Localization and tissue tropism of the symbiont <i>Microsporidia MB</i> in the germ line and somatic tissues of <i>Anopheles arabiensis</i>

Abstract

<i>Microsporidia MB</i> is a symbiont with a strong malaria transmission-blocking phenotype in <i>Anopheles arabiensis</i>. It spreads in mosquito populations through mother-to-offspring and sexual transmission. The ability of <i>Microsporidia MB</i> to block <i>Plasmodium</i> transmission, together with its ability to spread within <i>Anopheles</i> populations and its avirulence to the host, makes it a very attractive candidate for developing a key strategy to stop malaria transmissions. Here, we report tissue tropism and localization patterns of <i>Microsporidia MB</i>, which are relevant to its transmission. We find that <i>Microsporidia MB</i> accumulates in <i>Anopheles arabiensis</i> tissues, linked to its sexual and vertical transmission. Its prevalence and intensity in the tissues over the mosquito life cycle suggest adaptation to maximize transmission and avirulence in <i>Anopheles arabiensis</i>. These findings provide the foundation for understanding the factors that may affect <i>Microsporidia MB</i> transmission efficiency. This will contribute to the development of strategies to maximize <i>Microsporidia MB</i> transmission to establish and sustain a high prevalence of the symbiont in <i>Anopheles</i> mosquito populations for malaria transmission blocking.