AUTHOR=Nattoh Godfrey , Maina Tracy , Makhulu Edward E. , Mbaisi Lilian , Mararo Enock , Otieno Fidel G. , Bukhari Tullu , Onchuru Thomas O. , Teal Evan , Paredes Juan , Bargul Joel L. , Mburu David M. , Onyango Everline A. , Magoma Gabriel , Sinkins Steven P. , Herren Jeremy K. 

TITLE=Horizontal Transmission of the Symbiont Microsporidia MB in Anopheles arabiensis

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.647183

DOI=10.3389/fmicb.2021.647183

ISSN=1664-302X

ABSTRACT=<p>The recently discovered <italic>Anopheles</italic> symbiont, <italic>Microsporidia MB</italic>, has a strong malaria transmission-blocking phenotype in <italic>Anopheles arabiensis</italic>, the predominant <italic>Anopheles gambiae</italic> species complex member in many active transmission areas in eastern Africa. The ability of <italic>Microsporidia MB</italic> to block <italic>Plasmodium</italic> transmission together with vertical transmission and avirulence makes it a candidate for the development of a symbiont-based malaria transmission blocking strategy. We investigate the characteristics and efficiencies of <italic>Microsporidia MB</italic> transmission between <italic>An. arabiensis</italic> mosquitoes. We show that <italic>Microsporidia MB</italic> is not transmitted between larvae but is effectively transmitted horizontally between adult mosquitoes. Notably, <italic>Microsporidia MB</italic> was only found to be transmitted between male and female <italic>An. arabiensis</italic>, suggesting sexual horizontal transmission. In addition, <italic>Microsporidia MB</italic> cells were observed infecting the <italic>An. arabiensis</italic> ejaculatory duct. Female <italic>An. arabiensis</italic> that acquire <italic>Microsporidia MB</italic> horizontally are able to transmit the symbiont vertically to their offspring. We also investigate the possibility that <italic>Microsporidia MB</italic> can infect alternate hosts that live in the same habitats as their <italic>An. arabiensis</italic> hosts, but find no other non-anopheline hosts. Notably, <italic>Microsporidia MB</italic> infections were found in another primary malaria African vector, <italic>Anopheles funestus s.s</italic>. The finding that <italic>Microsporidia MB</italic> can be transmitted horizontally is relevant for the development of dissemination strategies to control malaria that are based on the targeted release of <italic>Microsporidia MB</italic> infected <italic>Anopheles</italic> mosquitoes.</p>