Climate change and shifting ecological patterns are helping push a deadly parasitic disease into new parts of East Africa, scientists say, complicating efforts to eliminate it by 2030.
Visceral leishmaniasis, also known as Kala-azar, is transmitted by sand flies and is often fatal if untreated. While the disease has long affected parts of Kenya, Uganda, Sudan, South Sudan and Ethiopia, researchers now report that cases are appearing in counties not previously considered endemic.
According to Dr Daniel Masiga of the International Centre of Insect Physiology and Ecology (ICIPE), East Africa is now the global epicenter of Kala-azar and we are seeing transmission patterns that are shifting.
Presenting on the study titled Visceral Leishmaniasis in East Africa: Insights from disease mapping ’ at the 16th KEMRI Annual Scientific and Health Conference in Nairobi, Dr Masiga’s findings suggest that ecological changes including land use, settlement expansion and environmental degradation combined with climate variability are altering where sand flies can survive and breed.
“Rising temperatures and changing rainfall patterns can expand suitable habitats for the insects, increasing the risk of transmission in areas that were previously too cool or dry to sustain large vector populations,” he said.
The disease remains geographically clustered, but Dr Masiga say new hotspots are emerging. In Kenya, cases are being reported in counties that historically recorded little or no transmission.
Children and adolescents are bearing the greatest burden. Most cases occur in individuals under 19 years old. In some areas, including Wajir and Kajiado counties, infections have been detected in children younger than four.
“That tells us transmission is happening close to homesteads,” Masiga said. “It is not just associated with grazing fields or traditional pastoral movement.”
In East Africa, sand flies often bite outdoors, limiting the effectiveness of indoor insecticide spraying strategies that proved successful in parts of Southeast Asia.
That ecological difference means control strategies cannot simply be replicated from other regions.
The World Health Organization and affected countries have set a target to eliminate kala-azar as a public health problem by 2030. But scientists say climate-driven changes in vector distribution could make that goal more difficult without stronger surveillance systems.
Dr Masiga called for increased county-level involvement in monitoring cases, expanded studies on sand fly biology and ecology, and improved disease modelling to help governments target interventions where risk is highest.
“As the climate changes, disease patterns change,” Masiga said. “We must adapt our surveillance and control strategies to match that reality.”
Visceral leishmaniasis attacks internal organs including the spleen and liver, causing prolonged fever, weight loss and severe anemia. Without treatment, it can be fatal.
The study warn that unless climate-sensitive surveillance and locally tailored interventions are strengthened, East Africa’s status as the global epicentre of kala-azar could persist or expand in the years ahead.
