Evaluation of a laboratory test to detect resistance to closantel in Haemonchus contortus

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.

Copper oxide and closantel prevent alterations in hepatic energetic metabolism and reduce inflammation in Haemonchus contortus infection

The aims of this study were to evaluate if the use of copper oxide wire particles, isolated or in association with closantel, in lambs infected with Haemonchus contortus enhances the anthelmintic efficacy of closantel, as well as to evaluate the effects of treatment in hepatic energy metabolism, inflammatory markers and hematological and biochemical tests. The lambs were randomly divided into five groups (6 animals each), as follows: uninfected animals (Control); animals infected with H. contortus (HC); infected and treated with closantel (HC + CL); infected and treated with copper oxide wire particles (HC + Cu); and infected and treated with closantel plus copper oxide wire particles (HC + CL + Cu). The animals of infected groups were infected orally with H. contortus (5,000 L3 -larvae) and on day 14 post infection (p.i) the treatments were initiated. The egg per gram of feces (EPG), butyrylcholinesterase (BuChE), myeloperoxidase (MPO), adenylate kinase (AK) and pyruvate kinase (PK) activities and hematological and biochemical tests were evaluated. Treatments with copper oxide (isolated and associated) were able to reduce the EPG count on days 28, 35, 42 and 49 p.i when compared to HC group, while closantel was able to reduce EPG only from day 35 p.i. Moreover, treatment with closantel (isolated or associated) was able to prevent the inhibition of hepatic AK and PK activities caused by H. contortus infection, which may contribute to efficient intracellular energetic communication in order to maintain the balance between cellular ATP consumption and production. Butyrylcholinesterase and MPO activities were higher in infected lambs compared to uninfected, while treated groups showed lower enzymatic activity compared to the group HC. The use of all therapeutic protocols was able to reduce the EPG count. Based on these evidences, the use of copper oxide plus closantel may be considered an alternative to treat lambs infected by H. contortus.