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Background: The favorable attitude among the public towards prenatal diagnostics in Finland allowed us to start a trial on population basis when screening for Down's syndrome by maternal serum markers and age was introduced., Methods: Screening by maternal serum markers for Down's syndrome was offered to all 17,200 pregnant women in the Helsinki area during the study period of 2.5 years. Screening due to advanced maternal age, 37 years or more, was continued as previously, and 1133 pregnant mothers used this option. Alpha-fetoprotein, human chorionic gonadotrophin, and during the first year also unconjugated estriol were used as markers., Results: The uptake of serum screening was 84%. The proportion of false positive results i.e. risk for Down's syndrome, 1:350 or more at term, was initially 5.7%. After ultrasound scan 4.1% of the mothers remained 'screen positive'. The amniocentesis or chorionic villus sampling uptake was 98.4%. Ten out of eighteen cases of Down's syndrome were detected by maternal serum screening, sensitivity 56%, 95% CI 31-79%. Other chromosomal abnormalities were found in three cases, and there were four cases of mosaicisms confined to the placenta. These were trisomies 16, 7 and 2, and tetraploidy. Elevated serum alpha-fetoprotein was found initially in 0.7% of the cases. One case of congenital nephrosis of the Finnish type and ten other, mainly structural, abnormalities were detected by high AFP., Conclusions: The screening was well received by the mothers. The detection rate of 56% is in the same range as in previous studies. Ultrasound scan before the test would effectively lower the false positive rate caused by incorrect timing.

Genotyping of hepatitis C virus (HCV) is important because of its clinical and epidemiological implications. We report here the distribution of HCV genotypes in various patient groups in Finland using a rapid and reliable HCV typing method based on restriction fragment length polymorphism (RFLP) of the amplified DNA from the 5' non-coding region of the genome. The reaction product from the primary, diagnostic PCR (nested, one tube system) was used in genotyping. From 264 Finnish sera we identified HCV genotypes 1a (14%), 1b (24%), 2b (20%). 3a (41%) and 1a + 1b (1%). Only one patient with genotype 2a was identified. From four Egyptian blood donors, types 1b and 4 were found. Genotype 3a was more often associated with i.v. drug abuse and younger age profile (less than 30 years).

Congenital toxoplasmosis results from maternal primary infection during pregnancy. In our serologic screening study 42 of 16,733 pregnant women had findings suggestive of primary infection. Here we document the outcome of their offspring, 37 of 39 liveborn children. After 12 months postnatally, serologically verified congenital toxoplasmosis appeared in 4 children. All these children had persisting IgG at the age of 12 months by both the dye test and the IgG enzyme-linked immunosorbent assay. All the congenitally infected infants had also specific IgM and IgA and showed significant increases in avidity of specific IgG during the 12-month follow-up. One of them had a unilateral retinal scar and intracranial calcifications. An additional 3 infants of the mothers with primary infection during early pregnancy presented with unilateral retinal scars but without seroresponses during the first 12 months of life. Maternal high avidity of IgG during the first trimester is a strong indicator against primary infection during pregnancy; the fetuses of such mothers are at low risk for congenital toxoplasmosis.

Congenital toxoplasmosis is a risk for fetus both in 'low' and 'high risk' areas. A cost-benefit analysis based on data from a Finnish prospective study (20.3% seropositivity of pregnant mothers and incidence of 2.4/1,000 seronegative pregnancies) and on Finnish cost data was performed to compare the no-screening and screening alternatives for primary toxoplasma infections during pregnancy. A maternal-feto transmission risk of 40%, effectiveness of treatment of 50%, and discount rate of 4% were used as other baseline probabilities. The calculations were carried out by decision analysis combined with sensitivity analysis. The total annual costs of congenital toxoplasmosis without screening amount to US$ 128/pregnancy/year, and with systematic serological screening, US$ 95/pregnancy. Thus screening reduces the costs by 25%. The present value of net savings in Finland would be US$ 2.1 million every year. A one-way sensitivity analysis showed that screening together with health education is preferable to health education without screening if the incidence of maternal primary infections exceeds 1.1/1,000 and effectiveness of treatment is better than 22.1%. Screening for toxoplasma infections during pregnancy is economically worthwhile even in a country with a low incidence. A scheme of systematic screening for maternal primary toxoplasma infections combined with health education should be considered.

Congenital toxoplasmosis may develop after maternal primary infection during pregnancy. Since toxoplasmosis in adults is usually asymptomatic, the only way to find the pregnancies at risk of acute toxoplasmosis (i.e. seronegative mothers) is to perform serological screening of all pregnant women. We studied toxoplasma-specific antibodies in 16,733 pregnant women in the first, second, and third trimesters over an 18-month period in the Helsinki area, with a population of 820,700. The participation rate in our study was 90.2% of all pregnancies in the area. The overall prevalence of toxoplasma seropositivity was 20.3%. The incidence of primary infection was 2.4/1000 pregnancies at risk. Our data on incidence suggest an annual occurrence of 131 cases of primary toxoplasma infections during pregnancy in Finland. Primary toxoplasma infection appears to be a significant risk to the fetus even in countries where the prevalence of toxoplasma seropositivity is low. The feasibility of mass screening for toxoplasma infections during pregnancy should be considered in order to reduce the morbidity and mortality due to congenital toxoplasmosis.

Existing serological methods for diagnosing congenital toxoplasmosis are inadequate. We have therefore characterized the features of peripheral blood cell counts and smears in a prospective study of 8 affected infants during their first year of life. Enlarged, vacuolated lymphocytes were observed in all patients. Six patients had periods of neutropenia; in 1 patient the neutropenia was severe and prolonged. A bone marrow aspirate from this patient showed enhanced myelopoiesis, and after stimulation with hydrocortisone, but not with adrenaline, his neutrophil count normalized. Phenotyping of his bone marrow cells revealed that approximately 55% of both the immature and mature B lymphocytes were positive for the cALL antigen. Of the 8 patients, 6 had mild eosinophilia, 4 had mild monocytosis and 3 had increased numbers of plasma cells in the peripheral blood. These findings may reflect the activity of the congenital toxoplasma infection and may thus contribute to the diagnosis, particularly in patients with silent serology.

16,733 pregnant women were studied for toxoplasma specific antibodies during an 18-month period. The number of specimens was 44,181. The IgG seropositivity of mothers was 20.3%. The incidence of primary toxoplasma infections during pregnancy was 4.2 per 1000 seronegative pregnancies by using the traditional criteria, IgG seroconversion and/or a positive IgM. By using the IgG activity test as an additional criterion, the incidence was 2.4 per 1000 seronegative pregnancies. Due to transmission rate of 40%, the number of congenital toxoplasma infections in Finland is more than 50 per year. The evaluation is going on and the cost-benefit analysis will reveal the effectiveness of antenatal screening.

10,288 fish specimens of 34 species from three water bodies in northern Finland were studied mainly in 1978-1982 Triaenophorus nodulosus and T. crassus parasites. Six of the 31 species from the Bothnian Bay were found to harbour T. nodulosus plerocercoids, four of the 11 from the cold, oligotrophic Lake Yli-Kitka in northeastern Finland and only one of the 6 from the small, eutrophic Lake Kuivasjärvi. The ruff (Gymnocephalus cernuus) was most essential intermediate host in the lakes, as supported by stomach analysis of predator fish. Although the highest prevalences were found in adult burbot (Lota lota) in two of the areas, these fish are more likely a blind end in the life cycle of T. nodulosus in the present case. T. crassus larvae were found only in three coregonid species and once in the intestine of a lamprey (Lampetra fluviatilis) from the sea. Neither the prevalence nor the intensity of infection in most of the intermediate fish hosts of T. nodulosus was seen to increase with the length of the fish. The only exception was the ruff in Lake Yli-Kitka, where a sharp increase was encountered. No prominent seasonal variation in Triaenophorus larvae infections was found in any of the cases. The prevalence of T. nodulosus infection in its final host, the pike (Esox lucius), was highest in the sea (93%) and lowest in the eutrophic lake (47%). Seasonally, the lowest T. nodulosus infections were found in June-July in the two lakes. A clear maturation cycle was also found, with the youngest worms in the summer months in all cases. T. crassus was found in every third pike in the sea and its proportion in relation to T. nodulosus is higher in the smallest and largest fish. In only 12%t of the pikes did the number of T. crassus exceed that of T. nodulosus, however, the mean ratio being 1:13 to favour of T. nodulosus. The results give an indication that the composition of the fish fauna in each water body has a considerable influence on the T. nodulosus burden and its distribution among its potential intermediate fish hosts. With the most stable environmental conditions and the greatest variety of fish species, the parasite burden in the Bothnian Bay is most evenly distributed among the 6 intermediate hosts. The fewer fish species occur in the water body, as in the present eutrophic lake, the more the significance of a few or even one intermediate host will increase.