Scientists claim that Indian cattle seds may act as a 'shelter' for malaria-causing mosquitoes. They further said if the relationship between mosquitoes and cows is taken into account, it can even help in reducing the spread of the disease in the country.
"In many parts of the world, the mosquitoes responsible for transmitting malaria are specialist feeders on humans and often rest within human houses," said Matthew Thomas, professor at Pennsylvania State University in the US.
"We found that in an area of India that has a high burden of malaria, most of the mosquitoes that are known to transmit malaria rest in cattle sheds and feed on both cows and humans," said Thomas.
According to Jessica Waite, post-doctoral scholar at Penn State, cattle sheds are often next to and sometimes even connected by, a shared wall to human houses, yet current control efforts are restricted to domestic dwellings only.
"Given this cattle-shed 'refuge' for mosquitoes, focusing only on humans with regard to malaria control is a bit like treating the tip of an iceberg," said Waite.
The researchers determined the importance of cows in the malaria-control problem by capturing adult mosquitoes in different habitats within six villages in Odisha - which has the highest number of malaria cases in the country - and noting where the mosquitoes had been resting.The team then used molecular techniques to determine which species they were and which hosts they had been feeding on.
The scientists collected a total of 1,774 Anopheles culicifacies and 169 Anopheles fluviatilis mosquitoes across all study sites. They found that both species were denser in cattle shedsthan in human dwellings, and both were feeding on humans and cattle. Next, the researchers used their field-collected data tohelp build a computer model that simulated the life of anadult mosquito. They used the model to explore how best to control themosquitoes to have maximum impact on malaria transmission inthese villages.
"Our model analysis suggests that conventional controltools - such as insecticide-treated bed nets and indoorinsecticide sprays - are less effective when mosquitoesexhibit 'zoophilic' behaviours (having an attraction tononhuman animals)," said Thomas.
"However, extending controls to better target thezoophilic mosquitoes for example, by broadening coverage ofnon-repellant insecticide sprays to include cattle sheds couldhelp reduce transmission dramatically," said Thomas.
Waite added that the model suggests very littlecattle-based vector control effort would be required to drive malaria transmission in the region to elimination.
"We show that directing even modest amounts of effort tospecifically increase mosquito mortality associated withzoophilic behavior can shift the balance towards elimination,"she said. The findings appear in the journal Scientific Reports.