M. Barba

Experimental Transmission of Corynebacterium pseudotuberculosis Biovar equi in Horses by House Flies

Background The route of Corynebacterium pseudotuberculosis infection in horses remains undetermined, but transmission by insects is suspected. Objectives To investigate house flies (Musca domestica L.) as vectors of C. pseudotuberculosis transmission in horses. Animals Eight healthy, adult ponies. Methods Randomized, controlled, blinded prospective study. Ten wounds were created in the pectoral region where cages for flies were attached. Three ponies were directly inoculated with C. pseudotuberculosis. Four ponies were exposed for 24 hours to 20 hours C. pseudotuberculosis‐inoculated flies. One negative control pony was exposed to noninoculated flies. Ponies were examined daily for swelling, heat, pain, and drainage at the inoculation site. Blood was collected weekly for CBC and biochemical analysis, and twice weekly for synergistic hemolysis inhibition titers. Results Clinical signs of local infection and positive cultures were observed in 7/7 exposed ponies and were absent in the negative control. In exposed ponies, peak serologic titers (1 : 512 to 1 : 2,048) were obtained between days 17 and 21. Seroconversion was not observed in the negative control. Neutrophil counts were higher in the positive and fly‐exposed groups than in the negative control (P = .002 and P = .005) on day 3 postinoculation. Serum amyloid A concentrations were higher in the positive control than in the negative control and fly‐exposed ponies on days 3 (P < .0001) and 7 (P = .0004 and P = .0001). No differences were detected for other biochemical variables. Conclusions and Clinical Importance House flies can serve as mechanical vectors of C. pseudotuberculosis and can transmit the bacterium to ponies.

Management of enterocutaneous fistula associated with an umbilical hernia in a two-year-old horse

Enterocutaneous fistula (ECF) occurs when there is open communication between the lumen of intestine and the skin. This report describes a two-year-old, American Quarter Horse filly presented with an acute ECF involving the ileum entrapped within an umbilical hernia. After four days of conservative therapy and worsening of hydration status and electrolyte and acid-base imbalances, surgical correction of the ECF was performed. The filly was stable 24 hours after surgery and eventually made a full recovery.

Seroprevalence and Risk Factors Associated With Corynebacterium pseudotuberculosis Detectable Antibodies in Equids in Alabama

&NA; A cross‐sectional serological survey was carried out to screen the equine population of the nonendemic state of Alabama for the presence of detectable antibody titers against Corynebacterium pseudotuberculosis. A second objective was to determine the association of detectable titers with risk factors such as exposure to ruminants or previous travel to endemic states. A total of 342 equine serum samples from 40 Alabama counties were analyzed using the synergistic hemolysis inhibition test (SHI). The prevalence of detectable antibody titers (≥1:8) was 52.5% (95% confidence interval [CI], 47%–57.9%). Titers ≥1:128 were detected in 2.63% (95% CI, 1.2%–4.9%), and titers ≥1:512 were detected in 0.3% (95% CI, 0%–1.6%) of the sampled population. In the final generalized linear model, age (P < .001), breed (P = .023), and contact with cattle (P = .05) were associated with increasing SHI titers. Contact with goats was associated in the initial but not in the final analysis (P = .19). Previous travel was not associated with increasing SHI titer (P = .97). The results demonstrated a high prevalence of low detectable titers and low prevalence of titers ≥ 1:128 in a nonendemic population. Further evaluation of SHI cutoff titers and accuracy is warranted to reduce the risk of a false positive diagnosis. HighlightsAlthough never reported in Alabama, 50% of horses had low detectable synergistic hemolysis inhibition (SHI) titers (1:8 to 1:64) and 2.6% of horses had titers ≥1:128.Increasing SHI titers in horses was associated with contact with ruminants.Further evaluation of cross‐reaction with phospholipase D exotoxin from C. p. biovar ovis is warranted.Additional research regarding the serological diagnosis of pigeon fever is needed.