Download Plant poisoning in New Zealand

Plant poisoning in New Zealand
Plant poisonings occur sporadically. Some
management factors can increase the chance
ofpoisoning. Hungystockare morelikely to
suffer poisoning and travelling stock may
seek out unusual plants because they have an
empty stomach. Stock may graze paddocks
containing known toxic plants, e.g. ragwort
or tutu, or have access to plants suck as ngaio
or macrocarpa without ill effect but wilting
caused by spraying, or felling of branches,
makes these plants more palatable and therefore more dangerous. Connor in his book The
Poisonous Plants in New Zealand") has
covered in detail a wide range of plants that
may be poisonous. This article gives a brief
account of the more important cases that have
been seen through the MAF Animal Health
LaboratoryNetwork. Ornamental plants have
caused a significant number of the losses
recorded and care should be taken not to
discard clippingsfrom ornamentals 'over the
fence', or into the farm dump, wheregrazing
stock have access. Some common pasture and
fodder plants are not included in this paper as
they have been recently reviewed in another
issue of Surveillance.'*)
over a 7 to 10 day period prior to death.
Mild bloat, abdominal distension, tenesmus and the passing of small quantities
of bloody or mucus covered faeces may
also be seen. Deaths may occur up to 18
days after exposure.
The diagnosis can be made on history
of exposure, evidence of renal failure,
severe azotaemia, or post mortem findings. These findings include acorns in the
gastrointestinal tract, distal oesophageal
ulceration, hydrothorax and hydroperitoneum, serosal haemorrhages, speckled
kidneys, perirenal oedema and haemorrhage.
The histopathological findings in the
kidney are characteristic with widespread
severe nephrosis.
Tannin breakdown products are believed to be the main toxins involved but
Aspergillus ftlmigatus toxin may also be
involved in some cases. This relationship
was discovered when searching for the
cause of an outbreak of mucosal-likedisease syndrome in New Zealand cattle in
the 1 9 6 0 ~ . ( ~ )
Acorn
Apple Pulp
Acorn poisoning continues to be one
of the most commonly diagnosed plant
poisonings. Green acorns appear to be
most toxic and poisonings often occur in
Autumn. Lossesincows, calves and sheep
are recorded with mortality rates ranging from 10 to 20%.c31
Clinical findings include dullness and
anorexia, with marked loss of condition
In the Nelson area apple pulp is ensiled, stored and fed to pigs and cattle.
Several cases of poisoning have been reported by the local veterinary practitioners. Apple pulp has a high carbohydrate
content in a readily digestible form. Excessive intake may result in carbohydrate
overload or intoxication by alcohols produced by fermentation of the pulp in the
stack.
Symptoms in severe cases are recumbency leading to death and in less severe
cases cows will be slow and staggery
(drunk).
To prevent excessive rapid intake, the
apple pulp should be mixed with silage
and not fed to fasted cows or to excess.
Avocado
Thoroughbred horses with access to
avocado foliage were reported by Ruakura Animal Health Laboratory to develop signs of mild abdominal pain, 'enteritis' and swollen prepuce. They were
reported to be sensitive to touch over the
back, flanks and rump. In Australia similar signs have been seen in horses, with
dyspnoea and oedematous swelling of
the head and pharynx. Poisoning has
also been reported in cattle, goats, birds
and fish.")
Cherry laurel
Prunus laurocerasusis grown as a hedge
plant and occasionally causes poisoning
of sheep and horses.") Cherry laurel is
not particularly palatable. The plant contains a cyanogenetic glycoside and increased cyanide can be detected in the
stomach contents of poisoned animals.
The clinical signs are salivation, convulsions, recumbency and death. At post
mortem examination there is reddening
of the gastrointestinal tract.@
s7)
continued overleaf
18 Surveillance 23( I ) 1996
Cestrum nocturnum
Members of the Cestrum family are
grown in gardens in the northern regions
of New Zealand. Cestrurn parqui causes
stock losses in Australia with characteristic liver necrosis.!')
In 1991 Ruakura Animal Health Laboratory reported that two out of 50 Angus yearling heifers died with liver necrosis originally suspected as copper poisoning. Histologically there was severe
acute periacinar to midzonal hepatocellular necrosis. The copper concentrations
were normal and on closer investigation
it was discovered that Cestrurn nocturnun1 plants had been pruned and thrown
into the paddock and had been eaten by
the yearlings.
Delphinium
Delphiniuin is a garden plant that is a
member of the Ranunculaceae or buttercup family. Buttercups have a sporadic
history of poisonings.")Occasional deaths
have been recorded when discarded Delphiriiunr plants have been thrown into
paddocks. Symptoms varying fromincoordination and recumbency to violent
tetanic spasms may occur.iR)
Datura
Datura sfranrorriurri, thorn apple, is a
well known toxic plant found occasionally in wasteland throughout New Zealand. When the plant is crushed it has a
disagreeable odour so stockusually avoid
it.c')However,it may be a common weed
in maize crops and a case of Datura seed
contamination in a commercialhorse feed
has been recorded.") Clinically the horse
was depressed, anorexic, with a brown
foetid diarrhoea. It survived with supportative treatment.
Foxglove
Digitalis purpurea is usually unpalatable tostockbut arecent casein theWaikato shows that calves seem to like to try
everything. Care should be taken to ensure that this plant is not included when
hay is made. In the Waikato case reported by Ruakura Animal Health Laboratory, three calves in a mob of 60 were affected with sporadic ataxia, panting respiration, very fast heart rates and heartbeat
abnormalities. The glycoside in the plant
is digitalis and the serum digoxin level of
one calf tested was 0.28 nmol/ml which
is in the therapeutic range for digitalisation. A South Island case tested gave a
result of 0.12 nmol/ml digoxin, which is
the limit of detection of the method. It
appears that this test, used for monitoring digoxin therapy, has some usefulness as a test for suspected foxglove poisoning.
Eupatorium (Mexican dev iI weed)
This weed occurs on farms in Northland and horses grazing paddocks con-
taining Eupatorium develop respiratory
distress, wasting and exerciseintolerance.
At post mortem examination the lungs
fail to collapse and are yellowishor meaty.
Histologically, pulmonary fibrosis and
chronic inflammatory changes are the
main features of Eupatorium associated
pneumonopathy.'", 11, 13) Other animals
do not appear to be affected.
A similar condition is seen in horses
grazing Eupatorium in Queensland, Australia.i'4)
Goats' rue
Galega officinalis is a perennial herbaceous legume and is common along the
Manawatu River and in the WellingtonWairarapa district asanornamental plant.
It has been cultivated in Europe as a
fodder crop.(')The plant is most toxic in
spring when the lush new growth appears or in autumn when immature green
seedpods are present. The plant remains
toxic after drying. It causes sudden death
in sheep approximately 24 hours after
ingestion and 5-10% of a mob may die. At
post mortem examination there may be
froth at the nose and mouth and large
volumes of serofibrinous fluid in the thoracic cavity.
Goats' rue was suspected as the cause
of death in a 4-year-old Angora buck 36
hours after introduction to a paddock
containing this plant. Pulmonary oedema, 4 litres of serofibrinous fluid in the
thoracic cavity and soft kidneys were
features at a~topsy.!'~)
Hemlock
Conium maculatum is a biennial herb
that grows in waste places, roadsides,
and shady places. The plant has a strong
smell and is usually not attractive to
stock.(')However, deaths attributable to
it do occur from time to time.(1h)
The signs
include salivation, bloating, bodily pain,
irregular breathing, convulsions, paralysis and death. The diagnosis can be confirmed by finding the plant in the rumen
or detection of the alkaloid coniine in the
con tents.
Iceland poppy
Papavar nudicaule has caused poisoning in horses and sheep in New Zealand
usually from garden plants being discarded. The clinical signs in sheep include increased respiration, convulsive
movements and spasms. Gastroenteritis
is the main postmortem finding.") In the
horse case ataxia, muscle tremor and
spasms occurred and the horses recovered following supportative
Iris
lrisfoetidissima (stinking iris) has been
recorded as poisoning sheep, cattle and
pigs. It was also suspected as the cause of
death of one pony and illness of a second
in a group of six ponies in Canterbury in
1976.('8)
Kiwifruit
At times during the development of
the kiwifruit industry there have been
marketing problems and excess or unmarketable fruit has been fed to stock. In
one case 27 cows from a herd of 180 died.
There was loss of condition, weakness,
staggering and collapse. Some cows
aborted and others showed respiratory
distress. The pathogenesis is uncertain
but may be acidosis, alcoholic fermentation or mycotoxicosis.(")
Kowhai
This New Zealand native tree (Sophora species) is not usually regarded as
toxic to stock. However in one case poisoning is likely. Three bulls had been in a
paddock for several months with no illness. Trimmings from some kowhai trees
were thrown into their paddock and the
next day one bull was dead and the other
two appeared 'dopey'. Leaves of kowhai
were found in the rumen of the dead
bull.(2")Theseplants
contain alkaloidsand
are potentially poisonous.")
Lantana
Lantana photosensitivity and poisoning occurs in Australia but some species
are considered more toxic than others.
Connor suggests that the species that
colonised our northern regions is probably the non-toxicvariety.(')Recentlyhowever, a report from the Auckland Animal
Health Laboratory describes a case involving 12 out of 150cows seeking shade,
jaundiced and severely emaciated. Two
died and post mortem examination revealed jaundice and large pale friable
livers. Lantana toxicity was confirmed by
typical histopathological changes in liver, kidney and heart and by the presence
of Lantana in the paddock being grazed.
Lathyrus (Wild pea)
Members of the wild pea family cause
poisoning overseas but until recently this
poisoning had not been recorded in New
Zealand.") In 1981 a case was recorded in
Otago when 60 out of 600 lambs died in a
lucerne, ryegrass paddock with rough
edges containing a lot of Lathyrus sylvesIris. Affected lambs showed blindness
and head pressing. The histopathological changes in the brain, the history and
signs suggested that lathyrism was the
cause of death.'*')
Macrocarpa
Cupressus rnacrocarpa is a common
hedge plant in New Zealand and ingestion is implicated in cattle abortion.!22)
Abortion usually occurs in late pregnancy and is often associated with oedematous swelling of cotyledons and retained
foetal membranes. Access to felled macrocarpa trees is a common finding. The
felled branches are more palatable and
attractive to cattle. Deaths of cattle and
calves have also been recorded.(')
Surveillance 23( 1 ) 1996 19
There have also been queries about
other members of the cypress family, e.g.
Leyland and Lawson's cypress and their
association with abortion but there is
little hard evidence to support this.'23)
Ngaio
Myoporum laetum is a native coastal
shrub that is usually not eaten. However,
sporadic cases of poisoning do occur usually after severe storms where trees or
branches are blown down, or after heavy
snow falls where branches are broken off
and eaten by stock.(')The clinical signs in
acute cases is sudden death.
In subacute cases the animal becomes
staggery and dies in convulsions. At autopsy there is a moderate enteritis and
liver necrosis, microscopically seen as
midzonal and centrilobular necrosis,
haemorrhage replacement and jaundice.
In sublethal cases there is hepatogenous
photosensitisation with swelling and
oedema of the head and dorsal skin from
the shoulders to the tail. The skin swells,
breaks, dries and
Characteristic liver necrosis has been
seen in a possum which died while feeding on ngaio(2s).
Oleander
Nerium oleander is one of the more
highly toxic plants to animals and humans. The plant may be eaten by browsing animals but the most common causes
of poisoning are clippings or prunings of
this garden plant being dumped into
paddocks or stock gaining access to rubbish tips or dumps containing this plant.
As little as 30 g can kill an adult cattle
beast.
The toxin is a cardiac glycoside similar to digitalis. It acts by stimulating and
then paralysing the vagusnerve. Death is
rapid and without a struggle. Clinically
affected animals are weak, have an unsteady gait and are easily approached.
Rumenotomy to remove ingested plant
material and atropine treatment have
been successful.(2h)
Onion
Onions can cause Heinz body anaemia when fed to dogs. Horses that gained
access to unharvested onion crops have
died after showing signs of anaemia.")
Similar losses have been suspected in
piglets with heinz body anaemia. On post
mortem examination the viscera were
pale and there was increased pericardial
fl~id.1~')
Onion poisoning was also implicated
in yearling cattle that had grazed onions
for 3 weeks. Four of the 60 developed
'redwater' and two died. Microscopically there was haemoglobinuric nephrosis.
Onion poisoning should be suspected
when haemolytic anaemia, haemolytic
icterus and haemoglobinuria occurs in
stock fed
20 Surveillance 23( 1) 1996
Pinus radiata and Pinos
ponderosa
Grazing animals in forests and woodlots has been recommended as part of
agroforestry. If cows in late pregnancy
have access to needles of Pinus ponderosa
some may abort, show extreme weakness, have enlarged cotyledons and retained foetal membranes. Similar abortions may occur with access to Pinus radiata but much of the evidence is circumstantial. However it is recommended that
cows in the last 2 months of pregnancy
should not have accessto recently pruned
or thinned stands of radiata pine(29).
system causing excitement, epileptiform
convulsions, exhaustion and death. In
sheepa 'dummy' syndrome has also been
de~cribed.1'~)
Affected sheep stood still,
were reluctant to move and appeared
blind. Respiration was rapid and death
occurred within six hours. Often the animals are just found dead.
At post mortem examination tutu
leaves may be found in the rumen or
stomach. The lungs may be purple coloured and consolidated. Haemorrhages
may be found in the heart, on the peritoneum or in abdominal and psoas muscles.
Rhododendron
Yew
As with most toxic garden plants,
Rhododendron poisoning usually occurs
when stock gain access to prunings. Sheep
may be most susceptible as most of the
New Zealand cases involve sheep
deaths.", 3", 31, 32) The clinical signs may
include salivation, vomiting, abdominal
pain, depressed respiration, weakness,
staggering gait, convulsions, and death
from respiratory failure.
Post mortem findings may include
pale liver, congestion of lungs, and mesenteric haemorrhages. Rhododendron
leaves will be found in the rumen.
Pieris japonica, Lily-of-the-valley,is a
member of the same family as Rkododendron and can also be poisonous even to
goats.(33)
Yew is one of the most dangerous
poisonous plants. All parts of the plant
are poisonous and all species are susceptible. The main toxic principle is the alkaloid taxine. Its chief effect is to depress
the conducting tissue of the heart causing heart failure.(38)
English yew (Taxus
haccata)is remarkably toxic, doses of 100200 g of yew leaves will kill a horse.
Poroporo
Solanum Iaciniafum (poroporo) is a
New Zealand native plant which contains large amounts of salasodine which
is used in the manufacture of certain
steroids, including synthetic progesterones. The plant has been cultivated in
Canterbury and some dried leaf was experimentally fed to three pregnant ewes.
One of the three became ill, showing
inappetance, depression and diarrhoea
for 1 week prior to euthanasia. She had
dead twin lambs in utero and had gross
and microscopic lesions of oxalate nephfield cases of poir ~ s i s . 'No
~ ~confirmed
)
soning have been recorded although in
two cases poroporo poisoning was suspected.(')
In 1981 the Veterinary Officer,
Christchurch investigated an episode of
cattle abortion on Bank's Peninsula. Two
calves had been born dead and two were
born prematurely. A farm walk revealed
that poroporo had been browsed. The
role of poroporo as a cause of abortion
was questioned.[35)
Many of the accounts of yew poisoning reveal access to clippings or trimmings from garden plants. Most animals
will not graze from a growing tree but
wilted cuttings of most plants become
more attractive and palatable.
The most common feature of yew
poisoning is sudden death often while
the leaves are still being eaten. Symptoms which may be seen are trembling,
dyspnoea, and collapsefollowed by death
in 5 minutes, though death in cattle has
been known to be delayed for up to 2
days, during which time the animals appear normal. When death follows rapidly after ingestion of the plant there is little
inflammationof the stomach, but if death
has been delayed for a few hours there is
intense inflammation due to an irritant
volatile oil (oilof yew)in the sap.Diagnosis depends on the demonstration of
leaves and twigs in the ingesta. Yew poisoning is not uncommon in calves, as
these animals will nibble any vegetation
within reach.(")
References
(I)
(2)
(3)
(4)
Tutu
Tutu or Coriaria is the classical native
poisonous plant of New Zealand' and
continues to sporadically cause stock losses. Travelling stock may be particularly
affected. Travelling zoo elephants have
grabbed a toxic meal as they have passed
along our bush lined
The toxin
is tutin which acts on the central nervous
(5)
(6)
(7)
Connor HE. The Poisonous Plants in New
Zealand. Government Printer, Wellington,
1977.
Ellison RS. Poisonings in ruminants grazing
pasture and fodder crops. Surveillance 26(2),
23-6, 1994.
Jackson R. Acorn poisoning. Surveillance
10(3), 27-8, 1983.
Thomton RH,Shirley G, Salisbury RM. A
nephrotoxin from A.spergi//usfumigatus and
its possible relationship with New Zealand
mucosal disease-like syndrome in cattle. New
Zealand Journal of Agricultural Research 11,
1-14, 1968.
McKenzie RA, Brown OP. Avocado (Persea
americana) poisoning in horses. Australian
Veterinary Journal 68, 77-8, 1991.
Anonymous. Cherry laurel. Surveillance 3(3),
17, 1976.
Anonyinous. Garden-grazed sheep. Surveillance 4(S), 21, 1977.
Milne JA. A caseofDelphinium poisoning in
rams. New Zealand Veterinary Journal 14,
127, 1966.
(9) Williams S, Scott P. The toxicity of Datura
slrumoniurn (thorn apples) to horses. New
Zealand Veterinary Journal 32, 47, 1984.
( I O ) Anonymous. Eupatorium and animal health.
Surveillance 2( I ) , 9-10, 1975.
( I I j Anonymous. Eupatorium toxicity. Surveillance 2(1), 9-10, 1975.
( 12) Anonymous. Eupatorium poisoning. Surveillance 3(3j, 6-7, 1976.
( 13 j Anonymous. Eupatorium poisoning. Surveillance 3(4), 10, 1976
( 14) O’Sullivan BM. Crofton weed (Eupnrorium
udrwoplrorum) toxicity in horses. Australian
Veterinary Journal 55, 19-21, 1979.
( I S ) Nuttal WO, Thompson KG. Goats rue toxicity in a goat. Surveillance 13(2), 19, 1986.
( 16) Anonymous. Hemlock. Surveillance3(3), 16,
1976.
(17) De Malmanche I . Suspected PupuLler
nutfic.uule (Iceland poppy) poisoning in two
horses. New Zealand Veterinary Journal 18,
96-7, 1970.
( I X) Anonymous. Poisoning\. Surveillance 3(4),
20, 1976
(X)
( I 9) Fraser D. Kiwifruit poisoning. Surveillance
I3(4), 20, 1986.
(20) Anonymous. The kowhai tree - a possible
source of poisoning. Surveillance 1(2), 21,
1974.
(21) Anonymous. Lathyrism in sheep. Surveillance 8(1), 22, 1981.
(22) Macdonald J. Macrocarpa poisoning. New
Zealand Veterinary Journal 4, 30, 1956.
(23) Anonymous. Does Lawson’s cypress cause
abortion? Surveillance 4(3), 20, 1977.
(24) Anonymous. Ngaio (Myoporum luetum) poisoning in cattle. Surveillance 2(3), 20, 1975.
(2.5) Anonymous. Poisoned possum? Surveillance
7(5), 20, 1980.
(26) Vermunt J. Oleander - decorative and very
dangerous. New Zealand Veterinary Journal
35, 138-9, 1987.
(27) Anonymous. Possible onion poisoning incattle. Surveillance 6(3), 14, 1979.
(28) Anonymous. Suspect onion poisoning. Surveillance 5 ( 3 ) , 17-8, 1978.
(29) Knowles RF, Dewes HF. Pinus radiata implicated in abortion. New Zealand Veterinary
Journal 28, 103, 1980.
(30) Anonymous. Poisonings. Surveillance 3( I ),
20, 1976.
(31) Anonymous. Ifit’sornamental, its toxic. Surveillance 4(4), 18-9, 1977.
(32) Anonymous. Rhododendron poisoning. Surveillance 5(4), 18, 1978.
(33) Gibb MC. Lily of the valley poisoning in an
Angora goat. New Zealand Veterinary Journal 35, 59, 1987.
(34) Anonymous. Solanum poisoning. Surveillance 1(3), 23-4, 1974.
( 3 5 ) Evans M. Abortion caused by poroporo? Surveillance 8 (4), I I , 1981.
(36) Anderson IL. Tutu poisoning in two circus
elephants. New Zealand Veterinary Journal
16, 146-7, 1968.
(37) Anonymous. Tutu poisoning in sheep. Surveillance 4(4), 13, 1977.
(38) Anonymous. Yew poisoning. Surveillance
4(4), 22, 1977.
(39) Anonymous. Yew poisoning. Surveillance
1(1), 19-20, 1974
JB Huttori
Lincoln Animal Health Laboratory
P 0 Box 24
Lincoln
Surveillance 23(7) 1996 21