Objective—To determine the prevalence of antimicrobial resistance to macrolide antimicrobials or rifampin in Rhodococcus equi isolates and to describe treatment outcome in foals infected with antimicrobial-resistant isolates of R equi.
Sample Population—38 isolates classified as resistant to macrolide antimicrobials or rifampin received from 9 veterinary diagnostic laboratories between January 1997 and December 2008.
Procedures—For each isolate, the minimum inhibitory concentration of macrolide antimicrobials (ie, azithromycin, erythromycin, and clarithromycin) and rifampin was determined by use of a concentration-gradient test. Prevalence of R equi isolates from Florida and Texas resistant to macrolide antimicrobials or rifampin was determined. Outcome of antimicrobial treatment in foals infected with antimicrobial-resistant isolates of R equi was determined.
Results—Only 24 of 38 (63.2%) isolates were resistant to > 1 antimicrobial. Two isolates were resistant only to rifampin, whereas 22 isolates were resistant to azithromycin, erythromycin, clarithromycin, and rifampin. The overall prevalence of antimicrobial-resistant isolates in submissions received from Florida and Texas was 3.7% (12/328). The survival proportion of foals infected with resistant R equi isolates (2/8 [25.0%]) was significantly less, compared with the survival proportion in foals that received the same antimicrobial treatment from which antimicrobial-susceptible isolates were cultured (55/79 [69.6%]). Odds of nonsurvival for foals infected with resistant R equi isolates were 6.9 (95% confidence interval, 1.3 to 37) times the odds for foals infected with susceptible isolates.
Conclusions and Clinical Relevance—Interpretation of the results emphasized the importance of microbiological culture and antimicrobial susceptibility testing in foals with pneumonia caused by R equi.
Objective—To determine risk factors for development
of sequestra in cattle and identify factors associated
with a successful outcome.
Procedure—Medical records of cattle treated at veterinary
teaching hospitals in North America were
reviewed. To determine risk factors for osseous
sequestration, breed, age, and sex of cattle with
osseous sequestration were compared with breed,
age, and sex of all other cattle admitted during the
Results—110 cattle were included in the study. Three
had 2 sequestra; thus, 113 lesions were identified.
Most sequestra were associated with the bones of
the extremities, most commonly the third metacarpal
or third metatarsal bone. Ninety-two animals were
treated surgically (ie, sequestrectomy), 7 were treated
medically, 3 were initially treated medically and
were then treated surgically, and 8 were not treated.
Follow-up information was available for 65 animals
treated surgically and 6 animals treated medically.
Fifty-one (78%) animals treated surgically and 5 animals
treated medically had a successful outcome.
Cattle that were 6 months to 2 years old had a significantly
increased risk of developing a sequestrum,
compared with cattle < 6 months old. Cattle in which
sequestrectomy was performed with the aid of local
anesthesia were significantly more likely to undergo 2
or more surgical procedures than were cattle in which
sequestrectomy was performed with the aid of general
Conclusions and Clinical Relevance—Results suggest
that sequestrectomy will result in a successful
outcome for most cattle with osseous sequestration.
(J Am Vet Med Assoc 2000;217:376–383)
Objective—To identify factors associated with abortions
during early gestation classified as mare reproductive
loss syndrome (MRLS).
Animals—324 broodmares from 43 farms in central
Kentucky, including 121 mares from 25 farms that
had early-term abortions (ETAs) associated with
MRLS (case horses), 120 mares from the same farms
but that did not abort, and 83 mares from 18 farms
that were not severely impacted by MRLS.
Procedure—Farm managers were interviewed to
obtain data on various management practices and
environmental exposures for the mares. Data for case
and control horses were compared to identify risk factors
for mares having MRLS-associated ETAs.
Results—Several factors increased the risk of MRLS-associated
ETAs, including feeding hay in pasture,
greater than usual amounts of white clover in pastures,
more eastern tent caterpillars in pastures, abortion
during a previous pregnancy, and sighting deer or
elk on the premises.
Conclusions and Clinical Relevance—Analysis indicates
that certain characteristics of pastures predisposed
mares to MRLS-associated ETAs. Methods for
limiting exposure to pasture (keeping mares in stalls
longer) during environmental conditions similar to
those of 2001 (ie, sudden freezing in mid-April following
warmer-than-usual springtime temperatures and
larger-than-usual numbers of eastern tent caterpillars
in and around pastures) should reduce the risk of
mares having MRLS-associated ETAs. It was not possible
to determine whether exposure to white clover
or caterpillars were causal factors for MRLS or were
merely indicators of unusual environmental conditions
that resulted in exposure of mares to a toxic or infectious
agent. (J Am Vet Med Assoc 2003;222:210–217)
Objective—To identify risk factors for equine protozoal myeloencephalitis (EPM) among horses examined at 11 equine referral hospitals.
Animals—183 horses with EPM, 297 horses with neurologic disease other than EPM (neurologic controls), and 168 horses with non-neurologic diseases (non-neurologic controls) examined at 11 equine referral hospitals in the United States.
Procedures—A study data form was completed for all horses. Data were compared between the case group and each of the control groups by means of bivariate and multivariate polytomous logistic regression.
Results—Relative to neurologic control horses, case horses were more likely to be ≥ 2 years old and to have a history of cats residing on the premises. Relative to non-neurologic control horses, case horses were more likely to be used for racing or Western performance.
Conclusions and Clinical Relevance—Results indicated that cats may play a role in the natural epidemiology of EPM, that the disease is less common among horses < 2 years of age relative to other neurologic diseases, and that horses used for particular types of competition may have an increased risk of developing EPM.
Objective—To compare signalment of horses with cervical vertebral malformation-malarticulation (CVM) with that of control horses and to describe results of clinical examination, diagnostic imaging and necropsy findings, and reported outcome in horses with CVM.
Design—Retrospective case-control study.
Animals—270 horses with CVM and 608 control horses admitted to 6 veterinary hospitals from 1992 through 2007.
Procedures—Medical records of participating hospitals were reviewed to identify horses with CVM (ie, case horses) and contemporaneous control (non-CVM-affected) horses that were admitted for treatment. Signalment was compared between case horses and control horses. Results of clinical examination, laboratory and diagnostic imaging findings, necropsy results, and outcome were assessed for horses with CVM.
Results—Case horses were younger (median age, 2 years) than were control horses (median age, 7 years). Thoroughbreds, warmbloods, and Tennessee Walking Horses were overrepresented in the CVM group. Gait asymmetry and cervical hyperesthesia were frequently detected in horses with CVM. Vertebral canal stenosis and articular process osteophytosis were commonly observed at necropsy; agreement between the results of radiographic or myelographic analysis and detection of lesions at necropsy was 65% to 71% and 67% to 78%, respectively. Of 263 horses with CVM for which outcome was recorded, 1 died and 172 (65.4%) were euthanatized.
Conclusions and Clinical Relevance—Odds of a diagnosis of CVM were greater in young horses and horses of specific breeds. Detection of gait asymmetry and cervical hyperesthesia were frequently reported in association with CVM. Accurate diagnosis of lesions associated with CVM by use of radiography and myelography can be challenging. (J Am Vet Med Assoc 2010;237:812-822)
To examine the susceptibility of cultured primary equine bronchial epithelial cells (EBECs) to a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pseudovirus relative to human bronchial epithelial cells (HBECs).
Primary EBEC cultures established from healthy adult horses and commercially sourced human bronchial epithelial cells (HBECs) were used as a positive control.
Angiotensin-converting enzyme 2 (ACE2) expression by EBECs was demonstrated using immunofluorescence, western immunoblot, and flow cytometry. EBECs were transduced with a lentivirus pseudotyped with the SARS-CoV-2 spike protein that binds to ACE2 and expresses the enhanced green fluorescent protein (eGFP) as a reporter. Cells were transduced with the pseudovirus at a multiplicity of infection of 0.1 for 6 hours, washed, and maintained in media for 96 hours. After 96 hours, eGFP expression in EBECs was assessed by fluorescence microscopy of cell cultures and quantitative PCR.
ACE2 expression in EBECs detected by immunofluorescence, western immunoblotting, and flow cytometry was lower in EBECs than in HBECs. After 96 hours, eGFP expression in EBECs was demonstrated by fluorescence microscopy, and mean ΔCt values from quantitative PCR were significantly (P < .0001) higher in EBECs (8.78) than HBECs (3.24) indicating lower infectivity in EBECs.
Equine respiratory tract cells were susceptible to cell entry with a SARS-CoV-2 pseudovirus. Lower replication efficiency in EBECs suggests that horses are unlikely to be an important zoonotic host of SARS-CoV-2, but viral mutations could render some strains more infective to horses. Serological and virological monitoring of horses in contact with persons shedding SARS-CoV-2 is warranted.
OBJECTIVE To investigate risk factors for the development of pasture- and endocrinopathy-associated laminitis (PEAL) in horses and ponies in North America.
DESIGN Case-control study.
ANIMALS 199 horses with incident cases of PEAL and 351 horses from 2 control populations (healthy horses [n = 198] and horses with lameness not caused by laminitis ) that were evaluated in North America between January 2012 and December 2015 by veterinarian members of the American Association of Equine Practitioners.
PROCEDURES North American members of the American Association of Equine Practitioners were contacted to participate in the study, and participating veterinarians provided historical data on incident cases of PEAL, each matched with a healthy control and a lameness control. Conditional logistic regression analysis was used to compare data on PEAL-affected horses with data on horses from each set of controls.
RESULTS Horses with an obese body condition (ie, body condition score ≥ 7), generalized or regional adiposity (alone or in combination), preexisting endocrinopathy, or recent (within 30 days) glucocorticoid administration had increased odds of developing PEAL, compared with horses that did not have these findings.
CONCLUSIONS AND CLINICAL RELEVANCE The present study identified several risk factors for PEAL that may assist not only in managing and preventing this form of laminitis, but also in guiding future research into its pathogenesis.
VapA expression was evaluated by western immunoblot in cultured equine bronchial cells transfected with 4 mRNA constructs encoding VapA. The mRNA construct with greatest expression was used to immunize foals at ages 2 and 21 days in 5 groups: (1) 300 μg nebulized mRNA (n = 6); (2) 600 μg nebulized mRNA (n = 4); (3) 300 μg mRNA administered intramuscularly (IM) (n = 5); (4) 300 μg VapA IM (positive controls; n = 6); or (5) nebulized water (negative controls; n = 6). Serum, BALF, and PBMCs were collected at ages 3, 22, and 35 days and tested for relative anti-VapA IgG1, IgG4/7, and IgA activities using ELISA and cell-mediated immunity by ELISpot.
As formulated, nebulized mRNA was not immunogenic. However, a significant increase in anti-VapA IgG4/7 activity (P < .05) was noted exclusively in foals immunized IM with VapA mRNA by age 35 days. The proportion of foals with anti-VapA IgG1 activity > 30% of positive control differed significantly (P = .0441) between negative controls (50%; 3/6), IM mRNA foals (100%; 5/5), and IM VapA (100%; 6/6) groups. Natural exposure to virulent R equi was immunogenic in some negative control foals.
Further evaluation of the immunogenicity and efficacy of IM mRNA encoding VapA in foals is warranted.