Molecular epidemiology of Theileria species in ticks and its potential threat to livestock in the Republic of Korea

The purpose of this study was to investigate molecular epidemiology of Theileria spp. in ticks in Korea and assess their potential threat from wildlife animals to domestic animals. A total of 21152 hard ticks were collected from Chungcheong and Jeolla provinces of Korea from March to October 2021. Tick species were identified by microscopy and Theileria spp. were screened by nested PCR targeting 18S rRNA. Haemaphysalis spp. were the most abundant tick species, followed by H. longicornis, H. flava, Amblyomma testudinarium, and Ixodes nipponensis. Of the collected ticks, 6914 ticks (541 pools) were screened, and PCR showed 211 positive pools (39.0%; MIR: 3.05). The PCR and phylogenetic analysis identified two Theileria species, T. luwenshuni and Theileria sp., with T. luwenshuni (162/211, 76.78%; MIR: 2.34) being more abundant than Theileria sp. (36/211, 17.06%; MIR: 0.52); co-infection of the two species were noted (13/211, 6.16%; MIR: 0.19). Among the tick species, H. longicornis, especially nymphs, showed the highest prevalence. Regarding season, the highest prevalence was observed in May. Considering the tick and Theileria species identified in this study, H. longicornis nymph and cervine play a critical role in maintaining Theileria spp. in Korea and could be a potential threat to domestic animals, including deer and goats. In addition, there are significant correlations among tick distribution, region, season, and prevalence of Theileria.

Reflected cross-polarized light microscopy as a method for measuring collagen fiber crimp in musculoskeletal tissues

Many musculoskeletal tissues are composed primarily of type I collagen, which takes on a periodic crimp morphology that allows large tensile strains in the tissue. The spatial period of collagen fiber crimp may be used to infer internal strains in a tissue and is typically measured using transmitted cross-polarized light imaging of thin slices. However, slicing may induce specimen distortion and precludes mechanical loading of the specimen during imaging. We hypothesized that reflected cross-polarized light imaging of thick tissue explants would yield crimp period measurements comparable to those obtained from transmitted light imaging of thin slices. We further hypothesized that these measurements would be sensitive to applied uniaxial strain in the fiber direction. These hypotheses were tested by imaging both intervertebral disc outer annulus fibrosus and medial collateral ligament tissue specimens. We found that both transmitted and reflected light yielded similar crimp period measurements for intervertebral disc tissue, with an overall average of 43.5 ± 11.5 μm. Reflected light yielded a significantly higher crimp period with lower variance than transmission through thin specimens (54.1 ± 10.6 μm versus 50.4 ± 16.0 μm) in the ligament. Upon application of axial tension, crimp periods in both fibers increased at a rate of approximately three times the applied strain (with 3.17% applied strain yielding a 9.64 ± 4.4% increase in crimp period in the disc and an 11.7 ± 3.7% increase in the ligament), indicating significant fibril sliding. In support of our hypotheses, these findings suggest that reflected cross-polarized light is a suitable method for measuring collagen fiber crimp in musculoskeletal tissues, both statically and under tension.

White-Tailed Deer as an Ex Vivo Knee Model: Joint Morphometry and ACL Rupture Strength

Animal joints are valuable proxies for those of humans in biomechanical studies, however commonly used quadruped knees differ greatly from human knees in scale and morphometry. To test the suitability of the cervine stifle joint (deer knee) as a laboratory model, gross morphometry, ACL cross section, and ACL rupture strength were measured and compared to values previously reported for the knees of humans and commonly studied animals. Twelve knee joints from wild white-tailed deer were tested. Several morphometry parameters, including bicondylar width (53.5 ± 3.0 mm) and notch width (14.7 ± 2.5 mm), showed a high degree of similarity to those of the human knee, while both medial (16.7 ± 2.1°) and lateral (17.6 ± 4.7°) tibial slopes were steeper than in humans but less steep than other quadrupeds. The median ACL rupture force (2054 N, 95% CI 2017-2256 N), mean stiffness (260 ± 166 N/mm), mean length (33 ± 7 mm), and mean cross sectional area (44.8 ± 18.3 mm²) were also comparable to previously reported values for human knees. In our limited sample size, no significant sexual dimorphism in strength or morphometry was observed (p ≥ 0.05 for all parameters), though female specimens generally had steeper tibial slopes (lateral: p = 0.52, medial: p = 0.07). Our results suggest that the deer knee may be a suitable model for ex vivo studies of ACL rupture and repair.

Ring apophysis fractures induced by low-load low-angle repetitive flexion in an ex-vivo cervine model

Ring apophysis fractures of the spine occur in physically-active adolescents causing low back pain and the potential for chronic pain. Many of these fractures occur without memorable trauma, suggesting that the fractures occur during everyday movements and activities. The benign nature of this poorly understood potential mechanism of injury hampers appropriate diagnosis and early treatment. The purpose of this study was to establish an ex-vivo model of ring apophysis fracture and demonstrate that these fractures can be initiated by repetitive non-traumatic loading. Six 5-vertebra cervine lumbar (L1-L5) motion segments were cyclically loaded in low-angle low-load flexion (to 15° flexion, with peak load of 230±50N), a representative movement component of daily activities for both human and deer lumbar spines. Pinned end conditions replicated physiologically realistic loading. Ring apophysis fractures were created under low-load low-angle conditions in healthy vertebrae of similar bone mineral density and a similar degree of skeletal maturity to adolescent humans. All specimens developed ring apophysis fractures, some as early as 1400 cycles. The load-displacement data, and hysteresis loops during the cyclic loading, suggest that the fractures occurred gradually, i.e., without trauma. The ease at which these fractures were created suggests that ring apophysis fractures may be more prevalent than current diagnosis rates. Therefore, clinically, healthcare providers should include the potential for ring apophysis fracture in the differential diagnosis of all physically-active adolescents who present with back pain.