Abstract
BackgroundThe development of pathogens transmitted by haematophagous invertebrate vectors is closely connected with the digestion of bloodmeals and is thus affected by midgut enzymatic activity. Some studies have demonstrated that avian blood inhibits Leishmania major infection in the Old World vector Phlebotomus papatasi; however, this effect has never been observed in the New World vectors of the genus Lutzomyia infected by other Leishmania species. Therefore, our study was focused on the effect of chicken blood on bloodmeal digestion and the development of Leishmania major in its natural vector Phlebotomus duboscqi, i.e. in a vector-parasite combination where the effect of blood is assumed. In addition, we tested the effect of avian blood on midgut trypsin activity and the influence of repeated feedings on the susceptibility of sand flies to Leishmania infection.MethodsPhlebotomus duboscqi females were infected by rabbit blood containing L. major and either before or after the infection fed on chickens or mice. The individual guts were checked microscopically for presence and localization of Leishmania, parasite numbers were detected by Q-PCR. In addition, midgut trypsin activity was studied.ResultsSand fly females fed on chicken blood had significantly lower midgut trypsin activity and delayed egg development compared to those fed on rabbits. On the other hand, there was no effect detected of avian blood on parasite development within the sand fly gut: similar infection rates and parasite loads were observed in P. duboscqi females infected by L. major and fed on chickens or mouse one or six days later. Similarly, previous blood feeding of sand flies on chickens or mice did not show any differences in subsequent Leishmania infections, and there was equal susceptibility of P. duboscqi to L. major infection during the first and second bloodmeals.ConclusionIn spite of the fact that avian blood affects trypsin activity and the oocyte development of sand flies, no effect of chicken blood was observed on the development of L. major in P. duboscqi. Our study unambiguously shows that sand fly feeding on avian hosts is not harmful to Leishmania parasites within the sand fly midgut.
Highlights
The development of pathogens transmitted by haematophagous invertebrate vectors is closely connected with the digestion of bloodmeals and is affected by midgut enzymatic activity
The effects of sand fly feeding on avian blood before and after infection To evaluate the effect of avian blood on Leishmania infection we followed three different experimental feeding schemes: (i) We evaluated the effect of chicken blood taken before infection
In the experiments presented here P. duboscqi females fed on chickens had half the midgut protein content compared to those fed on rabbits, which corresponds to the concentrations measured in chicken and rabbit blood
Summary
The development of pathogens transmitted by haematophagous invertebrate vectors is closely connected with the digestion of bloodmeals and is affected by midgut enzymatic activity. We tested the effect of avian blood on midgut trypsin activity and the influence of repeated feedings on the susceptibility of sand flies to Leishmania infection. Proteolytic activity in the Ingested blood affects the digestion and fecundity of sand flies and can affect Leishmania development. Adler [10] first suggested that products of blood serum digestion destroy Leishmania parasites in the midguts of ‘noncompatible’ sand fly species. According to Schlein and Romano [11] and Borovsky and Schlein [12], a specific component of the trypsinlike activity prevents the survival of L. donovani in the ‘noncompatible’ vector Phlebotomus papatasi while the ability to modulate this factor enables L. major to survive in ‘compatible’ sand fly species. Pimenta et al [13] described the susceptibility of Leishmania to midgut digestion in the ‘compatible’ vector P. papatasi as stage-specific: L. major amastigotes and fully transformed promastigotes were relatively resistant to P. papatasi proteolytic activity, whereas parasites within the amastigote-to-promastigote transition were highly susceptible being killed
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