Disease features of equine coronavirus and enteric salmonellosis are similar in horses

Case series report: Equine coronavirus in Australia

BACKGROUND

Equine Coronavirus (ECoV) can cause gastrointestinal disease and was first described in 2000 in the USA followed by several international outbreak case reports. Disease manifestation is characterised by vague clinical signs, including mild pyrexia, lethargy and anorexia. Morbidity ranges greatly from 10% to 83%. Although uncommon, ECoV may result in death secondary to disruption to the gastrointestinal barrier causing endotoxaemia and hyperammonaemic encephalopathy. Unfortunately to date, there is no vaccine available to prevent ECoV.

CASE REPORTS

Three faecal quantitative polymerase chain reaction (qPCR)-positive ECoV cases are described that presented with mild to severe colic signs: a 2-year-old Miniature Pony gelding from South Australia, an 8-year-old Arabian Riding Pony gelding, and a 6-year-old Warmblood mare, both from Western Australia. The diagnosis was based on a positive faecal qPCR, which is currently the gold standard diagnostic tool. All horses in this case series survived after medical management. The Miniature Pony presented with anorexia and mild colic signs. On day 5, the pony revealed severe colic signs unresponsive to analgesia along with severe abdominal distension secondary to caecal distension requiring surgical intervention.

CONCLUSION

To the authors' knowledge, this case series is the first published report of ECoV cases in Australia, and it adds both to the clinical description of the disease in horses and to the differential diagnosis list of colic signs.

A Review of Epithelial Ion Transporters and Their Roles in Equine Infectious Colitis

Equine colitis is a devastating disease with a high mortality rate. Infectious pathogens associated with colitis in the adult horse include Clostridioides difficile, Clostridium perfringens, Salmonella spp., Neorickettsia risticii/findlaynesis, and equine coronavirus. Antimicrobial-associated colitis can be associated with the presence of infectious pathogens. Colitis can also be due to non-infectious causes, including non-steroidal anti-inflammatory drug administration, sand ingestion, and infiltrative bowel disease. Current treatments focus on symptomatic treatment (restoring fluid and electrolyte balance, preventing laminitis and sepsis). Intestinal epithelial ion channels are key regulators of electrolyte (especially sodium and chloride) and water movement into the lumen. Dysfunctional ion channels play a key role in the development of diarrhea. Infectious pathogens, including Salmonella spp. and C. difficile, have been shown to regulate ion channels in a variety of ways. In other species, there has been an increased interest in ion channel manipulation as an anti-diarrheal treatment. While targeting ion channels also represents a promising way to manage diarrhea associated with equine colitis, ion channels have not been well studied in the equine colon. This review provides an overview of what is known about colonic ion channels and their known or putative role in specific types of equine colitis due to various pathogens.

Presence of Equine and Bovine Coronaviruses, Endoparasites, and Bacteria in Fecal Samples of Horses with Colic

Acute abdominal pain (colic) is one of the major equine health threats worldwide and often necessitates intensive veterinary medical care and surgical intervention. Equine coronavirus (ECoV) infections can cause colic in horses but are rarely considered as a differential diagnosis. To determine the frequency of otherwise undetected ECoV infections in horses with acute colic, fresh fecal samples of 105 horses with acute colic and 36 healthy control horses were screened for viruses belonging to the Betacoronavirus 1 species by RT-PCR as well as for gastrointestinal helminths and bacteria commonly associated with colic. Horses with colic excreted significantly fewer strongyle eggs than horses without colic. The prevalence of anaerobic, spore-forming, gram-positive bacteria (Clostridium perfringens and Clostridioides difficile) was significantly higher in the feces of horses with colic. Six horses with colic (5.7%) and one horse from the control group (2.8%) tested positive for Betacoronaviruses. Coronavirus-positive samples were sequenced to classify the virus by molecular phylogeny (N gene). Interestingly, in three out of six coronavirus-positive horses with colic, sequences closely related to bovine coronaviruses (BCoV) were found. The pathogenic potential of BCoV in horses remains unclear and warrants further investigation.

Equine Coronaviruses

Coronaviruses are a group of related RNA viruses that cause diseases in mammals and birds. In equids, equine coronavirus has been associated with diarrhea in foals and lethargy, fever, anorexia, and occasional gastrointestinal signs in adult horses. Although horses seem to be susceptible to the human severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) based on the high homology to the ACE-2 receptor, they seem to be incidental hosts because of occasional SARS-CoV-2 spillover from humans. However, until more clinical and seroepidemiological data are available, it remains important to monitor equids for possible transmission from humans with clinical or asymptomatic COVID-19.

Potomac Horse Fever

Potomac horse fever (PHF) is a common cause of equine colitis in endemic areas. Until recently, the only causative agent known to cause PHF was Neorickettsia risticii. However, N. findlayensis has been isolated from affected horses. Horses typically become infected upon ingestion of Neorickettsia spp.-infected trematodes within aquatic insects. The most common clinical signs include diarrhea, fever, anorexia, lethargy and colic. The diagnostic test of choice for PHF is PCR of blood and feces. Tetracyclines remain an effective treatment. Supportive care, including fluid therapy, colloid administration, NSAID and anti-endotoxin medication, and digital cryotherapy, is also necessary in some cases.

Risk factors associated with an outbreak of equine coronavirus at a large farm in North Carolina

Background

Equine coronavirus (ECoV) leads to outbreaks with variable morbidity and mortality. Few previous reports of risk factors for infection are available in the literature.

Objectives

To describe unique clinical findings and risk factors for infection and development of clinical disease.

Animals

135 horses on a farm affected by ECoV outbreak.

Methods

Retrospective cohort study. Data obtained included age, breed, gender, activity level, housing, and feed at the onset of the outbreak. Factors were evaluated for assessment of risk of infection using simple logistic regression or Fisher's exact test. Significance was set at p ≤ 0.05.

Results and findings

Forty-three of 54 (79.6%) horses tested on the farm were positive on fecal PCR for ECoV, and 17 horses (12.6%) developed clinical signs consistent with ECoV. Out of 17 horses in which the presence or absence of signs of colic was noted, 6 of 17 (35.3%) showed signs of colic. Three of these horses had small colon impactions, 2 of which required surgical intervention. Significant risk factors for having positive PCR results included being primarily stalled (OR 167.1, 95% CI 26.4-1719), housing next to a positive horse (OR 7.5, 95% CI 3.1-19.0), being in work (OR 26.9, 95% CI 4.6-281.9), being fed rationed hay vs. ad libitum (OR 1,558, 95% CI 130.8-15,593), and being fed alfalfa hay (OR 1,558, 95% CI 130.8-15,593).

Conclusions and clinical importance

This report describes risk factors for ECoV infection many of which were associated with intensive management of show horses. Clinicians should be aware that clinical signs vary and can include severe colic.

Acute diarrhea in horses: A multicenter Canadian retrospective study (2015 to 2019)

This study describes the clinicopathological findings, diagnostic approach, treatment, and factors associated with non-survival of diarrheic horses admitted to 4 Canadian university teaching hospitals between 2015 and 2019. A total of 300 horses, ≥1-year-old, with acute diarrhea were included and represented 1.6% (300/18 481; range: 0.7 to 3%) of admissions during that period, 70% of the horses survived to discharge. Testing for enteropathogens was limited to a single fecal culture for Salmonella spp. in most cases. An enteropathogen was identified in 14% (42/300) of the horses, but in the hospital with higher testing rates enteropathogens were detected in 29% (16/55) of cases. Neorickettsia risticii was the pathogen most frequently detected (31%, 32/102). Antimicrobial drugs and plasma were administered to 57 and 8% of the cases, respectively. Laminitis occurred in 24/298 (8%) of the horses. A multivariable regression model identified an association between non-survival of diarrheic horses and colic signs, increased heart rate, packed cell volume, creatinine concentration, and decreased total protein concentration. A standardized approach for pathogen detection in diarrheic horses is not consistent among Canadian veterinary teaching hospitals, and testing for known pathogens is limited. Signs of colic, severe dehydration, endotoxemia, and hypoproteinemia are associated with non-survival of diarrheic horses.

[Management and hygiene measures during an outbreak of herpes, influenza, strangles or infections with multidrug resistant bacteria]

The aim of this review is to describe general guidelines of hygiene measures in the horse stable as well as to provide current recommendations for an outbreak of a common infectious disease. General cleanliness, hand hygiene, avoidance of stress, regular deworming, and vaccinations belong to the basic hygiene measures in a horse herd. All new or returning equids should be submitted to a quarantine period as an important prevention measure. Repeated washing and disinfection of hands may prevent spreading of infectious agents to people and horses.The conception of a hygiene plan, including general biosecurity procedures and standard operating procedures in a case of an outbreak of an infectious disease, zoonosis, or colonization with multi-resistant bacteria is strongly recommended. As soon as the disease is suspected, extended hygiene measures including protective clothing, cleaning, disinfection, and isolation of potentially infected animals should be implemented. Prompt confirmation of the causative agent by examination of appropriate samples is crucial. It is important to adjust all safety measures based on the contagious nature of the respective pathogen and its major transmission routes. Apart from a lock-down of the stable, clinic or show grounds, the segregation of horses plays an important role. Implementation of the "traffic light system" is recommended. In this, the red group ("infected") include animals with clinical signs of the disease or that have been tested positive. All horses with possible pathogen contact should be allocated to a yellow group ("suspected") and regularly controlled for the signs of infection and fever. Clinically normal horses without contact to the infected animals belong to the green group ("healthy"). A change of protective clothing and an extensive disinfection should be performed when moving between the groups.The extended hygiene measures are to be maintained until all animals have been tested negative or fail to exhibit clinical signs of the disease for a certain time period.

The comparative pathology of enterocolitis caused by Clostridium perfringens type C, Clostridioides difficile, Paeniclostridium sordellii, Salmonella enterica subspecies enterica serovar Typhimurium, and nonsteroidal anti-inflammatory drugs in horses

To determine if there were significant differences produced by 5 of the most prevalent causes of equine enterocolitis, we studied retrospectively the gross and microscopic pathology of 90 cases of enterocolitis submitted to the San Bernardino laboratory of the California Animal Health and Food Safety Laboratory. Included were cases caused by Clostridium perfringens type C (CP; n = 20), Clostridioides difficile (CD; n = 20), Paeniclostridium sordellii (PS; n = 15), Salmonella enterica subspecies enterica serovar Typhimurium (ST; n = 20), and NSAID intoxication (NS; n = 15). Grossly, necrotizing hemorrhagic typhlocolitis was seen most frequently in cases of CD, ST, and NS disease. Cases of CP and PS had enteritis or colitis in similar percentages. Congestion, hemorrhage, and pleocellular inflammatory infiltrates followed by mucosal and submucosal necrosis were the main lesions found in horses with enteritis or colitis produced by any of the etiologic agents investigated. Severe lesions were more frequent in cases of CD and CP than in cases associated with any of the other 3 etiologies. Pseudomembranes were observed with similar prevalence in the small intestine and colon affected by all agents studied. Thrombosis of the lamina propria and/or submucosa was observed in ~50% of the cases of enteritis and colitis by all etiologies, except for PS, in which the majority of the cases had thrombosis. Gross and microscopic lesions of enterocolitis were not sufficiently specific for any of these etiologic agents to enable these enteritides to be distinguished by gross and/or histologic examination.

Detection of pathogens in blood or feces of adult horses with enteric disease and association with outcome of colitis

Background

Rates of detecting ≥1 potential enteric pathogens (PEP) or toxins (PEP‐T) in feces, blood, or both of horses ≥6 months of age with enteric disease and impact of multiple detections on outcome of horses with colitis has not been reported.

Objective

To determine detection rates of PEP/PEP‐T in feces, blood, or both of horses with enteric disease and effect of detecting multiple agents on outcome of horses with colitis.

Animals

Thirty‐seven hundred fifty‐three fecal samples submitted to IDEXX Laboratories and 239 fecal and blood samples submitted to Michigan State University's Veterinary Diagnostic Laboratory (MSUVDL).

Methods

Retrospective evaluation of PEP/PEP‐T testing results was performed to determine rates of detection of 1 or more PEP/PEP‐T. Impact of detecting multiple agents on outcome was assessed in 239 horses hospitalized for colitis.

Results

One or more PEP/PEP‐T was detected in 1175/3753 (31.3%) and 145/239 (60.7%) of samples submitted to IDEXX Laboratories and MSUVDL, respectively. In a hospitalized cohort, survival to discharge was lower (76%) in horses with 1 agent, compared to horses with either no (88%) or multiple (89%) agents. There was no difference (P = .78) in days of hospitalization between horses with 0 (1–17), 1 (1–33), and > 1 positive (1–20) result. There was no difference in cost of hospitalization (P = .25) between horses with 0 ($2357, $1110‐15 553), 1 ($2742, $788‐11 005), and >1 positive ($2560, $1091‐10 895) result.

Conclusions and Clinical Importance

Detection rates of PEP/PEP‐T in horses with colitis vary with cohorts and tests performed. Detection of more than 1 PEP or PEP‐T did not affect outcome.

Risk factors for laminitis and nonsurvival in acute colitis: Retrospective study of 85 hospitalized horses (2011-2019)

Background

Acute colitis is a serious cause of morbidity and death in horses. Recent studies have compared clinical features of coronavirus and salmonellosis, but no study has compared clinical features of enteric salmonellosis, coronavirus, and neorickettsiosis.

Hypothesis/Objectives

To identify risk factors for laminitis and nonsurvival to discharge in horses with enteric salmonellosis, coronavirus, or neorickettsiosis.

Animals

Eighty‐five horses hospitalized for acute colitis from 2011 to 2019.

Methods

Retrospective case series. Medical record review (2011‐2019) of adult (≥2 years) horses with colitis. Primary outcomes were laminitis and survival to discharge. Multivariable logistic regression was performed to assess association between variables and the development of laminitis. Stepwise Cox regression was performed to assess association between variables and survival.

Results

Seventeen of 85 (20%) horses developed laminitis during hospitalization. Neorickettsiosis cases (11/26, 42%) were more likely to develop laminitis than coronavirus (0/16, 0%) cases (odds ratio [OR] 24.48; 95% confidence interval [CI]: 1.33‐451.74, P = .03). There was no significant difference in laminitis between salmonellosis and neorickettsiosis cases (OR 0.27; 95% CI: 0.07‐1.07, P = .06). Admission heart rate (OR 1.08; 95% CI: 1.02‐1.15, P = .01), total solids (OR 0.17; 95% CI: 0.06‐0.54, P = .003), band neutrophils (OR 1248.47; 95% CI: 6.62‐235 540, P = .008), and bicarbonate concentration (OR 0.68; 95% CI: 0.5‐0.92, P = .01) were predictive of development of laminitis during hospitalization. Sixty‐three of 85 (74%) horses survived to discharge: 16/16 (100%) coronavirus cases, 17/26 (65%) neorickettsiosis cases, 14/20 (70%) salmonellosis cases, and 16/23 (70%) unknown cases. Packed cell volume (hazard ratio [HR] 1.17; 95% CI: 1.09‐1.26, P < .001), L‐lactate concentration (HR 1.33; 95% CI: 1.14‐1.55, P < .001), and development of laminitis (HR 7.07; 95% CI: 1.67‐29.95, P = .008) were retained in the final multivariable model for prediction of nonsurvival to discharge.

Conclusion and Clinical Importance

Nonsurvival and laminitis rates were high, likely related to the presence of neorickettsiosis in the region.

Developmental Results of a Vaccine against Salmonella-Induced Equine Abortion

An inactivated vaccine based on the Sal. abortus equi BN-12 strain with the Bac. subtilis TNP-3 strain filtrate used as immunomodulator has been developed in order to prevent salmonella-induced equine abortion. Preclinical and clinical trials with the white mice and the horses, respectively, are carried out. The lack of toxicity is proven. The vaccine immunogenicity for mouse and mare models comprised 90 and 100%, respectively. The industrial vaccine tests showed that the industrial output of foals increased by 13.8% after immunization. Cost-effectiveness of the vaccine used with the Bac. subtilis TNP-3 strain filtrate comprised 14.1 rubles per 1 ruble of costs, which was 1.8-fold greater when compared to the vaccine used with a polyribonate medicine. It is ascertained that administration of the inactivated vaccine with the Bac. subtilis TNP-3 strain is an effective method to prevent infectious abortion. Scientific and technical documentation is developed based on the survey results in order to submit it for approval to the Rosselkhoznadzor Federal Service for Veterinary and Phytosanitary Surveillance. The instruction is compliant with the approved use. The registration certificate (71-1-10.19-4495 no. PVR-1-1-.6/01631, as of June 10, 2019) has been issued.

Equine Coronavirus-Associated Colitis in Horses: A Retrospective Study

Equine coronavirus (ECoV) is a known cause of fever, anorexia, and lethargy in adult horses. Although there are multiple reports of ECoV outbreaks, less is known about the clinical presentation of individual horses during a nonoutbreak situation. The purpose of this study was to describe the clinical presentation of horses diagnosed with ECoV infection that were not associated with an outbreak. Medical records of all horses admitted to Washington State University, Veterinary Teaching Hospital, during an 8-year period were reviewed (2010-2018). The five horses included in this study were older than 1 year of age, were diagnosed with colitis, tested positive for ECoV using real-time polymerase chain reaction, and were negative to other enteric pathogens. Interestingly, 4 of 5 horses had moderate to severe diarrhea, 3 had abnormal large colon ultrasonography, 2 had transient ventricular tachycardia and 2 had clinicopathologic evidence of liver dysfunction. ECoV should be included as a differential diagnosis for individual horses presenting with anorexia, fever, lethargy, and colitis. Early identification of ECoV cases is key to implement appropriate biosecurity measures to prevent the potential spread of this disease.

Retrospective Analysis of Aetiological Agents Associated with Pulmonary Mycosis Secondary to Enteric Salmonellosis in Six Horses by Panfungal Polymerase Chain Reaction

Pulmonary mycosis secondary to enterocolitis is an uncommon diagnosis in equine medicine, but is thought to result from mucosal compromise and translocation of enteric fungi. The aetiological agent associated with translocation is often identified based on fungal culture or hyphal features in histological sections. In order to understand better the aetiological agents involved, six horses diagnosed with Salmonella enteritis and concurrent pulmonary mycosis were identified retrospectively through a database search of veterinary teaching hospital records. Samples from these cases were subjected to polymerase chain reaction and sequencing of the internal transcribed spacer 2 (ITS-2) located between the 5.8S and 28S rRNA genes to identify the aetiological agent involved. Sequencing identified Aspergillus fumigatus, Aspergillus flavus, Fusarium spp., Cladosporium spp. and Curvularia spp. A single case had a dual infection with Fusarium spp. and A. fumigatus.

Disease features of equine coronavirus and enteric salmonellosis are similar in horses

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.