INTESTINAL PARASITISM IN THE UNITED-STATES - UPDATE ON A CONTINUING PROBLEM

To document patterns of intestinal parasitism in the United States, we analyzed results of 216,275 stool specimens examined by the state dia gnostic laboratories in 1987; parasites were found in 20.0%. Percentag es were highest for protozoans: Giardia lamblia (7.2%), Entamoeba coli and Endolimax nana (4.2% each), Blastocystis hominis (2.6%), and Enta moeba histolytica (0.9%). The most commonly identified helminths were nematodes: hookworm (1.5%), Trichuris trichiura (1.2%), and Ascaris lu mbricoides (0.8%). Identifications of G. lamblia increased broadly fro m the 4.0% average found in 1979, with 40 states reporting increases a nd seven reporting decreases. Seasonally, Giardia identifications incr eased in the summer and fall, especially in the Midwest. Nine states r eported hookworms in more than 2% of specimens; none were states with indigenous transmission. We analyzed similar, but abbreviated, data fo r 1991; parasites were found in 19.7% of the 178,786 specimens and Gia rdia was found in 5.6%. States reporting percentages of Giardia identi fication in the highest quartile for both 1987 and 1991 were located i n the Midwest or in the Northwest. Cryptosporidium was identified in b oth the 1987 and 1991 surveys; it had not been identified in a previou s survey. For each year, Cryptosporidium was reported from 25 states a cross the country (for both years in 17 states). We conclude that inte stinal parasitism should not be overlooked as a cause of gastrointesti nal illness in the United States and that the prevalence of Giardia ma y be increasing.