Polioencephalomalacia in a calf
History: A 1 month-old Charolais cross was submitted for necropsy, from a herd where several were found acting “goofy” and walking in circles with foam and blood coming from their mouths. They died within 1 hour of symptoms. The calves were fed “wet cake” from an ethanol plant.
Gross Necropsy Findings:
The calf was in good body condition. There were no gross abnormalities. The brain did not fluoresce under UV light.
Brain, cerebrum: there is mild multifocal necrosis and degeneration of the superficial to middle laminar cortical neurons, characterized by cellular and nuclear pyknosis, hypereosinophilic, angular cell borders, and occasional rarefaction of the surrounding neuropli. There is multifocal hypertrophy of capillary endothelial cells, and a few macrophages in Virchow-Robbins spaces surrounding vessels.
Brain, cerebrum: Mild, multifocal laminar cortical necrosis and endothelial hypertrophy
Listeria culture: Negative
Lead Toxicology: Liver = 24.67 ppm (toxic)/ Kidney = 99.29 ppm (toxic)
This is a case of lead toxicity causing laminar cortical necrosis or Polioencepahlomalacia in calf. The mild lesions pose a contrast to the severity of clinical signs, probably as a function of the acute nature of the illness. The source of the lead was never discovered int his case.
Based on the history and described clinical signs initial differentials were thiamine deficiency (Wet Cake = distiller grain = high sulfur = thiamine deficiency), and listeriosis (unusual in a calf this young, but considered based on “circling” and multiple animals affected). Listeria culture was negative, and based on the lead toxicology results thiamine deficiency is less likely.
Poliencephalomalacia in ruminants can be caused by thiamine deficiency (Bracken fern, Sulfur, grain overload), lead, and cyanide poisoning. It has also been described in salt poisoning in swine. In young animals PEM may cause acute death with only swelling of the brain or cerebral edema.
Maxie, M.G. and Youssef, S. Nervous System. Chapter 3 in Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals, 5th edition, M. Grant Maxie editor. 2007. Saunders, Elsevier.