Rabies is a viral zoonotic disease or pathogens that is transmitted between domestic animals, wild carnivores and bats all over the world. Raccoons, skunks, foxes and coyotes are some of the most common wild reservoirs of rabies in the United States. Domestic animals such as cats, dogs and cattle too can get rabies. Raccoons are considered one of the most primary carriers of rabies in the US.
Terrestrial rabies is mostly associated with carnivores such as foxes, jackals, raccoons and mongooses. Rabies generally occurs in non-carnivores species as a spill-over from carnivores. Carnivores are well-suited as the maintenance host. The rabies virus present in the saliva of infected animals especially during the acute neurological stage of the disease is predominantly transmitted to non-carnivores mammals through bite wounds.
The first instance occurred in England in 1885 in roe deer (Capreolus). Common symptoms of rabies were observed including extreme aggressiveness, paralysis and syncope.
Rabies in Raccoons:
Most of the people are aware of the fact that raccoons are nocturnal animals. They are usually active during nighttime. So if a raccoon comes out during broad day-light instead of night, we have to assume that something is erroneous. At the same we cannot assure that it is an indicator of rabies. Although raccoons are primarily nocturnal, they are active in the middle of the day in search of food and water. This is especially true in the case of nursing female raccoons. For extra nutritional requirements, they need to gather extra food during the daytime in order to produce more milk.
Raccoons usually contract rabies when they bite or are bitten by another creature afflicted with the disease. When exposed to virus, they may show no indication of rabies during the initial stages. After two months or longer, these rabid raccoons gets affected by lethargy and exhibit various symptoms and a variety of unusual behaviors such as :
- Choking, drooling and frothing of the mouth due to throat muscle constriction
- Fur on their face appears to be wet and tangled
- Difficulty in walking with fully or partially paralyzed hind legs
- Lurching in an unnatural fashion or walking in circles.
- Making crazy noises
If a person stumble across a raccoon out in the daylight:
- Leave it alone and don't try to approach or feed them.
- Must be very alert when the raccoon lingering in the yard appears to be very friendly, acting unstable or walking in odd patterns. One must immediately report it to the concerned local animal control agency. Upon arrival, they will shoot the rabid raccoon if necessary.
Rabies in Bats:
Bats are warm-blooded animals that can contract and carry rabies. There are some bats in Europe that transmit rabies virus to humans which is known as the European Bat Lyssavirus (EBLV) type 1.
EBLV Type 1:
The Serotine bats (Eptesicus serotinus) most commonly found in European nations like UK, Spain and Germany is considered to be the main reservoir for European Bat Lyssavirus Type 1. It accounts for the vast majority of bat rabies cases in Europe. In order to determine the dissemination and probable means of transmission, twenty nine wild bats were caught and divided into four groups for inoculation and to detect the various potential routes of infection. They are:
- Subcutaneous injection and
The results revealed that mortality rate was higher in Intracranial infected animals followed by Subcutaneous and Intramuscular groups whereas rabies did not develop in Intranasal groups.
- Keep bats away from your house or living space.
- Do not handle bats if you find one lying on the ground. Just leave it alone undisturbed.
- Keep your pets away from the bats.
- Permanently seal any gaps or holes that prevent the bats from entering into your living quarters.
- Prevent bats from roosting in attics or buildings by covering outside entry points.
- Block the area where the bats exit at dusk by hanging clear plastic sheeting or bird netting.
Bats are not asymptomatic carriers of the disease. They are not very aggressive and usually stay away or avoid contact with humans. But if you are bitten by a bat follow the below steps:
- Wash the wound thoroughly using soap and water for a minimum of ten minutes and cleanse the bite site with an alcohol base or other disinfectant.
- Seek medical help and get vaccinated immediately.
- If possible, catch the bat safely using either heavy leather gloves, shovel or a net and put it in a tight container covered with a lid. Send it to the health department where they conduct the necessary test and verify whether the bat is virus infected.
- When an individual is exposed to rabies virus, a post exposure set of five shots is mandatory. The physician administers your upper arm after the shots are taken.
Pseudo rabies also known as Aujezsky's disease is a viral disease in swine caused by herpes virus that is endemic in many parts of the world. Incubation period for infection in pseudo rabies is comparatively much shorter than that found in rabies. The incubation period for pseudo rabies in rabbits is roughly 2-3 days with death occurring within 24 hours after the onset of symptoms. An experiment conducted by Adami in 1889, a rabbit was inoculated with brain material from infected deer. The rabbit died approximately 16-17 days after inoculation. He performed another experiment where a healthy deer was placed in a room with another infected deer. From his observations, he concluded that the mode of transmission was through infected saliva via biting. This was ascertained by the extreme aggressive behavior of the deer as well as several attempts made by the deer to bite a person within reach. It took 19 days for the healthy deer to show symptoms of infection.
Although the unusual occurrence of rabies was first observed in the greater Kudu antelope in 1975 near Windhoek, Namibia, an epizootic of rabies in Kudu antelope began in Okahandja district in 1977. In the same year the rabies was confirmed in two kudu antelopes at the Etosha National Park. The number of confirmed cases escalated throughout 1978-1979 spreading westwards along the Swakop river. During 1983-1984, the first case of lions contracting the disease was reported from the Etosha National Park. It is supposed that lions became infected from hunting rabid kudu since the report of rabid lions were from an area of high Kudu population density in eastern Kudu.
Factors responsible for transmission of rabies in Kudu:
Transmission of rabies among Kudu is believed to occur due to several factors such as environmental and behavioral. During the first epizootic, unusual heavy rainfall which occurred in 1977 and in 1973, the rainfall was above average but it doubled in 1975 and 1976. Due to the bush encroachment of thorny bushes into grassland areas, there was abundant supply of water and food sources. An estimated kudu numbers rose from 80,000 in 1972 to 2,00,000 in 1978. The protection and breeding for trophy hunting, tourism and reduction in number of predators due to farmers safeguarding their stock contribute to increase in kudu population.
This outbreak of rabies amongst kudus may arise owing to non-bite, horizontal transmission of rabies. The estimated loss of kudu during the first epizootic in 1977, it is unlikely that each kudu was attacked and infected separately by a carnivore such as jackal, dog, suricate, mongoose or wild cat.