High Prevalence of Orodental Disorders in South Brazilian Cart Horses: Walking a Tightrope Between Animal Welfare and Socioeconomic Inevitability

The Socioeconomic Impact of Diseases of Working Equids in Low and Middle-Income Countries: A Critical Review

Working equids provide a crucial contribution to the livelihoods and food security of communities in low- and middle-income countries (LMICs). Nevertheless, they are a neglected category within animal health policies and interventions of governmental and non-governmental institutions. This critical review aims to assess the socioeconomic impact of diseases of working equids in LMICs. By highlighting the implications of diseases on working equid welfare, human wellbeing and livelihoods, this review seeks to sensitise policymakers within governments and international organisations to develop policies and interventions aimed at protecting the health of working equids and, consequently, the health and livelihoods of their dependent communities. Twenty relevant publications were identified through the search of five databases (CAB Abstracts, Web of Science Core Collection, BIOSIS, EMBASE and Scopus), backward citation searching and screening of indexes of proceedings and Special Issues retrieved from the database search. The review findings show that diseases of working equids have detrimental socioeconomic effects. However, this subject is under-researched and restricted to few diseases and geographical settings. Considering the complexity of the issue, this review demonstrates that the 'One Health' approach represents an opportunity to clarify the link between equid health, human wellbeing and livelihoods, facilitating the translation of research into policy.

Temporomandibular joint biomechanics and equine incisor occlusal plane maintenance

In equine dentistry, the physiological incisor occlusal surface is visually perceived as a plane with a distinct inclination to the head's coronal plane, extending rostro-ventrally to caudo-dorsally. To better understand the formation of this inclined plane and its connection to dental wear, we investigated the hypothesis that it arises from masticatory movements and the considerable distance between mandibular articular heads and the incisor occlusal surfaces, acting as the three points of support for the mandibles. Leveraging data from a large-scale clinical study involving static and dynamic orthodontic measurements in horses, we approximated the mandibular movement range where incisor occlusion and dental wear occur. By introducing and testing a segment coordinate system, we explored possible angular deviations from the occlusal plane caused by mandibular roll and pitch rotations during two lateral mandibular movement patterns, protrusion and retrusion. Theoretical biomechanical calculations and simulations confirmed the visual perception of the incisor occlusal surface as a plane. To further examine our assumptions, we employed a simple mechanical simulator to assess incisor normal occlusion and provoked malocclusions (diagonal, smile, and frown bite) by modifying temporomandibular joint (TMJ) movement patterns. The results from clinical investigations were corroborated by both the theoretical analysis and mechanical simulations, strengthening our understanding of the biomechanical basis behind the physiological incisor occlusal plane maintenance in horses. These findings have significant implications for equine dental health and contribute to a thorough understanding of TMJ dynamics.

Intra- and Interexaminer Measurement Variability Analysis of an Orthodontic Gauge Device to Determine Incisor Occlusal Surface Angles in the Horse

Simple Summary

Annual tooth rasping is integral to prophylaxis work in equine dentistry. The procedure begins with a thorough examination of the oral cavity, including assessment of incisor occlusal surface angles. Any dental misalignment should be corrected or reduced to prevent abnormal forces from acting on teeth and supporting tissues and to maximize functionality of the masticatory apparatus. Thus far, clinical methods for dental angle assessment are scarce and not validated in terms of data reproducibility and comparability. These parameters are vital to objectively assess treatment needs and outcome, obtain population data, and establish data comparability among studies. However, this is the first study systematically validating a commercial dental angle measuring device. The data indicate high device performance and its applicability in practice.

Abstract

Incisor malocclusions are common in horses. As yet, an evidence-based understanding of incisor occlusal surface angle dynamics and normocclusal range is missing. Orthodontic measuring devices could help unravel this information objectively but imply measurement validation. We evaluated intra- and interexaminer variability of repeated sagittal and transversal incisor occlusal surface angle measures using a commercial orthodontic gauge device (MaPHorse1). Five examiners (two experienced, three inexperienced) measured six cadaver heads on 2 consecutive days in a blinded block-randomization design, resulting in 16 measures per examiner*head. Sagittal and transversal angle measures revealed low intraexaminer variability at scale-level independent mean SDs of α 0.58° and α 0.69°, respectively. Sagittal angle measures associate with low interexaminer variability, showing small mean angle differences (max. α 0.51° ± 0.35°), small scatter, and more consistent data reproducibility. Despite comparable mean interexaminer differences, the spread of transversal angle measures was relevantly higher using the proposed landmarks (average 2.2-fold higher interquartile range). The measurement performance of experienced and inexperienced examiners did not systematically differ. The time required for individual measurements was already comparable after 24/96 repetitions. This instrument may help deciphering sagittal angle normocclusal range and orthognathic dynamics and, with a proposed procedural amendment, transversal angle as well.

The facultative human oral pathogen Prevotella histicola in equine cheek tooth apical/ periapical infection: a case report

BACKGROUND

Prevotella histicola is a facultative oral pathogen that under certain conditions causes pathologies such as caries and periodontitis in humans. Prevotella spp. also colonize the oral cavity of horses and can cause disease, but P. histicola has not yet been identified.

CASE PRESENTATION

A 12-year-old Tinker mare was referred to the clinic for persistent, malodorous purulent nasal discharge and quidding. Conservative antibiotic (penicillin), antiphlogistic (meloxicam), and mucolytic (dembrexine-hydrochloride) treatment prior to referral was unsuccessful and symptoms worsened. Oral examination, radiography, sino-/ rhinoscopy, and standing computed tomography revealed severe apical/ periapical infection of the upper cheek tooth 209 with accompanying unilateral sinonasal inflammation and conchal necrosis. The tooth exhibited extensive subocclusal mesial infundibular cemental hypoplasia and caries, and an occlusal fissure fracture. After mechanical debridement and thermoplastic resin filling of the spacious subocclusal carious infundibular lesion, the tooth was extracted intraorally. The sinusitis and conchal necrosis were treated transendoscopically. Selective bacteriological swab cultures of affected tooth roots and subsequent matrix-assisted laser desorption ionization-time of flight mass spectrometry showed an infection with the obligate anaerobic, Gram-negative bacterium P. histicola. Surgical intervention and adapted antibiotic therapy led to normal healing without complications.

CONCLUSIONS

This study provides the first documented case of dental infection in a horse caused by P. histicola at once indicating necessity of more sufficient microbiological diagnostics and targeted antibiotic treatment in equine dental practice. This finding is also conducive to understand species-specific Prevotella diversity and cross-species distribution.

Bit type exerts an influence on self-controlled rein tension in unridden horses

Bit configuration and acting rein forces play a crucial role in oral health and comfort of ridden horses. Although it is a big animal welfare issue, dynamic response of horses to different bits has yet not been thoroughly investigated. This convenience sample experimental study describes a model to overcome the almost uncontrollable influence of riders on rein tension and evaluates self-controlled maximum side rein tension of ten sound horses randomly bitted with a double-jointed (DJS) and a version of a Mullen mouth snaffle-bit under unridden conditions. Horses were exercised at walk and trot on a horizontal treadmill wearing custom made force-sensing resistors (FSR) equipped to side reins. FSR were synchronized with a camera-based motion analysis system providing information on amplitudes and temporal occurrence of self-controlled maximum side rein tensile forces during different phases of separated motion cycles. The DJS exhibited larger side rein tension, indicating higher bit contact. Constant temporal occurrence of monophasic maxima at walk and biphasic maxima at trot could be observed in both bits. Within the limitations of this study, application of FSR linked to side reins in unridden horses may provide a promising tool when studying subjective response of horses to different bits.