Some mosquitoes that transmit malaria might also be capable of transmitting a pathogenic bacterium, according to a study. Rickettsia felis is a bacterium recently implicated as a human pathogen, particularly in patients diagnosed with "fever of unknown origin" in sub-Saharan Africa. The bacterium can be transmitted by fleas, but it is unknown if there are other possible modes of transmission. Given that human R. felis infections have been prevalent in malaria-endemic regions, Philippe Parola and colleagues explored the possibility that the mosquito Anopheles gambiae, which transmits malaria, can also transmit R. felis. The authors fed mosquitoes on either blood or cellular media, both infected with R. felis, and found R. felis DNA in the mosquitoes' tissues for up to 2 weeks after feeding. R. felis DNA was also found on the cotton used to feed the mosquitoes after infection, suggesting that the mosquitoes could transmit bacteria through saliva when biting. The authors observed bacteria in the salivary glands of infected mosquitoes, as well as in mosquito ovaries, although the mosquitoes did not transmit the infection to their offspring. Notably, when infected mosquitoes fed on healthy mice, the mice developed transient infections. The findings suggest that A. gambiae mosquitoes could potentially transmit R. felis in the wild.