Agricultural restructuring and gastrointestinal parasitism in domestic ruminants on the rangelands of Kazakhstan

Abstract

In order to evaluate the epidemiology of parasitism in farmed ruminants in the changed agricultural context in Kazakhstan, 505 cattle, sheep and goats were surveyed for gastrointestinal parasitism using coprological examination, and a further thirty sheep and four goats using post mortem extraction of helminths. The dominant helminth genera were Marshallagia, Nematodirus and Trichostrongylus. Haemonchus was also present. Faecal egg counts were low (mean abundance 0–115 eggs per gram in different groups), and there was no relationship between faecal egg density and body condition score. Eggs of Nematodirus spp. were more common in sheep less than 1 yr of age, whereas those of the Trichostrongylidae were generally more common in adult sheep. Based on faecal egg counts, sheep grazing on common land close to permanent human settlements were generally no more heavily infected than those grazing the remote open plains. This could be due to a non-linear relationship between livestock numbers and stocking density. We suggest that cessation of strategic nematode control in the region following post-Soviet agricultural reform was offset by a general reduction in stocking density, such that parasite burdens remained low. However, recovery in livestock numbers is likely to lead to increased levels of infection and production loss unless sustainable control strategies are put in place.

Introduction

Livestock production is the dominant economic activity across much of Kazakhstan. Changes to the structure of the livestock industry since the end of the Soviet period have been particularly marked in the semi-arid central areas, which previously provided a large proportion of the meat and wool for domestic consumption and export (Goskomstat, 1988). After independence in 1991, privatisation of state-owned and collective farms, halting of production subsidies and support, and disintegration of slaughter and marketing infrastructures were associated with marked decreases in livestock numbers and meat production (Suleimenov and Oram, 2000, Robinson and Milner-Gulland, 2003). The total sheep population decreased from 36 million in 1990 to 8 million in 1999, with changes in remote areas especially marked (Robinson and Milner-Gulland, 2003). Co-ordinated movement of livestock also decreased, while withdrawal of centrally provided animal health advice and drugs made effective strategic anthelmintic prophylaxis impossible on most farms. The effects of these complex changes on the epidemiology of gastrointestinal nematodosis in domestic ruminants are difficult to predict. As livestock numbers begin to recover, farm structure and animal husbandry are radically changed (Kerven, 2003), and improved understanding of the epidemiology of gastrointestinal parasites will be important to the future success of livestock production in Kazakhstan. In addition, the effects of stock density and movement on gastrointestinal nematode abundance in grazing animals are poorly understood, with conflicting evidence from different systems (Ciordia et al., 1971, Nansen et al., 1988, Thamsborg et al., 1996, Thomsen et al., 2001). The dramatic change in livestock abundance and distribution in Kazakhstan constitutes a natural experiment whose conclusions will be relevant to many rangeland settings.

Ruminants (especially sheep) are by far the most numerous livestock in Kazakhstan and we focus on them. During the Soviet period, livestock underwent seasonal movements that were in part modelled on early nomadic migrations (Robinson and Milner-Gulland, 2003). Large numbers of sheep from farms in southern Kazakhstan were moved in spring to land allocated to them in the northern semi-desert zone up to 400 km away, where they spent 4–5 months. On steppe or desert pastures, animals were also moved within farm territories. Sheep were routinely brought from winter pasture or housing onto land close to the farm villages for lambing. Two or three further movements to more remote land would occur through the summer, with autumn grazing again close to the villages, often in the same area as that used in spring. Exact movements were planned in advance taking into account stock numbers, pasture condition, and water availability. These ensured sustainable use of pasture and avoided the build-up of infective stages of important parasites (Denisova, 1976). On the rangeland, there is little fencing, and shepherds typically grazed their allocated flock on a radius of about 3 km from the water source. Under Soviet administration the small numbers of private stock would not usually participate in seasonal movements, instead grazing year-round on common land close to the farm villages. Goats would typically move with sheep, and cattle less so, being kept closer to water and supplementary feed. In the north, all ruminants were housed in winter, whereas in some southern areas grazing continued all year round, with supplementary fodder given on the pasture.

Kazakhstan has a continental climate. We focus on the central region, where mean monthly temperatures between 1968 and 1997 varied between 34 °C and −25 °C (Unpublished data, meteorological office of Kazakhstan). Annual rainfall over the same period averaged 350 mm (240–550 mm), with almost no rain falling in most summers in the south. Relative air humidity in the central arid plain of Betpak-Dala in summer is around 35% (Denisova, 1976). These conditions present a challenge for the survival and transmission of parasites. Nevertheless, the genera Haemonchus, Marshallagia, Ostertagia, Trichostrongylus, Nematodirus, Chabertia, Trichuris and Moniezia were all considered to be economically important in the region (Irgashev, 1973, Kuznetsov and Dikov, 1979). However, published quantitative data on parasite abundance in ruminants in Kazakhstan are few and are confined to the Russian-language literature. There are no widely available recent estimates of gastrointestinal parasite prevalence and abundance in ruminants in Kazakhstan, and none that assess how observed changes in livestock numbers and management might affect parasite transmission and abundance. We aim to identify the gastrointestinal helminths that are likely to be most important to livestock production on the rangelands of Kazakhstan, and determine the main factors associated with infection under post-Soviet conditions. We use our findings to make recommendations concerning sustainable parasite control in these new conditions.