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Continual cultivation of Toxoplasma gondii in monolayers of HeLa cells has been performed for 6 years. The toxoplasmas were then used for serial cultivation experiments. While searching for optimal conditions for toxoplasma inoculation it was found that infected HeLa cells which were scraped off the glass were a more suitable inoculum than those released by trypsinization. The optimal dose was one zoite per 12 host cells, medium level height at adsorption 2 mm and adsorption time 90 min at 37 degrees C. The concentration of sodium bicarbonate ranging from 8.7 to 26.1 mM had no effect on the multiplication of toxoplasmas. In serial passages in Roux bottles, when the medium was changed every 2-3 days, the average yield of toxoplasmas was 6.2 X 10(6) per ml of medium (after the second change of medium, i.e., 7 days after inoculation). The toxoplasmas obtained in serial passages were suitable for purification studies, for preparation of small amounts of antigens and as an inoculum for suspension cultures.

The properties of alkaline phosphatase present in Taenia crassiceps cysticerci were studied. Approximately a half of the total activity was free and the remaining part was bound to membranes. Kinetic studies did not show any differences between the free and bound alkaline phosphatases. It was found that high substrate concentrations produced an inhibitory effect on the enzyme. This effect was much greater at lower pH. pH optimum changed with the concentration of the substrate.

While studying the suslik fleas in artificial nests planted in free nature, significant changes in the population dynamics of N. setosa, C. simplex and C. orientalis (from the spring build up to the autumnal peak and the decrease of flea number until the next spring) were noted. The predominance of females in the spring period was recorded in N. setosa. Significant seasonal changes in the number of engorged females of N. setosa and C. simplex and of C. orientalis males (the increase of engorged specimens in the spring and summer) were demonstrated. A significant predominance of females with mature eggs in the spring and summer and their negligible number in the autumn were found in N. setosa and C. simplex.

Small mammals trapped in seven sites along the river Sava in Croatia were examined for leptospiral infection by renoculture and serological methods. Of the 1749 animals caught 702 were examined by renoculture method and 626 were tested by microagglutination-lysis. The dominant animals species caught were Microtus arvalis (672 animals) and Apodemus agrarius (552 animals). Of the 115 strains of leptospires isolated the dominant serotypes were L. grippotyphosa (40) and L. pomona (35). Five strains of L. sejroe, 9 strains of L. australis, 1 strain of L. bataviae and 25 undetermined strains were isolated, the infection rate ranging from 3 to 32%. Serologic evidence of infection was demonstrated in 91 animals, the prevalence ranging from 0 to 43% of animals depending on the trapping site. Specific agglutinins most frequently encountered were those against L. pomona (50) and L. grippotyphosa (26), though agglutinins against L. jalna (5), L. bataviae (4), L. bratislava (3) etc., were also found. A high degree if association between L. grippotyphosa and the common vole as well as between L. pomona and the field mouse was found indicating that as far as these two types of leptospires are concerned the Sava valley may be considered as their vast natural focus. It was also concluded that wild small mammals in this region of Croatia may be a source of leptospiral infection for the local population as well as for outdoor-reared domestic animals (swine, bovine).

The pathological picture of the migration phase of C. tenuicollis in pigs is characterized by a haemorrhagia within the liver parenchyma and under the liver surface. The haemorrhagia, which represents a migrational canal, is induced by the destruction of liver sinuses by migrating larvae. Approximately on day 10 p.i. a serofibrinous peritonitis occurs and free cysticerci appear in the exudate. On days 14-16 p.i. the exudative peritonitis may increase. The cysticerci are localized under the serosas or on them. On about day 10 p.i. even the pulmonary form of the disease may occur. On day 13 p.i. the cysticerci are present in the lumen of lung arteries or they migrate out of them. The changes in the lungs and on the pleura, as well as their dynamic changes, are identical with the changes in the liver and on the peritoneum. The period on days 21-24 p.i. is characterized by extensive synechiae of serosas and the cysticerci are firmly attached to the serosas. On day 35 p.i. the connective tissue adhesions persist and many of the cysticerci exhibit dystrophic changes or are dead and often already calcified. The wall of the pseudocyst, in which the cysticercus is situated, consists of the fibrocytes and serosa, and its cavity is not lined with endothelium, as it is the case in C. bovis and C. cellulosae.