While Tanzania's malaria prevalence rate has declined over the past few years, residents around Kilombero River Valley in the south are still vulnerable to the disease.

According to a study published in January’s edition of the Malaria Journal, mosquitoes carrying the little known malaria vector “anopheles funestus” exist in swarms in the valley.

"Further investigations could identify new opportunities for improved control of this dominant malaria vector, possibly by targeting the swarms," said researchers drawn mostly from the Ifakara Health Institute.

Swarm surveys for the study were concentrated on villages in two districts, Ulanga and Kilombero in Morogoro region.

The anopheles funestus vector contributes to at least 85 per cent of ongoing malaria transmission, even though it occurs in lower densities than other primary malaria-carrying vectors.

Tanzania has the third largest population in Africa at risk of contracting malaria, with over 90 per cent of its people said to be living in areas where the disease is still rampant.

Each year, 10 to 12 million people contract malaria in the country and 80,000 die from the disease, mostly children.

But according to the National Bureau of Statistics, malaria cases have dropped significantly in recent years.

Official figures released by the bureau slow that the prevalence rate dropped from 14.4 per cent in 2015 to 7.3 per cent in 2017, thanks to various control measures adopted by the Ministry of Health.

The authors of the IHI study say more intensive studies need to be conducted to map and characterise anopheles funestus swarms then figure out how to control them.

Unlike the other malaria vectors, the anopheles funestus populations are resistant to the pyrethroid insecticides commonly used on bed nets.

Such an approach could become a complementary tool used alongside existing interventions that include long-lasting insecticide-treated nets and indoor residual spraying to control malaria transmission, the study authors say.

The study recommends an anti-malaria approach that involves “suppressing mosquito populations by identifying and directly targeting anopheles swarms in general with highly effective insecticides before the mosquitoes enter houses."