Foal Mortality Research Articles

The complete genome of equid herpesvirus-1 (EHV-1) field isolates from Argentina reveals an interspecific recombinant strain.

The Equid alphaherpesvirus type 1 (EHV-1) infection can have devastating economic consequences in the horse industry due to large-scale outbreaks of abortions, perinatal foal mortality, and myeloencephalopathy. The present study analyzed the genome of two isolates obtained from aborted fetuses in Argentina, E/745/99 and E/1297/07. The E745/99 genome shares 98.2% sequence identity with Ab4, a reference EHV-1 strain. The E/1297/07 genome shares 99.8% identity with NY03, a recombinant strain containing part of ORF64 and part of the intergenic region from Equid alphaherpesvirus-4 (EHV-4). The E/1297/07 genome has the same breakpoints as other United States and Japanese recombinants, including NY03. The recombinant regions have varying numbers of tandem repeat sequences and different minor parental sequences (EHV-4), suggesting distinct origins of the recombinant events. These are the first complete genomes of EHV-1 from Argentina and South America available in the Databases.

Reduction in growth rates of wild horse populations treated with the controlled-release immunocontraceptive PZP-22 in the western United States

Context Management of wild horses (Equus caballus) on public lands in the western United States by gathering and removing surplus animals has historically failed to keep up with annual population growth. Research has yielded several effective contraceptive agents but these agents have not been widely applied, especially on difficult-to-access horses occupying expansive ranges. Aims This study examined wild horse population growth reduction associated with controlled-release PZP-22 immunocontraceptive vaccine treatments in two challenging herd management areas (HMA) in the western United States. Methods Populations of wild horse herds at Cedar Mountain HMA, Utah (CM), and Sand Wash Basin HMA, Colorado (SWB), USA, were primed with PZP-22 in gathers conducted in 2008 and 2012 (CM only) and boosted with PZP-22 or native PZP administered by dart (SWB in 2010) or by hand (CM in 2012). The two herds were intensively observed between 2008 and 2015. Population size, mortality, reproductive rates and growth rates were calculated from exhaustive inventories of known individuals. Key results Adult and foal mortality were low at both sites. Consequently, both reproductive rates and population growth rates were strongly predicted by a fertility control index, the product of proportion of mares treated and vaccine efficacy. Following the 2012 CM gather, at which 69% of the mares present were treated, only 20% of mares in the herd foaled, and population growth rate decreased by 74% relative to baseline levels, emphasising the importance of treating a large majority of mares. Conclusions Contraception can significantly reduce rates of population growth in wild horse herds that occupy large areas and are challenging to access. Multiple-year efforts and recruitment of new mares into the treatment population beyond the initial application are needed to achieve a biologically significant impact. Implications The strong quantitative relationship between proportion of mares treated and vaccine efficacy and population growth rates should allow managers to better forecast the effort and number of removals (if any) needed to cost-effectively regulate wild horse population numbers and protect the range ecosystem.

Using On-Farm Monitoring of Ergovaline and Tall Fescue Composition for Horse Pasture Management.

Central Kentucky horse pastures contain significant populations of tall fescue (Schedonorus arundinacea (Schreb.) Dumort) infected with an endophyte (Epichloë coenophialum (Morgan-Jones and Gams) Bacon and Schardl) known to produce several ergot alkaloids, with ergovaline in the highest concentration. While most classes of horses are not adversely affected by average levels of ergovaline in pastures, late term pregnant mares have a low tolerance to ergovaline and the related ergot alkaloids. Endophyte-infected tall fescue has been known to cause prolonged gestation, thickened placenta, dystocia, agalactia, and foal and mare mortality. The University of Kentucky Horse Pasture Evaluation Program utilizes ergovaline and endophyte testing, as well as pasture species composition, to calculate ergovaline in the total diet in broodmare pastures. This data is used to develop detailed management recommendations for individual pastures. Application of these recommendations has led to reduced tall fescue toxicity symptoms on these farms, as well as improved pasture management and improved forage quality and quantity.

Selenium and Vitamin E Concentrations in Miranda Jennies and Foals (Equus asinus) in Northeast Portugal

Simple SummaryDespite the importance of donkeys through history and their productive resuscitation during the last decades, reference values for common elements are not yet readily available. Such a challenge becomes even more noticeable when practitioners aim at evaluating the physiological and pathological concentrations of certain elements across the different stages that a donkey can go through along its life. The aims of this study are to determine baseline selenium and vitamin E concentrations for Miranda donkeys both jennies and foals. Miranda donkeys are considered to be endangered and it is possible that selenium and vitamin E may be associated with foal survival. Critical points may be identified related to overdosing or deficient levels of selenium and vitamin E, at different stages of development of gestation in utero during fetal development, parturition, and post foaling. Our study suggests that vitamin E and Se levels can have a major impact and effect on foal health and mortality levels. Multiple factors including location, diet, management practices, parity and time of breeding, and age of jenny may affect blood profiles in jennies, which ultimately may affect the profiles of her foals. The increase in donkeys treated by practitioners in recent years has led to an increased interest in finding more information on basic biochemical preliminary reference values. The aims of this study were to measure Se and Vit E levels in plasma from Miranda jennies peripartum and postpartum and in their foals to compare blood profiles of the jenny and foal related to the overall foal’s health. Twenty-two healthy peripartum and postpartum Miranda donkeys were sampled (12 jennies and 10 foals) in the northeast of Portugal (Atenor and Paradela) from May to November, 2018. Amounts of selenium in soil were significantly correlated (0.97) to concentrations of selenium in jennies (42.412 μg/L in Atenor and 9.612 μg/L in Paradela) and foals (19.378 μg/L in Atenor and 6.430 μg/L in Paradela). Selenium levels were lower in foals than adults and in males than females. Vitamin E was associated with overall foal health. Foals with a mean vitamin E of 3.585–5.307 mg/L showed signs of weakness, but carpal flexural deformities were observed when the average vitamin E was 11.520 mg/L. Low vitamin E levels (5.307 mg/L) in jennies were related to foal mortality. Diets, location, parity, and age affect blood profiles of jennies and, ultimately, foal health.

Recombinant Glycoprotein B of Equine herpesvirus Type 1 Elicits Protective Immune Response against Challenge in BALB/c Mouse Model

Background: Equine herpesvirus type 1 (EHV-1) is the most important viral pathogen of equines, causing respiratory illness, abortion, neonatal foal mortality and neurologic disorders. Large numbers of commercial EHV-1 vaccines are available to protect equines from the disease, but they provide only partial protection. Despite immunization with inactivated and modified live virus vaccine, mares show abortions. Present study was aimed to investigate the immunogenicity and protective efficacy of EHV-1 recombinant glycoprotein B (rgB) and gB expressing plasmid DNA against EHV-1 infection in BALB/c mice model.Methods: About 3-4 weeks old 225 female BALB/c mice were selected for the comparative study of immunization followed by challenged with EHV-1/India/Tohana/96-2 strain virus in 5 different groups of 45 animals each.Result: Following immunization, rgB vaccinated mice showed optimal stimulation of EHV-1 gB specific cell mediated and humoral mediated immunity (HMI and CMI). The gB expressing plasmid DNA vaccinated mice developed only CMI while inactivated whole virus vaccinated mice had only HMI. Upon EHV-1 challenge, all infected mice displayed variable levels of clinical signs with changes in body weight, however, vaccinated mice showed very rapid recovery with optimal protection. Positive control group mice showed severe pulmonary lesions along with persistence virus infection till 5 days post challenge (dpc) whereas vaccinated mice had less pulmonary lesion only up to 3dpc. Minimal lung lesions and early virus clearance was observed in the rgB immunized mice in comparison to the gB plasmid DNA and inactivated EHV-1 vaccine immunized mice. It has been concluded that immunization with rgB elicits optimum protective immune response against EHV-1 infection in mice model. The rgB could be a potential vaccine candidate against EHV-1 infection in equine in the future.

Understanding dystocia in the field: part 1

Difficult births (dystocias) are not uncommon for horses and present significant risks to mare and foal, with potentially fatal consequences. A sound understanding of the normal physiological processes before and during parturition are essential to enable vets to quickly identify when these processes deviate from the norm. To rapidly diagnose the cause of the dystocia, the attending obstetrician should be assured in their approach; resolute in their decision making; and prompt in action if the risks of mare and foal morbidity and mortality are to be managed. Constructive communication with the mare's owners is essential to allow adequate planning to prioritise the outcome. The future fertility of the mare is imperative in many cases yet is often overlooked. The obstetrician must be dynamic and be prepared to alter their approach when necessary. This review outlines the causes of dystocia and the recommended approaches to resolution.

Prevalence and performance effects of neonatal disease in Thoroughbred and Standardbred foals in South-Eastern Australia.

There is little information on foal mortality and the epidemiology of diseases in the neonatal period in Australian equine breeding enterprises. This was a prospective cohort study of 1219 foals on 15 breeding farms in south-eastern Australia to identify the proportion of foals recognised on farm as abnormal at birth or within the first 48 h postpartum, determine the prevalence and risk factors for neonatal disease and assess the subsequent performance of foals in the study population. Overall, 27 foals died within 6 weeks of birth in the study population (2.2%), 142 foals (11.6%) were reported as abnormal at birth, and 304 (25.3%) were regarded as abnormal in the first 48 h postpartum. Non-septic orthopaedic disease (NSOD) was the most common abnormality recognised. Premature foals and foals born after dystocia or abnormal parturition were more likely to have clinical abnormalities recognised, but the intensity of nursing care did not predict outcome. Prophylactic administration of antimicrobial drugs was associated with increased mortality and septic disease. Maternal periparturient problems, foal gender, abnormality at birth and the presence of septic disease or neonatal maladjustment were associated with decreased performance outcomes, whereas measures to assess and augment passive immune transfer were associated with improved athletic performance. Information in the current study is important for the treatment and management decisions on farm and to identify industry welfare and production priorities. Although the incidence of all outcome variables was variable, factors recognised on farm in the peri-parturient period were predictive of subsequent athletic performance.

The effect of foal or adult horse plasma on equine monocyte-derived dendritic cell phenotype and function

Immunological and endocrine immaturity in foals increases foal morbidity and mortality from bacterial sepsis. Dendritic cells (DC) are critical in activating the adaptive immune response, but foal DC are phenotypically and functionally different than those of adult horses. Age-related variations in availability of some soluble plasma factors, such as hormones, might govern some age-related differences in DC function. Effects of exposure to plasma factors on equine DC phenotype and function have not been described. We hypothesized that exposure to plasma from foals or adult horses would differentially impact monocyte-derived DC (MoDC) phenotype and function. Eight healthy adult horses and 8 healthy foals were divided into pairs of one adult horse and one foal. Blood was collected from each pair for MoDC generation when foals were 1 and 30 days of age. MoDC from horses and foals were then exposed to killed whole-cell bacteria in the presence of their own age-matched plasma, plasma from the opposite-aged animal in the pair, and serum-free medium alone (control). Expression of DC-relevant surface markers (MHC class-II, CD86, and CD14) and endocytosis capability were measured by flow cytometry. Supernatant cytokine concentrations (IL-4, IL-17, IFN-γ, and IL-10) were quantified with a validated bead-based immunoassay. Data were analyzed using linear mixed-effects and Tobit regression models (P < 0.05). The percentage of MoDC expressing surface markers MHC class-II and CD86 was reduced in MoDC derived from 1-day-old foals in comparison to adult horse MoDC when cultured in medium alone or with either source of plasma (P = 0.0001). Foal and adult horse MoDC cultured in either source of plasma expressed more CD86 and less CD14 than cells cultured in serum-free medium alone (P ≤ 0.02). Adult horse and foal MoDC exposed to bacterial antigen in the presence of 1-day-old foal plasma secreted less IL-10 (P ≤ 0.0008) compared to those cultured in adult horse plasma. Endogenous production of IL-17 by MoDC from foals at day 1 of age cultured in adult plasma was increased compared to foal MoDC cultured in serum-free medium (P = 0.004). Phagocytosis of killed, labeled Staphylococcus aureus was reduced when MoDC generated from foals or adult horses were exposed to plasma from foals at day 1 or 30 of age (P ≤ 0.03). Age-related variation in soluble plasma factors appear to regulate equine MoDC function, but specific plasma factors capable of regulating MoDC phenotype or function were not defined in this study.

Changing policy to treat foals with Rhodococcus equi pneumonia in the later course of disease decreases antimicrobial usage without increasing mortality rate.

There is a lack of data on the efficacy of treatment of Rhodococcus equi pneumonia in association with an optimised selection of foals. To evaluate whether targeted treatment protocols resulting in decreased antimicrobial use impact foal mortality rates. Retrospective study. Three hundred and thirty foals with pneumonia per year were randomly selected from 2008 to 2016. All foals were examined once weekly from birth until weaning. A physical examination of the respiratory tract, body temperature, haematology and an ultrasonographic examination of the lungs was included. Sonography areas with visible consolidation were measured and added to calculate an 'abscess score' which represents the extent of pulmonary damage. All weekly medical data were analysed retrospectively. In the period from 2008 to 2011, every foal with pulmonary abscesses was treated. The treatment protocol was changed in 2012 when only foals with larger lesions were treated. Between the two time periods 2008-2011 and 2012-2016, the abscess score at the beginning of treatment increased from a median of 4-11.5cm. From all foals that developed Requi pneumonia, 81.5% received antibiotic treatment in 2008-2011 (n=1215) compared with 50.9% in 2012-2016 (n=1541). The percentage of foals that died from pneumonia or Requi infections did not differ significantly between 2008-2011 and 2012-2016 (0.4% vs 0.6% respectively; P=.6). There was some lack of clarity in old data because this was a retrospective study; therefore, some foals had to be excluded from data analysis. Alteration of treatment criteria, to exclude antibiotic treatment of foals with smaller lesions, has significantly decreased the number of foals being treated without a significant increase in mortality from Requi pneumonia.

Development of equine herpesvirus 1 persistently infected human lymphoblastoid cells expressing latency-associated transcripts

Equid herpesvirus 1 (EHV1) is one of the most important equine viral pathogens causing respiratory disease in young animals, late-term abortions, neonatal foal mortality and myeloencephalopathy. Following acute infection, recovered animals develop life-long latent infection, with periodic reactivation. Latency is detected by demonstration of latency-associated transcripts (LATs) in selected tissues by PCR-based assays. EHV1 produces productive lytic infection in available susceptible cell culture systems within 1 week of infection and no in vitro model for studying the mechanism of EHV1 persistence, latency and reactivation is available. The objective of the present study was to establish persistently infected cells and to see whether these cells express LATs. Epstein-Barr Virus (EBV)-transformed human lymphoblastoid cells (LCs) were infected with EHV1 and observed for 120 days. Infectious extracellular and intracellular EHV1 was detected in LCs with mean titres of 104.35±0.09/ml and 101.78±0.12/ml, respectively, at 8, 30 and 120 days post-infection. Virus in infected LCs was also demonstrated by immunofluorescence and nested PCR. LATs corresponding to ORF64 in EHV1-infected LCs were detected from day 16 to day 120 post-infection by nested PCR and quantitative PCR. This is the first report of expression of LAT in EHV1 persistently infected LCs. These persistently infected cells may serve as model for understanding EHV1-associated latency.

Development of a multilocus sequence typing scheme for Rhodococcus equi

Rhodococcus equi causes pulmonary and extrapulmonary infections in animals and humans, with endemic situations and significant young foal mortality in stud farms worldwide. Despite its economic impact in the horse-breeding industry, the broad geographic and host distribution, global diversity and population structure of R. equi remain poorly characterised. In this context, we developed a multilocus sequence typing (MLST) scheme using 89 clinical and environmental R. equi of various origins and eight Rhodococcus sp. Data can be accessed at http://pubmlst.org/rhodococcus/. A clonal R. equi population was observed with 16 out of 37 sequence types (STs) grouped into six clonal complexes (CC) based on single-locus variants. One of the six CCs (CC3) is not host-specific, suggesting potential exchanges between different R. equi reservoirs. Most of the virulent equine R. equi CCs/unlinked STs were plasmid-type-specific. Despite this, marked genetic variability with the circulation of multiple R. equi genotypes was generally observed even within the same animal. Focusing on outbreaks, data indicated (i) the potential contagious transmission of R. equi during the 2012-Mayotte equine outbreak because of the poor genotype diversity of clinical strains; (ii) a potential porcine outbreak among the 30 Belgian farms investigated in 2013. This first Rhodococcus equi MLST is a powerful tool for further epidemiological investigations and population biology studies of R. equi isolates.

Differential distribution of vapA-positive Rhodococcus equi in affected and unaffected horse-breeding farms

Rhodococcus equi causes pulmonary and extrapulmonary infections in animals and humans, with endemic situations and significant young foal mortality in horse-breeding farms worldwide (von Bargen and Haas 2009, Muscatello 2012,...

Late-Term Abortion, Stillbirth, and Neonatal Foal Death in Kyrgyzstan: First Isolation of Equine Herpesvirus Type 1 in the Country

Late-term abortion, stillbirth, and neonatal foal mortality (commonly referred to as late fetal losses [LFLs]) of unknown etiology are a serious concern for horse farmers and breeders in Kyrgyzstan. Therefore, we investigated major infectious causes of LFL, with a focus on viral agents, for the first time in the horse population in the country. A total of 221 sera and 149 nasal swabs taken from mares in farms with a history of LFL within 1 year of testing as well as tissue samples collected from 17 LFL cases were investigated. Serologic studies revealed that equine herpesvirus type 1 (EHV-1) and type 4 (EHV-4) were prevalent in the population, although positivity rates were low with neutralizing antibody titers of 1:4 to 1:32 (median 1:8) against both pathogens. High antibody titers in the range from 1:32 to 1:512 (median 1:256) against equine arteritis virus (EAV) were detected in mares on a single farm, whereas three mares from different farms tested positive for Dourine. Virus isolation and PCR investigations of nasal swabs did not suggest ongoing active infection with EHV-1, EHV-4, or EAV in the examined mares. Bacteriologic and virological examination of tissue samples taken from LFL cases revealed the presence of Escherichia coli and/or Streptococcus equi (subsp. zooepidemicus) in 35% of neonatal foal death cases, and EHV-1 was isolated from a late-term abortion case representing the first isolation of this important pathogen of horses in the country and, to the best of our knowledge, in Central Asia.

Periparturient characteristics of mares and their foals on a New Zealand Thoroughbred stud farm

AIMS: To describe selected periparturient variables in a sample of Thoroughbred mares and their foals on a commercial stud farm in New Zealand.METHODS: Data were collected for 969 foaling records, from 592 mares, by foaling attendants from one Thoroughbred stud farm in the Waikato region of New Zealand for the breeding seasons 2008–2013, inclusive, and collated retrospectively. The associations between mare- and foal-level variables and gestation length, time of birth (expressed as the number of hours after midday), fetal membrane retention time, time for the foal to stand and suckle after birth, and foal mortality were quantified using linear and logistic regression models.RESULTS: Mean gestation length for mares in this study was 350 (min 296, max 429) days, and was shorter for filly foals (348 (min 296, max 429) days) compared with colt foals (350 (min 310, max 404) days) (p=0.001). Overall, 517/968 (53%) foalings occurred between 19:00 and 01:00 and 212/968 (22%) foalings occurred during daylight. Overall, 815/855 (95%) expelled their fetal membranes within 4 hours of parturition. The mean interval from birth to standing and to suckling was shorter (p<0.001) for filly foals than colts by 13 (95% CI=9–17) and 17 (95% CI=8–26) minutes, respectively. Dystocia was reported for 81/968 (8.4%) foalings with relative fetal oversize being the most common cause (36/81 (44%) cases). Perinatal foal death was recorded for 26/966 (2.7%) foalings. The odds of foal mortality decreased with increasing length of gestation (p=0.027), and were greater for colt than filly foals (p=0.042) and when dystocia was reported (p<0.001).CONCLUSIONS: Gestation length was influenced by the sex of the foal, as was the time taken for the foal to stand and suckle after birth. One fifth of mares foaled during daylight hours. The majority of mares in this study population expelled their fetal membranes within 4 hours of foaling.CLINICAL RELEVANCE: Accurate measures for periparturient behaviour can be important in the management of mares and newborn foals. Clinically relevant differences appear to exist between mares and foals in New Zealand and those in the Northern Hemisphere for some key parameters, likely as a result of differences in management and environment. The results of this study suggest that mares should be considered to have retained their membranes if not passed within 4 hours of parturition.

Scale‐dependent effects of density and habitat on foal survival

ABSTRACTIdentifying the most appropriate scale to study factors influencing life history is important to evolutionary ecology and wildlife management. For example, the scale at which density is assessed and explains variation in survival can affect how biologists observe and interpret population dynamics, which can influence plans for managing populations. Feral horses (Equus ferus caballus) contrast with most ungulates by exhibiting a mating system characterized by female‐defense polygyny with persistent, non‐territorial breeding groups (bands) and female‐biased initial (natal) and subsequent (breeding) dispersal. We predicted that for horses, offspring movements coupled with female‐biased breeding dispersal would increase the scale at which density best related to juvenile survival compared to species with greater female philopatry. From 2008 to 2013, we censused the population of feral horses on Sable Island, Canada. We annually computed individual‐specific local densities for 442 foals (horses/km2 in radii of 2,000 m, 4,000 m, and 8,000 m fixed to a band's centroid of movements) and whole‐island (total) population density, group (band) size, and local access to surface freshwater, which affected movement patterns and selection of vegetation by females. The population of feral horses increased from 380 in 2008 to 559 in 2013. Overwinter survival of foals averaged 82.8%. Island‐wide density was the most important predictor of foal mortality and was negatively associated with survival, with a lesser negative effect from local density. Increased access to surface freshwater (ponds) was an important predictor of foal survival but only at certain scales. Our study emphasizes the relevance of a multi‐scale approach when analyzing the response of fitness components to changes in habitat and population processes, which may be influenced by the particular social organization of the species. © 2015 The Wildlife Society.

Impact of inbreeding on fitness-related traits in the highly threatened Sorraia horse breed

The Sorraia horse population can be regarded as a universal equine genetic resource, most likely the representative of the ancestor of Iberian saddle horses and probably the ancestor of several New World horse breeds. The breed was recovered in 1937 and managed without further additions to the initial founder group of 12 horses, originating an extant population with extremely high inbreeding levels (mean F=0.38). There are only about 300 animals representing the Sorraia horse population worldwide, which places it in a critical risk status and strongly supports the need to establish a conservation-breeding plan aiming at a long-term self-sustaining population. Data on all registered horses in the Sorraia Studbook were used to study the impact of inbreeding on offspring's viability at birth and at 6 months of age, and a sub-sample was used to determine the influence of inbreeding on stallion and mare fertility rates, foaling intervals and age at first parturition. The effect of inbreeding on the analysed traits was only significant for the relationship of mare fertility with mare inbreeding coefficient (P=0.003). The influence of age of the mare was quadratic, with a reduction in foal mortality (both at birth and at six months of age) and an increase in foaling interval as age of mare increased. Stud farms had a statistically significant influence on age at first parturition. Decisive management-breeding plans must be taken to control inbreeding levels in Sorraia horses, and contribute to the conservation of this breed.

Viability analyses of an endangered donkey breed: the case of the Asinina de Miranda (Equus asinus)

The donkey breed Asinina de Miranda, with fewer than 1000 breeding females, is in danger of extinction. The objectives of this study were to predict the progression of the breed under present management and identify determinants for survival, by means of a population viability analysis program, in order to suggest suitable management strategies. The simulation showed a high risk of extinction. The most critical factor for breed survival was the percentage of females breeding per year, but the actual percentage needed depended on the carrying capacity of the breed. Reducing female mortality and age at production of first offspring, assuring registration in the Studbook, and tracking the foals will significantly foster this donkey breed’s recovery and maintenance. The breed comprised a potentially reproductive population of 589 individuals; however, just 54.1% of the adult females registered in the Studbook ever foaled, and of these 62.7% foaled just once. The overall neonatal mortality for the first month of life was 8.92% and was lower in females (6.51%) than in males (12.0%) (P = 0.028). Neonatal mortality was unevenly distributed throughout the year, with lower mortality rates recorded in February–May and October–November, and higher mortality rates in June–September and again in December–January. The neonatal foal mortality rate was lower with females aged 5–15 years (8.06%) than those younger than 4 years (10.3%) or older than 16 years (14.1%) at foaling.

Role of equine herpesviruses as co-infecting agents in cases of abortion, placental disease and neonatal foal mortality

Herpesviral infections frequently occur in horses. The objective of this study was to investigate the possible association of equine herpesviruses (EHV-1, EHV-2, EHV-3, EHV-4, EHV-5) with other causes of abortion, neonatal mortality or placental disorder. Sixty-seven abortions, 22 stillbirths, 14 cases of neonatal foal mortality and 3 cases of placental disease were investigated for infectious and non-infectious causes. Type-specific nested PCR assays and virus isolation were performed to detect EHV infections. A cause of fetal loss or placental disease was reached in 68 out 116 (58.7%) cases. Twenty-seven cases were positive for EHV, and 22/27 (81.5%) were positive for EHV-1 (16 neuropathogenic and 6 non-neuropathogenic strains), 4 (14.8%) for EHV-2 and 3 (11.1%) for EHV-5. The association between EHV infections and other etiological agents was statistically significant (two sided P = 0.002). The odds ratio of EHV DNA associated with other diagnoses, especially with bacterial infection and premature placental separation, was 10.88 (95% confidence interval: 2.15-55.16). EHV-1 was the main viral cause of pregnancy loss in this study, also associated with other etiological agents, including EHV-2 and EHV-5. The latter viruses in particular need to be more fully investigated to elucidate what role either or both may play as co-infecting agents with other established infectious causes of reproductive disease.

Development of a peptide ELISA for discrimination between serological responses to equine herpesvirus type 1 and 4 (EHV-1 and EHV-4)

Infections with equine herpesviruses type 1 (EHV-1) and 4 (EHV-4) can result in important economic losses for the horse industryworldwide. Both viruses are common causes of acute respiratory disease, while EHV-1 frequently induces abortion but also perinatal foal mortality and devastating neurological disease. EHV-1 and -4 are closely related alphaherpesviruses. Detection of EHV antibodies in serum is a common tool to determine whether a horse has been exposed to EHV. Despite the differences in their biological characteristics and genomic sequences, both viruses show strong antigenic cross-reactivity in any immunological assay that uses polyclonal serum as the source of antibodies. An effective serological tool capable of discriminating between antibodies responses to EHV-1 or EHV-4 in horses is of importance in disease control. In the present study, we describe the development and application of a type-specific EHV-1/EHV-4 ELISA based on peptide antigens. Seven and four peptides for EHV-1 and EHV-4, respectively, were initially studied with respect to their discriminatory potential in an ELISA setup using sera from experimentally infected foals. In our optimized protocol, plates were coated overnight at 4 C with 100 ml/well streptavidin at 1 mg/ml in 50 mM carbonate/bicarbonate buffer (pH 9.6), washed 3 times with washing buffer (PBS containing 0.1% Tween 20) and coated with 100 ml/well of respective biotinylated peptide at a concentration of 2 mg/ ml in carbonate/bicarbonate buffer. After incubation for 2 h at 37 C and extensive washing, wells were blocked with 100 ul/well of blocking buffer (1% goat serum in washing buffer) for 1 h at 37 C. After washing, 100 ml of horse serum diluted 1/400 or 1/1200 in washing buffer was added in triplicate and incubated for 1 h at 37 C. After 3 further washes, plates were incubated with 100 ml/well of HRP goat anti-horse immunoglobulin diluted 1/20,000 in blocking buffer for 1 h at 37 C. Following a final wash, the color reaction was developed for 10 min at room temperature by adding 100 ml/well of a chromogen/substrate mixture of TMB (240 mg/mL 3,3’,5,5’ tetramethylbenzidine) in Gallati buffer (42 mg/mL citric acid, pH 3.95/0.01% H2O2). The reaction was stopped with 100 ml/well of 1 M sulfuric acid and the optical density measured at 450 nm. Results were expressed as absorbance OD values and sera tested in triplicate against the EHV-1 and EHV-4 antigen. The most promising pair of peptides, EHV-1 glycoprotein E and EHV4 glycoprotein G peptides, was further evaluated using acute and convalescent sera from experimentally and naturally infected horses (Figure 1) as well as a panel of field sera. The results show that our peptide ELISA clearly identifies horses that have been infected with EHV-1 or EHV-4 using acute and convalescent sera and, when applied to a large number of field samples, revealed to be a robust assay for determining the EHV-1 and EHV-4 antibody status. With further validation, the developed EHV-1/EHV-4 peptide ELISA could serve as an effective and cheaper alternative to other current tools for EHV-1 and -4 serodiagnosis.

Parturition, dystocia and foal survival: A retrospective study of 1047 births

An understanding of the normal events of foaling, causes of dystocia and clinical outcomes is important for equine practitioners. The goals of the present study were to: 1) evaluate factors that influence gestation length; 2) report duration of Stage II labour; 3) determine the frequency of dystocia and premature placental separation; and 4) determine the relationship between problems at foaling and foal survival. Foaling records of 1047 mare births were evaluated. The average gestation length was 342.7 days [corrected] +/- 0.4 days, with no effect of mare age or breed observed. Mares carrying male fetuses had a longer gestation (P < or = 0.001) than mares carrying female fetuses. A majority (52.8%) of mares foaled at night between 2000 h and 0200 h when the facility was quiet. Dystocia occurred in 10.1% of all births and the incidence rate was higher in Thoroughbred mares than in Quarter Horse mares. The most common cause of dystocia was abnormalities of fetal posture. A delay in foal delivery beyond 40 min of Stage II of labour was associated with a significant increase in foal mortality. In addition, an increase in foal morbidity and mortality was noted when the interval from birth to standing or birth to nursing was prolonged. Early detection and rapid appropriate intervention are critical to foal survival in an equine dystocia. Equine veterinarians should counsel horse owners that early recognition of a foaling problem and rapid, appropriate intervention are critical to the survival of a foal.