Effect of anthelmintic treatment on the performance of Awassi sheep in Iraq

Effect of gastro-intestinal nematode infection on sheep performance: a systematic review and meta-analysis

Background

Gastrointestinal nematode (GIN) infections are common in domestic sheep and impact directly and indirectly on the health of infected animals as well as on the associated economic production. In this study, we aim at summarizing the current knowledge on the influence of GIN infections on sheep production by conducting a systematic review. A subsequent meta-analysis of relevant studies was performed to provide an estimate of the effect of GIN infections on weight gain, wool production and milk yield.

Methods

A literature search was performed on the CAB, Pubmed and Web of Science database for the period 1960–2012. Inclusion criteria were: 1) Measurement of at least one production parameter. 2) Comparison between groups of sheep with different nematode burdens. 3) Same conditions regarding all aspects except parasite burden between groups. 4) Quantitative measurements of one or more production traits.

Results

Altogether, 88 studies describing 218 trials were included in this review. The majority of studies (86 %) reported that GIN infections had a negative effect on production but this was reported to be statistically significant in only 43 % of the studies. Meta-analysis indicated that performances of sheep infected with nematodes was 85, 90 and 78 % of the performance in uninfected individuals for weight gain, wool production and milk yield respectively. Our results suggest a possible reporting bias or small study effect for the estimation of the impact of GIN infections on weight gain. Finally, a general linear model provided an estimate for the decrease in weight gain in relation to the increase in faecal egg count of nematodes.

Conclusion

This study underlines the importance of GIN infections for sheep production and highlights the need to improve parasite management in sheep, in particular in face of challenges such as anthelmintic resistance.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-1164-z) contains supplementary material, which is available to authorized users.

Development and survival of Haemonchus contortus larvae on pasture in Iraq

The survival of Haemonchus contortus infective larvae on pasture and soil was studied over a period of 12 months in the Baghdad area. Infective larvae were found on herbage and soil at all times except in the summer months. During autumn and winter infective larvae in pasture survived for periods of up to 32 weeks. Little larval migration into soil was observed during this study and larvae did not survive for long in the faecal pellets during the summer.

Epidemiology of gastrointestinal parasites of Awassi sheep in Iraq

Studies on the epidemiology of gastrointestinal nematodes of sheep, conducted at two different farms in the Baghdad area, in 1979, revealed two peaks in worm egg counts in ewes, one in spring and the other in autumn; the latter coincided with the lambing season. Similarly in lambs, two peaks of infection were apparent, but the spring peak was not so well defined. During the hot and dry summer months of Iraq, helminthic infection was at a low level. Faecal culture for larvae and their identification indicated the predominance of Haemonchus contortus infection in the ewes and that of Ostertagia and Trichostrongylus spp. in the lambs examined, Trichostrongylus infection predominating during the hot, dry period of the year. The self-cure phenomenon as well as preparturient rise in egg counts, as reported in other countries, was also observed during this study.