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Low incidence of primary infection with toxoplasma among women in Sheffield: a seroconversion study
P M Zadik1, G Kudesia, A D Siddons
1Sheffield Regional Public Health Laboratory, UK.
Objective:
To determine the incidence of primary toxoplasma infection in women of childbearing age.
Design:
A retrospective study of seroconversion on stored pairs of sera taken for routine antenatal testing.
Setting:
The antenatal clinics and general practices of Sheffield between July 1989 and October 1992.
Subjects:
One thousand six hundred and twenty-one women on whom pairs of sera, separated by more than 500 days, had been received.
Main Outcome Measure:
Rate of primary infection determined by seroconversion as measured by the presence of antibody in the second serum and its absence in the first.
Results:
Of 1621 women, 160 (9.9%) were initially seropositive. One seroconversion was detected in 2966 woman years of observation for susceptibles. The projected rate for primary infections was 0.23 (95% CI 0.0059-1.3) per 1000 pregnancies.
Conclusions:
The rate is much lower than for earlier estimates of incidence in the UK but agrees with a more recent estimate from Sheffield and suggests a falling incidence.