Visceral leishmaniasis is an important zoonotic disease transmitted to humans and dogs through the bite of an infected sand fly. It is mostly confined to tropical regions in Central and South America, the Middle East, and Asia, and along the Mediterranean Sea. In endemic regions, large numbers of infected dogs serve as reservoir hosts, increasing transmission to humans. In recent years, cases of canine visceral leishmaniasis have been documented in the United States, Canada, and northern Europe. To determine the scale of infection in the United Kingdom, the authors analyzed all potential canine leishmaniasis cases from 2005 to 2007. The study confirmed 257 cases by using polymerase chain reaction, immunofluorescence assays, or direct observation of parasites in tissues. In all cases, the dogs had clinical signs consistent with Leishmania infection, such as weight loss, inappetence, and skin lesions. Analysis of the travel history of 183 dogs found that 105 had lived 6 months or more in Spain, where prevalence ranges from 40% to 90%.

COMMENTARY: Although canine leishmaniasis is mostly imported in the United Kingdom, it now appears to be resident in the United States. In 1999, a New York foxhound club experienced an outbreak of leishmaniasis. Of 250 dogs housed at the club, 29 died and 112 fell ill, with clinical signs such as weight loss, seizures, skin lesions, and renal failure.1 Since this initial outbreak, spontaneous natural infections have occurred in dogs throughout the country. A subsequent study examining more than 12,000 kenneled hunting dogs nationwide found Leishmania antibodies in 13% of dogs, spread over 18 states. Transplacental transmission and blood exchange appear to be the main modes of parasite spread in these dogs; however, sand fly species throughout the eastern United States have been experimentally validated as competent vectors and may be able to transmit the parasite to humans.

Canine leishmaniasis in the United Kingdom: A zoonotic disease waiting for a vector? Shaw SE, Langton DA, Hillman TJ. VET PARASITOL 163:281-285, 2009.

1. Canine visceral leishmaniasis, United States and Canada, 2000–2003. Duprey ZH, Steurer FJ, Rooney JA, et al. Emerg Infect Dis 12:440-446, 2006.