Effects of an Irrigation Scheme on Malaria Burden in Irrigated and Non-irrigated Areas of Homa Bay County, Western Kenya.

Abstract

Malaria control efforts in the Lake Victoria Basin region have been stepped up by combining indoor residual spray intervention with long-lasting insecticidal nets (LLINs) to reduce malaria transmission rates. However, ongoing irrigation projects in arid and semiarid areas may have a direct impact on malaria epidemiology and anemia. The objective of the study was to compare the prevalence of Plasmodium infection, malaria treatment behavior, prevalence of anemia in irrigated and non-irrigated areas in Homa Bay County, Kenya. The study used a two-stage sampling method to recruit participants aged six months and above. Cross-sectional surveys were conducted in February 2018, just before the introduction of IRS, and was repeated in June 2018, February 2019, June 2019, and July 2020, during IRS's annual application. The blood samples were collected via the finger-prick for microscopy and qPCR analysis of Plasmodium infection and to determine the level of hemoglobin among participants. In addition, passive case detection was conducted in ten public healthcare facilities to determine monthly malaria cases, methods of diagnosis and antimalarial drug availability. Structured questionnaires were used to determine malaria knowledge, treatment seeking behavior, and predictors of malaria treatment-seeking. During wet season, the prevalence of Plasmodium infection was significantly greater in irrigated areas (15.3%) than in non-irrigated areas (7.8%) (² = 8.7, p = 0.003). However, during the dry season, the prevalence of Plasmodium infection was not significantly different between irrigated (1.7%) and non-irrigated areas (1%) (p > 0.05). During the wet season, anemia prevalence was found to be higher in communities living in non-irrigated areas (51.5%) than in communities residing in irrigated areas (38.9%) (p = 0.001). Similarly, during the dry season, non-irrigated areas had a higher prevalence of anemia (34.1%) than irrigated areas (25.2%) (p = 0.007). Prevalence of Plasmodium infections significantly reduced following the introduction of IRS. For example, just

before the start of IRS, the prevalence of Plasmodium infection was 18.5% (113/610) by microscopy. However, after the first IRS application, the prevalence of Plasmodium infection dropped to 14.2% (105/737) and 3.3% (24/720) (p < 0.0001). Similarly, after the second round of IRS applications, the prevalence of Plasmodium infections dropped to 1.3% (11/849) (p < 0.0001). The majority of local residents with fever (50.3%) purchased antimalarial drugs from a chemist. Key predictors of treatment seeking included access to healthcare facility (OR = 16.23, 95% CI: 2.74-96.12), and ability to pay hospital bill (OR = 10.6, 95% CI: 1.97- 57). Although irrigation scheme was linked to an increase in malaria transmission in the study area, the prevalence of anemia in irrigated areas were significantly lower than in non-irrigated areas. To reduce cryptic P. falciparum transmission, proper malaria management and adequate support for healthcare facilities to provide quality services are critical. Improved malaria control strategies should be considered to reduce the rates of asymptomatic and submicroscopic infections. The Ministry of Health should consider launching a community-based awareness campaign to educate the general public about the importance of seeking medical attention at a healthcare facility.