In Brazil, zoonotic visceral leishmaniasis (ZVL) control programs based on the mass elimination of seropositive dogs have failed to reduce the number of leishmaniasis cases. However, these programs have been done under sub-optimal conditions. We studied a cohort of dogs in an urban area in Brazil to determine, whether a dog-culling program optimized with: (i) replacement of a relatively low-sensitivity indirect immune-fluorescent test on blood eluate by a more sensitive enzyme-linked immunosorbent assay on serum blood samples; (ii) shortening of the time interval from serodiagnosis to removal of dogs; (iii) screening a high proportion of the dog population could reduce the incidence of canine Leishmania infection (CLI). The study ran from December 1997 to July 2000, with four follow-up assessments performed at approximately 8-month intervals. All dogs seropositive for anti-Leishmania antibodies were promptly eliminated. A large number of new dogs immigrated to the study area throughout the study period. They comprised 43.8-49.8% of the cohort at each follow-up assessment, and upto 15% of them already had Leishmania infection. Overall, 42 news cases of CLI were identified, for a crude incidence rate of 11.8 cases per 100 dog-years (95% CI 8.6-15.6). In the first, second, third and fourth follow-up assessments the incidence rates were 8.2 (95% CI 3.0-17.9), 12.2 (95% CI 6.3-21.2), 16.4 (95% CI 8.5-28.6) and 13.6 (95% CI 7.1-23.8), respectively. There was no statistically significant change in these rates throughout the study period. Our results suggest that dog-culling programs do not reduce the incidence of CLI, even with an optimized intervention. Possible reasons for this failure include: currently available serologic methods lack sufficient sensitivity and/or specificity to accurately identify all infected dogs warranting removal in order to prevent Leishmania transmission; destroyed dogs are immediately replaced by susceptible puppies, and quite often, by already infected dogs; and other reservoirs may be involved in maintaining canine infection. Further efforts on ZVL control should be directed to developing new strategies or to testing control methods already in place with properly designed trials.

Despite the wealth of information on the prevalence and correlates of canine Leishmania infection (CLI), data on its incidence are still sparse, and little is known regarding risk factors for CLI. We studied a cohort of dogs in an urban area in Brazil to determine whether incidence varied with age, breed, and environmental characteristics. The mean follow-up was 1.5 years, and the crude incidence rate was 11.8 cases/100 dog-years (95% confidence interval [CI] ‫ס‬ 8.6−15.6). In the multivariate analysis, short fur was the strongest predictor of CLI (relative risk [RR] ‫ס‬ 9.4). In addition, our data indicate that raising pigs (RR ‫ס‬ 4.1), chickens (RR ‫ס‬ 3.3), or other livestock (RR ‫ס‬ 2.6) significantly increased the risk of CLI. Thus, suggesting control measures directed towards modifying the environmental factors favoring contact between vectors, reservoirs, and susceptible humans, such as proximity to pigpens or hen houses. Furthermore, conventional control programs of insecticidal spraying of human dwellings should also apply insecticide in and around animal sheds.

Foram investigadas áreas de risco de leishmaniose visceral canina no município de Camaçari, Bahia. Um total de 278 cães distribuídos em 141 residências, pertencentes a 20 áreas de risco investigadas, foi examinado sorologicamente (ELISA). A soroprevalência geral foi 21,7% (56/258) depois da exclusão dos 20 cães usados no início do estudo para delimitar a área. Os resultados respectivos das análises univariada e multivariada dos fatores relacionados à infecção do cão por Leishmania chagasi, a captura e distribuição do vetor na área e a metodologia usada para localizar os focos caninos são discutidos.

There was a high social cost in terms of years of potential life lost and partial hospital costs associated with leptospirosis when compared to the possibility of early treatment or prevention of infection, both of which could minimize the impact of the disease on the Brazilian population.

These findings suggest a common source of infection for all patients and reinforce the hypotheses of spread of M. massiliense BRA100 in Brazilian hospital surgical environment in recent years.