Rabies in Ruminants
Adapted by Robert B. Moeller Jr. DVM, DACVP, DABT, California Animal Health and Food Safety Laboratory
Rabies is a rare viral disease to affect ruminants in California or the remainder of the United States. In 2010, 71 cattle were identified to have rabies in the United States. However, in certain areas of the world, particularly Central and South America, rabies is a common disease of cattle and small ruminants. While a rare problem here, rabies should always be considered as a possible infection if an animal is demonstrating neurological signs. In California, bats are the most common animal species that is identified with rabies. However, skunks, foxes and raccoons are also known to become infected with this viral disease and transmit this disease to other animals. In the United States, most cases of rabies in cattle are skunk associated. Infections often occur in cattle, sheep and goats that are confined in limited areas where the animal cannot escape and are bitten by the rabid animal. Rabies in all animals and man is almost always fatal.
Cattle infected with rabies often do not demonstrate the same clinical symptoms and may present with a variety of clinical signs. Infected animals may become aggressive and agitated; the animal often becomes very belligerent and may attack anything that moves. Other infected cattle may present clinically depressed and in a stupor state. Animals may also have difficulty swallowing and salivate excessively; these animals often appear to be choking due to a foreign body in the throat (no foreign body is found in the throat of the animal). Some cattle may also develop nonspecific neurological signs. Weakness of limbs with staggering and incoordination or paralysis of facial nerves can lead to difficulty picking up and chewing food. Animals may strain to urinate and bellow excessively. Many times these clinical signs cannot be differentiated from more common neurological problems in cattle such as anaplasmosis and hypomagnesemia (aggressive animals), pituitary abscess, listeriosis, Histophilus somnis, polioencephalomalacia or toxicities such as lead or locoweed.
Sheep and goats infected with rabies may present in an excitable agitated state which then progresses to one of severe depression and stupor. As with cattle, these animals may have difficulty drinking water or picking up and eating food (facial nerve damage). Like cattle, these clinical signs may mimic other common neurological diseases of sheep and goats such as lead toxicity, listeriosis, brain abscesses due to Corynebacterium pseudotuberculosis, Clostridium perfringens type D enterotoxemia, and West Nile virus (sheep).
In all these animals, rabies virus is shed in all body fluids and is found in high viral loads in the saliva, milk and urine. People exposed to these secretions are in danger of becoming infected with the virus. Consequently, it is important to have your veterinarian examine any animal that has developed neurological conditions and take appropriate samples to rule out rabies as the cause of the animal’s condition.