Health watch - pets and West Nile virus; seizures in dogs; vaccination of cats; other pet health issues

Animals, Winter, 2001 by Paul Gambardella

Are my pets at risk of acquiring West Nile virus?

Until recently, reports Jeff Bay, D.V.M., an internist at Rowley Memorial Animal Hospital in Springfield, a division of the Massachusetts Society for the Prevention of Cruelty to Animals/American Humane Education Society (MSPCA/AHES), West Nile virus was limited to the Eastern Hemisphere, but it seems to be on its way to becoming endemic in the northeastern United States. Wild birds are the primary hosts for West Nile virus, which is passed among animals via mosquito bites. Although domesticated fowl and other birds, including household parrots, budgerigars, and cockatiels, are also susceptible to the disease, infection in domestic birds has not yet been reported in the United States. Infection in horses and humans has been reported in the Northeast, however. Mammals are, in general, less susceptible to the virus, although contact with the mosquito vectors may be extensive. In rare cases, species such as cattle, dogs, donkeys, gerbils, mice, pigs, rabbits, rats, sheep, and squirrels have acquired West Nile virus elsewhere in the world.

The virus typically infects the central nervous system and causes neurological symptoms. Clinical signs in birds include weakness, incoordination, abnormal head posture, circling, and convulsions.

Affected horses can show signs of lethargy, hind-limb weakness, incoordination, and convulsions. Although West Nile virus infection is rare in the Northeast, you should contact your veterinarian if you observe neurological dysfunction in any of your pets.

The best way to prevent infection is to limit exposure to mosquitoes. In pet birds or small mammals, this can easily be achieved by limiting their time out of doors. You can use mosquito repellants on a dog just as you would for a child, taking special care to avoid contact with the dog's eyes or mouth and to keep the dose and frequency of administration within those recommended by the manufacturer. A variety of methods help limit mosquito exposure to livestock species; consult your veterinarian for the method most suitable to your situation.

I have a four-year-old Lab mix that had a seizure last year. She became very rigid and glassy-eyed and couldn't walk. She had another one recently that lasted about six minutes. The next day she seemed like her usual self. What triggers these seizures and what can I do to prevent them?

There are many causes of seizures, explains Allen Sisson, D.V.M., a neurologist at Angell Memorial Animal Hospital in Boston, a division of the MSPCA/AHES. In a four-year-old dog with such infrequent seizures, epilepsy is the most likely source. Although the exact cause of epileptic seizures is not known, an inherited defect in the brain's nerve cell metabolism is suspected. Hypoglycerma, low blood calcium, liver disease, kidney disease, lead poisoning, infectious diseases, and brain tumors, among other causes, can also produce seizures.

A veterinarian should examine your dog and conduct blood tests, such as a complete blood count, a serum chemistry profile (after a 24- hour fast), and a lead test. If all of these tests are normal and your veterinarian finds a normal neurological examination, the problem is most likely epilepsy. In some cases, an MRI of the brain and a spinal-fluid analysis are recommended to rule out a brain tumor or encephalitis. Because of your dog's youth and the infrequency of her seizures, these tests would not likely be advised.

Anticonvulsant drugs make seizures less frequent and less severe, but in many cases, the seizures cannot be prevented entirely. Anticonvulsants are generally not advised unless the dog has more than one seizure within 24 hours or the seizures occur more than once a month. Still, each case is different, and sometimes anticonvulsants are used for less frequent seizures.

Since Lucy is an indoor cat, does she have to be vaccinated anyway? If so, why?

According to Douglas Brum, D.V.M., a clinician at Angell Memorial, vaccination is a very important part of a general health plan for your indoor cat. Keeping your cat inside does decrease her likelihood of contracting an infectious disease, but it does not eliminate it. The upper respiratory viruses are airborne, and cats may become infected without leaving your home. Feline panleukopenia virus is a very hardy virus that could be brought into your home by a person who was in contact with a sick cat. Finally, even if your cat stays in, other animals from outside can still get into your house. It is not uncommon for bats to fly into houses, and a bat may carry rabies. Rabies vaccinations are also required by law in many states, whether a cat is a strictly indoor pet or not.

If my dog or cat needs to get a blood transfusion, where do veterinary hospitals get their blood?

According to Ann Marie Manning, D.V.M., a specialist in emergency medicine at Angell Memorial, it is not uncommon for a cat or dog to require a blood transfusion for a medical problem. Most veterinary hospitals have a means to respond to this need should it arise.