Schistosoma mansoni chemoprophylaxis with dietary lapachol
Austin, F.G.
American Journal of Tropical Medicine and Hygiene 23(3): 412-419
1974
ISSN/ISBN: 0002-9637 PMID: 4823795 Document Number: 72634
Mice were given lapachol [2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone] by gavage and exposed to Schistosoma mansoni cercariae by tail immersion. Worm counts at 8 weeks after infection showed that the lapachol had reduced cercarial penetration by 6.4 to 37.2%; worm burdens were 13.5 to 100% less than those of controls depending on dosage. A number of mice which received high doses died with occluded stomachs. In a further experiment, lapachol was fed at 0.91% in the diet or given as the sodium salt in the drinking water at 0.5% to mice from mid-day on day 0 to mid-day one, 2, 3 or 4 days later when they were exposed to S. mansoni cercariae by tail immersion or whole body wading. Infection was reduced by 80% after 24 hours of feeding and by 96.9% after 3 days of feeding the treated diet. Protection declined from 70 to 35% from 0 to 3 days after a single 24-hour feeding period. The sodium salt in drinking water reduced infection by 26.7 to 72.6%. Ultraviolet spectrophotometry demonstrated that the lapachol is secreted onto the skin where it acts as a topical barrier to penetration. In 14 of 15 mice fed lapachol at 2,860 mg/kg body-weight daily for 4 days, loss of weight was the only sign of toxicity observed; in the remaining mouse, loss of weight was excessive and the animal died.