Biting midges (Ceratopogonidae) as vectors of avian trypanosomes

Milena Svobodová,Olga V Dolnik,Jana Rádrová,Ivan Čepička

doi:10.1186/s13071-017-2158-9

Abstract

BackgroundAlthough avian trypanosomes are widespread parasites, the knowledge of their vectors is still incomplete. Despite biting midges (Diptera: Ceratopogonidae) are considered as potential vectors of avian trypanosomes, their role in transmission has not been satisfactorily elucidated. Our aim was to clarify the potential of biting midges to sustain the development of avian trypanosomes by testing their susceptibility to different strains of avian trypanosomes experimentally. Moreover, we screened biting midges for natural infections in the wild.ResultsLaboratory-bred biting midges Culicoides nubeculosus were highly susceptible to trypanosomes from the Trypanosoma bennetti and T. avium clades. Infection rates reached 100%, heavy infections developed in 55–87% of blood-fed females. Parasite stages from the insect gut were infective for birds. Moreover, midges could be infected after feeding on a trypanosome-positive bird. Avian trypanosomes can thus complete their cycle in birds and biting midges. Furthermore, we succeeded to find infected blood meal-free biting midges in the wild.ConclusionsBiting midges are probable vectors of avian trypanosomes belonging to T. bennetti group. Midges are highly susceptible to artificial infections, can be infected after feeding on birds, and T. bennetti-infected biting midges (Culicoides spp.) have been found in nature. Moreover, midges can be used as model hosts producing metacyclic avian trypanosome stages infective for avian hosts.

Highlights

Avian trypanosomes are widespread parasites, the knowledge of their vectors is still incomplete
Experimental infection of C. nubeculosus biting midges C. nubeculosus was highly susceptible to several strains of avian trypanosomes
Over 90% of individuals were infected with T. bennetti strain APO7; heavy infections were found in 50% of individuals on day 8–9, and in 80% on day 9–10 (Fig. 1)

Summary

Introduction

Avian trypanosomes are widespread parasites, the knowledge of their vectors is still incomplete. Despite biting midges (Diptera: Ceratopogonidae) are considered as potential vectors of avian trypanosomes, their role in transmission has not been satisfactorily elucidated. Avian trypanosomes have been shown to form three distinct evolutionary groups, each consisting of several lineages [1,2,3]. The lifecycles of several lineages of avian trypanosomes belonging to groups B and C have been clarified (see below), many of them remain unknown, including the entire T. bennetti (s.l.) group A. We have described or confirmed life-cycles of several avian trypanosome species which differ in vectors. The vector of Trypanosoma bennetti (and related lineages of avian trypanosomes) remains unknown. Strains belonging to T. bennetti group were found in European passerine birds as well as in raptors, and isolation from nestlings and yearlings

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