Vector competence and correlation of midgut microbiota of Aedes albopictus for Chikungunya virus

Abstract

Chikungunya virus (CHIKV) is an important mosquito-borne virus and transmission cycle of this virus involves mosquito vectors (Aedes albopictus and Aedes aegypti) and infected vertebrate hosts. The recently studies found that CHIKV outbreak in 2007 have been Ae. albopictus as an important vector which it was susceptible to genetic variation of CHIKV and induce to virus virulence. However, the study about vector competence for CHIKV in Thailand is limited. Moreover, the previous study indicates the impact of midgut microbiota of mosquito to viral infection. This study was conducted to examine the effects of CHIKV titers in blood meals on vector competence of Aedes albopictus (Diptera: Culicidae) and to investigate the correlation of midgut microbiota of Ae. albopictus. Six groups of Ae. albopictus were allowed to feed on different levels of CHIKV in the blood meals which were 106, 105, 104,103, 102 CID50/ml of CHIKV and the negative blood meal group. Body, legs and wings, and saliva samples from blood-fed mosquitoes were assayed for the presence of CHIKV by using immunocytochemistry staining on day 14 post blood feeding. Percent virus infection, dissemination, and transmission is defined as percent of blood-fed mosquitoes with virus in their bodies, legs and wings, and saliva, respectively. The percent infections were 83.3, 90, 100, 100, and 100%, the percent disseminations were 70.8, 86.7, 100, 90, and 98%, and the percent transmissions were 41.6, 70, 100, 90, and 82.4% after having been fed on 102, 103, 104, 105, 106 CID50/ml of CHIKV, respectively. This study suggested that Ae. albopictus are susceptible for CHIKV infection and efficient vectors for CHIKV transmission, and CHIKV titers in blood meals have effects on virus infection, dissemination, and transmission in Ae. albopictus or vector competence of this mosquito. For the bacterial isolation and identification, the midguts were cultured and 16s rRNA gene were analyzed followed by blast to gene bank database. The dominating bacterial genus was Micrococcus in infected mosquitoes after fed on CHIKV 102 CID50/ml, and it was significantly difference from the non-infected mosquitoes (P<0.04). In addition, Staphylococcus was the dominating bacterial genus in laboratory mosquitoes and it was significantly difference from field mosquitoes (P<0.0007). The correlation between midgut microbiota and CHIKV infection was not clearly indicated from this study.