Contact Mechanics of Simulated Meniscal Tears in Cadaveric Canine Stifles

Objective— To evaluate the biomechanical effects of 5 types of meniscal lesions on contact mechanics in the canine stifle.
Study Design— Experimental study.
Animals— Cadaveric canine stifles (n=12 pair).
Methods— Medial meniscal lesions (radial, vertical longitudinal, nonreducible bucket handle, flap, and complex tears) were simulated in cadaveric stifles. A contact map was recorded from each tear type and contact area (CA) and peak contact pressure (PCP) from each tear type were compared.
Results— A significant difference in PCP was detected between control and nonreducible bucket handle, flap, and complex tears. PCP increased by >45% in nonreducible bucket handle, flap, and complex meniscal tears when compared with control. No significant difference was found in PCP between control and radial and vertical longitudinal tears. No significant difference was found in CA between any of the meniscal conditions.
Conclusions— Nonreducible bucket handle, flap, and complex tears cause a significant increase in PCP. Radial and vertical longitudinal tears had a minimal impact on the contact pressures of the medial compartment of the stifle.
Clinical Relevance— Based on this ex vivo model, we support the clinical recommendation of debriding nonreducible bucket handle, flap, and complex tears because the injured portion of the meniscus no longer contributes significantly to the function of the meniscus. Radial and vertical longitudinal tears do not cause a change in contact mechanics allowing consideration of nonsurgical treatment and meniscal repair, respectively. Future experimental and clinical studies should aim to refine the treatment of specific meniscal injuries.     

Potential Iatrogenic Medial Meniscal Damage During Tibial Plateau Leveling Osteotomy

Objective— To evaluate potential iatrogenic medial meniscal (MM) damage during tibial plateau leveling osteotomy (TPLO) and to establish a safe zone (SZ) for hypodermic needle (HN) identification of the medial aspect of the stifle joint.
Study Design— Prospective cohort.
Animals— Cadaveric canine stifles (n=40).
Methods— HN (20 or 25 G) were inserted through the medial collateral ligament (MCL) of the femorotibial joint and through the SZ insertion points. The medial meniscus was inspected for iatrogenic damage. Statistical comparison of MM damage caused by different needle sizes and insertion sites was performed using Fisher's exact test with significance at P <.05.
Results— Twenty-gauge group: 65% of stifles had minor MM damage with MCL insertion compared with 35% of stifles with SZ insertion ( P =.0049). Severe MM damage occurred in 25% of stifles with MCL insertion compared with 0% of stifles with SZ insertion ( P =.0014). Twenty-five-gauge group: 85% of stifles had minor MM damage with MCL insertion compared with 30% after SZ insertion ( P =.0011); however, no severe MM injury was noted.
Conclusions— HN insertion though the MCL can produce iatrogenic damage to the MM. Use of a 25 G HN and SZ site for insertion reduced the frequency and severity of MM damage.
Clinical Relevance— HN insertion into the medial aspect of the femorotibial joint during TPLO can cause gross iatrogenic MM damage, which may contribute to the incidence and misdiagnosis of latent MM injuries after TPLO.     

Application of Platelet-Rich Gel to Enhance Wound Healing in the Horse: A Case Report

A large torn wound of the dorsal elbow region was observed in a 17-year-old Arabian mare. Surgical reconstruction was performed with the horse in standing sedation, but suture dehiscence occurred 2 days later. Autologous platelet-rich gel (PRG) was then applied to the wound every 3 weeks for a total of 3 administrations to accelerate good-quality healing. The wound had healed rapidly and completely within 5 months of the first PRG treatment, without chronic effects or formation of exuberant tissue granulation and with minimum scarring. This case report suggests that topical treatment with autologous PRG, as additional therapy, might be considered beneficial in the management of large-wound healing in horses, and it can be regarded as safe and inexpensive treatment that can be used in field.     

Se18.9, an anti-phagocytic factor H binding protein of Streptococcus equi

Evasion of phagocytosis is an important virulence determinant of Streptococcus equi (S. equi subsp. equi), the cause of equine strangles and distinguishes it from the closely related but much less virulent S. zooepidemicus (S. equi subsp. zooepidemicus). We describe Se18.9, a novel H factor binding protein secreted by S. equi but not by S. zooepidemicus that reduces deposition of C3 on the bacterial surface and significantly reduces the bactericidal activity of equine neutrophils suspended in normal serum for both S. equi and S. zooepidemicus. Se18.9 is secreted abundantly by actively dividing cells and is also bound to the bacterial surface. Strong serum and mucosal antibody responses are elicited in S. equi infected horses. Although a gene identical to se18.9 was not detected in S. zooepidemicus, sequences encoding proteins of similar size with similar signal peptide sequences were found in 3 of 12 randomly selected strains. Since Se18.9 is unique to S. equi, and immunoreactive with convalescent sera and mucosal IgA, it has potential for immunodiagnosis and for study of mucosal antibody response to S. equi.     

Toxic shock syndrome in a horse with Staphylococcus aureus pneumonia

A 3-year-old Thoroughbred gelding was examined because of clinical signs of pneumonia and shock. Mucous membrane petechiation and ventral edema were observed and considered to be a result of vasculitis. Epidermal necrosis developed on the distal portions of the limbs. The horse had a persistent high fever that was unresponsive to nonsteroidal anti-inflammatory treatment, and Staphylococcus aureus was isolated from a nasal swab specimen and 2 transtracheal wash fluid samples. Antimicrobial, anti-inflammatory, and supportive treatment resulted in clinical improvement. However, resolution of the pulmonary infection required long-term (42 days) antimicrobial administration. Staphylococcus aureus strains isolated from this horse were positive for the toxic shock syndrome toxin-1 gene and were shown to produce toxic shock syndrome toxin-1, the causative factor in toxic shock syndrome in humans. The horse's clinical signs were attributed to toxic shock syndrome secondary to pulmonary S. aureus infection.     

Minimum alveolar concentration of sevoflurane in spontaneously breathing llamas and alpacas

OBJECTIVE: To determine the minimum alveolar concentration (MAC) of sevoflurane in spontaneously breathing llamas and alpacas. DESIGN: Prospective study. ANIMALS: 6 healthy adult llamas and 6 healthy adult alpacas. PROCEDURE: Anesthesia was induced with sevoflurane delivered with oxygen through a mask. An endotracheal tube was inserted, and a port for continuous measurement of end-tidal and inspired sevoflurane concentrations was placed between the endotracheal tube and the breathing circuit. After equilibration at an end-tidal-to-inspired sevoflurane concentration ratio > 0.90 for 15 minutes, a 50-Hz, 80-mA electrical stimulus was applied to the antebrachium until a response was obtained (ie, gross purposeful movement) or for up to 1 minute. The vaporizer setting was increased or decreased to effect a 10 to 20% change in end-tidal sevoflurane concentration, and equilibration and stimulus were repeated. The MAC was defined as the mean of the lowest end-tidal sevoflurane concentration that prevented a positive response and the highest concentration that allowed a positive response. RESULTS: Mean +/- SD MAC of sevoflurane was 2.29 +/- 0.14% in llamas and 2.33 +/- 0.09% in alpacas. CONCLUSIONS AND CLINICAL RELEVANCE: The MAC of sevoflurane in llamas and alpacas was similar to that reported for other species.     

Pilot project to investigate over-wintering of free-living gastrointestinal nematode larvae of sheep in Ontario,Canada

This study investigated the overwintering survival and infectivity of free-living gastrointestinal nematode (GIN) stages on pasture. The presence of GIN larvae was assessed on 3 sheep farms in Ontario with a reported history of clinical haemonchosis, by collecting monthly pasture samples over the winter months of 2009/2010. The infectivity of GIN larvae on spring pastures was evaluated using 16 tracer lambs. Air and soil temperature and moisture were recorded hourly. Free-living stages of Trichostrongylus spp. and Nematodirus spp. were isolated from herbage samples. Gastrointestinal nematodes were recovered from all tracer lambs on all farms; Teladorsagia sp. was the predominant species. Very low levels of Haemonchus contortus were recovered from 1 animal on 1 farm. The results suggest that Haemonchus larvae do not survive well on pasture, while Teladorsagia sp., Trichostrongylus spp. and Nematodirus spp. are able to overwinter on pasture in Ontario and are still infective for sheep in the spring.     

Mutation and virulence assessment of chromosomal genes of Rhodococcus equi 103

Rhodococcus equi can cause severe or fatal pneumonia in foals as well as in immunocompromised animals and humans. Its ability to persist in macrophages is fundamental to how it causes disease, but the basis of this is poorly understood. To examine further the general application of a recently developed system of targeted gene mutation and to assess the importance of different genes in resistance to innate immune defenses, we disrupted the genes encoding high-temperature requirement A (htrA), nitrate reductase (narG), peptidase D (pepD), phosphoribosylaminoimidazole-succinocarboxamide synthase (purC), and superoxide dismutase (sodC) in strain 103 of R. equi using a double-crossover homologous recombination approach. Virulence testing by clearance after intravenous injection in mice showed that the htrA and narG mutants were fully attenuated, the purC and sodC mutants were unchanged, and the pepD mutant was slightly attenuated. Complementation with the pREM shuttle plasmid restored the virulence of the htrA and pepD mutants but not that of the narG mutant. A single-crossover mutation approach was simpler and faster than the double-crossover homologous recombination technique and was used to obtain mutations in 6 other genes potentially involved in virulence (clpB, fadD8, fbpB, glnA1, regX3, and sigF). These mutants were not attenuated in the mouse clearance assay. We were not able to obtain mutants for genesfurA, galE, and sigE using the single-crossover mutation approach. In summary, the targeted-mutation system had general applicability but was not always completely successful, perhaps because some genes are essential under the growth conditions used or because the success of mutation depends on the target genes.