Seroepidemiology of schistosomiasis in Puerto Rico: Evidence for vanishingendemicity

The current study summarizes our findings of anti-schistosome egg antibody by the circumoval precipitin test for two different populations in Puerto R ico. One group, exclusively males more than 40 years of age and from all mu nicipalities on the island, was from the Veterans Administration Hospital f or the period 1988-1997. The second group resided southeast of San Juan, ar ound the municipality of Caguas and adjacent municipalities east of Caguas, was of both sexes and mostly until 1997 of undetermined ages for the perio d 1993-1997. Results reveal a yearly decrease in testing requests from the Veterans Administration Hospital from 148 in 1988 and 1989 with 16% positiv e to three in 1996 through 1998 with none positive. This decrease in testin g requests was because of a decrease of suspicion of schistosomiasis in thi s group. The other patient population from the Caguas region showed a gradu al but continuous decrease in seropositive individuals from 21% in 1993 to 12% in 1996, with precipitous decrease to 5% in 1997 and only 1% in 1998. M oreover, there were four patients from which at least two serum samples wer e obtained one or two years apart and tested. In each instance the more rec ently obtained sample had lower antibody reactions than the first as reflec ted in lower percentages of positive egg reactors. The fact that they were treated with praziquantel after the first testing also suggests that the in fected population was being eliminated through chemotherapy. These combined results suggest the elimination of infections with Schistosoma mansoni in the traditionally high prevalence regions east of San Juan in the absence o f any proactive control efforts in Puerto Rico. Because of the rapid urbani zing of Puerto Rico, the one identifiable control effort is economic develo pment and well being.