Tremorgenic mycotoxicosis

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Tremorgenic mycotoxicosis is an acute toxin-induced gastroenteritis and neurotoxicity caused by Penicillium crustosum and Penicillium roqueforti[1].

Mycotoxins are produced by specific fungus and only certain species of Aspergillus spp, Claviceps spp and Penicillium spp produce tremorgenic mycotoxins[2], the latter of which is most frequently seen in dogs. The principal toxins involved are roquefortine and penitrem A, produced as a byproduct of mold growth[3], but consumption of more than one toxin is common in clinical cases.

Penicillium crustosum may be isolated from several types of food, including meat, fruit, cereal and cereal products, cheese, spices, and nuts. Fungal synthesis of mycotoxins is factor-dependent. For example, an ambient temperature of 25°C and a pH of 5.7 optimize production of penitrem A by P. crustosum[4].

Tremorgenic mycotoxicosis can occur rapidly (within 2 - 3 hours) following ingestion of moldy rice, walnuts, dairy products and other spoiled food, often eaten indiscriminately by dogs[5]. However, some dogs may vomit before any of these clinical signs appear.

After ingestion, the tremorgenic mycotoxins present in contaminated food are thought to cross the blood-brain barrier due to lipophilic properties[6]. These mycotoxins alter central presynaptic release of the excitatory neurotransmitters glutamate and aspartate, and the inhibitory neurotransmitter gamma-aminobutyric acid, causing most of the clinical signs[7].

Clinically affected dogs present with acute abdominal pain, muscle tremors and fasciculation, ptyalism, vomiting, fever, tachycardia, mydriasis, nystagmus, hyperesthesia and seizures. In dogs which have died from mycotoxicosis, the lungs and large and small intestine are often hemorrhagic and edematous[8].

In the brain, lesions are isolated to the cerebellum, characterized by degeneration of Purkinje cells[9].

A presumptive diagnosis is based clinical history, symptoms and exclusion of other toxins as well as snake-bite envenomation, hypocalcemia, hypoglycemia, shaker dog syndrome and distemper.

In order to differentiate from organophosphate toxicity, which has similar clinical symptoms, vomitus should be chemically tested for presence of organochlorine, organophosphor and carbamate insecticides. Biochemical detection of penetrim A needs to be distinguished from roquefortine C, a mycotoxin found in blue-vein cheese, that is relatively innocuous[10].

Treatment is usually supportive, with induction of vomiting to excavate the stomach. Apomorphine is usually given but gastric lavage may be required if severe intoxication is evident.

Supportive therapy includes intravenous fluid replacement, parenteral atropine and muscle relaxants such as diazepam, methocarbamol and anesthesia induction in severe cases with thiopentone followed by mechanical ventilation support[11].

Most affected dogs recover within a 24 - 48 hour period, although ataxia has been reported to persist up to three years in some cases[12].

References

  1. Naudé TW et al (2002) Tremorgenic neuromycotoxicosis in 2 dogs ascribed to the ingestion of penitrem A and possibly roquefortine in rice contaminated with Penicillium crustosum. J S Afr Vet Assoc 73(4):211-215
  2. Steyn PS & Vleggaar R (1985) Tremorgenic mycotoxins. Fortschr Chem Org Naturst 48:1–80
  3. Young KL et al (2003) Tremorgenic mycotoxin intoxication with penitrem A and roquefortine in two dogs. J Am Vet Med Assoc 222(1):52-53
  4. El-Banna AA & Leistner L (1988) Production of penitrem A by Penicillium crustosumisolated from foodstuffs. Int J Food Microbiol 7:9–17
  5. Munday JS et al (2008) Presumptive tremorgenic mycotoxicosis in a dog in New Zealand, after eating mouldy walnuts. N Z Vet J 56(3):145-148
  6. Puschner B (2009) Penitrem A and roquefortine. In: Plumlee KH, ed. Clinical Veterinary Toxicology. St. Louis, MO: Mosby. pp:258-259
  7. Bradford HF et al (1990) Changes in transmitter release patterns in vitro induced by tremorgenic mycotoxins. J Environ Pathol Toxicol Oncol 10:17–30
  8. Hayes AW et al (1976) Acute toxicity of penitrem A in dogs. Toxicol Appl Pharmacol 35:311–320
  9. Breton P et al (1998) Brain neurotoxicity of penitrem. A: electrophysiological, behavioral and histopathological study. Toxicon 36:645–655
  10. Tiwary AK et al (2009) Using roquefortine C as a biomarker for penitrem A intoxication. J Vet Diagn Invest 21(2):237-239
  11. Boysen SR et al (2002) Tremorgenic mycotoxicosis in four dogs from a single household. J Am Vet Med Assoc 221(10):1441-1444
  12. Eriksen GS et al (2010) Poisoning of dogs with tremorgenic Penicillium toxins. Med Mycol 48(1):188-196