Experimental Tribulus Terrestris Poisoning In Goats

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Experimental Tribulus terrestris poisoning in goats - ScienceDirect

Abstract
Seven, 1–2-year-old native goats were fed dried Tribulus terrestris from Sabzevar district of Khorasan province for 8 weeks. Two goats showed clinical signs of toxicity including weight loss, depression, ruminal stasis, icterus and elevation of body temperature. Haematological and biochemical trails revealed a declining of packed cell volume (PCV) and plasma total protein and elevation of total and direct bilirubin, blood urea nitrogen (BUN), creatinin and potassium concentrations and serum aspartate amino transferase (AST) activity. At necropsy, the affected goats showed gross pathological changes and marked microscopic lesions in liver and kidneys including generalized icterus, hepatocellular degeneration and necrosis, biliary fibrosis and proliferation, renal tubular necrosis and crystalloid materials in bile ducts and renal tubules. Focal degeneration and necrosis of ventricular muscle of the heart were observed in one goat.

1. Introduction
Tribulus terrestris is a drought-tolerant, summer growing annual herb with prostrate hairy branches belonging to plant family of Zygophyllaceae. The plant has a worldwide distribution mostly in many parts of Iran. Grazing on T. terrestris under certain circumstances induces a hepatogenous photosensitization in sheep and goats known as Geeldikkop, Tribulosis ovis or yellow big head (Hennings, 1932, Van Tonder et al., 1972, Jacob and Peet, 1987). In this disease phylloerythrin, a photodynamic porphyrin derived from the degradation of chlorophyll by micro-organisms in the rumen, is believed to be retained as a result of occlusion of bile ducts by birefringent crystalloid materials (Kellerman et al., 1991). Biliary crystalloid materials are the calcium salts of the β-d-glucuronide of epismilagenin and episarsasapogenin (Miles et al., 1994a) which are metabolites of diosgenin and yamogenin, steroidal saponins of T. terrestris, respectively (Miles et al., 1994b).

T. ovis has an economic importance in South Africa so that about half of million animals may be affected in a single season (Kellerman et al., 1996) and it has been intensively investigated in that country (Van Tonder et al., 1971; Kellerman et al., 1996). The disease has also been reported in Australia (Bourke, 1983, Glastonbury et al., 1984, Glastonbury and Boal, 1985, Jacob and Peet, 1987), USA (McDonough et al., 1994), Argentina (Tapala et al., 1994) and Iran (Amjadi et al., 1979).

Although T. ovis is believed to be a disease of sheep and goats, it has rarely been described in later animals (Glastonbury and Boal, 1985). There is a noticeable population of goats on pastures containing T. terrestris in Iran. The present study was undertaken in order to evaluate the toxicity of T. terrestris growing in Khorasan province of Iran in goats.

4. Discussion
Findings of this study showed that feeding of T. terrestris growing in Sabzevar district of Khorasan province of Iran can lead to development of a hepato-renal disease in goats. However, there was different susceptibility of animals so that 2 of 7 goats received the plant revealed clinical signs of hepatic failure and significant histopathological lesions in liver and kidneys. Various clinical and pathological manifestations in severity have also been observed in sheep received T. terrestris (Van Tonder et al., 1972, Aslani et al., 2002) or steroidal saponins of the plant (Kellerman et al., 1991), but it was more evident in the present study while the goats fed the plant for relatively long time. Although some reports suggest that sheep and goats are equally susceptible to the disease (Hennings, 1932, Glastonbury et al., 1984), no documented evidences have been presented and according to our knowledge there is no reports of experimental induction of T. terrestris poisoning in goats. In previous experiment we observed more severe clinical signs and pathological lesions in all sheep than goats of the present study which received T. terrestris collected from same area (Aslani et al., 2002).

The findings of pathology and clinical pathology of goats in the present study are generally in agreement with those reported in cases of natural (Amjadi et al., 1979, Glastonbury et al., 1984, Jacob and Peet, 1987, Tapala et al., 1994, McDonough et al., 1994) and experimental (Van Tonder et al., 1972, Kellerman et al., 1991) T. terrestris toxicosis in sheep; and those reported in goats (Glastonbury and Boal, 1985). However, periductal fibrosis was more marked than in the ovine cases described previously (Glastonbury et al., 1984, Van Tonder et al., 1972) and in contrast to Glastonbury and Boal (1985) no periductal oedema noticed in liver sections. In addition, there were various focal fibrous tissue proliferation in the liver parenchyma with cirrhotic feature in two goats that showed marked hepatic lesions. Although there were no typical signs of facial eczema such as vascular changes in liver sections, however the concurrent action of sporidesmin with toxins of the plant cannot fully rule out. It has been revealed that low levels of sporidesmin triggers the effects of steroidal saponins of T. terrestris in sheep (Kellerman et al., 1980).

Both goats with liver lesions also showed various renal lesions with precipitation of crystalloid material in tubules and haemosidrin pigments in tubular cells. These finding also supported by laboratory findings of elevation of serum creatinin and BUN. The haemosidrosis beside the falling of PCV during the study may be related to haemolytic effects of saponins of T. terrestris (Brown, 1959, Kellerman et al., 1991).

A few cases of myocardial lesions have been found in T. terrestris induced disease (Brown, 1959, Van Tonder et al., 1972, Aslani et al., 2002) and diseases caused by other saponin containing plants such as Panicum coloratum (Bridges et al., 1987). It is suggested that these saponins are toxic to the myocardium (Dollahite et al., 1977, Bridges et al., 1987).

Although the findings including icterus and serum biochemical changes as well as histopathology (in goats 2 and 3) of goats received T. terrestris in the present study indicated liver lesions and particularly biliary disorder, no clinical manifestation of photosensitization was observed. This may be related to the time of experiment which was performed in September and October and short days with low intensity of sunlight that did not provide enough skin irradiation to cause photodermatitis. Cases of photosensitization due to ingestion of T. terrestris have often been reported to occur in the hot and sunny seasons (Van Tonder et al., 1972, Tapala et al., 1994, Kellerman et al., 1996).

T. terrestris is widely distributed in Khorasan as well as some other provinces of Iran, and sheep and goats in such area are at risk of T. ovis.
 

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