Planning for next release on Vietnamese island
In September 2013 we completed a release of wMelPop Wolbachia mosquitoes on Tri Nguyen Island, on the south central coast of Vietnam. We have been continuing to monitor mosquitoes on the island since then to see if Wolbachia has established in the local mosquito population.
While the Wolbachia rate initially reached a high level which was encouraging, recent results show there has been a decline in the number of mosquitoes on the island carrying Wolbachia, to below 20% of the mosquito population. This decrease suggests that the wMelPop Wolbachia will disappear from the mosquito population.
We believe this is because the wMelPop strain of Wolbachia, the strongest dengue blocking strain, causes mosquitoes to have a shorter lifespan and lay fewer eggs than the existing mosquitoes on the island. This means the wMelPop mosquitoes produce fewer offspring, making it difficult to compete with the local wild mosquitoes and for wMelPop to establish in the local mosquito population.
We now hope to undertake another trial on Tri Nguyen Island with a different strain of Wolbachia – wMel – that has successfully established in wild mosquito populations in various communities in northern Australia. Laboratory results from Vietnam’s National Institute of Hygiene and Epidemiology (NIHE) show that this strain of Wolbachia is suitable for the Island’s environment.
Further releases of Wolbachia mosquitoes would only proceed with community support and approval from the Ministry of Health. We hope to begin these releases in mid 2014.