Persistence and chronic urinary shedding of the aphthovirus equine rhinitis A virus

Viral Safety Issues in the Production and Manufacturing of Human Immunoglobulin Preparations from Equine Plasma/Serum

The current Russian and foreign pharmacopoeias either do not provide any information about existing types of viral diseases in horses or do not present it in full. Data of modern domestic and foreign literature was used to prepare the most complete list of viruses that cause equine diseases including 36 infectious agents, 25 of which are pathogenic for humans, 13 of the 25 of which are widespread throughout Russia. Information is provided on the magnitudes of the disease incubation periods (which are most often within one month), the external clinical signs of these diseases (which can also be asymptomatic), and the maximum possible concentrations of viruses in the blood of horses with these diseases (which can reach 8 log conventional units/mL of blood). This information is offered for use in critical production stages of heterologous immunoglobulin drugs for medical use to assure viral safety.

Risk factors for duration of equine rhinitis A virus respiratory disease

BACKGROUND

Infectious respiratory disease is common in young horses and can impact athletic performance and long-term health. Significant variation in the duration of clinical disease has been observed, even in the absence of secondary complications. The determination of factors associated with disease chronicity may facilitate clinical decision-making and the development of improved biosecurity protocols.

OBJECTIVE

To investigate contact network characteristics, and demographic variables associated with time to clinical recovery from Equine Rhinitis A virus respiratory disease.

STUDY DESIGN

Prospective cohort study.

METHODS

Yearling Standardbred racehorses (n = 58) housed in a multi-barn training facility in Southern Ontario were included. Horses were monitored daily for clinical signs of acute respiratory disease over a 41-day period in Autumn 2017. Contact patterns between horses, including older racehorses, were determined through use of proximity loggers attached to halters during the initial 7-day of the study. Associations between duration of disease, demographic factors (birth month, gait, sex and yearling sale), serologic titres and network metrics (degree, betweenness and Eigenvector centrality) were investigated using a Cox proportional hazard model.

RESULTS

Yearling attack rate for infectious respiratory disease was 87.9% (n = 51). Median time to recovery was 6 days (IQR = 1-32) and 17 horses were censored due to early withdrawal or failure to recover during the study period. In those yearlings born February-May, birth month was significant in the Cox proportional hazard model (Hazard Ratio 0.7, 95% CI 0.49-1, P = 0.05).

MAIN LIMITATION

Probability of censoring was not independent of outcome which necessitated use of sensitivity analysis.

CONCLUSIONS

These findings suggest late born foals are less likely to recover quickly from infectious respiratory disease.

Equine Rhinitis A Virus Infection in Thoroughbred Racehorses-A Putative Role in Poor Performance?

The aim of this study was to identify respiratory viruses circulating amongst elite racehorses in a training yard by serological testing of serial samples and to determine their impact on health status and ability to race. A six-month longitudinal study was conducted in 30 Thoroughbred racehorses (21 two-year-olds, five three-year-olds and four four-year-olds) during the Flat racing season. Sera were tested for the presence of antibodies against equine herpesvirus 1 and 4 (EHV-1 and EHV-4) and equine rhinitis viruses A and B (ERAV and ERBV) by complement fixation (CF) and equine arteritis virus (EAV) by ELISA. Antibodies against equine influenza (EI) were measured by haemagglutination inhibition (HI). Only ERAV was circulating in the yard throughout the six-month study period. Seroconversion to ERAV frequently correlated with clinical respiratory disease and was significantly associated with subsequent failure to race (p = 0.0009). Over 55% of the two-year-olds in the study seroconverted to ERAV in May and June. In contrast, only one seroconversion to ERAV was observed in the older horses. They remained free of any signs of respiratory disease and raced successfully throughout the study period. The importance of ERAV as a contributory factor in the interruption of training programmes for young horses may be underestimated.

Equine Rhinitis A Virus Infection at a Standardbred Training Facility: Incidence, Clinical Signs, and Risk Factors for Clinical Disease

Respiratory disease is a common morbidity of young racehorses. Infections can lead to compromised welfare, and economic loss. Identification of risk factors for infection through clinical signs monitoring and collection of demographic, serologic, and contact network data can aid in the development of prevention and control strategies. The study objectives were to: (1) describe the transmission and clinical course of infectious respiratory disease in standardbred racehorses in a multi-barn training facility and, (2) identify demographic, serological, and contact network risk factors associated with Equine Rhinitis A virus (ERAV) respiratory disease. The study population included standardbred racehorses (age 1-5 years: n = 96) housed at a multi-barn training facility in southern Ontario. Clinical signs were monitored daily over a 41-day period in fall 2017. Descriptive statistics, including incidence rate, prevalence and incidence risk were calculated for the observed period. Associations between demographic, serologic, and contact pattern variables, and clinical disease status were investigated using multivariable logistic regression. Respiratory disease cases were characterized by mucopurulent discharge (100%), intermittent cough (37.7%), and ocular discharge (62.3%). Fever (>38.5°C) and inappetence were rarely reported (15.2 and 3.8%). Seroconversion to ERAV among cases was 75%. Total, and yearling-specific incidence risks were 52.5 and 87.9%. The cumulative incidence was 0.027 new cases/horse day. A negative association (OR = 0.011) between increasing age and respiratory disease was significant (p = < 0.001) in the final regression model. Yearling horses were at increased risk of infectious respiratory disease as demonstrated by the high yearling-specific incidence risk, and the negative association between age and infection. Disease control strategies, such as vaccination programs and isolation of new horses arriving from auction, should be targeted at young animals entering training facilities.

Viral, Serological, and Antioxidant Investigations of Equine Rhinitis A Virus in Serum and Nasal Swabs of Commercially Used Horses in Poland

Background

Equine rhinitis A virus (ERAV) is considered to be an important pathogen in horses, but relatively few studies are available.

Aims

The purpose of this study was to verify ERAV seroprevalence in selected horses in Poland, in addition to correlation between ERAV and age and sex of analysed animals and the antioxidant status.

Methods

The material collected from clinically healthy horses was tested using the VNT (353 serum samples) and virus isolation method (44 nasal swabs). 27 serum samples with antibody titers between 0 and ≥1 : 2048 were chosen for further analysis. The study was conducted in group 1 (ERAV titer ≤ 64) and group 2 (ERAV titer > 64).

Results

Seroneutralisation tests showed positive results in 72% of serum samples. No significant correlation between ERAV seropositive results and selected biochemical indicators was observed. Group 2 had statistically higher concentrations of SOD and CuZnSOD than the analysed group 1.

Conclusions

ERAV was not detected in the nasal swab samples. Antioxidant parameters did not significantly vary between horses of different breed, sex, or age. The ERAV virus had an impact on plasma total SOD and Cu/Zn SOD activity in horses in early stages of convalescence.

Equine rhinitis B viruses in horse fecal samples from the Middle East

Background

Among all known picornaviruses, only two species, equine rhinitis A virus and equine rhinitis B virus (ERBV) are known to infect horses, causing respiratory infections. No reports have described the detection of ERBV in fecal samples of horses and no complete genome sequences of ERBV3 are available.

Methods

We performed a molecular epidemiology study to detect ERBVs in horses from Dubai and Hong Kong. Complete genome sequencing of the ERBVs as well as viral loads and genome, phylogenetic and evolutionary analysis were performed on the positive samples.

Results

ERBV was detected in four (13.8 %) of the 29 fecal samples in horses from Dubai, with viral loads 8.28 × 10³ to 5.83 × 10⁴ copies per ml, but none of the 47 fecal samples in horses from Hong Kong by RT-PCR. Complete genome sequencing and phylogenetic analysis showed that three of the four strains were ERBV3 and one was ERBV2. The major difference between the genomes of ERBV3 and those of ERBV1 and ERBV2 lied in the amino acid sequences of their VP1 proteins. The Ka/Ks ratios of all the coding regions in the ERBV3 genomes were all <0.1, suggesting that ERBV3 were stably evolving in horses. Using the uncorrelated lognormal distributed relaxed clock model on VP1 gene, the date of the most recent common ancestor (MRCA) of ERBV3 was estimated to be 1785 (HPDs, 1176 to 1937) and the MRCA dates of ERBV1 and ERBV2 were estimated to be 1848 (HPDs, 1466 to 1949) respectively.

Conclusions

Both acid stable (ERBV3) and acid labile (ERBV2) ERBVs could be found in fecal samples of horses. Detection of ERBVs in fecal samples would have implications for their transmission and potential role in gastrointestinal diseases as well as fecal sampling as an alternative method of identifying infected horses.

Characteristics of respiratory tract disease in horses inoculated with equine rhinitis A virus

OBJECTIVE

To develop a method for experimental induction of equine rhinitis A virus (ERAV) infection in equids and to determine the clinical characteristics of such infection.

ANIMALS

8 ponies (age, 8 to 12 months) seronegative for antibodies against ERAV. PROCEDURES-Nebulization was used to administer ERAV (strain ERAV/ON/05; n = 4 ponies) or cell culture medium (control ponies; 4) into airways of ponies; 4 previously ERAV-inoculated ponies were reinoculated 1 year later. Physical examinations and pulmonary function testing were performed at various times for 21 days after ERAV or mock inoculation. Various types of samples were obtained for virus isolation, blood samples were obtained for serologic testing, and clinical scores were determined for various variables.

RESULTS

ERAV-inoculated ponies developed respiratory tract disease characterized by pyrexia, nasal discharge, adventitious lung sounds, and enlarged mandibular lymph nodes. Additionally, these animals had purulent mucus in lower airways up to the last evaluation time 21 days after inoculation (detected endoscopically). The virus was isolated from various samples obtained from lower and upper airways of ERAV-inoculated ponies up to 7 days after exposure; this time corresponded with an increase in serum titers of neutralizing antibodies against ERAV. None of the ponies developed clinical signs of disease after reinoculation 1 year later.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of this study indicated ERAV induced respiratory tract disease in seronegative ponies. However, ponies with neutralizing antibodies against ERAV did not develop clinical signs of disease when reinoculated with the virus. Therefore, immunization of ponies against ERAV could prevent respiratory tract disease attributable to that virus in such animals.

In vitro surrogate models to aid in the development of antivirals for the containment of foot-and-mouth disease outbreaks

Foot-and-mouth disease virus (FMDV) is a highly pathogenic member of the genus Aphthovirus (family Picornaviridae) that is only to be manipulated in high-containment facilities, thus complicating research on and discovery of antiviral strategies against the virus. Bovine rhinitis B virus (BRBV) and equine rhinitis A virus (ERAV), phylogenetically most closely related to FMDV, were explored as surrogates for FMDV in antiviral studies. Although no efficient cell culture system has been reported so far for BRBV, we demonstrate that infection of primary bovine kidney cells resulted in an extensive but rather poorly-reproducible induction of cytopathic effect (CPE). Madin-Darby bovine kidney cells on the other hand supported viral replication in the absence of CPE. Antiviral tests were developed for ERAV in Vero A cells employing a viral RNA-reduction assay and CPE-reduction assay; the latter having a Z' factor of 0.83±0.07. The BRBV and ERAV models were next used to assess the anti-aphthovirus activity of two broad-spectrum antiviral agents 2'-C-methylcytidine (2CMC) and ribavirin, as well as of the enterovirus-specific inhibitor enviroxime. The effects of the three compounds in the CPE-reduction (ERAV) and viral RNA-reduction assays (BRBV and ERAV) were comparable. Akin to 2CMC, compound A, a recently-discovered non-nucleoside pan-serotype FMDV inhibitor, also inhibited the replication of both BRBV and ERAV, whereas enviroxime was devoid of activity. The BRBV and ERAV surrogate models reported here can be manipulated in BSL-2 laboratories and may facilitate studies to unravel the mechanism of action of novel FMDV inhibitors.