Spotlight on Lyme disease
DVM: Is Lyme disease increasing?
Little: Well, certainly awareness of spread is important, especially if you are practicing in an area where transmission has only recently been recognized. Practice protocols may need to be updated with a renewed emphasis on tick control and perhaps periodic reconsideration about recommendations for vaccination. But I think it is also important that veterinarians remain aware of the prevalence of coinfection from other pathogens in dogs that test positive for Borrelia burgdorferi antibodies. We can't afford to stop looking for or considering coinfections once we make that initial diagnosis of a single tick-borne illness, like Lyme disease. If an animal has one tick-related infection, it may well have others. Coinfection should be particularly suspected when a patient fails to respond as expected to treatment for a single diagnosis.
DVM: Other than dogs, which other animals are most likely to contract Lyme disease?
Little: Horses are often infected in endemic areas, and recent case reports suggest this infection can cause neurologic disease and other clinical disease in some horses. As with dogs, not every animal infected will develop clinical Lyme disease. Antibodies to B. burgdorferi have also been reported in cats and cattle, but we don't have clear evidence of clinical disease associated with the infection.
DVM: I've read it's white-tailed deer and white-footed mice that are the primary maintenance hosts for the deer tick and the primary reservoirs for the B. burgdorferi infection. Is that still accurate?
Little: The white-tailed deer is the cornerstone species that supports the tick populations and, thus, allows transmission of Lyme borreliosis. Adult black-legged ticks thrive when deer are present, and since this is the reproductive stage, high deer numbers mean high tick numbers. The immature ticks feed on and acquire B. burgdorferi from rodents, but some recent data shows that other small mammals, like shrews and chipmunks, are just as important or even more important reservoir hosts in some regions.