A recent study led by scientists from Ifakara Health Institute has found that communities engaging in livestock-keeping face a higher risk of malaria both indoors and outdoors compared to those without livestock.

Published on the Malaria Journal, the study suggests that communities with livestock – such as cattle, sheep, goats, and chicken – experience a higher incidence of malaria due to the increased presence of malaria-carrying mosquitoes both indoors and outdoors. The study assessed the impact of livestock management on malaria transmission risks in rural Tanzania.

Increased mosquito density linked to livestock
Conducted in the rural setting of Minepa village in Ulanga district, Kilombero Valley, southeastern Tanzania, between 2022 and 2023, the study found that the increase in mosquito density in homes with livestock is linked to livestock odors and the availability of alternative blood meals from animals, which attract mosquitoes.

"In this study, the number of resting mosquitoes in houses with livestock was much higher than in houses without livestock both indoors and outdoors. This correlates with the results of host-seeking mosquitoes, where Anopheles mosquitoes were higher in households with livestock," the scientists noted.

Impact of livestock on malaria intervention strategies
Tanzania has one of the largest livestock numbers in sub-Saharan Africa, and livestock is one of the economic activities that play an important role in poverty alleviation, food security enhancement, employment creation, and environmental conservation, particularly, in village settings. 

While it has been suggested that livestock could help control malaria by diverting mosquitoes away from people – an intervention known as zooprophylaxis – the effectiveness of this livestock-based malaria intervention remains debatable, with studies showing mixed results. 

Zooprophylaxis, a potential risk rather than benefit
This study also revealed similar results, with scientists concluding that rather than mitigating malaria risk, zooprophylaxis may intensify it after findings showed that the presence of livestock attracts more mosquitoes or creates conditions that support larger mosquito populations, leading to increased malaria transmission rates.

For example, they found mosquito species like An. gambiae s.l. preferred feeding on cattle (71.6%) in homes with livestock, whereas in homes without livestock, mosquitoes preferred feeding on humans (67.3%).

Influence of livestock, home design on mosquito density
Other factors, such as the distance between livestock sheds and homes, generally did not significantly affect mosquito density indoors, except for the An. Coustani species, which decreased when livestock were kept 11 to 20 meters away. Additionally, homes with mud walls and thatched roofs had higher mosquito densities compared to those with brick walls and iron roofs. Residents also reported more mosquitoes near homes with livestock and noted that early evening outdoor activities exposed them to more mosquito bites. 

Call for integrated, livestock-based interventions
In light of these findings, the scientists are calling for immediate and targeted interventions to control mosquito populations in livestock-keeping areas. 

They recommend integrated control measures, including livestock-based interventions such as spraying animals with insecticides, raising awareness, and educating communities about the impact of livestock on malaria transmission. More research is also needed on mosquito behavior in livestock-keeping communities and the effects of different distances between homes and livestock pens.

Ifakara scientists lead the study
Ifakara Health Institute scientist Yohana Mwalugelo led this study as part of his MSc research. Mwalugelo collaborated with his colleagues Winifrida Mponzi, Letus Muyaga, Herieth Mahenge, Godfrey Katusi, and Emmanel Kaindoa, also from Ifakara. 

Additional contributors include Faith Muhonja from Amref International University in Kenya, and Dickens Omondi, Alfred Ochieng, and Fred Amimo from Jaramogi Oginga Odinga University of Science and Technology in Kenya.

Read the publication here.