Tag Archives: Worms

Worm Wars Continued

We have discussed results of deworming before and argued that it is important to treat at cluster level because of rapid re-infection from reservoirs in soil. A recent important meta-analysis compares deworming targeted at children versus a community-wide intervention.[1] It finds that community-wide approaches are more effective than treatment targeted at children for roundworms (Ascaris) and hookworms (Ancylostoma), but not whipworms (Trichuris). This finding is consistent with the much greater efficiency of the medicine in the former two worm types. The relative effect was greater in roundworms (odds ratio >16) than the more dangerous hookworms (OR >4), consistent with the shorter life-span of hookworm eggs than of roundworm eggs. These are important findings, but there is a worry that resistance may emerge with mass treatment. It would be interesting to see whether any studies have been done in slum populations specifically.

— Richard Lilford, CLAHRC WM Director

Reference:

  1. Clarke NE, Clements ACA, Doi SA, et al. Differential effect of mass deworming and targeted deworming for soil-transmitted helminth control in children: a systematic review and meta-analysis. Lancet. 2017; 389: 287-97.
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Nice Theory, but Ridding Children of Those Revolting Worms Does Not Seem to Affect Health

Wouldn’t it be nice if we could find a simple physical cause for stunted-growth and impaired school performance? Worm infestations provide such a target; round worms (which may compete for the child’s nutrition), and hook worms (which suck blood through the intestinal wall). Alas the attractive notion that we can do a great deal of good by the simple distribution of de-worming pills does not seem to be true. The recent meta-analysis from Paul Garner’s group [1] provides little support for de-worming policies. Even among children known to be infected, de-worming does not do anything dramatic, and surprisingly (and disappointingly) the trials examining this issue are of poor quality.

It could be argued that de-worming does not do any harm, and that worms are revolting, and therefore that de-worming programmes should continue. But in a world of scarce resources, this argument might not hold. And then of course some people say that worms do some good by providing an inflammatory response that reduces atopic conditions, such as hay fever of asthma.[2]

Science cannot prove a negative, merely exclude effects of measurable size, and we may never have a conclusive answer to this question. Comments are invited on this controversial issue.

— Richard Lilford, CLAHRC WM Director

References:

  1. Taylor-Robinson DC, Maayan N, Soares-Weiser K, Donegan S, Garner P. Deworming drugs for soil-transmitted intestinal worms in children: effects on nutritional indicators, haemoglobin, and school performance. Cochrane Database Sys Rev. 2015; 7: CD000371.
  2. Quinnell RJ, Bethony J, Prichard DI. The immunoepidemiology of human hookworm infection. Parasite Immunol. 2004; 26(11-12): 443-54.