Jury Still Out on Whether New Mosquito Carries Malaria




A new species of mosquito has been discovered by South African researchers, adding to the pantheon of some 140 species of Anopheles mosquitoes in Africa, of which seven are known to be malaria vectors.

"A lot of Africa's mosquitoes are not investigated - the Democratic Republic of Congo (DRC) is a huge blank in the map. Who knows what is happening in the remote regions of the Rift Valley?" said Prof Maureen Coetzee, of the University of the Witwatersrand's School of Pathology in Johannesburg, South Africa, who discovered the new species.

Coetzee is one of the authors of the report: A New Species Concealed by Anopheles funestus Giles, a Major Malaria Vector in Africa. "Understanding the vectors is absolutely key; if we don't do anything about mosquitoes, we will never do anything about malaria," she told IRIN.

The previously unknown species - provisionally named Anopheles funestus-like - was discovered during field studies by researchers from the university and South Africa's National Institute for Communicable Diseases in and around rural villages in northern Malawi near the town of Karonga, on the western shore of Lake Malawi.

The new species is related to the major African malarial vector, Anopheles funestus, but the "jury is still out on ... whether it carries [the] malaria [parasite]," Coetzee said. The Anopheles funestus Giles group of mosquitoes has nine known African species, and "although the members of the Anopheles funestus group may be similar in morphology [its form and structure], their efficiencies as malaria vectors vary greatly," the report said.

Anopheles funestus s.s. is recognized as one of the primary causes of malaria in sub-Saharan Africa because it is anthropophilic, meaning that it prefers to feed on humans rather than other animals, and endophilic, meaning it associates with humans and their domestic environment.

While "anopheles rivulum has only once been implicated in malaria transmission in Tanzania, it generally elects to blood-feed on domestic animals rather than humans," the report said.

The new species were "common inside houses [which] makes them potential [malaria] vectors", the researchers found, "although none of the 61 specimens examined for malaria parasite infection during this study were positive for Plasmodium Falciparum, [the parasite that causes malaria in humans]."

Coetzee said it was important to ascertain whether Anopheles funestus-like was a malaria vector or not, but this could only be determined after further research.

If it did not carry malaria it would be unnecessary to spend money on disease containments like spraying; if it did, strategies should be developed to limit its impact.

"Using the unique mosquito breeding facilities at the National Institute for Communicable Diseases [in Johannesburg], we were able to carry out a range of experiments to show that the mosquitoes from Malawi were not the same as Anopheles funestus, and that we were dealing with a species new to science," Coetzee said in a statement on September 1, 2009 announcing the breakthrough.

Donít know as much as we thought we did

"The results have implications for malaria-vector control, particularly any attempt to use genetically modified mosquitoes. They also demonstrate how little we know about the malaria mosquito vectors in Africa despite over 100 years of research into this important disease."

Nobel Prize winner Sir Ronald Ross, working in Secunderabad, near Hyderabad in Andhra Pradesh State, India, scientifically proved in 1897 that mosquitoes carried the parasite that caused malaria.

Coetzee remarked, "Here we are in 2009, discovering a new species [of mosquito] - it really is quite remarkable. The more we look, the more we will find; we might think that we know an awful lot [about mosquitoes and malaria], but there is a lot to learn."

The incidence of drug-resistant malaria in Cambodia was "causing worldwide panic", she said, but there were differences between Asian and African mosquitoes - "African vectors are very good [at transmitting malaria]."

According to the World Malaria report for 2008 by the UN World Health Organization, half the world's population is at risk, and an estimated 247 million cases led to nearly one million deaths in 2006. Pregnant women and children in sub-Saharan Africa are especially threatened.

© IRIN. All rights reserved.



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