A FIELD OUTBREAK IN ILE-DE-FRANCE SHEEP OF A CARDIOTOXICOSIS CAUSED BY THE PLANT PACHYSTIGMA PYGMAEUM(SCHLTR) ROBYNS (RUBIACEAE)

PROZESKY, L., FOURIE, N., NESER, J. A. & NEL, P. W., 1988. A field outbreak in lle-de-France sheep of a cardiotoxicosis caused by the plant Pachystigma pygmaeum (Schltr) Robyns (Rubiaceae). Onderste­ poon Journal a/Veterinary Research, 55, 193-196 (1988) A field outbreak of Pachystigma pygmaeum intoxication in sheep is described. Noteworthy clinical signs were: respiratory distress , apathy and subcutaneous oedema of mainly the head. Gross changes included cardio­ megaly, centrilobular hepatic necrosis and effusion of body cavities. Microscopically myocardial fibrosis , affecting predominantly the endocardium of the apex, left free ventricular wall and mterventricular septum, was most striking in the majority of animals, whilst myofibre atrophy was present in l sheep. 'Gousiekte' is a cardiotoxicosis of ruminants charac­ terized by heart failure c. 3-8 weeks after the ingestion of certain rubiaceous plants (Kellerman, Coetzer & Naude, 1988). Domestic ruminants are those mainly af­ fected, and it appears that the springbok (Antidorcas marsupia/is) is also susceptible (L. Prozesky, unpub­ lished data, 1986). While the majority of animals die peracutely without premonitory signs, a few animals may show clinical signs of congestive heart failure such as lethargy, dysp­ noea and tachycardia a few days prior to death (Theiler, Du Toit & Mitchell, 1923; Jackson, Needham & Law­ rence, 1968; Pretorius & Terblanche, 1967; Pretorius, Terblanche, Van der Walt & Van Ryssen, 1973). The underlying pathological lesion is a multifocal to diffuse myocardial fibrosis, usually accompanied by a mild to moderate round cell infiltration (mainly macrophages and lymphocytes) predominantly in the endocardium of the apex, left free ventricular wall and interventricular septum(Theileretal., 1923; Smit, 1959). The pathogenesis of ' gousiekte' is still unclear. Soy­ man, Van der Walt & Pretorius (1982) concluded that deviations of the myocardial energy metabolism may be primary or secondary in the genesis of the heart failure. Furthermore, a reduction in calcium uptake by frag­ mented sarcoplasmic reticulum in vitro and ultrastructu­ ral changes in the myofibrils were also considered possi­ ble causes of cardiac insufficiency (Pretorius et al., 1973; Schutte, Els, Booyens & Pienaar, 1984). This outbreak of 'gousiekte' is reported because of the unusual large number of animals that showed signs of congestive heart failure. FIELD OUTBREAK