CDC has recipe for 'purer' horse vaccine; canines may gain from research
While West Nile Virus is not expected to taint the average dog's bill of health in 2003, should the prognosis change, count on a new vaccine to hit the market just in time.
In fact, given appropriate approval, that vaccine will arrive anywayfor its intended species: the horse; dogs could be an indirect beneficiaryof the product.
Sources at Colorado State University (CSU) confirm that a vaccine isin "the last stages of approval," including safety trials, andis currently awaiting USDA's public comment.
The vaccine is classified a "second-generation" genetic vaccine.If approved, this vaccine, which is reportedly much cleaner and purer thanthe current killed vaccine being used on horses, would be a first of itskind to reach the market.
But is it really necessary for dogs?
"This vaccine component could be used in any species. It just hasto be tested for each of the species," says Dr. Jeffrey Chang, leadresearcher on the vaccine project at the Centers for Disease Control labat Fort Collins, Colo.
Whether canines stand to cash in on the vaccine is another story. Dr.Richard Bowen, a collaborator with Chang and professor at CSU, expects afew more canine cases in 2003, but adds, "It's hard to say whetheranybody's going to spend much time working on a vaccine for dogs."
Following studies of the effects of West Nile in dogs and cats, bothChang and Bowen conclude: horses are still the true victims.
In one study testing four dogs, Chang says all dogs became infected byWest Nile but showed no clinical signs. Some exhibited minimal virus.
"This is very preliminary data, but if this can be extrapolatedto compare to the equine cases, I think dogs should be a lot milder thanhorse cases," says Chang. "In four years, we only have five confirmedcanine cases (not all were fatal). I don't see it turning from five casesto 100 cases this year."
There isn't a story, says Bowen. "There's a (much greater) chancethat dogs will get hit by a car than killed by West Nile. The truth is,they're not very good hosts."
Studies of felines showed similar results - a few cats became mildlyill with slight temperature increase. All cats circulated the virus, someclearly higher than dogs, according to Bowen. Again, Bowen says he seesno cause for concern.
Currently, Chang says the primary goal is to publish intentions to testthis vaccine on horses in the field.
A key distinction between the available killed virus vaccine and thenew DNA-based genetic vaccine is that the latter does not use the virusper se, only part of a virus gene, yielding a vaccine of highest purity,according to Chang, a research microbiologist.
"We know which part of the virus gene is critical and is importantto stimulate protection," he explains. "We artificially clonepart of that gene." The gene is transferred into the tissue cell andthe tissue cell produces antigen similar to the killed virus vaccine. Thetissue cell then uptakes DNA, which will make the protein and produce animmune response.
A potential downside to the vaccine is production cost, which is estimatedto be 10 times higher than the killed vaccine.
That probably wouldn't dissuade horse owners, argues Chang. "Ifyou're a horse owner, you'd like your pet to have the best treatment possible,"says Chang.
Who'd buy it?
While Chang would not name any companies interested in marketing andproducing the vaccine, he did say the government has established a collaborativeresearch agreement with one company.
Industry insiders are equally tight-lipped about whether a vaccine specificallytargeting canines is under development, but Bowen cited Fort Dodge AnimalHealth as an interested party at least in the horse aspect.
"Fort Dodge is going to be marketing this vaccine" he says,"whether that will include dogs, I don't know." He says a cross-licenseis much more likely.
When asked about the potential for a vaccine for canines, a spokeswomanfrom Fort Dodge responded, "I can't speak about any specific productdevelopment, but I can tell you we're monitoring the disease in other speciesin general, besides horses."
Nevertheless, the vaccine can have canine application, says Chang. "Ifit's available veterinarians would probably use it, but how effective isthat? It's never been clinically proven."
The studies are to be published in the Journal of Emerging InfectiousDiseases later this year.