Over the past decade, high-throughput 16S rRNA gene sequencing studies have shown that mosquitoes harbor diverse bacterial communities in their digestive systems. However, previous research has yet to examine the overall bacterial community inside versus outside mosquitoes and whether bacteria found on the outside could pose a potential health threat through mechanical transfer.

Scientists at North Carolina State University examined the bacterial community of the external surface and internal body of female mosquitoes found in homes in Ivory Coast, Ivory Coast, Africa.

R. Michael Roe, William Neal Reynolds Distinguished Professor of Entomology at NC State and co-corresponding author of the study, said: “If you’re exposed to mosquitoes, you’re concerned about blood supply. We hypothesize that mosquitoes can physically transmit bacteria by landing on you or by defecating on household surfaces the way flies do.

“Maybe not, but no one has studied it before.”

Scientists at the Center Suisse de Recherches Scientifiques collected 79 adult female Anopheles coluzzii mosquitoes from homes in an Ivory Coast rice-producing area. The microbiomes of the mosquitoes’ inner and outer surfaces were examined at NC State.

The findings surprised scientists.

Loganathan Ponnusamy, an NC State principal investigator in entomology and co-corresponding author of the paper, said: “We found greater bacterial diversity internally than externally, which was not consistent with what has been found in blowflies, for example.”

“At the same time, we found many external bacterial differences between houses, but not many internal differences between houses, which makes sense. Much of what is found internally relates to nectar or honey consumed while mosquitoes forage outside.

The researchers also discovered fructobacillus for the first time in academic literature, often present in nectar sources such as flowers and beehives, suggesting that mosquitoes visited those plants or nectar sources.

Roe said, “This is another risk. Mosquitoes carry bacteria inside and out and enter your home, transmitting potentially disease-causing bacteria.”

Scientists also plan to continue their work by measuring mosquitoes with a bacterium that would never be found on human skin and seeing whether the bacterium transfers to an artificial membrane. They could then perform the same test on human arms.

Magazine reference:

  1. Kaiying Chen, Loganathan Ponnusamy, et al. Internal and external microbiota of domestically caught Anopheles coluzzii (Diptera: Culicidae) from Ivory Coast, Africa: Mosquitoes are nasty. PLOS ONE. DOI: 10.1371/journal.pone.0278912