Pyrrolizidine Alkaloid Toxicity
Adrian Gallagher*
Abstract
Several cases of non-specific muscle weakness, depression and inappetence with or without anorexia wereencountered in an avicultural breeding facility over six months. In vivo laboratory tests were inconclusive.
Histological sections from autopsy material displayed evidence of pyrrolizidine alkaloid (PA) toxicity. Seedanalysis was positive for PAs, two seed contaminants were found neither of which contained PAs. A casereport and literature review are discussed.
Case Report
The aviaries concerned are very well managed. None of the presented birds were new. They were not incontact with each other nor had there been any major movement or introductions within the fecility. The
affected birds were from different areas of the £acility. No major management changes had been made exceptthat a change in seed supplier had occurred in January-February 1993. The new merchant is held in high regard
and supplies seed grown only on the Darling Downs.
22 March 1993
The first bird presented was a cock two year old Senegal Parrot. The clinical signs were acute onset, sick bird
look (SBL), fluffed appearance, depression, inappetence, and disinterest in the environment. Examination
showed a well-muscled bird with no discharges and was clinically normal on auscultation and palpation. Cropand faecal smears and Gram stains were normal. Bloods were taken for a body function. The bird was
hospitalised with heat, antibiotics, and Ca EDTA. Iintravenous (IV) fluids were administered. The condition of
the bird improved within 24 hours. Bloods showed elevated liver enzymes and total bile acids, indicating liverdisease (see Table 1). Treatment was continued for a further two days, then the bird was discharged on
antibiotic therapy for a further 3 days.
13 July 1993
Derbyan hen 1 year old was presented. This bird showed the same non-specific clinical signs as with theSenegal but in addition was in a wasted physical condition. Auscultation and palpation were normal. Crop andfaecal smears and Gram stains were normal. Radiographs were normal. Blood was taken for a body function
and treatment was implemented as with the Senegal. Blood results indicated myopathy (see Table 1). Thebird failed to respond after four days. Laparoscopy was performed and no abnormalities were detected.
Two days later the bird's appearance improved, she began to eat and was discharged.
20 July 1993
Three birds were presented with similar non-specific signs. They were in moderate to poor condition:
Split lutino alexandrine
Derbyen cockRingneck cock

*

SBL+
SBL++
SBL+++

Brighton Veterinary Surgery, 353 Beaconsfield Terrace, Brighton QLD 4017

136 Pyrrolizidine toxicity

Treatment was instigated as before, i.e., antibiotics, chelation and fluids in addition to crop feeding with PolyAid®. Bloods were taken £or body functions. The ringneck died overnight. Both other birds were improving.
Blood results (see Table 1).
The ringneck apparently died of renal failure. The bird was sent to Veterinary Pathology Services (VPS) forautopsy. Histology of viscera and culture and sensitivity (C&S) of gut were requested. The histologicalfindings were significant. See VPS form.

Table 112

345

SenegalDerbyanDerbyanAlexandrine

Ringneck

Total bilirubin

5.8

8.1

7.1

6.3

2.0

AST

488.0

620.0

1150.02000.01600.0Gamma GT

4.0

16.0

47.0400.0

65.0

1572.08300.010,600.0

14,400.0

22,100.0

Cholesterol

4.4

----

Total bile acids>40.0----

Uric acid

0.5

0.8

1.4

0.8

5.6

EST WCC

18.0

16.0

12.6

21.0

10.6

Function

CPKVPS Form
Gross Pathology
The bird is in moderate flesh and minimal post mortem autolysis. There is some bending of the keelbone. The kidneys are swollen, pale tan in colour with numerous pale silver flecks. The ureters
contain urate crystals. There is a mild haemorrhagic enteritis in the anterior intestine.
Histopathology
Sections of the lung show mild congestion. There are focal areas of inflammation consisting ofmacrophages and heterophils. The main region is associated with the larger airways. Sections ofliver show widespread chronic inflammation of portal regions with fibrosis and infiltrate oflymphocytes and plasma cells with occasional heterophils. There is mild hyperplasia of biliary
epithelium. Hepatocytes adjacent to areas of necrosis show mild megalocytosis and nucleomegaly.
Eixed macrophages frequently contain hemosiderin. Sections of kidney show widespread tubular
degeneration with urate accumulation and mild inflammation adjacent to crystal formation. Small
number of renal tubular epithelial cells show cytomegaly.
Morphological Diagnosis
1.
2.
3.

Nephrosis
Chronic toxic hepatitis
Acute renal tubular nephrosis with renal gout.

Pyrrolizidine toxicity 137

Samples of the remaining seed (budgerigar mix) were obtained. The client was advised to return to using his
old seed supplier until the causative agent was discovered.
On examination of the budgeridar mix, three suspect seeds discovered.
1.
2.
3.

A white millet-sized seed, smooth bright-yellow-cream and pea-shaped (approximately 5% of seedmix)
A furry olive bean-shaped seed intermediate in size to white millet and sorghum. (approximately 5seeds per kilogram).
A black, hard pyramidal seed (approximately 5 seeds per kilogram).

The Type 1 seed was identified as hulled white millet. Type 2 seed was not identified by examination. Type 3
was identified as Polygonum convolvulus - commonly known in Queensland as buckwheat.
A sample of the mixed seed was sent for a standard toxicoloaical screen at the Government ChemicalLaboratories. The sample tested positive to pyrrolizidine alkaloids. The sample of seed Type 2 was delivered
to the Herbarium for germination and identification on suspicion of being a Crotalaria spp. After about 6weeks we received an identification of Hibiscus trionicum. This is, unfortunately, a non-toxic seedcontaminant commonly found in Queensland.
The remaining batch of seed was sent for mycotoxin analysis to rule out aflatoxin contamination. These results
were negative. This testing exhausted the remaining seed supply rendering further testing impossible.
Pyrrolizidine Alkaloids
Plants containing PAs are common causes of poisoning of livestock worldwide. In Australia, numerous plant
species contain PAs. The most important groups are:
1.
2.
3.
4.
5.
6.

Crotalaria (rattlepods)
Senecio (ragworts, fireweeds, groundsel)
Heliotropium
Amsinckia (iron weeds)
Echium (Patterson's curse)
Trichodesma (camel bush)

Of these 1 and 6 have broad toxicity, 2 is less toxic and 3, 4 and 5 are least toxic (Hooper, 1958). Recently,
100,000-200,000 chickens were poisoned in Australia by heliotrope seed contamination of feed (Gaul et al,1994).
PAs were first discovered in 1967 for Senecio spp. Many different PAs occur, and they broadly cause
peracute to chronic disease. Often death occurs weeks to months after ingestion. The reproductive parts ofthe plants, including seeds contain the highest levels of PAs.
PAs are ingested in plant material and then metabolized by the liver to toxic metabolites, i.e., thedihydroalkaloids. These metabolites attack hepatocytes, causing necrosis. They are very reactive but
relatively short lived.
Some circulate in the blood to the lungs where they become secondary metabolites, i.e., the dehydroaminoalcohols. These are less reactive but are long-lived and have antimitotic nucleotoxic effects (Kirschner, 1960).
These compounds are carcinogenic, teratogenic and mutagenic.
The effects of PAs and their metabolites on tissues can be summarised by direct necrosis, inhibition of mitosis
leading to megalocytosis or by direct action on vascular endothelium causing vascular damage and oedema.

138 Pyrrolizidine toxicity

SpecificallyLiverMost PAs cause primary liver disease. The effects on vascular endothelium causes haemorrhagic
necrosis and veno-occlusive disease (This can occur within days of a single dose of PAs). The
antimitotic effects cause megalocytosis, cytoplasmic invaginations and intracytoplasmic inclusion
bodies.
Portal fibrosis, bile duct proliferation, regeneration nodules and tumours are common.
Lung
The primary change is an increase in the medial thickness o£ muscular pulmonary arteries. Sometimes
an arteritis and destruction of the external elastic lamina occurs. These lesions result in pulmonary
hypertension and a corresponding increase in right ventricular weight.
Secondary myocardial damage can also occur (Larranconi and Huxtable, 1987). Alveolar
epithelialization and emphysema can occur (Hooper, 1978).
Kidneys
PAs produce a mild to severe renal tubular necrosis. Megalocytosis follows this acute damage.
Other Tissues
PAs exert their toxic effect on other tissues as well:Spongy degeneration of the cerebrum;
Necrosis of pancreatic acinar cells (Mattocks, 1986);
Gastrointestinal tract lesions (Hooper, 1978); andVascular degeneration of the pancreas (Allen et al, 1970) and mesenteries(Schoental et al, 1959).
In poultry: Acute disease was characterised at autopsy by severely congested livers withhaemorrhagic streaks and yellow to white areas on the liver surface and swollen gall bladders.
Subacutey affected birds showed petechial haemorrhages in the liver.
Chronic cases showed sub-capsular haemorrhagic cysts and congestion of hepatic blood vessels inaddition to the other signs (Sergany et al, 1991).

Pyrrolizidine toxicity 139

Microscopic Changes in Poultry
Acute Cases
Areas of hepatocellular degeneration and necrosis predominate.
Sub-acute and Chronic Cases
Coagulative necrosis of hepatocytes and bile duct hyperplasia with fibroplastic cellular proliferation
are the most typical lesions.
No other organ changes were included in this assessment (Sergany et al, 1991).
Carcinogenicity, Mutagenicity & Antimitotic Activity of PAs
Various PAs are carcinogenic, primarily to hepatocytes (Hirono, 1981; Hirono et al, 1983), but pancreatic andspinal cord tumours are common (Schoental et al, 1972). The carcinogen is generally a metabolite formed by
the liver (Mattocks, 1986). Some PAs are being investigated as chemotherapeutic aaents because of theirantimitotic activity (Mattocks 1986). Studies have shown that all hepatotoxic PAs are also mutagenic. They
have a prolonged effect at inhibiting DNA synthesis and hence liver regeneration after necrosis (Bull et al,1968). PAs have also been found to be embryotoxic and teratogenic. (Mattocks, 1986).
Discussion
Although a precise contaminant of the seed was not established, the history, autopsy findings, histologicalchanges and presence of PAs in the sampled seed, and the absence o£ aflatoxins in the seed, are all firm
grounds for suspecting PA toxicity. Unfortunately, no seed was available for further assessment for seedcontaminants and also no further tissues were available for PA analysis. The purpose of this article is to draw
awareness to PA toxicity and to suggest it be included in the differential diagnosis of hepatic disease,specifically aflatoxicosis.
References
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Bull LB, Cullvenor CCJ and Deck A (1968) The Pyrrolizidine Alkaloids, North Holland, Amsterdam.
Gaul KL, Gallagher PF, Reyes D, Stasi S and Edgar J (1994). Poisoninas in pigs and poultry by stock feed
contaminated with heliotrope seed. In Plant Associated Toxins: agricultural, phytochemical and ecologicalaspects. Colgate AM, Darling PR, Allen SG, Huxtable CR, Mead RT and Pawter KE. CAB International
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Hurono I, Ueno I, Aiso S, Yamaji T and Haga M (1981). Carcinogenic activity of Fargugium japonicum andSenecio cannabifolius. Camera Letters, 20: 1991.
Hooper PT (1978). Pyrrolizidine alkaloid poisoning - pathology with particular references to differences inanimal and plant species. In: Effects of poisonous plants on livestock. Eds Keeler RF, Van Kampen, KR andJames LF. Academic Press, New York, 161.
Kirschner HE (1960). Nature's healing grasses. HC White Publications, Riverside.
Lafranconi M and Huxtable RJ (1981). Pyrrolizidine and the pulmonary vasculature. Reviews of Drugmetabolism and Drug Interaction, 3: 271.

140 Pyrrolizidine toxicity

Mattocks AR (1986). Chemistry and toxicity of pyrrolizidine alkaloids. Academic Press, London.
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