Veterinary Viewpoints: Rabies continues to be a threat to pets and livestock
Friday, April 30, 2021
Media Contact: Derinda Blakeney, APR | OSU College of Veterinary Medicine | 405-744-6740 | email@example.com
A colleague of mine says every skunk she’s submitted for testing has come back positive for rabies.
Livestock producers and their families, who routinely interact with wild and domestic animals, are at particular risk. It is important to know some basic information about rabies in animals to protect your family and animals.
Rabies exists across the United States, with only Hawaii considered free of the virus. Most island states and nations attained free status by eradication of infected animals, testing of all incoming animals and vaccination. Their natural water barrier provides biosecurity from uninvited animal guests. For those of us surrounded by land, rabies virus will always be a reality via animal migration.
While all mammals are capable of being infected with rabies, it’s rare in very small mammals, like rats and squirrels. Raccoons, foxes, skunks and other wild animals are often the source of infection for livestock and other domestic animals. Dogs and cats often get it from fighting with wildlife, while horses, cattle and other livestock are likely to be bitten on the muzzle, udder or feet when encountering wildlife.
Saliva is the body fluid we all associate with rabies transmission, but spinal fluid, respiratory mucus and milk may also contain the virus. A bite is the most direct way to have a viral exposure, but because respiratory droplets may contain the virus, simply being in the presence of a rabid animal can be infective. This type of exposure can occur when entering caves inhabited by rabid bats.
Where the initial infection occurs on the body makes a difference in how the disease runs. If the initial exposure is through a bite, the biting animal’s saliva will be present in that wound. The virus latches onto the nerves in that area and move toward the brain at a pretty steady rate. So, for the animal bitten on the muzzle, the virus is going to get to the brain quickly and clinical signs will start relatively quickly after the bite. For a cow bitten on her back foot, that virus has a long way to go to get to the brain so there will be a delay before the disease is noticed. This is important because, in the case of the hind foot exposure, that length of time may be long enough for the initial bite to heal and be no longer noticeable. Therefore, not finding a bit wound on an animal suspected of having rabies doesn’t mean the disease can’t be rabies.
There is no typical set of signs of rabies. It can literally look like anything. My colleagues and I have seen rabies in cattle present as everything from a single limb lameness to overt seizures. Any signs that appear to be neurologic in origin and any changes in behavior should incite consideration of rabies.
There are three distinct syndromes described for rabies, but there is no way to define all the potential ways in which rabies can present.
In the furious form of rabies, animals are very excitable, easily startled and show rage. They may also strain as if constipated and act as if they are choking. Never stick your unprotected hand into the mouth of any animal that appears to be choking. Because these animals are unable to swallow, they drool and don’t want to eat or drink. Some may bellow relentlessly, with cows often sounding like bulls.
In the dumb form of rabies, reported to be most common in cattle, animals are often profoundly depressed and do not eat. This is in total contrast to the furious form that we all envision — dumb form animals are extremely passive, and it’s easy not to think of rabies in this way.
In the paralytic form, animals may be lame or unable to maintain proper placement and motion of their limbs.
Rabies can only be definitively diagnosed in veterinary species by postmortem exam or necropsy. The brain is removed and tested. When an animal is suspected to have rabies, it should only be handled by a veterinarian and only a veterinarian should remove the brain. Due to our high risk of exposure, most veterinarians are vaccinated against rabies.
Several years ago, I was called to look at a stocker calf with neurologic signs. He was down, had odd behavior and appeared to be blind. There are several more common causes of those symptoms in a calf that age, but the list always has to include rabies. I treated the animal for a more common disease and told the owner that rabies could be a possibility. I recommended that no one handle the calf, specifically to not handle the head, where exposure through saliva could easily happen. A couple of days later, I got a call that the calf had died and the owners were concerned because the husband had handled the calf’s head, getting saliva and mucus on his jeans before coming home. When he walked in the house, their toddler children came running up and hugged his legs. A truly frightening situation. At that point, I told them to immediately contact their physician, who determined the level of risk and an appropriate plan of action. Members of the family were ruled to have had high risk of exposure and underwent post-exposure prophylaxis, the series of injections given to prevent the disease after exposure. These are expensive, painful and must be started soon after exposure to be effective. Suffice it to say, it is preferable to avoid this situation altogether by taking great care when handling animals suspected to have the disease.
Consider rabies anytime you have an animal with a change in behavior or the appearance of neurologic disease. If you must handle these animals, wear latex gloves or palpation sleeves to protect your skin from exposure. Most of us who work on farms and ranches have cuts on our hands all the time, making us particularly vulnerable to the virus entering our skin. Have a veterinarian evaluate the animal and determine the proper course of treatment if another disease is suspected or a testing plan if rabies is a high concern. There is no treatment for rabies in animals.
Finally, get your animals vaccinated against rabies. Dogs, cats (especially barn cats) and horses should always be vaccinated. Discuss vaccination of other species like sheep, goats, pigs, cattle, llamas and alpacas with your veterinarian. A recent story of a young boy dying, even with aggressive treatment, should remind us all that this disease is not to be trifled with and is not a place to cut corners on our preventative medicine costs.
About the author: Dr. Meredyth Jones is an associate professor in the food animal medicine service at Oklahoma State University’s Veterinary Medical Hospital at the College of Veterinary Medicine. She earned her DVM degree from Oklahoma State University and is a Diplomate of the American College of Veterinary Internal Medicine (Large Animal).
Veterinary Viewpoints is provided by the faculty of the OSU Veterinary Medical Hospital. Certified by the American Animal Hospital Association, the hospital is open to the public providing routine and specialized care for all species and 24-hour emergency care, 365 days a year. Call 405-744-7000 for an appointment or more information.
OSU’s College of Veterinary Medicine is one of 32 accredited veterinary colleges in the United States and the only veterinary college in Oklahoma. The college’s Boren Veterinary Medical Hospital is open to the public and provides routine and specialized care for small and large animals. The hospital offers 24-hour emergency care and is certified by the American Animal Hospital Association. For more information, visit https://vetmed.okstate.edu or call 405-744-7000.