The saliva of tsetse flies contains a cocktail of bioactive molecules inducing specific antibody responses in hosts exposed to bites. We have previously shown that an indirect-ELISA test using whole salivary extracts from Glossina morsitans submorsitans was able to discriminate between (i) cattle from tsetse infested and tsetse free areas and (ii) animals experimentally exposed to low or high numbers of tsetse flies. In the present study, our aim was to identify specific salivary synthetic peptides that could be used to develop simple immunoassays to measure cattle exposure to tsetse flies. In a first step, 2D-electrophoresis immunoblotting, using sera from animals exposed to a variety of bloodsucking arthropods, was performed to identify specific salivary proteins recognised in cattle exposed to tsetse bites. Linear epitope prediction software and Blast analysis were then used to design synthetic peptides within the identified salivary proteins. Finally, candidate peptides were tested by indirect-ELISA on serum samples from tsetse infested and tsetse free areas, and from exposure experiments. The combined immunoblotting and bioinformatics analyses led to the identification of five peptides carrying putative linear epitopes within two salivary proteins: the tsetse salivary gland protein 1 (Tsal1) and the Salivary Secreted Adenosine (SSA). Of these, two were synthesised and tested further based on the absence of sequence homology with other arthropods or pathogen species. IgG responses to the Tsal152–75 synthetic peptide were shown to be specific of tsetse exposure in both naturally and experimentally exposed hosts. Nevertheless, anti-Tsal152–75 IgG responses were absent in animals exposed to high tsetse biting rates. These results suggest that Tsal152–75 specific antibodies represent a biomarker of low cattle exposure to tsetse fly. These results are discussed in the light of the other available tsetse saliva based-immunoassays and in the perspective of developing a simple serological tool for tsetse eradication campaigns to assess the tsetse free status or to detect tsetse reemergence in previously cleared areas.

Background: One of the alternatives for controlling malaria is using mosquito symbiotic bacteria to reduce Plasmodium transmission. Species of Serratia , a genus of the Enterobacteriaceae family, have been isolated from the midgut of mosquitoes and are commonly found in water, soil and plant surfaces. These bacteria have shown great promise in blocking the transmission of Plasmodium in mosquitoes. The aim of this study was to isolate and characterize the genus Serratia within the Anopheles gambiae complex from Burkina Faso. Methods: Mosquitoes were collected in three field sites located in Houet Province in western Burkina Faso (Dioulassoba, Vallée du Kou and Soumousso), transported to the laboratory and identified morphologically. The salivary gland, midgut, spermatheca, ovary of females and testis of males were dissected and their contents ground up. Different species of Serratia were identified by PCR targeting of the luxS gene of Serratia, followed by 16S ribosomal RNA (rRNA) sequencing. Results: Molecular analyses identified the isolates as belonging to the genus Serratia , and phylogenetic reconstruction revealed that these strains are highly similar to one another but distinct from Serratia strains previously reported in neighboring countries such as Ghana and Nigeria. The overall prevalence of Serratia among malaria vectors was 13.3%. This prevalence varied according to the development stage of mosquitoes, locality of origin and mosquito organ. Only one Anopheles coluzzii mosquito was co-infected with Serratia and Plasmodium falciparum . Conclusions: The results of this study support the presence of Serratia spp. in wild mosquitoes from Burkina Faso, we well as their potential use in malaria control. Graphical