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Toxicoses of the Spinal Column and Cord in Animals


William B. Thomas

, DVM, MS, DACVIM (Neurology), University of Tennessee

Last full review/revision Oct 2021 | Content last modified Nov 2021

Arsenic Poisoning in Animals

Arsenic poisoning Arsenic Poisoning read more (toxicosis) can occur in swine because of an overdose of organoarsenicals, which are often used as feed additives to promote growth and to control swine dysentery. With 3-nitro-4-hydroxyphenylarsonic acid poisoning (“3-nitro poisoning”), there is degeneration of the spinal cord, optic nerve, and peripheral nerves. Clinical signs consist of tremors and paraparesis. Mildly affected animals can recover after withdrawal of the offending feed.

Delayed Organophosphate Intoxication in Animals

Delayed organophosphate intoxication can occur after oral or topical administration of organophosphate Organophosphates (Toxicity) The organophosphates (OPs) are derivatives of phosphoric or phosphonic acid. OPs have replaced the banned organochlorine compounds and are a major cause of animal poisoning. They vary greatly... read more -containing insecticides or anthelmintics, including haloxon. In addition to the acute clinical signs, delayed paralysis can develop 1–4 weeks after exposure. Suffolk sheep have an inherited predisposition to this neurotoxicosis because they have low levels of plasma arylesterase activity. Affected animals have progressive, symmetric paraparesis and occasionally become tetraplegic. Diagnosis is based on clinical signs and history of exposure. On histologic examination, there is Wallerian degeneration, most prominent in the spinal cord and brainstem. The prognosis for severely affected animals is poor.

Sorghum Poisoning in Animals

Ingestion of cyanogenic (as well as nitrate-accumulating) plants such as Sorghum spp (eg, Sorghum, Sudan, and Johnson grass) can cause degeneration of the spinal cord in horses and occasionally in cattle and sheep (or nitrate and nitrite poisoning). The pathogenesis may be related to the high content of hydrocyanide in these grasses. There is ataxia and weakness of the pelvic limbs and incontinence. Urine retention often leads to cystitis and hematuria. Diagnosis is based on clinical features and a history of exposure. Clinical signs of sorghum poisoning may improve with removal of the offending feed, although persistent deficits are possible. (Also see Sorghum Poisoning Sorghum Poisoning read more .)

Tetanus in Animals

Tetanus Tetanus in Animals Tetanus is caused by the neurotoxin produced by Clostridium tetani , which is found in soil and intestinal tracts and usually introduced into tissues through deep puncture wounds. The toxin... read more is caused by toxins produced by the vegetative form of Clostridium tetani. Susceptibility varies markedly among species; dogs and cats are fairly resistant compared with horses. Clinical signs of tetanus usually develop within 5–10 days after infection. These include localized or generalized muscle stiffness and extensor rigidity, dysphagia, protrusion of the third eyelid, and contracted masticatory (lockjaw) and facial (risus sardonicus) muscles. In severe cases, the animal may be recumbent with opisthotonos and reflex muscle spasms. Diagnosis of tetanus is based on characteristic clinical features. Treatment consists of wound care, administration of antimicrobials to kill any remaining organisms, and tetanus antitoxin. In mild cases, prognosis is good with early treatment. In severe cases, death may occur because of respiratory paralysis.

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Diseases of the Peripheral Nerves and Neuromuscular Junction
Laryngeal paralysis is a common disorder of older, large-breed dogs. Denervation of the cricoarytenoideus dorsalis muscle of the larynx causes the vocal folds and arytenoid cartilages to fail to abduct during inspiration, creating an upper airway obstruction. Although the etiology is usually unknown, trauma and neoplasia can cause laryngeal paralysis. Which of the following conditions can also cause laryngeal paralysis?
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