RABIES IN LIVESTOCK IN INDIA
Rabies is endemic in India ,both in humans and animal, get from being bitten by an animal infected with the rabies virus and always deadly in humans and animal but can be totally prevented by appropriate management of bite, recognize the exposure and promptly get appropriate medical care before developing the symptoms of rabies. Rabies is a zoonotic disease caused by RNA viruses in the family Rhabdoviridae, Genus Lyssavirus. Virus is typically present in the saliva of clinically ill mammals and is transmitted through a bite. After entering the central nervous system of the next host, the virus causes an acute, progressive encephalomyelitis that is almost always fatal. About 65,000 people have been reported to be died due to rabies each year across the world .Dogs are the main reservoir of the virus and are responsible for spillover infections in humans and animal. Any warm blooded animal can get rabies. Cattle, goat, horse, domestic cats and humans often found infected with rabies in India.Rabies can also infect coyotes, wolves, ferrets skunks and foxes. The most important conditions for the successful spread of rabies virus prevail inIndia; a large population of stray dogs, which potentially interact with the population and with other species of animals. Although rabies occurs throughout the year in all parts of India , the mortality rate in livestock is unknown and large number of rabies cases remain unrecorded. Scattered reports from various sources indicate, however, that about over 15,0000 animals are vaccinated every year with pre-exposure and post-exposure vaccines produced locally and imported from other countries .With political will and solid global epidemiologic information, rabies elimination is possible. Molecular typing of circulating rabies viruses is necessary to identify and develop effective control measures, and to understand the spread of certain rabies virus variants and their incursion into new regions .If animal bites are managed appropriately and timely the rabies can be prevented to a large extent. In this regard the post exposure treatment and management of animal bite cases is of prime importance. Most people’s connotation of rabies is a snarling mad dog, foaming at the mouth. But livestock are also susceptible, and the symptoms easily can be mistaken for some other problem. Unfortunately, the result is often human exposure when the owner or veterinarian tries to examine or treat the animal.
Rabies can occur in all warm-blooded animals and is always fatal. Caused by a virus that affects the nervous system, it’s transmitted by saliva of an infected animal – usually via a bite, by saliva coming in contact with mucous membranes (eyes, nose or mouth) or an opening in the skin.
Characteristics———
The rabies virus (Family Rhabdoviridae, genus Lyssavirus) is fragile and easily inactivated by desiccation, ultra-violet radiation, and detergents. It is rapidly destroyed by temperatures above 50 Centigrade (122º F) and destroyed within a few hours at room temperature. However, the rabies virus may persist for years when frozen.
Transmission-———–
Rabies may be transmitted when infected saliva, central nervous system tissue, or cerebral spinal fluid penetrates the skin or mucosa of a susceptible mammal. Rabies is usually transmitted by bite wounds, but may involve saliva contact with mucous membranes or a fresh break in the skin. Rabies is not transmitted by contact with blood, urine, feces, petting or touching fur, or being sprayed by a skunk. Infection usually occurs when infectious saliva comes into contact with fresh wounds (e.g. bites and scratches) and unprotected mucous membranes (e.g. eyes and mouth) of non-vaccinated animals and people. Most (95%) of human cases of rabies are due to bites by infected dogs.
Pathogenesis ———–
There is still much to be learned about the pathogenesis of rabies in mammals, particularly with respect to species variations during the incubation period, the natural cycles in wildlife, and salivary shedding (infectious) periods. After inoculation, the rabies virus progresses from the subcutaneous tissue or muscle into peripheral nerves. The virus then migrates along nerves to the spinal cord and brain. The victim exhibits behavioral changes and clinical signs when the virus reaches the brain. At this point the incubation period is over and the clinical period begins. The virus continues to spread in the infected host, via the nerves, to the salivary glands and in the final phase, rabies may be transmitted to other mammals through infectious saliva. The infected animal usually dies within a few days after onset of clinical signs. Factors that may contribute to the transmission, incubation period and development or prevention of rabies infection include: the amount of viral inoculum (amount of rabies virus introduced into the body); the anatomic location of the bite or saliva exposure; and post-exposure wound management (washing the wound, rabies immune globulin and vaccination). Head and neck wounds as well as wounds in highly innervated areas such as fingers generally have shorter incubation periods due to the proximity of the viral inoculation to nerve tissue
Incubation Period and Duration of Disease in Dogs and Cats & Cattle
• Incubation Period – Average 2-9 weeks; range 9 days – 8.5 months (not >6 months in U.S.)
• Prodromal/Initial stage – 1-3 days
• Excitation (furious) stage – average 1-7 days. Some animals do not exhibit this stage.
• Paralytic stage – 1-4 days duration
*If a dog or cat has not shown any signs of abnormality on the tenth day after inflicting a bite, it is safe to assume that the animal was not shedding virus in its saliva at the time of the bite. Table 2.
Incubation Period and Duration of Disease in Other Species
Incubation period Duration of clinical disease Horses/mules Average 3-14 weeks, range
Prevention
Prevention of human and pet rabies depends on the following:
• Vaccinating dogs, cats, horses and ferrets, control of stray pets, and leash law enforcement. • Promoting educational messages to the public to reduce exposures to wild and stray animals. • Providing exposed persons with prompt wound care and appropriate post-exposure prophylaxis.
CLINICAL SIGNS OF RABIES IN ANIMALS
The rabies virus is a lyssavirus and is highly neurotropic; the virus travels from the peripheral nerves to the spinal cord and into the brain. The incubation period is variable, usually 1-2 months, and depends upon the location of inoculation site. In Kansas rabies is typically transmitted through the bite of an infected skunk; the closer the bite is to the head of the cow the shorter the incubation period. The rabies virus causes encephalitis with rapid progression of the disease over the course of a few days to a week culminating in death. The initial signs are non-specific and can make diagnosing rabies challenging. Clinical signs are variable and can include anorexia, pruritis , ataxia, lameness, tenesmus, hypersalivation, and aggression. Rabid cattle may appear to be choking which prompts owners, and veterinarians, to insert a hand into the mouth in an attempt to remove a foreign body. Distinct vocalization, bellowing, that some veterinarians say is specific to rabies is a common sign. Rabies should be on the differential diagnosis list for cattle that exhibit abnormal behavior, inability to swallow or choke, neurological abnormalities, and lameness.
Signs of illness in animals can develop anywhere between 10 days and several months to years after infection. Once signs of illness arise, death typically occurs within 10 days. The clinical signs of rabies are variable, depending on the effect on the brain. Rabies often causes sudden behavioural changes, followed by progressive paralysis, coma and death. Behavioural changes include the following:
• Dogs and cats behavioural changes range from a depressed/quiet form, where the animal remains quiet, and only bites when provoked, or a furious form with unusual restlessness, snapping at imaginary objects and eating strange objects such as sticks and stones.
Cattle become depressed, stop producing milk, may grind their teeth, salivate, bellow, have increased sexual activity and may even attack other animals. Paralysis increases, the animal loses balance, finally cannot rise, becomes comatose and dies. In the absence of anti-viral rabies drugs, progress to death is rapid once clinical signs appear. Milk production and feed intake may drop gradually before rapidly falling and cows may look very alert, staring at objects.
Aggressive, excitable or exaggerated movements can be signs of rabies. Sexual activity can be increased, including mounting behaviour. Bulls can have persistent erections or a prolapsed penis.
Other Signs Include
• Inapettence (Lack of appetite)
• Dyspahgia (difficulties swallowing)
• Altered Vocalisation
• Seizures
• Incoordination of hindquarters – Unsteady gait
• Sheep often have multiple cases existing at the same time in a flock, suggesting a rabid animal attack. Sheep appear restless then depressed, dying within about three days.
• Pigs show abnormal behaviour, such as hiding and then biting if provoked, crazed appetite, killing of piglets, increasing dullness, paralysis.
• Horses behavioural changes range from the quiet form where there is depression and difficulty swallowing (owners may think the animal has something caught in its throat) or the furious form where there is marked excitation and it is dangerous to get close to the animal.
Signs of rabies in individual animals, even of the same species, can vary widely. They can be either subtle or obvious and occasionally an animal will die suddenly after exhibiting few or no symptoms. Signs of rabies include: • Initial- lethargy, fever, vomiting, anorexia • Progressive- cerebral dysfunction (including ataxia, difficulty walking, tremors, disorientation, seizures), weakness, paralysis, difficulty breathing or swallowing, excessive salivation, aggression, self-mutilation, abnormal behavior and vocalization. • Death usually occurs from three to seven days after onset. Livestock with behavioral/ neurologic abnormalities that are not explained by an identified disease should be considered for rabies testing, especially if human or animal exposure has occurred. Livestock maintained on rural pastures or grazing land may contract rabies from exposure to wild animals. A 14-day quarantine/observation period is required when livestock bite or expose a person. If clinical signs develop or the animal dies during the 14-day quarantine/observation period, the animal should be euthanized and submitted for rabies testing.
Other Diseases or Conditions Which May Resemble Rabies —————
Many diseases and conditions occur in both wild and domesticated species that may mimic rabies. Some of the more common diseases/conditions in domestic animals can be found in Table 3. Table 3. Differential diagnoses for rabies in domestic animals Ferret Canine/Feline Bovine/Equine Distemper Distemper Toxicoses Insulinoma Encephalitides (Viral, Bacterial, Protozoal/Parasitic) Encephalitides (Viral, Bacterial, Protozoal/Parasitic) Neuropathy- Vestibular Syndrome Herpes Virus Head/Spinal Cord Trauma Tetanus Brain Tumor Brain Abscess Listeriosis Localized Lesions/Obstruction
Symptoms of Rabies in Cattle————-
Cattle infected with rabies may show a variety of symptoms. Initially symptoms may not be obvious, however, the disease will progress quickly. You may see the following in your cattle: Depression Abrupt changes in behavior Lameness or inability to get up Circling and head pressing Recurrent twitching Trouble urinating or pain upon urinating Muscle tremors Extreme sensitivity to touch and sound Ongoing and painful erection without there being a sexual interest Lack of interest in eating Lack of coordination of muscles; seemingly unaware of their limbs and where they are Paralysis Itchiness Aggression Sudden death Once a horse shows symptoms it will typically die within five to seven days. A cattle that is infected with rabies and showing symptoms of the disease may expose other animals as well as humans to the virus.
Treatment of Rabies in cattle———
There is no treatment for rabies; once symptoms occur the disease is fatal. Should your cattle show symptoms of infection, it is very important that you minimize his exposure to humans as well as other animals. While there is no treatment for rabies, vaccinating your cattle and any other animals can provide protection from becoming infected in the first place. Should your animal be bitten or have contact with another animal that you suspect is infected with rabies, it is important to immediately contact your veterinarian. Should you or another person be bitten by an animal, you will want to wash the wound with soap and water and take off any clothes that may have been contaminated. Then, call your doctor and go to the closest emergency room.
Tests
There are no tests available for rabies in live animals. Determination normally requires a post-mortem inspection of the brain.
Control of the disease in animals-———
In countries where rabies is endemic, control relies on vaccination programs and the management of stray animal populations.
Rabies vaccines are available for dogs, cats, horses, cattle, sheep and ferrets that prevent development of rabies disease.
Population management of stray and feral dog and cat populations reduces the pool of animals that may transmit rabies to humans.
Licensed oral vaccines are used for mass immunisation of terrestrial wildlife.
Treatment in people-———————
Immediately flush wounds thoroughly with soap and water, apply a disinfectant, such as one containing iodine, and seek urgent medical advice.
In people, the incubation period is typically 1-3 months but may vary from <1 week to several years. Once symptoms develop there is no cure and death is almost certain. However with timely medical intervention, the disease is easily preventable. For this reason all potential rabies exposures should be treated as a medical urgency.
Post-exposure medical treatment typically involves a course of rabies vaccinations. Rabies vaccines stimulate the body’s immune response, including the production of antibodies against the rabies virus. Rabies immunoglobulin, which contains readymade antibodies, may be given to provide immediate protection until the vaccine has had time to take effect.
Prevention in people————
Rabies infection can be prevented through several simple courses of action:
• seek medical advice about pre-exposure vaccination before travelling to a region with endemic rabies, particularly if contact with wildlife or dogs is likely
• avoid contact with stray or unknown animals when in countries with endemic rabies
• if bitten or scratched by an animal, immediately clean the wound, apply a disinfectant and, if in a country that is not free of rabies, seek urgent medical advice.
Prevent Exposure-—————
The rabies virus is found in saliva and neural tissue (e.g. brain, spinal cord, nerves). Cattle can shed rabies virus in their saliva and can potentially infect other animals and humans. Veterinarians should wear personal protective equipment (PPE) when examining a suspect rabid animal, or when collecting/handling specimens, to prevent exposure to saliva. PPE should include disposable gloves and goggles or mask to prevent contact of mucous membranes or open cuts on skin with saliva or neural tissue. If you are exposed, immediately wash the wound or cut with soap and water. If saliva comes into contact with mucous membranes immediately flush with fresh clean water. Consult your healthcare provider for bite wound management to include; appropriate antimicrobial therapy, a tetanus immunization (if not current), and an evaluation for rabies post-exposure prophylaxis.
Veterinarians and others at frequent risk of rabies exposure, should be vaccinated and have their rabies titer checked every two years; a booster vaccine is recommended if the titer is below 0.1 IU/mL. If you have been previously immunized against rabies, and have been exposed, you will only need two doses of vaccine. For unvaccinated people after exposure, the complete post exposure treatment consists of administration of rabies immunoglobulin at the site of the bite and a series of rabies vaccinations..
TERMINOLOGY RELATED TO RABIES———-
Rabies Exposures: 1) Bite- wound from a tooth that penetrates the skin. 2) Non-bite contact- getting saliva, brain tissue, or cerebral spinal fluid from a potentially rabid animal into an open wound or in the eyes, nose, or mouth.
Incubation Period: Incubation period is the time from exposure to a disease (such as rabies), until the development of clinical signs or symptoms. The incubation period of rabies is longer and more variable among different species and individuals than in other viral diseases. The incubation period in rabies may depend on the virus variant, susceptibility of the exposed species, the location and amount of inoculum, and post exposure management. The incubation period for rabies in domesticated animals is the basis for the 45-day (for vaccinated domestic animals) and 180 day (for unvaccinated animals) quarantine times after a pet or livestock animal has been exposed to a potentially rabid animal
Rabies Virus “Shedding Period” (infectious stage): The rabies viral shedding period is the time that an animal excretes rabies virus in its saliva. During this period, an animal can transmit rabies to another animal. Viral shedding tends to occur only during the late stage of the disease, after rabies has affected the brain (just before death).
Shedding Time and Quarantine/Observation:
The maximum infectious stage of rabies in dogs and cats in the United States is ten days. If a dog or cat remains healthy for 10 days after biting a person, it is safe to assume that rabies was not transmitted. This quarantine/observation period is extended to 14 days for ferrets, and dogs and cats when the bite occurs in a country with endemic canine rabies. Rabies shedding periods in wild animals are not known, and they should be tested for rabies rather than quarantined if they expose a person.
Quarantine:
Confinement of an animal to a limited, enclosed area in order to restrict exposure of that animal to other animals and to humans, and to facilitate observation of the animal for signs of rabies.
Prevention
Education and vaccination of wild animal populations can control rabies transmission. By limiting the number of wild animals carrying the virus and the chance that those animals will come in contact with pasture and farmland, the likelihood of rabies transmission is reduced.
Cautious handling of cattle with undetermined illnesses is recommended, especially if neurological signs have been observed. Examining a cow’s mouth should be done with gloves to avoid exposure of the veterinarian’s or stockman’s hand to saliva.
The Centre for Disease Control and Prevention recommends the following to limit rabies spread;
• Characterize Virus Characterize the virus at the national reference laboratory
• Identify and Control Source Identify and control the source of the virus introduction
• Enhance Surveillance Enhance laboratory-based surveillance in wild and domestic animals
• Increase Vaccination Increase animal rabies vaccination rates
• Restrict Animals Restrict the movement of animals
• Vector Population Evaluate the need for vector population reduction
• Coordinate Response Coordinate a multiagency response
• Provide Outreach Provide public and professional outreach and education
Dr.Devendra Singh Meratia,
Reference:On request.
