Antimicrobial susceptibility of Salmonella and Escherichia coli from equids sampled in the NAHMS 2015-16 equine study and association of management factors with resistance

Several studies have investigated antimicrobial resistance (AMR) in Salmonella spp. and Escherichia coli isolated from hospitalized horses, but studies conducted on community-based populations of equids are limited. The factors associated with AMR in these bacteria in the general horse population are not well understood. The primary objective of our study was to estimate the prevalence of Salmonella and describe antimicrobial susceptibility of Salmonella and E. coli from equids across the United States. The second objective was to identify associations between health management and biosecurity practices and AMR. Fecal samples submitted from 1357 equids on 199 operations were tested for Salmonella, identifying 27 positive samples with 29 isolates belonging to 18 serotypes. Fecal sample and operation-level prevalence of Salmonella was 2.0% (27/1357) and 7.0% (14/199), respectively. Most (25/29) isolates were pan-susceptible while four isolates exhibited resistance, three of which were multidrug resistant. Of the 721 samples cultured for E. coli, 85% (613/721) were positive. Eighty-six percent of the E. coli isolates recovered were pan-susceptible (529/612). Ten isolates were intermediate to one antimicrobial drug and susceptible to all others. Seventy-three E. coli isolates (11.9%, SE=1.3) were resistant to one or more antimicrobials, corresponding to a 33.0% (64/194) operation-level prevalence. Resistance to sulfonamide drugs was most common with 63 isolates (10.3%) resistant to sulfisoxazole, 57 of which (9.3%) were resistant to trimethoprim-sulfamethoxazole. MDR in E. coli was rare (1.8%, SE=0.5). Univariate and multivariable regression were used to evaluate associations between health management and biosecurity questionnaire items and AMR in E. coli. The outcome modeled was resistance to any of the 14 tested antimicrobials. Depending on the operation type, operations with greater than 20 resident equids were significantly associated with resistance. In addition, performance operations were significantly associated with resistance when compared to farm/ranch operations. Operations with feed containers that prevent fecal contamination and those that had treated any equids for illness or injury were associated with a lower AMR. The study results suggest that equids in the general population appear to pose low risk of shedding antimicrobial resistant strains of Salmonella and E. coli, and therefore low transmission potential to other equids, animals, humans, or the environment. However, it is prudent to practice good hand hygiene to prevent spread of Salmonella as well as AMR, and to protect both animal and human health. Despite study limitations, potential management factors that may influence prevalence and prevent spread of AMR shed by equids were identified.

Anthelmintic efficacy against equine strongyles in the United States

Equine strongyle parasites are ubiquitous in grazing equids across the world. Anthelmintic resistance is widely developed in cyathostomin populations, but very few surveys have evaluated anthelmintic efficacy in equine populations in the United States, and most of these are over 15 years old. The present study was carried out as part of the National Animal Health Monitoring Systems (NAHMS) Equine 2015-2016 study. The aims were to investigate anthelmintic treatment efficacy by means of the fecal egg count reduction test (FECRT) and identify parameters associated with decreased efficacy. Data were collected from equine operations in 28 states via questionnaires and fecal samples submitted for fecal egg count analysis. Participants were instructed to collect samples from six equids at the day of anthelmintic treatments and 14 days later, and they were asked to include an empty syringe with a legible label of the anthelmintic product used in the shipment. Overall, dewormer treatment was effective for 76.3% of operations (84.6% of animals). Macrocyclic lactone use was effective for 88.7% of operations (95.0% of animals) while pyrimidine/benzimidazole use was effective for 21.4% of operations (43.5% of animals). Univariate analysis revealed that overall, macrocyclic lactones exhibited significantly higher efficacy than the pyrimidine and benzimidazole drug classes (p < 0.0001). There were no statistically significant differences observed between geographic regions (West, South Central, North East, and Southeast). Body weight (p = 0.0355), amount of anthelmintic administered (p = 0.0119), and operation size (p = 0.0162) were statistically associated with anthelmintic efficacy, while anthelmintic treatment frequency in the previous 12 months was not (p = 0.7081). Multiple, mixed-effect logistic regression revealed that anthelmintic drug class (p < 0.0001) was the most impactful factor in predicting anthelmintic efficacy, after accounting for operation size, region and clustering of equids at the operation level. Pasture rotation (p = 0.0129) also demonstrated a significant effect using this model. These data document widespread occurrence of reduced anthelmintic efficacy of benzimidazole and pyrimidine products against strongyle infections in equids in the United States. Anthelmintic efficacy patterns were relatively uniform between the four studied regions, and some epidemiological factors were identified to be associated with anthelmintic efficacy against strongyle infections. This information can be useful in devising sustainable parasite control strategies in the future.

Parasite control strategies used by equine owners in the United States: A national survey

The widespread occurrence of anthelmintic resistance in equine parasites across the world has led to recommendations of fecal egg count-based parasite programs to reduce treatment intensity and thereby delay further development of resistance as much as possible. The most recent study describing equine parasite control in the United States was conducted 20 years ago, and little is known about current strategies employed. This study was part of the National Animal Health Monitoring Systems (NAHMS) Equine 2015 Study, and aimed to describe equine parasite control strategies in the U.S. and evaluate to which extent respondents were in compliance with current guidelines. The study was carried out in 28 states, representing 70.9% of all equine operations with at least five equids present. Two questionnaires were administered, either by mail or delivered in person by veterinary medical officers. Participants provided specific details of their operation and were asked questions about strategies for anthelmintic therapy and diagnostic testing. A total of 380 operations provided data regarding their parasite control practices. Most respondents dewormed 2-3 times a year with ivermectin being the most commonly used anthelmintic. About 22% of respondents used fecal egg counts (FEC) in some form, with less than 10% using them on a regular basis. Less than 5% made use of fecal egg count reduction tests (FECRT). These results suggest little change since the last nationwide survey was conducted in 1998, as the majority of respondents did not report using FECs. This is in stark contrast to recent European surveys, where 50-60% of respondents were using FECs routinely. However, the anthelmintic treatment intensity appears to have been lowered compared to 1998. Taken together, these results suggest a continuing need for education and outreach regarding sustainable parasite control.

Babesia equi-induced anemia in a Quarter Horse and subsequent regulatory response

CASE DESCRIPTION

A 7-year-old Quarter Horse gelding used for unsanctioned racing was examined because of fever and anorexia.

CLINICAL FINDINGS

Physical examination revealed fever, tachycardia, and tachypnea. Results of a CBC indicated anemia and mild thrombocytopenia. Results of microscopic examination of a blood smear indicated piroplasms in erythrocytes, consistent with Babesia spp. Regulatory authorities were contacted, and results of serologic testing at the National Veterinary Services Laboratories confirmed acute Babesia equi infection.

TREATMENT AND OUTCOME

Equids on the home premises of the index horse were placed under quarantine. Those equids were tested for piroplasmosis, and 6 of 63 horses had positive results for B equi. Another horse that had previously been housed on the index premises also had positive results for B equi. Competent tick vectors for piroplasmosis organisms were not identified. All 8 horses with piroplasmosis were Quarter Horses that participated in unsanctioned racing and were trained by the same person. Two of the horses were illegally removed from the index premises; these 2 horses and the other horse with piroplasmosis that was previously housed on the index premises could not be found. The other 5 horses with piroplasmosis were euthanized. Investigators concluded that transmission of B equi among horses was most likely iatrogenic.

CLINICAL RELEVANCE

The United States has been considered piroplasmosis free. However, veterinarians should consider piroplasmosis in horses with signalments and clinical signs similar to those of the index horse of this report. Regulatory authorities should be contacted regarding horses in which piroplasmosis is suspected.

Knowledge base and effectiveness of online continuing education about foreign animal diseases for equine veterinarians

The purpose of this study was to assess the effectiveness of two different methods of online education using the knowledge base of African horse sickness (AHS) among US equine veterinarians as a model. An e-mail was sent to US veterinary members of the American Association of Equine Practitioners (AAEP), inviting them to participate in a complementary online educational opportunity. We determined participants' baseline knowledge of AHS by their responses in an AHS case scenario. Participants were then randomly assigned to either a Webinar module or a text-formatted module, followed by an educational assessment quiz. Educational effectiveness was measured by considering the difference between the educational assessment quiz score and the baseline knowledge score. Of the 5,394 members from the AAEP list, 309 veterinarians agreed to participate, but only 211 completed the entire study. The median baseline knowledge score from the case scenario was 20 out of a perfect score of 100 points. The median assessment quiz score after the participants had access to the AHS educational material was 90, which was significantly higher than the baseline knowledge score (p=.01). Educational effectiveness in the module formats showed no significant difference (p=.81). Results from this study suggest that online education modules, once accessed, may improve participants' knowledge of veterinary diseases.

Re-emergence of the apicomplexan Theileria equi in the United States: elimination of persistent infection and transmission risk

Arthropod-borne apicomplexan pathogens that cause asymptomatic persistent infections present a significant challenge due to their life-long transmission potential. Although anti-microbials have been used to ameliorate acute disease in animals and humans, chemotherapeutic efficacy for apicomplexan pathogen elimination from a persistently infected host and removal of transmission risk is largely unconfirmed. The recent re-emergence of the apicomplexan Theileria equi in U.S. horses prompted testing whether imidocarb dipropionate was able to eliminate T. equi from naturally infected horses and remove transmission risk. Following imidocarb treatment, levels of T. equi declined from a mean of 10^4.9 organisms/ml of blood to undetectable by nested PCR in 24 of 25 naturally infected horses. Further, blood transfer from treated horses that became nested PCR negative failed to transmit to naïve splenectomized horses. Although these results were consistent with elimination of infection in 24 of 25 horses, T. equi-specific antibodies persisted in the majority of imidocarb treated horses. Imidocarb treatment was unsuccessful in one horse which remained infected as measured by nested PCR and retained the ability to infect a naïve recipient via intravenous blood transfer. However, a second round of treatment eliminated T. equi infection. These results support the utility of imidocarb chemotherapy for assistance in the control and eradication of this tick-borne pathogen. Successful imidocarb dipropionate treatment of persistently infected horses provides a tool to aid the global equine industry by removing transmission risk associated with infection and facilitating international movement of equids between endemic and non-endemic regions.

Arterial blood gas parameters of normal foals born at 1500 metres elevation

REASONS FOR PERFORMING STUDY

Arterial blood gas analysis is widely accepted as a diagnostic tool to assess respiratory function in neonates. To the authors' knowledge, there are no published reports of arterial blood gas parameters in normal neonatal foals at altitude.

OBJECTIVE

To provide information on arterial blood gas parameters of normal foals born at 1500 m elevation (Fort Collins, Colorado) in the first 48 h post partum.

HYPOTHESIS

Foals born at 1500 m will have lower PaO2 and PaCO2 than foals born at sea level due to low inspired oxygen and compensatory hyperventilation occurring at altitude.

METHODS

Sixteen foals were studied. Arterial blood gas analysis was performed within 1 h of foaling and subsequent samples were evaluated at 3, 6, 12, 24 and 48 h post partum. Data were compared to those previously reported in healthy foals born near sea level.

RESULTS

Mean PaO2 was 53.0 mmHg (7.06 kPa) within 1 h of foaling, rising to 67.5 mmHg (9.00 kPa) at 48 h post partum. PaCO2 was 44.1 mmHg (5.88 kPa) within one hour of foaling, falling to 38.3 mmHg (5.11 kPa) at 48 h. Both PaO2 and PaCO2 were significantly lower in foals born at 1500 m elevation than those near sea level at several time points during the first 48 h.

CONCLUSIONS AND POTENTIAL RELEVANCE

Foals at 1500 m elevation undergo hypobaric hypoxia and compensatory hyperventilation in the first 48 h. Altitude specific normal arterial blood values are an important reference for veterinarians providing critical care to equine neonates.

Lack of correlation between antibody titers to fibrinogen-binding protein of Streptococcus equi and persistent carriers of strangles

Previously published studies have neither used nor reported the results of an indirect enzyme-linked immunosorbent assay (iELISA) to measure serologic responses in natural outbreaks of strangles. The concept of using serologic responses to identify persistent carriers of Streptococcus equi has been proposed but not scientifically evaluated. The specific aims of the current study were to determine the duration and level of truncated fibrinogen-binding protein-specific (SeM allele 1) antibody production in ponies involved in a natural outbreak of strangles and to determine if test results from this serologic iELISA could predict persistent carrier status. Serologic samples were obtained before and after an outbreak of naturally occurring strangles infection. Persistent carriers of S. equi were identified via culture and polymerase chain reaction (PCR) testing of lavage fluid collected from the guttural pouches and nasopharynx or swabs of the nasopharynx after recovery from acute disease and at postmortem examination. Logistic regression analysis was used to determine if an association existed between serologic response and persistent carrier state. The ELISA reported in the current study definitively confirmed a recent exposure to S. equi. However, the measured serologic response did not predict carrier status in this strangles outbreak. Therefore, a guttural-pouch endoscopy with subsequent culture or PCR testing to detect S. equi remains the most accurate method available for the identification of persistent carriers.

Comparison of temperature readings from a percutaneous thermal sensing microchip with temperature readings from a digital rectal thermometer in equids

OBJECTIVE

To compare temperature readings from an implantable percutaneous thermal sensing microchip with temperature readings from a digital rectal thermometer, to identify factors that affect microchip readings, and to estimate the sensitivity and specificity of the microchip for fever detection.

DESIGN

Prospective study.

ANIMALS

52 Welsh pony foals that were 6 to 10 months old and 30 Quarter Horses that were 2 years old.

PROCEDURES

Data were collected in summer, winter, and fall in groups 1 (n = 23 ponies), 2 (29 ponies), and 3 (30 Quarter Horses), respectively. Temperature readings from a digital rectal thermometer and a percutaneous thermal sensing microchip as well as ambient temperature were recorded daily for 17, 23, and 19 days in groups 1 through 3, respectively. Effects of ambient temperature and rectal temperature on thermal sensor readings were estimated. Sensitivity and specificity of the thermal sensor for detection of fever (rectal temperature, >or= 38.9 degrees C [102 degrees F]) were estimated separately for data collection at ambient temperatures <or= 15.6 degrees C (60 degrees F) and > 15.6 degrees C.

RESULTS

Mean ambient temperatures were 29.0 degrees C (84.2 degrees F), -2.7 degrees C (27.1 degrees F), and 10.4 degrees C (50.8 degrees F) for groups 1 through 3, respectively. Thermal sensor readings varied with ambient temperature and rectal temperature. Rectal temperatures ranged from 36.2 degrees to 41.7 degrees C (97.2 degrees to 107 degrees F), whereas thermal sensor temperature readings ranged from 23.9 degrees (75 degrees F) to 42.2 degrees C (75 degrees to 108 degrees F). Sensitivity for fever detection was 87.4%, 53.3%, and 58.3% in groups 1 to 3, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

The thermal sensor appeared to have potential use for initial screening of body temperature in equids at ambient temperatures > 15.6 degrees C.

Risk factors for owner-reported occurrence of equine protozoal myeloencephalitis in the US equine population

BACKGROUND

Equine protozoal myeloencephalitis (EPM) is a serious and often fatal neurologic disease of horses, but few studies have investigated risk factors.

OBJECTIVES

To evaluate operation- and individual-level factors associated with likelihood of the occurrence of EPM.

ANIMALS

Data were collected as part of a study of the US equine industry from 1,178 operations representing 83.9% of horses and 51.6% of operations with > or =3 horses in 28 states.

METHODS

Probability-based sampling was used to enroll representative operations in a cross-sectional study. Interviews were conducted to collect information regarding health and management of horses. A nested case-control study was used to investigate risk factors among individual horses. Interview data were combined with climate data, human population density, and opossum regional ecology categories. Data were analyzed using logistic regression to identify risk factors for the occurrence of EPM.

RESULTS

Owners reported that 95% of EPM cases included in this study were diagnosed by veterinarians. Variables associated with EPM occurrence on premises included opossum regional ecology, reported exposure to small wildlife, climate, terrain, housing, choice of bedding material, method of storing feeds, equine stocking density, and primary use of horses. Among individual horses, age was most strongly associated with disease risk. Associations also were identified with sex, breed, primary use, and participation in competitions.

CONCLUSIONS AND CLINICAL IMPORTANCE

Because the risk of EPM occurrence on operations is closely tied to factors that impact exposure to opossums, their feces, and their environment, controlling these exposures may be important in preventing the occurrence of EPM.

Comparison of Salmonella enterica serotype Infantis isolates from a veterinary teaching hospital

AIMS

To compare Salmonella enterica serotype Infantis isolates obtained from patients or the environment of a veterinary teaching hospital over a period of 9 years following a nosocomial outbreak to determine whether isolates were epidemiologically related or represented unrelated introductions into the hospital environment.

METHODS AND RESULTS

Fifty-six S. Infantis isolates were compared based on their phenotypic (antimicrobial drug [AMD] susceptibility pattern) and genotypic (pulsed-field gel electrophoresis [PFGE] pattern and presence of integrons) characteristics. Epidemiologically unrelated S. Infantis isolates clustered separately from all but two of the hospital isolates, and several isolates from different years and various sources were indistinguishable from each other in cluster analysis of two-enzyme PFGE results. A high percentage of isolates (80.3%) were resistant to at least one AMD, with 67.8% showing resistance to >5 AMD. The majority (74.1%) of isolates tested contained type 1 integrons.

CONCLUSION

Results strongly suggest that there was nosocomial transmission of S. Infantis during the initial outbreak, and that contamination arising from this outbreak persisted across years despite rigorous hygiene and biosecurity precautions and may have led to subsequent nosocomial infections.

SIGNIFICANCE AND IMPACT OF THE STUDY

Evidence of persistence and transmission of Salmonella clones across years, even in the face of rigorous preventive measures, has important implications for other facilities that have experienced outbreaks of Salmonella infections.

Impact of heat stress on the fecal shedding patterns of Salmonella enterica Typhimurium DT104 and Salmonella enterica infantis by 5-week-old male broilers

The objective of this study was to determine if there is an impact of heat stress of broiler chickens on number and survival of two types of Salmonella shed in the chicken's feces after an oral challenge. The data from this study indicate that heat stress did not result in higher levels or longer survival of Salmonella spp. shed in feces. It is possible that the duration or intensity of the heat stress employed was not sufficient or that heat stress does not alter the number or survivability for these particular strains of Salmonella spp. Feces stored at room temperature after collection, resulted in the numbers of both strains of Salmonella increasing by one to three logs in the first week. This finding indicates that there could be an increase in environmental contamination under certain conditions.

Pilot study to evaluate 3 hygiene protocols on the reduction of bacterial load on the hands of veterinary staff performing routine equine physical examinations

Reduction factors (RFs) for bacterial counts on examiners' hands were compared when performing a standardized equine physical examination, followed by the use of one of 3 hand-hygiene protocols (washing with soap, ethanol gel application, and chlorohexidine-ethanol application). The mean RFs were 1.29 log10 and 1.44 log10 at 2 study sites for the alcohol-gel (62% ethyl alcohol active ingredient) protocols and 1.47 log10 and 1.94 log10 at 2 study sites for the chlorhexidine-alcohol (61% ethyl alcohol plus 1% chlorhexidine active ingredients) protocols, respectively. The RFs were significantly different (P < 0.0001) between the hand-washing group and the other 2 treatment groups (the alcohol-gel and the chlorhexidine-alcohol lotion). The use of alcohol-based gels or chlorhexidine-alcohol hand hygiene protocols must still be proven effective in equine practice settings, but in this study, these protocols were equivalent or superior to hand washing for reduction in bacterial load on the hands of people after they perform routine physical examinations.

Impact of hospitalization and antimicrobial drug administration on antimicrobial susceptibility patterns of commensalEscherichia coliisolated from the feces of horses

Objective-To evaluate antimicrobial susceptibility of commensal Escherichia coli strains isolated from the feces of horses and investigate relationships with hospitalization and antimicrobial drug (AMD) administration. Design-Observational study. Animals-68 hospitalized horses that had been treated with AMDs for at least 3 days (HOSP-AMD group), 63 hospitalized horses that had not received AMDs for at least 4 days (HOSP-NOAMD group), and 85 healthy horses that had not been hospitalized or treated with AMDs (community group). Procedures-Fecal samples were submitted for bacterial culture, and up to 3 E coli colonies were recovered from each sample. Antimicrobial susceptibility of 724 isolates was evaluated. Prevalence of resistance was compared among groups by use of log-linear modeling. Results-For 12 of the 15 AMDs evaluated, prevalence of antimicrobial resistance differed significantly among groups, with prevalence being highest among isolates from the HOSP-AMD group and lowest among isolates from the community group. Isolates recovered from the HOSP-AMD and HOSP-NOAMD groups were also significantly more likely to be resistant to multiple AMDs. Resistance to sulfamethoxazole and resistance to trimethoprim-sulfamethoxazole were most common, followed by resistance to gentamicin and resistance to tetracycline. Use of a potentiated sulfonamide, aminoglycosides, cephalosporins, or metronidazole was positively associated with resistance to 1 or more AMDs, but use of penicillins was not associated with increased risk of resistance to AMDs. Conclusion and Clinical Relevance-Results suggest that both hospitalization and AMD administration were associated with prevalence of antimicrobial resistance among E coli strains isolated from the feces of horses.

Evaluation of factors associated with positive IgM capture ELISA results in equids with clinical signs compatible with West Nile virus infection: 1,017 cases (2003)

OBJECTIVE

To describe the prevalence of West Nile virus (WNV) infection and evaluate factors associated with positive IgM capture ELISA results in equids with clinical signs compatible with WNV infection.

DESIGN

Retrospective case series.

SAMPLE POPULATION

Laboratory submission forms from 1,104 equids tested for WNV in Colorado in 2003.

PROCEDURES

Submission forms accompanying samples submitted for detection of WNV via IgM capture ELISA were obtained from the Colorado state veterinarian and diagnostic laboratories performing the tests. Data on signalment, clinical signs, history of vaccination against WNV, and assay results were collected from laboratory submission forms. Equids with clinical signs compatible with WNV infection in which IgM capture ELISA results were positive were considered as case equids.

RESULTS

1,104 equids were tested for WNV; 1,017 (92.1%) had clinical signs compatible with WNV infection. Among equids with clinical signs compatible with WNV infection, the odds of testing positive for WNV via IgM capture ELISA were lower in males and in vaccinated equids and higher in equids with moderate and severe illness, compared with females, unvaccinated equids, and equids with mild illness.

CONCLUSIONS AND CLINICAL RELEVANCE

Among equids with clinical signs compatible with WNV infection, vaccination against WNV, severity of clinical signs, duration of illness, and region in Colorado were associated with increased risk of having a positive IgM capture ELISA result.

Antimicrobial drug use in veterinary medicine

Recognizing the importance of antimicrobial resistance and the need for veterinarians to aid in efforts for maintaining the usefulness of antimicrobial drugs in animals and humans, the Board of Regents of the American College of Veterinary Internal Medicine charged a special committee with responsibility for drafting this position statement regarding antimicrobial drug use in veterinary medicine. The Committee believes that veterinarians are obligated to balance the well-being of animals under their care with the protection of other animals and public health. Therefore, if an animal's medical condition can be reasonably expected to improve as a result of treatment with antimicrobial drugs, and the animal is under a veterinarian's care with an appropriate veterinarian-client-patient relationship, veterinarians have an obligation to offer antimicrobial treatment as a therapeutic option. Veterinarians also have an obligation to actively promote disease prevention efforts, to treat as conservatively as possible, and to explain the potential consequences associated with antimicrobial treatment to animal owners and managers, including the possibility of promoting selection of resistant bacteria. However, the consequences of losing usefulness of an antimicrobial drug that is used as a last resort in humans or animals with resistant bacterial infections might be unacceptable from a public or population health perspective. Veterinarians could therefore face the difficult choice of treating animals with a drug that is less likely to be successful, possibly resulting in prolonged or exacerbated morbidity, to protect the good of society. The Committee recommends that voluntary actions be taken by the veterinary profession to promote conservative use of antimicrobial drugs to minimize the potential adverse effects on animal or human health. The veterinary profession must work to educate all veterinarians about issues related to conservative antimicrobial drug use and antimicrobial resistance so that each individual is better able to balance ethical obligations regarding the perceived benefit to their patients versus the perceived risk to public health. Specific means by which the veterinary profession can promote stewardship of this valuable resource are presented and discussed in this document.

Immunologic responses to West Nile virus in vaccinated and clinically affected horses

OBJECTIVE

To compare neutralizing antibody response between horses vaccinated against West Nile virus (WNV) and horses that survived naturally occurring infection.

DESIGN

Cross-sectional observational study.

ANIMALS

187 horses vaccinated with a killed WNV vaccine and 37 horses with confirmed clinical WNV infection.

PROCEDURE

Serum was collected from vaccinated horses prior to and 4 to 6 weeks after completion of an initial vaccination series (2 doses) and 5 to 7 months later. Serum was collected from affected horses 4 to 6 weeks after laboratory diagnosis of infection and 5 to 7 months after the first sample was obtained. The IgM capture ELISA, plaque reduction neutralization test (PRNT), and microtiter virus neutralization test were used.

RESULTS

All affected horses had PRNT titers > or = 1:100 at 4 to 6 weeks after onset of disease, and 90% (18/20) maintained this titer for 5 to 7 months. After the second vaccination, 67% of vaccinated horses had PRNT titers > or = 1:100 and 14% had titers < 1:10. Five to 7 months later, 33% (28/84) of vaccinated horses had PRNT titers > or = 1:100, whereas 29% (24/84) had titers < 1:10. Vaccinated and clinically affected horses' end point titers had decreased by 5 to 7 months after vaccination.

CONCLUSIONS AND CLINICAL RELEVANCE

A portion of horses vaccinated against WNV may respond poorly. Vaccination every 6 months may be indicated in certain horses and in areas of high vector activity. Other preventative methods such as mosquito control are warranted to prevent WNV infection in horses.

Community-associated methicillin-resistant Staphylococcus aureus in horses and humans who work with horses

OBJECTIVE

To evaluate the prevalence of nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) in horses and horse personnel.

DESIGN

Prospective prevalence study.

SAMPLE POPULATION

972 horses and 107 personnel from equine farms in Ontario, Canada and New York state.

PROCEDURE

Nasal swab specimens were collected from horses and humans on farms with (targeted surveillance) and without (nontargeted surveillance) a history of MRSA colonization or infection in horses during the preceding year. Selective culture for MRSA was performed. Isolates were typed via pulsed-field gel electrophoresis, and antibiograms were determined.

RESULTS

MRSA was isolated from 46 of 972 (4.7%) horses (0/581 via nontargeted surveillance and 46/391 [12%] via targeted surveillance). Similarly, MRSA was isolated from 14 of 107 (13%) humans (2/41 [5%] from nontargeted surveillance and 12/66 [18%] from targeted surveillance). All isolates were subtypes of Canadian epidemic MRSA-5, an uncommon strain in humans. All isolates were resistant to at least 1 antimicrobial class in addition to beta-lactams. On all farms with colonized horses, at least 1 human was colonized with an indistinguishable subtype. For horses, residing on a farm that housed > 20 horses was the only factor significantly associated with MRSA colonization. For humans, regular contact with > 20 horses was the only identified risk factor.

CONCLUSIONS AND CLINICAL RELEVANCE

Results confirm a reservoir of colonized horses on a variety of farms in Ontario and New York and provide evidence that 1 MRSA strain is predominantly involved in MRSA colonization in horses and humans that work with horses.

An overview of infection control strategies for equine facilities, with an emphasis on veterinary hospitals

Infection control entails preventing or minimizing exposure to infectious agents or optimizing resistance to infection at the individual and population levels should exposure occur. The degree to which each of these strategies is applied varies according to the attributes of the disease agent and the population at risk. In developing an infection control, biosecurity, or biocontainment plan, it is important to decide which agent or agents are to be controlled, the method by which they might be introduced to the individual or population, and methods by which they might spread once at a farm or veterinary clinic.

Multidrug-resistant Salmonella and nosocomial infections

Nosocomial infections are a serious threat to optimum patient care. In addition, nosocomial infections can have far-reaching consequences for the hospital personnel and the financial aspects of the hospital. Nosocomial infections with Salmonella spp have been described among hospitalized equine populations more frequently than any other agent. Salmonella spp associated with hospitalized equids often possess more antimicrobial resistance determinants than do Salmonella spp isolated from healthy horses in the general population. There is little evidence to suggest that resistant salmonellae are more virulent than nonresistant forms. MDR forms of Salmonella complicate the selection of appropriate antimicrobials when they are indicated, however. Furthermore, the use of some antimicrobials may apply selection pressure toward enhanced ability of MDR Salmonella to colonize equine patients. Further research should help to elucidate the risky uses of antimicrobials in the hospital setting and define the role of disinfectants and treatments such as NSAIDs in the ecology of MDR forms of nosocomial infections, including Salmonella. In the meantime, thoughtful selection of when and how to use antimicrobials in equine patients, together with deliberate selection of which antimicrobials to use based on monitoring data and other factors, such as safety and spectrum, is advised.

Outcome of equids with clinical signs of West Nile virus infection and factors associated with death

OBJECTIVE

To determine outcome of equids in the western United States with clinical signs of West Nile virus (WNV) infection and identify factors associated with risk of death in infected equids.

DESIGN

Cross-sectional study.

ANIMALS

484 equids in Nebraska and Colorado.

PROCEDURE

Owners of 484 equids with laboratory-confirmed West Nile virus infection in Nebraska and Colorado were contacted by telephone, and a questionnaire was used to obtain information on signalment, management, clinical signs, date of disease onset, duration of disease, WNV vaccination status, and health status at the time of the interview.

RESULTS

137 of 482 (28.4%) animals died or were euthanatized. Ataxia, lethargy, muscle fasciculations, and weakness were the most common clinical signs of disease. Animals > or = 3 years old were more likely to die than were animals < or = 2 years old. Unvaccinated equids were twice as likely to die as were animals that had been vaccinated at least once prior to the onset of disease. Animals that were recumbent and unable to rise were 78 times as likely to die as were animals that never lost the ability to rise. Females were 2.9 times as likely to die as males. Two hundred seventy-one of 339 (79.9%) animals that survived recovered fully; mean duration of disease for these animals was 22.3 days.

CONCLUSIONS AND CLINICAL RELEVANCE

Among equids with WNV infection, age, vaccination status, an inability to rise, and sex were associated with the risk of death.

Gastrointestinal protectants and cathartics

The purpose of this article is to provide the reader with an overview of gastrointestinal cathartics and protectants and to point out possible applications for use in the horse with gastrointestinal disease. Most of the treatments described in this article have been used by the authors with apparent success; however, controlled studies with subsequent publication in the scientific literature with respect to these treatments in the horse are, for the most part, lacking. The authors view this emerging field of treatment as exciting and look forward to substantiating the efficacy of several of the treatments discussed.

Case-control study of factors associated with excessive proportions of early fetal losses associated with mare reproductive loss syndrome in central Kentucky during 2001

OBJECTIVE

To identify factors associated with excessive proportions of early fetal losses associated with mare reproductive loss syndrome in central Kentucky during 2001.

DESIGN

Case-control study.

PROCEDURE

Questionnaires were used to collect information on farm-, pasture-, and individual animal-level factors purportedly associated with mare reproductive loss syndrome. Data were collected for 133 farms (97 with excessive proportions of early feta losses and 36 control farms) representing 6,576 mares.

RESULTS

Factors significantly associated with an increased risk of excessive early fetal losses were exposure to moderate to high concentrations of Eastern tent caterpillars, exposure to cherry trees, farm size > or = 50 broodmares, being bred during February 2001, and frequent exposure to waterfowl. Feeding hay to mares outside was associated with a decreased risk of excessive proportions of early fetal losses. Pasture composition and management factors were not significantly different between affected and control pastures. Individual animal-level factors were investigated on 6 farms representing 340 mares, and age, parity, and pre- and postbreeding treatments were not significantly associated with risk of early fetal loss.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that limiting exposure to Eastern tent caterpillars and cherry trees and feeding hay to mares outside may help decrease the risk of excessive proportions of early fetal losses associated with mare reproductive loss syndrome.

A comparison of dobutamine infusion to exercise as a cardiac stress test in healthy horses

This study was done to determine whether administration of dobutamine would produce echocardiographic and electrocardiographic alterations comparable to those induced by treadmill exercise in healthy horses. Fourteen horses received maximal treadmill exercise and, separately, intravenous dobutamine infusion up to a maximum rate of 50 microg/kg/min. Ten of the 14 horses were euthanized, and the myocardial tissues were examined grossly and histopathologically. No significant differences were found in the chronotropic effects of dobutamine and exercise (P = .905). Dobutamine induced greater interventricular septal thickening during systole (dobutamine = 4.78 cm, exercise = 4.03 cm; P = .004). and greater left ventricular diameters during diastole (dobutamine = 9.73 cm, exercise = 9.26 cm; P = .037), than did exercise treatment. Horses exhibited transient signs of sweating and restlessness during infusion of moderate to maximum doses of dobutamine. Ventricular ectopy seen in 11 of 14 horses was attributed to the arrhythmogenic properties of dobutamine, as well as to increased vagal tone present at low dobutamine doses. Myocardial lesions characteristic of catecholamine myotoxicity were present in 2 of the 10 horses examined. Although dobutamine induces chronotropic and inotropic changes similar to those induced by exercise, the use of high-dose dobutamine as a cardiac stressor in horses cannot be advocated because of potential development of arrhythmias or myotoxicity.

Occurrence of infectious upper respiratory tract disease and response to vaccination in horses on six sentinel premises in northern Colorado

REASONS FOR PERFORMING STUDY

Horses vaccinated against common agents of infectious upper respiratory disease (IURD) may not have detectable serum antibody and may not be protected from clinical disease.

OBJECTIVES

The objectives of this study were to 1) investigate the serological response of horses to vaccination against influenza virus (H3N8 and H7N7) and equine herpesviruses (EHV) in a field setting and 2) evaluate associations among vaccination status, serum antibody concentrations, and occurrences of IURD in monitored horses.

METHODS

In this study, horses on 6 Colorado premises were vaccinated parenterally against influenza virus and EHV, and serological response evaluated. Horses were monitored, and biological samples collected from individuals with clinical IURD and control horses.

RESULTS

Of 173 horses, 61 (35.3%), 21 (12.1%) and 4 (2.3%) seroconverted in response to vaccination against EHV, influenza virus H7N7 and influenza virus H3N8, respectively.

CONCLUSIONS

Outbreaks of IURD in study horses were associated with influenza virus H3N8 and Streptococcus equi infection, and serological response to vaccination with conventional products was poor.

POTENTIAL RELEVANCE

These results confirm that horses may not respond with detectable serological responses to conventional vaccination against common respiratory viruses and, therefore, suggest that alternate methods of protecting horses against common respiratory viruses should be sought.

Detection of Salmonella spp in fecal specimens by use of real-time polymerase chain reaction assay

OBJECTIVE

To use real-time polymerase chain reaction (PCR) technology to develop a highly sensitive and specific diagnostic assay for the detection of Salmonella spp in fecal specimens.

SAMPLE POPULATION

299 fecal specimens from cattle, horses, and dogs.

PROCEDURE

Enrichment of fecal specimens was followed by genomic DNA extraction by use of commercially available isolation kits. Real-time PCR assay was performed to target a Salmonella spp-specific DNA segment. Results of real-time PCR assay were compared with bacterial culture results to determine relative sensitivity and specificity.

RESULTS

Use of the spaQ primer-probe set resulted in a relative sensitivity of 100% and a specificity of 98.2%, compared with bacterial culture results when tested on 299 clinical fecal specimens.

CONCLUSIONS AND CLINICAL RELEVANCE

A rapid, sensitive, and specific assay for the detection of Salmonella spp from enriched clinical fecal specimens was developed. This technique would be highly valuable in clinical settings to help avoid or mitigate the complications arising from an outbreak of salmonellosis in a herd or among patients of a veterinary hospital.

Effects of dietary flaxseed oil supplementation on equine plasma fatty acid concentrations and whole blood platelet aggregation

An 18-week feeding trial was performed to investigate the effects of an omega-3 (n-3) fatty acid-enriched ration on plasma fatty acid concentrations and platelet aggregation in healthy horses. Flaxseed oil served as the source of the n-3 fatty acid alpha-linolenic acid (ALA). Twelve horses were fed dietary maintenance requirements using a complete pelleted ration (80%) and timothy grass hay (20%) for a 2-week acclimation period before being randomly assigned either to a treatment (group 1) or control (group 2) group. Group 2 horses (n = 6) were fed the diet described in the acclimation period, whereas group I horses (n = 6) were fed a 10% flaxseed oil-enriched complete pellet (80%) and grass hay (20%). Biological samples and physical measurements were collected at one point during the acclimation period (week 0) and every 4 weeks thereafter (weeks 4, 8, 12, and 16). Body weight, CBC (including platelet count), plasma fibrinogen. electrolyte (Na, K, and Cl) concentrations, and biochemical profile enzyme activities (aspartate aminotransferase, alkaline phosphatase, gamma-glutamyltransferase, and creatine kinase) did not change markedly with diet. Platelet aggregation was not altered by the supplementation of flaxseed oil in these healthy horses, although increases in plasma cis-polyunsaturated 18-carbon fatty acids C18:3; n-3 (ALA) and C18:2; n-6 (linoleic acid), biologically active C20:5; n-3 (eicosapentaenoic acid [EPA]), and malondialdehyde (MDA) were evident. There were no marked decreases in C20:4; n-6 (arachidonic acid [AA]) or increases in C22:6; n-3 (docosahexaenoic acid [DHA]), signifying that flaxseed oil may have had a high percentage of omega-6 (n-6) fatty acids as well as n-3 fatty acids, and this relatively high n-6: n-3 fatty acid ratio may have affected the biochemical effect of n-3 fatty acids. In healthy horses supplemented with flaxseed oil, platelet aggregation was not altered, which may have been due to the limited biologic effect in healthy subjects or the inability of flaxseed oil to induce the necessary biochemical effect of replacing n-6 fatty acids with n-3 types.

Survey of complications and antimicrobial use in equine patients at veterinary teaching hospitals that underwent surgery because of colic

OBJECTIVE

To determine current practices regarding use of antimicrobials in equine patients undergoing surgery because of colic at veterinary teaching hospitals.

DESIGN

Survey.

SAMPLE POPULATION

Diplomates of the American College of Veterinary Surgeons performing equine surgery at veterinary teaching hospitals in the United States.

PROCEDURE

A Web-based questionnaire was developed, and 85 surgeons were asked to participate. The first part of the survey requested demographic information and information about total number of colic surgeries performed at the hospital, number of colic surgeries performed by the respondent, and whether the hospital had written guidelines for antimicrobial drug use. The second part pertained to nosocomial infections. The third part provided several case scenarios and asked respondents whether they would use antimicrobial drugs in these instances.

RESULTS

Thirty-four (40%) surgeons responded to the questionnaire. Respondents indicated that most equine patients undergoing surgery because of colic at veterinary teaching hospitals in the United States received antimicrobial drugs. Drugs that were used were similar for the various hospitals that were represented, and for the most part, the drugs that were used were fairly uniform irrespective of the type of colic, whereas the duration of treatment varied with the type of colic and the surgical findings. The combination of potassium penicillin and gentamicin was the most commonly used treatment.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of this study document the implementation of recommendations by several authors in veterinary texts that antimicrobial drugs be administered perioperatively in equine patients with colic that are undergoing surgery. However, the need for long-term antimicrobial drug treatment in equine patients with colic is unknown.

An introduction to biosecurity of cattle operations

Recent world events have heightened awareness for the need to safeguard our livestock industries from disease agents. Biosecurity is the outcome of all activities undertaken to preclude introduction of disease agents into an animal population. The concepts of biosecurity are not new. Activities directed at ensuring biosecurity include controlling exposure and optimizing resistance. Programs for biosecurity must be individually tailored to specific situations to account for varying risks and perceptions of risk by decision makers. It is important for practitioners to take a holistic approach to disease control, considering the epidemiology of the disease in addition to the available vaccines and therapeutics.

Population-based study of fecal shedding of Clostridium perfringens in broodmares and foals

OBJECTIVE

To determine the percentage of broodmares and foals that shed Clostridium perfringens in their feces and classify the genotypes of those isolates.

DESIGN

Prospective cross-sectional study.

ANIMALS

128 broodmares and their foals on 6 equine premises.

PROCEDURES

Anaerobic and aerobic bacteriologic cultures were performed on feces collected 3 times from broodmares and foals. All isolates of C. perfringens were genotyped.

RESULTS

Clostridium perfringens was isolated from the feces of 90% of 3-day-old foals and 64% of foals at 8 to 12 hours of age. A lower percentage of broodmares and 1- to 2-month-old foals shed C. perfringens in their feces, compared with neonatal foals. Among samples with positive results, C. perfringens type A was the most common genotype identified (85%); C. perfringens type A with the beta2 toxin gene was identified in 12% of samples, C. perfringens type A with the enterotoxin gene was identified in 2.1% of samples, and C. perfringens type C was identified in < 1% of samples.

CONCLUSIONS AND CLINICAL RELEVANCE

Clostridium perfringens was identified from the feces of all but 6 foals by 3 days of age and is likely part of the normal microflora of neonatal foals. Most isolates from broodmares and foals are C. perfringens type A; thus, the clinical relevance of culture results alone is questionable. Clostridium perfringens type C, which has been associated with neonatal enterocolitis, is rarely found in the feces of horses.

Estimate of the national incidence of and operation-level risk factors for colic among horses in the United States, spring 1998 to spring 1999

OBJECTIVE

To estimate the national incidence of, operation-level risk factors for, and annual economic impact of colic among horses in the United States during 1998 and 1999.

DESIGN

Epidemiologic survey.

ANIMALS

21,820 horses on 1,026 horse operations in 28 states.

PROCEDURES

Horses were monitored for colic for 1 year, and results were recorded in a log that was collected quarterly. Operation-level data were collected via 4 on-site personal interviews. Associations between colic and independent variables adjusted for size of operation were determined.

RESULTS

Annual national incidence of colic in the US horse population was estimated to be 4.2 colic events/100 horses per year. Case fatality rate was 11%, and 1.4% of colic events resulted in surgery. Annual cost of colic in the United States was estimated to be $115,300,000.

CONCLUSIONS AND CLINICAL RELEVANCE

The national impact of equine colic is substantial because of the high case fatality rate.

Factors associated with Salmonella shedding among equine colic patients at a veterinary teaching hospital

OBJECTIVE

To evaluate factors potentially associated with fecal Salmonella shedding among equine patients hospitalized for colic at a veterinary teaching hospital and to determine the effects of probiotic treatment on fecal Salmonella shedding and clinical signs.

DESIGN

Longitudinal study and controlled trial.

ANIMALS

246 equine colic patients.

PROCEDURE

History and medical information were obtained from patient records. Fecal and environmental samples were submitted for aerobic bacterial culture for Salmonella enterica. Fifty-one patients were treated with a commercially available probiotic; 46 were treated with a placebo. Logistic regression was used to evaluate data.

RESULTS

Salmonella organisms were detected in feces from 23 (9%) patients at least once during hospitalization. Patients were more likely to shed Salmonella organisms if diarrhea was evident < or = 6 hours after hospitalization and duration of hospitalization exceeded 8 days (odds ratio [OR], 20.3), laminitis developed during hospitalization (OR, 12.0), results of nasogastric intubation were abnormal (OR, 4.9), leukopenia was evident < or =6 hours after hospitalization (OR, 4.6), or travel time to the teaching hospital exceeded 1 hour (OR, 3.5). Horses treated with the probiotic did not differ from control horses in regard to likelihood of fecal Salmonella shedding (OR, 1.5) or prevalence of clinical signs.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that certain risk factors are associated with fecal shedding of S enterica among equine patients hospitalized at a veterinary teaching hospital because of colic and that pathogen monitoring in patients and the hospital environment and use of barrier nursing precautions for equine colic patients are beneficial.

Putative uremic encephalopathy in horses: five cases (1978-1998)

OBJECTIVE

To determine historical, physical examination, clinicopathologic, and postmortem findings in horses with putative uremic encephalopathy. Design-Retrospective study. Animals-5 horses with renal failure and neurologic disease not attributable to abnormalities in any other organ system.

PROCEDURE

Medical records from 1978 to 1998 were examined for horses with renal disease and neurologic signs not attributable to primary neurologic, hepatic, or other diseases. Signalment, history, physical examination findings, clinicopathologic data, renal ultrasonographic findings, and postmortem data were reviewed.

RESULTS

Of 332 horses with renal disease, 5 met selection criteria. Historical findings, physical examination findings, clinicopathologic data, ultrasonographic data, and postmortem findings were consistent with chronic renal failure. Swollen astrocytes were detected in all 4 horses examined at necropsy.

CONCLUSIONS AND CLINICAL RELEVANCE

A single criterion was not determined to be pathognomonic for uremic encephalopathy in horses. Uremic encephalopathy should be considered as a differential diagnosis in horses with evidence of chronic renal failure and encephalopathic neurologic sign not attributable to other causes. Astrocyte swelling, which was common to all 4 horses examined at necropsy, may serve as a microscopic indicator of uremic encephalopathy in horses.

Antimicrobic and anthelmintic resistance

Antimicrobial and anthelmintic resistance are growing issues for the equine practitioner. The development of antimicrobial or anthelmintic resistance is a source of significant concern because of increased frequency of treatment failures and increased treatment costs. In addition, antimicrobial resistance may have important consequences for public health. Only through judicious use can the efficacy of antimicrobials and anthelmintics be prolonged. This article discusses the development of resistance and suggestions for control.

Operation-management factors associated with early-postnatal mortality of US foals

Of 7320 equine foals reported born alive during 1997 on 1043 operations that had equids on 1 January 1997, and that participated in the United States National Animal Health Monitoring System (NAHMS) Equine 1998 Study, 120 foals were reported to have died (by either euthanasia or natural causes) within the first 2 days of a live birth. The weighted estimate was 1.7% mortality (standard error=0.5) within the first 2 days of live birth for all foals born on operations in the 28 states included in the study.A multivariable logistic-regression model revealed that foals born in the southern region were more likely to have been reported to have died within the first 2 days of live birth than in the western region. In addition, the following operation-level factors were associated with increased odds of a foal dying within the first 2 days of live birth: not routinely testing newborn foals for adequate absorption of colostral immunoglobulins during the first 2 days of life; adding new resident equids to the operation during 1997; having non-resident equids stay on the operation for 1-30 days during 1997; never requiring an official health certificate (for operations that had non-resident equids stay on the operation for 1-30 days); using something other than straw or hay as the predominant bedding type; and feeding equids a vitamin-mineral supplement/premix with forage and/or grain.

Fecal shedding of Salmonella spp by horses in the United States during 1998 and 1999 and detection of Salmonella spp in grain and concentrate sources on equine operations

OBJECTIVE

To estimate prevalence of fecal shedding of Salmonella spp among horses in the US horse population and prevalence of Salmonella spp in grain or other concentrate used as horse feed on equine operations in the United States.

DESIGN

Cross-sectional survey.

SAMPLE POPULATION

Horses on 972 operations in 28 states.

PROCEDURE

Fecal samples were collected from horses resident at each operation. Only a single sample was collected from any individual horse; number of horses from which samples were collected on each operation was determined on the basis of number of horses on the operation. A single sample of grain or concentrate was also collected from each operation. All samples were tested for Salmonella spp by means of bacterial culture.

RESULTS

Overall, 0.8% (SE, 0.5) of resident horses shed Salmonella spp in their feces. The overall prevalence of operations positive for fecal shedding of Salmonella spp (i.e., operations with > or = 1 horse shedding Salmonella spp in its feces) was 1.8% (SE, 0.7). Prevalence of grain or other concentrate samples positive for Salmonella spp was 0.4%. Serotypes of Salmonella spp that were identified in grain or other concentrate were not those typically associated with clinical disease in horses.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that the national prevalence of fecal shedding of Salmonella spp by horses in the United States was 0.8%, and that prevalence of Salmonella spp in grain or other concentrate used for horse feed was 0.4%.

Foaling-management practices associated with the occurrence of enterocolitis attributed to Clostridium perfringens infection in the equine neonate

Enterocolitis associated with Clostridium perfringens (C. perfringens) infection in neonatal foals is often severe and has been associated with a high case-mortality risk. We designed a premises-based survey to evaluate the associations of regional foaling practices, premises environmental management, periparturient foal and brood-mare management, and periparturient brood-mare ration with the occurrence of neonatal enterocolitis attributed to C. perfringens infection. Potential risk factors individually associated with enterocolitis were breed type, housing type at foaling and in the first three days of life, ground/floor surface type at foaling and in the first three days of life, brood-mare ration before and after foaling, and the presence of livestock other than horses on the premises in the past. From the multivariable-logistic regression models, six variables were significantly associated with an increased risk of the outcome of interest (p<0.05): foals of the stock horse type, housing in a stall or drylot in the first three days of life, other livestock present on the premises in the past, foal born on dirt, sand or gravel surface, and low amounts of grass hay and grain fed post-partum. Low grain amounts fed pre-partum represented a decreased risk of the outcome of interest.

The application of technetium-99m hexamethylpropyleneamine oxime (99mTc-HMPAO) labeled white blood cells for the diagnosis of right dorsal ulcerative colitis in two horses

The application of 99mTc-HMPAO labeled white blood cells to support the diagnosis of right dorsal ulcerative colitis was studied in two horses with a history and clinical signs consistent with phenylbutazone toxicity. These images were compared to a reference horse unaffected by right dorsal ulcerative colitis. Blood was collected aseptically in heparinized syringes from the patients for in vitro white blood cell (WBC) radiolabeling. The buffy coat was separated out and radiolabeled with 99mTc-HMPAO. The radiolabeled blood was re-injected i.v. and four images of the right and left side of the patient's abdomen were acquired at 4 hours and 20 hours post-injection. Results of the nuclear study revealed no abnormal findings in the abdomen at the four-hour post-injection images in any horse. Images obtained 20 hours post-injection revealed a linear uptake of radiolabeled WBCs in the right cranioventral abdomen in the region of the right dorsal colon in both horses with right dorsal ulcerative colitis. The reference horse had no radiopharmaceutical uptake in this region. This nuclear imaging study was a rapid, non-invasive method to identify right dorsal colon inflammation. These findings not only supported the diagnosis of right dorsal ulcerative colitis, but also facilitated appropriate medical management of each horse.

Urinary tract neoplasia

This article is a review of reports on neoplasia of the equine urinary tract. Clinical signs associated with equine patients with urinary tract neoplasia are summarized along with a description of diagnostic methods used in such patients. The prognosis for treatment of urinary tract neoplasia is guarded. A review of the limited treatments that have been reported to date are also provided in this article.

Public veterinary medicine: public health. Serologic evaluation of vesicular stomatitis virus exposure in horses and cattle in 1996

OBJECTIVE

To determine potential risk factors for vesicular stomatitis (VS) in Colorado livestock in 1995 and evaluate VS virus (VSV) exposure of Colorado livestock in 1996.

DESIGN

Retrospective case-control study of VS risk factors and seroprevalence evaluation.

SAMPLE POPULATION

Premises included 52 that had VS-positive animals and 33 that did not have VS-positive animals during the 1995 epidemic, and 8 in the vicinity of premises that had VS-positive animals during the 1995 epidemic.

PROCEDURE

Layout and management data for premises were collected during site visits in 1996. Signalment and management data were collected for animals from which samples were obtained, and samples were tested by serologic examination and virus isolation. The VSV seroprevalence rate was estimated for Colorado, using serum obtained for equine infectious anemia testing and from the Market Cattle Identification program in Colorado.

RESULTS

At least 1 animal was seropositive for VSV on 35 of 52 (67%) premises, and 71 of 228 (31%) animals tested were seropositive for VSV. Seroprevalence was 63 of 170 (37%) for horses and 8 of 54 (15%) for cattle. Seroprevalence of VSV in animals from non-study premises in Colorado in 1996 was estimated to be 1.1% in cattle and 0.8% in horses.

CLINICAL IMPLICATIONS

Overall VSV seroprevalence in Colorado livestock was less than seroprevalence in epidemic areas, and seroprevalence rates in epidemic areas were greater for horses than cattle. Results may indicate that some animals had subclinical VSV infection during epidemics and that animals may be exposed to VSV between epidemics.