Intoxicação natural por Chamaecrista serpens (l) Greene em bovinos, ovinos e equinos na Bahia e comprovação experimental de sua ação fotossensibilizante em ovinos

Abstract

Proof of the toxic effect of plants for production animals is essential, as it allows control and prophylaxis measures to be adopted. In recent years, more than 20 species of toxic plants of livestock interest have been described in the North and Northeast regions of the country. However, there are still uncertainties about the etiology of some intoxications observed in the northeastern semi-arid region. The objective was to describe for the first time the epidemiological and clinicopathological findings of 11 outbreaks of photosensitization caused by Chamaecrista sp. in cattle, sheep and horses, as well as experimentally reproducing intoxication in sheep. During technical visits carried out in 9 rural properties in the agreste and sertão of Bahia, unprecedented outbreaks of natural poisoning by Chamaecrista sp. in production animals with photosensitization and pruritus. To prove the photosensitizing action of the plant, 15 healthy, young and adult crossbred Santa Inês and Dorper sheep were used. These were divided into 7 experimental groups, being 2 controls (GC1 and GC2). The plant suspected of causing poisoning was botanically identified as Chamaecrista serpens (HUEFS-240995). For experimental reproduction, the plant was collected on a property with a history of intoxication, being kept fresh in a cold chamber. Initially, a pilot experiment (EP) was carried out, in which a sheep received the fresh plant in the trough for 21 days. Additionally, an experimental group (EG) formed by 4 sheep were kept for 30 days in a pasture heavily invaded by C. serpens. In this first study, there were indications of treating hepatogenous photosensitization. Subsequently, in order to confirm the type of photosensitization involved and determine the toxic dose of the plant for sheep, 6 sheep were divided into 3 other experimental groups (G1, G2 and G3). G1 received an exclusive diet of C. serpens daily, and groups G2 and G3 received daily 10g/kg and 20g/kg of C. serpens, respectively, for 30 days. Blood samples were collected (blood count and serum biochemistry), as well as skin samples and liver biopsies. In the outbreaks studied and in the experiments carried out, the animals presented photosensitive skin lesions with varied distribution, size, intensity and appearance, in addition to hyporexia, restlessness, pruritus and photophobia. In the outbreaks, xii morbidity was varied in cattle (6% to 60%), sheep (18.75% to 62.5%) and horses (33.3% to 50%), however, the reported lethality is rare. There was a slight increase in GGT levels in 77.8% (28/36) of the natural cases of photosensitization, whose examination was performed, and in approximately 30% (4/11) of the experimental cases. At the end of the experiments, this finding, associated with the absence of significant hepatic macroscopic (in 5 necropsied sheep) and microscopic (in 11 sheep, 5 by liver biopsies and 6 post necropsy) changes, as well as the anatomopathological cutaneous alterations characteristic of photosensitization , verified in 11 sheep (orthokeratotic hyperkeratosis, hypergranulosis, acanthosis, necrosis and epidermal ulceration), allowed us to conclude that it was, in fact, primary photosensitization. In this way, it was proved that C. serpens is a plant of photosensitizing action for ruminants and equines, being responsible for several outbreaks of intoxication of causes, until then, unknown in Bahia. Therefore, C. serpens poisoning should be part of the differential diagnoses of photosensitive dermatitis in production animals in Northeast Brazil.