Vigilance exposes cattle, canine WNV cases

Lincoln, Neb.-Judi Galeota wasn't surprised to learn her laboratory at the University of Nebraska, Lincoln (UNL) diagnosed two serological positives for West Nile Virus (WNV) in cattle. And despite the magnitude of the discoveries - the first two confirmations in the U.S. - it's "business as usual" at the UNL Veterinary Diagnostic Center (VDC), the supervisor of the VDC's Virology Laboratory says.

"If it was really a problem like the way it has been in horses,we would've known it by now, says Galeota. "I really am not very concernedabout cattle."

She's not worried despite that Nebraska is widely recognized as one ofthe leading cattle producers in the nation. The same state also leads ina less popular category - number of equine cases infected with West Nilein 2002 totaling more than 1,000.

But horses exposed to WNV pose no known threat to cattle, says Galeota.She believes the underlying reason for the bovine positives isn't statistical,but rather correlates with the unusual degree of vigilance by large animalveterinarians who are scouring farms for any signs of disease.

"We have done tremendous amounts of testing," says Galeota."I'm not sure other states have. Some veterinarians are much more intellectuallycurious than others. That's something you need to keep in mind in termsof skewing any conclusions you want to come to."

Since being inundated with such large volumes of equine WNV cases, Nebraskaveterinary officials are hopeful next year's large animals will have developedimmunity.

Landmark cases

UNL sent its suspect bovine tissue samples to Cornell University, sincethere is no ELISA test for cattle. Cornell confirmed the WNV positive serologiesin mid-October. Should West Nile Virus be indicated as the causative agent,it would mark the first documented bovine cases of clinical disease in theUnited States and the world. (One other bovine in Illinois tested positiveserologically but not for clinical disease.)

Familiar signs

The UNL laboratory was only able to analyze tissues of one of the twocattle, an adult female Holstein, which tested positive for WNV serologicallywith exceptionally high titers (1:1024). The other, a 900-pound steer, waseuthanized with no further testing. It had presented with ataxia that progressedto paresis and was unresponsive to antibiotic treatment.

Both animals presented with neurological symptoms as well as rear limbataxia, and even anorexia.

Testing the market

Shortly following the bovine announcement, Galeota received a call fromFort Dodge Animal Health exploring novel vaccine possibilities. She saidsafety trials for a vaccine specific to dogs and cattle is under consideration,but the numbers for 2002 don't justify it.

Dog cases mounting?

The number of dogs affected by West Nile continues to raise a few eyebrows.

Louisiana Veterinary Medical Diagnostic Laboratory and the National VeterinaryServices Laboratory were the latest in a short string of laboratories tocite canine WNV cases - four were detected. The news came in the wake ofearlier reports of Illinois officials discovering the first case of WestNile in a canine in September, followed by Nebraska with four additionalcases of WNV-positive dogs.

"After a summer of 'dogs don't get WNV' these four veterinariansdecided to check anyway," says Dr. Martha Littlefield-Chabaud, assistantstate veterinarian of Louisiana, who confirmed signalment, history and clinicalsigns on the cases. Two dogs were not necropsied; another lived. Resultson the fourth dog are pending.

"As we notified the veterinarians in Louisiana about the observationsother calls have come from vets who have noticed similar clinical encephaliticsigns," she adds.

Although veterinarians are not diagnosing WNV they have included it onthe differential list.

When asked why the majority of canine cases surfaced in Illinois (leadingthe nation in human cases of WNV), Nebraska and Louisiana, Littlefield-Chabaudresponds, "It's because we had veterinarians that (were) looking forit.

"We're not trying to create a scare. We just want to get the wordout," she says.