By Suzanne Venter
Toxic green leaves among fields full of pale dead grass are causing panic among livestock and game farmers nationwide.
These tempting green leaves of the cestrum species, also known as the inkberry, inkweed or nightshade), are deadly and veterinarians warn they cannot do anything for animals if they have eaten a large amount of them.
Dr Danie Odendaal, director of the Veterinarian Network, says a veterinarian from Reitz in the Free State reported a case in which 70 pregnant heifers or cows from a group of 200 died after eating the plants.
This happened after the livestock had been worked on and the animals could not return to their camp due to another crisis. As an interim measure the animals were driven into a nearby camp that had already been grazed and where many of the inkberry plants were unknowingly in a eucalyptus forest.
An infestation was suspected when the first animals started to die the next day and large losses were suffered over the next few days.
“This is not a new plant. We have been monitoring it for years, but the areas where it occurs vary. It is important that farmers report all strange deaths to their veterinarians and that a post-mortem examination is carried out. We now know the disease signs and the post-mortem findings well when an animal’s death is caused by the inkberry. But if it is something else, it is important that this is also documented so that we can be aware of any new disease outbreaks,” says Odendaal.
Dr. Carmen Nel, a veterinarian from the Sannieshof area in the North West, says as far as she knows, this is the first year that these berries have appeared in so many areas in the North West. “I have now had four cases of clients whose cattle ate the leaves. In one case, there were ten cattle, of which two survived. We suspect those that survived may have ingested less of the poisonous plant. The more the animals eat of it, the sicker they get and the faster they die,” says Nel.
Odendaal says they have noticed from the reported poisonings on the veterinary network the most important trend is that this poisonous plant is now more common in the lower rainfall areas, such as the Free State, North West and Gauteng, while previously it was mostly limited to high rainfall areas, such as KwaZulu-Natal and parts of the Eastern Cape and Southern Cape.
No medication helps
Nel and Odendaal warn there is no medication that can be injected into livestock or game after they have eaten large quantities of the plants.
“I have injected a few drugs, but nothing helps. The animals die, unless they have ingested very little of it, and then treatment with activated charcoal and liver support treatment can help,” says Nel.
“The cestrum species is an invasive plant and an extremely toxic terpenoid that causes strychnine-like symptoms in animals. It is highly toxic to ruminants,” says Dr. Gerhard Verdoorn, CropLife SA’s operations and stewardship manager and director of the Griffon Poison Information Centre.
Verdoorn says apart from the North West, they also know the plant occurs in Gauteng, the Free State, Mpumalanga and KwaZulu-Natal.
Odendaal says a cow eats 2.5% of its body weight per day. “So, a cow of approximately 500kg eats approximately 12kg of dry matter per day. Research by the Onderstepoort Research Institute on the cestrum species shows just 3kg of the plant can be fatal for a cow of, for example, 300kg. And more importantly, the study found the effect of the poison on the cattle that ate less was just as detrimental and they also had to be put down.
What are the signs of the disease?
A farmer from Stella in the North West, who lost a bull, two cows, a calf, two sheep and 26 impala, says the first thing he noticed was the animals’ ears seemed to be hanging. Then they started to get diarrhoea, after which they died. Nel says she saw the animals become paralysed after they ingested it.
“They become weak and cannot stand up or walk. I have had cases where the animals have been a little aggressive, but it is not always like that.
“The bush stinks and you cannot imagine that it could taste good at all, but because it is so green among all the dead grass, they eat it. And that is also the reason why it is such a problem especially at this time of year and more cases of poisoning occur because the animals are desperate for something green,” says Nel.
Prevention by eradication of plants
Odendaal, Nel and Verdoorn agree the only advice against this invasive plant from South America is to eradicate it by using the correct registered poison.
“Farmers should not take chances here. There is a lot of advice, but why would you take that chance when there is a registered poison we know works? Follow the correct route to combat it,” says Odendaal.
Verdoorn says drugs such as Arborex and Hatchet with the active ingredient imasapir are registered. Otherwise, Kaput 100 Gel with the active ingredients picloram and triclopyr is also registered.
Veterinarians on the veterinary network say farmers and poison experts have found the following recipe also works well:
Mix:
- Garlon 480EC or Tripyr 480 EC (50ml per 20 litres of water)
- Dye (optional, 60ml per 20 litres of water)
- Mineral oil or Performer (100ml per 20 litres of water)
- Tomahawk 200EC or Sabre 200EC (30ml per 20 litres of water)
Farmers who have successfully eradicated the plant also say it works better to spray the plant using a backpack sprayer because it mostly grows inside bushes, such as cat bushes, or under other trees. Cutting it out is not sufficient.
Where did it come from?
According to a publication in the Onderstepoort Veterinary Journal in 1991 (Onderstepoort J.vet Res., 58, 211 – 221 (1991), the inkberry is an evergreen shrub from South America that was brought to South Africa for its ornamental value in gardens and also to serve as shelter against the wind, and it was also used especially as fences. It then spread quickly throughout South Africa and was classified as a weed. Researchers from the Onderstepoort Research Institute found the poison of the plant is especially harmful to the livers of cattle. The plant is believed to be spread by birds that eat the ripe berries and droppings when they sit on bushes and trees.
