The curse of plant poisoning continues to have devastating effects. This time, the culprit is the normal widespread devils’ thorn or duwweltjie plant that recently started killing small stock.
This is a common plant with small, yellow flowers and small, sharp thorns. What most farmers don’t realise is, this common plant can be poisonous to small stock.
This plant has a tendency of growing all over sandy areas, especially after the first rains. But once the rains stop, the green plant wilts in the hot Namibian sun. This makes the plant poisonous, especially after two to six weeks after the rains - when the plant still has a bit of moisture or has not yet dried completely.
However, other green plants become poisonous when eaten in large quantities. The poison then gets transported to the liver and some crystallites in the poison obstruct the bile ducts. Thus, the bile that is normally made in the liver and is supposed to reach the small intestines [to help with food digestion] gets stuck and prevents the liver from fuctioning properly. This results in the staining of tissues and the whole carcas by the bile, hence it turns yellow.
The animal will start avoiding the sun by constantly seeking to stay in the shade. Otherwise, it will stand with its head low towards the ground if there is no shade.
This is a typical sign in most poison cases in which the liver functioning is affected. The most common symptom farmers will notice after the duwweltjies’ thorn poisoning is when a sheep spots a swollen face and ears, hence the common Afrikaans name of the disease, geeldikkop (yellow swollen head).
Typicaly, the affected animal will scratch or rub its head on objects, because the sculp becomes itchy. If you open the mouth, the animal’s gums (mucus membranes) may appear yellow and swollen. The same happens to the eyes. With all the discomfort, the animal will refuse to eat and become depressed and then tend to have difficulty in breathing.
In mild cases or if the animal has not consumed much of the poison, it will gradually recover. However, the skin, especially around the head, will become hard and leathery before peeling off.
The hooves may become bright red around the top after a few days. This inflamation of the hoof skin leads to the animal’s loss of its hooves after a few days.
Should the animal not survive the devil’s thorn, the carcass will typically be yellowish (jaudiced) at this stage and very dehydrated. This symptom is quite similar to the anaplasmosis disease we recently described for cattle (and sometimes sheep and goats) after the disease is trasmitted by ticks. For such yellow carcasses, the liver will also appear yellowish and seem as though it might have been lightly fried. So will the kidneys.
As in most plant poisoning, there is no specific treatment for geeldikkop. However, treatment is administered per symptom. But for animals whose skins already peel off, it is better to slaughter them than to watch them suffer.
Another important trick is to keep the animal in the shade at all times and apply wound oil all over the affected skin, to keep it moist, until it recovers. If you don’t have wound oil, use the salve but mix it with an anticeptic solution and then apply it on the affected animal’s skin.
All sick animals should get special care until they recover, including giving plenty of water and soft feed even if you have to forcefeed them with a bottle. For the experienced farmers, forcefeed through a stomach tube.
As with any illness, an animal recovers much faster if you supplement its feed with multiminerals and multivitamins. Antibiotics are also recommended to prevent the animals from getting other infections since their immune system is weakened by the poisoning.
The usual activated charchoal, kaolin or Hypo® that are supposed to prevent poison from being absorbed faster in the body can also be given in the animal’s drinking water, as soon as poisoning is suspected.
Under normal circumstances, animals learn to avoid eating poisonous plants but when grazing is scarce, anything goes. Once you notice the devil’s thorn is wilting, keep sheep and goats away from them as much as possible.
The devil’s thorn will probabably always be available in our fields but the long-term solution is to manage the field in a way that the plant doesn’t become a problem.