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This study introduced a new method for estimating intestinal tissue Schistosoma japonicum egg counts, based on scraping of the mucosal layer of different sections of the intestines. Twenty-eight Danish Landrace/Yorkshire/Duroc crossbred pigs were divided into 3 groups of 15, 5 and 8 pigs, respectively. Pigs were fed either a high- or low- protein diet and were infected by an intra-muscular or per-oral route of infection with doses of either 1,000, 1,500 or 3,000 S. japonicum cercariae. The pigs were killed 9-11 weeks post infection. For all 28 pigs the intestines were divided into 3 sections: cecum, colon and rectum and the entire mucosa was scraped off the serosa of each section and homogenized. Subsequently, samples corresponding to 5 g homogenised mucosal tissue were digested and egg counts were determined and correlated to liver egg counts. In order to compare the relative distribution of eggs in the mucosa and the serosa, small intestinal wall subsamples formerly taken from each section from a subgroup of 5 pigs were homogenized and egg counts determined for both the mucosa and serosa. The number of eggs were significantly higher in the mucosa than in the serosa. Egg counts estimated from digestion of mucosa subsamples either over or underestimated egg counts based on scrapings of the entire mucosa when compared, reflecting the very patchy distribution of S. japonicum eggs in the intestinal wall. Correlating liver egg counts with the number of eggs based on scrapings from the entire mucosa from cecum, colon and rectum, respectively, significant correlations were found for 2 out of 3 groups of pigs. The present study revealed that estimating intestinal tissue egg counts based on scrapings of the entire mucosa is a reliable and convenient approach, nicely supporting the liver tissue digestion approach. In addition, a reduction of the processing time of intestinal tissue in general was achieved due to the very simple scraping technique.

A technique was developed for in vivo labeling of adult Schistosoma japonicum worms using 35S bound to methionine and cysteine. The isotope was applied in an in vivo labeling system in which Oncomelania hupensis snails harboring a patent S. japonicum were individually exposed to the label. Following exposure to cercariae, mice were perfused after 6 wk. For autoradiography and fluorography, the worms were mounted on cardboard, covered with x-ray films, and exposed for 5 wk. With both techniques, images of both male and female worms were obtained in the 1- and 2-microCi groups, but not in the 0.5-microCi group. Fluorography proved more sensitive than autoradiography. Snail survival, labeled cercariae, and worm establishment were not affected by the radiolabeling. 35S was thus found useful for radiolabeling adult S. japonicum worms.

To relate the marked differences observed in morbidity due to Schistosoma mansoni infection in the Kangundo and Kibwezi areas of Machakos District, Kenya with possible parasite-related differences in pathobiological characteristics, a quantitative comparison of the host-parasite relationship in infections in NMRI mice with S. mansoni isolates from the 2 areas was conducted. One hundred and 20 cercariae were used per mouse, and necropsy took place between 35 and 94 days following infection. Parameters assessed comprised worm establishment, tissue egg counts, fecal egg excretion, egg production/worm pair, and weights of liver and spleen. Central findings included a higher worm establishment and a lower egg production/worm pair in Kangundo infections than in Kibwezi infections, comparable total tissue schistosome egg counts, and a higher liver/intestinal tissue schistosome egg ratio in Kibwezi infected mice than in the Kangundo infected mice. In addition, a much higher fecal egg excretion, expressed as eggs/g feces and eggs/g feces/worm pair, was observed in mice infected with the Kangundo isolate of S. munsoni than in mice infected with the isolate from Kibwezi. Although possible limitations in the use of mouse models need be realized, the results provide some support to the hypothesis that parasite-related differences in pathobiological characteristics may at least contribute to the marked difference observed in S. mansoni-induced morbidity between the Kangundo and Kibwezi areas.

Experimental primary and challenge Schistosoma bovis infections were studied in West African Dwarf goats, using clinicopathological and parasitological parameters. The experiment included 44 goats divided into 4 groups of which group A received primary infection, group B received primary and challenge infection, group C received a challenge control infection, and group D included noninfected controls. Primary infection (wk 0) and challenge infection (wk 16) both comprised exposure to 1,000 cercariae per goat, and necropsies took place 16, 22 and 32 wk following primary infection. Clinicopathological effects were moderate in all infected groups. Egg excretion became gradually reduced following peak levels during early primary infection, and egg excretion increased only marginally following challenge infection in the primary- and challenge-infection group. Similarly, challenge infection of primary-infected goats did not result in an increase in tissue egg counts. Worm recovery and tissue egg counts in primary-infected goats remained comparable throughout the experiment, and although evidence was obtained for a delay in maturation, challenge worm establishment was comparable with challenge-control worm establishment. An anti-fecundity effect is thus an essential component of the regulatory response to both primary and challenge S. bovis infection in the goats. However, it was also shown that the intrauterine egg count is an unreliable parameter for fecundity assessments.

Patterns of infection with Schistosoma haematobium were studied in 1991 and 1992 in two, lakeside, resettlement communities at the newly established Oyan Reservoir in Ogun State, Nigeria. Prevalence and intensity of S. haematobium infection and frequency of haematuria and proteinuria all increased markedly from 1991 to 1992, indicating intensive transmission. This was confirmed in an incidence study. In both years, infection patterns were highly age-dependent, with peaks in those aged 10-14 years. These patterns deviate from those seen during a survey carried out in the same communities in 1988, providing strong evidence that infection had changed from an epidemic to an endemic stage. Although sex, tribe, religion, occupation, and village of residence had little if any effect on infection pattern, the patterns in settled and migrant groups differed considerably. The study provided a thorough elucidation of the complexity and instability of transmission of S. haematobium in a resettlement community characterized by social instability and extensive population movements. Although haematuria was very common, the subjects knew little about its cause.

To study the relation between indicators of infection and Schistosoma mansoni and S. haematobium infection, and serum concentrations of zinc, ferritin and retinol.Cross-sectional.313 rural Zimbabwean schoolchildren (144 boys and 169 girls, 11-17 years).S. mansoni and S. haematobium egg output, concentration of C-reactive protein, neutrophil count, questionnaire data on fever and diarrhoea, and serum concentrations of retinol, ferritin and zinc.Age, elevated CRP, fever and S. mansoni egg output were significant predictors of the concentration of retinol. The regression coefficient for age was positive, and negative for elevated CRP, fever and S. mansoni egg output. As S. mansoni, but not S. haematobium, was of significance, it is unlikely that low retinol level increased susceptibility to infection. The effect of S. mansoni on retinol level was 0.03 mumol/l (95% CI: 0.002-0.06, P = 0.03) for each 100 eggs/g increase in egg output. Neither indicators of infection nor age and sex were predictors of concentration of zinc and log10 concentration of ferritin.S. mansoni infection reduced retinol level, when indicators of infection and age were controlled for. High intensities of S. mansoni infection may induce vitamin A deficiency among children with marginal vitamin A status. The study emphasizes the importance of controlling for age and metabolic response to concurrent infections in studies using serum retinol as a measure of vitamin A status.

The overall prevalences of infection with Schistosoma mansoni, S. haematobium or both species among 6122 children from 27 schools in the former White Nile Province of Sudan (now divided into the Kosti, El Getaina, El Gebelein and El Duem Provinces) were 10.1%, 21.4% and 4.5%, respectively. Geometric mean egg counts in the pure S. mansoni and pure S. haematobium infections were 97.7 eggs/g faeces and 12.9 eggs/10 ml urine, respectively. There were marked differences in levels of endemicity between provinces and also between schools within each province. School-specific prevalences and intensities of infection were positively correlated, both for S. mansoni and for S. haematobium. Prevalences and intensities of infection were generally similar in male and female subjects and in the different age groups into which they were split (i.e. 5-9, 10-14 and 15-19 years). Community-based surveys of all age groups in two villages showed typical patterns of infections with S. mansoni and S. haematobium, with indices peaking in those aged 10-19 years, both in males and females. Observations on snail-related aspects of transmission revealed that transmission of both S. mansoni and S. haematobium was highly focal and also seasonal, taking place during the hot, dry and post-rainy seasons.

The endemicity (prevalence, intensity and incidence) of schistosomiasis mansoni and its patterns of transmission (focality, seasonality) were studied in five villages in the Managil irrigation scheme, Sudan. Marked differences between villages were observed in overall prevalence (33.3%-54.8%), intensity (77.3-135.0 eggs/g faeces), incidence (15.2%-57.9%) and age-related patterns of Schistosoma mansoni infections. Overall, prevalence and intensity of infection peaked in those aged 10-14 years and then declined slowly with increasing age. However, there were second, smaller peaks in both prevalence and intensity of infection in the older males (> 40 years) and, in general, the indices of infection for males exceeded those for females. The infection pattern was influenced by occupation and possibly by having a latrine. Transmission of S. mansoni in the Managil irrigation scheme is highly focal and seasonal, taking place in a few major human-contact sites near villages and peaking during the hot and dry season (April-June). The infection and transmission patterns of S. mansoni in the scheme show great resemblance to those in the neighbouring Gezira irrigation scheme.

Human- and snail-related aspects of transmission of urinary and intestinal schistosomiasis were studied in the Tono Irrigation Scheme in northern Ghana. The scheme became operational in 1977. In some schools, prevalences and intensities of both Schistosoma mansoni and S. haematobium infection were alarmingly high, pointing to human schistosomiasis being at least focally a health problem of major public health concern. Positive correlations between intensity of schistosome infection, as measured by egg output, with frequency of visible haematuria and history of haematuria point to opportunities for community-based assessment of morbidity and identification of high risk population subgroups. Bulinus globosus is the most important snail host for S. haematobium while Biomphalaria pfeifferi serves as host for S. mansoni. While transmission of S. mansoni is taking place only in the main canal, transmission of S. haematobium takes place in all parts of the irrigation system (lateral canal, night storage dam, main reservoir). Transmission of both S. mansoni and S. haematobium is rather focal and a seasonal pattern of transmission is indicated with peak transmission taking place during the beginning of the dry season. The high endemicity and the transmission patterns described in this study call for an integrated approach to schistosomiasis morbidity control in the area.

Human- and snail-related aspects of the transmission of schistosomiasis mansoni was studied in the Amor Parish community located at the western bank of the River Nile in the Nebbi District, north-western Uganda. A cross sectional survey involving 642 people revealed an overall prevalence of infection among males and females of 81.6% and 81.3%, respectively. The prevalence of infection peaked in the 10-14 years age group, being 93.2% and 93.6% in males and females, respectively, but the prevalence remained high also in older age groups. Intensity of infection peaked in the 10-14 years age group in males and in the 15-19 years age group in females, reaching 768 and 482 eggs/g faeces, respectively. Intensity of infection diminished only to a moderate extent with increasing age with the infection intensity in the 40+ years age group being 270 and 241 eggs/g faeces in males and females, respectively. Observations on the human water contact pattern revealed a community having a very intensive water contact persisting into old age. Interviews revealed a high level of awareness of the disease schistosomiasis, and 87.2% had a history of passing blood in stool. The total set of observations point to intestinal schistosomiasis being of public health importance in Amor Parish. Studies on snail-related aspects of transmission revealed that Biomphalaria stanleyi was by far the most important snail host in the area. A tendency was seen for B. stanleyi snail numbers to be reduced during the rainy season.

From 1980 to 1989, 575 unicompartmental prostheses were implanted for gonarthrosis in 415 patients. More than half of the prostheses were operated in cases of arthrosis of both knees. In 115 patients, both knees were operated on the same day. Pain relief was very good, and the patients were generally satisfied. There was no loss in follow-up evaluation, even deaths were registered. Clinical and roentgenographic examination was performed at three, six, and ten years, according to the Swedish Knee Project. Of the 575 cases, 1.2% had a change of component during revision surgery, and generally, the same type of prosthesis could be used at revision. In 2.4% of the cases, other secondary procedures were used. More than 90% of the candidates for prosthesis surgery in gonarthrosis had unicompartmental arthroplasty. That included cases with pyrophosphate synovitis, absence of the anterior cruciate ligament, and severe degree of the disease. The status of the ligaments after correction was crucial for a good result. Secondary wear of the contralateral compartment was not a problem. A roentgenographic assessment of the follow-up evaluation by an independent radiologist was considered important, because the material is retrospective.

Superimposing the intestinal tapeworm Hymenolepis diminuta on an established infection with the trematode Echinostoma caproni or simultaneous infection of mice with H. diminuta and Hymenolepis microstoma caused destrobilation and expulsion of H. diminuta, whereas establishment and growth of H. microstoma under the same infection regimes were not affected. In contrast, simultaneous superimposition of H. diminuta and H. microstoma on an established E. caproni infection caused destrobilation and expulsion of both H. diminuta and H. microstoma.

Thirteen cases of nonunion of the humerus were treated by intramedullary reaming and nail fixation. Rigid stabilization which was usual after operating upon other long bones was not always secured in these cases, and supplementary plaster immobilization was necessary. Seven fractures healed and 3 fractures required re-nailing before healing. Three fractures did not heal in spite of reoperation, but in 2 of these cases the nail provided stability and controlled pain and motion at fracture site. Nonunion of the humerus is a difficult problem, irrespective of the method of treatment.

Homologous immunotolerance was demonstrated in Echinostoma revolutum infections in the mouse. High-level infections of about 15 worms were not expelled for a period of at least 61 days following infection, whereas low-level infections of about 10 to 12 worms or below were eliminated completely between day 47 and 61 after infection. A primary, 20- to 33-day-old, heavy E. revolutum infection in the mouse produced a statistically significant increase in the number of Schistosoma mansoni recovered in challenge infections. Worm burdens increased by 65.7 to 90.6% as compared with those of the respective S. mansoni challenge control groups.

Various aspects of the epidemiology of Schistosoma bovis were studied over a one-year period in Iringa Region, Tanzania. An abattoir survey revealed an overall prevalence rate of 30.8% in cattle and 3.8% in goats in the area, and field studies on two dairy farms both providing good opportunities for schistosome transmission provided information concerning the transmission ecology of S. bovis in relation to different types of grazing and water supply. The traditional management system on one farm with a large number of cattle utilizing a limited water resource highly suitable for sustaining populations of the snail host Bulinus africanus resulted in intensive transmission as evidenced by uptake of massive infections in calves and development of resistance to S. bovis challenge in dairy cows. On another farm, appropriate management comprising watering of cattle at a B. africanus-free pond provided the background for less intensive transmission in that transmission risk was confined to occasional contact with water contact sites of secondary importance. Besides, the transmission pattern as regards intensity and seasonality was affected markedly by the geographical and seasonal distribution of the host snail B. africanus. Thus, transmission in canals and temporary ponds was limited mainly to the dry season and the end of the rainy season, respectively, while transmission in permanent ponds occurred intermittently throughout at least most of the year. It is concluded that prevention of severe loss of productivity in domestic ruminants due to schistosome infections should be possible using strategic management procedures provided that essential information is available concerning the pattern of transmission in the particular area.

Experiments were designed to study the effect of Trypanosoma brucei on the expulsion of Echinostoma revolutum and on the development and maintenance of homologous E. revolutum resistance in the mouse. T. brucei given 3, 2, and 1 wk before and 1 wk after infection with E. revolutum completely inhibited the expulsion of the E. revolutum worm burden for a period of at least 6 wk following infection, and T. brucei given 2 or 3 wk after infection with E. revolutum conferred a significant delay in the expulsion of the E. revolutum worm burden. T. brucei given 1 wk before and 1 wk after a primary E. revolutum infection blocked completely the resistance of the mouse to a homologous E. revolutum challenge given 2 wk after the primary infection. A similar blockage of resistance to a homologous challenge was experienced by mice given T. brucei 3 wk after the primary E. revolutum infection and challenged following another 2 wk. The mechanisms underlying the T. brucei-induced interference with the expulsion of E. revolutum and with the development and maintenance of homologous E. revolutum resistance in mice are presumably immunologically mediated.

With the starting point in a comprehensive and integrated longitudinal study conducted by the Blair Research Laboratory from March 1982 to May 1984 in Bushu and Chiweshe communal areas, a review is presented of the dynamics of transmission of urinary (Schistosoma haematobium) and intestinal (S. mansoni) human schistosomiasis in the highveld region of Zimbabwe. The study comprised observations on snail-related aspects of transmission, on human water contact patterns, and on prevalence, intensity and incidence of infection in the human definitive host population. S. haematobium was found to be of high endemicity whereas the endemicity of S. mansoni was moderate. This reflects that Bulinus globosus, the snail host for S. haematobium, is better adapted to the biologically unstable freshwater environments than Biomphalaria pfeifferi, the snail host for S. mansoni. The most essential findings comprise a marked seasonality and focality of transmission, an overdispersed distribution of infection, individual predisposition to infection, peak of prevalence and intensity of infection among children and young adults, a positive correlation between infection status in population subgroup and the relative transmission potential of water contact sites used, a pronounced specificity and marked conservatism in the human water contact pattern. The epidemiological background for schistosomiasis control strategies is outlined, and a community-based strategy within the primary health care system for schistosomiasis morbidity control is described. The community-based primary health care approach to schistosomiasis morbidity control is the strategy adopted in Zimbabwe.

The clinical pathology of Schistosoma bovis infection in sheep was studied for a period of 16 weeks. The length of the prepatent period was 10 weeks, and reduced haemoglobin and packed cell volume values and increased serum gammaglutamyl-transpeptidase levels were observed from eight to 10 weeks after infection and onwards. The bromsulphalein clearance rate was significantly reduced 16 weeks after infection. Eosinophil counts were increased six and eight weeks after infection and towards the end of the experiment.

The viability of a hybrid between male Schistosoma haematobium (Dar es Salaam, Tanzania) and female S. intercalatum (Edea, Cameroun) was studied for up to the F7 hybrid generation and the biological characteristics of the hybrid were compared with those of each of the parental species. Using the total cercarial production/100 exposed snails/5 weeks value (TCP) as an index the hybrid miracidial infectivity to Bulinus forskalii (Kinshasa, Zaire), the host snail for S. intercalatum, remained comparable to that of S. intercalatum for up to at least the F5 generation and the TCP values for the hybrid/B. wrighti combination remained for up to the F7 generation intermediate between those of the parental species in B. wrighti. The hybrid also retained the infectivity for up to at least the F5 generation to B. globosus (Mazeras, Kenya), the host snail for S. haematobium, but the TCP values for the hybrid/B. globosus combination remained consistently lower than that of the S. haematobium/B. globosus combination. The hybrid cercarial infectivity to hamsters was for up to the F7 generation comparable to that of both parental species and the egg production capacity/worm pair/day of production of the F1 hybrid generation exceeded in both hamsters and mice that of both parental species. However, the egg production capacity subsequently decreased with that of the F3 to F6 generations in hamsters and with that of the F2 and F5 generations in mice being comparable to that of S. intercalatum. The pattern of distribution of eggs in tissue of hamsters of the F1 and F2 generations resembled that of S. haematobium and S. intercalatum, respectively, but the distributional pattern of the F3 to F6 generations deviated markedly from that of both the parental species and the preceding hybrid generations. The hybrid cercarial infectivity to mice and the pattern of egg distribution corresponded to that of S. intercalatum. The egg morphology of the P1 generation corresponded to that of S. intercalatum while that of the F1, F2 and F3 hybrid generations exhibited great polymorphism with a range of shapes through those of the parental species but with most eggs being intermediate in shape. However, the eggs of the F4 to F7 hybrid generations exhibited less polymorphism and resembled those of S. bovis in both size and shape.

The pattern of fluctuation in the population size of Bulinus globosus and Biomphalaria pfeifferi, in their infection rates with Schistosoma haematobium/S. mattheei and S. mansoni, respectively, and in the cercarial population size as monitored using hamster immersions, was elucidated in streams in the temperate highveld region of Zimbabwe over a 27-month period during 1982-1984. The results revealed that transmission of S. mansoni was erratic and unpredictable without a clearcut seasonal transmission pattern. In contrast, transmission of S. haematobium and S. mattheei exhibited a marked seasonal pattern, being most intensive during the hot, dry season (September-November) and markedly reduced during the cold, dry season (June-August). During the rainy (December-February) and warm, post-rainy (March-May) seasons transmission was moderate and variable, but occasionally intensive. The results also showed that rodent immersion is to be preferred to measurements of snail population size and snail infection rate in elucidating seasonality of transmission of schistosomiasis.