WildlifeCampus – Wildlife Management Course
1
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
Measures Against Toxic Plants And Poisoning©
WildlifeCampus – Wildlife Management Course
2
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
in an attempt 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 in an attempt to gain their needed relief. It is the game
managers responsibility to ensure that game are 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.
Measures Against Toxic Plants And Poisoning©
WildlifeCampus – Wildlife Management Course
3
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 with regard to 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.
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 generally has the ability to 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.
Measures Against Toxic Plants And Poisoning©
WildlifeCampus – Wildlife Management Course
4
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.
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)
Measures Against Toxic Plants And Poisoning©
WildlifeCampus – Wildlife Management Course
5
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 are capable of producing
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.
Measures Against Toxic Plants And Poisoning©
WildlifeCampus – Wildlife Management Course
6
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.
Effect of Alkaloids on Animals
The toxic effects of alkaloids can be divided into:
Per-acute effects, which are observed after a large amount 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.
Measures Against Toxic Plants And Poisoning©
WildlifeCampus – Wildlife Management Course
7
Sickness as a Result of 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.
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.
Measures Against Toxic Plants And Poisoning©
WildlifeCampus – Wildlife Management Course
8
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 down, 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.
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.
Measures Against Toxic Plants And Poisoning©
WildlifeCampus – Wildlife Management Course
9
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.
Researchers did experiments to determine the effect of gifblaar on a number
of 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 as a result of lowered production,
unproductive capital, veterinary surgeon costs, unutilised grazing and the cost of
removing poisonous plants.
Measures Against Toxic Plants And Poisoning©
WildlifeCampus – Wildlife Management Course
10
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 at all 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.
Measures Against Toxic Plants And Poisoning©