Alterações oftálmicas associadas à intoxicação experimental por closantel em caprinos

Ophthalmic findings in sheep treated with closantel in Curitiba, Brazil

BACKGROUND AND AIM

Closantel is a widely used anti-parasitic drug that is known to cause ophthalmic problems that lead to blindness. The aim of this study was to investigate the possible electroretinographic changes in sheep that received closantel.

MATERIALS AND METHODS

Twenty-four 30-day-old Suffolk sheep were split into control group (12 animals) and closantel group (12 animals). The latter group received 15 mg/kg of closantel subcutaneously immediately after the first electroretinography (ERG). The ISCEV protocol was used to perform the ERGs pre-dose (0), 7, and 30 days after treatment. Statistical analyses to compare ERG responses using t-test and analysis of variance were performed (p<0.05). Three months later, the animals were euthanized and the eyes and a part of optic nerve were collected for histopathology. Photography of the retina and optic nerve was taken, and measures of the retinal layers were made and analyzed by paired t-test.

RESULTS

Closantel group showed a significant increase of the mean scotopic a-wave amplitude from 0 to 7 days after closantel administration, using a stimulus of 10,000 mcd.s/m2 and a decrease of the mean scotopic and photopic a-wave amplitude (from 7 to 30 days) using the same flash intensity, as well as a decrease in mean photopic b-wave amplitude (from 7 to 30 days) within the group. Control group showed a significant increase of the mean scotopic b-wave implicit time from pre to 30 days after treatment and an increase of the mean scotopic a-wave implicit time from pre to 7 days after treatment, with the stimulus of 10,000 mcd.s/m2. This group also showed a decrease in mean photopic b-wave implicit time (from pre to 30 days after treatment), using a stimulus of 10,000 mcd.s/m2 and a decrease in mean photopic a-wave implicit time from pre to 30 days after treatment, using a stimulus of 3000 mcd.s/m2. The no difference was found in images neither in the measurements of the retina layers.

CONCLUSION

As observed by ERG responses and the histopathology, a dose of 15 mg/kg of closantel does not significantly affect retinal and optic nerve structures in sheep but the electroretinographic results, however, showed alterations on the phototransduction.

Accidental and experimental Closantel intoxication in Uruguayan sheep

Abstract An outbreak of Closantel intoxication in sheep in Uruguay is described. The outbreak occurred in a group of 1300 weaning lambs treated orally with a 10% solution of Closantel. One hundred forty eight lambs showed clinical signs of intoxication and 14 died. The clinical signs included mydriasis, nystagmus, and negative pupillary reflex, bilateral blindness, bump into objects, and lateral movement of the head. No macroscopic lesions were observed. The histological lesions of the retina were cytoplasmic vacuolization in ganglion cells and in cells of the inner and outer nuclear layers with different degrees of atrophy. Vacuolization and axonal degeneration were observed in the optic nerve, with multifocal areas of fibrosis and infiltration by lymphocytes and Gitter cells. To reproduce the intoxication, four sheep were given two, four and 10 times the therapeutic dose of Closantel (0.1g/kg of BW). Only the animals receiving 10 times the recommended dose showed clinical signs. The histological examination of the lesions in experimental sheep showed similar results to those described in the accidental outbreak, except for the absence of optic nerve fibrosis and inflammation, characterizing an acute phase. Axonal myelin sheaths loss, fibroblasts and collagen fibers were observed in the ultrastructural study of the optic nerve of accidental intoxicated animals. The optic nerve of experimentally intoxicated animals had vacuoles that separated the myelin sheaths of axons. To prevent outbreaks it is suggested to weigh the animals before Closantel administration to avoid errors in dose calculation.

Doenças de caprinos diagnosticadas na região Central no Rio Grande do Sul: 114 casos

Foi realizado um estudo retrospectivo dos arquivos do LPV-UFSM e examinados os laudos de necropsias de caprinos realizadas num período de 48 anos (1964 a 2011). Foram analisados 114 laudos de necropsias de caprinos. Deste total, 95 (83,33%) tinham diagnóstico conclusivo e 19 (19,66%) tinham diagnóstico inconclusivo. Dos 95 casos conclusivos, as doenças infecciosas e parasitárias foram as mais prevalentes, seguidas em ordem decrescente de prevalência, pelas doenças metabólicas e nutricionais, intoxicações e toxi-infecções e alterações do desenvolvimento. Outras alterações de diferentes naturezas e etiologias que não se enquadravam nos grupos de doenças acima afetaram cerca de 10% dos caprinos examinados. A hemoncose foi a principal causa de morte de caprinos na área de abrangência do LPV-UFSM. Eimeriose e listeriose também foram causas importantes de morte. Dentre as doenças metabólicas e nutricionais, urolitíase, osteoporose, toxemia da prenhez, desnutrição e doença dos músculos brancos foram as mais prevalentes. Principalmente as doenças infecciosas e parasitárias e as metabólicas e nutricionais ocorreram muitas vezes na forma de surtos, acarretando maiores perdas econômicas associadas.