Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Haemonchus”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 793 records · Page 44Linked to original sources
PubMed1997

The effect of infection with the abomasal nematode, Haemonchus contortus, on the avoidance behaviour of sheep in a motivational-choice test.

The behaviour of immune and non-immune sheep infected with H. contortus and undergoing a variety of experimental treatments was investigated in a motivational-choice test, the arena test. This test evaluates motivational state in sheep by pitting the motivation of test animals to approach a small flock of sheep against the motivation to avoid a human decoy located directly in front of the small flock. Approach distance is decreased by infection in immune ewes but was unaffected by infection in non-immune weaner lambs in the present study. Experimental drug-treatments with the opiate-antagonist nalorphine, the antihistamine chlorpheniramine, and the immunosuppressive glucocorticoid dexamethasone, affected avoidance behaviour but did not shed light on possible mechanisms involved in the changes observed when immune sheep are infected with the parasite. These substances may affect motivational state directly and not through a pharmacological action on processes triggered by infection in immune sheep. Arena tests conducted in immune ewes at 4, 7 and 11 days after challenge infection showed a fluctuating locomotor behaviour, which may arise from either the dynamics of a standard secondary immune response or particular antigens released during larval development. The immune-mediated changes in behaviour in the arena test will have entailed information-processing or cognitive pathways, but it is not known whether they also involved the physiological manifestations of emotion.

Animals↗
PubMed1997

Effects of adult and larval Haemonchus contortus on abomasal secretion.

Abomasal pH and serum pepsinogen and gastrin were increased in parasite-naive sheep by infection with either larval or adult H. contortus. Four sheep received 10000 larvae intraruminally and 9000 adult worms were given directly via an abomasal cannula to another 4 sheep. The latter animals were dosed orally with 0.4 mg kg-1 ivermectin 4 days after worm transfer and their recovery was monitored for a further 8 days. Whereas the presence of adult worms rapidly induced changes in the secretory activity of the abomasum, the early larval stages had minimal effects up to the 4th day post-infection. After either larval or adult infection, the initial hypergastrinaemia began at the same time as the increase in abomasal pH, but serum gastrin continued to increase after abomasal pH had reached a maximum and returned more slowly to normal values after drenching. The increase in serum pepsinogen did not precede those in the other parameters, unlike the earlier hyperpepsinogenaemia which occurs with Ostertagia infection. Three of the 8 infected sheep had no detectable serum pepsinogen increase during the parasitism while showing typical effects on abomasal pH and serum gastrin. The rapidity of the responses to the transfer of adult worms and to their removal by treatment with anthelmintic supports a role for worm excretory/secretory (ES) products which possibly are not produced by the early larval stages. The similarity of responses to H. contortus and O. circumcincta infection suggests the involvement of the same or very similar ES products.

Abomasum↗
PubMed1999

The effects of urea supplementation on production and parasitological responses of sheep infected with Haemonchus contortus and Trichostrongylus colubriformis.

Merino wether lambs were individually confined and fed a basal diet of oaten chaff containing essential minerals which was untreated or contained 3% urea. Within each dietary group animals were orally infected with either 200 H. contortus (H), 1000 T. colubriformis (T) or both species (H + T) thrice weekly or remained uninfected (C). Weight gain, wool production, and parasite burden were measured over a 19-week period. Sheep on the diet containing urea gained more weight, consumed more feed and grew more wool of higher fibre diameter than their counterparts given no urea. On both diets uninfected sheep consumed more feed than infected sheep and the sheep given no urea and infected with both H and T worm species consumed the least feed. Parasitised sheep gained less weight than uninfected control sheep. Sheep with urea in their diet had lower faecal egg counts when infected with H alone or with H and T but there was no effect of urea on egg count of sheep infected with T alone. In contrast, T numbers after slaughter were reduced in sheep fed diets containing urea whereas H numbers were not affected by diet. It was concluded that supplementation with urea can increase resilience to parasitism thereby improving production and also enhance resistance mechanisms against worms in young sheep on low quality roughage diets. These responses can be partly attributed to stimulation of feed intake, presumably due to enhanced ruminal digestion, but also to elevated rumen NH3-N levels which would be expected to have increased rumen microbial protein synthesis and availability to the intestines.

Abomasum↗