As human continually advance its efforts to combat the dengue virus, mosquito vectors are also evolving, posing new challenges in the control of the disease.
Theoretically, Aedes aegypti mosquito acquires dengue virus by sucking infected blood from human. But this could be changed because dengue virus can now pass by an adult mosquito to its offspring.
In the study Natural Transovarial Transmission (TOT) of Dengue Virus in Aedesaegypti conducted by the researchers from the University of San Carlos – Talumban Campus in Cebu City confirmed that Aedes aegypti mosquitoes are capable of transferring dengue virus biologically to its offspring.
Dr. Frances Edillo, biology professor and proponent of the study, collected mosquito larvae and pupae in Barangay Babag, Basak San Nicolas, Pasil and Barangay Poblacion Pardo, among the barangays with the highest dengue incidence in Cebu City, to determine the occurrence of transovarial transmission (TOT) of dengue virus (the mosquitoes’ ability to transfer dengue virus to its offspring) and to identify the strains of dengue virus infecting mosquitoes in Cebu City.
Larvae and pupae were gathered monthly from the natural mosquito habitats like plant leaf axils, plastic containers, drums, water reservoirs, bamboo stumps and other mosquito habitats. Larvae and pupae were reared in laboratory until they become adults.
In the process, the researchers extracted ribonucleic acid (RNA) from mosquito samples and subjected to laboratory tests and analysis. Results showed that out of 2,871 individual mosquitoes (171 pools), 679 (62 pools) are positive with dengue virus. Most of the dengue strains identified were dengue 4 (DENV-4), followed by dengue 3 (DENV-3) and dengue 1 (DENV-1), respectively. There were no dengue 2 (DENV-2) strains detected by the study.
The study emphasized that dengue virus were detected in different life’s stages of an Aedes aegypti mosquito, including larva, pupa and in both male and female adult mosquitoes.
According to Dr. Edillo, the occurrence of dengue virus in mosquito larvae and pupae would lead to re-emergence of the disease in previously infected community. Thus, by detecting dengue virus at early stages would be an important strategy in monitoring and surveillance of dengue infection in the community.