'WITSTORM' 'VAALSTORM' Thesium spp.
By By Dr Mackie Hobson BSc(Agric),BVSc

1. Poisoning

Most deaths in winter on southern slopes but can occur whenever the ‘witstorm’ is consumed.  Deaths are usually acute and symptoms have been demonstrated in trials in sheep fed 50g dried material.

The active principle causing the cardiovascular syndrome is a Bufadienolide (a cardiac glycoside).

These are small, woody perennial shrubs (up to 1,5 m) The many thin, woody upright stems and branches of T. namaquense are green to yellow-green and virtually leafless except to the expert eye. Those of T. lineatum are grey-green or blue-green.

The flowers are inconspicuous, pale yellowish in colour and borne at the end of the branches or in the axils of the minute leaves.  The fruit are very small, spherical, with longitudinal ridges.

These plants grow in the arid to semi-arid areas open veld, seasonally dry watercourses and on hills.

Clinical signs:

• A period of laboured, shallow panting
• Diarrhoea
• Loss of muscular control
• In some cases acute death.

 Post Mortem:

Findings are non-specific

• Subepi- and endocardial haemorrhages
• Lung oedema, congestion, emphysema
• Ruminal atony and enteritis - even haemorrhagic
• Leaves present in rumen.

Treatment:

• Activated charcoal is very effective. Dose 2g/kg
• Minimize stress to prevent catecholamine release.

 Additional treatment for valuable animals:

1. Lignocaine.
2. ß-blocking agents
3. ACP: Tranquillizer (multipotent blocker)
4. Atropine (if AV-block is present).

Source, Reference:

Botha, C.J. (Christoffel Jacobus); Venter, Elna; University of Pretoria. Faculty of Veterinary Science. Dept. of Paraclinical Sciences. Section Pharmacology and Toxicology

Plant Poisonings and Mycotoxicoses of Livestock in Southern Africa: Kellerman, Coetzer, Naude