EVALUATION OF IVERMECTIN ORAL AND INJECTABLE FORMULATIONS AGAINST SUSCEPTIBLE AND RESISTANT GASTROINTESTINAL NEMATODES IN CATTLE

CANTON, C.1; CEBALLOS, L.1; MORENO, L.1; FIEL, C.2; DOMÍNGUEZ, P.1,2; BERNAT, G. 2,3; LANUSSE, C.1; ALVAREZ, L.1

Liverpool

Congreso; Congreso Mundial de la World Association of Veterinary Parasitology; 2015

World Association for the Advancement of Veterinary Parasitology

It is well known that ivermectin (IVM) is highly efficacious against susceptible gastrointestinal (GI) nematodes following both oral and subcutaneous (SC) treatments. However, enhanced efficacy has been reported for the oral route in the presence of resistant nematodes. The current study evaluated the comparative pharmacokinetic (PK) behaviour and clinical efficacy against susceptible and resistant nematodes observed after IVM administration by the oral and SC routes to cattle. The trial was conducted in two commercial farms. Farm A with predominance of an IVM-susceptible nematode population and Farm B with well established IVM-resistant nematode populations. Forty five (45) male calves (from each Farm) naturally infected with GI nematodes susceptible/resistant to IVM were randomly allocated into three groups (n= 15): untreated (control) and IVM treated by the SC and oral route at 0.2 mg/kg. Eight (8) animals from each treated group (Farm A) were randomly selected to perform the PK study. Plasma and faecal samples were taken from those animals up-to 25 days post-treatment. Drug concentrations were measured by HPLC. The clinical efficacy was determined at 16 days after treatment by Faecal Egg Count Reduction Test (FECRT). The FECRT in Farm A were 92.8% (SC treatment) and 91.3% (oral treatment) confirming that both routes of administration reached equivalent efficacy against susceptible nematodes. The IVM systemic availability (estimated as the area under the plasma concentration vs time curve) obtained after its SC administration (421.02 ± 70.25 ng.d/ml) was higher (P