Vaccination with LiESP/QA-21 (CaniLeish®) reduces the intensity of infection in Phlebotomus perniciosus fed on Leishmania infantum infected dogs-A preliminary xenodiagnosis study

Ten Beagle dogs at different stages of Leishmania infantum infection, among which 6 had received a full course of LiESP/QA-21 (CaniLeish®; Virbac) vaccination, were exposed to the bites of reared Phlebotomus perniciosus to assesses their infectiousness potential. This was found to be negligible/nil in 2 seronegative dogs with subpatent infection. Among the 8 dogs with active infection (=positive serology, bone-marrow qualitative PCR and lymph node culture), 2/5 vaccinated (40.0%) and 2/3 nonvaccinated dogs (66.7%) were infectious to the sand flies (p = 0.5). However significantly fewer of the sand flies which fed on the vaccinated dogs were infected when compared to those which fed on the control dogs (10/82 compared to 30/49) (chi-squared test, p < 0.0001; mixed binomial model with the dog identity included as a random effect, p = 0.03). Furthermore, there was a significant difference in the proportion of sand flies with >500 parasites in their gut (i.e. a higher risk for subsequent transmission): 3.7% for vaccinated dogs compared with 28.6% for nonvaccinated dogs (Fisher's exact test, p < 0.0001; binomial mixed model, p = 0.006). Although preliminary, these results suggest value in further investigations on L. infantum transmissibility parameters in LiESP/QA-21 vaccinated dogs.