The horse nematode Parascaris equorum: in vitro experiments and evaluation of anthelmintic resistance

Parascaris equorum is a worldwide-spread parasite which affects young horses and donkeys. Three different classes of anthelmintic drugs are commonly used to control horse parasites: Benzimidazoles (BM), Tetrahydropyrimidine (Pyrantel - PYR) and Macrocyclic Lactones (ML). Benzimidazoles are nowadays the preferred drug to treat P. equorum infections since this parasite has developed resistance to ML in multiple countries and to Pyrantel (described only in the USA). The development of anthelmintic resistance to ML is thought to be correlated with exclusive and/or excessively frequent use of these drugs in young foals; this is why constantly monitoring the effectiveness of these drugs is crucial meanwhile a new diagnostic method, which allows to detect early infections, is developed. In this study, eggs of P. equorum were isolated from feces of contaminated foals, hatched and left develop into larvae, then exposed to Thiabendazole (TBZ) to investigate if the parasite was gaining resistance to this drug. After the exposure to TBZ was also analyzed the expression of two P-glycoproteins, p-gp 11 and p-gp 16, which seem to be responsible for the development of resistance in similar drugs.