Strain, S.A.J. and Stear, M.J. (2001). The influence of protein supplementation on the immune response to Haemonchus contortus. Parasite Immunology, 23: 527-531.

Summary:
A major protective mechanism in lambs against theabomasal parasite Ostertagia (Teladorsagia) circumcincta appears to be the immunoglubulin (Ig)A-mediated suppression of worm growth and fecundity. The present study indicates that IgA may play a similar role in the control of another abomasal parasite Haemonchus contortus . Hampshire Down lambs were offered one of two diets: (i) a basal diet and (ii) a diet supplemented with additional protein. Lambs were then `trickle' infected with H. contortus and killed 10 weeks after the start of infection. Those lambs on the supplemented diet had shorter adult worms and produced significantly more antiparasite IgA. There was a significant association between reduced female adult worm length and increased IgA against third-stage larvae. Most of the difference between the two groups in worm length could be accounted for by differences in IgA responses. Therefore, IgA may be the major mechanism controlling fecundity of H. contortus and the magnitude of the IgA response is influenced by the quality of the diet.

J. M. Mugambi, S. W. Wanyangu, R. K. Bain, M. O. Owango, J. L. Duncan, M. J. Stear. (1996). Response of Dorper and Red Masai lambs to trickle Haemonchus contortus infections. Research in Veterinary Science, 61, 218-221.

Summary:
Six-month-old red Maasai lambs were more resistant than Dorper lambs to repeated infections at one to two week intervals with 1000 Haemonchus contortus infective larvae. Resistance after infection was assessed by means of faecal egg counts, packed cell volumes, eosinophil counts, total serum protein concentrations and mortality rates. The weight gains of the infected animals were only marginally lower than those of their uninfected controls, most probably because of their significantly higher feed consumption, and evidently the infected lambs were not utilising all of the extra feed for growth. This absence of anorexia in spite of the infection was probably due to the palatability of the high protein diet fed to the lambs.

J.M. Mugarnbi, R.K. Bain, S.W. Wanyangu, M.A. Ihiga, J.L. Duncan, M. Murray, M.J. Stear. (1997). Resistance of four sheep breeds to natural and subsequent artificial Haemonchus contortus infection. Veterinary Parasitology 69, 265-273

Abstract:
The response of Red Maasai sheep to natural and artificial Haemonchus contortus infections was compared with sheep of Blackheaded Somali, Dorper and Romney Marsh breeds. Significant breed differences in egg count, packed cell volume (PCV), and mortality rates showed that the Red Maasai sheep were more resistant to natural H. contonus infection than sheep from the other three breeds. Of the initial groups of 15 wethers of each breed, two animals from each of the Dorper and Blackheaded Somali groups and nine from the Romney Marsh group died with haemonchosis during a 12 month field study. Following artificial infection of the Red Maasai, Dorpers and Blackheaded Somalis, with 10000 H. contortus L3, the Red Maasai sheep maintained a lower egg output and a higher PCV than animals of the other two breeds. The results clearly showed that breed substitution with the Red Maasai is a control option in areas where sheep are kept for meat and H. contortus is endemic.

Wanyangu, S.W., Mugambi, J.M., Bain, R.K., Duncan, J.L., Murray, M., Stear, M.J. (1997). Response to artificial and subsequent natural infection with Haemonchus contortus in Red Masai and Dower ewes. Veterinary Parasitology 69, 275-282.

Abstract:
Maiden Red Maasai and Dorper ewes were kept indoors and artificially infected with a single oral dose of 5000 infective larvae of Haemonchus contortus. Their faecal egg counts (FEC) andpacked red cell volumes (PCV) were monitored for 9 weeks. They were then treated with ananthelmintic and turned out to graze together on a pasture contaminated with H. contortus. Theygrazed this pasture for 14 months and were allowed to mate and lamb. While at pasture the ewes were monitored for FEC, PCV and peripheral eosinophilia. Red Maasai ewes had significantly lower FEC, and for certain periods, significantly higher PCV and peripheral eosinophilia. During the periparturient period, FEC were about twice as high in the Dorper breed as the Red Maasai. These results confirm and extend previous reports on the superiority of the Red Maasai breed in East Africa .

Stear M.J., Bairden K., Duncan J.L., Eckersall P.D., Fishwick G., Graham P.A., Holmes P.H., McKellar Q.A., Mitchell S., Murray M., Parkins J.J., Wallace D.S. (2000). The influence of relative resistance and urea-supplementation on deliberate infection with Teladorsagia circumcincta during winter. Veterinary Parasitology 94, 45–54.

Abstract:
The consequences for lambs of infection over the winter with Teladorsagia circumcincta were quantified by deliberate, trickle infection of selected animals at 7 months of age. Infected and control uninfected animals were each allocated into four groups, relatively resistant animals on a normal diet, relatively resistant animals on an isocaloric diet supplemented with urea, and relatively susceptible animals on the same two diets. Resistance and susceptibility was assessed by faecal egg counts following natural infection during the summer preceding the deliberate infection. During the deliberate infection egg counts remained low and most parasites recovered at necropsy were inhibited larvae. Nonetheless, infection reduced weight gain, decreased albumin and fructosamine concentrations and provoked a noticeable pepsinogen and eosinophil response. As most larvae were inhibited these responses may have been largely a consequence of immuno-inflammatory responses in the host rather than the direct action of parasites themselves. Relatively resistant animals on the supplemented diet allowed fewer larvae to establish and had higher fructosamine concentrations, higher albumin concentrations and decreased pepsinogen responses. Therefore, a combination of relatively resistant sheep and nutritional supplementation appears most efficient at controlling infection.

J. M. Nginyi, J. L. Duncan, D. J. Mellor, M. J. Stear, S. W. Wanyangu, R. K. Bain, P. M. Gatongi. (2001). Epidemiology of parasitic gastrointestinal nematode infections of ruminants on smallholder farms in central Kenya. Research in Veterinary Science, 70, 33–39.

doi:10.1053/rvsc.2000.0438, available online at http://www.idealibrary.com

Summary:
In order to establish the infection pattern with gastrointestinal nematodes in ruminants in the central Kenya highlands, a study was carried out in 58 smallholder farms. The study involved monthly faecal examinations from sheep, goats and cattle and pasture sampling from eight communal grazing areas. Each month, six Dorper worm-free tracer lambs were introduced and four locally grazed cross-bred sheep were purchased for parasite recovery. The mean faecal egg counts ( FEC ) for cattle were low throughout the study period, whereas those for sheep and goats showed a seasonal pattern with high levels of infection occurring during the two main rainy seasons, especially in March, April and October. There were significant differences in egg counts over time and among farms. Haemonchus contortus was the most prevalent nematode in the tracer lambs whereas the previously exposed locally grazed sheep had significantly lower numbers of H contortus but significantly higher numbers of Trichostrongylus species The highest levels of infection in the tracer lambs occurred in November 1995 and January, May and June 1996. Based on this study, it is now possible to explore the possibility of using strategic treatments for the control of parasitic gastroenteritis in this area of Kenya .