No abstract

Age-stratified data on toxoplasma seroprevalence in pregnant women in Stockholm, Sweden for the years 1969, 1979 and 1987 provide the basis for an analysis of temporal patterns of Toxoplasma gondii infection, and estimation of the risk of maternal toxoplasmosis, in this population. A catalytic infection model, in which the rate or force of infection is assumed to be a function of time (and not, as is more usual, age), was employed to describe the observed changes in levels of toxoplasma seropositivity. A range of simple incidence functions (up to 3 parameters) were fitted using a method of maximum likelihood. The data were significantly better described by a linear or an exponential decay in the rate of infection through time compared with a constant level. More complex incidence functions gave no better data description. Thus, whilst there is strong evidence for declining incidence in Stockholm over the past 4-5 decades, the data do not allow discrimination between different possibilities for the nature of this decline. Based on these modelling results, best estimates of the force of infection in 1987 acting on susceptible women are within the range 0 to 0.0045/susceptible/year (95% confidence limits), yielding a possible risk of maternal toxoplasmosis of between 0 and 2.7 cases/1000 pregnancies. These values are shown to be significantly lower than estimates based upon an assumption of temporal stability in toxoplasma incidence, which may be of practical significance to public health policy.

Surveys of pregnant women in four areas of Sweden in 1987-88, reveal a significant trend for decrease in Toxoplasma seroprevalence from Gotland island (26%, n = 467) in the south through Orebro county (18%, n = 1413) and Stockholm area (18%, n = 939), to Northern Sweden (12%, n = 837). No within area differences were observed between samples from rural and urban localities. Quantitative antibody data indicate marginally higher levels in the north than in the south, and a significant declining trend by age only in Orebro county. Incidence models are used to describe age-seroprevalence profiles for each area, using different assumptions about age- and time-specific infection rates, and to estimate the risk of maternal infection at the time of the survey. It is shown that the patterns of seroprevalence with age in Orebro county and Northern Sweden, but not Gotland island or Stockholm, strongly implicate time-dependent changes in Toxoplasma incidence, consistent with a declining incidence in the past which has possibly been reversed in recent years. The estimates of Toxoplasma incidence and risk of maternal toxoplasmosis are strongly dependent upon the underlying assumption of temporal change in incidence, with wide ranges in the predicted values. These studies demonstrate the difficulties in interpretation of horizontal cross-sectional data and the need for longitudinal studies of age-prevalence and seroconversion in the determination of the true risk of maternal toxoplasmosis.

In order to study the long-term course after herpes simplex virus type 2 (HSV-2) meningitis and/or myeloradiculitis the records of 40 consecutive patients were studied. During the year following the acute phase, verified or suspected neurologic recurrences were noted in nearly half of the patients: 1 or more episodes of recurring meningitis were noted in 8 patients; new episodes of myelitis or radiculitis in 3; distinct attacks of headache in 4; and diffuse neurologic complaints impairing daily life in 3. Recurring mucocutaneous symptoms were observed in 16 patients. Eleven patients experienced concurrent or separate episodes of recurring mucocutaneous and neurologic symptoms, 7 had neurologic recurrences only and 5 had only mucocutaneous recurrences. As considerable morbidity may result, patients with HSV-2 meningitis and/or myeloradiculitis should be identified by means of thorough history-taking, careful examination and a specific viral diagnosis in order to enable adequate advice and counseling to be provided and to aid decision-making regarding antiviral therapy.