Scientists in French Polynesia on verge of mosquito breakthrough

Transcript

Scientists in French Polynesia say an ambitious experiment to control mosquito populations is proving to be very successful, and could change the way countries prevent mosquito-borne illness.

Hervé Bossin, and his team from Institut Louis Malardé, the territory's public research institute, have released sterilised Polynesian Tiger Mosquitos on the atoll of Tetiaroa to try and prevent breeding.

He says that in six months, Tetiaroa, the private island of the late Hollywood star Marlon Brando, has seen its mosquito population drop dramatically. 

He told Jamie Tahana that if successful, the process could become one of the most effective ways for Pacific countries fight against diseases like dengue fever, chikungunya, and Zika Virus.

HERVÉ BOSSIN: The mosquito project that is happening right now, it's a trial that seeks for the suppression of one of the very important disease mosquito vectors in the Pacific islands, it's called the Polynesian Tiger Mosquito -- latin name Aedes Polynesiensis --It is a major vector for lymphatic filariasis and other diseases such as dengue, obviously Zika and chikungunya that have recently affected the Pacific region. This moquito is apparent in most populated islands of French Polynesia and also it goes all over from Samoa, Fiji, Cook Islands and all the way to Pitcairns on the eastern end of the polynesian triangle, and so we have developed innovative strategy to try to better control this mosquito which is otherwise very difficult to control using conventional methods and tools for mosquito vector control. 

JAMIE TAHANA: So these conventional methods, they are the programmes that are on right now of clearing water areas and spraying and stuff isn't it? Are they quite ineffective?

HB: So what we need to know about Aedes Polynesiensis; it is a mosquito vector that is essentially present in sub-urban areas, the natural forests, rural areas and so it is difficult to control because there is a number of natural breeding sites that this mosquito breeds in and that includes coconuts that are chewed by rats, holes in trees, that you would have a very difficult time getting rid of, and they are also present in numerous areas where we don't essentially live and it would be very difficult to manage in terms of, you know, environmental management. And so it is unlikely also that you will be spraying in these natural areas where the mosquito is thriving.

JT: And so this experiment, what are you trying to do to be able to get this mosquito?

HB: We have developed a very innovative approach which can be integrated to existing tools it is based on basically sterilising male mosquitoes. What you need to know is that male mosquitoes, unlike female mosquitoes, they don't bite and they are not the source of any nuisance. They don't transmit diseases so you can essentially release as many as you want and that will not cause any nuisance around where we are present. We are using a biological approach that is based on the use of the tiny bacteria called Wolbachia. Wolbachia is present in a number of insect species including butterflies honey bees and a number of mosquito species as well and we are harnessing the properties from these small bacteria for the purpose of our innovative vector control strategy. Essentially because Wolbachia is present under different strains and different species, different strains of Wolbachia don't do well together in a different species so when a male and a female carry different wolbachia strains and when they mate the result of the mating is not compatible. In other words the male strain of wolbachia that we have developed in the colony in the lab is going to sterilise the female. This female will lay eggs that will never hatch as a result of the incompatibility between the two wolbachia strains in the embryo.

JT: Ok so it is pretty much a biological approach to clear out populations of mosquitoes?

HB: Yes so the mosquitoes we are releasing their genome their genes have not been modified in any ways and the wolbachia bacteria that we are using in this mosquito is neither modified is not genetically transformed in anyway. So it is a very natural approach. So it has shown to be very efficient so far, we have started to release on Tetiaroa since September of last year and we have observed the gradual suppression and collapse of the treated area, you know the treated mosquito population that we are targeting in Tetiaroa 

JT: And how long does it take for that target population to collapse, is it say if there is a outbreak of something, how quickly would it work?

HB: We started the release in september just before the start of the rainy season when the population of mosquitoes is at its lowest and so that helped us with the production and the releases we were facing a lower number of mosquitoes to begin with which is strategically better. It took about just a few weeks, four to six weeks to start to see the start of the collapse of the targeted mosquito population. And we have maintained the releases for that number a month because there is a number of eggs that are present it is like an egg bank that are naturally present and we are waiting for those eggs to hatch as a result of the rainfall and so that they can emerge as adults and the females can sterilsed and we need to deplete this egg bank before we can claim for succesful elimination in the motu.

JT: Ok so it is quite effective from what you have done so far?

HB: It has been very effective we are really, really happy with the outcome of the program so far. The program will continue until the end of 2016. We will probably end the releases maybe sometime in May or July depending on the outcome and the results we get from the monitoring of mosquitoes we do on a regular basis. Depending on what we see in terms of mosquito recovery in our traps and there is very few today coming into our traps, there are very few remaining in the field. And we will monitor those mosquitoes for a period of time to determine how sustainable the whole approach is.