Suspected levamisole intoxication in calves

CASE HISTORY: A group of 32 Friesian and four Hereford calves, 3–4 months old with body weights between 100–120?kg, were purchased from a weaner sale. On arrival at the property the Hereford calves were treated with a combination anthelmintic containing 2?g/L abamectin and 80?g/L levamisole hydrochloride. Shortly afterwards they developed tremors and frothing from the mouth, and two died overnight. The Friesian calves were treated with the same anthelmintic on the following day, when some showed hypersalivation and frothing from the mouth.

CLINICAL FINDINGS: Examination of the three most severely affected Friesian calves revealed severe nicotinic-type symptoms including hypersalivation, frothing from the mouth, muscle tremors, recumbency, rapid respiration, hyperaesthesia, and central nervous system depression. Other calves showed mild to moderate signs of intoxication including restlessness, tail switching, salivation, tremors, frequent defaecation, mild colic and jaw chomping. Two calves died shortly afterwards. An adverse drug event investigation revealed that the formulation and quality of the anthelmintic was within the correct specification, and that the drench gun was functioning correctly.

DIAGNOSIS: Suspected levamisole intoxication due to a combination of possible overdosing, dehydration, and stress caused by transportation and prolonged yarding.

CLINICAL RELEVANCE: Susceptibility to levamisole toxicity in New Zealand calves can be increased if factors like dehydration or stress are present. Levamisole has a narrow margin of safety, and overdosing in calves can easily occur if the dose rate is not based on their actual weight or health status.     

Suspected dimethoate toxicity in cattle

Dimethoate, an organophosphorus insecticide, was the suspected cause of toxicosis in a group of young cattle grazing on pasture that had been sprayed 6 weeks before the onset of clinical signs. Affected animals had primarily nicotinic signs, such as muscle twitching, stiffness, weakness and paralysis, though muscarinic signs, such as diarrhea, salivation and pollakiuria, were also observed. Whole blood acetylcholinesterase activity was depressed in 3 animals. The atypical clinical syndrome and poor response to treatment with atropine and other anticholinergics may have been due to coexistent hypomagnesemia.     

Suspected white kidney bean (Phaseolus vulgaris) toxicity in horses and cattle

Thirty-four mixed breed horses from two separate farms showed signs of abdominal discomfort, pyrexia and dehydration after being exposed to a new batch of 14% complete horse feed. A new batch of cattle feed from the same manufacturer resulted in dairy cows showing depression, a drop in milk production and diarrhoea. Examination of both diets revealed the presence of white kidney beans (Phaseolus vulgaris). Inclusion of raw beans of this genus in animal feeds is to be avoided.     

Suspected monensin toxicosis in feedlot cattle

Suspected monensin toxicosis was seen in feedlot cattle aged 6 to 9 months. Twenty cattle died following inclusion of monensin in the feed at 400g/tonne, which was 13 times the recommended level. The deaths occurred over 2 weeks. Clinical signs were inappetance, respiratory distress and sudden death. Post-mortem features were those of right-sided heart failure and included dependent subcutaneous oedema, ascites, hydrothorax, and periancinar hepatocyte congestion and necrosis. However, in contrast to previous reports no myocardial necrosis was found, but focal skeletal muscle necrosis was observed. Additional findings were marked pulmonary oedema accompanied by fibrin and erythrocyte exudation into alveoli and interlobular lymphatics. From these findings it appears that monensin, as well as affecting both cardiac and skeletal muscle, has a primary effect on lung vasculature.     

Polioencephalomalacia in cattle in New Zealand fed chou moellier (Brassica oleracea)

Polioencephalomalacia was diagnosed clinically in 26 heifers from a herd of 99 grazing chou moellier (Brassica oleracea). Clinical signs included ataxia, recumbency, blindness and aimless walking. Characteristic polioencephalomalacic autofluorescence was seen under long ultraviolet radiation of four fresh brains examined in the veterinary clinic and two formalin-fixed brains sectioned and examined in the laboratory. Haemorrhage and malacia were noted grossly and microscopically in the cranial colliculus, thalamus and hippocampus of two brains sectioned in the laboratory, while multifocal vasculitis was seen in one brain. High sulphur concentrations of 8500 mg/kg DM in the chou moellier and a recent change in grazing management were the most likely causes of the outbreak.     

Suspected ammonium nitrate fertiliser poisoning in cattle

The occurrence of a suspected mixed ammonia and nitrate fertiliser poisoning that led to acute illness and fatalities in cattle is described. The circumstances leading to the incident included the method of application of the fertiliser, low rainfall and the absence of subsequent irrigation of the fertilised pastures. The clinical and gross post mortem findings, principally dehydration and fluid distension of the rumen, were not pathognomonic. The complex of nitrate, nitrite and ammonia toxicity is discussed.