Population dynamics and habitat preferences of Phlebotomus orientalis in extra-domestic habitats of Kafta Humera lowlands – kala azar endemic areas in Northwest Ethiopia

BACKGROUND: Kafta Humera lowlands are endemic for kala-azar (visceral leishmaniasis). These lowlands are characterized by black clay soil which is used for growing sesame, sorghum and cotton for commercial purposes. The aim of this study was to determine seasonal dynamics and habitat preferences of Phlebotomus orientalis, the vector of kala-azar, in extra-domestic habitats of Kafta Humera lowlands. METHODS: CDC-light Trap [CDC-LT] and Sticky paper Trap [ST] were used to collect sand flies from different habitats before species identification by their morphological characteristics using appropriate keys. Data summarized and analyzed included: species, sex, density, habitats, type of trap used and date (month). RESULTS: A total of 389,207 sand flies using CDC-LT (n = 955) and ST (n = 5551) were collected from May 17, 2011 to June 6, 2012. The highest Mean Monthly Density (MMD) of P. orientalis trapped by CDC-LT was found in thickets of Acacia seyal in March (64.11 ± 75.87). The corresponding highest MMD of P. orientalis trapped by STs was found in April (58.69 ± 85.20) in agricultural field. No P. orientalis were caught in September using CDC traps and July-October using sticky traps. The overall MMD of P. orientalis trapped by CDC-LT was 15. 78 ± 28.93 (n = 320) in agricultural field, 19.37 ± 36.42 (n = 255) in thickets of A. seyal, and 3.81 ± 6.45 (n = 380) in dense mixed forest. Similar habitats in different localities did not show statistically significant difference for the MMD of P. orientalis trapped by CDC-LT (p = 0.117) and ST (p = 0.134). CONCLUSION: Agricultural fields and thickets of A. seyal habitats, which exhibit extensive soil cracks and fissures, as opposed to dense mixed forests, serve as preferred breeding sites for P. orientalis.