Clinical pathology of Schistosoma bovis infection in sheep

Acquired resistance in goats following a single primary Schistosoma bovis infection

The course of Schistosoma bovis infection was monitored in West African Dwarf Goats over a 34-week period following primary, experimental exposure (3000 cercariae/animal) and over a 17-week period following challenge exposure (2500 cercariae/animal) of goats harbouring 17-week old primary infection. For comparison, groups of challenge control and parasite-free control animals were monitored. Maximal egg excretion observed from week 8 to 12 following primary infection was accompanied by reduced weight gain, marked anaemia, hypoalbuminaemia and eosinophilia. These changes gradually diminished in parallel with decreasing egg excretion from week 14 onwards. Challenge infection induced neither additional egg excretion nor adverse effects in primary-infected animals. This was in contrast to challenge control animals which revealed the typical course of experimental schistosome infection including a peak of egg excretion, weight gain affection, and associated clinico-pathological changes. It was concluded that goats are capable of mounting an effective regulatory response to single primary S. bovis infection as well as to superimposed homologous challenge infection. Further elucidation of the regulatory response to S. bovis infection in goats are needed in order to determine its possible immunological background and epidemiological impact.

Pathology of Schistosoma curassoni infection in sheep

The gross- and histopathology of natural and experimental Schistosoma curassoni infections in sheep were studied. The data obtained showed that S. curassoni infection in sheep causes only slight clinico-pathological manifestations with preferential involvement of the liver, the lower intestine and the urinary bladder. A variable spectrum of host reaction to the eggs within an individual animal was observed, reflecting the duration of presence of eggs in the organs. In the liver, egg granulomas were most numerous in the perilobular regions, while in the intestine, lesions were most pronounced in the mucosa of the rectum. The presence of eggs in 10% of the urinary bladders examined indicated some bladder involvement.

The pathogenesis of experimental Schistosoma bovis infections in Sudanese sheep and goats

The pathogenic effects of experimental Schistosoma bovis infection in Sudanese sheep and goats were investigated by a variety of clinical, parasitological, physiological and histopathological techniques; uninfected animals of each species were used as controls. Infected animals of both species lost or failed to gain weight and developed a haemorrhagic diarrhoea, inappetence, marked anaemia, hypoalbuminaemia, hyperglobulinaemia, hyperproteinaemia and eosinophilia. These changes first became noticeable around the time of onset of oviposition and their severity was generally related to faecal egg counts. Red cell breakdown and albumin catabolism were much higher in infected than in control animals of the same species, and it was concluded that these changes were due to haemorrhage resulting from the extrusion of large numbers of eggs through the intestinal mucosa. Although all the animals were infected with the same number of cercariae, both the number of worms reaching maturity and the tissue egg counts tended to be higher in sheep than in goats. On the other hand, goats had significantly higher faecal egg counts than sheep and it is suggested that this was the reason for the generally more severe disease in the former species.