Page 78 - January 2016 Speedhorse

If an unvaccinated horse is known to have been bitten by a rabid animal, and the offending animal was tested, it is possible to treat that horse like we treat humans and not have to euthanize it, but check your state’s guidelines to determine what you can do with the horse.
TREATMENT
If an unvaccinated horse is known to have been bitten by a rabid animal such as a cat, skunk, or raccoon (with the offending animal killed and tested), it is possible to treat that horse like we treat humans and not have to euthanize it. “This is something that was looked at in Texas. The laws regarding unvac- cinated, exposed animals vary from state to state. You can check your state’s public health guidelines to determine what you can do with that horse,” she says.
Texas developed what they call a post- exposure rabies prophylaxis protocol. “A study was published in 2010 in a medical journal looking at a time period from 2000 to 2009, using 72 horses. They do this post- exposure type of treatment in many different species of animals, especially pets, but in this study they also mentioned 72 horses that
had received this prophylaxis and none of them got rabies. It was the same for the dogs and cats that were treated,” she says. Thus, an animal that is started on this protocol immediately after being bitten could be quarantined and watched rather than having to euthanize it.
“The animal must be immediately vac- cinated, isolated for 90 days and boostered with the vaccine again at the third and eighth week during that isolation period. Thus, it receives
a series of three vaccinations. The study specifically looked at previously unvaccinated animals,” says Johnson.
Rabies variants vary geographically. This map shows the major rabies distribution of rabies by source in the U.S.
The time from exposure to the onset of rabies symptoms varies greatly, depending on the location of the bite. The farther the virus has to travel along the nerves to the brain, the longer the onset of symptoms will be. In some cases, the initial bite may be healed and you may be unable to locate the bite. Signs can include attitude change, depression, weakness and incoordination, mild lameness, mild muscle contractions in the upper neck and face, inability to swallow, drooling, and a tendency toward aggression and irritability.
Rabies Variants
Rabies, just like influenza, has different variants or genetically different strains. There are numerous variants of the rabies virus, and each of these is adapted to a particular species of ani- mal. This adaptation makes that species a reservoir for that variant. The host species is not killed as quickly as is a species into which that variant spills over. Thus, a skunk with skunk rabies lives longer (to infect more animals) than would some other type of animal bitten by a skunk.
• This enables the variant to survive and be propagated in nature. There are several rabies variants in skunks, including the North Central Skunk, South Central Skunk, and Spotted Skunk, and even more variants in bats.
• The variants were named for the species, and sometimes the region, in which they were first detected. Many distinct rabies virus variants have been identified in different bat species (Mexican Free-tail, Cave Myotis, Silver-haired bat, etc.). As of 2005, researchers think there are between 15 and 40 species of bats that may each have their own rabies variant.
• Examples of rabies variants in the U.S. include raccoon, skunk, fox, and mongoose (in Puerto Rico). Several fox variants exist in the U.S., including the Texas Gray Fox, Arizona Fox, Arctic Fox, Red Fox, etc., while different canine variants are the predominant form of rabies in other countries.
• Genetically different rabies virus variants have also been identified in geographically separate populations of animals of the same species, such as gray foxes in Arizona and Texas (or skunks in California, south central U.S. and north central U.S.). A new rabies virus vari- ant associated with Mexican free-tail bats was identified in the U.S. in 2008 after the death of a Mexican immigrant who was exposed to bats prior to her arrival in the U.S.
76 SPEEDHORSE, January 2016
EQUINE HEALTH