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1.
Rhodococcus equi (R equi) pneumonia is an important cause of disease and death in foals. Feces from mares can contain R equi, including virulent R equi, and thus may act as a source of the bacteria at horse breeding farms. A previous report documented that every mare at a farm in central Kentucky shed virulent R equi in at least one of four fecal samples collected serially during the periparturient period. The objective of this study was to assess the extent to which this high prevalence of fecal shedding could be replicated at other horse breeding farms. The frequency of detection of R equi and virulent R equi in fecal samples was studied among 131 mares from 24 farms in central Kentucky. The proportions of fecal samples from mares containing R equi and virulent R equi were 95% and 76%, respectively. These findings indicate that R equi and virulent R equi may be isolated with high frequency from feces of mares at breeding farms in central Kentucky, and that mares are a source of virulent R equi for the environment of their foals.  相似文献   

2.
The results of 3 years (2005–2007) of observations and mating (5,646 estrous cycles of 3,788 mares bred to 1 of 15 stallions) at one Thoroughbred breeding farm in central Kentucky were analyzed by a multiple logistic regression model using Bayesian statistics to evaluate the relationship between data entries (factors) and pregnancy outcomes. Factors found to be significantly (P < .05) associated with pregnancy outcome included stallion (one stallion had lower OR for pregnancy higher odds ratio [OR] for pregnancy, and one had, than other stallions), date of mating (OR for pregnancy declined slightly in May – July), mare age (OR for pregnancy were higher for mares <13 years old, and lower for mares >18 years old), mare beginning status (foaling mares had a higher OR for pregnancy), mating on foal heat (lowered OR for pregnancy), mating of the day for the stallion (OR for pregnancy was 4.16 times lower for fifth compared with first mating of day), reinforcement breeding (increased OR for pregnancy), dismount semen neutrophil score (lowered OR for pregnancy when neutrophils were present in dismount semen samples), and tranquilization before breeding (lowered OR for pregnancy in foaling and barren mares). The influence of dismount sample sperm motility scores on OR for pregnancy was weak, so motility scores were not included in the final logistic regression model. The majority of variation in pregnancy outcome was because of mare factors, with only approximately one-third of the variation in fertility explained by stallion.  相似文献   

3.
Contagious equine metritis (CEM) is a highly contagious venereal disease of horses caused by Taylorella equigenitalis. During testing for semen export purposes, a stallion in Kentucky was found to be T. equigenitalis culture positive in December of 2008. This finding triggered an extensive regulatory investigation to search for additional positive horses, determine the extent of the outbreak, identify the potential source of the outbreak, and ultimately return the United States to CEM-free status. The investigation included over 1000 horses located in 48 states. Diagnostic testing found a total of 22 stallions, 1 gelding and 5 mares culture positive for T. equigenitalis. Epidemiologic analysis indicated that all of the positive horses were linked to a single common source, most likely a Fjord stallion imported into the United States in 2000. The T. equigenitalis strain subsequently spread to other stallions via undetermined indirect mechanisms at shared breeding facilities, and to mares via artificial insemination and live breeding. This CEM outbreak and investigation represent the largest ever in the United States based on the number of exposed horses tested and their geographic distribution.  相似文献   

4.
Pregnancy rates in managed horse populations depend on the innate fertility of the mares and stallions involved and on the quality of breeding management. Of course, because a single stallion usually mates many mares, stallion fertility is a critical factor in the overall success of a breeding program. Unfortunately, accurate evaluation of stallion fertility per se requires a large number of normal mares to be mated and is necessarily retrospective. Rather, the ideal is to predict fertility in advance of the stallion's breeding career, and this is currently attempted by way of a thorough physical examination and a routine analysis of semen quality. However, while such a ‘breeding soundness examination’ identifies stallions that clearly lack the capacity for adequate fertility, it is of limited use for predicting the level of fertility and fails to identify some seriously sub‐fertile animals. Similarly, while various sperm function tests (e.g., sperm head morphometry, the hypoosmotic swelling test, glass wool‐sephadex filtration, progesterone receptor exposure) have been shown to correlate fairly well with fertility in the field, most examine only a single or a narrow range of the attributes that a sperm must possess if it is to fertilize an oocyte in vivo, and are thus more useful for identifying specific causes of sub‐fertility than for predicting the level of fertility. On the other hand, combining the results of the various sperm function tests does improve the reliability of fertility estimation and current research is therefore concentrated on identifying a range of tests that covers as many important sperm attributes as possible but that can be performed rapidly and cheaply. In this respect, flow‐cytometry has proven to be an ideal tool because it allows the objective, rapid and simultaneous analysis of a number of properties in a large number of sperm. Moreover, stains are available for an increasing range of sperm characteristics including viability, capacitation and acrosome status, mitochondrial activity and chromatin integrity. Flow‐cytometric analysis of sperm with appropriate probes thus offers considerable promise for the prediction of stallion fertility.  相似文献   

5.
To evaluate factors contributing to fertility of thoroughbred mares, data from 3743 oestrous periods of 2385 mares were collected on a large thoroughbred farm in Ireland. Fourteen stallions (mean age 8.3 years; range 4–15 years) had bred 2385 mares (mean age 9.4 years; range 3–24 years). Maiden mares accounted for 12%, mares with a foal at foot for 64%, and barren, slipped or rested mares for 24% of the total. The mean pregnancy rate per cycle was 67.8% (68.6% in year 1 and 66.9% in year 2). Backward stepwise multivariable logistic regression analysis was utilized to develop two models to evaluate mare factors, including mare age, reproductive status, month of foaling, dystocia, month of cover, foal heat, cycle number, treatments, walk‐in status and stallion factors including stallion identity, stallion age, shuttle status, time elapsed between covers and high stallion usage on the per cycle pregnancy rate and pregnancy loss. Old age (p < 0.001) and cover within 20 days post‐partum (p < 0.003) were associated with lowered pregnancy rates. High mare age (p < 0.05) and barren, slipped or rested reproductive status (p = 0.05) increased the likelihood of pregnancy loss. Uterine inflammation or infection, if appropriately treated, did not affect fertility. Only high usage of stallions (used more than 21 times in previous week) was associated with lowered (p = 0.009) pregnancy rates. However, shuttle stallions were more likely to have increased (p = 0.035) pregnancy survival, perhaps reflecting a bias in stallion selection. In conclusion, mare age exerted the greatest influence on fertility; nonetheless, thoroughbreds can be effectively managed to achieve high reproductive performance in a commercial setting.  相似文献   

6.
Status of equine viral arteritis in Kentucky, 1985   总被引：1，自引：0，他引：1  
Clinical cases of equine arteritis virus infection have not been diagnosed in Kentucky since 1984, and there has been no indication that any of the horses involved in the 1984 epizootic have since been responsible for spread of the disease to horses in other states or other countries. Cases of abortion caused by naturally acquired infection with this virus have not been confirmed in 1984 or 1985. Neither field nor vaccine strains of equine arteritis virus have been shown to induce teratologic abnormalities or the carrier state in foals born to infected or vaccinated mares. The carrier stallion appears to have played a major epidemiologic role in the dissemination and perpetuation of the virus. A commercial modified live equine viral arteritis vaccine was found to be safe and efficacious for stallions and mares. The disease can be controlled by immunizing the stallion population and by restricting the breeding of equine arteritis virus-shedding stallions to vaccinated or seropositive mares, followed by an appropriate period of isolation from other nonvaccinated Equidae.  相似文献   

7.
Streptococcus equi subsp. zooepidemicus is the pathogen most commonly isolated from the uterus of mares. S. zooepidemicus is an opportunistic pathogen and part of the resident flora in the caudal reproductive tract. The aim of this study was to investigate whether a genotypically distinct subpopulation of S. zooepidemicus is associated with endometritis in the mare, by genotyping and comparing uterine S. zooepidemicus strains with isolates from the vagina and clitoral fossa. Mares with (n = 18) or without (n = 11) clinical symptoms of endometritis were included. Uterine samples were obtained using a guarded endometrial biopsy punch, whereas a swab was used to recover samples from the cranial vagina and the clitoral fossa. If S. zooepidemicus was present, up to three colonies were selected from each anatomical location (max. 9 isolates per mare). Bacterial isolates were characterized by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). S. zooepidemicus was isolated from the endometrium of 12 mares. A total of 88 isolates were analyzed by PFGE: 31 from the endometrium, 26 from the cranial vagina and 31 isolates from the clitoral fossa. For MLST 21 isolates were chosen. Results demonstrated a higher genetic similarity of the isolates obtained from infectious endometritis compared to isolates obtained from the caudal reproductive tract. In conclusion, we demonstrate for the first time that a genetically distinct group of S. zooepidemicus is associated with infectious endometritis in the mare.  相似文献   

8.
Contagious equine metritis (CEM) has given rise to international concern since it was first recognized as a novel venereal disease of equids in 1977 and the etiologic agent was identified as a previously undescribed bacterium, Taylorella equigenitalis. Horse industry concerns over CEM centered on the ease with which this bacterium could be disseminated, the significance of T. equigenitalis as a cause of short-term infertility in the mare, and the existence of the carrier state in the stallion and the mare. The first known outbreak of CEM in the United States was in Kentucky in 1978. The economic impact on the Thoroughbred industry in the state was substantial. Before 2008, additional small-scale outbreaks occurred in Missouri in 1979, Kentucky in 1982, and Wisconsin in 2006, nearly all attributed to the importation of carrier animals. On each occasion, appropriate measures were taken to eliminate the infection, resulting in the United States regaining its CEM-free status. With the exception of the 1978 occurrence in Kentucky, none of the subsequent outbreaks significantly affected the horse industry. That changed dramatically in 2008, however, after the discovery of a Quarter horse stallion in Kentucky that cultured positive. Subsequent investigations turned up 23 carrier stallions and 5 carrier mares belonging to 11 breeds and located in 8 states. Shipment of infective semen and indirect venereal contact in stallion collection centers through the use of contaminated fomites were major factors in the spread of T. equigenitalis. Trace-back investigations of some 1,005 exposed and carrier stallions and mares in 48 states have failed to identify the origin of this latest CEM event. Neither clinical evidence of CEM nor decreased pregnancy rates were reportedly a feature in infected or exposed mares. In light of these findings, there was some question of whether or not the considerable expense incurred in investigating the latest CEM occurrence was warranted. Regaining CEM-free status for the United States will present considerable challenges.  相似文献   

9.
A method of predicting a stallion to mare ratio for horses entering either natural service or artificial insemination programs was discussed. Limiting factors for stallions in hand-breeding situations were age, libido and physical ability to cover mares presented for breeding. Other limiting factors for stallions involved in artificial breeding programs were scrotal width, daily sperm output, and the number of live spermatozoa inseminated per mare. Considerations were given for the seasonal effect upon pregnancy rate of the mare, but no considerations were made for seasonal effect upon the stallion. This method must only be applied to stallions that have undergone a thorough breeding soundness examination. It must be emphasized that it served only as a guide; the calculated values were merely useful estimates rather than firm numbers. The multitude of uncontrollable factors involved in breeding farm management, especially with regard to the mares that are presented for breeding were influences that could not be directly considered by this method.  相似文献   

10.
Feed with ergot alkaloids ingested by horses has a deleterious clinical and economic impact on the industry. The clinical manifestation of the effects in mares is early embryonic mortality, abortions, prolonged gestation, dystocia, thickened (edematous) or retained placental membranes, agalactia, and increased rates of newborn mortality. For the stallion, very little is known, although ergot alkaloids decrease the ejaculate volume. However, a large number of breeding stallions graze endophyte infected (E+) pastures. This is especially true in the southeastern United States, and clinically we do not perceive that any stallions have any defined problems that could be attributed to ergot alkaloids. However, the number of spermatozoa produced by any stallion might mask the effects. The effects on fertility may be more subtle and only evident with sperm cell manipulation such as chilling or freezing. A preliminary study was performed on six breeding stallions fed feed containing infected fescue seed. We were not able to determine any significant (P < .05) detrimental effects on sperm motility, number morphology, and sperm morphology when compared with controls.  相似文献   

11.
目的 研究分析新疆昭苏地区不同性别、不同年龄段纯血马在不同月份的寄生虫感染情况,为纯血马的健康养殖以及科学驱虫提供参考。方法 随机选取不同年龄段纯血马122匹,分为5组,哺乳马驹30匹,青年母马25匹,青年公马20匹,繁殖母马35匹,种公马12匹。采用马场分栏群体舍饲和单厩饲养模式,保证不同年龄段纯血马饲料和饮水充足,分别在5月和10月采集粪便样品。使用虫卵计数法检测马匹粪便中的寄生虫,计算不同年龄纯血马在不同时间段的寄生虫感染率和感染强度。结果 5月纯血马马蛲虫以及马球虫感染率较高,除种公马外,感染率均在94.00%以上,其中,哺乳马驹马蛲虫的感染率高达98.89%,哺乳马驹马球虫的感染率高达98.33%。10月纯血马马副蛔虫以及马球虫的感染率均在93.00%以上,其中,繁殖母马马副蛔虫感染率高达99.52%,哺乳马驹马球虫感染率高达98.33%。5月哺乳马驹的马副蛔虫、毛圆线虫、盅口线虫与细颈三齿线虫感染强度均显著（P<0.05）高于其他年龄段的纯血马;马蛲虫、马球虫和埃氏腹盘吸虫的感染强度显著（P<0.05）高于种公马,与其他阶段纯血马相比差异不显著（P>0.05）。10月哺乳马驹马副蛔虫、毛圆线虫、裸头绦虫感染强度显著（P<0.05）高于除繁殖母马以外的其他年龄段纯血马,细颈三齿线虫感染强度显著（P<0.05）高于其他年龄段纯血马,马球虫和埃氏腹盘吸虫的感染强度显著（P<0.05）高于种公马。种公马马副蛔虫与细颈三齿线虫感染强度显著（P<0.05）低于其他阶段的纯血马。不同年龄段纯血马马蛲虫感染强度差异不显著（P>0.05）。结论 纯血马感染的肠道寄生虫主要有马蛲虫、马球虫、毛圆线虫、细颈三齿线虫、盅口线虫、马副蛔虫、裸头绦虫以及埃氏腹盘吸虫,不同年龄段、不同月份均有感染,且混合感染较为严重。哺乳马驹感染强度及感染率普遍高于其他年龄段纯血马。  相似文献   

12.
A possible role of breeding activities in the composition of the microbial population in stallions' external genitalia (EG) and the relationship between micro‐organisms colonizing the skin of the abdomen and the ones colonizing the EG have not been studied. In experiment 1, EG microbiological samples were collected from 41 stallions used for both natural cover and semen collection (BST) and from 18 non‐breeding stallions (NBST). A higher (p < 0.05) frequency of isolation of potentially pathogenic species was found for BST. Age did not influence number of micro‐organism species isolated both in BST and NBST. In experiment 2, the microbial content of the EG and semen was compared in 23 BST. Most micro‐organisms isolated from the EG were present in semen, albeit with a numerically lower prevalence. In 7 stallions, six microbial species isolated from semen were absent from the EG cultures, suggesting contamination by the operator. In experiment 3, a numerically higher number of micro‐organism species was isolated from the EG of 31 stallions, than from their skin of the ventral abdomen in contact with the penis or from the skin of the thorax. With the sole exception of Escherichia coli, potentially pathogenic bacteria were only isolated from the EG but not from the skin. Results suggest that breeding activity increased the number of species colonizing the EG; most species isolated from the EG were also found in semen even if with a lower frequency, and additional semen contamination seemed to occur during its manipulation. Many micro‐organism species of the skin were also isolated from the penis, but independently of being or not in contact with the penis, skin did not seem to provide an adequate environment for the growth of potentially pathogenic bacteria that were isolated from EG, with the sole exception for E. coli.  相似文献   

13.
Conception rates for mares bred with transported-cooled and fresh stallion semen were collected over a 4-yr period (1998–2002) for two stallions. Both stallions stood at a commercial breeding farm. Semen from both stallions was used immediately after collection on the farm and after 24 to 48 h of cold storage when transported to locations in the U.S. and Canada. Semen for insemination of mares located on the farm was extended with a commercially available skim milk glucose extender (SKMG). Spermatozoal motility following cold storage for spermatozoa diluted in SKMG extender was unacceptable. Thus, semen from both stallions was centrifuged, and spermatozoa were resuspended in SKMG supplemented with modified PBS. In a previous study, the percentage of motile spermatozoa increased following centrifugation and reconstitution of the sperm pellet in SKMG-PBS as compared with semen dilution in SKMG (Stallion A: 15% vs 47%; Stallion B: 18% vs 43%). In the current study, 22 of 25 (88%) and 3 of 4 (75%) mares conceived with transported-cooled semen from Stallions A and B, respectively. Conception rates for mares inseminated with transported semen did not differ (P>0.05) from those inseminated on the farm with fresh semen. These data illustrate that stallion owners can modify standard cooled semen processing procedures and semen extender composition to improve post-storage spermatozoa motility and to obtain acceptable fertility.  相似文献   

14.
Sperm concentration and sperm membrane intactness (SMI) or viability are two measures of sperm quality that provide important but different information about a stallion's reproductive capability. Sperm concentration is a measure that, by itself, informs little about the reproductive status of either the stallion or the ejaculate. Nevertheless, it is part of the product, along with semen volume, that determines total sperm number. The correct calculation of total sperm number directly affects the number of mares a stallion can breed and therefore, fertility. If either sperm concentration or semen volume is incorrectly measured, both the number of mares that a stallion can breed and the fertility of those breedings are affected. Although considerable between-stallion variation exists, sperm concentration, semen volume and total sperm number tend to be seasonal and vary with ejaculation frequency.  相似文献   

15.
In our experience, the testicular dysfunction that develops in aged stallions is typically progressive, contributing to a gradual deterioration in sperm output and quality over 2-4 years. As the ability to produce sufficient numbers of normal sperm in ejaculates declines, so do pregnancy rates until the stallion eventually becomes so subfertile that it is no longer commercially feasible to continue breeding. However, more intensive breeding management can sometimes result in pregnancy rates (per cycle and per season) that are sufficient to justify breeding of the aged stallion to a diminishing number of mares during the period of declining fertility.  相似文献   

16.
Microbial culture from a double-guarded culture swab is commonly used to diagnose infectious endometritis. The objective of this study was to develop a quantitative polymerase chain reaction (qPCR) assay to detect a broad range of bacteria from equine uterine samples. Twenty-seven mares with a clinical history of endometritis had a double-guarded culture swab collected for analysis by qPCR and microbial cultures. An additional 12 mares had a uterine biopsy sample collected for qPCR analysis, microbial culture, and histopathology. Subsequently, a double-guarded culture swab for microbial culture and a cytology brush sample were also collected. The qPCR assay detected bacterial DNA in nine of 27 mares from a double-guarded swab and six of 12 mares from an endometrial biopsy. Positive microbial growth was detected in nine of 27 mares and four of 12 mares from a double-guarded culture swab. Bacterial DNA was detected in two of 27 mares and two of 12 mares without subsequent microbial growth. The simple presence of an organism's DNA allows for detection by nonculture-based systems, both live and dead organisms can be identified. In conclusion, the qPCR assay was determined to be a sensitive diagnostic technique for identifying pathogens associated with infectious endometritis. The primary application of the qPCR assay is detection of potential pathogenic bacteria in the uterus of a mare suspected of having infectious endometritis when a traditional microbial culture is negative. Further work is warranted to determine if mares positive for bacterial DNA and negative for microbial culture are affected clinically.  相似文献   

17.
A 7-year-old thoroughbred stallion presented with severe colic, which was resolved surgically. On postsurgical palpation and rectal ultrasonography, the left seminal vesicle was enlarged, the left testicle and epididymis showed signs of inflammation with hydrocele. Antibiotics and anti-inflammatory treatment were administered. Fever and colic syndrome recurred, with severe inflammation of the left testis and epididymis, and unilateral orchiectomy was performed. Histopathological diagnosis confirmed chronic orchioepididymitis, and Klebsiella pneumoniae was identified and typed from all cultures. At breeding soundness examination 2 months after treatment with ceftiofur, K. pneumoniae was again isolated, and cytology revealed degenerated polymorphonuclear cells and red blood cells. Transurethral endoscopic examination was used to locate the infection in the left seminal vesicle, and ticarcillin-clavulanic was locally infused for 10 days. Nevertheless, the pathogen was once again isolated in the ejaculate, and the affected seminal vesicle was again treated locally for 5 consecutive days, using imipenem-cilastatin, a new antibiotic showing high sensitivity. Follow-up breeding soundness examination revealed an improvement in seminal characteristics and no pathogen isolation. Total pregnancy rate (31 of 36; 86%) and first cycle pregnancy rate (18 of 36; 50%) in the last breeding season reached levels similar to those prior to infection (65 of 82; 80% and 47 of 82; 57% respectively), suggesting that local treatment with imipenem-cilastatin in stallions with seminal vesicle infections is effective and, in this case, did not produce any adhesions or other undesirable effects, permitting the stallion to resume breeding with no apparent deleterious effect on fertility despite having only one testicle.  相似文献   

18.

Background

Pseudomonas aeruginosa may cause venereal disease and infertility in horses. A Pseudomonas aeruginosa - carrier stallion, often unresponsive to artificial vagina collection, was used to naturally breed mares. Semen collected from the same stallion was also used to perform artificial inseminations. Pregnancy rates, embryo quality and incidence of uterine infection were compared between inseminated or naturally-bred mares.

Methods

P. aeruginosa was isolated from swabbing of the penis, prepuce and distal urethra of the stallion. Before being bred or inseminated, clitoral/vestibular samples were collected from all mares, and cultured for isolation of P. aeruginosa. At the first observed estrus, endometrial swabs were also collected. All mares subjected to natural mating (NS) were re-evaluated for P.aeruginosa by culture of clitoral and endometrial swabs. Artificial inseminations (AI) were performed either with fresh-extended semen (11 AI/7 mares) or frozen semen (10 AI/7 mares). The stallion was also used to breed 3 mares (4 services). For embryo collection, 2 mares were inseminated with fresh-extended semen (1 AI/mare), and 2 additional mares were inseminated with frozen semen (2 AI/mare). Two mares were naturally-bred with a total of 9 services, for embryo collection. All mares were examined after AI or natural service (NS), for uterine pathologies. Embryo recoveries were attempted passing a catheter with inflatable cuff connected to a sterile flexible 2-way flushing catheter, through the cervix. Flushed media was recovered into an Em-Con filter, and embryos searched using a stereoscope. Embryos were graded from 1 (excellent) to 4 (degenerated/dead).

Results

Pregnancy rates obtained after NS was 50% per cycle. However, more than half of the NS resulted in uterine disease, while uterine pathology was seen only in 22% of the time following AI. Half of the mares bred by NS got positive to P. aeruginosa. Percentage of embryo recovery rates was identical after AI or NS (66.7%). The 4 embryos recovered after AI were classified as Grade 1, while after NS only 2 out of the 6 recovered embryos were Grade 1.

Conclusion

a) there was no evidence of reduced fertilization after AI or NS, b) a numerically higher incidence of uterine disease was noticed after NS, c) venereal transmission of P. aeruginosa after NS was confirmed, d) a lower percentage of G1 embryos may be obtained after NS. Overall, the data supports the indication for P. aeruginosa-carrier stallions to be bred by AI rather than by NS, and raises the possibility that P. aeruginosa may affect embryo quality.  相似文献   

19.
Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) is one of the cutting-edge methods currently applied in medical bacteriologic diagnostics. The aim of the study was to prove the possibility of applying MALDI-TOF MS to identify bacterial contamination in the ejaculate of stud stallions, which may cause infections to reproductive organs of mares following artificial insemination with cooled semen. A partial aim was to determine changes in the total count of microorganisms in long-term storage of ejaculate after its treatment with gentamicin and also without antimicrobial medication. Aerobic cultivation on Columbia agar was used to examine 26 semen samples from 13 horses; 31 different species of bacteria were isolated, which were identified by MALDI-TOF MS. The most frequently detected species came from Aerococcaceae, Staphylococcaceae, and Micrococcaceae families. The results of our work confirm that MALDI-TOF MS is a quick alternative method for identifying bacterial species that may contaminate stallion semen.  相似文献   

20.
The equine virus arteritis (EVA) consistently epidemically varying throughout the different breeds of the horse breeding countries is up to now only of lower significance by means of the typical clinical manifestation as well as an abortion causing factor. The susceptibility of the sexual mature stallions against the equine arteritis virus (EAV) causes different infection response which may lead to some restrictions in their use in natural breeding especially in the artificial insemination. In a certain not precisely predictable part of the stallion population EAV infection will cause a transient or permanent virus presence in the accessorial apparatus of the genital tract with transient or permanent shedding of the virus via seminal secretions. This makes the stallion to one of the dominant factors of the propagation of the field virus. The use of EAV shedding stallions in natural breeding or AI is very risky and only justifiable under certain precautions and additional measurements e.g. in EAV-seropositive or vaccinated mares. A consistent progress in the defeat of the disease can be expected from vaccination of the seronegative stallions with dead or inactivated live vaccines as they are considered to be able to prevent the establishing of EAV shedder status.  相似文献   

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