Schistosomiasis in hamsters: the relationship of egg concentration in the liver to disease

The host-parasite relationship of Schistosoma haematobium in CBA mice

The host-parasite relationships of two geographical isolates of Schistosoma haematobium in CBA mice are described and compared to previous reports on this parasite in other experimental hosts and in man. The mean percentage establishment of worms in mice was 17% and was not affected by the age or sex of the host. Adult worm burdens remained constant over 20 weeks, but were reduced after 18 months of infection. Male and female worms reached mean maximum lengths of 4.78 and 5.9 mm respectively. Egg laying commenced 9.5 weeks after infection and eggs accumulated in the tissues throughout the period of infection. A large increase in the rate of egg accumulation occurred coincidental with the appearance of eggs in the bladder of some mice. Faecal eggs were first observed in some mice at 12.5 weeks and most mice excreted a few eggs by 17 weeks p.i. (post-infection). Eggs were not found in the urine of infected mice. Excreted eggs and eggs isolated from the livers of infected mice hatched, but the resulting miracidia were unable to infect appropriate snail hosts. The development of hepatic granulomas and egg-induced pathology in the bladder of mice is described.

Schistosomatium douthitti: biochemical and morphological effects of an experimental infection in mice

The pathophysiological changes that occur in mice experimentally infected with Schistosomatium douthitti were studied. Male ICR mice, 6-8 weeks in age, were exposed to 100 cercariae of S. douthitti from infected snails (Lymnaea catascopium) and sacrificed weekly for a total of 13 weeks. Liver homogenates, serum samples, and histological sections of liver tissue were examined. Results showed that body weights of animals with prepatent infections were higher than those of corresponding controls. After patency, which occurred at 5 weeks, body weights were lower and liver weights were higher resulting in significantly increased liver weight/body weight ratios. Hematocrit values declined progressively in patent infections. Total cholesterol in liver was generally higher in the parasitized groups reaching significance during patency. Values rose with age in both control and parasitized groups, but sooner in the latter. Free cholesterol was increased in the liver of animals with patent infections. Total lipid content of the liver was reduced in the infected animals throughout the study. Both liver glycogen and serum glucose levels in the infected animals rose over the control values. The activity of alkaline phosphatase (E.C.3.1.3.1) was elevated in liver tissue of infected mice. Glutamic-pyruvic transaminase (E.C.2.6.1.2) activity was higher in serum but lower in the livers of animals harboring patent infections. Total bile salt concentration in parasitized animals did not differ appreciably from control values; however, gallbladders were enlarged five times in the infected animals. Histologically, liver sections from infected mice showed granulomas in various stages of formation and degeneration. Granulomas contained from 1 to 40 schistosome eggs. After 6 weeks of infection, granulomas were characterized by many neutrophils and monocytes. Few lymphocytes and eosinophils were present. As the granulomas developed, fibroblasts and connective tissue became more prominent. Glycogen deposits were observed surrounding granulomas and were increased in older infections. Adult worms contained abundant amounts of glycogen and cholesterol in their parenchymal tissues.

Culture of Schistosoma haematobium in vivo and in vitro

The maximum rate of development of Schistosoma haematobium in the hamster was determined by examination of the most advanced worms recovered at short intervals throughout the course of development. In culture S. haematobium developed at the same rate as in the hamster up to day 31 when pairing first occurs and male worms produce some spermatozoa. In vitro males formed some spermatozoa but pairing did not take place and, probably for this reason, females did not complete sexual maturation as occurs in the host between days 57-65. Somatic growth continued in vitro and at 70 days male worms had achieved almost the same length as in the hamster at this time. The culture medium, previously used for S. mansoni, consisted of equal volumes of serum and Earle's balanced saline with a final concentration of 0.25% lactalbumin hydrolysate, 100 units/ml penicillin, 100 mug/ml streptomycin and 1% rbc. The best culture results were obtained with one particular human serum; seven other human sera gave a wide range of growth support. The samples of baboon, rhesus monkey or foetal calf sera tested provided little or no growth support but prolonged survival was possible in all the sera.

Stimulation of hamster and human lymphocyte cultures by soluble egg antigens (SEA) of Schistosoma haematobium and S. mansoni

Soluble egg and adult worm antigen preparations of Schistosoma haematobium and S. mansoni were tested in hamster and human lymphocyte cultures. Primed lymphocytes from infected donors showed a marked blastogenic response to the homologous antigens. A cross-reactivity to the heterologous antigens was seen especially in S. mansoni infected hamsters.