key: cord-0898765-er41ifu0
authors: Manship, Arlie J.; Blikslager, Anthony T.; Elfenbein, Johanna R.
title: Disease features of equine coronavirus and enteric salmonellosis are similar in horses
date: 2019-01-10
journal: J Vet Intern Med
DOI: 10.1111/jvim.15386
sha: 53c5b444db5bde8e975a22df9e3c80250e8ad3d1
doc_id: 898765
cord_uid: er41ifu0

BACKGROUND: Equine coronavirus (ECoV) is an emerging pathogen associated with fever and enteric disease in adult horses. Clinical features of ECoV infection have been described, but no study has compared these features to those of Salmonella infections. OBJECTIVES: Compare the clinical features of ECoV infection with enteric salmonellosis and establish a disease signature to increase clinical suspicion of ECoV infection in adult horses. ANIMALS: Forty‐three horses >1 year of age with results of CBC, serum biochemistry, and fecal diagnostic testing for ECoV and Salmonella spp. METHODS: Medical records of horses presented to the North Carolina State University Equine and Farm Animal Veterinary Center (2003‐016) were retrospectively reviewed. Horses were divided into 3 groups based on fecal diagnostic test results: ECoV‐positive, Salmonella‐positive, or unknown diagnosis (UNK). Time of year presented, clinical signs, CBC, and serum biochemistry test results were recorded. Data were analyzed by 1‐way analysis of variance, Kruskal‐Wallis test, or Fisher's exact test with significance set at P < .05. RESULTS: Most common presenting complaints were fever and colic and were similar across groups. Horses with ECoV had significantly decreased neutrophil counts when compared to those with no diagnosis but were not different from horses with Salmonella. Horses with Salmonella had significantly lower mean leukocyte counts compared to those with UNK. No significant differences were found among groups for any other examined variable. CONCLUSIONS AND CLINICAL IMPORTANCE: Equine coronavirus and Salmonella infections share clinical features, suggesting both diseases should be differential diagnoses for horses with fever and enteric clinical signs.

Horses presenting with fever and nonspecific clinical signs of illness can present a diagnostic challenge for practitioners. Equine coronavirus (ECoV) is a Betacoronavirus that is emerging as an agent isolated in association with outbreaks and sporadic cases of fever and enteric disease in adult horses worldwide. Recent reports have associated ECoV with outbreaks of enteric and pyrogenic disease causing substantial morbidity and higher than expected mortality in certain horse populations. 1 

Draft Horses led to fever and nonspecific signs of illness in 2 of 3 animals, suggesting that this virus may be a primary pathogen of adult horses although the molecular details of ECoV infection in adult horses remain unclear. 4 Readily available molecular diagnostic tests and increased awareness of ECoV have facilitated recognition of ECoV as a potential pathogen. [5] [6] [7] The preferred method for diagnosis of ECoV is quantitative PCR on fresh fecal samples, but outbreak reports indicate that horses clinically affected with ECoV are not always accurately identified by a single fecal PCR test. 6, 7 Thus, it is Abbreviations: ECoV, equine coronavirus; NSAID, nonsteroidal anti-inflammatory drug; UNK, unknown diagnosis. important to develop a disease signature characterizing clinical features common to ECoV-infected horses to improve clinical recognition of the pathogen.

In contrast to ECoV, Salmonella enterica is a well-established cause of fever and enteric disease in horses. 8 Salmonella can cause acute and chronic diarrheal disease, neonatal bacteremia, or subclinical colonization of apparently healthy horses. 9 Like ECoV, Salmonella can cause both outbreaks and sporadic illnesses and, as a result, this pathogen is a primary target of hospital biosecurity programs. 10 Diagnosis is made by enrichment culture or PCR using fecal samples, with improved diagnostic sensitivity with sequential sampling. [11] [12] [13] Horses affected by ECoV and Salmonella can have indistinguishable clinical signs including fever, anorexia, abnormal fecal character, malaise, and colic. 6, 7, 9, 14 Thus, our objective was to compare clinical features associated with ECoV infection to those associated with Salmonella infection in a population of ill horses. A secondary objective was to identify a clinical signature of ECoV infection in horses. We hypothesized that adult horses with ECoV infection would more likely to be leukopenic than would horses diagnosed with Salmonella infection. All data were entered into a digital collection sheet. Patient data collected included signalment, month and year of presentation, and presenting complaint. The month of presentation was grouped into season with winter defined as December-February, spring defined as March-May, summer defined as June-August, and fall defined as September-November. Presenting complaints were collected from the records as defined by the owner, the referring veterinarian, or both.

The admission rectal temperature, heart and respiratory rates, mucous membrane color, capillary refill time, and fecal consistency were recorded. Mucous membrane color was considered abnormal if the medical record indicated the presence of a toxic line, hyperemia, or purple or pale mucous membranes; pink was considered normal. The capillary refill time was considered abnormal if >2 seconds. Fecal character was considered abnormal if the medical record described the feces as soft, cow-pie, loose, or diarrhea. The hematocrit, total white blood cell count, fibrinogen concentration, platelet count, and, where available, results of a manual differential cell count were collected and laboratory reference ranges used for data analysis. The serum total protein, albumin and globulin concentrations, gamma-glutamyl transferase activity, and bilirubin, creatinine, sodium, and potassium concentrations were recorded and laboratory reference ranges used for data analysis. On the occasion that fecal diagnostic testing occurred during hospitalization for an unrelated event, laboratory analysis and physical examination variables were included from the event that prompted fecal diagnostic testing according to the infectious disease policy or discretion of the attending clinician.

Data analysis was performed using GraphPad Prism v7.0c (La Jolla, California). Data were assessed for normality using the D'Agostino-Pearson Omnibus test. For normally distributed data, a 1-way analysis of variance was used to determine differences among groups and a post hoc Tukey's test was used for multiple comparisons. For nonnormally distributed data, a Kruskal-Wallis test with a post hoc Dunn's test for multiple comparisons was used to determine differences among groups. A chi-square test was used to determine seasonal distribution of cases. Fisher's exact test was used to establish likelihood of an abnormal test result, and odds ratios were calculated using the Baptista-Pike method. For all tests, significance was set at P < .05.

Forty-three horses met the inclusion criteria. One horse did not have CBC data available for the duration of hospitalization and was removed from analysis. Not all data were available for all horses. Horses ranged in age from 1 to -25 years (mean, 10.5 years) and included a variety of breeds, with the largest single group being Warmbloods (12/42; 29%).

There were 25 geldings, 15 mares, and 2 stallions. Complete patient demographic data are presented in supplemental Table 1 .

Eight of 42 (19%) horses were classified as ECoV-positive, 12 of 42 (29%) were classified as Salmonella-positive, and 22 of 42 (52%) were UNK. The presenting complaints recorded at the time of admission were similar among groups (Table 1) . Fever (21/42; 50%) and colic (11/42; 26%) were the most common presenting complaints, followed by anorexia and diarrhea (9/42; 21% each). Presenting physical examination findings were similar among groups (supplemental Table 2 No significant differences were found for any variable between horses diagnosed with ECoV and Salmonella. Horses with ECoV had significantly lower neutrophil counts than UNK ( Figure 3A) . However, horses with ECoV were no more likely to be neutropenic than horses with Salmonella (odds ratio, 0.909; 95% confidence interval, 0.177-3.912) or UNK (odds ratio, infinity; 95% confidence interval, 0.891-infinity). The total white blood cell count was significantly lower in horses with Salmonella than in UNK horses ( Figure 2 ). Horses with Salmonella were more likely to be leukopenic than were UNK horses (odds ratio, 11; 95% confidence interval, 1.521-127.8) but no more likely to be leukopenic than ECoV (odds ratio, 0.152; 95% confidence interval, 0.011-1.361). No significant differences in lymphocyte or platelet counts or fibrinogen concentration were found among groups ( Figure 3C,D) .

Serum biochemistry data are summarized in Table 2 

We compared the clinical features of ECoV and Salmonella infections in adult horses to establish a disease signature for ECoV infection. We hypothesized that horses with ECoV would be more likely to be leukopenic than those with Salmonella infections. Our data indicate that horses with ECoV infection have significantly lower neutrophil counts than do those without a diagnosis for their fever and enteric disease.

Consistent with prior work, we also found a significant decrease in total white blood cell count in horses with a diagnosis of Salmonella. 14 Although our data do not allow us to accept our hypothesis, the data suggest that ECoV and Salmonella infections have indistinguishable clinical features in adult horses presenting to a tertiary referral hospital. All of the documented presenting complaints were recorded and summarized. More than 1 complaint could be registered at the time of admission or start of fecal diagnostic testing. Abbreviation: ECoV, equine coronavirus. nal dysfunction in addition to fever and anorexia. 3, 4, 6 We also found that fever and anorexia were the most common presenting complaints for all horses in our study, regardless of the diagnosis. The next most common clinical signs were colic and diarrhea, and the combination of fever with colic or diarrhea likely prompted clinicians to perform fecal diagnostic testing because these clinical signs are highly associated with a positive diagnosis of Salmonella in horses. [14] [15] [16] inoculation of Japanese racehorses with ECoV caused a decrease in total white blood cell count, with only 1 of 3 developing leukopenia, but no differential cell counts were available. 4 An additional report suggests that as many as 65% of horses with ECoV are neutropenic, but lack of case information precludes comparisons with our study. 17 Our finding that ECoV horses had significantly lower neutrophil counts than horses with UNK is consistent with the available literature and suggests that neutropenia may be an important feature of ECoV infection.

In addition to the decreased neutrophil count, we found thrombocytopenia and hypoproteinemia in half of our ECoV horses. However, no significant differences in platelet count or protein concentration were found among groups. This finding is in contrast to a report from an ECoV outbreak that documented thrombocytopenia in 25% and hypoproteinemia in 0% of cases. 3 Our case sample population was taken from a tertiary care referral hospital, and it is possible that our cases represent individuals that are most severely affected thus prompting referral for hospitalization. Additional work is needed to establish whether thrombocytopenia or hypoproteinemia are consistent features of ECoV infection.

One limitation of our retrospective study is the small sample size of each group. To increase the number of horses in the study population, we defined the UNK group as a horse that had 3 negative fecal We observed significantly lower neutrophil counts in the ECoV population as compared with UNK horses. In addition, we found no differences in clinical or hematologic abnormalities among horses diagnosed with ECoV and Salmonella. Therefore, the results of our study suggest that ECoV should be included in the differential diagnoses for horses presenting with fever, anorexia, intestinal disease, and neutropenia. Molecular diagnostic testing for both ECoV and Salmonella should be performed to aid diagnosis and improve hospital and on-farm biosecurity measures in these cases.

This work was performed at the North Carolina State University

Equine and Food Animal Veterinary Center. A portion of this work was presented at the 2016 ACVIM Forum, Denver, CO.

Isolation of an equine coronavirus from adult horses with pyrogenic and enteric disease and its antigenic and genomic characterization in comparison with the NC99 strain

Epidemic of equine coronavirus at Obihiro racecourse, Hokkaido, Japan in 2012

Disease associated with equine coronavirus infection and high case fatality rate

Experimental inoculation of equine coronavirus into Japanese draft horses

First detection of equine coronavirus (ECoV) in Europe

Emerging outbreaks associated with equine coronavirus in adult horses

Equine coronavirus: an emerging enteric virus of adult horses

Equine salmonellosis: a contemporary view

Colitis: differential diagnosis and treatment

Managing Salmonella in Equine Populations

Salmonella shedding in the equine

Comparison of rectal mucosal cultures and fecal cultures in detecting salmonella infection in horses and cattle

Diagnosing salmonellosis in horses culturing of multiple versus single faecal samples

Identification of predictors of salmonella shedding in adult horses presented for acute colic

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

Epidemiologic study of salmonellae shedding in the feces of horses and potential risk factors for development of the infection in hospitalized horses

Enteric coronavirus infection in adult horses

Comparison of clinical, microbiologic, and clinicopathologic findings in horses positive and negative for Clostridium difficile infection

Information section at the end of the article. How to cite this article: Manship AJ, Blikslager AT, Elfenbein JR. Disease features of equine coronavirus and enteric salmonellosis are similar in horses

Authors declare no conflict of interest.

Authors declare no off-label use of antimicrobials.

Authors declare no IACUC or other approval was needed.

Authors declare human ethics approval was not needed for this study.

https://orcid.org/0000-0002-0867-7310Johanna R. Elfenbein https://orcid.org/0000-0002-4764-0713