Abstract:
Arthropod vectors are responsible for a multitude of human and animal diseases affecting
poor communities in sub-Saharan Africa. Their control still relies on chemical agents, despite growing
evidence of insecticide resistance and environmental health concerns. Biorational agents, such as the
entomopathogenic fungus Metarhizium anisopliae, might be an alternative for vector control. Recently,
the M. anisopliae isolate ICIPE 7 has been developed into a commercial product in Kenya for control
of ticks on cattle. We were interested in assessing the potential of controlling not only ticks but also
disease-transmitting mosquitoes and tsetse flies using cattle as blood hosts, with the aim of developing a
product for integrated vector management. Laboratory bioassays were carried out with M. anisopliae,
isolate ICIPE 7 and isolate ICIPE 30, to compare efficacy against laboratory-reared Anopheles arabiensis.
ICIPE 7 was further tested against wild Glossina fuscipes and Rhipicephalus spp. Dose–response tests
were implemented, period of mosquito exposure was evaluated for effects on time to death, and the
number of spores attached to exposed vectors was assessed. Exposure to 109
spores/mL of ICIPE 7 for
10 min resulted in a similar mortality of An. arabiensis as exposure to ICIPE 30, albeit at a slower rate
(12 vs. 8 days). The same ICIPE 7 concentration also resulted in mortalities of tsetse flies (LT50: 16 days),
tick nymphs (LT50: 11 days), and adult ticks (LT50: 20 days). Mosquito mortality was dose-dependent,
with decreasing LT50 of 8 days at a concentration of 106
spores/mL to 6 days at 1010 spores/mL. Exposure
period did not modulate the outcome, 1 min of exposure still resulted in mortality, and spore attachment
to vectors was dose-dependent. The laboratory bioassays confirmed that ICIPE 7 has the potential to
infect and cause mortality to the three exposed arthropods, though at slower rate, thus requiring further
validation under field conditions.
