08 November 2017

Biological warfare

In the USA, they will fight mosquitoes with the help of bacteria

Ksenia Malysheva, Naked Science

The US Federal Environmental Protection Agency has approved the use of bacteria to control mosquitoes – pathogens of dangerous diseases and vectors, in particular, the Zika virus, yellow fever and dengue fever.

On November 3, the biotech startup MosquitoMate received permission to use Wolbachia pipientis bacteria to fight Asian tiger mosquitoes (Aedes albopictus). Laboratory-grown insects infected with bacteria will be released in areas where wild mosquitoes are spreading.

There has been no official application for a permit, while an editorial in the journal Nature reports about it. According to the magazine, the document will allow MosquitoMate to release infected mosquitoes in 20 states and the District of Washington.

Before releasing infected mosquitoes into the wild, MosquitoMate employees will separate the females from the males. Only males who do not feed on mammalian blood will leave the walls of the laboratory. The female wild mosquitoes fertilized by them will lay eggs infected with bacteria. The W.pipientis bacterium does not kill an adult insect, but it interferes with the development of a fertilized egg, so there will be fewer mosquitoes in each next generation. For other insects, including other types of mosquitoes, bacteria are harmless, says entomologist Stephen Dobson, founder of the startup.

The restriction to 20 states and the District of Columbia is motivated by the fact that the average annual temperature and humidity in these states correspond to those at which the bacterial method of mosquito control was tested (testing was carried out in Kentucky, where the startup's office is located, New York and California). The permit does not apply to the south-east of the country, where the mosquito activity season lasts almost the whole year, and the populations are very large, because MosquitoMate has not tested its technique there yet.

In the coming months, the company plans to start selling infected male mosquitoes to land owners, golf course owners and other customers. The first batches will soon appear in Lexington, Kentucky, and a little later in Louisville, Kentucky and Cincinnati. The company will not be able to quickly achieve the large production volumes needed to effectively reduce the number of mosquito populations – production capacities do not allow it yet.

W. pipientis bacteria are already being used to control mosquitoes in China: There, scientists from Sun Yat-sen University in Guangzhou, with the support of entomologists from the University of Michigan, grow and release 5 million male mosquitoes infected with bacteria every week. Males are separated from females mechanically based on differences in weight and size. The remaining insects after sorting are subjected to X-ray treatment; the radiation dose is calculated so as to sterilize the females, but not to harm the males.

Previously, tests of genetically modified mosquitoes were conducted in Brazil, which have the same effect on the population: the mutation does not allow larvae hatched from eggs fertilized by GM insects to develop into a sexually mature individual; since 2015, this technique has been widely used to combat the spread of the Zika virus, which infects a person with a mosquito bite of the species Aedes aegypti. Zika virus is associated with fetal developmental defects such as microcephaly. Brazilian startup Oxitec tried to produce GM mosquitoes in the United States, but met resistance from the local population; in 2016, a referendum was held in Florida, in the Florida Keys settlement, according to the results of which testing of genetically modified insects was banned on the territory of the settlement. Unlike the Brazilian company, MosquitoMate has not attracted much public attention and has already tested A.aegypti infected in Florida and California; according to the results of the tests, the company expects to receive permission to use its products in all states.

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