316 ADAMS ET AL. TABLE | Toxoplasma antibodies in Marshallese Group Number tested Number posiuve (%} 235 282 517 221 (94.0) 264 (93.6) 485 (93.8) 10 61 141 113 66 63 63 8 (80.0) 57 (93.4) 135 (95.7) 104 (92.0) 60 (90.9) 61 (96.8) 60 (95.2) Meanlog titer* + SD By sex: Male Female Total By age in 1982: “he ere: ‘ * Ficure 1. Retinal lesion characteristic of toxoplasmosis which was identified ina Marshallese subject with serum antibody to Toxoplasma gondii. sorbed radiation from radioiodines was much greater and has been described elsewhere.*® Since 1954 annual medical examinations and treatment have been offered to the exposed persons. This program has been carried out by the Medical Department of Brookhaven National Laboratory under contractto the Atomic Energy Commission (now the U.S. Department of Energy). In order to detect unsuspected medical consequencesof the Rongelap and Utirik radiation exposure, an unexposed population of Marshallese has also been examined annually. That population, termed the “‘comparison”’ group, is Statistically similar to both of the exposed populations in age and sex distribution.’ In addition, other Marshallese are included in the examinations on the basis of humanitarian need as resources permit. Almost all persons examinedresided on one of four islands: the remote islands of Rongelap and Utirik, where fallout had settled, and Ebeye and Majuro, the Marshallese population centers. During the 1981 examinations, retinal lesions compatible with toxoplasmosis were observed using indirect and direct ophthalmoscopy performed by Brookhaven consultant ophthalmologists. The lesions observed were typical of toxoplasmosis and included punctate or smoothedged, roundish, chorioretinal scars with altered pigmentation (Fig. 1). The retinal findings prompted a serologic survey of the population for antibodies to the parasite. A review of medical records of the examined persons indicated that similar lesions had been documentedin earlier years by other ophthalmologists, but the possible association with toxoplasmosis had not been commented on. Included in the survey were all 10-14 15-19 20-29 30-39 40-49 50-59 >59 7.9 9.0 8.1 8.5 8.2 8.6 8.5 + + = + + + 2.9 2.2 2.3 2.0 2.3 2.0 1.8 By island of residence: Ebeye Majuro 103 62 Utink 172 Rongelap 87 99 (96.1) 36 (90.3) 78 (89.7) 167 (97.1) By radiation exposure group: Rongelap Utirik Comparison 62 51 (82.3) 98 95 (96.9) 100 96 (96.0) 7.9 + 2.2 8.6 + 2.0 8.1 + 2.0 By island, excluding exposed persons: Ebeye Majuro Rongelap Utink 68 53 71 172 66 (97,1) 51 (96.2) 67 (94.4) 167 (97.1) By island, born subsequentto fallout: Ebeye Majuro 42 Utink 74 Rongelap not tested 36 38 (90.5) 34 (94.4) 72 (97.3) * Mean titer of seropositive persons. individuals in the exposed and comparison groups who presented for medical examination during the survey,as well as other Marshallese who were offered medical examinations at that time. Four hundred thirty-two serum samples were collected and 457 ophthalmologic examinations were performed. Additional sera were collected in 1982 from examinees who were unavailable in 1981, bringing the total to 517. In 1985 follow-up ophthalmologic examinations were performed on 275 individuals knownto be seropositive for toxoplasmosis and negative for retinochoroiditis as a result of the 1981-1982 survey. Toxoplasma antibody testing using a fluorescence immunoassay was performed in the Parasitology Division, Centers for Disease Control.'° Results were reported as log titers and analyzed as either meanlog titer or as positive/