"Natural" does not mean "safe" (Proceedings)

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"Natural" does not mean "safe" (Proceedings)

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Nov 01, 2010

Unfortunately, many people equate natural and safe. Thus, this may explain in part the current popularity of products containing "all natural" active ingredients. However, some of the most toxic compounds known to man are naturally-occurring (botulism, cyanogenic glycosides, ricin). This presentation will discuss several toxins (poisonous substances occurring naturally) that represent potential hazards to companion animals. They are chemically diverse and affect a variety of organ systems. In several cases, the toxin or toxins responsible for tissue damage have not been identified.

Mycotoxins

Vomitoxin or deoxynivalenol has been found in dog foods containing corn, wheat, barley or oats contaminated with toxin-producing Fusarium spp. molds. Clinical signs in affected animals include sudden onset of feed refusal and emesis. In experimental feeding trials with dogs, feed refusal has occurred at vomitoxin concentrations of ~ 4 to 5 ppm. Differential diagnosis includes other causes for anorexia and emesis (viral, bacterial or parasitic), which are very non-specific signs. There are no specific clinical pathologic or post-mortem findings. Exposure is confirmed by analysis of suspect feed; most veterinary diagnostic laboratories offer vomitoxin analysis. Treatment involves removal from suspect feed and symptomatic and supportive care. The prognosis is excellent.

Several Penicillium spp. of molds produce penitrem A and/or roquefortine. Penitrem A poisoning has been reported in dogs that have ingested moldy food items (moldy cheese, bread or English walnuts). Roquefortine poisoning has been documented in dogs ingesting such moldy material as dairy products or compost. The mechanism of toxicity is not known, but penitrem A may act by interfering with central inhibitory neurons or influencing presynpatic transmitter release. Clinical signs include early restlessness, panting, and hypersalivation followed by mild to moderate whole body muscle tremors. At high doses, tremors can be severe and seizures may occur. Affected animals may be hyperesthetic. Secondary signs include hyperthermia, exhaustion, dehydration, metabolic acidosis and rhabdomyolysis. Diagnosis can be confirmed by analysis of vomitus, gastric lavage washings or stomach contents. Treatment is directed toward appropriate gastrointestinal decontamination procedures and symptomatic and supportive care. Diazepam is recommended for initially controlling agitation, muscle tremors, or seizures. If unsuccessful, methocarbamol may be tried. The majority of patients recover within 24 to 48 hours with appropriate care. Differential diagnoses includes strychnine, metaldehyde, methylxanthines, pyrethrins/pyrethroids, organophosphates/carbamates and eclampsia in pregnant animals.

Zootoxins

Spiders
Latrodectus spp. or black widow spiders are globose black spiders with an hour-glass red-orange abdominal pattern. They are widely distributed in the US. Single bites are potentially fatal especially to sensitive species such as cats. Clinical signs include progressive muscle fasiciculations, severe pain, muscle cramping, abdominal rigidity without tenderness, restlessness, hypertension, bronchorrhea, regional numbness and hypersalivation. The venom of black widow spiders contains several biologically active proteins one of which, α-latrotoxin, induces neurotransmitter release from nerve terminals. Acetylcholine, noradrenaline, dopamine, glutamate and enkephalin systems are all affected. There are no confirmatory tests that are available. One clue in cats: they may vomit up the spider. Early identification of bites is difficult unless the bite is actually witnessed. Treatment includes the administration of a specific antivenin (Lyovac®, equine origin from Merck) by slow i.v. infusion. Allergic and anaphylactic reactions can occur. If antivenin is not available, 10% calcium gluconate can be used to help alleviate muscle cramping and pain.

Loxosceles spp. also inhabit many areas of the US. They have a violin-shaped marking on the dorsum of the cephalothorax. A single bite is potentially lethal. The site of the bite can be difficult to detect initially. However, a severe dermonecrotic lesion characterized by erythema, bulla formation, sloughing and scabbing often results. Severe systemic signs are uncommon. A number of biologically active components of the venom have been identified including hyaluronidase, esterase, alkaline phosphatase, lipase, 5'-ribonucleotide phosphorylase and sphingomyelinase D. There is no specific antidote available. Case management is directed toward treating the local cutaneous reaction and systemic manifestations. Dapsone, a leucocyte inhibitor, has shown efficacy in treating dermal lesions in animal models. Anti-inflammatory, antipyretic and analgesic agents can be useful although use of agents that potentially interfere with normal clotting should be avoided.