| Scott Fritz, DVM, ABVT Toxicologist Beef Cattle Institute Kansas State University Scottfritz@vet.k-state.edu |
Sources
- CCA (chromated copper arsenate) treated lumber, especially after burning, cattle seem to find the ashes palatable.
- Arsenic-containing insecticides
Mechanism
Most heavy metals exert their toxic effects by substitution for other metals. Arsenic is no different. Trivalent arsenicals interrupt the TCA cycle while pentavalent arsenicals uncouple oxidative phosphorylation. Both mechanisms interrupt cellular respiration and produce an energy deficit at the cellular level. Rapidly dividing cells and those with a high energy demand are first affected.
Signs
Clinical signs and risk are heavily dependent upon the valence of the arsenic involved. Generally, clinical signs are severe and associated with the gastrointestinal system. Colic, weakness, and diarrhea, often hemorrhagic, are common. Sever neurologic signs can predominate in acute exposures to readily available sources. Ataxia, staggering, recumbency are common in these cases.
Treatment
The classic antidote for arsenic poisoning is dimercaprol in companion animals but is not overly effective after clinical signs are observed so it’s use in clinical cases is limited. Thioctic acid is more effective in cattle but is not approved for use in food animals. FARAD should be consulted if used. Excretion is rapid and, unlike lead, arsenic is readily cleared after exposures.
Diagnosis
Diagnosis is heavily dependent upon elevated concentrations of arsenic in liver and kidney. Both organs should be submitted and it is important to recognize that given the rapid excretion of arsenic, animals that live for long periods after exposure may not have identifiable concentrations in these organs. Diagnosis can be supported by histologic examination of tissues, especially the kidney and gastrointestinal tract. Suspect material can also be analyzed.
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