Aspectos clínicos e patológicos da intoxicação experimental por Pteridium arachnoideum (Dennstatiaceae) em equinos

Abstract

The administration of the aerial parts of Pteridium arachnoideum during 15 to 57 days in proportions that varied from 50 to 75% of the supplied grass (Pennicetum purpureum) mixed with hay of bracken fern, caused in 3 of the 4 experimental horses, a clinical and pathological picture that can be attributed to the thiaminases, one of the poisonous principles of the plant. The clinical picture consisted, in a progressive way, apathy, lethargy, sleepiness, hyporrexia with evolution to anorexia, reluctance in moving, increase of heart frequency, arrhythmia and sternal decubitus passing to lateral decubitus. The decubitus lasted at the most 48 hours. In this phase, the clinical signs previously observed got more intense; additionaly the animals refused water, made attempts of getting up without success, made intense intermittent peddling movements, followed by dyspnoea, had muscular tremors, tonic muscle spasms of limbs, opistotonus, intense sweating and finally death. The electrocardiographic analysis showed hydropericardium and myocardial failure in the last 48 hours before death. Post-mortem and histopathological examinations did not show significant lesions, unless congestion in various organs, indicating congestive heart failure. Clinical pathology revealed, in relation to the blood count, in one of the three horses, anemia in the final part of the experiment, and trombocitopenia in only two. No changes were seen in the leucograma. Parallel to a fall of serous thiamine, an increase the pyruvic acid was seen in the three animals. One of the experimental horses developed a taste for the fern, and the other two only consumed the P. arachnoideum-grass mixture with addition of sugar.