Revisiting the paradigm of anhematophagy in male mosquitoes

Most female mosquitoes are reproductively obligate feeders on vertebrate blood to obtain nutrients required for egg production (driving transmission of vector-borne pathogens in the process), and which rely on plant sugars for their non-reproductive energy requirements. Male mosquitoes, on the other hand, are thought to rely exclusively on plant sugars for their energetic needs; indeed, this dichotomy is one of the central paradigms of medical entomology. Here, we provide multiple lines of evidence challenging this assumption. We show that when reared under dehydration/starvation conditions, male mosquitoes will readily take blood from a membrane feeder while CRISPR mutants with impaired humidity detection do not increase their bloodfeeding rates. For multiple mosquito species, dehydrated males are attracted to human hosts and attempt to probe. We also observed several instances where dehydrated probing males were able to successfully pierce vertebrate host skin and acquire blood from a vertebrate host. When fed a blood meal containing West Nile virus, male Cx. tarsalis mosquitoes became infected with and orally transmitted the pathogen at rates and titers equivalent to females. Finally, we collected wild, putatively blood-fed male mosquitoes from Texas, USA and Mallorca, Spain, and identified vertebrate DNA in these samples (canine and human, respectively). These data suggest that under specific circumstances male mosquitoes may be able to probe and/or ingest blood and transmit pathogens to vertebrate hosts. These results are a paradigm shift in our understanding of male mosquito biology and suggest they may be more directly involved in pathogen transmission cycles than previously recognized.