Have more cows, keep mosquitoes away: Experts

via Pioneer News Service | Alappuzha published on April 26, 2008

Cows can save human beings form mosquitoes. This is the revelation of a study conducted by a team of experts of the National Institute of Communicable Diseases, Delhi.

The study by a team headed by the institute Joint Director, Rajendran reached a conclusion that decrease in the number of cows had caused an increase in the density of mosquitoes in Kerala. Certain mosquito species had some sort of an affinity to the blood of cows, says the study. These mosquitoes, categorised as Zoophilic and Aviphilic, like cows’ blood than that of human beings, it said.

Dr Rajenderan said that the Vishnoy group mosquitoes were Zoophilic and these preferred the blood of animals, especially of cows. Vishnoy, Psudovishnoy and Tritinio Rhynchus mosquitoes belonged to the Zoophilic group.

Aviphilic group of mosquitoes suck blood of birds, especially of water birds. Mansonia mosquito, which was regarded as the career of filaria virus earlier, was later proved to be carriers of Japanese encephalitis strands also.

These mosquitoes are divided into three categories: Unifiorunis, Annulifera and Indiana.

Of these three, Unifiorunis are known to be Zoophilic, while Annulifera likes to suck human blood. But, the Indiana species likes both types of blood. These three categories of mosquitoes are carriers of the virus of Japanese Encephalitis. Zoophilic mosquitoes were more lethal than other species that like blood of cows, Dr Rajendran said.

“Thus mosquitoes can be avoided from the house, if there is a cow,” Dr Rajendran said. “If there is no cow, mosquitoes could target human beings for sucking blood. As far as a cow is concerned, the virus that gets into its body system with mosquito-bite would be ruined, because all viruses were not capable of living long in the system of cows,” he said.

Dr Rajendran said that there was a tendency among mosquitoes to be ‘revengeful’ when all avenues for getting food were closed. He said that a mosquito-eradication programme conducted in Thiruvananthapuram city in 1996 was a best example for it. The Thiruvananthapuram Corporation had conducted a comprehensive programme of cleaning all drainage systems in the city. It was done in a day, but in the evening denizens were seen running helter-skelter, because mosquitoes had begun targeting houses, attacking human beings.

The scientist felt that if there were enough ‘substitute apparatuses’ like cows in the city, mosquitoes would not have attacked public. “There has been a steep fall in the number of cows in Kerala. This might cause a big problem. Do something to increase in the number of cows and human beings would benefit out of it,” he said.

Similarly, keeping paddy fields as wastelands had also caused an increase in the spread mosquitoes all over Kerala, he said. Earlier, presence of mansonia mosquitoes used to be reported only from areas between Kollam and Ponnani. “Today, mansonia mosquitoes are seen everywhere in the State – from Thiruvananthapuram to Kasaragod,” Rajendran said.

Plants of paddy keep mosquitoes in the fields and fishes and other aqua creatures eat the pupa of mosquitoes, he said. As the area of wasted paddy fields are increasing, a corresponding increase in the number of mosquitoes is seen, said Dr Rajendran.

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