Outbreak of severe foot rot associated with benign Dichelobacter nodosus in an Alpine ibex colony in the Swiss Prealps

Abstract

An outbreak of foot rot occurred in the ibex colony "Vanil Noir" in Switzerland from May to December 2014. This article describes field observations and the analyses carried out on the limbs of 3 animals submitted for postmortem examination. Disease signs observed in the field included lameness, poor body condition and overgrown hooves. Macroscopic examination of selected limbs revealed severe lesions in all of them, including interdigital inflammation with ulceration and malodorous exudation. Histological changes were consistent with chronic laminitis with bone resorption, which was not detected at radiographical examination. Grocott-positive organisms compatible with Dichelobacternodosus were detected in the lesions. Samples collected from the lesions were positive by polymerase chain reaction for benign D. nodosus, which is typically associated with only mild lesions in domestic sheep. Whether D. nodosus is endemic in the colony or had previously been transmitted from sympatric domestic livestock is unclear. The unusual warm and humid weather conditions in 2014 may well have contributed to the outbreak.

Identifying maintenance hosts for infection with Dichelobacter nodosus in free-ranging wild ruminants in Switzerland: A prevalence study

“…Two adult male Alpine ibex, the one infected with benign strains and the other with virulent strains, showed severe lesions consistent with footrot. These findings are in line with previous reports documenting that the presence of benign and virulent strains of D. nodosus can be associated with severe foot lesions in Alpine ibex that are comparable to typical lesions of footrot in sheep [1,4]. The classification into benign and virulent strains was developed in the framework of a study conducted in sheep [10,33] and may only be applicable to sheep.…”

“…In free-ranging wildlife, footrot has been documented in several European countries, affecting Alpine ibex (Capra ibex ibex) and mufflon (Ovis orientalis orientalis) [1,[4][5][6] (Meneguz, Frey and Ryser, unpublished data). Since the treatment of wild ungulates in the field is challenging, expensive, and neither feasible nor desired by wildlife managers, severe lesions do not just affect animal welfare but typically result in death [4,6]. Considering that Alpine ibex in Switzerland have just recovered from the verge of extinction in the 20 th century [7], outbreaks of footrot may be relevant to species conservation.…”

“…In sheep, mild and severe clinical forms of footrot have been shown to be associated with the presence of strains of D. nodosus carrying either the AprB2 or AprV2 genes, respectively, which encode for the subtilisin-like extracellular proteases playing a key role as virulence factors [8,10], thus referred to as "benign" and "virulent". However, in Alpine ibex, the benign strain was also found in association with severe lesions [4]. Furthermore, both types of strains of D. nodosus have been detected in the absence of lesions in sheep, cattle, goats and swine [11][12][13][14], suggesting the existence of species-specific differences in disease susceptibility and the involvement of other individual or environmental risk factors in the disease course.…”

The prevalence of Dichelobacter nodosus in clinically footrot-free sheep flocks: a comparative field study on elimination strategies

“…In Sweden benign D nodosus is often associated with underrunning (score ≥ 3 lesions) [31]. Similarly, clinical impact caused by benign D nodosus was reported from a wild-range alpine ibex colony in Switzerland [32]. Therefore, further research is required to determine whether the PCR classification used in this study corresponds to clinical presentation, if considered as elimination tool in other species like goats or other populations, since the genetic background of the host also plays a role [33].…”

Klaueninfektionen beim Schaf – Therapiemöglichkeiten in der tierärztlichen Praxis unter besonderer Berück sichtigung der Moderhinkebekämpfung

“…Regelmäßige Herdenbehandlungen als Teil des beschriebenen Maßnahmenbündels können zur Moderhinkefreiheit führen, wenn es über mehrere Jahre gelingt, die Zahl latent infizierter Tiere kontinuierlich, letztlich auf Null zu senken. Für einige Herden ist dies utopisch, solange Kontakt zu infizierten Nachbarherden oder Wildtierpopulationen (Mufflons, Steinböcke) besteht (102). Für diese Betriebe stellt die nachhaltige Kontrolle das maximal erreichbare Behandlungsziel dar.…”