Clinical and pathological aspects of experimental Crotalus poisoning in cattle

摘要

> face="Verdana, Arial, Helvetica, sans-serif" size="2">Crotalus poisoning was experimentally reproduced by subcutaneous inoculation of Crotalus durissus terrificus (South American rattlesnake) venom into 10 clinically healthy mixed bred 12 to 36-month-old cattle, weighing 125 to 449 kg. Two animals were used as controls. The animal that received a dose of 0.03mg/kg body weight died 7h40min after inoculation. A 0.015mg/kg dose provoked death in 4 out of 7 young oxen. Two animals given 0.0075mg/kg became slightly sick and recovered. Onset of symptoms occurred from 1h30min to 13h45min after inoculation. The clinical course varied from 5h25min to 45h for animals that died, and from 33h15min to 17 days for animals that recovered. The main nervous signs observed were diminished response to external stimuli, hypotonic reflexes, dragging of the hooves, apathy, difficulties in moving around obstacles, ocular globe paralysis, lateral and sternal decubitus, and tongue paralysis. Adipsia and sometimes petechiae in the conjunctival and vaginal mucosa were observed. A slight to moderate increase in bleeding time was noted in 6 animals, and a moderate increase in partial thromboplastin time was found in 7 others. Moderate leukocytosis with neutrophilia, relative lymphopenia, eosinopenia, and monocytosis was found. There was a significant increase in creatine kinase serum levels of a ten-fold order. No significant alterations were revealed by urinalysis. Necropsy revealed minimal edema at the inoculation site, few petechiae and equimoses in the epicardium, omentum, biliary vesicle and bladder mucosa of some animals. Histopathological examination revealed necrosis (hyalinization) of groups or isolated myocytes in different muscles examined, both near and far from the inoculation site, in all animals. The diagnosis of Crotalus poisoning and its differentiation from diseases causing paralysis and muscular necrosis in cattle in Brazil are discussed.