Arithmetic or geometric means of eggs per gram are not appropriate indicators to estimate the impact of control measures in helminth infections.
In helminthology, the mean number of eggs per gram of faeces (EPG) is a commonly used indicator for the severity of the infection in a population. The example presented here shows that, in my opinion, mean EPG (either calculated as arithmetic or geometric means) is not the best way to evaluate the impact of control measures, as helminth infections present an intensity/morbidity relationship, which should be considered when selecting indicators for the evaluation of control measures. In my opinion, an analysis by class of intensity is more informative.
Montresor
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Vectorborne and other Parasitic Diseases, World Health Organization, Ha Noi, Viet Nam. montresora@vtn.wpro.who.int <montresora@vtn.wpro.who.int>
D000818:Animals; D005243:Feces / Q000469:parasitology*; D006373:Helminthiasis / Q000175:diagnosis* / Q000517:prevention & control; D006801:Humans; D007411:Intestinal Diseases, Parasitic / Q000175:diagnosis* / Q000517:prevention & control; D010270:Parasite Egg Count / Q000379:methods*