilian girl was attacked and killed by a shoal of P. nattereri. Some Brazilian rivers have warning signs about lethal piranhas.

Catfish

Reports have been made of goonch catfish eating humans in the Kali River in India. Additionally there have been reports of Wels catfish killing and eating humans in Europe. Large predatory catfish such as the redtail catfish and piraíba are thought to have contributed to the loss of life when the Sobral Santos II ferry sank in the Amazon River in 1981.

Groupers

The giant grouper is one of the largest species of bony fish in the world, reaching a maximum length of 3 meters (10 ft) and weight of 600 kilograms (1,300 lb). There have been cases of this species attacking humans, along with the closely related Atlantic goliath grouper.

Invertebrates

Cephalopods

Some large cephalopods, in particular the Humboldt squid, are said to attack and eat humans.

Lie group

From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Lie_group In mathematics , a Lie gro...