Effect of naturally occurring <i>Wolbachia</i> in <i>Anopheles gambiae s.l.</i> mosquitoes from Mali on <i>Plasmodium falciparum</i> malaria transmission.

Abstract

A naturally occurring <i>Wolbachia</i> strain (<i>w</i>Anga-Mali) was identified in mosquitoes of the <i>Anopheles gambiae</i> complex collected in the Malian villages of Dangassa and Kenieroba. Phylogenetic analysis of the nucleotide sequence of two 16S rRNA regions showed that <i>w</i>Anga-Mali clusters with <i>Wolbachia</i> strains from supergroup A and has the highest homology to a <i>Wolbachia</i> strain isolated from cat fleas (<i>Ctenocephalides</i>). <i>w</i>Anga-Mali is different from two <i>Wolbachia</i> strains previously reported in <i>A. gambiae</i> from Burkina Faso (<i>w</i>Anga_VK5_STP and <i>w</i>Anga_VK5_3.1a). Quantitative analysis of <i>Wolbachia</i> and <i>Plasmodium</i> sporozoite infection in field-collected mosquitoes indicates that the prevalence and intensity of <i>Plasmodium falciparum</i> sporozoite infection is significantly lower in <i>Wolbachia</i>-infected females. The presence of <i>Wolbachia</i> in females from a laboratory <i>Anopheles coluzzii</i> (<i>A. gambiae</i>, M form) colony experimentally infected with <i>P. falciparum</i> (NF54 strain) gametocyte cultures slightly enhanced oocyst infection. However, <i>Wolbachia</i> infection significantly reduced the prevalence and intensity of sporozoite infection, as observed in the field. This indicates that <i>w</i>Anga-Mali infection does not limit early stages of <i>Plasmodium</i> infection in the mosquito, but it has a strong deleterious effect on sporozoites and reduces malaria transmission.