Objective—To describe the clinical course and outcome in horses in which Corynebacterium pseudotuberculosis infections were associated with musculoskeletal disease and lameness.
Design—Retrospective case series.
Procedures—Clinical and clinicopathologic data were collected from horses diagnosed with lameness associated with C pseudotuberculosis infection between 1999 and 2009.
Results—32 (91.4%) horses had grade 4/5 lameness. Three (8.6%) horses had grade 5/5 lameness. Abscesses were diagnosed by clinical or ultrasonographic examination. Abscesses were located in the axillary or triceps region in 25 (71.4%) horses, the stifle region in 2 (5.7%), and the popliteal lymph node in 1 (2.9%). Diffuse lymphangitis was seen in 4 (11.4%) horses, osteomyelitis in 2 (5.7%) horses, and septic arthritis in 2 (5.7%) horses. Horses commonly had clinicopathologic abnormalities characterized by neutrophilia (96.4%), anemia (67.8%), hypoalbuminemia (66.6%), or hyperfibrinogenemia (42.8%). Treatment included surgical drainage of the abscess in 21 (60%) horses, performed under ultrasonography in 20 horses; anti-inflammatory medications in 34 (97.1 %) horses; and antimicrobials in 30 (85.7%) horses.
Conclusions and Clinical Relevance—C pseudotuberculosis infection of the limbs in horses typically results in severe lameness but may have a favorable prognosis. The diagnosis may be challenging, and results of blood work consistent with inflammation are nonspecific, but anemia, hyperglobulinemia, and increased synergistic hemolysis inhibition titers are common. Ultrasonography may localize the lesions and facilitate surgical drainage to alleviate lameness. When C pseudotuberculosis musculoskeletal infection results in osteomyelitis or septic arthritis, the prognosis for survival is poor.
Objective—To determine the incidence of complications and identify risk factors associated with development of complications following routine castration of equids.
Design—Retrospective case series.
Animals—311 horses, 10 mules, and 3 donkeys.
Procedures—Medical records of equids undergoing routine castration were reviewed. Age, breed, surgical techniques (closed vs semiclosed castration and use of ligatures), anesthesia method (general IV anesthesia vs standing sedation with local anesthesia) and repeated administration of IV anesthetic agents, administration of antimicrobials and anti-inflammatory drugs, and details regarding development, management, and outcome of complications were recorded. Odds ratios and 95% confidence intervals were determined. Associations between additional doses of anesthetic agents during surgery and development of complications were analyzed with a Jonckheere-Terpstra test.
Results—33 of 324 (10.2%) equids developed a complication after surgery; 32 recovered and 1 was euthanized because of eventration. Equids that underwent semiclosed castration had significantly higher odds of developing a complication (OR, 4.69; 95% confidence interval, 2.09 to 10.6) than did those that underwent closed castration. Equids that received additional doses of anesthetic agents to maintain adequate general anesthesia developed complications more frequently than those that did not require this treatment.
Conclusions and Clinical Relevance—Incidence of complications was low, and most evaluated variables were not significantly associated with development of complications following castration in equids. However, findings suggested that the choice of surgical technique (closed vs semiclosed) is an important factor in this regard. Future studies should investigate whether duration of surgery is associated with complications following castration in equids.
Objective—To determine the outcome of penetrating injuries to the central region of the foot in equids and identify factors that may affect treatment and outcome.
Design—Retrospective case series.
Animals—63 equids (61 horses, 1 pony, and 1 mule).
Procedures—Records of equids incurring puncture wounds through the frog (cuneus ungulae) or collateral sulci of the foot between 1998 and 2008 were reviewed. Evaluated factors that were hypothesized to affect outcome included signalment, degree of lameness, foot affected, duration between injury and admission, and treatment. Injuries were graded from 1 (< 1 inch; involving superficial corium only) to 4 (involving a synovial structure) on the basis of severity of penetration as determined by radiographic evidence or findings on synoviocentesis at the time of admission.
Results—Overall, 60% (38/63) of equids returned to soundness. Thirteen equids were euthanized on the basis of synovial structure involvement and financial constraints. Of 35 equids that were treated conservatively, which may have included undergoing a surgical procedure with the horse standing, 32 (91.4%) returned to their previous level of soundness. Fifteen equids underwent surgical treatment under general anesthesia, of which 6 (40%) became sound for intended use. Ten of 34 (29%) equids with synovial structure involvement regained soundness. Equids treated earlier after injury had a better prognosis. Equids with a hind foot injury had a more favorable outcome than those with a forefoot injury.
Conclusions and Clinical Relevance—Results suggested that penetrating injuries located centrally in the foot of equids without involvement of a synovial structure have a favorable prognosis, especially if managed early. Penetration of a synovial structure provided a poor prognosis.
Objective—To use an extracorporeal circuit to evaluate
effects of intraluminal distention on the jejunum
of healthy horses.
Sample Population—2 jejunal segments from each
of 5 horses.
Procedure—Jejunal segments were harvested and
maintained in an extracorporeal circuit. One segment
was subjected to distention (intraluminal pressure,
25 cm H2O) followed by decompression, and 1 segment
was maintained without distention. The influence
of distention-decompression on vascular resistance
was calculated. Mucosal permeability was
evaluated by measuring the clearance of albumin
from blood to lumen. After distention and decompression,
tissue specimens were collected for histomorphologic
evaluation. In addition, the contractile
response of the circular smooth muscle layer was
determined following incubation with 3 prokinetic
Results—Intestinal vascular resistance increased during
intraluminal distention and returned to baseline
values after decompression. Albumin clearance rate
increased after distention, compared with baseline
and control values. Histologic examination of the distended
segments revealed grade-1 and -2 lesions of
the mucosal villus. Edema and hemorrhage were evident
in the submucosa and muscular layers.
Mesothelial cell loss, edema, and hemorrhage were
also evident in the serosa. Mucosal surface area and
villus tip height decreased and submucosal volume
increased in the distended tissue. Compared with
responses in control specimens, distention
decreased the contractile response induced by cisapride,
erythromycin, and metoclopramide.
Conclusions and Clinical Relevance—Intraluminal
distention of the jejunum followed by decompression
increased mucosal permeability and injury and
decreased responses to prokinetic agents. Horses
with intraluminal intestinal distention may have a
decreased response to prokinetic agents. (Am J Vet Res 2002;63:267–275)
Objective—To characterize isolates of Corynebacterium
pseudotuberculosis from horses, cattle, and sheep in
Colorado, Kentucky, Utah, and California in samples collected
during perceived epidemics of infection
(increased numbers of cases identified) in 2002 and
2003, and determine how closely isolates were related
and their possible source.
Sample Population—54 isolates of C pseudotuberculosis
from 49 horses, 4 cattle, and 1 sheep.
Procedures—Random amplified polymorphic DNA
(RAPD) polymerase chain reaction (PCR) assay, PCR
assay for the gene encoding the phospholipase D
(PLD) toxin, biochemical analyses, and tests for susceptibility
to 17 antimicrobial drugs were performed.
Results—All isolates reduced nitrate to nitrite, most
yielded positive results for the PLD toxin gene, and all
were susceptible to antimicrobial drugs. Ten genetic
types were detected by use of RAPD PCR assay;
types III to X were isolated from horses, cattle, or
both in 1 or more states. Types III and IX were isolated
from both horses and cattle. Types VII and VIII were
isolated in only 1 state, but the number of isolates in
these groups was small. In contrast, all other types
were isolated in 2 or more states. All isolates from
Utah were type III, but the other 3 states had isolates
from more than 1 type.
Conclusions and Clinical Relevance—These data
are consistent with a clonally expanding epidemic of
infection in Utah and an increase in number of infections
caused by multiple strains of C pseudotuberculosis
not derived from a single source in the other
states. The increase in number of infections could be
the result of reporting bias, environmental factors facilitating
infection, or host factors such as greater herd
susceptibility. (Am J Vet Res 2004;65:1734–1737)
Objective—To evaluate the efficacy of a customized
solution to attenuate intestinal injury following 20%
low-flow ischemia and reperfusion in the jejunum of
Animals—10 healthy adult horses.
Procedure—Two 30.5-cm-long segments of jejunum
were exteriorized through a ventral midline incision
and the mesenteric artery and vein supplying that portion
of the intestine were instrumented with flow
probes. Blood flow was decreased to 20% of baseline
for 90 minutes followed by 90 minutes of reperfusion.
In 5 horses, 60 mL of the customized solution
was placed in the lumen of each segment (treatment-group
horses), and 60 mL of lactated Ringer's solution
was placed in the lumen of 5 additional horses
(control-group horses). Biopsy specimens were
obtained from 1 segment in both groups for histologic
evaluation. Aliquots of luminal fluid were obtained
from the other segment in both groups for determination
of albumin concentrations as an index of
Results—Compared with control-group horses, treatment-group horses had a significant decrease in luminal
albumin concentration following reperfusion.
Although differences in mucosal grades were not significantly
different between control- and treatment-group
horses, treatment-group horses had significantly
greater jejunal villous length and area, compared
with that of control-group horses.
Conclusions and Clinical Relevance—Intraluminal
administration of the customized solution in the
jejunum, compared with lactated Ringer's solution,
results in an improvement in histologic findings and
mucosal translocation of albumin in horses with mild
intestinal injury. (Am J Vet Res 2004;65:485–490)
Objective—To quantify the number of horses with Corynebacterium pseudotuberculosis infection identified in the United States from January 2003 through December 2012.
Sample—State veterinary diagnostic laboratory records of 2,237 C pseudotuberculosis culture-positive samples from horses.
Procedures—44 state veterinary diagnostic laboratories throughout the United States were invited by mail to participate in the study. Data requested included the number of C pseudotuberculosis culture-positive samples from horses identified per year, geographic location from which the C pseudotuberculosis culture-positive sample was submitted, month and year of sample submission, breed and age of horses, and category of clinical manifestation (ie, internal infection, external infection, or ulcerative lymphangitis).
Results—Of the 44 invited laboratories, 15 agreed to participate and provided data on affected horses from 23 states. The proportion of C pseudotuberculosis culture-positive samples submitted during 2011 through 2012 (1,213/2,237 [54%]) was significantly greater than that for the period from 2003 through 2010 (1,024/2,237 [46%]). Corynebacterium pseudotuberculosis was recovered from horses in states where the disease has not been previously recognized as endemic. Affected horses were identified year-round. The greatest proportion of C pseudotuberculosis culture-positive samples was identified during November, December, and January (789/2,237 [35%]). No significant association between the clinical form of disease and age or breed of horse was observed.
Conclusions and Clinical Relevance—The occurrence of C pseudotuberculosis infection in horses increased during the 10-year period, and affected horses were identified throughout the United States. Further studies to determine changes in annual incidence and to identify potential changing climatic conditions or vector populations associated with disease transmission are warranted to help control the occurrence and spread of C pseudotuberculosis infection in horses.
Objective—To evaluate clinical, microbiologic, and pathologic outcomes in mice after inoculation with 4 equine-origin Corynebacterium pseudotuberculosis strains.
Animals—15 C3H/HeJ mice.
Procedures—In a preliminary study, the optimum route of inoculation was determined. In the main study, mice were allocated to 4 treatment groups (3 mice/group). One slow- or rapid-growing equine-origin C pseudotuberculosis strain was inoculated ID into the mice of each treatment group.
Results—All 4 strains had distinct tropism for the liver. Histologic lesions associated with rapid-growing strains included focally extensive unencapsulated areas of acute, massive coagulative necrosis of hepatocytes with intralesional colonies of bacteria and variable portal hepatitis characterized by accumulations of mononuclear and polymorphonuclear inflammatory cells. In contrast, the livers of mice inoculated with slow-growing strains had multiple discrete, randomly distributed foci of hepatocellular necrosis and neutrophilic hepatitis that were considerably less severe than the lesions in the mice inoculated with the rapid-growing strains. Significantly more bacterial colonies were recovered from the organs of mice inoculated with rapid-growing than with slow-growing strains of bacteria. Bacteria were isolated from the liver, spleen, lungs, and mesenteric lymph nodes of mice inoculated with rapid-growing strains and from the liver and lymph nodes of mice inoculated with slow-growing strains.
Conclusions and Clinical Relevance—Study of host-bacteria interactions in hosts that are naturally infected with C pseudotuberculosis is difficult because of underlying genetic variability among animals, expense, and requirements for multiple replicates and control animals. The C3H/HeJ mice may provide a useful means for studying virulence mechanisms of C pseudotuberculosis.
Objective—To estimate likelihood ratios (LRs) of correctly identifying internal Corynebacterium pseudotuberculosis infection in horses by measurement of antibody titers via serum synergistic hemolysis inhibition (SHI) testing.
Design—Retrospective case-control study.
Animals—170 horses (171 records; 92 cases of C pseudotuberculosis infection and 79 controls).
Procedures—Medical records were reviewed, and horses were grouped on the basis of evidence of internal or external C pseudotuberculosis infection. The LRs and 95% confidence intervals for identification of internal C pseudotuberculosis infection by use of SHI test results were estimated.
Results—LRs for C pseudotuberculosis infection increased as antibody titers increased when all horses were included in analyses; LRs for detecting internal infection were significantly > 1 (null value) for reciprocal antibody titers ≥ 1,280 overall and > 160 when horses with external abscesses were excluded. Likelihood ratios for detecting internal infection did not differ from 1 (indicating no change in pretest-to-posttest odds of internal infection) when only horses with external C pseudotuberculosis infection (horses with external and internal abscesses vs those with external abscesses only) were included. The LR for detecting internal infection was 2.98 (95% confidence interval, 2.19 to 4.05) for horses with titers ≥ 512.
Conclusions and Clinical Relevance—In the study population, higher titers were typically more indicative of active external or internal C pseudotuberculosis infection than of internal disease specifically. The SHI test was not a useful predictor of internal C pseudotuberculosis infection in horses with external abscesses but was useful in the absence of external disease.