Tolerance and Efficacy of Emamectin Benzoate and Ivermectin for the Treatment of Pseudocapillaria tomentosa in Laboratory Zebrafish (Danio rerio)

Abstract

Tolerance of adult zebrafish and efficacy of emamectin benzoate and ivermectin in eliminating Pseudocapillaria tomentosa infection were evaluated. In the tolerance study, behavioral changes, fecundity, histopathology, and mortality were evaluated for in-feed administration of emamectin (0.05, 0.10, and 0.25 mg/kg) and ivermectin (0.05 and 0.10 mg/kg). All doses of emamectin were well tolerated. Ivermectin 0.05 mg/kg administration resulted in mild behavioral changes and a transient decrease in fecundity. Ivermectin 0.10 mg/kg administration resulted in severe behavioral changes and some mortality. In the efficacy study, emamectin (0.05 and 0.25 mg/kg) and ivermectin (0.05 mg/kg) were evaluated for their efficacy in eliminating P. tomentosa infection. Emamectin reduced parasite burden in infected zebrafish, and ivermectin eliminated intestinal nematode infections. Despite a small margin of safety, ivermectin 0.05 mg/kg was effective at eliminating P. tomentosa infection in adult zebrafish. Higher doses or a longer course of treatment may be needed for complete elimination of P. tomentosa infection using emamectin. In this study, we propose two possible treatments for intestinal nematode infections in zebrafish.

Housing Environment Affects Baseline Anxiety in Zebrafish

“…In a study where single-housed fish kept in a barren environment were compared with those in an enriched (i.e. greenery added) environment, there was no difference observed in the novel tank diving or light-dark preference tests [7]. Given our experimental design we cannot completely rule out the contribution of the greenery, but in light of the existing data in the literature, we think that fish density plays the primary role in determining the difference in anxiety phenotype.…”

“…Despite the lack of differences in bottom-dwelling among the four housing conditions, Collymore and colleagues [7], nevertheless, concluded that housing fish individually in a barren environment enhances anxiety and that enrichment It would appear that previously under-valued aspects of experimental design may influence, in subtle ways, the data obtained, particularly when behavioral parameters are being measured. While testing conditions often receive the highest attention, methods used for housing and handling may be currently insufficiently emphasized or inadequately reported.…”

“…Experimentally, the specific size of the bottom compartment can vary among studies. Collymore and colleagues [7] designated the bottom half of their test tanks in measuring tank-diving. They compared bottom-dwelling in group-housed versus single-housed, either in barren tanks or in tanks enriched with plants.…”

Recommendations for Health Monitoring and Reporting for Zebrafish Research Facilities

“…Transmission can occur in as little as 1 month. 44 P. tomentosa has also been associated with an increased incidence of tumor formation in zebrafish exposed to carcinogens. 2 As more zebrafish are being used for cancer research, this is another possible confounding agent.…”

“…Three recent publications described effective treatments for zebrafish infected with this parasite. [44][45][46][47] These include use of fenbendazole, ivermectin, emamectin benzoate, mebendazole and praziquantel.…”