AN INCREASE IN GIARDIA-DUODENALIS INFECTION AMONG CHILDREN RECEIVING PERIODIC ANTHELMINTIC TREATMENT IN BANGLADESH

During a deworming study in northern Bangladesh, the prevalence of Gia rdia duodenalis increased significantly among three groups of children receiving periodic treatment with mebendazole. This was first observe d in the treatment group (Group A) of a 12-month study. Giardia increa sed from 5 to 31 per cent in Group A (n = 49 chi(2) = 10.42, P < 0.005 ), but did not increase significantly in the placebo group (Group B) ( 11 to 18 per cent; chi(2) = 0.4, P = NS). The prevalence of Giardia in the treatment and placebo groups was not significantly different at t he beginning of the study (n = 89, chi(2) = 0.8, P = NS). During a 6-m onth follow-up study, children in Groups A and B received 2-monthly tr eatment with mebendazole. Within 6 months the prevalence of Giardia in creased significantly in Group B from 18 to 44 per cent (chi(1)(2) = 6 .14, P < 0.05). The prevalence of Giardia was also examined in 265 chi ldren at the end of an 18-month deworming study in the same area and f ound to be significantly higher among the treatment group (Group C) co mpared with the placebo group (Group D) (38 v. 21 per cent, chi(2) = 8 .87, P < 0.005). Finally, the prevalence of Giardia was significantly higher in Group B after being treated than in Group D which had not be en treated (44 and 21 per cent, respectively, chi(2) = 9.08, P < 0.005 ). These children were from the same villages and measured during the same month of the monsoon season. The increase in Giardia infection di d not appear to relate to seasonal changes in prevalence or difference s in prevalence due to local conditions and may therefore be related t o the introduction of regular deworming.