Mean Faecal Egg Count Reduction Research Articles

Cases of reduced cyathostomin egg-reappearance period and failure of Parascaris equorum egg count reduction following ivermectin treatment as well as survey on pyrantel efficacy on German horse farms

In 2003 and 2004, on a total of 63 different German horse farms, a survey using the faecal egg count reduction (FECR) test was performed to investigate the efficacy of ivermectin (IVM, Ivomec ®) and pyrantel (PYR, Banminth ®) treatment against gastro-intestinal nematodes in a total of 767 horses. IVM treatment resulted in 100% reduction of the cyathostomin egg production 14 and 21 days post-treatment (d.p.t.) on 37 farms. On the remaining five farms, the mean faecal egg count reduction ranged between 97.7 and 99.9%. The mean cyathostomin FECR following PYR treatment ranged between 92.2 and 100% on the 25 farms tested. Therefore, based on the 90% FECR threshold suggested for detection of anthelmintic resistance in horses, neither IVM nor PYR anthelmintic resistance was detected. However, if the thresholds recommended for the detection of resistance in small ruminants were applied, on one and four farms signs of reduced IVM and PYR efficacy, respectively, were observed. In 2005, to further investigate these findings, the cyathostomin egg-reappearance period (ERP) following IVM treatment was examined on six selected farms, two of which were found to show less than 99.8% FECR in the previous survey. On these two latter farms, the ERP was less than 5 weeks, while on the other four it was at least 8 weeks. Earlier investigations described IVM cyathostomin ERP of at least 9 weeks. The efficacy of IVM to reduce Parascaris equorum egg excretion was also studied. On one farm in 2 consecutive years, IVM treatment did not lead to a significant reduction in P. equorum faecal egg counts in one and five young horses, respectively.

Investigation of Anthelmintic Resistance and Deworming Regimens in Horses

AbstractThree studies were conducted to examine parasite resistance and anthelmintic efficacy in the horse. In Experiment 1, 3 fenbendazole (FBZ) treatments (5 mg/kg BW, 10 mg/kg BW, or a larvicidal, 50 mg/kg BW) were administered to horses treated only with FBZ for 18 mo prior. Resistance to FBZ was documented by larval hatch assay and fecal egg count reduction (FECR) tests. In all treatment groups, FECR was not greater than 90%. In Experiment 2, the efficacy of moxidectin (MOX), ivermectin (IVM), and the larvicidal FBZ dose were studied. Mean FECR was 99.91%, 98.73%, and 84.3%, respectively. Animals treated with MOX and IVM had higher (P < 0.05) FECR than the FBZ group. When FECR was analyzed by age, there were no differences among treatment groups in the mature horses, whereas the MOX and IVM groups were higher (P < 0.05) than the FBZ group in the young horses. Experiment 3 determined the efficacy of a year-long quarterly rotation. A farmwide study, including the animals from Experiments 1 and 2, showed a quarterly rotation of pyrantel pamoate (June), IVM (September), larvicidal FBZ (December), and MOX (March) effectively reduced or broke resistance to FBZ, based on FECR tests. The mean FECR for the treatments were 95.86, 100, 97.84, and 100, respectively. These studies indicate that neither frequent use nor larger doses of FBZ will alleviate a FBZ resistance problem in the horse. However, Experiment 3 demonstrated that a rotational regimen can effectively break or reduce FBZ resistance and that FBZ can be successfully implemented in a rotational scheme subsequent to prior resistance.

Benzimidazole resistance in cyathostomin populations on horse farms in western Anatolia, Turkey.

A cross-sectional survey was performed on ten stud farms in western Anatolia, Turkey, in order to provide the first information on the problem of anthelmintic resistance in equine strongyles in this country. Benzimidazole (BZ) resistant cyathostomin populations were detected on seven farms if pre- and post-treatment egg counts are compared in treated animals and the resistance is defined as a mean faecal egg count reduction (FECR) of <95% with a lower 95% confidence limit of <90%. Egg hatch tests using an ED(50) of 0.1 microg/ml thiabendazole as the cut-off value confirmed BZ resistance on four of the seven farms. The probable reasons for the occurrence of BZ resistance are discussed. Resistance to pyrantel embonate or macrocyclic lactones, evaluated on five and six farms, respectively, was not detected using the FECR test.

A study to evaluate the field efficacy of ivermectin, fenbendazole and pyrantel pamoate, with preliminary observations on the efficacy of doramectin, as anthelmintics in horses.

The efficacy of ivermectin, fenbendazole, pyrantel pamoate and doramectin was evaluated under field conditions at 2 sites in the Free State Province of South Africa. The study involved 25 horses at each site, divided into 5 groups of equal size. Ivermectin, fenbendazole and pyrantel pamoate were administered orally at doses of 0.2, 10 and 19 mg/kg respectively. Doramectin was administered by intramuscular injection at a dose of 0.2 mg/kg. Treatment efficacy was based on the mean faecal egg count reduction 14 days post treatment. At site A a faecal egg count reduction of 100% was found after treatment with ivermectin, fenbendazole and doramectin. A 96.1% reduction was found after treatment with pyrantel pamoate. At site B ivermectin and doramectin produced a 100% reduction in faecal egg counts, fenbendazole produced an 80.8% reduction and pyrantel pamoate a 94.1% reduction. Doramectin produced a 100% reduction in faecal egg counts at both sites, despite not being registered for use in horses. In addition, the results indicated reduced efficacy of fenbendazole at site B, which suggested benzimidazole resistance. Larval cultures showed that cyathostomes accounted for between 86 and 96% of pre-treatment parasite burdens at both sites. Other helminths identified in the faecal samples were Strongylus spp. and Trichostrongylus axei.

Faecal egg count reduction percentage calculations to detect anthelmintic resistance in Oesophagostomum spp. in pigs

The results of four alternative methods of mean faecal egg count reduction percentage (FECR%) calculations were evaluated and compared using data obtained for Oesophagostomum spp. from ten sow herds. The estimates of FECR% and 95% confidence limits obtained using the four methods were different. However, there were few discrepancies in the final decision as to whether a given herd carried drug resistant isolates or not. The methods that used geometric means were more appropriate than those that used the arithmetic mean as the measure of central tendency for eggs per gram of faeces (EPG) values. The use of geometric mean EPG values in calculations has been criticized from several viewpoints, one of which is that its use reduces the comparability of reports between laboratories. If the geometric mean is to be used as we suggest in FECR% calculations, the appropriate references, number of animals in each group, minimum and maximum EPG values and the factor added to zero EPG counts should be reported in order to improve the comparability. The difficulty in obtaining groups with similar pre-treatment EPG values in field situations suggested the inclusion of pre-treatment EPG values in the calculations as an adjustment procedure. The importance of including a non-treated control group in calculations was demonstrated during this study. Therefore, we suggest the use of geometric mean EPG values, to include pre-treatment EPG values and to include the egg counts from the control group in FECR% calculations. The interpretation of the resulting FECR estimate may be different according to the purpose for which the testing procedure is carried out, e.g. survey in detecting anthelmintic resistance, control field tests, etc.