New Strangles Test?

Hello Summarians!

Surgeons performing TPLO have long wondered whether opening the joint contributes to patellar tendon thickening afterward. It turns out, it doesn't. What seems to matter is where you make the osteotomy cut.

This week also brings a more accurate blood test for strangles that sidesteps the false-positive problem caused by a related bacterium.

And a retrospective study finds that injecting steroids into mast cell tumors before surgery shrinks them without increasing wound complications.

Three findings. Each one corrects a common assumption.

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New Strangles Test

This study evaluated a new blood test designed to improve the diagnosis of strangles, a highly contagious respiratory disease in horses caused by Streptococcus equi subsp. equi (SEE). Although PCR and bacterial culture remain the primary diagnostic methods for active infection, serologic testing is valuable for identifying previous exposure, detecting occult infections, and investigating disease outbreaks. The currently available U.S. serologic test targets the SEE M protein (SeM), but its accuracy is limited by cross-reactivity with the related bacterium Streptococcus equi subsp. zooepidemicus (SEZ), which can produce false-positive results. 

To identify a more reliable diagnostic target, researchers screened 89 SEE proteins using a protein microarray. Serum samples from horses with confirmed strangles, healthy control horses, and horses infected with SEZ were analyzed. This screening identified a previously uncharacterized protein, designated P92, as the most promising antigen. The investigators then developed an indirect ELISA using P92 and compared its performance with an ELISA based on SeM in a larger group of horses from multiple U.S. states. 

The P92 ELISA demonstrated significantly greater diagnostic accuracy than the SeM test. It achieved an area under the receiver operating characteristic curve of 95%, compared with 88% for the SeM assay. Using the optimal cutoff value, the P92 test showed 90% sensitivity and 93% specificity, exceeding the SeM ELISA, which achieved 78% sensitivity and 83% specificity. Positive and negative predictive values were also higher for the P92 assay, indicating fewer false-positive and false-negative results. 

The authors acknowledge limitations, including the case-control study design, the relatively small number of SEZ-infected horses, and the need for validation in broader geographic populations and horses with different stages of disease. Nevertheless, the findings indicate that P92 is a highly conserved and effective antigen that could substantially improve serologic diagnosis of strangles. In addition to enhancing ELISA testing, P92 may also serve as a target for future rapid antigen or molecular diagnostic assays used in both laboratory and field settings.

Cohen, N. D., Nakajima, R., Morris, E. R. A., de Assis, R. R., Hughes, E. V., Gonzales, D. M., Baker, R. M., Klein, R. L., Liu, W., Bordin, A. I., & Felgner, P. L. (2026). A new single-antigen serological test accurately detects horses infected with Streptococcus equi subsp equi. Journal of the American Veterinary Medical Association https://doi.org/10.2460/javma.26.02.0149

Bottom line — Seems to be a more accurate marker.

Pre Op Steroid Injection For MCT

This retrospective study evaluated whether neoadjuvant intralesional triamcinolone (NIT) administered within 30 days before surgical removal of canine cutaneous and subcutaneous mast cell tumors (MCTs) increased the risk of postoperative surgical site complications (SSCs). Researchers reviewed the records of 69 dogs with 78 MCTs treated at a tertiary referral hospital between 2018 and 2026. Tumor characteristics, treatment protocols, and postoperative outcomes were analyzed to identify factors associated with wound complications. 

Overall, 25% of tumors developed a postoperative surgical site complication, a rate comparable to previous reports for MCT surgery without NIT. Importantly, 90% of these complications were minor and managed medically, while only two cases required additional surgery. No relationship was found between complication rates and triamcinolone dose, timing of injection before surgery, tumor size, tumor grade, tumor location, use of antibiotics, corticosteroids, antihistamines, NSAIDs, or postoperative bandaging. Surprisingly, tumors receiving two or more intralesional injections experienced no postoperative complications, whereas tumors treated with only one injection had a significantly higher complication rate. Although this finding requires confirmation because of the relatively small number of dogs receiving multiple injections, it suggests repeated treatments do not impair wound healing and may even improve surgical outcomes. 

Among tumors with documented treatment response, 65% decreased in size, with a median reduction of 40%. Tumor shrinkage may improve surgical planning by reducing local inflammation and facilitating complete excision, particularly in anatomically challenging locations. No adverse effects directly attributable to intralesional triamcinolone were observed before surgery. 

The authors conclude that NIT appears to be a safe adjunctive treatment for canine mast cell tumors when used before surgery. It provides meaningful tumor cytoreduction without increasing short-term postoperative wound complications. While the retrospective design and lack of a control group limit definitive conclusions, the findings support further prospective studies to determine optimal dosing schedules, timing before surgery, and effects on long-term tumor control and surgical success. 

Gruber, D. R., Doornink, M. T., & Urie, B. K. (2026). Neoadjuvant intralesional triamcinolone is not associated with increased incidence of surgical site complications in dogs with cutaneous and subcutaneous mast cell tumors. Journal of the American Veterinary Medical Association https://doi.org/10.2460/javma.26.04.0311

Bottom line — Early results support this as a beneficial protocol

TPLO And Osteotomy Site Choice

This retrospective study evaluated whether joint inspection during tibial plateau leveling osteotomy (TPLO) influences postoperative patellar tendon thickness (PTT) in dogs with cranial cruciate ligament disease. Researchers also examined whether the position of the osteotomy affected tendon thickening. Medical records from 145 stifles in 139 dogs treated during 2023 were reviewed. Dogs underwent TPLO either with a mini medial arthrotomy, allowing direct joint inspection, or without an arthrotomy. Radiographs obtained before surgery, immediately after surgery, and at follow-up 4 to 12 weeks later were used to measure PTT. Osteotomies were also classified as either ideally centered or distally centered. 

Dogs that underwent mini medial arthrotomy had significantly greater patellar tendon thickening immediately after surgery than dogs without joint inspection. However, this difference disappeared by the recheck examination, suggesting that arthrotomy contributes only to temporary postoperative tendon swelling rather than persistent thickening. The investigators also found that distally centered osteotomies were associated with significantly greater tendon thickening at follow-up compared with ideally centered osteotomies, although no significant difference was observed immediately after surgery. A higher postoperative tibial plateau angle was another factor associated with increased tendon thickness. 

The findings indicate that while surgical joint inspection may cause transient inflammation of the patellar tendon, it does not appear to influence long-term tendon thickening. Instead, surgical technique, particularly osteotomy positioning and the resulting postoperative tibial plateau angle, may have a greater impact on persistent radiographic changes. The authors suggest that altered biomechanics following TPLO, rather than disruption of tendon blood supply during arthrotomy, likely play a more important role in the development of patellar tendon thickening. Because the study was retrospective and relied on radiographic measurements rather than clinical assessments of pain or lameness, further prospective studies are needed to determine whether these radiographic findings translate into clinically significant patellar tendinosis and to identify surgical methods that may reduce this common postoperative complication.

Toth, D. D., Hamon, M., Márquez, C. B., Pritchard, A., Roush, J. K., Renberg, W. C., & Picavet, P. P. (2026). Distally centered osteotomies, but not joint inspection, are associated with increased radiographic patellar tendon thickness at short-term follow-up after tibial plateau leveling osteotomy in dogs. Journal of the American Veterinary Medical Association https://doi.org/10.2460/javma.26.03.0229 

Bottom line — Distal site choice had more complications.

Just putting things in perspective …