Understanding Phlebotomus perniciosus abundance in south-east Spain: assessing the role of environmental and anthropic factors

José Risueño,María Ortuño,Moisés Gonzálvez,Elena Goyena,Luis Jesús Bernal,Juana Ortiz,Eduardo Berriatua,Clara Muñoz,Bulent Alten,Pedro Pérez-Cutillas

doi:10.1186/s13071-017-2135-3

Abstract

BackgroundLeishmaniosis is associated with Phlebotomus sand fly vector density, but our knowledge of the environmental framework that regulates highly overdispersed vector abundance distributions is limited. We used a standardized sampling procedure in the bioclimatically diverse Murcia Region in Spain and multilevel regression models for count data to estimate P. perniciosus abundance in relation to environmental and anthropic factors.MethodsTwenty-five dog and sheep premises were sampled for sand flies using adhesive and light-attraction traps, from late May to early October 2015. Temperature, relative humidity and other animal- and premise-related data recorded on site and other environmental data were extracted from digital databases using a geographical information system. The relationship between sand fly abundance and explanatory variables was analysed using binomial regression models.ResultsThe total number of sand flies captured, mostly with light-attraction traps, was 3,644 specimens, including 80% P. perniciosus, the main L. infantum vector in Spain. Abundance varied between and within zones and was positively associated with increasing altitude from 0 to 900 m above sea level, except from 500 to 700 m where it was low. Populations peaked in July and especially during a 3-day heat wave when relative humidity and wind speed plummeted. Regression models indicated that climate and not land use or soil characteristics have the greatest impact on this species density on a large geographical scale. In contrast, micro-environmental factors such as animal building characteristics and husbandry practices affect sand fly population size on a smaller scale.ConclusionsA standardised sampling procedure and statistical analysis for highly overdispersed distributions allow reliable estimation of P. perniciosus abundance and identification of environmental drivers. While climatic variables have the greatest impact at macro-environmental scale, anthropic factors may be determinant at a micro-geographical scale. These finding may be used to elaborate predictive distribution maps useful for vector and pathogen control programs.

Highlights

Leishmaniosis is associated with Phlebotomus sand fly vector density, but our knowledge of the environmental framework that regulates highly overdispersed vector abundance distributions is limited
While climatic variables have the greatest impact at macro-environmental scale, anthropic factors may be determinant at a microgeographical scale
Sand fly abundance was monitored in 25 animal premises including 5 premises, sheep sheds and 2 dog kennels, in each of the main five geographical zones that are traditionally recognized in the Murcia Region: N, S, C, W and SE (Fig. 1, Table 1)

Summary

Introduction

Leishmaniosis is associated with Phlebotomus sand fly vector density, but our knowledge of the environmental framework that regulates highly overdispersed vector abundance distributions is limited. Among over 800 sand fly species worldwide, 12 have been identified in Spain [2] These include Phlebotomus perniciosus and P. ariasi, vectors of Leishmania infantum responsible for zoonotic visceral leishmaniosis in western Mediterranean countries; and P. papatasi and P. sergenti, vectors of L. major and L. tropica, respectively, that cause cutaneous leishmaniosis in Northern Africa and the Middle East. The great majority of sand fly distribution studies monitor adult stages only. Their activity is typically seasonal; they can be found over a broad altitudinal range and temperature is considered the main artifice of sand fly phenology patterns in Mediterranean countries [4]. The role of other climatic and environmental variables on sand fly abundance is still inconclusive due to the wide variety of natural habitats in which sand flies are found, and the complex interconnections between the multiple factors affecting sand fly biological cycles

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