Cryptic Leishmaniosis by Leishmania infantum, a feature of canines only? A study of natural infection in wild rabbits, humans and dogs in southeastern Spain.

An epidemiological study was carried out to investigate asymptomatic Leishmania infantum infection by PCR and ELISA in wild rabbits, humans and domestic dogs in southeastern Spain. Seroprevalence was 0% (0/36) in rabbits, 2% (13/657) in humans and 7% (14/208) in dogs. The prevalence of PCR-positives was 0.6% (1/162) in rabbits tested in a wide range of tissue samples, 2% (8/392) in humans analysed in blood samples and 10% (20/193) and 67% (29/43) in dogs analysed in blood and lymphoid tissue samples, respectively. Results suggest that wild rabbits have a very low risk of becoming chronically infected with L. infantum, and provide further evidence that cryptic L. infantum infection is widespread in the domestic dog population and is also present in a comparatively smaller proportion of healthy humans. The epidemiological and clinical implications of these findings are discussed.

Geographical variation and factors associated to seroprevalence of canine leishmaniosis in an endemic Mediterranean area.

This article retrospectively analyses the spatial distribution and dog- and environmental-level risk factors associated to Leishmania infantum seroprevalence among 807 asymptomatic dogs in the Municipality of Crevillente in Alicante in southeast Spain in 1999. They represented 60% of the dogs in this 103 km2 area, with a human census of 27 034 people and 90% lived in Crevillente town. The estimated seroprevalence (95% confidence interval) in 714 dogs > or =1-year old was 22% (19-25) however; it was 12% (8-15) in town dogs and 0-100% in other administrative zones. High-medium seroprevalence zone clustered along a northeast-southwest fringe and around the town. They comprised the highest and driest inhabited part of the municipality, where farmland was interspersed by residential detached houses, whilst null-low seroprevalence zones included larger farmland extensions and two small rural villages. Predominant vegetation and ground soil type were bush, non-irrigated fruit trees and conglomerate crust and sandstone in medium-high seroprevalence zones and irrigated grassland and fruit trees and colluvial deposits in null-low seroprevalence zones. Random effects logistic regression indicated that the prevalence of infection with L. infantum was higher for dogs sharing residence with infected dogs, increased until 5-6 years old and with body weight and was associated to increasing conglomerate crust and low surface water in the dog's zone of residence. The study confirms that L. infantum infection is endemic in this part of Spain and shows that prevalence can vary significantly within a small area depending on specific demographic and environmental factors conditioning the habitat of the local L. infantum vector, Phlebotomus perniciosus. It suggests similar low-scale variability is present in other geographically variable endemic areas and should be investigated to design Leishmaniosis risk maps and cost-effective, evidence-based, targeted control interventions.