Vector species-specific association between natural Wolbachia infections and avian malaria in black fly populations

Abstract

Artificial infection of mosquitoes with the endosymbiont bacteria Wolbachia can interfere with malaria parasite development. Therefore, the release of Wolbachia-infected mosquitoes has been proposed as a malaria control strategy. However, Wolbachia effects on vector competence are only partly understood, as indicated by inconsistent effects on malaria infection reported under laboratory conditions. Studies of naturally-occurring Wolbachia infections in wild vector populations could be useful to identify the ecological and evolutionary conditions under which these endosymbionts can block malaria transmission. Here we demonstrate the occurrence of natural Wolbachia infections in three species of black fly (genus Simulium), which is a main vector of the avian malaria parasite Leucocytozoon. Prevalence of Leucocytozoon was high (25%), but the nature and magnitude of its association with Wolbachia differed between black fly species. Wolbachia infection was positively associated with avian malaria infection in S. cryophilum, negatively associated in S. aureum, and unrelated in S. vernum. These differences suggest that Wolbachia interacts with the parasite in a vector host species-specific manner. This provides a useful model system for further study of how Wolbachia influences vector competence. Such knowledge, including the possibility of undesirable positive association, is required to guide endosymbiont based control methods.

First report of natural Wolbachia infection in the malaria mosquito Anopheles arabiensis in Tanzania

“…Indeed, pathogen inhibition may not be a consistent consequence of Wolbachia infection. For example, natural Wolbachia infections can increase the susceptibility of Aedes and Culex mosquitoes and Simulium blackflies to avian malaria parasites [ 40 – 42 ]. Therefore, it will be crucial to assess the impact of w Anga on malaria infections and vectorial capacity under natural, ecologically variable conditions.…”

Differential gene expression inDrosophila melanogasterandD. nigrosparsainfected with the sameWolbachiastrain

“…Independently of hosts’ particular phylogenetic position and ecology, the same Wolbachia strain can have different effects on different genetic backgrounds within and across host species (Ranz et al ., 2003; Herbert and McGraw, 2018). A recent study in three black fly species in the genus Simulium found differential Wolbachia prevalence among species, suggesting host-specific interactions (Woodford et al ., 2018). However, the mechanisms behind these interactions are not clear.…”

Aquatic Hemiptera in Southwest Cameroon: Biodiversity of Potential Reservoirs of Mycobacterium ulcerans and Multiple Wolbachia Sequence Types Revealed by Metagenomics

“…In this small sample, Wolbachia was found not only to be the dominant symbiont but also to be represented by multiple sequence types. While Wolbachia is ubiquitous in arthropods from terrestrial environments, very few data on its distribution in aquatic species existed until recently, apart from analyses of holometabolous, medically important vectors with aquatic larval stages (principally mosquitoes [107], but also blackflies [108,109], and some limited surveys in aquatic crustaceans [110,111]). However, a 2017 meta-analysis of Wolbachia prevalence in aquatic insects (n = 228 species) estimated that >50% of species are infected, with Hemiptera exhibiting a particularly high prevalence (69%) [38].…”