Decrease of the incidence of human and canine visceral leishmaniasis after dog vaccination with Leishmune® in Brazilian endemic areas

Abstract

Leishmune, the first prophylactic vaccine licensed against canine visceral leishmaniasis (CVL), has been used in Brazil since 2004, where seropositive dogs are sacrificed in order to control human visceral leishmaniasis (VL). We demonstrate here that vaccination with Leishmune does not interfere with the serological control campaign (110,000 dogs). Only 1.3% of positivity (76 among 5860) was detected among Leishmune uninfected vaccinees. We also analyzed the possible additive effect of Leishmune vaccination over dog culling, on the decrease of the incidence of CVL and VL in two Brazilian endemic areas, from 2004 to 2006. In Araçatuba, a 25% of decline was seen in CVL with a 61% decline in human cases, indicating the additive effect of Leishmune vaccination of 5.7% of the healthy dogs (1419 dogs), on regular dog culling. In Belo Horizonte (BH), rising curves of canine and human incidence were observed in the districts of Barreiro, Venda Nova and Noroeste, while the canine and human incidence of Centro Sul, Leste, Nordeste, Norte, Pampulha and Oeste, started to decrease or maintained a stabilized plateau after Leishmune vaccination. Among the districts showing a percent decrease of human incidence (-36.5%), Centro Sul and Pampulha showed the highest dog vaccination percents (63.27% and 27.27%, respectively) and the lowest dog incidence (-3.36% and 1.89%, respectively). They were followed by Oeste, that vaccinated 25.30% of the animals and experienced an increase of only 12.86% of dog incidence and by Leste and Nordeste, with lower proportions of vaccinees (11.72% and 10.76%, respectively) and probably because of that, slightly higher canine incidences (42.77% and 35.73%). The only exception was found in Norte district where the reduced human and canine incidence were not correlated to Leishmune vaccination. Much lower proportions of dogs were vaccinated in Venda Nova (4.35%), Noroeste (10.27%) and Barreiro (0.09%) districts, which according to that exhibited very increased canine incidences (24.48%, 21.85% and 328.57%, respectively), and pronounced increases in human incidence (14%, 4% and 17%, respectively). The decrease of canine (p=-0.008) and human incidences (p=-0.048) is directly correlated to the increase of the number of vaccinated dogs, confirming the additive control effect of Leishmune vaccination over dog culling, reducing the parasite reservoir, protecting dogs and, in this way, reducing the risk of transmission of VL to humans and becoming a new effective control tool.

Diagnostic Value of Conjunctival Swab Sampling Associated with Nested PCR for Different Categories of Dogs Naturally Exposed to Leishmania infantum Infection

“…Disease management represents a serious problem, since both symptomatic and asymptomatic dogs can be infectious to phlebotomine vectors (26,28), and the available antileishmanial drugs have limited efficacy in dogs. Furthermore, although progress has been made in CanL vaccination in the past decade, an effective Leishmania vaccine against CanL infection is not available worldwide (20,34).…”

Questionnaire-based survey on canine leishmaniosis (Leishmania infantum) in Greece

“…Η υιοθέτηση επιστημονικά τεκμηριωμένων μεθό δων πρόληψης, όχι μόνο αυτών που υπάρχουν σήμε ρα και με τις οποίες επιτυγχάνεται η μείωση της έκ θεσης των σκύλων στα νύγματα των φλεβοτόμων (πυ-ρεθρινοειδή, DEET, κιτρονέλλα, παραμονή τη νΰχτα σε εσωτερικούς χώρους, σίτες σε πόρτες και παράθυ ρα) όσο και των αποτελεσματικών εμβολίων που α ναμένονται στο εγγΰς μέλλον, μπορεί, σε ένα βαθμό, να περιορίσει τη συχνότητα της ΑΣ (Killick-Kendrick et al 1997, Slappendel and Ferrer 1998, Reithinger et al 2001, Gavgani et al 2002, Noli and Auxilia 2005, Otranto et al 2007, Palatnik-de-Sousa et al 2009). Επισημαίνεται ότι με τα διαθέσιμα εντομοκτόνα/ε-ντομοαπωθητικά δεν αποτρέπεται πλήρως η μόλυνση, αν ληφθεί υπ' όψιν ότι η μέγιστη αποτελεσματικότη τα τους για την αποτροπή των νυγμάτων δεν ξεπερνά το 99%, ενώ, κάτω από ευνοϊκές περιβαλλοντικές συνθήκες, κάθε μη προστατευμένος σκύλος ενδέχεται να νυχθεί από περισσότερους από 100 φλεβοτόμους κάθε ώρα της νύχτας, από τους οποίους, όμως, μολυ σμένο κατά μέσο όρο είναι το 1% (Gradoni 2002).…”

Leishmaniasis

“…104 Results from recent field studies reveal that Leishmune decreases the incidence of both VL and CVL in endemic areas. 105 A second vaccine, Leish-Tec has been developed by the Hertape Calier-Saúde Animal and registered in 2007 in Brazil. It consists of adenovirus expressing the L. donovani A2 antigen.…”