Vector competence of Aedes aegypti populations from central Argentina for Mayaro virus (Alphavirus)

Abstract

Abstract: 

In recent decades, diseases caused by arboviruses have increased their global distribution and incidence on the human population. The Mayaro virus (MAYV) endemic of South and Central America, is causal agent of polyarthritis diseases. In urban regions MAYV could be transmitted by Aedes aegypti. Vector competence is the ability of a mosquito population to become infected by feeding on a viremic host and transmitting it to a susceptible host. The aim of this study was to evaluate the susceptibility to infection and transmission by MAYV in populations of Ae. aegypti from Córdoba and Buenos Aires cities. Eggs were collected in the before mentioned cities and colonies were established in the Arbovirus Laboratory facilities (InViV). Five to 7 days old mosquito females were exposed orally with five viral load ranging 1.9 to 5.8 log10 PFU/ml. Fully engorged females were apart and kept at 27oC, 70% humidity and 12:12 photoperiod during 9 days. Abdomens, legs and salivary secretion were extracted for presence of infective viral particles by means of plaquing assay on Vero cell monolayers. The infection rate (IR = number of mosquitoes with presence of MAYV in abdomen/number of mosquitoes analyzed), dissemination rate (DR = number of mosquitoes with presence of MAYV on legs/number of mosquitoes analyzed) and transmission rate (TR = number of mosquitoes with presence of MAYV in saliva/number of mosquitoes analyzed) were estimated for each population. Córdoba population showed IR between 3.1% and 22.2% with viral load of 4.7 to 5.2 log10 PFU/ml, respectively. In Buenos Aires population the IR were 5.3% to 41.2% with viral loads of 3.8 to 5.8 log10 PFU/ml, respectively. TR was 4% (Córdoba) and 5.8% (Buenos Aires) only in individuals exposed with the highest viral load. Our results show that Ae. aegypti populations from the main urban cities of Argentina do not have a high susceptibility to infection by MAYV and only transmit the virus in a small proportion at high viral loads.