Longitudinal study for anthelmintic efficacy against intestinal helminths in naturally exposed Lithuanian village dogs: critical analysis of feasibility and limitations.

Abstract

The efficacy of anthelmintic treatment at 1, 3, and 6&#xa0;month intervals was evaluated in a prospective controlled field study with naturally exposed Lithuanian village dogs by monthly coproscopy during 1&#xa0;year. A placebo-treated control group (C) (n&#x2009;=&#x2009;202) and groups treated with two broad-spectrum anthelmintics, febantel/pyrantel-embonate/praziquantel (Drontal&#xae; Plus, Bayer) (D1, D3, D6; n&#x2009;=&#x2009;113-117) and emodepside/praziquantel (Profender&#xae;, Bayer) (P1, P3, P6; n&#x2009;=&#x2009;114-119), were included. At the beginning of the study, eggs of Toxocara canis (4.02%) and T. cati (0.44%) identified morphometrically and/or molecularly and eggs of taeniid- (0.78%) and Capillaria-like eggs (5.03%) were present in the feces without significant differences in prevalence between groups. Significant decreases in excretion of T. canis eggs was found 1&#xa0;month after the treatment with Drontal&#xae; Plus in February (D1) and with Profender&#xae; in October (P1), November (P1), December (P3), February (P1), and March (P1, P3), as compared to controls in the same months. The incidence of egg excretion per dog at least once a year was significantly lower in group P1 for T. canis (4.24%; p&#x2009;<&#x2009;0.01) and in groups D1, P1 for taeniid eggs (0%; p&#x2009;<&#x2009;0.01 and p&#x2009;<&#x2009;0.001), when compared to controls (16.96 and 6.70%, respectively). A critical analyses of factors possibly responsible for intestinal passage of canine helminth eggs revealed that chained dogs excreted T. canis eggs more frequently 1&#xa0;month after treatment compared to dogs in pens, particularly from November to March (p&#x2009;=&#x2009;0.01). The incidence of single detection of T. cati eggs was significantly increased in chained dogs (12.46%) as compared to fenced dogs (1.08%; p&#x2009;=&#x2009;0.0001).