Apical Elongation of Molar Teeth in Captive Microtus Voles

Abstract

Molar apical elongation (MAE) was the leading cause for euthanasia or death in a captive breeding colony of endangered Amargosa voles ( Microtus californicus scirpensis). Clinical signs included ocular discharge, abnormal mastication, dyspnea, abnormal mentation, weight loss, and death. Although the severity varied, all molars in all quadrants were affected. When severe, the overgrown molar reserve crown and apex protruded into the nasal meatuses, the orbit, the calvarial vault and through the ventral margin of the mandible. Overall prevalence in the colony was 63% (92/146 voles) and increased to 77% in aged voles (>1 year). Mean age of onset was 5.3 months (1.7-11.2 months). Progression to extreme severity occurred over 1 to 3 months. Mean survival was 10.9 months (7.1-21.7 months). Histologically, the lesion was characterized by odontogenic hyperplasia and dysplasia. MAE was also documented in museum specimens of 2 other M. californicus subspecies ( M. californicus californicus, M. californicus vallicola) and 3 other Microtus species ( M. montanus, M. pennsylvanicus, M. socialis). In the M. californicus californicus collection, overall prevalence was 35.1% (129/368 skulls) and increased to 77.3% in aged voles (>1 year). A probable genetic influence was identified in the museum collection of M. californicus californicus. The etiopathogenesis of MAE is likely multifactorial, due to (1) inherent continuous odontogenic proliferation, (2) inadequate occlusal attrition, and (3) possible heritable disease susceptibility. In captivity, dietary or other management of occlusal attrition to prevent or delay MAE is a fundamental concern.

Evaluation of the “Bottleneck” Effect in an Isolated Population of Microtus hartingi (Rodentia, Arvicolinae) from the Eastern Rhodopes (Bulgaria) by Methods of Integrative Analysis

“…It should be mentioned that despite such serious disturbances, voles continue to eat normally and live to adulthood and even to the senex stage (>1 year of age). Tooth growth disorders-molar apical elongation-have been documented in many voles of laboratory colonies: Mynomes ochrogaster [39], Mynomes californicus scirpensis [40], Mynomes pinetorum [41], Lagurus lagurus [42], and Alexandromys montebelli [43]. Nonetheless, the cause of these aberrations was an incorrectly selected diet for keeping laboratory colonies of voles.…”

Common Pitfalls in Analysis of Tissue Scores

“…In recent years, statistical software platforms have become increasingly more user-friendly and as such are common tools used in biomedical publications. 4,23 Several published resources (eg, books or articles) are also available to learn more about tissue scoring, experimental design, and statistical analysis. 2,6,7,9,[11][12][13][14][15][16][17][18][19][20][21]23 Last, but not least, pathologists should secure the professional expertise and collaboration of a statistician as a part of the multidisciplinary team.…”

“…When using ordinal data, nonparametric tests are often recommended. 4,7,23 Table 1 illustrates the results of nonparametric tests on the mock data to demonstrate how easy it is to make errors. Notice that the 4 different tests give 4 very different P-values!…”

Conservation Implications of Shifting Gut Microbiomes in Captive-Reared Endangered Voles Intended for Reintroduction into the Wild

“…A comparison of nutrient content in Teklad 2018 rodent chow and LabDiet 5326 rabbit chow can be found in Supplementary Table S2 . All three voles sampled had developed early stages of molar apical elongation [ 36 ] and required euthanasia, which allowed for opportunistic sampling of foregut contents. Although severe molar apical elongation can inhibit food intake when incisor malocclusion occurs, no malocclusion or weight loss was observed in the individuals sampled.…”