Visceral leishmaniasis is an important emerging zoonotic disease. This study was conducted in southern France using client-owned outdoor dogs. A total of 771 dogs were screened for the study and 414 were enrolled. All dogs were seronegative at the start of the study and randomized to either a placebo (n = 209) or treatment group (n = 205). Dogs received either a subcutaneous treatment or placebo vaccine at 0 and 3 to 4 weeks and a booster dose at 12 months. Dogs were closely monitored for adverse effects. At the end of 2 years or 2 sandfly transmission cycles, 340 dogs were available for data analysis (placebo, n = 175; treatment n = 165). The leishmaniasis infection rate was 0.61% (1/165) in the vaccinated group and 6.86% (12/175) in the placebo group. Vaccine efficacy was calculated to be 92%. Immune function studies also found increased anti-Leishmania IgG reactivity among other changes in the vaccinated group. The authors concluded that this vaccine offered strong long-term protection against visceral Leishmania in the field. Study funded by Agence Francaise de l'Inovation

COMMENTARY: Leishmaniasis accounts for about 57,000 human deaths annually worldwide. Dog ownership is a known risk factor because dogs are a natural reservoir for Leishmania infantum (chagasi). The disease occurs in Central and South America. No human case has been reported in the U.S., but L infantum is endemic in foxhounds, having been identified in kennels from Missouri and Iowa and in 16 states east of the Mississippi River.1 The method of transmission in U.S. dogs is unknown. In this study, vaccinated dogs had a much lower (11%) rate of infection over a 2-year period than unvaccinated dogs-results that are very encouraging. This and previous reports of effectiveness2 suggest that vaccination may play a role in preventing and even eliminating leishmaniasis from foxhounds in North America. Further research is necessary to better define the role of vaccination as a preventive strategy. Vaccination of the general U.S. dog population cannot currently be recommended because the disease is limited almost exclusively to foxhounds.

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.
2. Leishmune vaccine blocks the transmission of canine visceral leishmaniasis. Absence of Leishmania parasites in blood, skin and lymph nodes of vaccinated exposed dogs. Nogueira FS, Moreira MA, Borja-Cabrera GP, et al. Vaccine 23:4805-4810, 2005.

Long-lasting protection against canine visceral leishmaniasis using the LiESAp-MDP vaccine in endemic areas of France: Double blinded randomized efficacy field trial. Lemesre J, Holzmuller P, Goncalves RB, et al. Vaccine 2007, in press.