Rapid reinfection by Giardia lamblia after treatment in a hyperendemic Third World community

Abstract

In a peri-urban shanty town in Lima, Peru, that was hyperendemic for Giardia lamblia, 44 children aged between 0.9 months and 10 years were effectively treated for Giardia lamblia with tinidazole. Stools were examined weekly in the 6 months after treatment to determine the rate of reinfection, and after reinfection stools continued to be examined. 98% of the children became reinfected with Giardia lamblia within 6 months, and after reinfection stool excretion of the parasite lasted a mean (SD) of 3.2 (3.3) months. The children's mean stool pH and their mean stool fat index was unaffected by Giardia lamblia reinfection. Treatment of all symptomless Giardia lamblia infections in a developing country hyperendemic for the disease is of questionable value because of rapid reinfection.

PIP: Giardia lamblia is 1 of the 1st parasites to infect infants and young children in both developed and developing countries. In the peri-urban shanty towns of Lima, Peru, this parasite infects nearly all children before they reach 2 years of age. This study was performed in 1 such setting. 44 children aged between 0.9 months and 10 years were effectively treated for Giardia lamblia with tinidazole. Stools were examined weekly in the 6 months after treatment to determine the rate of reinfection, and after reinfection stools continued to be examined. 98% of the children became reinfected with Giardia lamblia within 6 months, and after reinfection stool excretion of the parasite lasted a mean of 3.2 months. The children's mean stool pH and their mean stool fat index was unaffected by the reinfection. It would appear that in areas hyperendemic for Giardia lamblia, such as the shanty towns in Lima, treatment is not an effective public health measure, since nearly all children become rapidly reinfected and the protozoa can be excreted in the stools for a long time after reinfection. The high rate of reinfection after therapy, lack of an age differential, and long duration of parasite excretion after reinfection all suggest that children in developing countries do not acquire immunity to recolonization with Giardia lamblia. On the basis of this data it is suggested that in resource-limited communities in developing countries where Giardia lamblia is hyperendemic, children found to be excreting Giardia lamblea in their stools should be treated only when clinically indicated and not routinely.