Effect of mass treatment of a human population with ivermectin on transmission of Onchocerca volvulus by Simulium yahense in Liberia, West Africa

M. Trpis, J. E. Childs, D. J. Fryauff, B. M. Greene, P. N. Williams, Beatriz Munoz, M. C. Pacque, H. R. Taylor

Research output: Contribution to journalArticle

Abstract

The impact of mass treatment with ivermectin on the intensity of Onchocerca volvulus transmission by the black fly (Simulium yahense) was evaluated on the Liberian Agricultural Company rubber plantation in Liberia, West Africa. The adult pre-treatment prevalence of onchocerciasis was >80%, and the average intensity of infection was 5.35 mf/mg of skin. The drug was administered at 2 annual intervals, reaching 58-60% of the ~ 14,000 people living in 73 camps. Landing/biting catches of black flies made in central and peripheral plantation zones indicated similar fly activity before and after ivermectin treatment (man hr index of 2.1 and 2.4 within the plantation, and 10 and 10.9 outside the plantation, respectively). The number of infected flies with developing larvae (L1, L2, L3 stages) of O. volvulus in treated areas was reduced by 93.4-95%; the number of infective flies with L3 larvae was reduced by 81.7-89.3%. Parasite loads of infected (L1, L2) and infective flies (L3 stages only) outside the plantation also decreased by 86.8% and 80%, respectively. Monthly transmission potential (MTP) showed a similar decrease: from 22.9 to 5.8 (74.6% reduction) in the treated area, and from 210 to 158.8 (24.4% reduction) in untreated areas. Mass treatment with ivermectin efficiently controlled, and at least temporarily interrupted, transmission of Onchocerca volvulus by black fly vectors.

Original languageEnglish (US)
Pages (from-to)148-156
Number of pages9
JournalAmerican Journal of Tropical Medicine and Hygiene
Volume42
Issue number2
StatePublished - 1990

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Liberia
Onchocerca volvulus
Simuliidae
Ivermectin
Western Africa
Diptera
Population
Larva
Parasite Load
Onchocerciasis
Rubber
Therapeutics
Skin
Infection
Pharmaceutical Preparations

ASJC Scopus subject areas

  • Parasitology
  • Infectious Diseases

Cite this

Effect of mass treatment of a human population with ivermectin on transmission of Onchocerca volvulus by Simulium yahense in Liberia, West Africa. / Trpis, M.; Childs, J. E.; Fryauff, D. J.; Greene, B. M.; Williams, P. N.; Munoz, Beatriz; Pacque, M. C.; Taylor, H. R.

In: American Journal of Tropical Medicine and Hygiene, Vol. 42, No. 2, 1990, p. 148-156.

Research output: Contribution to journalArticle

Trpis, M. ; Childs, J. E. ; Fryauff, D. J. ; Greene, B. M. ; Williams, P. N. ; Munoz, Beatriz ; Pacque, M. C. ; Taylor, H. R. / Effect of mass treatment of a human population with ivermectin on transmission of Onchocerca volvulus by Simulium yahense in Liberia, West Africa. In: American Journal of Tropical Medicine and Hygiene. 1990 ; Vol. 42, No. 2. pp. 148-156.
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abstract = "The impact of mass treatment with ivermectin on the intensity of Onchocerca volvulus transmission by the black fly (Simulium yahense) was evaluated on the Liberian Agricultural Company rubber plantation in Liberia, West Africa. The adult pre-treatment prevalence of onchocerciasis was >80{\%}, and the average intensity of infection was 5.35 mf/mg of skin. The drug was administered at 2 annual intervals, reaching 58-60{\%} of the ~ 14,000 people living in 73 camps. Landing/biting catches of black flies made in central and peripheral plantation zones indicated similar fly activity before and after ivermectin treatment (man hr index of 2.1 and 2.4 within the plantation, and 10 and 10.9 outside the plantation, respectively). The number of infected flies with developing larvae (L1, L2, L3 stages) of O. volvulus in treated areas was reduced by 93.4-95{\%}; the number of infective flies with L3 larvae was reduced by 81.7-89.3{\%}. Parasite loads of infected (L1, L2) and infective flies (L3 stages only) outside the plantation also decreased by 86.8{\%} and 80{\%}, respectively. Monthly transmission potential (MTP) showed a similar decrease: from 22.9 to 5.8 (74.6{\%} reduction) in the treated area, and from 210 to 158.8 (24.4{\%} reduction) in untreated areas. Mass treatment with ivermectin efficiently controlled, and at least temporarily interrupted, transmission of Onchocerca volvulus by black fly vectors.",
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