moxidectin and oxibendazole

Cyathostomins can cause a severe inflammation of equine large intestine characterized by substantial ventral edema and pronounced protein loss. Anthelmintic treatment of horses can result in a localized inflammatory response in the colonic mucosa of clinically normal horses. The aim of this study was to evaluate the systemic inflammatory response of ponies naturally infected with cyathostomins to single dose representatives of three anthelmintic drug classes, namely, oxibendazole, pyrantel pamoate, and moxidectin. Thirty ponies aged between 1 and 18 years of age were allocated to one of three anthelmintic treatments groups. Anthelmintic efficacy was evaluated using the fecal egg count reduction test performed weekly between 2 and 8 weeks post-treatment. Inflammatory responses were evaluated on days 0, 1, 3, 5, and 14 after treatment using hematology, measurement of the acute phase inflammatory markers serum amyloid A, fibrinogen, haptoglobin, and iron, and real-time PCR measurement of expression of the genes for interleukins 1-β and -10, tumor necrosis factor-α, and interferon-γ. There were subtle inflammatory responses to treatment, but cytokine expression was significantly associated with the interaction term between treatment group and anthelmintic efficacy (P<0.05). Of the acute phase markers, only fibrinogen associated with treatment group. The findings suggest that systemic inflammatory responses subsequent to anthelmintic treatment of cyathostomin infection are minimal. It is possible that this response is 'buffered' by anti-inflammatory products of the parasites and/or the anti-inflammatory effects of the macrocyclic lactones.

Topics: Acute-Phase Proteins; Animals; Antinematodal Agents; Benzimidazoles; Cytokines; Feces; Female; Gene Expression Regulation; Horse Diseases; Horses; Macrolides; Male; Pyrantel Pamoate; Strongylida Infections; Strongyloidea

An alternative control regimen for drug-resistant parasites is combination deworming, where two drugs with different modes of action are administered simultaneously to target the same parasite. Few studies have investigated this in equine cyathostomins. We previously reported that an oxibendazole (OBZ) and pyrantel pamoate (PYR) combination was not sustainable against a cyathostomin population with high levels of OBZ and PYR resistance. This study consisted of a field study and two computer simulations to evaluate the efficacy of a moxidectin-oxibendazole (MOX-OBZ) combination against the same cyathostomin population. In the field study, anthelmintic treatments occurred when ten horses exceeded 100 eggs per gram. Fecal egg counts and efficacy evaluations were performed every two weeks. The two simulations utilized weather data as well as equine and parasite population parameters from the field study. The first simulation repeated the treatment schedule used in the field study over a 40 year period. The second evaluated efficacies of combination treatments using selective therapy over 40 years. In the field study, efficacies of MOX and both combination treatments were 100%. The egg reappearance period for MOX was 16 weeks, and the two combination treatments were 12 and 18 weeks. The first (46.7%) and last (40.1%) OBZ efficacies were not significantly different from each other. In the simulation study, the combination treatment delayed MOX resistance development compared to when MOX was used as a single active. This occurred despite the low efficacy of OBZ. The second set of simulations identified combination treatments used with selective therapy to be the most effective at delaying MOX resistance. Overall, this study supports the use of combination treatment against drug-resistant cyathostomins, when one of the actives exhibits high efficacy, and demonstrates benefits of this approach despite substantially lowered efficacy of the other active ingredient.

Topics: Animals; Anthelmintics; Benzimidazoles; Drug Resistance; Drug Therapy, Combination; Feces; Female; Horse Diseases; Horses; Macrolides; Parasite Egg Count; Strongyle Infections, Equine

The main purpose of the research was to determine if three weekly samplings would produce consistent results for low strongyle egg shedders, generally associated with older horses. Strongyle egg counts per gram of feces (EPG) were done for 661 Thoroughbred mares on 14 farms in 2012-2013 once a week for three consecutive weeks. None of the mares had been treated with ivermectin or moxidectin for more than 90 days and with fenbendazole, oxibendazole, or pyrantel pamoate for more than 60 days. Strongyle EPG count data indicated that 38.3% of the mares were positive at first and second sampling, and 37.8%--at third sampling. There were 5.6-63.3% of horses positive per farm. Correlations between EPG count data in all three weeks are quite high (Rs = 0.84, p<0.001). Level of horse infection was found to be dependent on horse age, type of farm and individual characters of horse. This study documented that strongyle egg counts (EPGs) from individual horses did not differ significantly between weeks. Thus, a single strongyle EPG count can be interpreted as indicative of the level of egg shedding for a given horse. These data support the current trend of not deworming all adult horses on a farm, so that high shedders can be identified and treated. This saves horse owners money and reduces development of potential drug resistance of parasites because of less frequent usage of antiparasitic compounds. Information from this study helps to conclude recommendations for parasite control in horses globally.

Topics: Animal Husbandry; Animals; Anthelmintics; Antiparasitic Agents; Benzimidazoles; Drug Resistance; Feces; Female; Fenbendazole; Horses; Ivermectin; Kentucky; Macrolides; Parasite Egg Count; Pyrantel Pamoate; Strongyle Infections, Equine; Strongylus

Cyathostome populations in horses on two farms located in central Italy with a history of fenbendazole (FBZ) resistance were investigated with the Faecal Egg Count Reduction Test to evaluate the susceptibility to oxibendazole and moxidectin. Faecal eggs were collected pre- and post-treatment on each farm and molecularly examined with a Reverse Line Blot (RLB) assay able to unequivocally detect and identify 13 cyathostome species. Resistance to FBZ was confirmed on both farms, while oxibendazole and moxidectin demonstrated 97% and 100% efficacy, respectively. Overall eight species of cyathostomes (Coronocyclus labiatus, Cylicocyclus ashworthi, Cylicocyclus nassatus, Cyathostomum catinatum, Cylicostephanus longibursatus, Cylicostephanus goldi, Cylicostephanus calicatus and Cylicocyclus insigne) were identified in pre-treatment samples. Coronocyclus labiatus and C. goldi were identified after treatment with FBZ while C. calicatus and C. labiatus were shown to be <100% susceptible to oxibendazole. These data confirm that resistance to benzimidazoles is established in cyathostome populations from horse farms in Italy and that they are susceptible to moxidectin. The oxibendazole has been successfully demonstrated for the first time as effective against Italian populations of cyathostomes resistant to other benzimidazoles. The RLB assay herein used showed to be useful to study the distribution of these parasitic populations at species level under field conditions and could represent a powerful tool in broader investigation of drug resistance in horse farms from several countries.

Topics: Animals; Antinematodal Agents; Benzimidazoles; Drug Resistance; Feces; Fenbendazole; Horses; Macrolides; Nucleic Acid Hybridization; Oligonucleotide Probes; Parasite Egg Count; Parasitic Sensitivity Tests; Random Allocation; Species Specificity; Strongyle Infections, Equine; Strongyloidea

To compare the efficacy of moxidectin to ivermectin, oxibendazole and morantel against some gastrointestinal nematodes in horses.. Faecal egg count reduction after treatment.. A farm was selected where the population of small strongyles in horses was known to be resistant to oxibendazole. Horses were allocated to treatment groups based on faecal egg counts. After treatment, faecal samples were taken up to 109 days after treatment and faecal egg counts estimated. Faecal cultures were used to estimate the contribution of small and large strongyles to the faecal egg counts at each sampling.. Moxidectin (0.4 mg/kg) suppressed faecal egg counts for 109 days after treatment in most horses compared to 40 days with ivermectin (0.2 mg/kg), 13 days with morantel (9.4 mg/kg) and less than 13 days with oxibendazole (10 mg/kg). Most of the faecal egg count was attributable to small strongyles based on faecal culture, although Strongylus vulgaris was present in some samples in low numbers. Oxibendazole resistance in small strongyles was confirmed and a less than expected efficacy of morantel was also seen.. Moxidectin was highly effective in reducing faecal egg counts after treatment for at least 12 weeks and up to 16 weeks in most horses. These horses were infected with a population of small strongyles known to be resistant to oxibendazole and possibly morantel. The duration of the reduction in faecal egg counts after treatment with moxidectin (0.4 mg/kg) was at least twice that of ivermectin (0.2 mg/kg) and greater than four times that for morantel and oxibendazole.

Topics: Animals; Anti-Bacterial Agents; Antinematodal Agents; Benzimidazoles; Drug Resistance; Feces; Female; Horses; Ivermectin; Macrolides; Male; Morantel; Ointments; Parasite Egg Count; Random Allocation; Strongyle Infections, Equine; Strongylus