Warsito Tantowijoyo (World Mosquito Program)
Wolbachia establishment/spread and its impact on insecticide resistance

Warsito Tantowijoyo delivered a detailed and insightful presentation on the Wolbachia establishment/spread and its impact on insecticide resistance. He detailed the timeline of studies, in 2014 a small scale release then in 2015 an impact study then in 2021 an implementation study. The small scale release study aimed to demonstrate the feasibility of establishing Wolbachia in a disease endemic setting. He emphasised the importance of community acceptance levels being high to the small scale release and how safe Wolbachia is for humans and the environment. In order to heighten this feeling of safety, the research team collected mosquito eggs constantly and tested them in the lab for evidence on the increase in Wolbachia composition. This was a strategy to provide evidence and proof to the community of how the project is seeing success and they can trust it further. An interesting observation that no Wolbachia has been detected in humans. Warsito Tantowijoyo indicated that the fitness of the mosquito is crucial for the Wolbachia to be passed to the next generation. He reminded us that Wolbachia has been maintained in the field of Indonesia for seven years. Multiple studies are continually being conducted to measure the Wolbachia composition in mosquitoes and access the effectiveness of the program. To close, Warsit Tantowijoyo presented a useful visual of a heatmap which indicates the Wolbachia status and is coloured to highlight the % of dengue reduction in different areas in Indonesia.

Riris Andono Ahmad (World Mosquito Program Yogyakarta)
Public health impact of Wolbachia intervention in Yogyakarta

In his insightful presentation about the public health impact of Wolbachia intervention in Yogyakarta, Riris Andono Ahmad emphasised the result in the impact study of Wolbachia in the phase 3. It was a long study, however it has a very impressive result. The study itself was conducted in 24 contagious areas in Yogyakarta city and was started in 2016 when the first community engagement was also implemented. Results from the study vary in some variables, but again, the result is promising. Effect on the efficacy of the study is 77% reduced incidence in Yogyakarta. This result is comparable with the dengue vaccine available nowadays. Using the quasi-control study, the cases in the control areas are higher than the intervention area. Another result after the intervention is the insecticide fogging activity is lower in the treated area compared to the untreated area. This is because the community in the treated areas are aware of the vector control regulation. As we speak about the vector control, there is no difference after the intervention of Wolbachia. Another result, such as impact of Wolbachia in case of fatality rate in DHF, the study found there some increasing part, but this due to reduction of the denominator.

Kat Edenborough (Monash University)
Evolution; implications on Wolbachia

Kat Edenborough delivered a detailed and insightful presentation on the evolution and implications for Wolbachia. She began by stating the unknown of the durability of protection, which is likely to be influenced by evolution stability. She progressed to get technical and explained that the Wolbacia gene is 1.3Mb and genome snippet size indicates the level of diversity in the genes of the mosquitoes. She expressed the observations of Cairns, Australia and that despite a large number of travel infections coming in each year there has been only a small number of breakthrough infections of dengue. The dengue virus genome has four serotypes and several genotypes and geography has a great impact on the diversity which Kat Edenborough indicates is the major complexities of the studies as diversity is based on location. He also emphasises that DENV evidence is an obvious risk to the evolution of dengue and Wolbachia project outcomes and investigating DENV evolution and resistance risk is crucial. She found the function of one mutation might be found in future compounds and the envelope protein changes in this position may impact infusion threshold. The point was made that variants might not survive the human-mosquito transmission cycle if unfit in one host and it is very important to conduct these studies to compare the genotypes/sequences between baseline and prospective samples: small sample sizes, imported sequences and transmission chains are rare. She concluded by remarking about genotype level efficiency, diverse linkages in Yogyakarta, there are biases towards lineage sharing between Yogyakarta, China, Taiwan, Singapore and elsewhere in Indonesia. Kat Edenborough provided such important insight into the evolutions and genetics of this project.