Publication: Resurgence of Visceral and Cutaneous Leishmaniasis in Kajiado County, Kenya: A Coordinated Response and Entomological Survey.
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2025
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We obtained support for this study from the Kenya National Research Fund (DKM, DMM, RW and JW), the AntiVec grant (AV/PP0018/1; JV & DMM), the German Academic Exchange Service (DAAD) grant (91843264; BOO), and the US National Institutes of Health, NIH under the Tropical Medicine Research Centers (TMRC) grant (U01AI168619; AS, DKM & DMM). Additionally, we are grateful for the financial support from the following organisations and agencies: the Swedish International Development Cooperation Agency (Sida), the Swiss Agency for Development and Cooperation (SDC), the Australian Centre for International Agricultural Research (ACIAR), the Norwegian Agency for Development Cooperation (Norad), the Federal Democratic Republic of Ethiopia, and the Government of the Republic of Kenya.
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The Lancet Global Health
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Abstract
Background: Leishmaniasis is of major global health concern with global elimination targets
set for 2030. East Africa accounts for ~75% of global visceral leishmaniasis (VL) cases.
Hence, attention to endemic, recurrent or emerging foci is critical to meeting global elimination
targets. In 2021, Kajiado County, on the southern border of Kenya with Tanzania, emerged
with cases of local transmission that necessitated this investigation.
Methods: This was a mixed methods coordinated response. We conducted a training for
clinicians, sensitised communities, and set up medical camps in four villages. Here we
screened the community for VL and other common ailments and undertook an entomological
survey for sandfly vector species in the same villages. We screened 100 individuals (males:
56; females: 44) for leishmaniasis using the rK39 rapid antibody test and by microscopic
examination. Dry blood spots (DBS) were collected from suspected cases. The samples were
further analyzed using PCR targeting the internal transcribed spacer 1 (ITS1) region, followed
1
Preprint not peer reviewed
This preprint research paper has not been peer reviewed. Electronic copy available at: https://ssrn.com/abstract=5242611
by sequencing for Leishmania species identification. For entomological surveys, sandfly
sampling was done in the four villages where medical camps were implemented, and another
four adjacent villages using CDC miniature or Silverbullet 2.0 light traps. Sandflies were
identified morphologically using taxonomic keys and the speciation confirmed by PCR analysis
of the cytochrome c oxidase subunit 1 (Cox1) gene and sequencing. We characterized sandfly
blood feeding preference by PCR analysis of the vertebrate cytochrome-b (Cyt-b) gene,
followed by HRM analysis and sequencing.
Results: Ten people (10/100; 10%) tested positive for VL (eight below 15 years old - six
males and two females). Of the 22 suspected cases with lesions suspected of cutaneous
leishmaniasis (CL), eight were confirmed as being infected with Leishmania tropica. We
trapped 4,781 sandflies and identified 1,624 specimens, consisting of 422 males and 1202
females, to species. They represented four Phlebotomus spp. and eight Sergentomyia spp.
The Phlebotomus spp. included Ph. martini (8.4%; n = 136), Ph. saevus (2.2%; n = 35), Ph.
orientalis (1.2%; n = 19), and Ph. guggisbergi (0.1%; n = 1). Overall, Sergentomyia species
(62.7%, 1019 specimens) were abundant. Of the 450 sandflies examined for presence of
Leishmania parasites by PCR, we detected DNA of Leishmania donovani in Sergentomyia
clydei (n = 13), Sergentomyia adleri (n = 4), S. antennatus (n = 2), and Ph. saevus (n = 1),
while L. tropica DNA was detected in Ph. saevus (n = 1). Analysis of the blood meal sources
of the 68 engorged sand flies showed that most fed on humans followed by goats. We also
detected blood from donkeys, mongoose and rock hyraxes.
Conclusion: We confirmed L. donovani and L. tropica as the main Leishmania species
responsible for VL and CL, respectively, in Kajiado. The presence of the parasites in humans
and the high human blood indices in sandflies indicate active transmission and high vector
human contact in the area. The co-occurrence of VL and CL is unusual and complicates case
management as the two forms are managed differently, and raises the possibilities of genetic
recombination in Leishmania parasites. Since access to diagnostic and treatment facilities are
at the core of infectious diseases management, and elimination efforts, the establishment of
two treatment Centres in Kajiado, for the first time, constitutes an important step in enhancing
community access to treatment and stemming the spread of leishmaniasis in the region. This
study thus contributes to global and national VL elimination targets, and demonstrates the
value of coordinated outbreak preparedness.