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Ivermectin prophylaxis against experimental Onchocerca volvulus infection in chimpanzees
H R Taylor1, M Trpis, E W Cupp
1International Center for Epidemiologic and Preventive Ophthalmology, Wilmer Institute, Johns Hopkins University, Baltimore, Maryland 21205.
Summary
Ivermectin showed a partial prophylactic effect against early Onchocerca volvulus larvae (L3) in chimpanzees. However, ivermectin did not impact later larval stages (L4) or patent infections.
Area of Science:
- Parasitology
- Tropical Medicine
- Pharmacology
Background:
- Onchocerca volvulus causes onchocerciasis, a debilitating neglected tropical disease.
- Preventive strategies against O. volvulus infection are crucial for disease control.
Purpose of the Study:
- To evaluate the prophylactic efficacy of ivermectin against early larval stages of Onchocerca volvulus in a primate model.
- To determine if ivermectin affects the development of O. volvulus larvae in vivo.
Main Methods:
- Eighteen chimpanzees were inoculated with approximately 250 infective L3 O. volvulus larvae.
- Treatment groups included immediate ivermectin administration (day 0), delayed administration (day 28), and a control group.
- Monthly skin snips were analyzed for patent infection over 30 months.
Main Results:
- One chimpanzee treated on day 0 developed a patent infection.
- Four of six chimpanzees treated on day 28 developed patent infections.
- Four of six control chimpanzees developed patent infections, indicating a partial effect of ivermectin on L3.
Conclusions:
- Ivermectin demonstrates a partial in vivo prophylactic effect against the third larval stage (L3) of Onchocerca volvulus.
- Ivermectin has no discernible effect on later larval stages (L4) or the establishment of patent infections in this model.