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Cambodia & Health: 6th International Conference on Aedes Albopictus, the tiger mosquito

On 28 and 29 March 2024, at the Himawari Hotel Apartments, the Institut Pasteur du Cambodge will host the 6th International Conference on the Asian tiger mosquito Aedes albopictus.

Aedes albopictus, the tiger mosquito. Photo James Gathany, CDC
Aedes albopictus, the tiger mosquito. Photo James Gathany, CDC

The conference will be held under the chairmanship of His Excellency Professor Chheang Ra, Cambodian Minister of Health, and His Excellency Mr Jacques Pellet, French Ambassador to Cambodia.

Aedes albopictus, better known as the tiger mosquito, is one of the main vectors of Dengue fever, Chikungunya, Zika and at least 40 other major pathogens for public health.

This mosquito is native to tropical and subtropical areas of South-East Asia. However, over the last few centuries, this species has spread to many countries through the transport of goods and travel. It is characterised by white stripes on its legs and body.

This mosquito has become a significant pest in many communities because it lives close to humans and generally flies and feeds during the day, at dusk and dawn. The insect is called a tiger mosquito because of its striped appearance.

Scientists at the Institut Pasteur and Université Paris Cité have shown that this mosquito could acquire the ability to transmit the chikungunya virus just as effectively at 20°C as at 28°C. The spread of the tiger mosquito in temperate climates could therefore lead to the spread of the chikungunya virus in these regions.

The recent emergence of vector-borne diseases has marked a turning point in public health, as they now affect regions that are increasingly distant from endemic areas. The chikungunya virus was first reported in Europe in 2007 during an epidemic in Italy. The first native cases of chikungunya in the south of France were observed in the autumn, first in 2010, then in 2014 and 2017. The question of the effects of climate, and in particular temperature, on the transmission of pathogens by mosquitoes inevitably arises.

In this study, scientists from the Institut Pasteur and Université Paris Cité looked at the transmission of the chikungunya virus by the tiger mosquito Aedes albopictus at an ambient temperature of 20°C or 28°C. The minimum temperature recorded during recent epidemics in continental Europe was 20°C. 28°C is the average temperature in tropical countries where the virus usually circulates.

Using tiger mosquitoes taken from their natural habitat in Montpellier, the researchers analysed the adaptive molecular mechanisms induced by temperature.

"We have shown that temperature profoundly modifies gene expression and the bacterial microbiome of mosquitoes", explains Anna-Bella Failloux, head of the Arbovirus and Insect Vectors Unit at the Institut Pasteur and the latest author of the study. The scientists observed different gene expression profiles at 20°C and 28°C in mosquitoes infected with the virus.

In addition, the microbiome of mosquitoes infected with the chikungunya virus was modified at 28°C, with a significant decrease in Wolbachia bacteria correlated with an increase in Serratia bacteria contributing to viral transmission. Wolbachia bacteria inhibit viral replication, while Serratia bacteria promote infection of the mosquito's midgut by the virus.

Temperature also influences the viral genome of infected mosquitoes.

"The genetic diversity of the chikungunya virus has also been modified. All these changes lead to molecular modifications that result in efficient transmission of the pathogen", explains Anna-Bella Failloux.

"In this study, the Aedes albopictus mosquito was able to transmit chikungunya just as effectively at 20°C as at 28°C, but through very different molecular processes. This is a real example of mutual adjustment between the virus and the vector, in this case the tiger mosquito, in response to environmental conditions", adds the scientist.

The tiger mosquito is now present in temperate regions such as the American continent, temperate Asia and around 28 European countries, including France since 2004. In just a few decades, it has spread to four-fifths of France.

"Chikungunya is therefore likely to continue to spread in areas where the tiger mosquito is established. In the absence of vaccines and treatments, it could become a public health problem in a greater number of countries with a temperate climate", concludes Anna-Bella-Failloux.

At present, all the indigenous cases reported in mainland France come from imported cases and are not the result of an enzootic transmission cycle. In 2010, the imported cases involved two people who had just returned from Rajasthan, triggering a chain of transmission that led to the first indigenous cases reported in mainland France.

This international conference, held every two years, will highlight research topics on the Aedes albopictus mosquito species, such as bionomics, vector competence, invasion and dispersal patterns and its role as a transition vector, as well as new vector control strategies and the impact of climate change. Emphasis will also be placed on research conducted in Asia. The conference also aims to strengthen scientific collaboration.

The founders of this conference are Italian and Chinese collaborators from the Institut Pasteur du Cambodge, and meetings have been organised alternately between China (Guangzhou) and Italy (Pavia). Exceptionally, it was held in Montpellier, France, in 2022. This is the first time the event will be held in Cambodia, and the first time it will be organised by a team from the Pasteur network.

Source : Institut Pasteur


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