Contrasting patterns of Asaia association with Plasmodium falciparum between field-collected Anopheles gambiae and Anopheles coluzzii from Cameroon

The widespread prevalence of Asaia in mosquitoes makes it a potential candidate for paratrangenic control in Anopheles. To better understand whether this bacterium could be used for malaria control, we quantified Asaia in An. gambiae s.l populations in malaria endemic regions examining co-infection with Plasmodium falciparum. Adult Anopheles mosquitoes were collected across two different eco-geographical localities in Cameroon, during both the dry and wet seasons. DNA was extracted from whole individual mosquitoes, and real time-qPCR amplification of the 16S ribosomal RNA was used to quantify Asaia in both An. gambiae and An. coluzzii samples. We also detected and quantified P. falciparum infection in the same mosquitoes. The density of Asaia was successfully quantified in a total of 864 field mosquitoes, comprising of 439 An. gambiae from Bankeng and 424 An. coluzii collected from Gounougou. Interestingly, a higher prevalence of Asaia in An. gambiae (88.3%) compared to An. coluzzii (80.9%) was observed. Moreover, the density of Asaia in both species was significantly affected by seasonal changes in the two localities. Furthermore, a significant difference between the infection densities of Asaia and the Plasmodium infection status in the two species was recorded. However, no correlation was observed between the number of Asaia and P. falciparum infections. This study provides evidence that naturally occurring Asaia infection is not correlated to P. falciparum development within An. gambiae and An. coluzzii. Nevertheless, further studies incorporating experimental infections are required to better investigate the correlation between Anopheles mosquitoes, Asaia, and Plasmodium. IMPORTANCE The symbiont Asaia has emerged as a promising candidate for paratransgenic control of malaria, but further analysis of its biology and genetics across Africa is necessary. In this study, we investigated and quantified the influence of Asaia in naturally infected An. gambiae s.l. populations with the malaria parasite Plasmodium falciparum. Genomic DNA was extracted from whole individual mosquitoes collected from two localities, and Asaia was quantified using real-time qPCR by amplification of the 16S ribosomal RNA gene. We also detected and quantified Plasmodium falciparum infection in the same mosquitoes and established the correlation between Asaia and Plasmodium coinfection. This study provides evidence that naturally occurring Asaia infection is not correlated with P. falciparum development within An. gambiae and An. coluzzii mosquitoes.