TRANSMISSION OF TOXOPLASMA-GONDII IN PANAMA-CITY, PANAMA - A 5-YEAR PROSPECTIVE COHORT STUDY OF CHILDREN, CATS, RODENTS, BIRDS, AND SOIL

A cohort of more than 500 children from Panama City, Panama was studie d prospectively over five years for acquisition of antibody to Toxopla sma gondii. The direct agglutination test showed that 72 of 571 childr en seroconverted between one and six years of age, for a cumulative in cidence of 12.6%. Children were examined by pediatricians quarterly,an d illnesses that had occurred in the interval and their activities wer e noted on questionnaires. Thirty-eight variables were examined for th eir role as risk factors for seroconversion. There was a higher correl ation between children's seroconversion and contact with dogs than wit h cats. Combinations of significant predictors without dogs explained only 67% of the seroconversions, but the same factors with dogs explai ned 90%. On the other hand, ingestion of raw or rare meat or eggs appe ared to play no role in transmission. Cats were examined and 110 (45.6 %) of 241 had Toxoplasma antibody on the first bleeding. Only two (0.5 %) of 383 cat fecal specimens, when tested in mice, resulted in seroco nversion. Ten (1.1%) of 924 soil samples resulted in seroconversion in mice that had been injected. Antibody to Toxoplasma was found in 52 ( 23.3%) of 226 rats (Rattus norvegicus) and two (0.035%) of 571 mice (M us musculus). Two hundred sixteen birds of 16 different species were b led. Antibody to Toxoplasma was found in 13.4% of these birds, mostly in grackles, blue-gray tanagers, and doves. The rate of isolation of T oxoplasma was low: one of 23 in rats and three of 201 in birds. High r elative risks (RRs) of transmission to children were predicted by cont act histories with nursing dogs (RR = 5.8), weaned dogs (RR = 4.7), ma ny flies (RR 3.6), 6-12-month-old dogs (RR = 3.4), weaned cats (RR = 3 .0), 6-12-month-old cats (RR = 2.7), nursing cats (RR = 2.5), much gar bage (RR = 2.4), and many roaches (RR = 2.2). The high statistical cor relation of dog contact with seroconversion in children suggests the p ossibility that dogs, by eating and rolling in cat feces, are instrume ntal in mechanically transmitting Toxoplasma infection. In addition, f lies, and to a lesser extent, cockroaches, may have practically import ant roles in transmission.