An outbreak of equine neonatal salmonellosis

An outbreak of salmonellosis in foals occurred on a large Thoroughbred farm in California. Only foals less than 8 days of age exhibited clinical signs, which included depression, anorexia, and diarrhea. Three foals died from septicemia. The agent responsible was Salmonella ohio, which is rarely involved in salmonellosis in horses. During the course of the outbreak, S. ohio was isolated from 27 of 97 mares (27.8%) and 34 of 97 foals (35.1%). Mares were the presumed source of infection for foals. The absence of clinical signs in mares allowed for increased exposure of foals through environmental contamination. Although foals continued to become infected after strict control measures were adopted, none became ill. Salmonella serotypes of seemingly low virulence can produce serious disease outbreaks.     

An outbreak of paresis in mares and geldings associated with equid herpesvirus 1

An outbreak of paresis occurred on a small isolated stud farm in July 1980. Of the 42 horses on the stud, infection was confined to a group of nine in-foal mares and their foals and eight other horses which were either housed together at night or grazed adjacent pastures. Eight mares and two geldings developed ataxia or paresis and one mare died. Equid herpesvirus 1 was isolated from 17 animals and serological studies confirmed that 24 of 26 animals sampled had experienced infection.     

Thoracic trauma in newborn foals

In a report describing life ending fractures (255 horses) from the Livestock Disease Diagnostic Center, Kentucky (1993 and 1994), 32 foals had rib fractures. The purpose of our study was to examine the incidence of rib fractures in newborn foals on a Thoroughbred studfarm by physical and radiographic examination, to determine factors which may contribute to the problem and to document any clinical consequences. All foals (263) included were examined within 3 days of birth. The thoracic cage was palpated externally for abnormalities and all foals were placed in dorsal recumbency to evaluate thoracic cage symmetry. Radiographs were used to diagnose foals with thoracic cage asymmetry (TCA) and rib fracture (RF). A diagnosis of costochondral dislocation (CD) was made when no radiographic evidence of fracture was present but there was severe TCA. Fifty-five foals (20.1%) had TCA (9 RF). One to 5 ribs were fractured on 9 of 40 radiographic studies. No consequences of the thoracic trauma was detected clinically, radiographically or ultrasonographically in this group of foals or at a 2- and 4-week follow-up examination. The percentage of foals with a history of abnormal parturition was higher in the TCA foals (15%) compared to the normal foals (6.8%). There were more primiparous dams in the TCA group than in the normal foal group. Fillies (56.6%) had a higher incidence of birth trauma than colts (43.4%). This study demonstrates that thoracic trauma is often present in newborn foals and may not always be of clinical significance. Dystocia foals and foals from primiparous mares should be considered high risk for thoracic trauma.     

Enzootic viral abortion on a stud farm in east Switzerland

An outbreak of abortion due to the equine herpesvirus-1 (EHV-1) in the eastern part of Switzerland is reviewed. Seven of eleven pregnant mares aborted within twenty-three days in January 1989. Four weeks later another foal died a few minutes after parturition. Three mares delivered live foals in February, March and April without any complications. The examination of the eight dead foals revealed an EHV-1 Infection. The clinical signs and the pathology are discussed. Severe complications during the early post-parturient time are in contrast to the uncomplicated outcome mentioned by other authors. Procedures for prevention and control are listed.     

Neonatal Equine Herpesvirus Type 1 Infection on a Thoroughbred Breeding Farm

Of 17 foals born on a Thoroughbred breeding farm between March and April 1995, infection with equine herpesvirus type 1 (EHV-1) was associated with neonatal morbidity in 5 foals, 3 of which died or were euthanized. Morbidity and mortality were associated with pulmonary inflammation, and EHV-1 was identified in the lungs of the 3 foals that died. All neonatal EHV-1 infections occurred in foals of mares housed in the same pasture and barn. No other clinical manifestations of EHV-1 infection (eg, abortion, neurologic disease, or respiratory disease) occurred during this outbreak. Three foals were treated with acyclovir (1 died, 2 survived), which may have influenced the clinical outcome in the surviving foals.     

Seroprevalence of equine herpesvirus 1 in mares and foals on a large Hunter Valley stud farm in years pre- and postvaccination

OBJECTIVE: To examine the prevalence of equine herpesvirus 1 antibody in mares and foals on a large Hunter Valley Thoroughbred stud farm in New South Wales before and after the introduction of an inactivated whole virus vaccine. DESIGN: Cross-sectional serological surveys performed in February 1995 and 2000 to determine the prevalence of EHV-1 antibody-positive mares and foals. A further cross-sectional survey was carried out in 2001 to complement the 2000 data. STUDY POPULATION: Two hundred and twenty-nine mares and their foals were sampled in 1995 and 236 mares and their foals were sampled in 2000. The study population comprised all of the mares with foals at foot on this property at each sample period. Fifty mares were sampled in both studies. A further 264 mares and their foals were sampled in 2001. PROCEDURE: A blood sample was collected from each mare and foal at the beginning of February 1995, 2000 and 2001. Each sample was tested in triplicate using an antibody-detection ELISA that is type-specific for EHV-1 and EHV-4 antibodies. RESULTS: The prevalence of EHV-1 antibody-positive mares was not statistically different in 2000 compared to 1995. However, the prevalence of antibody-positive foals was significantly lower in 2000 than in 1995. In 2001, the prevalence of antibody-positive mares was higher than in 2000, but not different from that in 1995. The prevalence of antibody-positive foals in 2001 was not significantly different from the prevalence observed in 1995 or that observed in 2000. However, when the three studies were compared there was a significant variation in the prevalence of EHV-1 positive foals due to the variation between the 1995 and the 2000 data. CONCLUSIONS: Mares are the source of virus from which foals are infected early in life and following analysis of the 2001 data, the difference in the prevalence of EHV-1 antibody-positive foals between 1995 and 2000 was likely to be a reflection of seasonal, nutritional and management factors, rather than the result of vaccination.     

Prevalence of Eimeria leuckarti (Flesch, 1883) and intensity of faecal oocyst output in a herd of horses during a summer grazing season

The prevalence of Eimeria leuckarti infection and the intensity of faecal oocyst output were determined in a herd of 14 mares and their foals in northwest Germany using a sedimentation technique at weekly intervals during a summer grazing season from May to September. None of the mares, but all foals shed oocysts on at least one occasion. The patent periods lasted up to 16 weeks. The mean intensity of oocyst output (0.1-33 o.p.g.) was very low. No clinical signs of gastrointestinal disorder were noticed in any of the foals during this study.     

Studies of passive immunity in foals to equine viral arteritis

The capacity of colostral samples collected from mares immune to equine viral arteritis to neutralize arteritis virus was two or more times greater than that present in the dams' sera. This activity in the mammary secretions was very low or undetectable after 1 week. The capacity of sera from eight of the nine foals born to immune mares to neutralize arteritis virus was high at 1 week of age. All of the titres had declined to extinction after 2–6 months. Arteritis virus neutralization was not detected in serum collected from foals prior to nursing or in samples from non-immune mares and their foals.Foals from immune mares developed mild signs or no signs of disease when inoculated nasally with virulent arteritis virus at 6 days of age.Seven- to nine-day-old foals from non-immune mares responded to vaccinationas they had appreciable serum-virus neutralizing antibody titres 6 months after vaccination and did not develop signs of disease when inoculated nasally with virulent virus. Foals of the same ages from immune mares did not respond to the vaccine since antibody could not be detected 6 months after vaccination and they either died or experienced clinically severe disease when inoculated nasally with virulent arteritis virus.     

An unusual case of generalized soft-tissue mineralization in a suckling foal

An atypical case of severe soft-tissue mineralization in a 3-week-old foal from a herd of Andalusian horses is described. The herd clinical history and the laboratory findings were compatible with a diagnosis of secondary hyperparathyroidism due to a mineral imbalance in the diet (low calcium and high phosphorus intake). Mares showed a marked increase in serum parathyroid hormone (PTH) approximately 10 times normal levels. Serum PTH was marginally elevated in foals. Clinical signs (unthriftiness, painful joints, lameness in one or more limbs, and stiff gait) were more pronounced in foals than in mares. Two foals died and necropsy of one of them revealed extensive soft-tissue mineralization of arterial walls and pulmonary parenchyma. Clinical signs in mares and foals resolved by 4 weeks after diet adjustment.     

The Effects of Ivermectin Given Postpartum on the Incidence and Severity of Foal Heat Diarrhea

Foal heat diarrhea (FHD) is a major factor in the management of foals between 2 and 3 wk of age. The objective of this on-farm study was to determine the efficacy of postpartum anthelmintic treatment of mares for reducing the incidence and/or the severity of FHD in foals caused by parasitic infestation. Twenty-four Quarter Horse mares and their foals were alternately assigned to a treated or non-treated group according to expected foaling date. Treatment consisted of oral administration of Zimectrin® (Farnam Companies, Inc., Phoenix, AZ) to the dam within 12 h post-foaling. From d l through 25, foals were weighed, and vital signs and severity or absence of diarrhea were recorded. Incidence scores of 0 to 3 were assigned to each foal based on severity of diarrhea: 0 = no affliction and 3 = severe, watery diarrhea. There was no difference in incidence scores because of treatment; however, there was a trend for foals from treated mares to experience more severe diarrhea with a shorter duration. There was no difference in BW gain related to treatment or nontreatment of mares. Postpartum administration of Zimectrin to mares did not significantly decrease the incidence or severity of diarrhea in foals. Additionally, it did not affect growth rate of foals. The trend for foals from treated mares to have a shorter duration of FHD may be beneficial to farm managers who spend time and money treating and cleaning foals.     

The Athletic Performance of Thoroughbred Racehorses out of Mares with Suspected Placentitis during Gestation

Thoroughbred mares treated for signs of placentitis are potentially costly to farms and owners. Although these treatments often are effective, the resulting foal may require expensive aftercare. The current study investigated the future racing performance of foals from mares treated for clinical and subclinical signs of placentitis compared with matched control mares that had no signs of placentitis producing foals on the same farms. In total, 190 horses born from mares with suspected placentitis met the criteria for analysis and were matched with 190 horses born on the same farm. Mare data and percentage of stakes winners in each group were analyzed with Student t test. Analysis between pairs of horses was done using a paired t test for number of starts, wins, places, shows, and amount earned. Significance was set at a P value of <.05. Mares with suspected placentitis were slightly older than control mares, had slightly shorter lengths of gestation, and had a longer interval to subsequent pregnancy than control mares (P < .05). Horses out of suspected placentitis mares that were racing as 2 year olds in the study had no difference in starts, wins, places, shows, and percentages of black-type race winners; however, this group earned more than their matched control pairs (P < .05). Older horses (3 year olds) out of suspected placentitis mares had no differences in number of starts, wins, places, shows or amount earned; however, the matched control older horses had more black-type race winners (P < .05). The information from this study may aid owners when making decisions about treatment options.     

Surgical treatment of uterine torsion using a ventral midline laparotomy in 19 mares

OBJECTIVE: To report on the outcome of surgical treatment of uterine torsion in preterm mares. DESIGN: Retrospective case series of pregnant mares with uterine torsion presented to the Clinic for Obstetrics, Gynaecology and Andrology of Large and Small Animals. METHODS: Hospital records of all pregnant mares that underwent ventral midline laparotomy for uterine torsion between 1998 and 2004 were reviewed. The signalment, history, clinical signs, results of diagnostic procedures, direction and degree of the uterine twist, treatment and outcome were retrieved from each case record. RESULTS: This study comprised 19 mares between months 5 and 11 of pregnancy (8.7 +/- 1.9) and suffering from uterine torsion. In all cases ventromedian laparotomy was carried out under general anaesthesia. Gastrointestinal disorders were also present in 52.6% of horses. Postoperative complications included subcutaneous seromas (five mares), peritonitis (one mare) and abortion (two mares). In four mares (21%) the operation was unsuccessful (i.e. these mares had to be euthanased intra- or postoperatively). Of the surviving 15 mares, 13 (86.6%) gave birth to viable foals at full term. The foals developed normally. Only two mares aborted. CONCLUSIONS: Because of its versatility the ventral midline approach should be considered for correction of uterine torsion. The approach has many advantages, including rapid and clear access to the abdominal cavity, safety, visual assessment of uterine wall viability, correction of concomitant gastrointestinal tract problems, and performance of hysterotomy or hysterectomy, if indicated. In this study, managing uterine torsion in this way resulted in a high percentage of cases (86.6%) in which pregnancy was maintained, with the birth of a viable, mature foal.     

Plasma Leptin Level in Hyperlipidemic Mares and Their Newborn Foals

The aim of this study was to evaluate the relationship between plasma leptin and lipid levels in breeding mares and their newborn foals. The study was conducted on 17 Polish cold‐blood mares and their newborn foals. The mares were divided into two groups, according to the course of delivery. These groups were seven mares which had a normal delivery and 10 mares which had required veterinary intervention during their delivery. Blood samples were taken from the jugular vein of both the mares and their foals. The blood samples were taken within 30 min after delivery, as well as on four successive mornings directly afterwards. In obtained plasma samples, the leptin, triacylglycerols (TG) and free fatty acid (FFA) concentrations were measured. The leptin and TG levels in the plasma sampled on the day of delivery and the two following days were significantly higher in mares which received veterinary intervention during the delivery, when compared to the results obtained from the plasma of mares which had normal delivery. The results obtained from foals did not show any statistical differences. In conclusion, the conducted tests have shown that post‐parturient hyperlipidemia and hyperleptinemia in mares did not influence the lipid status and plasma leptin level in newborn foals.     

Passive transfer of Theileria equi antibodies to neonate foals of immune tolerant mares

Equine babesiosis, a tick transmitted haemoprotozoan disease caused by Theileria equi is globally distributed and responsible for heavy economic losses to the equine husbandry. Equids reared in endemic areas usually pick up infection at an early age and become immune tolerant throughout their life span. We studied the level of passively transferred antibodies in neonate foals born from pre-immuned mares. Latently T. equi infected pre-immuned pony and donkey mares (three each) were selected and T. equi antibody titres in neonates was monitored till 90 days post foaling (DPF) by applying Dot-ELISA on sequentially collected serum samples from foals and their dams. A very high antibody titre was observed in pre-immuned pony and donkey mares. The maximum antibody of 1:60 to 1:80 was observed in pony's and donkey's foal on 2–16 and 2–10 DPF, respectively and thereafter it declined to less than 1:20 on 63–77 and 56–63 DPF. Simultaneously parasite carrying status in neonate foals and their dam was also monitored by applying PCR on blood samples. We could demonstrate PCR amplification in dam's blood samples while no amplification was recorded in neonate's blood samples. This study indicated that new-born foals were born naïve and passively transferred immunity was transitory which wanes after 63–77 DPF.     

Passive transfer failure in horses: incidence and causative factors on a breeding farm

A prospective study was performed to determine the incidence and associated maternal and managemental factors of failure of passive transfer (FPT) in foals on a breeding farm. The zinc sulfate turbidity test (ZSTT) and latex agglutination test (LAT) were compared for accuracy in estimating serum immunoglobulin (Ig)G of foals, as determined by single radial immunodiffusion (SRID). Complete past and present foaling histories of 136 Standardbred mares were obtained. All foalings were witnessed by farm attendants, and colostral samples were collected from mares within 2 hours after parturition. Foals that did not rise and nurse were supplemented with colostrum from the dam, using a bottle or nasogastric tube. Serum samples were prepared from foals and mares between 24 and 36 hours after parturition, and from some mares 45 to 90 days before parturition. Serum IgG concentrations of mares and foals and colostral whey were determined, using SRID. Serum IgG also was estimated in foals, using ZSTT and a commercially available LAT. Four of the 136 foals (2.9%) had FPT (serum IgG less than or equal to 400 mg/dl). Serum IgG concentrations in foals significantly correlated with colostral IgG (P less than 0.001). A significantly larger proportion of foals with FPT were bottle-fed their colostrum (P less than 0.01). Month of parturition, mare age, parity, number of barren seasons, incidence of assisted births or retained placenta, or prepartum serum IgG concentrations did not significantly affect colostral IgG concentrations or serum IgG concentrations in foals. As serum IgG concentrations in foals decreased and as colostral IgG concentrations decreased, the proportion of mares that prelactated significantly (P less than 0.01) increased.(ABSTRACT TRUNCATED AT 250 WORDS)     

Epizootiological examination of a respiratory disease associated with mycoplasma infection in horse

The authors examined 585 samples from 92 mares of 2 studs and 346 nasal swabs taken from their foals for the presence of mycoplasmas. The positive rates of mares and foals were 81.5% and 71.7%, respectively, with positivity of samples being variable. Clinical symptoms developed in 2-4 waves and lasted 3-7 days, with intervals of 7-12 days. The disease started in April among foals born in February, at an average age of 88 days. Later on, the average age of the affected foals decreased. There was a correlation between presence of mycoplasmas in nasal cavity and disease of foals.     

An equine herpesvirus 1 (EHV1) abortion storm at a riding school

An outbreak of EHV1 abortions occurred at a riding school in The Netherlands in 1991. Seven of twelve pregnant mares aborted, and another foal died at 8 days of age. Six abortions occurred within 12 days in March after an initial abortion on 8 February. Four mares delivered live foals. Virological examination of four aborted foals revealed an EHV1 infection. Serological results for paired sera from 17 horses suggested, that the initial abortion on 8 February was the index case, and probably caused the other six abortions. The index case could well have been caused by reactivation of latent virus induced by transport stress. The laboratory results are discussed in the light of the present knowledge of the pathogenesis and epidemiology of EHV1 abortion.     

The potential of embryo transfer in a German horse‐breeding programme

A reference horse‐breeding programme with 13 500 foals each year was modelled with ZPLAN+. This new software for the optimization of the structures in breeding programmes is based on ZPLAN. In two scenarios, the implementation of a rigorous selection of mares was implemented. In scenario I, the mare performance test was the point of selection, while in scenario II, further information on 20 competitions in two more years is available. These selected mares were used for embryo transfer (ET), partly in combination with multiple ovulation (MOET). The selection intensity and the number of foals out of (MO)ET were varied in both scenarios. It was expected that 250, 500 and 1000 mares are available for selecting 20, 50, 100 or 200 donor mares each year. The number of foals out of (MO)ET was varied between one and six foals per donor mare and year. Donor mares were used for ET for 4 years. It became clear that with high selection intensities of donor mares and high reproduction rates of them, the yearly genetic gain in a horse‐breeding programme could increase over a large range. In scenario II, the additional information on 20 competitions increased the accuracy of the selection index to 0.85. With 200 selected donor mares of 1000 available mares and six foals per year, the genetic gain could almost be doubled compared to the reference scenario. The implementation of ET and a related higher usage of few selected mares entails rising costs and a reduction in the genetic variance. In the most extreme MOET scenario, the effective population size was reduced by 19% relative to the reference scenario. Only if the increase in genetic gain can be converted into higher return for the breeders, the implementation of (MO)ET schemes is a realistic and sensible option for horse‐breeding programmes.     

Evaluation of fecal samples from mares as a source of Rhodococcus equi for their foals by use of quantitative bacteriologic culture and colony immunoblot analyses

OBJECTIVE: To determine whether mares are a clinically important source of Rhodococcus equi for their foals. SAMPLE POPULATION: 171 mares and 171 foals from a farm in Kentucky (evaluated during 2004 and 2005). PROCEDURES: At 4 time points (2 before and 2 after parturition), the total concentration of R equi and concentration of virulent R equi were determined in fecal specimens from mares by use of quantitative bacteriologic culture and a colony immunoblot technique, respectively. These concentrations for mares of foals that developed R equi-associated pneumonia and for mares with unaffected foals were compared. Data for each year were analyzed separately. RESULTS: R equi-associated pneumonia developed in 53 of 171 (31%) foals. Fecal shedding of virulent R equi was detected in at least 1 time point for every mare; bacteriologic culture results were positive for 62 of 171 (36%) mares at all time points. However, compared with dams of unaffected foals, fecal concentrations of total or virulent R equi in dams of foals with R equi-associated pneumonia were not significantly different. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that dams of foals with R equi-associated pneumonia did not shed more R equi in feces than dams of unaffected foals; therefore, R equi infection in foals was not associated with comparatively greater fecal shedding by their dams. However, detection of virulent R equi in the feces of all mares during at least 1 time point suggests that mares can be an important source of R equi for the surrounding environment.     

Induction of parturition in mares: effect on passive transfer of immunity to foals

Parturition was induced in 11 mares, using a synthetic prostaglandin. Eight mares, not treated, were used as controls. There was no significant difference between the serum immunoglobulin G (IgG) concentrations of the treated and control mares. The concentration of IgG in the colostrum of treated mares compared favorably with that reported for naturally foaling mares. Four foals from treated mares died or were euthanatized because of weakness during the 1st 24 hours after birth. The mean IgG concentration in the surviving foals from treated mares at 24 to 36 hours of age was 1,561 mg/100 ml, which was significantly (P less than 0.01) lower than the mean concentration of 2,731 mg/100 ml in foals from control mares. The mean serum IgG concentration in foals from control mares was significantly (P less than 0.01) greater than that of their dams, whereas the mean serum IgG concentration of the foals from treated mares was significantly (P less than 0.01) lower than that of their dams.