Emerging trends in the seroprevalence of canine leishmaniasis in the Madrid region (central Spain)

Abstract

This report describes a cross-sectional serological survey of the epidemiology of canine leishmaniasis (CanL) performed in 2006 and 2007 in the Madrid region (central Spain) where the disease is endemic. The work presented here is one of the several studies conducted in different Spanish regions under the Integrated Project of the European Commission entitled Emerging Diseases in a changing European eNvironment (EDEN). The aim of this project is to identify and catalogue European ecosystems and environmental conditions that determine the spatial and temporal distributions and dynamics of several pathogenic agents including Leishmania infantum (EDEN-LEI). The study area (Madrid Autonomous Region) was selected on the grounds of its wide altitude range. This area was surveyed from NE to SW across its mountain range (Sistema Central) and plateau area. One thousand and seventy-six dogs from 32 villages were examined for clinical signs of CanL, and serum samples were obtained to determine several haematological and biochemical variables. Leishmaniasis-specific antibodies were identified using an indirect immunofluorescence antibody test (IFAT). 87 of the 1076 dogs were seropositive for the protozoan (IFAT: cut-off>or=1/80) indicating a seroprevalence of 8.1% (0-16.1% depending on the village). On the basis of a physical examination and the biochemical/haematological status of each dog, 32 of the 87 infected dogs were described as clinically healthy (37%). Seroprevalence showed a peak in young dogs (1-2 years) and a second larger peak among the older dogs (7-8 years). Factors correlated with a higher infection risk were age (OR=1.15 [95% CI: 1.07-1.22]), weight (OR=1.10 [95% CI: 1.04-1.16]), and living outdoors as opposed to in a home (OR=3.38 [95% CI: 1.42-8.05]). According to data from studies performed in 1992 in the same area, the seroprevalence of CanL has increased 1.54-fold [95% CI: 1.04-2.29]. Given that this increasing trend cannot be attributed to differences in the sociodemographic characteristics of the dog populations, it is proposed that environmental changes could have had an impact on vector and reservoir densities and their geographical distributions. Further studies designed to explain this trend should attempt to correlate sand fly densities and CanL seroprevalences with climate, land use and human changes.