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/

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