Livestock Update, October 2006
Dr. W. Dee Whittier, Extension Veterinarian, Cattle, VA-MD Regional College of Vet. Med.
Cattle are one of the most common domestic animals to contract deadly rabies putting cattle producers at an increased risk themselves. In a year 2000 report only cats exceeded cattle in the incidence of rabies cases in domestic animals. A large amount of effort goes into keeping pet owners safe from rabies through vaccination programs and educational efforts but those who routinely handle cattle are less often reminded of the threat of this disease which is almost always fatal.
Virginia is considered to be endemic for rabies in most areas. This means that there are low levels of the disease present that are maintained by some animal reservoir. In Virginia’s case, raccoons, skunks, foxes and bats are the animals where the disease persists, with raccoons being the most important. Since the virus that causes the disease only survives out of the animal for short periods of time, it would disappear from an area if it were not constantly being incubated and spread in these wildlife populations. Fortunately, human contact with these animals is infrequent so that humans are seldom at risk due to exposure to wildlife. Figure 1 shows the cycle of the rabies virus in raccoons.
Figure 1. The infectious path of rabies virus
|4. The virus incubates in raccoon's body for approximately 3-12 weeks. The raccoon has no signs of illness during this time.|
3. Rabies virus spreads through the nerves to the spinal cord and brain.
2. Rabies virus enters the raccoon through infected saliva.
5. When it reaches the brain, the virus multiplies rapidly, passes to the salivary glands, and the raccoon begins to show signs of disease.
6. The infected animal usually dies within 7 days of becoming sick.
|1. Raccoon is bitten by a rabid animal.|
Cattle most often become infected with rabies when they come in contact with infected raccoons, skunks or foxes. Cattle’s curious nature puts them especially at risk when they investigate an animal which is acting strangely in their area. Rabid animals are prone to bite livestock on the nose or extremities. Because these wildlife species are well adapted to areas where cattle are kept the threat of becoming infected is always present. Cattle in barns or other enclosures are not spared the risk of rabies since infected wildlife commonly frequent cattle housing.
Symptoms of rabies in cattle vary considerably. The slobbering, aggressive cow is only one way that the disease presents. Initial signs of the disease may be quite mild with cattle appearing depressed, not eating and isolating themselves. As the disease progresses function of some body parts decreases. This might result in the inability to swallow so that saliva is drooled but it might also be weakness in a leg or legs or a drooping ear or head. Animal behavior may also be varied. A few rabid animals are aggressive but many are sleepy and constant bellowing or straining is also seen. Most animals affected by the disease die within a week from the time that signs are first seen.
Because the signs of rabies are not always certain, animals that don’t fit a pattern of typical disease should be examined by a veterinarian. This is especially true if any signs of the disease suggest that the brain is involved in the disease. Animals that die with suspicious signs should be autopsied and official should be made aware of a rabies suspicion, both to protect those who perform the autopsy as well as to be sure that the right tests are done to be sure rabies will be detected if it was the disease.
Anyone who suspects that they have been exposed to rabies, through association with rabid cattle or any other animal should seek medical attention immediately. Preventive vaccination is quite effective if initiated soon after exposure. Once the disease has incubated, the outcome is nearly always fatal.
Prevention of rabies in cattle is not an easy task. Vaccines are available but are so expensive that their routine use in cattle herds is not recommended unless a farm has a very high threat of the disease. Wildlife control should be a concern for all cattle operations for rabies prevention and for other health and safety reasons. In some cases, hunting and trapping should be employed. In all cases, attempts should be made to secure feeds that would attract wildlife likely to be rabid.
While rabies is not a high incidence disease on Virginia cattle operations, the threat to the health of farm personnel is so great that a constant vigilance for it should be practiced by all cattle workers in Virginia.