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At least 829 records · Page 46Linked to original sources
PubMed1998

Eosinophil-mediated killing of Haemonchus contortus larvae: effect of eosinophil activation and role of antibody, complement and interleukin-5.

Eosinophils have previously been shown to accumulate around the tissue invasive (L3) stage of sheep gastrointestinal parasites in vivo. In this study, eosinophils obtained from mammary washes of sheep, were shown to immobilize and kill H. contortus larvae in vitro in the presence of antibody specific against a defined L3 surface antigen. Eosinophils obtained from sheep primed by repeated infusion of H. contortus larvae were more effective than eosinophils obtained after a single infusion of parasite extract in Fasciola hepatica infected ewes suggesting the former were activated in vivo. The level of larval immobilization in the presence of antibody was significantly increased when complement was added to cultures containing activated eosinophils. The addition of interleukin-5 to larval cultures containing antibody and complement resulted in a significant increase in larval immobilization with unactivated eosinophils suggesting that eosinophil effector function is enhanced following priming with this cytokine. Ultrastructural analysis of the eosinophil/larvae interaction at 6 h of incubation revealed degranulation of adhering eosinophils onto the surface of larvae. By 24 h of incubation, many larvae showed signs of damage and most eosinophils had degenerated. These results suggest that eosinophil-mediated killing may be an effector mechanism for the elimination of L3 H. contortus larvae in immune sheep.

Animals↗
PubMed2002

Characterization and purification of cytosolic and membrane-bound protease(s) in adults of Haemonchus contortus.

The activity of protease(s) was observed separately in cytosolic and membrane-bound protease(s) from male and female Hae monchus contortus (Nematoda: Trichostrongylidae). Different fractions showed optimum protease activity at 37 degrees C, pH 8.5 and 8.0 mg casein concentration. The female fractions had a particularly high activity of protease(s) in comparison with the male fractions, especially of membrane-bound enzymes in the anterior half. Inhibition, activation studies revealed the presence of four kinds of protease(s) in cytosolic and membrane-bound fractions. Protease(s) in different fractions are purified to a greater extent by higher concentrations of saturated ammonium sulphate solution, i.e. ranging from 50 to 65%. The purification study revealed the presence of multiple forms of protease(s) in cytosolic and membrane-bound extracts of H. contortus.

Animals↗
PubMedDate not supplied

Pathological and immunohistochemical study of the abomasum and abomasal lymph nodes in goats experimentally infected with Haemonchus contortus.

Histopathological changes and the distributions of T and B lymphocytes and IgG producing plasma cells were recorded in the abomasum and abomasal lymph nodes of goats 3, 7 and 21 weeks post-infection (wpi) after an experimental infection with H. contortus. The low rate of worm recovery by 3 wpi (5.6%) might have been due to larvae death as suggested by the presence of granulomas in the abomasal mucosa at 3 and 7 wpi, or simply due to a poor larval establishment. Marked increase in the secretion of mucus by mucous cells together with an abundant infiltration of eosinophils, mast cells, CD3+ T lymphocytes, CD79a+ B cells, IgG+ plasma cells and globule leukocytes were recorded in the abomasal mucosa, especially at 7 wpi. Except for the globule leukocytes, this reaction decreased substantially by week 21, suggesting this cell type may have been involved in rejection of adult nematodes. The abomasal lymph nodes showed marked hyperplasia, particularly of CD79a+ B cells and IgG+ plasma cells in all infected goats. These reactions may have been responsible for the reduction in the number of worms found in the abomasum between 3 and 7 wpi.

Abomasum↗
PubMed1999

The response of Nigerian West African Dwarf goats to experimental infections with Haemonchus contortus.

One option for controlling haemonchosis in warm pastoral regions is improvement of resistance by selective breeding. Variation in acquired immunity to H. contortus and immunological correlates of infection were studied in West African Dwarf (WAD) goats. Following exposure to 5000 L3, 63 per cent of the inoculum established but 77 per cent of established worms were expelled by week 5. All infected animals were anaemic (day 14). When exposed to 2000L3, 36 per cent of the inoculum was still present (day 35) with no loss by day 49. Persisting primary infection worms survived a superimposed challenge (day 35), but their growth was slowed and resistance to challenge was significant. Most goats showed eosinophilia and parasite-specific IgG responses to primary infection, but only eosinophilia increased after challenge. No consistent associations were found between parasite burden and any immunological measures of infection, but parasite egg counts showed considerable variation. Overall, our results suggest that resistant genotypes exist among the WAD goat population.

Animals↗
PubMed1979

The incidence of thiabendazole resistance in field populations of Haemonchus contortus on the northern tablelands of New South Wales.

A survey was undertaken to assess the incidence of thiabendazole resistance in field populations of H. contortus in sheep flocks on 40 farms distributed throughout the sheep grazing area of the northern tablelands of New South Wales. Treatment with thiabendazole at 66 mg/kg reduced H. contortus ova output by 96-100% in 18 flocks while in the remaining 22 there was a range of responses down to levels where the anthelmintic was without apparent effect. Factors which may contribute to the high incidence of anthelmintic resistance are discussed and the possibility of widespread resistance occurring in other sheep raising areas is considered.

Animals↗