AML 37fCL Upton, L, L, N ew York The Medical Research Cent er B rookhaven Na tiona} Lahora tay» meD.Wd. 2372 ten J Trop Med. Hye, 36¢2), 1987. pp. 315-320 Copyright © 1987 by The American Society of Tropical Medicine and Hygie ne 401842 TOXOPLASMA ANTIBODIES AND RETINOCHOROIDITIS IN THE MARSHALLISLANDS AND THEIR ASSOCIATION WITH EXPOSURE TO RADIOACTIVE FALLOUT WILLIAM H. ADAMS,* W. REED KINDERMANN,t KENNETH W. WALLS,¢ anp PETER M. HEOTIS* *Vedical Department, Brookhaven National Laboratory, Upton, New York, tWills Eye Hospital, Philadelphia. Pennsylvania, and tParasitology Division, Centers for Disease Control, Atlanta, Georgia rotpen 43.72 = 24/3 CA TIONS BOXNo, MEDICAL DEPT _PYBLI ISLANDS cottection 7ARSHALL REPOSITORY BNL REC OR DS Abstract. Nearly universal serologic evidence of Toxoplasma gondii infection was found to have occurred by adulthood in 517 Marshallese tested in 1981-1982. The prevalence and incidenceof retinal lesions compatible with toxoplasmosis were 3.9% and 273 cases/ year/ 100,000 seropositive persons, respectively, thus indicating a significant public heaith problem. Seronegativity was significantly more commonin a subgroup of Marshallese that. had received 110-190 rads of total-body gammaradiation as a consequenceof accidenta} exposure to radioactive fallout in 1954. Despite this finding there was no evidence of an increase in clinically significant lesions in exp osed persons. Human infection by the ubiquitous intracellular protozoan, Toxoplasma gondii, is manifested by a variety of clinical syndromes, the most commonbeing retinochoroiditis.' Serious illness occurs more frequently in immunosuppressed persons.” Despite the importance of the subject, no data describing the incidence of Toxoplasma retinochoroiditis are available, and even prevalence data from unselected populations are scanty. A prevalence of 0.6% was reported for a small Maryland community.’ The Medical Department of Brookhaven National Laboratory monitors medical care to a population of Marshallese which was accidentally exposed to radioactive fallout from a thermonuclear test detonation on Bikini atoll! in 1954.4 Tropical Pacific populations are known to have a high prevalence of positive serologic tests for T. gondii.°-’ To determine if radiation exposure may have produced longterm immunosuppression which might place the exposed population at greater risk for clinical illness due to toxoplasmosis, a serologic survey for evidence of past infection, supported by ophthalmologic examinations, was undertaken. Toxoplasmosis has been described as a relatively unimportant public health problem on certain Pacific islands, in part because the high prevalence of positive serologic tests at an early age wasfelt to indicate thatlittle opportunity existed for fetal infection.° To determine whether or not toxoplasmosis should be viewed as a serious public health threat in the Republic of the Marshall Islands, a second goal of the investigation was to evaluate the prevalence of Toxoplasma seropositivity and the prevalence and incidence of suspected Toxoplasma retinochoroiditis in a larger population of Marshallese which included unexposed individuals. MATERIALS AND METHODS The Republic ofthe Marshall Islands is located in eastern Micronesia approximately 2,500 miles southwest of Hawaii. Its population of 33,000is spread over 29 atoils and 5 mountain-top islands. Following World War II, the Marshall Islands were made a United Nations Trust Territory under U.S. trusteeship. Twoatolls, Bikini and Enewetok, were subsequently used by the U.S. government as nuclear weapons proving groundsafter relocation of the island inhabitants. In 1954 radioactive fallout from a U.S. ther- monuclear test on Bikini atoll descended accidentally on the populations of Rongelap and Utirik atolls located approximately 100 and 300 miles distant, respectively.* Eighty-six Rongelap individuals (including 4 in utero) and 159 persons on Utinik (including 8 in utero) received an estimated 110-190 and 11 rads of total-body Accepted 9 September 1986. gamma radiation, respectively. Thyroid-ab- 315