Module # 6 – Component # 2 Measures Against Toxic Plants ... · symptoms by which plant poisoning in game may be recognised. The sudden illness of game without a visible reason

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Measures Against Toxic Plants © Copyright

Module # 6 – Component # 2

Measures Against Toxic Plants and

Poisoning

Introduction Toxic plants we will have learnt from the previous component are an integral part of the Savanna Ecosystem. Wildlife managers must accept this fact and devise methods of dealing with the phenomenon.

This takes the form of a four-pronged plan:

Preventing poisoning

Eradicating (to some degree) the poisonous plants

Identifying affected Game

Treating and managing affected game

Impala: Aepyceros melampus



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Prevention of Poisoning

From a management point of view:

Veld management: Good veld management that prevents over-grazing and includes alternate grazing in one form or another, can maintain conditions that are least favourable for the increase of toxic plants and plant poisoning. Various toxic plants are pioneer plants, which would disappear as plant succession progresses to the climax state. (More on Plant succession and climax communities can be found in the Ecology Module of the Game Ranging course under the Ecosystem Dynamics component)

Veld fires: The judicious burning of veld and correct veld management thereafter,

can prevent plant poisoning.

Mineral provision: Adequate provisioning of minerals prevents the over utilisation of a specific plant species, which can become toxic to protect itself against over utilisation.

Wild animals also have an innate ability to sense when they are ill or have a mineral

deficiency – this ability is called a picorism. Animals that experience a picorism will deliberately seek out unusual and unfamiliar plants to gain their needed relief. It is the game managers responsibility to ensure that game is adequately supplied with minerals and treated when ill.

Transfer provision: During the translocation of game from one reserve to another,

before the animals are released, they are placed in temporary camps to acclimatise. If possible, game must then, not be placed in camps containing toxic plants, especially if the camp is small. If this requirement cannot be met, adequate food must be provided to ensure that game does not utilise the poisonous plants.

Encampment: Areas with thick stands of toxic plants can be enclosed to keep

game out. This is not always successful on game farms, but animals can be kept out of areas which have an abundance of toxic plants by placing water and licks in other places.

Importing game: Animals, which mature in a certain area, know and avoid the toxic

plants that occur there. Game from other areas is not familiar with the toxic plants on the new farm and is less selective. It is, therefore, advisable to only buy game from areas in which the same toxic plants occur.

Management ability: The lack of knowledge and awareness of farmers regarding

poisoning is important. Farmers must be made aware of potential poisonous plant problems on their farms and must have a degree of knowledge of how to handle this from a manager’s point of view.



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The Adaptation of Game

All game, feeds in an environment where plants with potential toxins occur. It is presumed that game is adapted to these substances. Animals have adapted to secondary chemicals in plants by using one of the following strategies: avoidance, dilution, degradation or detoxification. Avoidance Game can generally distinguish between toxic and non-toxic plants or to decrease their intake to undamaging amounts. This has developed by a learning process in animals that live in a geographical area where certain poisonous plants occur.

Dilution Game usually eats a large variety of plants. This kind of diet tends to reduce the amount of toxins taken in and reduces the chance for the intake of lethal amounts of poison.

Degradation / detoxification The two main methods of the annihilation of harmful secondary products are:

Degradation of the toxin in the gastro-intestinal tract General and specific detoxification mechanisms that are active after absorption

has occurred from the intestinal tract.

Healthy gastro-intestinal micro-organisms can render many poisons harmless. Proline (a naturally produced chemical) in the saliva of browsers binds with tannin, also rendering it harmless.

Impala: Aepyceros melampus



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Eradication of Toxic Plants

The total eradication of toxic plants is not always possible because in some cases there are no known effective practical methods for the eradication of the specific toxic plants. This is further made difficult since many of the plants have bulbs, and furthermore, the seed of some toxic plants can lie dormant in the soil for a long time and only germinate when conditions are favourable.

A mechanical approach to the eradication of some toxic plants is the most suitable. Many toxic plants have been declared weeds under Law No. 42 of 1973 and chemical control can thus be applied.

(More information on the eradication of invasive species and poisonous plants can be found in the Game Ranging Course, Module # 11, component # 7 – Principles of Habitat Management. This topic is also further explored in Module # 10 – Toxic Plants - of this course)

Hartebeest: Alcelaphus buselaphus



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Symptoms of Poisoning In general, it is very difficult to reach diagnosis because many sicknesses are caused by viruses, bacteria, fungal and feeding disruptions, deficiency diseases or internal and external parasites that cause similar symptoms and can be confusing. There is no easy or practical solution to the problem. Every possible case of cattle poisoning by plants must be discussed with a vet as soon as possible. A detailed description of the signs and duration of the sickness is very important. Special notes must be made of cramps, excitability, the appearance of paralysis, constipation, stomach working, blindness and skin damage.

Toxins can damage the animal’s body in many ways. Usually one organ is attacked more than another. Therefore, blood, muscle, nerve, intestine and other toxins must be

considered. With all plant poisonings absorption occurs through the intestine.

Since plants contain many different chemicals, they can produce a variety of clinical symptoms. It is therefore important to understand that there is not a unique group of symptoms by which plant poisoning in game may be recognised. The sudden illness of game without a visible reason provides an adequate reason to include poisoning on the list of possible reasons. In the absence of fever, and with acute dysfunctions of the digestive canal or central nervous system, which leads to weight loss, plant poisoning can be suspected.

Other clinical signs, which regularly occur with plant poisoning, include:

Total indisposition Repeated attempts to empty the bowels Stomach or intestine wall irritation A quickening or variation in the heartbeat.

These general signs are often followed by weakness, breathing problems, fainting and comas, followed by death within a few hours.

The two most important secondary chemicals in plants, as already mentioned, are tannins and alkaloids.



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Effect of Tannins on Animals

The absorbed tannins cause a decrease in intake by:

The modification of the physiological system, Causing poisoning, By causing an additional energy requirement.

Liver and kidney damage can occur in animals that ingest tannins, especially where the detoxification mechanisms cannot detoxify the absorbed phenols. Although game may have a higher detoxification capacity, the rate of intake, and the rate of detoxification must balance.



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Effect of Alkaloids on Animals

The toxic effects of alkaloids can be divided into:

Per-acute effects, which are observed after a large number of alkaloids have been taken in. The central nervous system is affected, convulsions are observed, and death occurs within a few minutes

Cytotoxic effects where cells in various organs such as the liver, lungs, heart, kidneys

and brain are damaged and destroyed. Death occurs within a few days to a few years after the intake of alkaloids.

Although the effect of alkaloids is usually on the central nervous system, a certain amount of the alkaloid must accumulate in the blood before poisoning occurs.

Giraffe: Giraffa camelopardalis



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Sickness from Poisoning Literature available on plant poisoning of game is limited. General diseases, which occur in domestic cattle, are discussed individually and it is accepted that game can suffer from the same sicknesses.

Since the accumulated knowledge on this specific topic has primarily been derived from cattle farming – and in South Africa this activity is largely the domain of Afrikaans speaking farmers, the names for the diseases have become known by their Afrikaans common names. The English equivalent and scientific names will be given where possible.

Springbok: Antidorcas marsupialis



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Gousiekte Quick sickness / Pachystigma pygmaeum poisoning / Dwarf Medlar poisoning

Gousiekte occurs in ruminants and is characterised by chronic heart seizure. Signs of poisoning can take from 4 to 8 weeks after intake to be manifested. In acute cases, a sheep with Gousiekte will be grazing peacefully in the veld, then

suddenly turn around in circles once or twice and sometimes bleat loudly or jump into the air and fall down dead. This is one origin of the quick in quick-sickness

Deaths are increased by quick movement such as when the herd is chased. Closer observations have brought to light the fact that animals show quicker breathing and heartbeat a few hours before they die.

Gousiekte remains the most important plant poisoning in South Africa.

Geeldikkop Sunlight sickness, / Tribulus terrestris poisoning / Devil thorns poisoning

A great many plants can cause photo-sensitivity (over-sensitivity to sunlight). The

Tribulus sp. causes by far the most losses by Geeldikkop. Light sensitivity is caused by photo-dynamic chemicals of the plant that

accumulate in the animal’s skin. These chemicals can absorb energy from sunlight and release this energy into the surrounding tissues thus causing damage.

Lantana camara-poisoning is very painful and unpleasant. The poison attacks the liver and causes the animals to be very sensitive to sunlight, as mentioned above. The skin peels off and forms a crust layer that hardens and bursts. Sores develop, the animals battle to eat and breathe, their kidneys are damaged, and they often die.

This plant is classified as a noxious weed in South Africa in addition to being an alien exotic from South America. If it is found growing on your property you will be subject to a substantial fine.

Dronksiekte Drunk disease / Drilsiekte / Bewerasiesiekte / shivering disease

Sometimes no signs of the disease can be seen when the animals are peacefully

grazing. The disease only becomes visible when the herd is chased. The symptoms are as follows: shivering of the whole body, shortness of breath, quick

pulse, staggering, falling, sometimes the animal wanders around aimlessly and falls off a cliff, or into ditches. The best treatment is to allow the animal to rest as much as possible.



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Stywesiekte Stiffsickness / Crotolaria burkeana intoxication / Rattle pod poisoning

This is caused by Crotolaria burkeana. The toxin causes painful inflammation of the horn forming layers of the hoof, which

leads to an uncomfortable walk. The toxin is also an active liver toxin, and the liver is often so badly damaged that

the animal cannot recover.

There are two other diseases that are also known as ‘stywesiekte’. One is caused by a phosphate deficiency; while 3 – day Stiffsickness is a viral disease and is contagious

Vermeersiekte Expand sickness / Geigeria ornativa poisoning / Vermeerbos poisoning

This disease is caused by the intake of Geigeria spp. causes vomiting of the rumen

content through the nose and mouth, stiffness and muscle paralysis. Vomiting occurs as a result of total or partial paralysis of the oesophagus which disrupts the animal's control over the normal rumination function.

Gifblaarsiekte Poison leaf sickness / Dichapetalum cymasum poisoning

Gifblaar (Dichapetalum cymasum) is one of the most toxic plants in the world. The younger leaves are the most poisonous. One seldom sees an animal that is sick with Gifblaar because they usually die very

quickly. Gifblaar poisoning is characterised by a latent period of 4 - 24 hours before clinical

symptoms are visible. The main area that is affected is the central nervous system of carnivores, and the

heart of ruminants. Affected animals usually show muscle spasms, stagger around, are excited and the

breathing is heavy, and the heartbeat is weak.



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Researchers did experiments to determine the effect of gifblaar on several different species.

They found the following:

Interrupted periods of listlessness and lack of appetite was observed for eland. Listlessness, lack of appetite and shivering was observed for kudu. Muscle tremors and irregular breathing occurred in gemsbok. Bleating was observed for springbok, but most died before any symptoms were

observed.

Although many animals recover from plant poisoning, there are a number of plant toxins that permanently affect the growth and productivity of the animal as well as their resistance to other diseases. It is exceptionally difficult to financially calculate losses because of lowered production, unproductive capital, veterinary surgeon costs, unutilised grazing and the cost of removing poisonous plants.

Springbok: Antidorcas marsupialis



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Treatment of Poisoned Animals

Poisoned animals are seldom noticed before they die. Handling poisoned game will hasten their death. Almost no antidotes for plant poisoning exist. Exceptions are that sodiumthiosulphate (hypo) or even sulphur can be used for Geilsiekte treatment. Nitrate and nitrite poisoning can be treated by supplying methylene blue intravenously.

The treatment of poisoned game is very difficult. A few general principals can be applied when poisoning is expected.

These are:

If possible, further intake of toxins must be prevented by moving the animals to another area, where the plant concerned does not occur. This must be done as peacefully as possible.

The herd, both sick and healthy animals, must be kept away from water for a day

or two.

Poisons, which have not yet been aborted, must be removed. Animals may be given chemists paraffin which will delay the uptake of toxins, protect the stomach intestine mucous membrane and it also has a strong laxative effect.

General supportive therapy is necessary to keep the vital body functions going and

to maintain homeostasis. Animals must also be kept warm in a sheltered and dry environment.

Documents

Module # 6 – Component # 2 Measures Against Toxic Plants ... · symptoms by which plant poisoning in game may be recognised. The sudden illness of game without a visible reason