Impact of ivermectin mass distribution for onchocerciasis control on Ascaris lumbricoides among schoolchildren in Rungwe and Kyela Districts, southwest Tanzania

Abstract

Across-sectional survey on the impact of ivermectin treatment for onchocerciasis control, on Ascaris lumbricoides
infections was conducted in 1994, before the first treatment cycle was implemented in the Tukuyu focus in Tanzania. A
total of 560 pupils were randomly selected for stool samples before, 7 days and 3 months after treatment. Modified Kato
Katz technique was used to prepare slides, and a dissection microscope for examination. Results showed pre-treatment
A. lumbricoides prevalence ranging from 4.2% (Lutete) to 34.0% (Lufilyo). At day seven post-treatment, samples were
devoid of Ascaris eggs, except at Lufilyo with 2.9% prevalence. Three months post treatment showed 34 (8.2%) out of 213
pupils had patent infections and 24 (5.8%) re-infections. Mean infection intensities were significantly higher at pretreatment
than three months post-treatment. A. lumbricoides adult worm expulsion was self-reported in the first week of
treatment, especially 2-3 days after, by 21.9% participants. Ivermectin treatment was effective against adult A. lumbricoides
and cleared egg excretion by day seven, but re-infection occurred within three months. Visible worm excretion was
appreciated as potency of treatment. Long term mass treatment with ivermectin proposed for onchocerciasis control can
be used to reduce A. lumbircoides infections. To benefit optimally from this programme, additional inputs should be
availed to reduce re-infection between consecutive annual cycles. Appreciation of visible worm expulsion enhanced
acceptance and compliance of onchocerciasis control campaign using ivermectin. Follow-up surveys are recommended.

Keywords: Ivermectin, onchocerciasis, Ascaris lumbricoides, schoolchildren, Tanzania

Tanzania Health Research Bulletin Vol. 8 (2) 2006: pp. 70-74