Poisonous plants of veterinary and human importance in southern Africa.
ABSTRACT Southern Africa is inherently rich in flora, where the habitat and climatic conditions range from arid environments to lush, sub-tropical greenery. Needless to say, with such diversity in plant life there are numerous indigenous poisonous plants, and when naturalised exotic species and toxic garden varieties are added the list of potential poisonous plants increases. The economically important poisonous plants affecting livestock and other plant poisonings of veterinary significance are briefly reviewed. In addition, a synopsis of the more common plant poisonings in humans is presented. Many of the plants mentioned in this review are also used ethnobotanically for treatment of disease in humans and animals and it is essential to be mindful of their toxic potential.
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ABSTRACT: Toxic medicinal plants can be defined as any plant that in one or more of its organs contains toxin that can induce adverse side effects in animal/humans upon consumption or administration for therapeutic purposes. The use of plants in African traditional medicine (ATM) is currently not regulated in most countries of the continent, resulting in a serious danger of misadministration of toxic plants. The potential toxic effects following prolonged use of some of the popular medicinal plants are to be scientifically investigated. Of the 120 African medicinal plants screened for their toxic effects and examined in this chapter, 49 of them were potentially toxic. Toxic symptoms mainly included neurological, hepatic, renal, gastrointestinal, and cardiovascular signs. The issues related to the use of toxic plants in ATM should now be addressed and taken as a priority in all African countries. This chapter aims: (i) to report toxic or potentially toxic plants used in ATM based on the LD50 values, physical and biochemical changes; (ii) to highlight the advanced in the methods used to detect these toxic plants; (iii) to provide baseline information in order to warn healer and patient on the side effects of some commonly used herbal drugs. Most of the plants mentioned in this chapter are used in ATM for treatment of several diseases in humans and it is essential to be aware of their toxic effects. Keywords: African traditional medicine; medicinal plants; toxic effects; physical symptoms; LD50 values; biochemical and hematological changesToxicological Survey of African Medicinal Plants, First edition edited by Victor Kuete, 06/2014: chapter 7: pages 135-180; Elsevier., ISBN: 978-0-12-800018-2
- South African Journal of Botany 05/2013; 86:41-45. · 1.34 Impact Factor
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ABSTRACT: Extensive and indiscriminate use of synthetic compounds and natural compounds obtained from plant sources have resulted into serious threats to not only the aquatic ecosystem but also to human health. Aqueous seed extract of the plant Croton tiglium L. is used in many traditional medicines to treat various ailments in many developing countries. The extract is also used for killing fishes for consumption in Manipur, India. However, the side effects and safety measures are not well studied and evaluated. The present study aims to investigate major phytochemical constituents, acute toxicity and genotoxicity of the aqueous extract. The phytochemical screening was carried out using chemical methods; acute toxicity test was performed using zebrafish as a model organism and genotoxicity potential was evaluated by in vitro plasmid DNA fragmentation analysis. Our results show that the exposure of aqueous extracts of Croton tiglium cause increase plasmid DNA strand breakage in a dose dependent manner. The aqueous extract of Croton tiglium also showed pisicidal activity. So, the plant extract need to be evaluated for its long term human health hazards and safety thoroughly before it could be used for therapeutic medicinal interventions.International Journal of Scientific and Research Publications. 01/2014; 4(1):p2579.
Journal of Ethnopharmacology 119 (2008) 549–558
Contents lists available at ScienceDirect
Journal of Ethnopharmacology
journal homepage: www.elsevier.com/locate/jethpharm
Poisonous plants of veterinary and human importance in southern Africa
C.J. Bothaa,∗, M.-L. Penrithb,c
aDepartment of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa
bTADScientific, 40 Thomson Street, Colbyn 0083, South Africa
cDepartment of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa
a r t i c l ei n f o
Received 9 April 2008
Received in revised form 14 July 2008
Accepted 17 July 2008
Available online 25 July 2008
a b s t r a c t
Southern Africa is inherently rich in flora, where the habitat and climatic conditions range from arid
environments to lush, sub-tropical greenery. Needless to say, with such diversity in plant life there are
numerous indigenous poisonous plants, and when naturalised exotic species and toxic garden varieties
are added the list of potential poisonous plants increases. The economically important poisonous plants
affecting livestock and other plant poisonings of veterinary significance are briefly reviewed. In addition,
a synopsis of the more common plant poisonings in humans is presented. Many of the plants mentioned
in this review are also used ethnobotanically for treatment of disease in humans and animals and it is
essential to be mindful of their toxic potential.
© 2008 Elsevier Ireland Ltd. All rights reserved.
Southern Africa has a rich and varied flora that includes a wide
variety of plants with the potential to cause poisoning of animals
and humans. Heavy stock losses caused by plant poisoning have
occurred throughout the history of the region, and have given rise
to considerable research. Although there is a large amount of infor-
mation in the veterinary field, human poisoning appears to be less
Plant poisoning in animals is usually accidental, and most fre-
quently occurs during unfavourable conditions when pastures are
poor due to drought, veld fires and overstocking and trampling
of the grazing. Consumption of hay contaminated with poisonous
plants also occurs. In humans it may be accidental or intentional.
by the use of plants as remedies.
Poisonous plants can affect the entire spectrum of organ sys-
tems, with some plants having several toxic principles that affect
different systems. The dominant effect may depend on the condi-
tion, growth stage or part of the plant, the amount consumed, and
the species and susceptibility of the victim.
∗Corresponding author. Tel.: +27 12 5298023; fax: +27 12 5298304.
E-mail address: firstname.lastname@example.org (C.J. Botha).
While the active principles and mode of action are known for
many plants, many others are known to induce poisoning, but the
mechanism of intoxication has yet to be elucidated.
clinical syndrome observed, post-mortem lesions, evidence that
plants have been grazed, and remains of toxic plants in the gastro-
intestinal tract. Where the toxic principle is known, confirmatory
laboratory tests may be possible.
Only a proportion of plant poisonings results from the presence
of toxic principles in the plant itself. Poisoning can result from con-
tamination of non-toxic food plants with mycotoxin synthesizing
helminths and bacteria that result in the elaboration of toxins. It
can also result from mineral imbalances that are linked to the con-
sumption of certain plants under particular circumstances, such as
ing. In this review, only poisoning due to toxins in the plant tissue
itself will be discussed.
Many of the plants mentioned in this review are also used eth-
nobotanically for treatment of disease in humans and animals.
The interrelationship of pharmacology and toxicology is important
as therapeutic efficacy occurs at a lower dose, where overdos-
ing can induce poisoning. However, poisonous plants may contain
active compounds with useful biological activities (McGaw and
Eloff, 2005). With the current emphasis on research and devel-
opment of phytomedicines in southern Africa it is imperative
to be aware of and have some information at hand regarding
0378-8741/$ – see front matter © 2008 Elsevier Ireland Ltd. All rights reserved.
C.J. Botha, M.-L. Penrith / Journal of Ethnopharmacology 119 (2008) 549–558
the more common plant poisonings occurring in man and live-
When plants are to be utilized ethnobotanically it is essential to
of this review to include all aspects of ethnobotanical usage the
interested reader is referred to the complete and comprehensive
reference works compiled by Watt and Breijer-Brandwyk (1962),
toxic properties of plants of interest, prior to conducting biological
activity studies. Where toxic effects are unknown, parallel cytotox-
icity studies, or inclusion of a panel of unrelated micro-organisms,
are useful in detecting potential toxicity when screening plant
extracts or isolated natural products for antibacterial, antifungal,
antiviral and antiparasitic activity (Cos et al., 2006).
2. Major plant poisonings of livestock in southern Africa
The plant poisonings that cause major stock losses in southern
Africa have been thoroughly reviewed by Kellerman et al. (1996)
and Naudé et al. (1996).
2.1. Cardiac glycosides
Plants that contain cardiac glycosides are considered to be the
most important cause of livestock poisoning (Kellerman et al.,
1996). Cardiac glycosides affect a wide range of species, includ-
ing humans, but cardiac glycoside poisoning in southern Africa
is most frequently reported in cattle and sheep. Chemically, two
forms of cardiac glycosides’ are contained by plants, viz. car-
denolides and bufadienolides. Plants that contain cardenolides
include Nerium oleander (oleander), Thevetia peruviana (yellow
man’s poison bush), Gomphocarpus spp. (milkweeds), Cryptostegia
grandiflora (rubber vine) and Adenium multiflorum (impala lily).
As these are unpalatable plants they are rarely eaten by stock
and therefore of little veterinary importance. Major stock losses
are, however, recorded due to consumption of plants containing
bufadienolides. Poisoning by bufadienolides falls into two major
categories, acute poisoning by non-cumulative bufadienolides and
chronic poisoning by cumulative bufadienolides (Kellerman et al.,
Acute cardiac glycoside poisoning most frequently results from
Drimia (Hyacinthaceae, slangkop). Other genera of Hyacinthaceae,
Thesium spp. (Santalaceae) and Melianthus spp. (Melianthaceae)
also contain bufadienolides and have rarely been suspected or
incriminated. Tulp and slangkop appear before the rains and may
be the only greenery available, particularly in the drier parts
of their distribution areas. Contamination of hay with tulp has
also caused poisoning, as desiccated plants retain their toxicity.
Animals newly introduced to pastures where tulp grows are par-
ticularly susceptible, as aversion to tulp has not yet developed
(Snyman et al., 2003). Death is usually due to a cardiotoxic effect,
although cardiac glycosides also affect three other systems, namely
the gastro-intestinal, respiratory and nervous systems. Gastro-
intestinal effects include colic, ruminal stasis, bloat and usually
diarrhoea. Nervous signs are most frequently observed as posterior
paresis. Respiratory effects are probably neuromuscular in origin
et al., 2005). Acute cardiac glycoside poisoning may be treated
by the administration of relatively large doses of activated char-
Chronic bufadienolide poisoning is caused by a group of suc-
culent plants of the family Crassulaceae (plakkies) of the genera
Tylecodon, Cotyledon and Kalanchoe. Their bufadienolides have a
cumulative, neurotoxic effect that produces a syndrome known
as ‘krimpsiekte’ (=shrinking disease), a paretic syndrome of sheep
and goats (Botha, 2003). Consumption of these plants can result
in acute cardiac glycoside poisoning, as the manifestation depends
on factors such as dose, duration of exposure, the bufadienolides
involved and predisposing factors. Hungry animals that consume
large amounts of the plants in a short period of time may die sud-
denly or develop an acute syndrome that can include depression,
bloat, regurgitation, paralysis of the tongue, salivation and recum-
bency. This may progress to the typical chronic form of poisoning,
which can also develop in animals that are exposed to the plants
over a protracted period that allows low but continuous intake.
Affected animals lag behind the flock, walk with the neck dangling
and assume the characteristic ‘shrinking’ posture, with the back
arched, the feet drawn together under the body and the head hang-
ing down. Affected small stock tire quickly and lie down with the
neck extended sometimes twisted to one side (torticollis). Mortal-
and domestic chickens. Relay toxicosis or secondary poisoning has
that have died of krimpsiekte (Henning, 1926).
Various plants of the family Rubiaceae (Pachystigma spp., Fado-
gia homblei and Pavetta spp.) induce a syndrome known as
‘gousiekte’ (=quick sickness). Large numbers of domestic rumi-
nants can die suddenly without any premonitory signs 6–8 weeks
after ingestion of these rubiaceous plants. These plants occur in
the north-eastern and central parts of southern Africa and may be
dead after exercise or other stimulation, although a few may mani-
of the heart reveals typical lesions of degenerative cardiomyopathy
and replacement fibrosis that affect mainly the endocardium of the
isolated and purified relatively recently and has been identified as
pavetamine (Kellerman et al., 2005; Prozesky et al., 2005).
Fluoracetate poisoning due to the consumption of Dichapetalum
cymosum (‘gifblaar’, Dichapetalaceae) most frequently affects cat-
tle, possibly because the distribution of the plant coincides with
mainly cattle-raising areas. Gifblaar is deeply rooted and is gener-
allows it to sprout before the rains, when no other green forage is
available. However, it is also reported to be particularly dangerous
when the pasture is deteriorating at the end of the rainy season.
Because the mechanism of action, which blocks the tricarboxylic
acid cycle, drastically reduces cellular respiration, sudden death
occurs as a result of acute heart failure induced by the affected
animal drinking water or exercising, usually within 24h of eating
the plant (Kellerman et al., 1996).
The consumption of species of Senecio (Asteraceae: Senecio lati-
folius, Senecio retrorsus) that contain pyrrolizidine alkaloids results
in hepatotoxicosis. About 10% of cattle deaths due to plant poi-
soning and 5% of small stock deaths are attributed to seneciosis
C.J. Botha, M.-L. Penrith / Journal of Ethnopharmacology 119 (2008) 549–558
may die within a few days of consuming the plants. Clinical signs
include loss of appetite, abdominal pain, diarrhoea, and icterus.
The most significant pathological lesions are found in the liver, and
the necrotic zones. Field cases of subacute to chronic seneciosis are
more frequent. Adult cattle develop a syndrome known as Molteno
straining disease that is characterised by tenesmus, blood-stained
faeces and progressive loss of condition, as well as nervous signs
that are ascribed to hepatic encephalopathy resulting from the
severe liver damage. Sheep suffering from chronic seneciosis sim-
ilarly lose condition and may develop ascites, but although lesions
characteristic of hepatic encephalopathy may be present in the
brain, nervous signs have not been described (Kellerman et al.,
2005). Chronic seneciosis in horses manifests as a wasting disease,
(Botha and Naudé, 2002). Chronic seneciosis may be preceded by a
in all species has characteristic lesions of fibrosis, often progressing
to cirrhosis, with nodular regeneration. Megalocytosis is a typical
is another typical feature of Senecio-induced hepatosis.
2.5. Lantana camara
Lantana camara (Verbenaceae) is an important cause of poison-
ing in cattle. Although this exotic weed is generally unpalatable
to stock, its abundant availability at times when pasture is scarce
results in ingestion by hungry cattle. Furthermore, there is some
evidence that certain animals will develop a taste for Lantana and
actually eat it in preference to other plants. Sheep and goats are
susceptible but are rarely naturally poisoned, although one inci-
dent in relocated goats has been reported (Ide and Tutt, 1998).
The toxic principles are pentacyclic triterpene acids. Affected ani-
mals develop photosensitivity and jaundice as a result of retention
of phylloerythrin and bile stasis, which is ascribed to damage to
the bile canaliculi caused by the action of the toxins. Apart from
icterus and photodermatitis, clinical signs include loss of appetite,
ruminal stasis, diarrhoea and severe depression. In addition to liver
damage, severe nephrosis develops, and the animal may become
uraemic (Fourie et al., 1987). Because the toxic effects depend
upon the continuous passage and absorption of the toxins through
the gastro-intestinal tract, the effects, if not too advanced, may
be mitigated by the administration of activated charcoal. Micro-
scopic lesions in the liver and kidneys confirm cholestasis, hepatic
degeneration and necrosis, and severe damage to the renal tubular
epithelium (Kellerman et al., 2005).
2.6. Tribulus terrestris
The most important plant poisoning causing photosensitivity
in sheep, referred to as ‘geeldikkop’, is associated with the con-
sumption of Tribulus terrestris (Zygophyllaceae). This plant is an
important food plant for sheep in dry areas, but consumption of
young wilted plants and, occasionally, plants that have not wilted,
can result in hepatogenous photosensitivity. This is characterised
pathologically by the presence of birefringent crystalline mate-
rial in bile ducts that may result in their complete occlusion.
Although the clinical signs of photosensitivity are similar to those
of sporidesmin-induced facial eczema, the pathogenesis, involv-
ing the deposition of crystalline material in bile ducts that show
evidence of epithelial damage, is different (Coetzer et al., 1983). In
ilar syndrome occurs in sheep grazing Panicum grasses (Poaceae)
that have wilted in hot dry conditions after rains (Kellerman et al.,
A syndrome known as ‘vermeersiekte’ in sheep, induced by the
sible for up to 13% of stock deaths due to plant poisoning and
mycotoxicoses in South Africa (Kellerman et al., 1996). Affected
sheep show one or more of the following signs: regurgitation of
ruminal content, bloat, stiffness and/or paralysis. The name ‘ver-
target appears to be striated muscle, in which marked pathologi-
cal changes occur (Van der Lugt and Van Heerden, 1993). Sheep
that regurgitate usually show marked dilatation of the oesophagus,
which may be more than four times the diameter of the normal
oesophagus (Kellerman et al., 2005). Prompt removal of animals
from pastures with abundant Geigeria can reduce mortality and
promote recovery of most of the sheep, but production losses can
3. Other plant poisonings of livestock
Numerous plant poisonings have been documented as occa-
sional events. These are nevertheless of economic importance to
affected livestock producers, who may suffer the loss of most of
their herd or flock as a result. ‘New’ poisonous plants have been
discovered during the last two decades. Prolonged droughts and
changes in animal management may result in the discovery of
potentially poisonous plants that under different conditions would
not be eaten in sufficient quantities to cause ill effects. Many poi-
sonings affect more than one organ system, but for convenience
the less frequent plant poisonings will be grouped under the main
organ system affected.
3.1. Central nervous system
Plant poisonings affect the nervous system in various ways,
which include stimulation, depression, tremors, convulsions, pare-
sis, paralysis, and abnormal behaviour. A large number of plant
species have been associated with the development of nervous
signs in livestock (Table 1). These poisonings have been grouped
by Kellerman et al. (2005) according to whether or not they are
associated with specific pathological lesions in the central nervous
Poisoning of mainly cattle and rarely sheep and goats by con-
sumption of the pods of Albizia versicolor and Albizia tanganyicensis
occurs in late winter and spring when high winds cause large num-
Animals are usually found dead, with the ground around them
disturbed as a result of violent convulsions before death. Animals
observed in time can recover if treated with Vitamin B6(Gummow
et al., 1992).
Toxic pregnane glycosides are responsible for the nervous syn-
dromes resulting from consumption of the succulent creepers
Cynanchum africanum, Cynanchum ellipticum, Cynanchum obtusi-
folium and Sarcostemma viminale. Cynanchum species, which are
widely distributed along the coast of southern Africa, contain a
milky, bitter latex, but nevertheless appear to be palatable to
C.J. Botha, M.-L. Penrith / Journal of Ethnopharmacology 119 (2008) 549–558
Plant poisonings that primarily affect the central nervous system
Plant SpeciesSyndromeToxin Mode of action
Tremors (+bloat and diarrhoea)
Tremors, dyspnoea, vomition, diarrhoea
Tremors, hallucinations, convulsions,
mydriasis, gastro-intestinal signs
Incoordination, tremors, convulsions,
Hyperaesthesia, ataxia, tremors, paddling
Variety of nervous signs
Loss of balance, epileptiform seizures
Ataxia, head tremors, nystagmus
Ruminants, horsesPregnane glycosides Unknown
Anabasine (alkaloid like
Ficus ingens Ficus salicifolia
Inhibition of mannosidase and
glycosidases, resulting in lysosomal
Ruminants, horses, pigs
Progressive paresis and paralysis
Amaurosis, paresis, paralysis
Cattle Disorientation, head pressing UnknownUnknown
livestock. Sarcostemma viminale grows in drier areas and may be
consumed when grazing is scarce. Poisoning caused by Euphorbia
mauritanica is rare.
Dipcadi glaucum, unlike other poisonous members of its family
(Hyacinthaceae), apparently does not contain cardiac glycosides,
but is nevertheless toxic to ruminants. Consumption induces dis-
orientation and eventually posterior paresis in cattle, commencing
with knuckling over of the fetlocks, causing them to stumble; how-
ever, appetite is not affected. Sheep are more frequently poisoned
severe diarrhoea and fever, and pregnant ewes may abort. Like
many of the toxic lilies, Dipcadi glaucum sprouts rapidly after the
first rains, and may be the only green feed available on dry pas-
nus digitatus, is less common than lupinosis, a hepatotoxicosis that
occurs when lupins are contaminated with the fungus Phomopsis
leptostromiformis. Bitter lupine alkaloids have been associated with
the development of nervous signs, rapidly culminating in asphyxia,
in cattle, sheep and pigs in the Western Cape province of South
Africa, as well as in Australia and America (Van Warmelo et al.,
Datura spp. (Datura ferox, Datura stramonium), Nicotiana glauca
(wild tobacco) and Pteridium aquilinum (bracken fern) are cos-
mopolitan poisonous plants that cause nervous disorders and are
present in South Africa, although they are rarely responsible for
livestock poisoning. Datura poisoning has been reported mainly in
horses that have eaten feed heavily contaminated with the toxic
parts (Naudé et al., 2005). Poisoning by Nicotiana glauca causes an
acute nervous toxicity that culminates in death due to respiratory
paralysis, as well as teratology in sheep, but rarely causes poison-
ing in southern Africa in spite of its abundance. Bracken fern has
been associated with a variety of toxic effects worldwide. In South
Africa, horses that have eaten fodder contaminated with bracken
fern become drowsy and dyspnoeic, and develop an unsteady gait,
tremors, staggers, arching of the back, and eventually recumbency
with convulsions. Thiamine treatment in the early stages results in
(Solanaceae) are introduced ornamental plants that have escaped
from gardens and become established on natural pastures. Pigs
are most susceptible to poisoning by Melia, in particular the ripe
drupes, which have also been incriminated in poisoning in chil-
dren, but cases of poisoning have also occurred in sheep and
described in calves in the Free State province of South Africa (Botha
et al., 1999).
Another recently described neurotoxicosis involved the indige-
during times of drought. Cattle developed hyperaesthesia, ataxia
and tremors, progressing to lateral recumbency with paddling
movements and death (Myburgh et al., 1994).
Of the plant-induced neurotoxicoses with which specific patho-
logical lesions are associated, the most recently described is a
lysosomal storage disease in goats in southern Mozambique (De
Balogh et al., 1999). Ipomoea carnea (Convolvulaceae) is a cos-
mopolitan shrub that is extensively used for hedging. Goats that
consumed this plant developed ataxia, head tremors and nystag-
mus, associated with vacuolar lesions in neurons and other brain
cells typical of a lysosomal storage disease. The plant material
was demonstrated to contain toxic principles that inhibited man-
nosidase, ?-glycosidase and ?-galactosidases, resulting in lysomal
The neurotoxicosis known as ‘maldronksiekte’ (‘mad drunk dis-
ease’) in cattle induced by Solanum tettense (Solanaceae) is also
characterised by vacuolation of neurons, but has not been demon-
which is macroscopically conspicuous in severely affected animals,
and is microscopically characterised by loss of the Purkinje cells.
As the name implies, the clinical signs include loss of balance and
falling (Pienaar et al., 1976).
Progressive posterior paresis and paralysis induced in cattle,
sheep, horses and pigs by consumption of Trachyandra spp. (Tra-
and cattle are characterised by the accumulation of brownish pig-
ment in neurons in the brain and spinal cord. The toxic principles
have not as yet been identified.
C.J. Botha, M.-L. Penrith / Journal of Ethnopharmacology 119 (2008) 549–558
Nervous signs and amaurotic blindness in sheep caused by
Helichrysum argyrosphaerum are the result of severe brain swelling,
necrosis of the retina, and bilateral status spongiosus especially
of the mid-brain and thalamus (Van Der Lugt et al., 1996). In cat-
tle, which are rarely affected by this plant, stiffness and posterior
paresis associated with necrosis of skeletal muscles occurs, but not
The condition known as ‘stootsiekte’ (pressing disease) in cattle
caused by Cotula nigellifolia (Asteraceae) is unusual among toxi-
coses in being accompanied by inflammatory lesions in the white
matter of the cerebrum and mid-brain with occasional extension
to the cerebellum (Newsholme et al., 1984). The lesions consist of
perivascular gliosis with infiltration of inflammatory leucocytes,
mainly lymphocytes and plasma cells, and are more suggestive of
an infectious disease than a toxicosis.
3.2. Cardiovascular system
As described above, three of the most important plant poison-
poisoning) primarily affect the cardiovascular system. The other
cardiovascular toxicoses affect a wide range of species and involve
more than one system, although death is most likely to be due to
Gossypol is a reactive polyphenolic pigment that is present in
cotton seed (Gossypium spp.). It is inactivated by binding to pro-
tolerate higher amounts of gossypol in the diet than monogas-
tric animals, including young ruminants. Pigs are severely affected.
Clinical signs that may include dyspnoea, anorexia, unthriftiness
out warning during transport to the abattoir, without premonitory
signs. Post-mortem examination reveals severe cardiomyopathy as
well as severe hepatosis with centrilobular necrosis and haemor-
rhage that may affect the whole lobule. The hepatic lesions may be
more pronounced than the lesions in the heart. Gossypol poisoning
has also been associated with various manifestations of infertility
in monogastric species including humans (Nicholson, 2007).
Argemone spp. (prickly poppies, or ‘bloudissel’) are unpalatable,
spiny exotic weeds that are not intentionally eaten by livestock
but cause poisoning when the plants are harvested together with
lucerne or wheat. The toxic principles are isoquinoline alkaloids.
Berberine and protopine are present in all parts of the plant, while
the seeds also contain sanguinarine and dihydrosanguinarine. The
most prominent sign in affected animals is dyspnoea. Necropsy
reveals severe ascites and hydrothorax, with degenerative changes
in the myocardium and the liver. The alkaloids present in the seeds
have been demonstrated to cause vasodilation and increased vas-
cular permeability (Kingsbury, 1964).
Avocado (Persea americana) has been associated with conges-
tive heart failure related to severe cardiomyopathy in goats, sheep,
horses and ostriches (Stadler et al., 1991; Burger et al., 1994). At
lower doses aseptic mastitis has been reported in goats and horses.
High intake of the fruits of certain cultivars has poisoned budgeri-
gars and canaries, as well as possibly dogs (Kellerman et al., 2005).
Three of the most important plant poisonings of livestock
ings also cause hepatotoxicity.
Like Senecio, at least some members of the genus Crotalaria
contain pyrrolizidine alkaloids. Crotalaria spartioides has occasion-
ally been associated with hepatotoxicity in cattle (Kellerman et al.,
2005), and dosing cattle with Crotalaria spartioides and cattle and
sheep with Crotalaria dura has resulted in cirrhosis of the liver. Var-
ious members of the genus are also associated with respiratory
disease and laminitis (see below).
Several other plants induce hepatotoxicity without photosen-
sitivity. Liver lesions are characterised by centrilobular to zonal
necrosis and varying degrees of congestion and haemorrhage.
Cestrum spp. contain kaurene glycosides that are very similar to
carboxyatractyloside isolated from Xanthium spp. (Van Wyk et al.,
2002). Cestrum poisoning has been reported in cattle and goats
(Van Der Lugt et al., 1991), while pigs are most frequently the vic-
tims of cockle burr (Xanthium) poisoning. Sheep and sometimes
goats in the western parts of southern Africa may be poisoned by
eating Hertia pallens and Pteronia pallens (Asteraceae) and Gale-
nia africana (Aizoaceae) (Kellerman et al., 2005). Animals poisoned
by Galenia usually develop severe ascites, so that the condition
observed in field cases is believed to develop secondary to severe
liver damage rather than as a primary effect of the toxin (Van der
Lugt et al., 1992).
Furanosesquiterpenoids have been identified in four plants
of the family Asteraceae that cause hepatotoxicity with photo-
sensitivity. These are Lasiospermum bipinnatum, two Athanasia
spp. (Athanasia minuta, Athanasia trifurcata) and Nidorella foetida
(Kellerman et al., 2005). Poisoning of cattle and sheep by Lasiosper-
mum bipinnatum is locally important in parts of the Eastern Cape
Province and eastern Free State (Kellerman et al., 1996). The liver
lesions that typically consist of midzonal and peripheral necrosis,
with the centrilobular area relatively unaffected, are accompanied
by lung lesions of emphysema, bronchiolar dilatation, and inter-
stitial pneumonia characterised by proliferation of non-ciliated
epithelial cells (Penrith and Van Vollenhoven, 1994).
3.4. Gastro-intestinal tract
(Table 2), although the toxins and their modes of action, where
known, differ. In addition to severe, foetid diarrhoea, cattle poi-
soned with Ornithogalum spp. (Hyacinthaceae, chinkerinchee) also
become blind, and the blindness may be permanent or may resolve
within a few weeks.
Poisoning of livestock by the toxalbumin-containing plants
(Table 2) is unusual, as the plants are not palatable. Ricin poison-
ing has been associated with the accidental inclusion of castor oil
seed cake in rations. A case of poisoning of cattle that grazed Abrus
precatorius has been recorded (Kellerman et al., 2005).
Many species of the family Solanaceae, including food plants
such as tomatoes and potatoes, contain glycoalkaloids that may
reach toxic levels under particular conditions (e.g. unripe toma-
toes, potato tubers that have turned green after exposure to light).
Poisoning by Solanaceae is relatively rare, possibly due to a com-
bination of unpalatability of the unripe fruits and the fact that
solanine is rapidly hydrolysed to the less toxic aglycone in the
gastro-intestinal tract. In addition, solanine is also poorly absorbed
from the gastro-intestinal tract (Steyn, 1934).
Wild cucumbers (Cucurbitaceae: Cucumis spp.) contain cucur-
bitacins that are concentrated in the ripe fruits and the roots. These
impart an extremely bitter taste to the plants, which are generally
only eaten by cattle when nothing else is available. Clinical signs
range from sudden death with lung oedema to severe, sometimes
haemorrhagic diarrhoea (Rimington, 1935).
occasionally been incriminated in stock losses. The toxic principle
has not yet been identified but, although the clinical signs of exper-
C.J. Botha, M.-L. Penrith / Journal of Ethnopharmacology 119 (2008) 549–558
Plant poisonings that manifest as diarrhoea
Plant SpeciesSyndrome ToxinMode of action
Solanum nigrum, S. lichtensteinii
Disrupts protein synthesis
Sheep and goats
Daphnetoxin (phorbol triterpene)
imental poisoning in a sheep resembled those induced by cardiac
glycosides, none have been isolated from the plant.
Plants of the genus Gnidia (Gnidia polycephala, Gnidia burchellii)
by emphysema that causes polypnoea. Lymphoid tissues may also
be affected. The mechanism of action of the toxin is not completely
understood, but dust from the dried plant has an irritant effect on
the mucosa when inhaled (Terblanche et al., 1966).
Sesbania punicea (Fabaceae) is an introduced leguminous plant
that has been incriminated in outbreaks of poisoning in domestic
fowl and pigeons. Although it was possible to poison laboratory
in mammals in southern Africa (Kellerman et al., 2005).
3.5. Respiratory system
All the plants associated with toxic effects on the respira-
tory system also affect other systems and have been described
elsewhere. Crotalaria spp., mainly Crotalaria dura and Crotalaria
globifera, have been associated with chronic pulmonary disease
(‘jaagsiekte’) in horses and mules. Affected animals developed res-
piratory signs commencing with an increase in respiratory rate
and progressing to severe dyspnoea particularly after exercise
(Botha and Naudé, 2002). Necropsy revealed severe emphysema,
thickening of interlobular septa, and microscopic lesions show-
ing bronchiolar obstruction and desquamation of epithelial cells
into fluid-filled alveoli. There was sometimes extension of the
emphysema subcutaneously and into regional lymph nodes. The
liver of affected horses usually showed changes typical of those
the same species of Crotalaria only developed hepatotoxicity. Two
other plants that target the liver, Lasiospermum bipinnatum and
Hertia pallens, also affect the respiratory system, as described
above under hepatotoxicoses, while Gnidia spp. cause severe diar-
rhoea in addition to pulmonary emphysema (Kellerman et al.,
3.6. Urogenital system
Primary nephropathy results from poisoning by plants that
contain oxalic acid/soluble oxalates, tannins, and unknown toxic
principles. Oxalate poisoning occurs when soluble oxalates bind
with calcium in the blood, causing hypocalcaemia and the depo-
sition in tissues, in particular the kidneys, of insoluble calcium
oxalate, resulting in damage to renal tubular epithelium. High lev-
els of oxalates can occur in a wide variety of plants, including many
that are used as fodder (beetroot and related plants, prickly pears,
grazed (oxalis, sorrel, Mesembryanthemum spp.). Although soluble
that are excreted in the faeces and/or are detoxified in the rumen,
ingestion of large amounts of oxalate-containing plants can over-
whelm this mechanism and result in oxalate poisoning (Naudé and
Poisoning by ingestion of oak (Quercus robur) has been reported
in cattle, sheep and horses, although pigs can be fed acorns with-
out any ill effects. The toxic effects are believed to be due to tannin
derivatives, mainly digallic acid. The animals die as a result of
kidney failure due to severe nephrosis, accompanied by necrotic
lesions in the gastro-intestinal tract. One of the clinical signs may
be severe, foetid diarrhoea (Neser et al., 1982).
Other plants that have been associated with primary nephro-
sis are Anagallis arvensis (Primulaceae), an introduced weed that is
reported to have caused poisoning in sheep in the Western Cape
province, and Nolletia gariepina (Asteraceae), which has recently
been demonstrated to be nephrotoxic after an outbreak occurred
in cattle in the Northern Cape province (Du Plessis et al., 2004).
Plant poisonings affecting reproduction include Salsola tubercu-
latiformis (Chenopodiaceae), a shrub that grows in dry areas, and
the red and white subterranean clovers, Trifolium spp., which can
affect fertility when they contain high levels of oestrogenic gly-
cosides. Salsola spp. if consumed in sufficient quantities during
pregnancy can result in retention of the foetus past term, with a
large, post-mature lamb that, at up to three times the normal birth
weight, is likely to cause dystocia (Basson et al., 1969).
3.7. Haemopoietic system
Plant poisonings that affect the haemopoietic system include
toxic haemolysis, prussic acid poisoning, nitrite poisoning, plant-
induced bone marrow suppression and haemorrhagic diathesis.
Plants of the onion family, including onions and garlic, and
the cruciferous plants (Brassicaceae), can contain disulphides
or their precursors that, if present in sufficient quantity, can
cause haemolytic anaemia through interference with the hex-
ose monophosphate pathway. Onions can affect both ruminants
and monogastric animals, while conversion of S-methylcysteine
sulphoxide in cruciferous plants to dimethyl disulphide in the
rumen is the cause of Brassicaceae-induced poisoning (Taljaard,
A wide variety of plants can contain high concentrations of
cyanogenic glycosides that can result in prussic acid poisoning in
ing the release of prussic acid, but most species including humans
can be affected. The presence of cyanogenic glycosides depends
upon the growth stage of the plant as well as damage and wilting.
to die from anoxia (Kellerman et al., 2005).
Plants are an uncommon source of nitrite poisoning compared
to other sources such as underground water and fertilizers. Never-
theless, a number of plants contain levels of nitrates that may be
converted in the rumen to nitrites sufficient to cause intoxication.
These plants include pigweed Amaranthus spp. (Amaranthaceae)
C.J. Botha, M.-L. Penrith / Journal of Ethnopharmacology 119 (2008) 549–558
and various members of the Brassicaceae, Chenopodiaceae, and
some grasses (Poaceae). Nitrites induce poisoning due to fatal
oxygen, is formed (Kellerman et al., 2005).
One of the toxicoses caused by bracken fern (Pteridium aquil-
inum) is a haemorrhagic syndrome caused by a radiomimetic
toxin, ptaquiloside, that causes severe bone marrow suppression,
thrombocytopenia, and widespread bleeding. Feeding spoilt sweet
clover (Melilotus alba), in which coumarins have been converted to
dicoumarol, to cattle can cause a haemorrhagic diathesis if suffi-
cient quantities are fed over a long period (Kellerman et al., 2005).
3.8. Skin and adnexa
Mechanical damage to the skin and adnexa can result from con-
tact with plants and is not considered here. Skin irritation due to
contact with plants is also in general not considered to be a toxi-
cosis, but the irritant effects of the latex of Euphorbia ingens, which
can result in severe dermatitis as well as blindness, are sufficiently
severe to be categorised as a poisoning.
Ingestion of certain plants can produce adverse effects mainly
involving the skin or adnexa. Certain species of Crotalaria, prin-
cipally Crotalaria burkeana and Crotalaria barkae, cause severe
laminitis in cattle, while Crotalaria juncea has been associated with
laminitis in cattle and a break in the wool in sheep (Steyn, 1934).
also causes severe diarrhoea in adult sheep and goats. Additionally,
the plant has, circumstantially, been linked to a nervous syndrome
called falling disease (‘valsiekte’) in sheep. The spinal cord lesions
in animals that die of ‘valsiekte’ resemble those caused by copper
Hairy vetch (Vicia spp.) is associated with the development
of pruritis and granular dermatitis in cattle; granulomas may
also occur in internal organs, including the kidneys (Green and
Primary photosensitivity in livestock caused by plants that
contain hypericin has not been documented in southern Africa,
although St John’s wort, Hypericum perforatum, has been intro-
duced, and in addition there are indigenous species of Hypericum
(Hypericum aethiopicum, Hypericum revolutum) that have been
demonstrated experimentally to be capable of causing photosensi-
tivity (Kellerman et al., 2005).
4. Plant poisonings of humans
Plant poisonings of humans in eastern and southern Africa have
been documented in a comprehensive treatise by Watt and Breijer-
Brandwyk (1962). Plant poisoning in humans usually arises either
from the unintentional use of toxic plants as food or from the use
of poisonous plants for medicinal purposes. Accidental ingestion of
plants resulting in acute poisoning is more common in pre-school
children (Van Wyk et al., 2002). Human intoxication due to plant
exposure is far less important than poisonings involving paraf-
fin, pesticides, pharmaceuticals, household cleaning chemicals and
cosmetics (Gaillard and Paquin, 1999; Van Wyk et al., 2002). It is,
however, likely to be higher in societies where plant-based tradi-
tional medicines are commonly used. A survey conducted at a large
hospital in such an area revealed that poisoning with traditional
medicines is the second most common cause of acute poisoning
representing 12.1%, mostly of plant origin (Joubert and Mathibe,
1989). Through the centuries traditional medicines based on plants
known and selected for their therapeutic effects have been used
to good purpose and have undoubtedly cured many more people
than they have killed. However, the levels of poisonous principles
in plants are usually unpredictably variable, and occasional over-
in over long periods may be subtle and not well understood in
traditional medicine. The toxic effects of poisonous plants, partic-
ularly chronic effects, are not always easy to reverse, and it has
been estimated that 15% of people in southern Africa poisoned by
medicinal plants will die, as opposed to 2% suffering from acute,
non-plant-induced poisoning (Gaillard and Paquin, 1999).
4.1. Nervous system
There are numerous plants that contain cyanogenic glycosides.
Some of these, such as sorghum and cassava (Manihot esculenta),
are cultivated as crops for human consumption. Cassava is a sta-
ple food in large parts of tropical Africa. Toxicity depends on the
cultivar, and in general the sweet cassava varieties are less toxic
than the bitter varieties. Various strategies have been developed
to detoxify the tubers, such as peeling and soaking in water for
a day or two before processing. Grating, chopping, and thorough
cooking also reduce toxicity. However, acute prussic acid poison-
ing, often killing entire families, occurs sporadically in areas where
cassava of low toxicity is usually used without particular precau-
tions, and consequently tubers containing high concentrations of
the cyanogenic glycoside are prepared in the same way. A chronic
neurological condition is also associated with cassava consump-
tion. Protein-deficient subjects with low sulphur amino acids are
tic paraparesis) in Mozambique and East Africa and mantakassa
(cassava-associated tropical ataxic myeloneuropathy) in Nigeria
after consuming levels that do not affect healthy, well-nourished
is a peripheral neuropathy caused by excitatory amino acids con-
tained by this plant. The disease manifests as a spastic muscle
weakness and is clinically very similar to konzo (Ellenhorn, 1997).
Datura stramonium and Datura ferox (moon flower, jimson
weed, stinkblaar, oliebome) are cosmopolitan weeds that con-
tain parasympatholytic alkaloids such as atropine and hyoscine.
Humans are extremely susceptible to their effects and hallucina-
tions may occur, and the proverb “blind as a bat, red as a beet, dry
as a bone and mad as a hatter” aptly describes atropine poisoning
plants may be mistaken for Amaranthus and prepared as “marog”,
resulting in severe poisoning, or the seeds may end up in har-
vested maize. On occasion, young children have been forced to
swallow seeds (“malpitte”) during initiation ceremonies at schools
(Watt and Breijer-Brandwyk, 1962). Another plant of which the
young seedlings may be mistakenly collected as ‘marog’ is Nico-
tiana glauca (wild tobacco), which contains a pyridine alkaloid,
anabasine, which is very similar to nicotine. Ingestion may result in
nausea, vomition, gait abnormalities, tremors, confusion and con-
vulsive seizures (Steenkamp et al., 2002).
Boophane disticha (seeroogblom, bushman poison bulb) con-
tains various alkaloids such as buphanidrine, buphanisine and
buphanamine. Poisoning usually occurs in humans that utilize the
bulb for medicinal purposes. Acute poisoning induces vomition,
weakness, coma and mortality (Steenkamp, 2005).
4.2. Cardiovascular system
Cardiac glycoside-containing plants, which cause some of the
most economically important livestock toxicoses, are also promi-
nent in causing human plant poisoning (McVann et al., 1992).
Cardenolide-containing plants are highly toxic and may be very
C.J. Botha, M.-L. Penrith / Journal of Ethnopharmacology 119 (2008) 549–558
important in humans, as a number of garden plants contain car-
denolides. Nerium oleander (oleander, selonsroos) is a popular
ornamental plant widely used in gardens and contains oleandrin. It
is extremely toxic, apparently soldiers of Alexander the Great were
fatally poisoned when they roasted meat on skewers made from
oleander branches, and there are anecdotes of people dying after
chewing or sucking the leaves by accident. Yellow oleander (Theve-
is referred to as “Be-still-nut”. Certain cardiac glycoside-containing
plants are used medicinally.Digitalis purpurea(foxglove) contains a
cardenolide, digoxin, which is used for the treatment of congestive
heart failure. Some of the bufadienolide-containing plants, in par-
ticular Drimia sanguinea (slangkop, sekanama) and Bowiea volubilis
(climbing potato) are used by traditional healers in the treatment
of various ailments and have been implicated in human poison-
ing (Marx et al., 2005; Steenkamp, 2005). The sap of Acokanthera
oppositifolia (bushman poison bush) contains cardenolides and, as
the name implies the sap has been used as arrow poisons for hunt-
ing by the San people. Humans may accidentally or intentionally
become the target, resulting in fatal intoxication.
Although poisoning of humans by the consumption of animals
that have died of ‘krimpsiekte’ induced by cumulative bufadieno-
lides has not been documented, deaths of carnivores by relay
poisoning is well known and the possibility that humans could be
affected remains an aspect of concern (Henning, 1926). An unusual
case of possible secondary poisoning by Argemone seeds has been
as a result of feeding on contaminated wheat (Brink et al., 1965). At
the time a large number of sheep as well as people were poisoned
of the wheat could be definitively excluded and it seemed probable
that the meat of the poisoned sheep had to be responsible.
Hepatotoxic plants may be consumed either in traditional
and upon ingestion induces severe hepatotoxicity, nephrotoxic-
ity and hypoglycaemia (Wainwright et al., 1977). An atractyloside
has been isolated from the tuberous roots (Laurens et al., 2001;
Seeds and other parts of the pyrrolizidine alkaloid-containing
plants such as Senecio species and Crotalaria species may contam-
inate flour. In the 1930s bread poisoning occurred in poor people
when they consumed wheat flour contaminated with Senecio plant
ease (Steyn, 1934). Exposure to pyrrolizidine alkaloids through the
use of herbal remedies may also be a contributing factor to the
high rates of liver cancer and cirrhosis seen in Africa (Steenkamp
et al., 2000). Another pyrrolizidine alkaloid-containing plant that
is often used as herbal medicine and has also been associated with
in humans and animals. They contain different glycosides that fol-
lowing ingestion are converted in the intestinal tract to methyl-
azoxymethanol (MAM), which is hepatotoxic and carcinogenic
(Spatz et al., 1967). Reitz described that during the Anglo-Boer War
hungry soldiers ate the fruit of an Encephalartos species and were
severely affected (Reitz, 1969).
4.4. Digestive system
Toxalbumins that occur principally in the seeds but sometimes
also in other parts of plants are highly toxic plant lectins. Ricin,
derived from the castor oil plant Ricinus communis, is one of the
most toxic substances known, and features very high on the list of
substances likely to be used for bioterrorism. During the Cold War
an assassination using ricin was documented where a Bulgarian
dissident, Georgi Markov, was eliminated by the implantation in
his body of a perforated metal sphere containing ricin. The assas-
sin injected the sphere with a sharpened umbrella tip at a crowded
bus stop, and had left by the time the victim collapsed and died
(Farrell, 1992). Other members of the Euphorbiaceae family such
as Jatropha curcas and Jatropha multifida also contain a toxalbu-
min, namely curcin, which can cause severe diarrhoea. The brightly
coloured seeds of Abrus precatorius (Fabaceae) are used to produce
bracelets and necklaces and contain a toxalbumin named abrin.
Although abrin is highly toxic, poisoning in humans is unusual,
even if eaten are likely to pass through the digestive tract unbroken
(Van Wyk et al., 2002).
rhoea, dyspnoea, muscle tremors and convulsions in children (Van
Wyk et al., 2002).
Vegetables such as green tomatoes, potatoes and brinjals may
contain high concentrations of solanine, which can cause irritation
of the digestive tract. Many of the Solanaceae produce attractive
berries that might be picked and eaten by children, and which are
poisonous when unripe, although some become harmless when
ripe (Van Wyk et al., 2002).
An indigenous tree, Spirostachys africana (tamboti), which is
sometimes used for medicinal purposes, is nevertheless highly
toxic, and use of the wood in fires over which meat is grilled has
resulted in severe diarrhoea after eating the meat. Even the smoke
can cause headache and nausea (Palmer, 1981; Van Wyk et al.,
Members of the family Araceae, such as Alocasia macrorrhiza,
Dieffenbachia, Philodendron spp., Monstera deliciosa and Zant-
edeschia aethiopica (the only indigenous species) may cause severe
stomatitis. These plants are grown for their beautiful foliage,
sometimes as house plants, and contain insoluble calcium oxalate
crystals (needle-sharp raphides), which are packed in specialised
ampoule-shaped ejector cells, each with an operculum, called
idioblasts. On pressure such as crushing of the stem when chewed
the needle-like crystals are ejected and penetrate the surround-
ing tissue, resulting in intense irritation, discomfort and histamine
most of the victims in America are children, many under the age of
4.5. Skin and adnexa
African poison ivy or pynboom (Smodingium argutum) causes
an allergic dermatitis and pruritis in sensitive individuals. It even
occurs when the individual just passes near the tree (Van Wyk et
Like animals, people who come into contact with the highly
irritant milky latex of the candelabra tree or naboom, Euphorbia
severe irritation and inflammation, especially when moist mucous
membranes are affected (Van Wyk et al., 2002).
Plant poisonings of livestock are responsible for considerable
economic losses in southern Africa (Kellerman et al., 1996). Most
of these losses are due to consumption of plants that induce seven
well documented toxicoses, namely cardiac glycoside poisoning,
C.J. Botha, M.-L. Penrith / Journal of Ethnopharmacology 119 (2008) 549–558
gousiekte, gifblaar, seneciosis, Lantana camara hepatotoxicosis,
geeldikkop and vermeersiekte. Most if not all of these poisonings
occur during periods when pastures are poor and the poisonous
plants offer the most obvious source of green feed. In the case of
palatable and nutritious plant toxic. Plant poisonings are also more
common in stock newly introduced to areas where toxic plants
grow, as aversion can play an important role in protecting stock
against eating poisonous plants.
Plant poisoning of humans is possibly overwhelmingly linked
to the use of toxic plants as medicine, with many cases, including
fatal cases, presumed to occur without diagnosis or documenta-
tion (Gaillard and Paquin, 1999). Cases of contamination of human
administration of plant toxins, have also been documented.
The diagnosis of plant poisonings in livestock and humans is
not always simple, and depends on a good case history and an
evaluation of clinical signs and pathological lesions, as well as
confirmatory laboratory tests where these exist. Treatment is not
always possible or successful, and prevention remains the most
important way to protect humans and animals. The study and doc-
umentation of traditional medicines will go a long way towards
protecting people from being poisoned by substances that were
meant to cure them. For livestock, optimal pasture management
and supplementary feeding during times of adversity can prevent
many of the outbreaks of poisoning, as well as well-informed farm-
ers having a good knowledge of the local plants likely to cause
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