M.F. Hussein

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.

The pathology of nasopharyngeal myiasis in Saudi Arabian camels (Camelus dromedarius)

Thirty-two out of thirty-five camels examined at Jeddah and Riyadh slaughter houses were infected with the camel nasal bot Cephalopina titillator. The larvae occurred mainly in the nasopharynx and, occasionally, degenerated larvae were found embedded between the turbinated bones. In the pharynx, the pathological changes included the formation of lymphoid nodules, with central abscesses, at the sites of larval attachment, and a combination of inflammatory, degenerative and reparative processes in other parts of the pharyngeal wall. The nasal cavity was congested and filled with mucus in which some larvae were entangled.

Clinico-pathological studies on naturally-occurring bovine fascioliasis in the Sudan

An investigation was made of the pathological, haematological and biochemical aspects of naturally-occurring bovine fascioliasis in the Sudan. 228 animals infected with Fasciola gigantica and 25 non-infected controls were used in the study. The infected cattle revealed emaciation, typical liver pathology, and, occasionally, lesions in the lung and the pancreas. Analysis of their sera also showed reduced albumin values, increased globulin concentrations and decrease albumin/globulin ratio, in addition to increased arginase activity. The serum iron concentration, on the other hand, was decreased, while the total iron binding capacity increased and the resultant iron saturation values reduced. Haematological findings in the infected animals included reduced erythrocyte counts, decreased haematocrit values, increased mean corpuscular volumes, eosinophilia and decreased neutrophil, lymphocyte and monocyte counts. Other parameters were similar in infected and control cattle.

Prevalence of toxoplasmosis in Saudi Arabian camels (Camelus dromedarius)

Serum samples from 227 Saudi Arabian camels were examined for Toxoplasma gondii antibodies by the indirect haemagglutination test, using a microtitre technique. Agglutinations (greater than 2+) occurring at 1:64 dilution were considered positive. A total of 36 (16%) camels were serologically positive for toxoplasmosis, giving titres ranging between 1:64 and 1:8192. The prevalence was much higher in female compared to male camels and in adults compared to young individuals.

The pathogenesis of experimental Haemonchus longistipes infection in camels

The pathogenesis and clinical signs of Haemonchus longistipes infection were studied in four experimentally infected camels two of which were adults and the other two were young. In the former animals, an acute infection developed, characterized by mucoid diarrhoea, anorexia, anaemia, loss of body weight, oedema of the lower parts of the limbs, general malaise and death at 8-10 weeks post-infection. In the two younger camels, a less dramatic disease was encountered with less severe symptoms and no oedema, but also terminating fatally at 19-20 weeks post-infection. Parasitological, haematological and biochemical parameters were determined during the course of the infection and were mostly comparable with those usually encountered in haemonchosis of other animals.

Immunization of sheep against Schistosoma bovis using an irradiated schistosomular vaccine.

S. bovis is an economically important parasite of cattle and possibly of sheep and other domestic stock in many African and Mediterranean countries. Control of this infection by chemotherapy and mollusciciding is impractical and this has stimulated interest in vaccination. Previous work in sheep with the Central and South African species S. mattheei has led to the development of an effective vaccine which incorporates irradiated schistosomula produced by artificial transformation of cercariae. In the present experiments a similar S. bovis vaccine has been used in sheep. Fifteen 5 month old Border Leicester × Suffolk crossbred wethers were divided into three groups, two were vaccinated with either 10000 or 20000 6 krad irradiated S. bovis schistosomula, and the third kept as unvaccinated controls. All sheep were challenged with 6700 normal S. bovis cercariae. Worm recoveries and tissue egg counts at necropsy showed that vaccination with 10000 irradiated schistosomula produced a reduction of 71% in the mean worm burden resulting from challenge of the controls and the mean densities of eggs in the tissues were reduced by 75–82%. Immunization with 20000 irradiated schistosomula was not more effective. Histopathological observations showed that both groups of vaccinated sheep had much milder lesions in the intestines than the non-vaccinated controls. There was also a clear reduction in the severity of liver lesions in 4 of the 5 sheep given the lower dose of irradiated schistosomula but the livers of sheep vaccinated with 20000 irradiated schistosomula had severe and widespread lesions due mainly to a massive accumulation of eosinophils and other inflammatory cells around the vessels.

Erythrokinetics and albumin metabolism in primary experimental Schistosoma bovis infections in Zebu calves.

Red cell kinetics and albumin metabolism were studied in calves infected with either 100 or 200 Schistosoma bovis cercariae per kg body weight, by the use of 59Fe-labelled transferrin, 51Cr-labelled erythrocytes and 125I-labelled albumin; a third group of worm-free animals acted as controls. The anaemia which developed in the infected calves was shown to be due basically to an accelerated rate of red cell loss from the circulation, and became evident around the seventh week of infection, increased in severity during the following two months, and subsequently subsided. In view of its close similarity to the pattern of faecal egg excretion, it was concluded that haemorrhage into the intestine caused by the exit of eggs was the principal aetiological factor: haemolysis was excluded by the absence of both splenomegaly and hyperferraemia . Erythropoiesis was also accelerated in infected animals, but could not keep pace with the rate of red cell breakdown to which the animals were concurrently subjected. Haemodilution was involved, but not to a significant extent. The hypoalbuminaemia associated with infection was caused by an increased rate of albumin catabolism, and a plasma volume expansion, and was accompanied by marked depletion of all albumin pools, but particularly the extravascular pool. The pattern of albumin catabolism closely followed that of red cell loss, suggesting that passage of plasma as whole blood into the intestine was the basic cause of hypoalbuminaemia. Red cell losses and albumin hypercatabolism were more severe in the more heavily infected group, and although both subsided as egg counts fell, they remained evident even 1 year after infection. This may partly explain the failure of infected animals to regain the weight lost during earlier stages of disease.

The prevalence and pathogenesis of naturally-occurring Haemonchus longistipes infection in Sudanese camels.

Camel haemonchosis is prevalent in the Sudan, especially during the rainy season, with a decrease in prevalence in the dry season possibly due to delayed maturation of the worms. The naturally occurring disease in Sudanese camels is characterized by emaciation, anaemia, oedema of the lower parts of the limbs, eosinophilia, hypoproteinaemia, hypoalbuminaemia, hyperglobulinaemia and eosinophilia, as well as elevated blood urea concentrations.

The pathogenesis of experimental Haemonchus longistipes infection in goats.

Goats are highly susceptible to Haemonchus longistipes and could therefore serve as an inexpensive model to study camel haemonchosis. The course of the disease in goats is similar to that in camels and to H. contortus infection in sheep and goats. Unlike the age-dependency of camel haemonchosis, however, the severity of H. longistipes infection in goats is dose-dependent and varies from mild to hyperacute.

Haemonchus longistipes Railliet & Henry, 1909 in goats in the Sudan

Haemonchus longistipes specimens were collected from experimentally infected Sudanese goats and camels for morphological studies. The specimens from goats were much smaller than those from camels, but their infectivity to camels was not affected by their passage in goats. Goats inhabiting the same areas as camels in the Sudan were found to be naturally infected with H. longistipes, but sheep were not and were resistant to experimental infection.