Dynamic of Mayaro virus transmission betweenAedes aegyptiandCulex quinquefasciatusmosquitoes and a mice model
Authors: Krokovsky Larissa , Lins Carlos Ralph Batista , Guedes Duschinka Ribeiro Duarte , Wallau Gabriel da Luz , Ayres Constância Flávia Junqueira , Paiva Marcelo Henrique Santos 
Published: November 2022

Mayaro virus (MAYV) is transmitted byHaemagogus spp. mosquitoes and has been circulating in Amazon areas in the North and Central West regions of Brazil since the 1980s, with an increase in human case notifications in the last 10 years. MAYV introduction in urban areas is a public health concern once the infection can cause severe symptoms similar to other Alphaviruses. Regarding to urban transmission, studies withAedes aegyptidemonstrate the potential vector competence of the species and the detection of MAYV in urban populations of mosquitoes. Considering the two most abundant urban mosquito species in Brazil, we investigated the dynamics of MAYV transmission byAe. aegyptiandCulex quinquefasciatusin a mice model. Mosquito colonies were artificially fed with blood containing MAYV and infection (IR) and dissemination rates (DR) were evaluated. On the 7thpost-infection day (dpi), IFNAR BL/6 mice were made available as a blood source to both mosquito’s species. After the appearance of clinical signs of infection, a second blood feeding was performed with a new group of non-infected mosquitoes. RT-q PCR and plaque assay were carried out with animal and mosquito’s tissues. We found forAe. aegyptia IR of 97,5-100% and a DR of 100% in both 7thand 14thdpi. RegardingCx. quinquefasciatus, the IR found was 13.1-14.81% and DR ranged from 60% to 80%. To evaluate the mosquito-mice transmission rate, 18 mice were evaluated (Test=12 and Control=6) forAe. aegyptiand 12 animals (Test=8 and Control=4) forCx. quinquefasciatus. All mice bitten by infectedAe. aegyptishowed clinical signs of infection while all mice exposed to infectedCx. quinquefasciatusmosquitoes remained healthy. Viremia found in those animals ranged from 2.5 × 108to 5 × 109PFU/ml.Ae. aegyptifrom the second blood feeding showed a 50% infection rate. Our study showed the applicability of an efficient model to complete arbovirus transmission cycle studies and suggests that theAe. aegyptipopulation evaluated is a competent vector for MAYV highlighting the risk of establishment of MAYV urban cycle. The mice model employed here can be used more extensively for arthropod-vector transmission studies, with laboratory and field mosquito populations, as well as with other arboviruses.

Author summary

Mayaro virus (MAYV) is an arbovirus maintained mostly in a sylvan cycle in South America, circulating between Haemagogus mosquitoes and wild animals. In Brazil, MAYV has been circulating in the northern region since early 80s, but a substantial increase in human cases has been reported in the past decade. MAYV infections may go undetected, as clinical symptoms are mistaken with other arboviruses already circulating in Brazil, such as dengue (DENV), Zika (ZIKV) and chikungunya (CHIKV) viruses. The introduction of MAYV in other parts of Brazil may result in a public health concern, since the virus will find all favorable conditions in urban settings: high mosquito densities, poor sanitation and uncontrolled urbanization. Therefore, we conducted a study to test the vector competence of MAYV in the two most abundant mosquito species in Brazil:Aedes aegyptiandCulex quinquefasciatus. We used an animal model to analyze the dynamics between artificially-infected mosquitos and mice. We fed mosquito colonies with blood containing MAYV and on the 7thday post-infection (dpi), mice were made available as a blood source to both mosquito’s species. When these mice display signs of infection, a second blood feeding was performed with a new group of non-infected mosquitoes. We found thatAe. aegyptimosquitoes are very competent in transmitting MAYV, whileCx. quinquefasciatuspresented lower rates of infection and dissemination of the virus. All mice bitten by infectedAe. aegyptishowed clinical signs of infection. On the other hand, all mice exposed to infectedCx. quinquefasciatusmosquitoes remained healthy. We also found a higher viremia in animals bitten by infected-Ae. aegypti. Overall, our study showed the applicability of an efficient model to complete arbovirus transmission cycle studies and suggests that theAe. aegyptipopulation evaluated is a competent vector for MAYV highlighting the risk of establishment of MAYV urban cycle.