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E-Book 3rd Congress

  • Assessing the Efficacy of the MacMaster Fecal Technique in Identifying Oxfendazole efficacy in Parascaris equorum
  • Negar Najafifard,1 Fatemeh Jalousian,2,* Negar Hemmati,3
    1. DVM student, faculty of veterinary medicine, Tehran university
    2. Department of parasitology, faculty of veterinary medicine, Tehran university
    3. DVM student, faculty of veterinary medicine, Tehran university


  • Introduction: The McMaster method is widely used in veterinary parasitology to accurately measure the quantity of eggs in stool samples. The technique employs a McMaster slide, which includes a chamber where a specific volume of stool suspension is added. Researchers examine the checkered pattern on the slide to count the number of eggs present in each square. This method is particularly valuable for monitoring resistance to anti-parasitic drugs. To assess resistance, the number of parasite eggs in fecal samples is counted both before and after treatment, and the results are subsequently compared. The MacMaster method is highly regarded as an effective, cost-efficient, and time-saving approach for evaluating resistance to anti-parasitic treatments. The main objective of this study was to evaluate the effectiveness of Oxfendazole as a treatment for Parascaris equorum infections in stable horses located in Tehran province.
  • Methods: In this study, we collected a total of 38 samples of horse fecal samples directly by performing rectal touch. These samples were then transferred to the parasitology laboratory at the Faculty of Veterinary Medicine, University of Tehran. To detect the presence of Parascaris equorum eggs, we employed a flotation technique with saturated sodium chloride solution (1.202g/m density at 25°C). The eggs of P. equorum are easily distinguishable from those of other parasites and measure approximately 90-100 µm in diameter. Subsequently, we counted the number of eggs in each sample using the McMaster method. For horses diagnosed with Parascaris equorum infection, we administered treatment with oxfendazole. After the completion of treatment, we conducted a follow-up sampling on the fourteenth day, and the stool samples collected after this period were further examined using the McMaster method.
  • Results: The results of the stool test showed that 4 horses, which were 10.5% of the tested population and aged 36 months or older, were infected with Parascaris equorum. The average egg count per gram of feces in these infected horses was determined to be 625±132.28. After treating these 4 infected cases with oxfendazole, a subsequent test was conducted on the 14th day to evaluate the effectiveness of the drug. The results displayed acceptable efficiency of the treatment, as the average number of eggs observed in the feces on the 14th day after treatment was 28.29± 25.5. Furthermore, the drug exhibited an efficiency rate exceeding 65%.
  • Conclusion: The present study discovered the presence of Parascaris equorum infection in horses kept in stable conditions. The significant daily excretion of Parascaris equorum eggs makes a stool test a suitable method for detecting the presence of Ascarid eggs. To date, there have been no reported incidents of Parascaris equorum developing resistance towards fenbendazoles on a global scale. However, the emergence of resistance to this specific anthelmintic among cyathostomins presents a significant challenge. The study's findings exhibited a marked reduction in Fecal Egg Count (FECRT>95%) and a Low Confidence (LCL>90%) when employing Oxfendazole. Anti-parasitic treatment in horses should be administered following diagnostic testing, while also avoiding the excessive use of anthelmintic drugs. The concurrent application of multiple drugs can help prevent the development of drug resistance within the parasite population. To effectively control and prevent infection with the Parascaris equorum parasite, it is essential to implement measures such as stable sterilization and raise awareness among horse owners regarding its transmission among foals, mares, and stallions. In the context of the valuable horse breeding industry, the McMaster method emerges as a cost-effective approach for monitoring the efficacy of anti-parasitic drugs. By training veterinary experts and establishing a standardized McMaster test protocol, the effectiveness of expensive drugs can be significantly enhanced.
  • Keywords: anthelmintic resistance, cyathostomins, equine parasitology, fecal egg counts.