Abstract:
Introduction: The recent detection of An. stephensi, an invasive vector, in Ethiopia and other
parts of the Horn of Africa has raised concerns about increased malaria transmission due to its
adaptability to urban environments. Larviciding is crucial to combat this challenge, especially
given the limitations on multiple-insecticide resistance by the vector and environmental
contamination from chemical insecticides. Hence, this study aims to address the knowledge gap in
the biological activity and residual efficacy of Natular Mini DT larvicide against An. stephensi, a
critical step towards developing targeted and sustainable control strategies.
Methods: Longitudinal semi-field study was conducted at the Tropical and Infectious Disease
Research Center (TIDRC) Field Research Station in Awash Sebat Kilo, Afar, Ethiopia, between
November 2024 and February 2025. The research evaluated prolonged larvicidal effect of Natular
Mini DT in 50-litre of water under two conditions; with no water replacement and 50% weekly
water replacement. Larval count data were collected every 24 hours across treatment and control
groups and presented using descriptive statistics and bar graphs with 95% confidence intervals. A
difference in larval mortality between treatment and controls was assessed using t- test. Larval
mortality difference between treated water regimens and residual efficacy were statistically
assessed using binary logistic regression.
Results: Our study revealed that Natular Mini DT exhibited a rapid larvicidal effect, with mortality
rates reached a peak at 72 hours, despite 100% mortality was not recorded within 72 hours for the
first two weeks, regardless of water conditions. There was a significant difference in mean larval
mortality between treatment and control groups. The comparison of treated water regimens
revealed that the absence of water replacement resulted in a 75% lower likelihood of larval
mortality rate within 24 hours. Furthermore, the larvicide showed significant residual efficacy for
12 weeks.
Conclusion: The study showed that Natular Mini DT larvicide resulted in 100% larval mortality
and residual efficacy for 12 weeks against An. stephensi, which showed a promising solution for
controlling malaria transmission. However, the residual efficacy and non-target effects of Natular
Mini DT larvicide should be evaluated under field condition in different eco-epidemiological
settings and seasons
