Gastrointestinal (nematode) infections in small ruminants : epidemiology, anthelmintic efficacy and the effect of wattle tannins.

Abstract

Nematode parasites have become the biggest problem for small ruminant production in South Africa due to their resistance to the commercial anthelmintics. Notable, wattle tannin has been used as an alternative strategy for control. However, the concentration and the frequencies can likely influence its effect on the parasites control. The objective of this study was to determine the degree of pasture infestation and nematode infection in sheep and goats, as well as investigate nematode resistance to the anthelmintics, and the potential of wattle tannin in nematode control. The first study dealt with the epidemiology of internal parasites. Eight Merino ewes and eight Nguni does averaged 7-18 months of age were observed for 1 year during the months of February 2008 to January 2009 at the University of KwaZulu-Natal Research Farm (Ukulinga). Egg count per gram (EPG) and coccidian oocysts per gram (OPG) were counted according to Mc Master Technique (Hansen & Perry, 1994) by magnifying parasitic eggs from monthly rectal faecal samples dissolved in saturated sodium chloride. Faecal samples also were cultured for 15 days to identify infective nematode larvae (L3) using Baermann technique. Herbage samples were collected monthly from four paddocks as well to count L3 on the pasture. Sheep live weight was also recorded monthly. Seasonal effects was significant (P<0.05) on the EPG, OPG, faecal culture L3 and pasture L3. A higher level of infection was observed in summer (wet) than in winter (dry season). Trichostrongylus spp larvae were the most prevalent larvae (26.5%) while Strongyloides, Haemonchus contortus, Nematodirus and Cooperia spp occurred in the faecal culture by percentage of 20.9%, 16%, 16% and 14.5%, respectively. For parasite resistance, Ivermectin 1% (IVM), Closantel 5% (CST) and a combination of Abamectin 0.08% and Praziquantel 1.5% (CPA) were evaluated. Twenty four sheep (12 females and 12 males) aged between 7-18 months were used for 21 days. Animals were naturally infested by gastro-intestinal parasites. EPG and faecal culture L3 were counted on day 0, 7, 14 and 21. Closantel was the most effective. Haemonchus spp. were least affected whilst Trichostrongylus spp. were the most affected by all drugs. In the third study, wattle tannins were evaluated as an alternative nematode control drug. Three experiments (Exp.) were conducted to determine the effect of tannin concentration (Exp.1 and 2) and frequency (Exp.3) on nematode parasites. In Exp.1, 0, 0.8, 1.6 and 2.4 g tannin/kg BW were drenched for three consecutive days per sheep (16 females and 8 males, aged 8-9 months) for 21 day. In Exp.2, 30 sheep (14 males and 16 females, aged 9-18 months) were randomly allocated into three tannin treatments (0, 0.8 and 1.6 g tannin/kg BW) and drenched for a day. In Exp.3, 26 sheep (11 males and 15 females aged 9-18 months) were divided into three groups of 9, 9, and 8 sheep each. These groups were drenched with 1.6 g tannins/kg BW/day; once, twice or thrice for the 3 groups respectively. For the three experiments, EPG and L3 larvae were counted in individual feacal samples. For all tannin treatments, EPG decreased (P<0.05) over time. Though the differences among tannin levels and frequencies varied (P<0.05) over time, EPG consistently decreased with increasing tannin level and frequency. Thus 1.6 and 2.4 g tannin /kg BW for 3 consecutive days had nearly similar effects on the EPG. The results of this study are rather inconclusive that weather conditions such as rainfall had a direct effect on internal parasites development. Nematode parasites at Ukulinga Research Farm were resistant to the commercial anthelmintics used. Drenching with 1.6g wattle tannin/kg BW over three successive days is enough to reduce EPG and reduce the degree of pasture contamination.