KUALA LUMPUR: THE first “intersex” mosquito, known to be a vector for Japanese encephalitis, was found in Kuala Lipis, Pahang, recently.
It is believed that the discovery could pave the way for a novel bio-insecticide method in controlling the mosquito population.
The mosquito, from the Culex sitiens species, was discovered by researchers from Universiti Malaya’s Tropical Infectious Disease Research and Education Centre.
UM senior lecturer in vectors and vector-borne diseases Dr Low Van Lun said the mosquito exhibited gynandromorphism as it had male and female characteristics.
“Further investigation is required following the discovery as this mosquito can breed rapidly. A female mosquito can live up to four weeks. It will lay eggs up to three times, with 100 eggs each time,” he told the New Straits Times at the university yesterday.
Low, 32, said the mosquito was found by accident during surveillance in a rubber plantation in Kuala Lipis, Pahang on July 20.
“I was invited by Professor Datin Dr Indra Vythilingam from the university’s Faculty of Medicine to carry out Anopheles mosquito surveillance for malaria research in the peninsula last year.
“The project, which is ongoing, started in Johor in May.
“In Kuala Lipis, the first sampling was conducted in July,” he said, adding that Anopheles was a genus of mosquito and 460 of its species had been recognised; out of which 100 could transmit malaria in humans.
He said while waiting for Anopheles mosquitoes to feed on a human bait, one of the team members found a mosquito with unusual morphology on its leg.
The mosquito had unique characteristics, Low added, with a bushy antenna on the left side, a common trait for male mosquitoes.
“However, it was unusual as only female mosquitoes are attracted to human blood, which is required for egg production.”
He said the mosquito was caught and kept in a container.
“We tried to feed it by placing a mouse in the container to find out if it would suck blood. However, it refused to feed on it and died three days later.”
Low said the team brought the insect to a lab to study its morphology and that DNA barcoding to determine its species was done based on information from the National Centre for Biotechnology Information GenBank.
Low said it was important to study more on possible genetic alteration and other factors that could have led to the mutation.
“Based on my literature review, there are several factors that could have caused this. Biological changes could have happened at the larvae stage of the mosquito development.”
He said other possible factors included extreme temperatures (too high or too low), bacterial infections on the larvae as well as parasitic nematode infections.
“The intersex variation was also found in a black fly with nematode infections.
“We discovered this in a sample of black flies collected from water streams in Johor.”
He hoped to secure funding to enable him to look for more mutated Culex sitiens.
“This mosquito can fly up to 200m and its normal habitat is salt and brackish water.
“However, this mutated species was found in a rubber plantation, 100km from its usual habitat.”
He said ecological factors could have played a part in the discovery of the mosquito.
With talks on genetically-modified mosquitoes used to reduce the number of native disease-carrying mosquitoes having remained a contentious issue due to potential disruption to the ecosystem, Low said the discovery of the intersex mosquito in its natural setting could pave the way for an alternative solution in managing the mosquito population.
He said he was interested in studying insect vectors with medical-veterinary importance, such as mosquitoes, flies, ticks, fleas, lice and mites, as well as their associated infectious disease agents.