Experimental infection of early pregnant cows with bovine viral diarrhea virus: Transmission of virus to the reproductive tract and conceptus

The objective of this study was to chronologically investigate the effect of bovine viral diarrhea virus (BVDV) infection on early pregnant cows before placenta formation. Six cows were intravenously inoculated with either BVDV (treated, n = 4) or growth medium (control, n = 2) (day 0) at day 26 of pregnancy. Two treated cows and one control cow were euthanized on day 3 post-infection and the remaining animals were euthanized on day 6. BVDV was isolated from maternal tissues such as lymphoid or reproductive tissues of treated animals on days 3 and 6 post-infection. Additionally, one treated cow autopsied on day 6 post-infection had evidence of infectious BVDV in the allantoic membranes, allantoic fluid and embryos. In three treated cows, a significant decline in progesterone concentration was also observed post-infection while in control cows they remained constant. Therefore, BVDV can infect bovine embryos before placenta formation and may affect progesterone profiles in cows during early pregnancy.     

Isolation of pathogenic strains of Haemophilus somnus from the female bovine reproductive tract.

The prevalence of Haemophilus somnus in the genital tract of slaughtered and live cows in southern Ontario was investigated. The vagina and uterus of slaughtered cows were swabbed separately. Live cows were examined and sampled in two field surveys: Centre A and Centre B. In the former, aspirated mucus secretions and in the latter, specimens obtained by guarded swabbing were examined bacteriologically. Haemophilus somnus was isolated from 28 genital tracts of 461 slaughtered (6.1%), and seven of 199 live (3.5%) cows during the centre B survey. The isolates were recovered from both normal and diseased reproductive tracts. Fourteen strains isolated from genital organs were examined for pathogenicity in vivo to test the occurrence of pathogenic isolates. In the initial stage of the in vivo study on pathogenicity, each of the fourteen isolates was examined on one calf using an intracisternal inoculation. Subsequently, one pathogenic and one nonpathogenic strain were inoculated into five calves each to statistically confirm their pathogenic potential. Of 14 genital isolates of H. somnus examined in an intracisternal calf assay, six (43%) caused a fatal peracute neurological disease, while eight were nonpathogenic. A comparative pathological study of pathogenic and nonpathogenic isolates showed that the former caused a severe fatal suppurative meningoencephalitis whereas the latter caused no lesions whatsoever or a mild leukocytic leptomeningitis. The salient data obtained in this study indicate that there are pathogenic strains of H. somnus in the genital tract of apparently normal cows as well as of those with inflammatory disease.     

Complement fixation titers in cattle following intranasal inoculation of Hemophilus somnus.

Five bulls were inoculated intranasally with a live culture of Hemophilus somnus originally isolated from a clinical case of Hemophilus septicemia. Preinoculation and postinoculation blood samples were taken at weekly intervals for nine weeks for measuring complement fixation titers and daily postinoculation temperatures were taken for one week. Three animals had transient fever and slight lethargy was observed in two animals had a transitory rise in complement fixation titers in the second to fifth weeks postexposure while one animal which had been seronegative on preinoculation testing produced little serological response to the organism. The experiment demonstrated that the nasal instillation of young cattle using an originally pathogenic H. somnus isolate is capable of stimulating only transitory complement fixation antibody titer.     

Hemophilus somnus in the reproductive tracts of slaughtered cows: location and frequency of isolations and lesions

One hundred bovine female reproductive tracts were examined for the presence of Hemophilus somnus, and fifty were examined for gross and microscopic lesions. H. somnus was isolated from eight of 100 tracts. The isolation was made from the vagina in seven cows. Of 24 tracts in which the major vestibular gland was sampled, three were positive at this site, and two of these three also had the organism isolated from the vagina. Further investigations into the role of the major vestibular gland as a source for continuing infections of the reproductive tract of cattle were indicated. In this investigation, H. somnus was as likely to be found in a region without lesions as one with lesions.     

Inflammation in the bovine female reproductive tract

Inflammation of the reproductive tract of a cow occurs when the physical and functional barriers to contamination are breached or specific infection occurs. Commonly, contamination occurs at parturition and to a lesser extent at estrus. Uterine contamination following calving is common, but most healthy cows are able to clear the uterus of bacteria in the first 2 to 3 wk after calving. Persistent infections are more likely to be caused by Actinomyces pyogenes. Specific venereal infections tend to be more host-adapted and produce a lower grade inflammation. Nonspecific bacterial contamination of the endometrium generally induces a neutrophilic influx into the stratum compactum and uterine lumen. Neutrophils phagocytize bacteria with the aid of opsonins in the uterine fluid. Mast cells and eosinophils may also contribute to the inflammatory reaction, which may damage the surface epithelium and release vasoactive substances that allow leakage of serum antibodies into the uterine secretions. Specific antibodies of immunoglobulin (Ig) isotype A, M, G1, and G2 in uterine secretions have been described. In model species, the immune capability of the uterus is influenced by steroid hormones, especially estradiol, which increases secretory component and both IgA and IgG content in uterine secretions and increases the activity of antigen-presenting cells in the uterus. Similar cyclic fluctuations in immune components have been described for cows, including changes in the population of subsurface cytotoxic and helper T cells and changes in the expression of major histocompatibility II antigen on surface cells.     

Inhibitory effect of the bovine conceptus on lymphocyte stimulation

Experiments were conducted to determine whether the preimplantation bovine conceptus produces an immunosuppressant as measured by the inhibition of lectin-induced incorporation of thymidine into lymphocytes. The results of the experiments clearly indicated that media from cultured 18-d-old embryos inhibited lectin-induced incorporation of thymidine into bovine lymphocytes. The inhibitory substance was not produced by heat-killed cells from the conceptus, was not toxic to lymphocytes, was not lectin-specific, but did act in a partially reversible manner. The inhibitor had no apparent effect on porcine lymphocytes, a moderate effect on ovine lymphocytes and a potent effect on bovine lymphocytes. The substance appeared to have a molecular weight of between 500 and 10,000 and was ether insoluble and heat stable. The possible chemical nature of the inhibitor and its potential effect on survival of the preimplantation conceptus are discussed.     

Haemophilus somnus and reproductive disease in the cow: A review

Haemophilus somnus causes inflammatory disease in the genital tract of cows as reported in several field surveys and experimental trials. This organism can also innocuously colonize the healthy genital mucosa of the cow, which indicates its dual relationship with the host, that of pathogen and commensal. Experimental data indicate embryocidal capability of this pathogen suggesting a possible role in early embryonic death. Haemophilus somnus also causes sporadic abortions after a bacteremia in the dam. Retrograde infection of the pregnant uterus from the lower genital tract appears unlikely; however, this process can account for post-parturient endometritis. Detection of high homologous IgG₂ serum antibody titers using an ELISA test may be useful for the diagnosis of current or recent genital inflammation. Experimental laboratory data indicate that a proportion of genital strains of H. somnus are pathogenic and capable of causing thrombotic meningoencephalitis and perhaps pneumonia. In vivo testing of the pathogenicity of genital strains remains to be conducted.     

Antibody response in the bovine genital tract to intrauterine infusion of Actinomyces pyogenes

Antibody titres and immunoglobulin concentrations were measured in serum and in uterine and vaginal secretions from five heifers after intrauterine infusion of Actinomyces pyogenes. Infection stimulated an increase in uterine antibody titres of IgG2 and IgA, which approached significance. There was no increase in antibody titres in vaginal secretions or in serum. For each class of immunoglobulin, the ratio of specific antibody to immunoglobulin tended to increase in uterine secretions after infection, whereas no change was detected in the serum. These results indicate that at least a portion of the antibody was derived from local uterine synthesis.     

Immunohistochemical study of Hemophilus somnus, Mycoplasma bovis, Mannheimia hemolytica, and bovine viral diarrhea virus in death losses due to myocarditis in feedlot cattle

The purpose of this study was to determine the presence of Hemophilus somnus, Mycoplasma bovis, Mannheimia hemolytica, and bovine viral diarrhea virus (BVDV) in lesional tissues of feeder calves dying with myocarditis. Tissues from the heart and lungs of 92 calves dying with myocarditis in Alberta feedlots were immunohistochemically stained for the antigens of these agents. Tissues from 44 calves dying from noninfectious causes and 35 calves dying with pneumonia were tested as controls. Hemophilus somnus was found in cardiac lesions in the majority of myocarditis cases (70/92). Mycoplasma bovis was concurrently demonstrated in the hearts of 4/92 affected calves. No bacterial pathogens were found in heart tissues from the control groups of calves. Bovine viral diarrhea virus was demonstrated in the tissues of 4/92 myocarditis cases compared with those of 13/35 calves dying from pneumonia and 0/44 calves dying from noninfectious causes. The results demonstrate that H. somnus is the principle pathogen associated with myocarditis in feedlot calves and that the presence of BVDV is more common in these calves compared with calves dying of noninfectious causes. The findings also suggest that BVDV is an important pathogen in calves dying with gross postmortem lesions of pneumonia.     

A comparative study of bovine and ovine Haemophilus somnus isolates.

Bacterial isolates (including 17 Haemophilus somnus isolates and an H. somnus-like isolate) from asymptomatic or diseased cattle and sheep, were evaluated for markers associated with virulence and host predilection. The isolates were separated into 6 distinct biovariants, 3 for sheep and 3 for cattle, based on reactions in a battery of 21 test media. Three bovine isolates associated with disease caused hemolysis of bovine blood. The rest of the isolates did not hemolyze either bovine or ovine erythrocytes. Protein profiles of all H. somnus isolates were similar with the exception of the major outer membrane proteins (MOMPs). The MOMPs of isolates associated with disease in cattle had a relative molecular weight of approximately 41 kDa compared with 33 kDa for the MOMPs of isolates from asymptomatic cattle. The MOMPs from sheep isolates were either slightly higher or lower than the 41 kDa MOMPs of bovine isolates. Major antigens detected by Western blotting were similar in all isolates except the H. somnus-like isolate. An immunodominant 40 kDa antigen was conserved in all H. somnus isolates. Antibodies to this antigen have previously been found to be protective in cattle and may also be protective for sheep. Marked differences between cattle and sheep isolates were revealed by use of restriction enzyme analysis, which separated the isolates into 12 ribotypes and 15 unique DNA profiles. Thus, cattle and sheep isolates in this collection had distinctive differences in biochemical reactions, MOMP profiles, and DNA analyses. Such differences have potential value for epidemiological studies and may also be used to evaluate host specificity of H. somnus isolates.     

妊娠母羊胆酸灌注对胎儿和新生儿的影响

妊娠期肝内胆汁淤积症(Intrahepatic cholestasis of pregnancy,ICP)是孕妇在妊娠晚期出现的以瘙痒和黄疸为特征的肝病,是一种高危产科疾病,严重影响胎儿的健康.为了更好地研究ICP的发病机制,本试验以妊娠母羊为动物模型,分别通过大剂量(2 mg/kg)和小剂量(1.1 mg/kg)的胆酸盐静脉灌注怀孕后期的母羊,同时进行胎儿血管造瘘手术,目的是研究ICP的发病模型和胆酸对胎儿和新生儿的影响机制.结果显示,给妊娠母羊大剂量多次静脉灌注胆酸盐,引起母体难产,导致胎儿宫内窘迫和死亡;小剂量灌注,导致胎儿的低出生重,但胎儿在出生后15 d时,羔羊的体质量与正常的羔羊没有差异,体现了追赶生长的特性.结果表明以妊娠母羊为动物模型,通过静脉灌注胆酸盐可以作为研究妊娠期肝内胆汁淤积症的疾病模型,为进一步探索ICP发病时胆酸对胎儿的影响机制提供实验依据.     

Effects of dietary L‐arginine supplementation to early pregnant mares on conceptus diameter—Preliminary findings

The importance of the amino acid L‐arginine (ARG) for conceptus growth and litter size has been demonstrated in various species. L‐arginine is part of embryo‐derived polyamines, a substrate for nitric oxide synthase and stimulates protein synthesis by the embryo. In the present study, we have investigated whether dietary L‐arginine supplementation stimulates early conceptus growth in mares. Warmblood mares with singleton pregnancies received either an arginine‐supplemented diet (approximately 0.0125% of body weight, n = 12) or a control diet (n = 11) from days 15 to 45 after ovulation. Diameter of the embryonic vesicle (days 14, 17, 20 of pregnancy) and size of the embryo respective foetus (length and maximal diameter, days 25–45 of pregnancy at 5‐day intervals) were determined by transrectal ultrasound. At foaling, weight and size of the foal and the placenta were determined. Blood for determination of equine chorionic gonadotrophin (eCG) and progestin concentrations was collected repeatedly. Neither eCG nor progestin concentration in plasma of mares differed between groups at any time. No effects of arginine treatment on diameter of the embryonic vesicle between days 14 and 20 of pregnancy were detected. Diameter of the embryo/foetus on days 40 to 45 of pregnancy strongly tended to be enhanced by arginine supplementation (p = 0.06). Weight and size of neither the foal nor placenta at birth differed between groups. In conclusion, L‐arginine supplementation was without negative effects on early equine embryos and may support embryonic growth at the beginning of placentation.     

Ultrasonographic appearance of the bovine conceptus from days 10 through 20

The bovine conceptus was monitored in 19 heifers by intrarectal ultrasonic imaging from the day an embryonic vesicle was first detected (mean, day 11.7 +/- 0.4; range, days 10 to 17) until detection of the embryo proper (mean, day 20.3 +/- 0.3). Fifteen heifers maintained the conceptus and 4 heifers apparently lost the conceptus. In the heifers that maintained the conceptus, 73% of the embryonic vesicles were classified as spherical (mean diameter, 2.8 +/- 0.2 mm) and 27% were classified as oblong (mean dimensions, 2.0 +/- 0.0 mm and 4.5 +/- 1.0 mm) on the day of first detection. All vesicles were in the uterine horn ipsilateral to the corpus luteum. The vesicles increased in length from the day of first detection. On the average, the vesicle occupied all of the ipsilateral uterine horn on day 16.9 +/- 0.6 and all of the contralateral horn on day 19.6 +/- 0.9. During elongation, the vesicle remained at an approximate height of 2 mm throughout its length, but developed a localized enlargement or bulge on mean day 19.7 +/- 0.2. The embryo proper was detected within the bulge in all 15 heifers. A heartbeat (mean, 188 +/- 4.8 beats/min) was detected on the first day of detection of the embryo proper (8 heifers) or on the following day (7 heifers). The mean length of the interovulatory interval in the 4 heifers that apparently lost the embryonic vesicle was not significantly different from that of nonbred heifers. The vesicles were lost (not ultrasonographically detectable) on days 17 (2 heifers) and 19 (2 heifers).(ABSTRACT TRUNCATED AT 250 WORDS)     

Ultrasonographic appearance of the bovine conceptus from days 20 through 60

The ultrasonographic appearance of the conceptus on days 20 to 60 was determined by daily examinations in 15 heifers. The mean length of the embryo proper increased from the day of first detection (day 20.3 +/- 0.3; 3.8 +/- 0.3 mm) to day 60 (66.1 +/- 1.7 mm). The growth curve was quadratic, with an increasing growth rate after approximately day 50. The embryo initially had the appearance of a short, straight line and developed a C shape on day 25.4 +/- 0.8 and an L shape on day 32.7 +/- 1.1. The average day of first detection of various structures was as follows: allantois, 23.2 +/- 0.3; spinal cord, 29.1 +/- 0.5; forelimbs, 29.1 +/- 0.3; amnion, 29.5 +/- 0.5; optic area, 30.2 +/- 0.4; hindlimbs, 31.2 +/- 0.3; placentomes, 35.2 +/- 1.0; optic lens, 40.0 +/- 0.6; split hooves, 44.6 +/- 0.7; fetal movements, 44.8 +/- 0.8; and ribs, 52.8 +/- 0.5. Embryonic death, as indicated by cessation of heartbeats, occurred in one heifer on day 26. The embryonic mass increased in echogenicity and was maintained with a gradually decreasing fluid volume until the occurrence of estrus 17 days after death.     

Effects of deficiency and surplus dietary threonine on reproductive performance of primiparous pregnant gilts

Dietary threonine imbalance is known to impair reproductive performances of gestating sows, but the underlying mechanisms are largely unknown. In this study, effects of deficiency and surplus dietary threonine during gestation on reproductive performance, serum metabolites and hormones concentration, and colostral nutrient and immunoglobulin contents of primiparous sows were investigated. Ninety primiparous pregnant gilts were assigned to one of the three dietary treatments with different standardized ileal digestible threonine/lysine ratios at 0.59, 0.72 and 0.85, which represented deficient (DT), adequate (AT) and surplus (ST) dietary threonine concentration respectively. Maternal body weight gain from day 80–110 of gestation was highest (p < .05) for gilts fed AT than for gilts fed DT or ST. On days 30 and 110, serum threonine concentration increases in a dose‐dependent manner with the increasing of dietary threonine concentration in (p < .01), serum urea nitrogen concentration was lower (p < .01) in gilts fed AT than DT or ST, and serum insulin‐like growth factor‐I (IGF‐I) was lowest (p < .05) for gilts fed DT. On day 110, gilts fed AT had lower serum progesterone concentration but higher concentrations of serum prolactin (p < .05) compared to DT and ST. Concentration of colostral immunoglobulin A and G from gilts fed DT was lower (p < .05) compared with gilts fed AT or ST. In conclusion, gilts with the adequate threonine intake were more able to conserve dietary amino acids to support foetal and maternal tissue gain. Deficient or ST threonine intake may induce a delay in changes in progesterone and prolactin concentrations during the prepartum period impeding the transition from pregnancy to lactation.     

Relationship between estrous behavior in pregnant mares and the presence of a female conceptus

Unsolicited reports of estrous behavior in mares thought to be pregnant were received from owners or caretakers of Arabian mares. Estrous behavior was confirmed and mares were examined for pregnancy. Gender of the conceptus was determined at foaling in 11 mares in which estrous behavior was confirmed while an apparently viable, ultrasonically normal-appearing conceptus was present. In 9 mares in which the day of ovulation was known (Day 0), the estrous behavior occurred on Day 12, 13 or 14 (5 mares), Day 18 or 20 (2 mares), Day 40 (1 mare) and Day 60 (1 mare). In another study, 55 pony mares were observed for estrous behavior every 3 days for 20 minutes during Days 11 to 40. Estrous behavior was observed in 1 mare (2%) on Day 24. Combined for the 2 studies, the incidence of a female conceptus (12/12) was greater (P<0.01) than the incidence of a male conceptus (0/12) in mares that exhibited estrous behavior.