Abstract
BackgroundChikungunya virus (CHIKV) has emerged as one of the most important arboviruses of public health significance in the past decade. The virus is mainly maintained through human-mosquito-human cycle. Other routes of transmission and the mechanism of maintenance of the virus in nature are not clearly known. Vertical transmission may be a mechanism of sustaining the virus during inter-epidemic periods. Laboratory experiments were conducted to determine whether Aedes aegypti, a principal vector, is capable of vertically transmitting CHIKV or not.Methodology/Principal FindingsFemale Ae. aegypti were orally infected with a novel ECSA genotype of CHIKV in the 2nd gonotrophic cycle. On day 10 post infection, a non-infectious blood meal was provided to obtain another cycle of eggs. Larvae and adults developed from the eggs obtained following both infectious and non-infectious blood meal were tested for the presence of CHIKV specific RNA through real time RT-PCR. The results revealed that the larvae and adults developed from eggs derived from the infectious blood meal (2nd gonotrophic cycle) were negative for CHIKV RNA. However, the larvae and adults developed after subsequent non-infectious blood meal (3rd gonotrophic cycle) were positive with minimum filial infection rates of 28.2 (1∶35.5) and 20.2 (1∶49.5) respectively.Conclusion/SignificanceThis study is the first to confirm experimental vertical transmission of emerging novel ECSA genotype of CHIKV in Ae. aegypti from India, indicating the possibilities of occurrence of this phenomenon in nature. This evidence may have important consequence for survival of CHIKV during adverse climatic conditions and inter-epidemic periods.
Highlights
Chikungunya virus (CHIKV) is a mosquito-borne pathogen, native to Africa that is transmitted between non human primates, mainly by forest dwelling Aedes species
We speculated that the difference could be attributable to two factors:(i) the first batch of eggs is laid several days before virus has begun rapid replication after passing via the gut wall into the hemolymph, and/ or (ii) the enormous increase in the volume of the ovaries during oogenesis might increase its permeability to virus. We explored these possibilities by investigating the occurrence of vertical transmission in experimentally infected Ae. aegypti, the principal vector of CHIKV
Detection of CHIKV in parental females CHIKV RNA was detected in body, legs & wings of all the 10 randomly selected female Ae. aegypti that were provided with an infectious blood meal
Summary
Chikungunya virus (CHIKV) (genus Alphavirus, family Togaviridae) is a mosquito-borne pathogen, native to Africa that is transmitted between non human primates, mainly by forest dwelling Aedes species. The virus is widespread as an urban infection throughout the old world tropics and subtropics, transmitted by two species of mosquito- Aedes aegypti and Ae. albopictus, both closely associated with the human peridomestic environment [1]. Autochthonous cases have occurred in Europe, most notably in 2007 in an epidemic in northeast Italy that affected nearly 300 people [3] In this case the vector was Ae. albopictus, an invasive species that is rapidly expanding its distribution in Europe and is already present in at least 27 countries. Laboratory experiments were conducted to determine whether Aedes aegypti, a principal vector, is capable of vertically transmitting CHIKV or not
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