Molecular Characterisation of Equine Herpesvirus 1 Isolates from Cases of Abortion, Respiratory and Neurological Disease in Ireland between 1990 and 2017.

Multiple locus typing based on sequencing heterologous regions in 26 open reading frames (ORFs) of equine herpesvirus 1 (EHV-1) strains Ab4 and V592 was used to characterise 272 EHV-1 isolates from 238 outbreaks of abortion, respiratory or neurological disease over a 28-year period. The analysis grouped the 272 viruses into at least 10 of the 13 unique long region (UL) clades previously recognised. Viruses from the same outbreak had identical multi-locus profiles. Sequencing of the ORF68 region of EHV-1 isolates from 222 outbreaks established a divergence into seven groups and network analysis demonstrated that Irish genotypes were not geographically restricted but clustered with viruses from all over the world. Multi-locus analysis proved a more comprehensive method of strain typing than ORF68 sequencing. It was demonstrated that when interpreted in combination with epidemiological data, this type of analysis has a potential role in tracking virus between premises and therefore in the implementation of targeted control measures. Viruses from 31 of 238 outbreaks analysed had the proposed ORF30 G2254/D752 neuropathogenic marker. There was a statistically significant association between viruses of the G2254/D752 genotype and both neurological disease and hypervirulence as defined by outbreaks involving multiple abortion or neurological cases. The association of neurological disease in those with the G2254/D752 genotype was estimated as 27 times greater than in those with the A2254/N752 genotype.

Facial hair whorls (trichoglyphs) and the incidence of motor laterality in the horse.

Several species demonstrate obvious motor laterality (sidedness, handedness) in their motor function. Motor laterality in the horse affects locomotion and subsequently equine performance during training and may have inherent safety implications for equitation. Some of the most commonly used identification features in the horse are hair whorls (trichoglyphs), since their specific location and character vary to some degree in every horse. We investigated the relationship between the hair flow of single facial hair whorls and the incidence of lateralised motor bias in 219 horses when under saddle in ridden work. The horses exhibited significant differences in motor preferences with 104 left-lateralised (LL) horses, 95 right-lateralised (RL) horses compared to only 20 well-balanced (WB) horses (chi(2)=36.9, d.f.=2, P<0.01). There was also a significant difference in the frequency distribution of single facial hair whorl patterns in the horses consisting of 114 horses with counter-clockwise (CC) whorls, 82 horses with clockwise (C) whorls and 23 horses, which had radial (R) whorls (chi(2)=38.87, d.f.=2, P<0.01). Overall there was a statistically significant association between motor behaviour and facial hair whorl patterns in the horses (chi(2)=69.4, d.f.=4, P>0.001). The RL horses had significantly more C facial hair whorls and the LL horses had significantly more CC facial hair whorls than would be expected purely by chance alone (P<0.05). The findings may provide trainers with a useful tool when attempting to identify simple, non-invasive and reliable predictors of motor laterality in the horse. Furthermore, given that efficient targeted training of performance horses during ridden work may produce WB equine athletes, the findings could assist trainers when designing individual-specific training programmes for young horses.

Equid herpesvirus 8: Complete genome sequence and association with abortion in mares.

Equid herpesvirus 8 (EHV-8), formerly known as asinine herpesvirus 3, is an alphaherpesvirus that is closely related to equid herpesviruses 1 and 9 (EHV-1 and EHV-9). The pathogenesis of EHV-8 is relatively little studied and to date has only been associated with respiratory disease in donkeys in Australia and horses in China. A single EHV-8 genome sequence has been generated for strain Wh in China, but is apparently incomplete and contains frameshifts in two genes. In this study, the complete genome sequences of four EHV-8 strains isolated in Ireland between 2003 and 2015 were determined by Illumina sequencing. Two of these strains were isolated from cases of abortion in horses, and were misdiagnosed initially as EHV-1, and two were isolated from donkeys, one with neurological disease. The four genome sequences are very similar to each other, exhibiting greater than 98.4% nucleotide identity, and their phylogenetic clustering together demonstrated that genomic diversity is not dependent on the host. Comparative genomic analysis revealed 24 of the 76 predicted protein sequences are completely conserved among the Irish EHV-8 strains. Evolutionary comparisons indicate that EHV-8 is phylogenetically closer to EHV-9 than it is to EHV-1. In summary, the first complete genome sequences of EHV-8 isolates from two host species over a twelve year period are reported. The current study suggests that EHV-8 can cause abortion in horses. The potential threat of EHV-8 to the horse industry and the possibility that donkeys may act as reservoirs of infection warrant further investigation.

Equine learning behaviour.

Scientists and equestrians continually seek to achieve a clearer understanding of equine learning behaviour and its implications for training. Behavioural and learning processes in the horse are likely to influence not only equine athletic success but also the usefulness of the horse as a domesticated species. However given the status and commercial importance of the animal, equine learning behaviour has received only limited investigation. Indeed most experimental studies on equine cognitive function to date have addressed behaviour, learning and conceptualization processes at a moderately basic cognitive level compared to studies in other species. It is however, likely that the horses with the greatest ability to learn and form/understand concepts are those, which are better equipped to succeed in terms of the human-horse relationship and the contemporary training environment. Within equitation generally, interpretation of the behavioural processes and training of the desired responses in the horse are normally attempted using negative reinforcement strategies. On the other hand, experimental designs to actually induce and/or measure equine learning rely almost exclusively on primary positive reinforcement regimes. Employing two such different approaches may complicate interpretation and lead to difficulties in identifying problematic or undesirable behaviours in the horse. The visual system provides the horse with direct access to immediate environmental stimuli that affect behaviour but vision in the horse is of yet not fully investigated or understood. Further investigations of the equine visual system will benefit our understanding of equine perception, cognitive function and the subsequent link with learning and training. More detailed comparative investigations of feral or free-ranging and domestic horses may provide useful evidence of attention, stress and motivational issues affecting behavioural and learning processes in the horse. The challenge for scientists is, as always, to design and commission experiments that will investigate and provide insight into these processes in a manner that withstands scientific scrutiny.

Noseband Use in Equestrian Sports - An International Study.

Nosebands are used by riders to prevent the horse from opening its mouth, to increase control and, in some cases, to comply with the competition rules. While equestrian texts traditionally recommend that two adult human fingers should be able to fit under a fastened noseband, noseband tightness levels are not, in general, regulated in competition. Possible detrimental consequences for the horse, of excessively tight nosebands, include discomfort, pain or tissue damage. The current study investigated noseband usage in equestrian competition. Data regarding noseband type, position, width and tightness were collected from 750 horses in eventing (n = 354), dressage (n = 334) and performance hunter (n = 62) competitions in Ireland, England and Belgium. Data were collected immediately before or after the performance. Using the ISES taper gauge as a guide, results were classified according to the number of 'fingers' that could fit under the noseband at the nasal planum, and assigned to six groups: greater than 2 fingers; 2 fingers; 1.5 fingers; 1 finger; 0.5 fingers; zero fingers. A calliper was used to measure noseband width and position relative to the facial crest. The data were not normally distributed so Kruskall-Wallis and Mann-Whitney tests were used. In all, 44% of horses fell into the zero fingers classification while only 7% were in the two fingers classification. Significant differences emerged between disciplines (p<0.001), with the highest levels of noseband tightness measured among eventers followed by dressage horses with lowest levels among performance hunters. Noseband tightness did not differ significantly with horse age (p>0.05), which ranged from 4 to 19 years. The flash noseband was the most commonly used noseband (n = 326) and was significantly tighter than the cavesson (p < 0.001), drop noseband (p < 0.001) and the Micklem (p < 0.005). Noseband width ranged from 10 to 50 mm. Noseband position varied widely with the distance between the facial crest and upper noseband margin ranging from 0 to 70 mm. The high proportion of very tight nosebands found in this study raises concerns regarding the short and long term behavioural and physiological consequences of such tight nosebands are for the horse. Although these data are currently lacking, the findings are of concern.

Genetic typing of bovine viral diarrhoea virus in cattle on Irish farms.

The aim was to carry out a phylogenetic study of bovine viral diarrhoea viruses (BVDV) circulating in Irish cattle herds from 2011 to 2014. Three hundred and twenty five viruses from 267 herds were subtyped by nucleotide sequence analysis of the 5'UTR and/or the Npro regions. All viruses investigated in this study belonged to species BVDV-1 with BVDV-1a as the prominent subtype (97%). Subtypes BVDV-1b, BVDV-1d and BVDV-1e were also identified for the first time in Ireland. Pairwise alignments of 225 viruses with complete sequences for the 5'UTR and the Npro regions were performed to determine a low conflict threshold for virus strain demarcation. One hundred and seventy seven unique virus strains were identified. The study revealed significant levels of herd specific clustering of strains but no geographical or temporal clustering. Similar virus strains were identified in different counties, provinces and years indicating the potential to investigate the epidemiology of the disease by combining sequence analysis with animal movement data.

Impact of three inactivated bovine viral diarrhoea virus vaccines on bulk milk p80 (NS3) ELISA test results in dairy herds.

Bovine viral diarrhoea virus (BVDV) is endemic in many countries and vaccines are used as a component of control and eradication strategies. Surveillance programmes to detect exposure to BVDV often incorporate the use of bulk milk (BM) testing for antibodies against BVDV p80 (NS3), but vaccination can interfere with these results. The aim of this study was to evaluate whether BVDV vaccines would confound BM testing for specific antibodies in a nationally representative group of commercial dairy farms in the Republic of Ireland. A total of 256 commercial dairy herds were included in the statistical analysis. Quarterly BM or serum samples from selected weanling heifers (unvaccinated homeborn youngstock) were assessed by ELISA for antibodies against the BVDV p80 subunit and whole virus. Wilcoxon rank-sum and receiver operating characteristic (ROC) analyses were used to examine differences among groups vaccinated with one of three commercially available inactivated BVDV vaccines. Two of the three vaccines showed evidence of interference with ELISA testing of BM samples. ROC analysis highlighted that one vaccine did not reduce the discriminatory power of the BVDV p80 ELISA for identification of herds with evidence of recent BVDV circulation, when compared with unvaccinated herds; thus, administration of this vaccine would allow uncomplicated interpretation of BM ELISA test results in vaccinated seropositive herds. Seasonal differences in BM antibody results were identified, suggesting that the latter half of lactation is the most suitable time for sampling dairy herds containing predominantly spring calving cows. The results of the present study are likely to prove useful in countries allowing vaccination during or following BVDV eradication, where BM testing is required as part of the surveillance strategy.

Age-associated loss of bone marrow hematopoietic cells is reversed by GH and accompanies thymic reconstitution.

Deterioration of the thymus gland during aging is accompanied by a reduction in plasma GH. Here we report gross and microscopic results from 24-month-old Wistar-Furth rats treated with rat GH derived from syngeneic GH3 cells or with recombinant human GH. Histological evaluation of aged rats treated with either rat or human GH displayed clear morphologic evidence of thymic regeneration, reconstitution of hematopoietic cells in the bone marrow, and multiorgan extramedullary hematopoiesis. Quantitative evaluation of formalin-fixed, hematoxylin and eosin-stained sections of bone marrow from aged rats revealed at least a 50% reduction in the number hematopoietic bone marrow cells, compared with that of young 3-month-old rats. This age-associated decline in bone marrow leukocytes, as well as the increase in bone marrow adipocytes, was significantly reversed by in vivo treatment with GH. Restoration of bone marrow cellularity was caused primarily by erythrocytic and granulocytic cells, but all cell lineages were represented and their proportions were similar to those in aged control rats. On a per-cell basis, GH treatment in vivo significantly increased the number of in vitro myeloid colony forming units in both bone marrow and spleen. Morphological evidence of enhanced extramedullary hematopoiesis was observed in the spleen, liver, and adrenal glands from animals treated with GH. These results confirm that GH prevents thymic aging. Furthermore, these data significantly extend earlier findings by establishing that GH dramatically promotes reconstitution of another primary hematopoietic tissue by reversing the accumulation of bone marrow adipocytes and by restoring the number of bone marrow myeloid cells of both the erythrocytic and granulocytic lineages.

The evaluation of three diagnostic tests for the detection of equine influenza nucleoprotein in nasal swabs.

BACKGROUND: Equine influenza (EI) is a highly contagious respiratory disease of horses. OBJECTIVES: The aim of this study was to evaluate two rapid antigen detection kits (Directigen or DFA, and Espline) and a commercial ELISA for the detection of EI nucleoprotein in nasal swabs. METHOD: Nasal swab samples from naturally and experimentally infected horses were used to compare the sensitivity and specificity of these assays to virus isolation (VI) and real-time RT-PCR. RESULTS: If real-time RT-PCR was considered as the gold standard, the sensitivity of the other tests in field samples was 68% (DFA), 35% (ELISA), 29% (Espline), and 9% (VI). These tests had 100% specificity when compared to real-time RT-PCR. A receiver operating characteristic (ROC) curve indicated that decreasing the cutoff of the ELISA would increase sensitivity with some loss of specificity. In samples from experimentally infected horses, the sensitivity of the tests compared with real-time RT-PCR was 69% (VI), 27% (DFA), 6% (Espline), and 2% (ELISA). The specificity was 100% for Espline and ELISA and 95% for VI and DFA. CONCLUSIONS: This study illustrated that DFA is the most sensitive antigen detection test evaluated for the diagnosis of EI and that it can detect virus in some subclinical infected and vaccinated horses. The results suggest that DFA is a useful adjunct to laboratory tests and may be effective as a screening test in a quarantine station or similar facility where horses are monitored daily.

The evaluation of a nucleoprotein ELISA for the detection of equine influenza antibodies and the differentiation of infected from vaccinated horses (DIVA).

BACKGROUND: Antibodies against equine influenza virus (EIV) are traditionally quantified by haemagglutination inhibition (HI) or single radial haemolysis (SRH). OBJECTIVES: To evaluate an ELISA for the detection of antibodies against influenza nucleoprotein in the diagnosis and surveillance of equine influenza (EI). METHODS: The ELISA was compared with the SRH and HI tests. Serial serum samples from 203 naturally and 14 experimentally infected horses, from 60 weanlings following primary vaccination with five different vaccines (two whole inactivated vaccines, two ISCOM-based subunit vaccines and a recombinant canarypox virus vaccine) and from 44 adult horses following annual booster vaccination with six different vaccines were analysed. RESULTS: Fewer seroconversions were detected in clinical samples by ELISA than by SRH or HI but ELISA was more sensitive than SRH in naïve foals post-experimental infection. The ELISA did not detect the antibody response to vaccination with the recombinant canarypox virus vaccine confirming the usefulness of the combination of this kit and vaccine to differentiate between naturally infected and vaccinated horses, that is, DIVA. No DIVA capacity was evident with the other vaccines. CONCLUSION: The results suggest that this ELISA is a useful supplementary test for the diagnosis of EI although less sensitive than HI or SRH. It is an appropriate test for EI surveillance in a naïve population and may be combined with the recombinant canarypox virus vaccine but not with other commercially available subunit vaccines, in a DIVA strategy.

A comparison of antibody responses to commercial equine influenza vaccines following primary vaccination of Thoroughbred weanlings--a randomised blind study.

Many racing authorities, sales companies and equestrian bodies have mandatory vaccination policies for equine influenza (EI). The consequences of lack of vaccine efficacy include clinical disease, disruption to training programmes, the cancellation of equestrian events and the introduction of virus to susceptible populations. The correlation between antibody against the virus haemagglutinin and protection against influenza has been well established. The objective of this study was to compare the antibody responses of 66 unvaccinated Thoroughbred weanlings on four different stud farms, following primary vaccination (V1, V2 and V3) with the five EI vaccines commercially available in Ireland (Duvaxyn IET Plus, Equilis Resequin, Equip FT, Equilis Prequenza Te, ProteqFlu Te). Antibody responses were monitored for 6 months post V3 by single radial haemolysis. The pattern of antibody response was similar for all vaccines and for all antigens tested. A rapid decline of antibody level was observed by 3 months post V2 for all vaccines. The antibody response of the horses vaccinated with the whole virus vaccine Duvaxyn IET Plus was significantly higher than that of the horses vaccinated with the other four products. Five weanlings had maternally derived antibodies (MDA) at the time of V1. The canary pox recombinant vaccine, subunit vaccine and whole virus inactivated vaccines administered to these weanlings did not induce a detectable antibody response against the background of MDA but effectively primed the animals as revaccination resulted in a strong antibody response. In this study 43% of the weanlings failed to seroconvert after V1. This high incidence of poor responders has not been reported in previous experimental studies relating to these products. The poor responders were observed in all vaccine groups except those vaccinated with Duvaxyn IET Plus. Post V2 the incidence of poor responders was reduced to 7% and all horses responded to V3. The study demonstrates that independent evaluation of influenza vaccine performance in the field is critical to add to the body of knowledge gained from experimental challenge experiments carried out for regulatory or marketing purposes.

A comparison of antibody responses to commercial equine influenza vaccines following annual booster vaccination of National Hunt horses - a randomised blind study.

Protection against equine influenza virus (EIV) relies largely on the production of circulating antibodies specific for the haemagglutinin (HA) glycoprotein. The objective of this study was to determine the antibody response of National Hunt horses in training to booster vaccination. The antibody response to the six equine influenza vaccines available in Ireland (three whole inactivated vaccines, two subunit vaccines and a canary pox recombinant vaccine), was monitored by single radial haemolysis (SRH) for six months post vaccination. There was no significant difference between antibody response induced following booster vaccination with any of the six vaccines. The antibodies peaked between two and four weeks post vaccination, decreased significantly by three months post vaccination and declined to their original levels by six months post vaccination. Peak antibody response to the canary pox recombinant vaccine was delayed in comparison to the other vaccines. Although analysis of the mean SRH levels of the horses suggested that they were clinically protected post booster vaccination, analysis of the individual responses suggested that there was potential for vaccination breakdown in a manner similar to that observed previously in racing yards in Ireland. There was a significant correlation between the SRH level at the time of vaccination and the antibody response. The findings of the study suggest that it would be advantageous to monitor SRH levels and to vaccinate strategically. The revaccination of horses with low antibody levels three months post booster vaccination may have been more effective in protecting horses in this yard than the annual vaccination of horses with high SRH levels. Eighteen of the 44 (41%) horses included in this study did not demonstrate a significant rise in SRH level to H3N8 following booster vaccination. It is presumed that annual revaccination is the minimum necessary to protect all horses against EI but this assumption needs to be systematically evaluated. It has been demonstrated that shorter intervals are required for optimum protection of young horses and it may be that longer vaccination intervals are sufficient for older horses with several years of vaccination history. Further investigations in a larger population of horses will be necessary to determine if the findings of this study are applicable to the population at large.

A comparative antibody study of the potential susceptibility of Thoroughbred and non-Thoroughbred horse populations in Ireland to equine influenza virus.

BACKGROUND: In Ireland, horses may be protected against equine influenza virus (EIV) as a result of natural exposure or vaccination. Current mandatory vaccination programmes are targeted at highly mobile horses. A correlation between antibody levels as measured by single radial haemolysis (SRH) and protective immunity against EIV has been established. OBJECTIVES: The objective of this study was to determine the susceptibility of selected populations of horses by quantifying their antibodies to EIV. METHODS: Blood samples were collected from Thoroughbred weanlings, yearlings, racehorses and broodmares, teaser stallions and non-Thoroughbred horses. Antibodies against EIV H3N8 and H7N7 were measured by SRH. RESULTS: The order of susceptibility to Equine Influenza (EI) in the populations examined in Ireland was as follows: Thoroughbred weanlings > teasers > non-Thoroughbred horses and ponies > Thoroughbred yearlings > Thoroughbred horses in training > Thoroughbred broodmares. The H3N8 antibody levels of the weanlings, yearlings, broodmares and horses in training were similar to their H7N7 antibody levels, suggesting that their antibodies were primarily vaccinal in origin. The teasers and non-Thoroughbreds had higher H3N8 antibody levels than H7N7 antibody levels, suggesting that the majority of seropositive horses in these populations had been exposed to H3N8 by natural infection. CONCLUSIONS: Weanlings, teasers and non-Thoroughbred horses were identified as most susceptible to EIV. The results suggest that it would be advisable that weanlings are vaccinated prior to attendance at public sales, that teaser stallions are vaccinated prior to each breeding season and that mandatory vaccination be implemented for participation in non-Thoroughbred events.

Intramammary infusion of a live culture for treatment of bovine mastitis: effect of live lactococci on the mammary immune response.

In the accompanying article, we demonstrated that a live culture of Lactococcus lactis compares favourably with antibiotics for treatment of bovine mastitis in two initial field trials. In an effort to explain the mechanism involved, this study investigated the effect of culture administration on the local immune response. In this respect we initially observed that infusion of the live culture Lactococcus lactis stimulated substantial recruitment of polymorphonucleocytes (PMN) and lymphocytes to the udder. For instance, in one assay, quarters infused with the probiotic experienced a dramatic increase (approximately 20,000-fold) in neutrophils over the first 48-h period from an average value of 83.6 cells/ml pre-treatment to 1.78 x 106 cells/ml 48 h post-infusion. Levels of the acute phase proteins haptaglobin and milk amyloid A were also elevated significantly in comparison with controls following infusion of the culture. The results of flow cytometric assays also demonstrated that while infusion of a live lactococcal culture led to an enhanced recruitment of PMN to the udder (from 1.85 x 104 cells/ml pre-infusion to 1.45 x 106 cells/ml 24 h post-infusion) cell-free supernatant from the same culture was not able to do so, indicating that live Lc. lactis can specifically trigger the mammary immune response to elicit PMN accumulation. These results suggest that the mechanism responsible for this probiotic treatment of mastitis is associated with stimulation of the host intramammary immune system.

Pro-inflammatory and antiviral cytokine expression in vaccinated and unvaccinated horses exposed to equine influenza virus.

Most studies of the cytokine response to influenza virus infection have been carried out in human, porcine and murine models, however the data available on equine cytokines is limited. An experimental challenge study was undertaken in unvaccinated naïve horses and horses vaccinated with a commercial inactivated influenza vaccine. The humoral antibody response to vaccination and virus challenge was measured by single radial haemolysis (SRH) assay and clinical signs of influenza and viral shedding were monitored post-challenge. Levels of three equine pro-inflammatory cytokines interleukin (IL)-1beta, IL-6 and tumor necrosis factor (TNF)-alpha and the antiviral cytokine interferon (IFN)-alpha were examined by quantitative RT-PCR of mRNA. Vaccination provided significant clinical and virological protection and resulted in a significant reduction of IFN-alpha and IL-6 expression on day 2 post-challenge. The patterns of cytokine expression observed in control animals suffering from influenza after challenge are comparable to those reported in studies of other species.

Real-time reverse transcription PCR for detection and quantitative analysis of equine influenza virus.

Equine influenza is a cause of epizootic respiratory disease of the equine. The detection of equine influenza virus using real-time Light Cycler reverse transcription (RT)-PCR technology was evaluated over two influenza seasons with the analysis of 171 samples submitted for viral respiratory disease. Increased sensitivity was found in overall viral detection with this system compared to Directigen Flu A and virus isolation, which were 40% and 23%, respectively, that of the RT-PCR. The assay was also evaluated as a viable replacement for the more traditional methods of quantifying equine influenza virus, 50% egg infectious dose and 50% tissue culture infectious dose. There was a significant positive correlation (P<0.05) between the quantitative RT-PCR and both of these assays.

Comparison of sensitivities of virus isolation, antigen detection, and nucleic acid amplification for detection of equine influenza virus.

Four seronegative foals aged 6 to 7 months were exposed to an aerosol of influenza strain A/Equi/2/Kildare/89 at 10(6) 50% egg infective doses (EID(50))/ml. Nasopharyngeal swabs were collected for 10 consecutive days after challenge. Virus isolation was performed in embryonated eggs, and the EID(50) was determined for all positive samples. The 50% tissue culture infective dose was determined using Madin-Darby canine kidney (MDCK) cells. Samples were also tested by an in vitro enzyme immunoassay test, Directigen Flu A, and by reverse transcription-PCR (RT-PCR) using nested primers from the nucleoprotein gene and a single set of primers from the matrix gene. RT-PCR using the matrix primers and virus isolation in embryonated eggs proved to be the most sensitive methods for the detection of virus. The Directigen Flu A test was the least sensitive method. The inclusion of 2% fetal calf serum in the viral transport medium inhibited the growth of virus from undiluted samples in MDCK cells but was essential for the maintenance of the virus titer in samples subjected to repeated freeze-thaw cycles.