Courtesy of Tony Leahy
Cases of visceral canine leishmaniasis had been confirmed in 21 states and southern Canada by the beginning of September.
Results of DNA and blood tests obtained by scientists at North Carolina State University's College of Veterinary Medicine and the national Centers for Disease Control and Prevention had confirmed the cases. NCSU researchers said the test results suggest leishmaniasis is substantially more widespread in North American canine populations than originally thought.
Dr. Edward Breitschwerdt, professor of small animal internal medicine at NCSU, commented that the disease, which can lead to chronic debilitation and kidney failure in dogs, and even death, is "extremely hard to diagnose." Dr. Breitschwerdt helped lead the research effort to facilitate more widespread testing for leishmaniasis after diagnosing the disease in dogs at a New York hunt club last spring (see JAVMA, June 15, 2000).
Until researchers determine how leishmaniasis is transmitted in the United States, the threat to human health is not completely known, Dr. Breitschwerdt said. Direct transmission would pose a far smaller risk to humans than transmission by insects such as sand flies or ticks. Vector transmission could create a serious public health concern, according to Dr. Breitschwerdt. The disease is potentially fatal in humans, but can be treated. Although there is no cure for leishmaniasis in dogs, remission is possible.
Dr. Breitschwerdt said leishmaniasis was originally thought not to be in the United States, but he acknowledged the possibility that there could have been cases in the United States that weren't diagnosed. "This [epizootic] may have been smoldering for 15 to 20 years," he said.
Visceral leishmaniasis is prevalent in southern Europe, India, and South America. Ongoing research efforts should allow scientists to determine the source of the US canine leishmaniasis, how it's being transmitted, and whether the cases in various states come from the same strain of the organism.
With the aid of his colleagues, Dr. Breitschwerdt implemented new diagnostic tests at the NCSU College of Veterinary Medicine last spring in response to a disease outbreak among Foxhounds at a New York hunt club. Using cytology, PCR amplification, and serologic testing, Dr. Breitschwerdt and his team confirmed that the disease was canine leishmaniasis.
A collaborative effort has been under way since February 2000 between the CDC and the Dutchess County (NY) Department of Health, the Walter Reed Army Institute of Research, the New York State Department of Agriculture and Markets, the New York State Department of Health, the Virginia Department of Health, and the NCSU College of Veterinary Medicine to investigate the outbreak. It's still not clear how the dogs in New York became infected.
Some of the investigative activities in progress or planned include continued serosurveys of Foxhounds, serosurveys of stray dogs, isolation of infective organisms from selected seropositive dogs; and serosurveys of humans at risk, such as Foxhound handlers and hunters. Epidemiologic information will also be collected to evaluate risk factors. Investigation will continue on the vector competence of sand flies.