Occurrence and monthly dynamics of female Phlebotomine sandfly species from Kousseri Visceral Leishmaniasis endemic focus in northern Cameroon

Leishmaniasis, an anthropozoonotic infection transmitted to humans and animals through female sandfly bite, is endemic in the far north region of Cameroon, which currently lacks a control programme. This study aimed to assess the occurrence and monthly distribution of sandflies in Kousseri County, a region with reported cases of visceral leishmaniasis (VL), to provide data needed for combatting the disease. Sandfly occurrence was evaluated by monthly deployment of six CDC light traps over a twelve-month period (from September 2020 to August 2021) in urban, peri-urban and rural ecotopes. Our survey collected 4,214 sandflies, including 51.02% females. The highest abundance of sandflies was recorded in the rural areas (43.43%, n = 1830) and in January during the dry season (16.22%, n = 679). Ten sand fly species from the Sergentomyia genus Franca and Parrot 1920 and one species of the Phlebotomus genus Rondani and Berté 1840 were identified. The monthly dynamics of the collected female sandflies varied markedly: Se. antennata Newstead, 1912, the most prevalent species and Se. squamipleuris Newstead, 1912 showed unimodal peaks in January and February, respectively; Se. schwetzi Adler, Theodor & Parrot, 1929 exhibited a trimodal pattern with a major peak in September; Se. distincta followed a bimodal trend with peaks in January and May. The aforementioned sandfly species were present throughout the study period, while other species displayed variable and intermittent presence. Ph. duboscqi, the sole known vector of leishmaniasis in this study, was absent in January and July, but peaked in September, representing only 1.07% of the total catch. The Shannon–Wiener index was high (H > 1) in all the collected ecotopes and months, indicating high evenness and Simpson indices. Overall, the findings suggest that sandflies are active year-round in Kousseri, with elevated abundance during the dry season, particularly in January and March. The presence of animal shelters surrounding houses, vegetation (primarily rice paddies) and building conditions with unplastered, fissured mud walls likely favour a high abundance of sandflies in rural areas in Kousseri. These findings highlight the need of optimising surveillance and intervention strategies, especially in rural settings and during months when sandflies are more active. Further studies on climatic and environmental factors affecting sandfly distribution, as well as investigations into their feeding habits and Leishmania infection rates, are crucial for enhancing disease control in the region.