Guillaume Fortier

Sub-clinical diseases affecting performance in Standardbred trotters: diagnostic methods and predictive parameters.

The objectives of this study were to determine the prevalence of sub-clinical diseases in poorly-performing Standardbred horses, compare their physiological response to exercise with control horses, and identify predictive parameters of poor-performance. Fifty horses underwent thorough clinical and ancillary examinations, including haematological and biochemical evaluation, Doppler echocardiography, standardised exercise tests (SETs) on both treadmill and racetrack, treadmill video-endoscopy and collection of respiratory fluids. Most of the poorly-performing horses exhibited many concomitant diseases. The most frequently diagnosed problems involved the lower and upper respiratory tract and the musculoskeletal system. Poor-performers had lower speeds at a blood lactate (LA) concentration of 4mmol/L (V(LA4)) and a heart rate (HR) of 200bpm (V(200)) on treadmill and racetrack, as well as lower values for haematological parameters, plasma angiotensin-converting enzyme and antioxidants, compared to control horses. Problems of the respiratory system were the most frequently diagnosed sub-clinical diseases affecting performance. SETs, together with some blood markers, may be useful as a non-specific diagnostic tool for early detection of diseases that may affect performance.

Equine gammaherpesviruses: pathogenesis, epidemiology and diagnosis.

Equine gammaherpesviruses (γEHV) have been widely studied over the past 45 years and many isolates have been characterised. Despite this, the diagnosis of γEHV infection remains difficult to establish as its clinical manifestations lack specificity, ranging from mild respiratory signs in a small number of animals to outbreaks in large groups of young horses. This review focuses on the epidemiology, pathogenesis, clinical manifestations and diagnosis of equine herpesvirus (EHV)-2 and -5 infections, as well as on the genetic variation of these viruses. Study of these variations has resulted in hypotheses relating to viral re-infection and re-activation. Interestingly, the viruses were found to contain genetic sequences identical to those of eukaryotic cells which are considered central to the development of viral latency through interfering with host immune and inflammatory responses. Future molecular biological studies will further elucidate the virulence mechanisms of these equine pathogens.

Identification of pathogenic Leptospira strains in tissues of a premature foal by use of polymerase chain reaction analysis

Studies were carried out to determine the cause of death in a prematurely born Thoroughbred foal that died 24 hours after birth. Necropsy revealed gross lesions suggestive of septicemia. A commercial Leptospira polymerase chain reaction (PCR) assay designed to specifically amplify the hemolysis-associated protein 1 (hap1) gene present only in pathogenic Leptospira strains detected the presence of Leptospira DNA in various tissues of the foal. Histologic examination of lung, liver, kidney, and myocardium revealed numerous spirochetes in Warthin–Starry-stained tissue sections. Results of PCR analysis and histologic examination suggested a leptospiral infection in the newborn foal. At the moment of death, the infection coexisted with a streptococcal-associated aspiration bronchopneumonia and postpartum septicemia. These findings indicate that the PCR assay based on the amplification of the hap1 gene represents a useful tool for specific detection of pathogenic leptospira in field samples taken from horses.

Laboratory findings in respiratory fluids of the poorly-performing horse

Any disorder impairing a performance horses ability to ventilate its lungs and exchange oxygen compromises exercise performance in any discipline. Since bronchoalveolar lavage was described in horses in the early 1980s, laboratory evaluation of respiratory fluids, along with clinical and functional assessment of the respiratory system, has become a relevant step in the diagnosis of respiratory disease affecting performance. The aim of this review is to provide objective information to assist clinicians in interpreting laboratory findings by (1) summarising published cytological references values in both clinically healthy horses and those with various airway diseases, (2) assessing the influence of physiological circumstances, such as exercise, on the cytological evaluation, (3) discussing the relationship between cytological and microbiological analyses, clinical signs and respiratory function, and (4) suggesting how this latter relationship may affect performance.

Herpesviruses in respiratory liquids of horses: Putative implication in airway inflammation and association with cytological features

The objectives of this study were to estimate the prevalence and the potential role of equine herpesviruses (EHVs) detection in both bronchoalveolar lavage (BAL) and tracheal wash (TW). The population included a control group (CTL; 37 TW and 25 BAL) and a pathological group (PAT; 259 TW and 387 BAL), including horses either suffering from respiratory diseases including syndrome of tracheal inflammation, inflammatory airway disease, recurrent airway obstruction, or submitted to respiratory investigation because of exercise intolerance or poor performance. Each respiratory liquid was submitted to a standardised cytological analysis, mentioning the morphological abnormalities of exfoliated epithelial cells (ECAb) and ciliocytophthoria (CCPh) as markers of potential viral infection, as well as PCR assays including a consensus PCR and virus-specific PCR for both equine alphaherpesviruses (EHV-1; EHV-4) and gammaherpesviruses (EHV-2; EHV-5). The EHV infections were more prevalent in the TW of PAT group (P=0.004), with the highest prevalence being for EHV-2 (P=0.006). The EHV detection in BALs was not significantly different between groups. The EHVs detection in TW was correlated to the polymorphonuclear neutrophil (PMN) counts in the respiratory liquid but not with CCPh or ECAb. CCPh or ECAb were associated with both consensus PCR and EHV-2 and EHV-5 virus-type PCR in the BAL only. The significant detection of EHVs in the TW of PAT group in association with the PMN increased counts could lead to further investigations about their putative role in equine syndrome of tracheal inflammation.

Influence of subclinical inflammatory airway disease on equine respiratory function evaluated by impulse oscillometry

REASONS FOR PERFORMING STUDY Inflammatory airway disease (IAD) is a nonseptic condition of the lower respiratory tract. Its negative impact on respiratory function has previously been described using either forced expiration or forced oscillations techniques. However, sedation or drug-induced bronchoconstriction were usually required. The impulse oscillometry system (IOS) is a noninvasive and sensitive respiratory function test validated in horses, which could be useful to evaluate IAD-affected horses without further procedures. OBJECTIVES To determine the sensitivity of IOS in detecting alterations of the respiratory function in subclinically IAD-affected horses without inducing bronchoprovocation and to characterise their respiratory impedance according to frequency for each respiratory phase. METHODS Pulmonary function was evaluated at rest by IOS in 34 Standardbred trotters. According to the cytology of bronchoalveolar lavage fluid (BALF), 19 horses were defined as IAD-affected and 15 horses were used as control (CTL). Total respiratory resistance (Rrs) and reactance (Xrs) from 1-20 Hz as well as their inspiratory and expiratory components were compared between groups. RESULTS A significant increase of Rrs at the lower frequencies (R1-10 Hz) as well as a significant decrease of Xrs beyond 5 Hz (X5-20 Hz) was observed in IAD compared to CTL horses. IOS-data was also significantly different between inspiration and expiration in IAD-affected horses. In the whole population, both BALF eosinophil and mast cell counts were significantly correlated with IOS measurements. CONCLUSIONS Functional respiratory impairment may be measured, even in the absence of clinical signs of disease. In IAD-affected horses, the different parameters of respiratory function (Rrs or Xrs) may vary depending on the inflammatory cell profiles represented in BALF. POTENTIAL RELEVANCE Impulse oscillometry could be used in a routine clinical setting as a noninvasive method for early detection of subclinical respiratory disease and of the results of treatment in horses.

Neosporosis in bovine dairy herds from the west of France: detection of Neospora caninum DNA in aborted fetuses, seroepidemiology of N. caninum in cattle and dogs.

Neospora caninum is considered one of the major causes of abortion in cattle in most parts of the world. In this study, the role of N. caninum was investigated in groups of aborted cattle and dairy herds from the west of France. Good correlation was found between parasite DNA detection in fetuses and serologic statuses of dams. In groups with documented abortion status and no antibodies to other pathogens, 17-45% of aborted animals were seropositive for N. caninum, and significant relationship between prevalence of Neospora antibodies and frequency of abortions was found. Neospora-associated abortions were observed all the year round, with a peak in summer. Higher ratios of seropositive abortions were found before the 6th month of gestation. In 12 herds studied in the field, serologic prevalence ranged 6-47%. No difference in age was found between seropositive and seronegative cows. Results indicate that N. caninum is an important and stable cause of abortion in cattle in France.

Neuropathogenic and non-neuropathogenic variants of equine herpesvirus 1 in France

Equine herpesvirus 1 (EHV-1) is a common pathogen of the horse which may induce mild respiratory distress, abortion, neonatal death and neurological disease. A single nucleotide polymorphism in the EHV-1 DNA polymerase (ORF30 A(2254) to G(2254)) has been associated with clinical signs of Equine herpes myeloencephalopathy (EHM). The aim of this work was to analyze the ORF30 genomic region among a panel of EHV-1 DNA extract in order to estimate the prevalence of the EHV-1 neuropathogenic genotype in France. Samples coming from cases associated with EHM, horses with respiratory symptoms and aborted mares, each obtained between 2002 and 2009, were investigated. DNA was directly extracted from biological samples and allelic discrimination was performed using real-time PCR. Thirty of the 125 analysed horses (24%) presented the G(2254) genotype of ORF 30. Among them, 7/16 were provided by EHM cases, 1/24 by respiratory cases and 22/85 by abortion cases. Concerning EHM, the 7 G(2254) genotype of ORF30 were all isolated in 2009 during two outbreaks where mortality was observed. Regarding the 22 G(2254) genotype of ORF 30, 17 were identified in foetuses on which EHV-1 was detected by PCR, without any certainty of viral implication in the abortion. These findings clearly suggest that other factors need to be considered for a better understanding of the impact of DNA polymerase genotype upon EHV-1 neuropathogenic phenotype.

Identification of equid herpesvirus-5 in respiratory liquids: A retrospective study of 785 samples taken in 2006–2007

During a case control study undertaken in 2006-2007, a screening and consensus polymerase chain reaction (PCR) was performed to evaluate the potential role of equid herpesviruses (EHV) in several occurrences of respiratory disorders in 661 horses. Of 785 bronchoalveolar or tracheal lavage fluid samples submitted for analysis, 20 were positive for EHV-5 DNA by sequential analysis of the consensus PCR product. Nineteen of those samples were confirmed using a specific EHV-5 PCR. No particular changes in cytological profile could be associated with the detection of EHV-5 in contrast to suggestions in previous reports of natural or experimental respiratory viral infections in horses or ponies. This is the first description of EHV-5 isolation in equine respiratory fluids in Europe, but further investigations are needed to determine the potential pathogenic role of this gammaherpesvirus in the horse.

Multilocus Sequence Analysis for Typing Leptospira interrogans and Leptospira kirschneri

ABSTRACT Fifty-three strains belonging to the pathogenic species Leptospira interrogans and Leptospira kirschneri were analyzed by multilocus sequence analysis. The species formed two distinct branches. In the L. interrogans branch, the phylogenetic tree clustered the strains into three subgroups. Genogroups and serogroups were superimposed but not strictly.