Health officials say the West Nile virus has been detected in mosquitoes in Washington, Illinois, throughout much of California, and even in Las Vegas, where mosquitoes would seem to be less common.
According to the Centers for Disease Control (CDC), nearly 44,000 cases of the West Nile virus have been reported in the U.S. since 1999. Of those, more than 20,000 people have had infections of the brain or spinal cord, and more than 1,900 people have died. While these numbers are low given the general U.S. population, they are powerful if you or someone you know has been affected by the virus.
In 2015, 44 states and the District of Columbia in the continental U.S. reported 2,175 cases of West Nile virus in people, according to the CDC. Many reports show mosquito populations are on the rise, and some areas of the U.S. have also reported cases of other viruses spread by mosquitoes, such as eastern equine encephalitis virus or La Crosse encephalitis virus.
Dogs are susceptible to West Nile (and also other types of encephalitis), but most dogs don’t show signs or get sick. Still, just like with people, some dogs do get sick.
Back in 2003, following the identification of West Nile in a domestic dog and also in a wolf in Illinois, a CDC study found the epidemiology of West Nile in canids is likely similar to that in humans: sporadic disease cases with no important role in viral transmission or maintenance. The authors of the report suggested further investigation was needed to confirm the epidemiology of the virus in canids and to monitor disease in other known and novel host species. However, the studies have not been done or have been limited.
According to some of the research, cats are more likely than dogs to show minor signs of infection from West Nile, especially mildly elevated temperatures and lethargy, but neither animal has been shown to exhibit neurological problems. Both dogs and cats developed titers of West Nile when bitten by infected mosquitoes or as a result of feeding on infected birds or mice; however, they are not considered to be natural hosts for further spreading of the disease. Dogs especially are unlikely to serve as amplifying hosts since the virus level appears to be low in infected dogs. Cats, although not as effective as birds to serve as hosts for West Nile, appear to be capable of infecting mosquitoes, although it is unclear whether the virus levels in their bloodstream are at a high enough level to do so. Pet birds are potentially particularly susceptible to West Nile.
Of course, West Niles isn’t the only mosquito-carried illness that can affect our pets. The big one is heartworm disease. Heartworm can be deadly to dogs, and the treatment for heartworm can actually make dogs sick. But, once infected, there is no choice, treatment is required, and that treatment is expensive. Prevention is, of course, preferred. Traditional heartworm protection works to prevent disease, but it doesn’t protect against heartworm because mosquitoes still bite protected pets and transmit microfilaria (“baby heartworm”). It’s now thought that these microfilaria could be damaging to dogs. The good news is that protection does inhibit development of adult heartworm.
However, in increasing places around the U.S., there is resistance to traditional heartworm products. So, what should we do? The answer seems obvious: to stop the bite in the first place, which some professionals call a “double-defense.” A product that offers this strategy, also kills fleas and ticks, and is called Vectra 3D. Preventing the bite prevents those microfilaria from entering a pet’s bloodstream in the first place. And, as noted, mosquitoes carry other pathogens that can sicken pets. Mosquito illnesses don’t affect animals when there is no bite in the first place. In fact, Vectra 3D repels and kills mosquitoes.
In cats, there is no similar product that repels and kills mosquitoes. However, there are heartworm preventives. Prevention is exceedingly important in cats, since there is no treatment for heartworm in cats. Ferrets are also susceptible to heartworm.