New evidence of project shows reduction of arbovirus diseases

Researchers of the World Mosquito Program (WMP) presented on 11/21 new evidence of the reduction of arbovirus-caused diseases in areas where Aedes aegypti with Wolbachia were released, in Brazil, Indonesia, Vietnam and Australia. Wolbachia is an intracellular bacterium that, once present inside mosquitoes, prevents dengue, zika and chikungunya viruses from developing within these insects, therefore reducing the transmission of the diseases. Preliminary WMP data, a global initiative led by Fiocruz in Brazil, point to a reduction of about 75% of the cases of chikungunya in Niterói (in the state of Rio de Janeiro) in the last two years, when comparing the areas of the city that received the mosquitoes with Wolbachia and the ones that did not. “We monitored data based on surveillance information of the Ministry of Health and, in the case of chikungunya, in this period of analysis we have identified this significant reduction”, stated Betina Durovni, epidemiology coordinator of WMP Brazil.

The data were presented by Fiocruz researcher and leader of WMP in Brazil, Luciano Moreira, during the Annual Meeting of the American Socity of Tropical Medicine and Hygiene (ASTMH), in the United States. The WMP Brazil has operated in Niterói and in Rio de Janeiro since 2016. As the Wolbachia Aedes aegypti were first released in Niterói, the early data now publicized are from this city. The data are preliminary and a full study with information on the two cities should be made public by 2022.

Data regarding WMP action in Indonesia, Vietnam and Australia were also presented at the ASTMH. The work of the World Mosquito Program in Indonesia involved the release of mosquitoes with Wolbachia in an area with about 65,000 inhabitantes near the city of Yogyakarta. The mosquitoes began to be released in 2016, 76% less cases of dengue fever were recorded among the target population by local health authorities, when compared with a control area nearby that did not receive the Wolbachia.
 

Katie Anders, researcher and epidemiology specialist of the WMP, showed the results of a field study carried out near Nha Trang, in Vietnam, where very few dengue fever cases were reported during the year following the release of Wolbachia mosquitoes. The mosquitoes were released in 2018. This low incidence of dengue fever cases in the intervention area was documented at a time in which the municipality of Nha Trang was facing one of its most serious dengue fever outbreaks.
 

Anders also presented the results published early this year, showing that in the extreme north of the state of Queensland, in Australia, the local transmission of dengue fever was interrupted. Wolbachia mosquitoes were first released eight years ago and led to a 96% reduction of the cases of local transmission of dengue fever.
 
“We are very excited about the impact on public health. This highlights the potential of the approach to fight dengue fever and mosquito-related diseases on a global scale”, emphasizes professor Cameron Simmons, director of impact assessment and WMP epidemiology expert. “Evidence shows that in areas where Wolbachia mosquitoes were released there are less reports of dengue fever than in non-treated areas”.
 
WMP researchers emphasize that mosquito releases are always preceded by engaging actions to inform local communities on the safety of Wolbachia bacteria and their impact on the ecosystem. The WMP’s Wolbachia Method involves no genetic modification, neither in the bacterium nor in the mosquito. Wolbachia is naturally present in most insects, but it is not found in Aedes aegypti mosquitoes, the vectors of dengue fever, chikungunya and zika, all belonging to a class of virus called arboviruses.
 
“This is a very encouraging work, done in the midst of an explosion of dengue fever infections that health authorities are finding very difficult to control”, said the president of the American Society of Tropical Medicine and Hygiene, Chandy C. John. “The combination of advanced science and community involvement and commitment is impressive, and essential for its success”.

Existing evidence on the reduction of dengue fever related to Wolbachia mosquitoes are consistent with the predictions made in previously published modelling studies. “We are very excited with the fact that this self-sustainable and cheap method has been adopted by the communities and is offering the public health benefits we were expecting”, said Simmons, WMP director. “Our challenge now is working with partners and governments to take the method to 100 million people by 2023”.
 
WMP Brazil
The World Mosquito Program has been developing activities in Brazil since 2012, when it was called “Eliminating Dengue Fever: Brazil Challenge”. Between August 2015 and January 2016, the project released Aedes aegypti with Wolbachia in two pilot areas: Tubiacanga, in Ilha do Governador, Rio de Janeiro, and Jurujuba, a neighbourhood in the city of Niterói. Wolbachia has already been established in this area. Since 2016, the program has been extended to include other neighbourhoods of these two cities.
 
In April 2019, with the support of the Ministry of Health, the WMP announced the expansion of the program to three new municipalities: Campo Grande (state of Mato Grosso do Sul), Petrolina (state of Pernambuco), and Belo Horizonte (state of Minas Gerais). The first releases of Wolbachia mosquitoes in these cities are expected to take place in the first semester of 2020.