| Scott Fritz, DVM, ABVT Toxicologist Beef Cattle Institute Kansas State University Scottfritz@vet.k-state.edu |
Sources
Primarily a water deprivation syndrome – cattle can consume a significant amount of salt if fresh water is available. There are reports of mineral-starved cattle overeating mineral supplements with sodium used as an intake limiter.
Mechanism
As animals become dehydrated, the sodium concentration in the brain increases. The problem is upon rehydration, water follows the sodium into the brain resulting in cerebral edema and death to neurons.
Signs
Clinical signs are the same for lead poisoning and polioencephalomalacia and rooted in the central nervous system. Blindness is a hallmark of the syndrome and can help rule out causes of neurologic disease in cattle. Ataxia, head pression, recumbency, and death are also associated with the progression of clinical signs.
Treatment
The classic therapy for polio cases is injectable thiamine. Thiamine is a general neuro-protectant but is less effective in water deprivation cases than polio and lead encephalopathy. Slow rehydration of affected animals is the best approach. This can be a challenge on a herd basis and veterinarians and producers are often forced to get creative. Unlimited access to water will precipitate clinical signs and IV fluid therapy is not practical. Allowing water to run on a flat surface and forcing animals to drink slowly is ideal. Fluid deficits should be corrected over 12-24 hours.
Diagnosis
Diagnosis is based upon clinical signs, lack of a response to thiamine, characteristic lesions in the brain, and elevated brain sodium levels. It is important to submit both fixed and fresh brain in these cases as formalin-fixed brain is useless for sodium evaluation.
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