Vector Status and Transovarial Transmission of Chikungunya Virus (CHIKV) and Dengue Virus (DENV)in Aedes mosquitoes in Kampung Pulau Salak and Kampung Tanjong Bako, Sarawak. Master thesis

Cindy, Tan Siew Ching (2022) Vector Status and Transovarial Transmission of Chikungunya Virus (CHIKV) and Dengue Virus (DENV)in Aedes mosquitoes in Kampung Pulau Salak and Kampung Tanjong Bako, Sarawak. Master thesis. Masters thesis, Universiti Malaysia Sarawak.

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Abstract

Chikungunya virus (CHIKV) and dengue virus (DENV) are vector-borne viruses which can be transmitted through vector mosquitoes, Ae. aegypti and Ae. albopictus. Pulau Salak in Sarawak is one of those areas affected by chikungunya outbreak in 2009. Thus, this study was conducted to determine the vector status and transovarial transmission of CHIKV in Aedes mosquitoes on Kampung Pulau Salak, Kuching, Sarawak, since it is one of the areas which was affected due to the outbreak of CHIKV. The process of detection of DENV was carried out on the mosquitoes as well. The research was carried out at Kampung Pulau Salak and Kampung Tanjong Bako, Kuching in which Kampung Tanjong Bako act as a negative control site in this study. Mosquito larvae were collected from ovitraps and discarded receptacles before being reared in the laboratory for emergence of adults while adult mosquitoes were sampled by using bare-leg catch method (BLC) with the help of mechanical aspirators. A total of 7834 Aedes mosquitoes were pooled according to species, sex and sampling location. The ovitrap index recorded on Kampung Pulau Salak was 84.3%, 96.7%, and 89.3% for the first, second and third sampling respectively. On the other hand, the ovitrap index recorded in Kampung Tanjong Bako was 67.6%, 50.0%, and 87.1% for the first, second and third sampling respectively. There was no significant difference (p > 0.05) of ovitrap indexes between Kampung Pulau Salak and Kampung Tanjong Bako. The highest number of species of mosquitoes collected in Kampung Pulau Salak was Ae. albopictus (90.07%) followed by Ae. aegypti (6.02%), Culex sp. (2.63%), and Armigeres sp. (1.28%) while the highest number of species of mosquitoes collected in Kampung Tanjong Bako was Ae. albopictus (99.93%) followed by Ae. aegypti (0.07%). RNA extraction and two-step Reverse Transcription Polymerase Chain Reaction (RT-PCR) were performed to detect CHIKV and DENV from the samples collected. There were 223 pools of Aedes mosquitoes tested for the presence of the viruses. Chikungunya virus of East Central South African genotypes were detected in one pool of male and one pool of female (n=35) emerged Aedes albopictus mosquitoes collected from the ovitraps in Kampung Pulau Salak. DENV of serotype 2 was detected in one pool of male and two female pools (n=35) of emerged Aedes albopictus collected from Kampung Pulau Salak as well. There was no presence of CHIKV and DENV detected in the emerged Aedes mosquitoes collected from Kampung Tanjong Bako. None of the field-caught Aedes mosquitoes collected from Kampung Pulau Salak and Kampung Tanjong Bako were detected with CHIKV and DENV as well. The findings of this study showed evidence of transovarial transmission of CHIKV and DENV in Aedes mosquitoes in Kampung Pulau Salak. This finding may contribute to the effort in controlling the vector of CHIKV and DENV in the island as the status of the vector is currently unknown.

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