Same Problem: Different Part of the World
Dr. Enrique Nelson Escobar
Small Ruminant Specialist
Univerity of Maryland Eastern Shore
Last month’s “Timely Topic” article written by Dr. Ray Kaplan indicated that worms' resistance to commercial anthelmintics has reached such a troublesome level that combination(s) treatment is/are the best method for using dewormers on small ruminant farms. By the way, such article is a must read for those involved in educating farmers and other livestock specialists (http://www.wormx.info/combinations).
Outside the United States, where sheep and goats are basal to the economy and survival of rural communities, gastrointestinal parasites are a major constraint, along with other diseases, such as malnutrition. There is also a general lack of parasite resistant breeding stock. When reading and investigating about gastrointestinal parasites affecting small ruminants, it helps keeping in mind Dr. Gareth Bath’s “BIG FIVE” holistic approach (http://www.sheepandgoat.com/southafrica). In the following reported studies, there is one or two of such principles that come to mind…can you find them?
Mbuh et al., (2008) cited Haemonchus contortus as the most prevalent species (94.23%) in sheep and goats in the South West Province of Cameroon, West Africa. Additionally, he reported that strongyle infections were more prevalent in sheep than in goats (96.25% vs. 86%, respectively). The highest prevalence of fluke was in December (29.73%). It is particularly interesting that the most widely practiced management system is tethering; therefore, during the rainy season, the environmental conditions favor larvae survival, contaminating the limited pasturing area each animal is allocated to.
In Ethiopia, 23.6 million sheep are a significant source of nutritional protein and revenue for the citizens (Bersissa and Ajebu, 2008). Similar to the report from Cameroon, in Hawassa, nematodes are the primary factor challenging sheep productivity (stunted growth, poor feed utilization, treatment cost, and mortality) along with nutrition and general sanitation. Hawassa is located 275 km south of Addis Ababa (latitude and longitude of 7°3′N-38°28′E and an elevation of 1,708 meters above sea level), with an average rainfall of 801 to 1, 000 mm.
Bersissa and Ajebu (2008) conducted a sheep farmer survey and a research project at the College of Agriculture-Hawassa University with 105 male Arsi-Bale sheep, 6 to 8 months of age, to evaluate the efficacy of albendazole, tetramisole and ivermectic. Fecal egg counts (using the modified McMaster protocol) were performed on day 0 and on the 12th day after administration of the treatments to calculate values for Fecal Egg Count Reduction Test (FECRT %). The sheep were separated by treatment, kept in a pen and fed Rhodes grass hay (Chloris gayana) supplemented with Egyptian pea hay (Sasbanian sesban) hay with water and mineral ad libitum.
The survey indicated that participating farmers selected anthelmintics by price (50%), color (27%, green was the preferred color), recommendations by a veterinarian (13%) and ease of application (10%). Other important information provided by the farmers was that they did not have any “preventive” practice(s), and they treated sheep that are very sick or fail to thrive. Additionally, the sheep owners reported that they did not have knowledge of dewormer rotation”. In this study, the three anthelmintics reduced > 95% the fecal egg counts of the naturally infected sheep.
Tibe et al. (2013) investigated several forage plants in Botswana which contain condensed tannins and how the extracts affect worm egg hatching, larval development, or larval migration patterns in vitro. Five plants were extracted, red-berry mistletoe (Viscum rotundifolium), Viscum verrucosum, lighting matches (Tapinanthus oleifolius), Velvet raisin (Grewia flava), and Ipomoea sinensis. Three gastrointestinal sheep parasite nematodes were evaluated in this project: Haemonchus contortus, Trichostrongylus culibriformis and Teladorsagia circumcincta. Ground leaves from the plants (freeze-dried) were initially extracted with acetone, water and ascorbic acid. After several concentration steps, the condensed tannins content in each extracts was determined.
Results from the anti-parasitic assays indicated that the plant extracts had a lack of anti-parasite activity for egg hatching and larval development. Only G. flava extracts inhibited larval development of T. circumcincta. In the larval migration inhibition assay in vitro, only condensed tannins isolated from G. flava and T. oleifolius inhibited larval migration. The other plant extracts did not show any effect on larval migration. The reasons associated with condensed tannings preventing parasite larval development in-vitro are not clear. Tibe et al. (2013) suggest that condensed tannins might bind with nutrients in the nearby space around the larvae and interfere with availability promoting larval mortality or worm larvae starve because condensed tannins prevent bacterial growth.
Bersissa, K. and N. Ajebu. 2008. Comparative efficacy of albendazole, tetramisole and ivermectin against gastrointestinal nematodes in naturally infected sheep in Hawassa, southern Ethiopia. Revue de Medecine Veterinaire. 159:593-598.
Mbuh, J.V., K.J.N. Ndamukong, N. Ntonifor and G.F. Nforlem. 2008. Parasites of sheep and goats and their prevalence in Bokova, a rural area of Buea Sub Division, Cameroon. Veterinary Parasitology. 156:350-352.
Tibe, O., I.A. Sutherland, L. Lesperance and D.R.K. Harding. 2013. The effects of purified condensed tannins of forage plants from Botswana on the free-living stages of gastrointestinal nematode parasites of livestock. Veterinary Parasitology. 197:160-167.