Climate change and visceral leishmaniasis in North Eastern Kenya
An epidemic of visceral leishmaniasis (Kala-azar) occurred in the North Eastern Province (NEP) of Kenya in 2001 and 2002. This appeared to have been triggered by an exceptionally heavy rainfall associated with the El Nino Southern Oscillation (ENSO) which took place between October 1997 and February 1998. The high rainfall also triggered epidemics of malaria and Rift Valley Fever in a predominantly arid and semi-arid region bordering Somalia and Ethiopia during the same period of heavy rain. Before 2001 Kala-azar was a rare disease in NEP, and had never reached epidemic proportions. The study aimed at exploring the relationship between the epidemic of Kala-azar and heavy rainfall associated with ENSO.
Methodology
Following reports of cases suggestive of Kala-azar from local hospitals in NEP a series of surveys and active case detection, diagnosis and treatment were conducted in NEP. Screening was carried out based on the clinical manifestation and confirmatory diagnosis was arrived at parasitologically by demonstration of Leishmania amastigotes in splenic aspirates. This was necessary before commencement of treatment in local hospitals.
Phlebotomine sandflies were collected from villages suspected to be foci of infection by means of light traps and by hand capture using aspirators from ant hills. Identification of sandflies was carried out using morphological characters. Meteorological data was collected for the region.
Results
301 cases of Kala-azar were confirmed from several foci predominantly in Wajir, and several from Mandersa and Garissa Counties of NEP. Most of the foci of transmission were villages in Wajir County, such as Wajir Bor, Gorof Harar, Kutulo and Tarbaj. Others were in Mandera, which included Ramu, Lafey and El Wak villages. In Garissa the cases were restricted almost exclusively to Dadaab refugee camp harbouring refugees mainly from Somalia. The disease affected all age groups throughout NEP and in Dadaab refugee camp. Phlebotomus martini and P. celiae were the only sand flies of the genus Phlebotomus collected. Meteorological data showed a definite peak coinciding with the period of ENSO and compared favorably with the chronic nature and the normal incubation period of Kala-azar.
Conclusion
The current epidemic occurred in new previously undescribed foci of visceral leishmaniasis in North Eastern province, Kenya in 2001 and 2002. The epidemic which was preceded by other more acute epidemics due to malaria and Rift Valley fever appears to have been precipitated by high rainfall owing to the El Nino Southern Oscillation (ENSO) that occurred in 1997/1998. ENSO was therefore considered to be a predictor for Kala-azar. The vector of Kala-zar in NEP appeared to be Phlebotomus martini, a proven vector of this disease in other endemic areas of Kenya.