Experts warn as Kala Zar-causing sand flies creep closer to homes

A boy with a Kala-azar infection.

The tiny sand flies that spread kala-azar are now biting people inside their homes.

This is a major shift from their previous habit of biting in remote grazing fields, Kenyan scientists have found.

Sand flies spread Visceral Leishmaniasis (VL), or kala-azar, a silent killer that begins with fever, followed by weakness and weight loss. It attacks the liver and spleen and can be fatal if not treated.

The disease mostly affected people in dry grazing fields and pastoral areas in northern Kenya.

However, scientists have discovered that the sand flies that spread kala-azar are changing habitats and now bite people inside their homes.

They said the habitat shift is driven by climate change and environmental disruption, complicating efforts to eliminate the disease by 2030.

Dr Daniel Masiga of the International Centre of Insect Physiology and Ecology (Icipe) said as the climate becomes hotter and rainfall patterns shift, new areas are becoming suitable for sand flies to live and reproduce.

This, he said, complicates efforts to eliminate the disease by 2030.

Masiga presented findings of his study titled “Visceral Leishmaniasis in East Africa: Insights from disease mapping” at the 16^th KEMRI Annual Scientific and Health Conference in Nairobi.

He said; “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 too dry to sustain large vector populations.”

Even more worrying is who is being infected.

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.”

Most past infections were linked to grazing fields, where herders spent long hours outdoors. Now, if children under four are getting infected, it means sand flies are biting near houses and in places where families gather in the evening.

This suggests that sand flies may be breeding in cracks in nearby soil, animal shelters or vegetation around homes. It also places families who are not pastoralists at risk.

Masiga said when a disease moves from distant grazing lands into compounds and homesteads, protection becomes harder and outbreaks can spread more quickly.

According to the Ministry of Health, over 3,500 cases occurred in 2025.

Endemic counties include Turkana, Wajir, Mandera, Marsabit, Baringo, West Pokot, Kitui, Machakos, Meru, Isiolo, Garissa and Tharaka Nithi.

Other scientific evidence from Kenya also supports Icipe’s warning.

A 2026 study titled “Mapping visceral leishmaniasis (also known as kala-azar) and examining environmental influences in Baringo county, Kenya” analysed five years of disease data alongside rainfall and temperature records.

The researchers found that mean monthly temperature and precipitation were significantly associated with kala-azar prevalence at sub-location level.

This means that when temperatures and rainfall changed, kala-azar cases also changed.

The study also identified four transmission hotspots in Baringo between 2019 and 2024, confirming that the disease is clustering in specific areas linked to environmental conditions.

The World Health Organization and Kenya’s Neglected Tropical Diseases Master Plan recognise this shift. The national plan states: “The disease foci in Kenya are changing to areas previously not known to be endemic as a result of climate change and population movements.”

The WHO notes that outbreaks of visceral leishmaniasis occur frequently in East Africa and that the region carries a large share of the global burden.

The organisation aims to eliminate kala-azar as a public health problem by 2030.

However, 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.”