RESUMO
Anthelmintic resistance in equine cyathostomins has been described worldwide, with resistance to the benzimidazole class being particularly widespread. The status of anthelmintic efficacy in Cuba has been virtually unknown due to the lack of equine labelled products. One recent report documented suboptimal efficacy levels of extra-label albendazole products against cyathostomins, but it remains unknown to which extent benzimidazole resistance exists in the population. The aim of the present study was to evaluate the anthelmintic efficacy of two benzimidazole products labelled for equines, fenbendazole and oxibendazole. A fecal egg count reduction test (FECRT) was carried out on 132 horses aged 4â¯months to 18â¯years in 14 herds, belonging to six provinces. Ten herds exhibited signs of resistance to at least one of the benzimidazoles (mean FECRT<90%). Overall, oxibendazole exhibited higher efficacy than fenbendazole (pâ¯=â¯0.0062), and higher efficacy levels were found in horses never dewormed before compared to those treated within 3-12â¯months prior to the study (pâ¯=â¯0.0015). Pre-treatment larval cultures revealed the presence of large strongyles and cyathostomin larvae in all herds, while only cyathostomin larvae were detected post treatment. The present work is the first report of anthelmintic resistance in equine cyathostomins in Cuba, and suggests pre-selection for resistant strains by extra-label use of albendazole on the studied farms.
Assuntos
Anti-Helmínticos/farmacologia , Anti-Helmínticos/uso terapêutico , Resistência a Medicamentos , Infecções Equinas por Strongyloidea/tratamento farmacológico , Strongyloidea/efeitos dos fármacos , Animais , Benzimidazóis/farmacologia , Cuba , Fezes/parasitologia , Feminino , Cavalos/parasitologia , Masculino , Contagem de Ovos de Parasitas/veterináriaRESUMO
Increasing levels of anthelmintic resistance observed in equine cyathostomin parasites have led to recommendations of selective anthelmintic treatment strategies to lower the selection pressure favoring resistant populations. This principle is based on determining strongyle fecal egg counts from all herd members, and treating those exceeding a predetermined treatment cutoff. However, epidemiological information is lacking from horses kept under tropical conditions, where parasite burdens may be of a different composition and magnitude compared to those of horses kept under temperate climate conditions. The aim of the present work was to characterize the strongylid fauna in horses kept in tropical Camagüey, Cuba and identify risk factors associated with strongylid and ascarid egg counts. A total of 396 horses from eight different establishments were included in the study. Coprocultures revealed that Strongylus vulgaris and cyathostomins, sensu lato, were detected in all of those establishments. Prevalence and mean value of strongylid eggs per gram of feces were 97% and 1436, respectively. Eggs of Parascaris spp. were observed in 10% of horses. A multivariate mixed linear model identified sex (p=0.022), month (p=0.044), operation type (p=0.037) and time since last deworming (p<0.001) to be significantly associated in with the magnitude of strongylid fecal egg counts. A multivariate logistic regression identified horses less than two years of age (p=0.010) and horses not receiving anthelmintic treatment (p<0.001) to be significantly more likely to harbor Parascaris spp. parasites. The high magnitude and prevalence of strongylid fecal egg counts observed and the common occurrence of S. vulgaris suggest that strongylid parasite burdens are substantially different from those typically observed in managed equines kept under more temperate conditions.
Assuntos
Fezes/parasitologia , Helmintíase Animal/parasitologia , Helmintos/fisiologia , Doenças dos Cavalos/parasitologia , Contagem de Ovos de Parasitas/veterinária , Animais , Anti-Helmínticos/administração & dosagem , Anti-Helmínticos/uso terapêutico , Cuba/epidemiologia , Resistência a Medicamentos , Feminino , Helmintíase Animal/tratamento farmacológico , Helmintíase Animal/epidemiologia , Helmintos/efeitos dos fármacos , Doenças dos Cavalos/tratamento farmacológico , Doenças dos Cavalos/epidemiologia , Cavalos , Masculino , Prevalência , Fatores de RiscoRESUMO
The large roundworm of horses, Parascaris equorum is considered ubiquitous in breeding operations, and is regarded as a most important helminth pathogen of foals. Over the past decade, this parasite has been reported increasingly resistant to anthelmintic drugs worldwide. This paper reports analysis of the population genetic structure of P. equorum. Adult parasites (n=194) collected from Sweden, Norway, Iceland, Germany, Brazil and the USA were investigated by amplified restriction fragment length polymorphism (AFLP) analysis. The genetic variation was low (Hj=0.12-0.4), for the global population of worms. This was accompanied by a weak degree of population structure (Fst=0.2), low gene flow (Nm=1.0) and low mutation rate (4 Nµ=0.07). Thus, the low genetic diversity is probably a result of a low mutation rate in DNA, although the gene flow (due to global movement of horses) is large enough to allow the spread of novel mutations. Surprisingly, isolates from Icelandic horses were not found to be different from other isolates, in spite of the fact that these have been isolated for thousands of years. The study indicates that the global P. equorum population is essentially homogenous, and continents do not appear to be strong barriers for the population structure of this species. Consequently, the potential spread of rare anthelmintic resistance genes may be rapid in a homogenous population.