Efficacy of in-feed-administered ivermectin on Elaphostrongylus cervi first-stage excretion in red deer (Cervus elaphus)

Abstract

Elaphostrongylus cervi (Nematoda, Metastrongyloidea) is an extrapulmonary lungworm of red deer (Cervus elaphus), which has a wide natural distribution in Eurasia. The presence and seasonal pattern of excretion of large spiny-tailed protostrongylid larvae comparable to the descriptions of first-stage E. cervi in fecal samples (prevalence of 66.47%) from southern and central Spain were recently reported for the first time (Vicente and Gortazar 2001; Vicente et al. 2005). Although individual anthelmintic treatment allows administrating precise drug dosage, such a manipulation would be highly stressful for wild animals. Moreover, it would require the involvement of many people. Management problems could be overcome by using in-feed drug formulations. Only drugs known to be safe and having a broad therapeutic spectrum should be used (Rajkovic-Janje et al. 2004). Ivermectin is a semisynthetic derivative of avermectin characterized by an exceptional potency and wide spectrum of activity against many parasitic nematodes and arthropods. This compound has stimulated interest in its application in the treatment and prevention of parasitic problems common to free-ranging species of wildlife (Kocan 1985 ; Fernandez de Mera et al. 2004). The control of diseases in hunting-managed animals is of concern (Peterson 1991). In particular, E. cervi has considerable pathological consequences for other wild and domestic ungulates, thus being of importance for wildlife managers, livestock breeders and sanitary authorities (Gajadhar and Tessaro 1995; Pusterla 1998). The aim of this study was to assess the efficacy of a treatment usually employed in sanitary programs of semi-extensive red deer hunting ranges: the use of an in-feed 0.6% ivermectin premix formulation under field conditions. A simple case-control study was designed. Naturally infected adult hinds (n=132) fromMontes de Toledo (Ciudad Real province, Spain) were captured from the wild. During May–June 2004, the control group (n=20) and the treated group (n=112) were separately kept in two fenced grounds of similar characteristics. Oral in-feed ivermectin (Ivomec Premix 0.6% Merial Sharp & Dohme, The Netherlands) was mixed with commercial deer feed at a concentration of 7.5 ppm and administrated ad libitum during 7 days. The control group was fed with untreated deer feed. We employed fecal examination as a useful indicator of relative parasite abundance (Todd et al. 1970; Mason 1989). We collected fresh fecal pellet groups (11–22) on day 0 (prior to treatment) and then fortnightly until the end of the study. Protostrongylid larvae were extracted by coprological analysis in less than 24 h from 8–10 g of feces collected using the beaker extraction method as described by Forrester and Lankester (1997). The larvae were quantified in a Favatti counting chamber and expressed as the number of L1 per gram of feces. The terms prevalence and intensity of excretion are used as in Margolis et al. (1982). L1 counts were log10+1-transformed and Mann–Whitney’s nonparametric test (Siegel 1990) was employed to compare treatment effectiveness on L1 excretion intensity between (1) treatment groups throughout the different sampling dates and between (2) pretreatment and post-treatment prevalence separately for each group. Similarly, chi-square tests were employed to test for differences in prevalence. The significance level was established at P 0.05; ZM-W=0.75, P>0.05, respectively, I. G. Fernandez de Mera . J. Vicente (*) . C. Gortazar Instituto de Investigacion en Recursos Cinegeticos IREC (CSIC-UCLM-JCCM), Ronda de Toledo s/n, 13005 Ciudad Real, Spain e-mail: jvicente@irec.uclm.es Tel.: +34-926-225450 Fax: +34-926-225451