Search Results

You are looking at 11 - 18 of 18 items for :

  • "colostrum" x
  • Microbiology x
  • Refine by Access: All Content x
Clear All

SUMMARY

The infectivity and pathogenicity of selected bovine viral diarrhea virus (bvdv) isolates were determined in gnotobiotic, colostrum-deprived neonatal lambs. Five-day-old cesarean-derived gnotobiotic lambs were exposed to 1 of 10 bvdv. isolates via aerosol suspension. These isolates were from tissues or secretions of calves or lambs affected with respiratory tract disease, weak neonatal calves, aborted bovine fetuses, or reference Singer or Draper bvdv. The pathogenicity of each isolate, relative to the others, was evaluated in lambs by measurement of the neutralizing antibody response, virus isolation from nasal secretions or tissues, and postmortem lesions. The bvdv isolates varied in their infectivity and pathogenicity. Singer, the cytopathic reference strain, was the most lymphotrophic isolate and stimulated the greatest neutralizing antibody response. Encephalitis was the most consistent lesion observed and was used as the final determinant of relative pathogenicity of the viruses. The most neuropathogenic isolates were the 2 viruses originating from lambs affected with respiratory tract disease, the 2 weak neonatal calf isolates, and 1 isolate from an aborted bovine fetus. The least pathogenic isolates were the 2 reference isolates, Draper and Singer; the 2 mucosal disease isolates; and 1 isolate originating from an aborted bovine fetus.

Free access
in American Journal of Veterinary Research

SUMMARY

Objective

To determine the effect of congenital and early postnatal infection of pigs with porcine reproductive and respiratory syndrome virus (PRRSV) on postnatal survival and growth.

Animals

20 pregnant gilts and their pigs and fetuses.

Procedure

16 pregnant gilts (principals) comprising 4 groups (4 gilts/group) were exposed oronasally to 4 strains of PRRSV (a vaccine strain, and 3 field strains) at or about day 90 of gestation. Four pregnant gilts (controls) were kept under similar conditions, except for exposure to PRRSV. Samples collected from pigs before ingestion of colostrum and samples and specimens collected from pigs at selected times thereafter were tested for PRRSV and homologous antibody. Pigs were observed for clinical signs and were weighed at birth and at weekly intervals until they were euthanatized and necropsied at about 3 weeks of age.

Results

At least some members of all litters of principal gilts were infected congenitally. Most noninfected, liveborn littermates became infected within the first week of life. Infection of pigs with field strains did, and infection of pigs with the vaccine strain did not, adversely affect postnatal survival and growth rate. All infected pigs had generalized lymph node enlargement.

Conclusion

Exposure of pregnant gilts to either attenuated (vaccine) or virulent (field) strains of PRRSV can result in congenital infection. Vaccine as well as field strains can be transmitted postnatally from infected to noninfected littermates. Pigs infected with field strains have a poorer rate of survival and growth than do noninfected pigs.

Clinical Relevance

Because attenuated (vaccine) PRRSV can cause congenital infection and be transmitted postnatally from congenitally infected to immune-naive pigs, the use of attenuated virus during gestation is, at best, questionable. (Am J Vet Res 1998;59:52–55)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine the pathogenic potential of an adenovirus isolated from a goat.

Animals

14 colostrum-deprived, isolation-reared goat kids approximately 3 weeks old.

Procedure

Kids were inoculated with either cell culture fluid containing adenovirus (n = 10) or uninfected cell culture fluid (n = 4): 2 ml transtracheally and 1 ml/nostril. Clinical signs of disease and rectal temperature were recorded daily; nasal secretion and fecal specimens were collected daily. Control kids were necropsied, 2/d, on postinoculation days (PID) 5 and 10. Virus-inoculated kids were necropsied on PID 3, 5, 7, 10, and 28. After necropsy, lung, liver, kidney, and brain specimens were aseptically collected for virus isolation attempts. Tracheal fluid was collected on sterile cotton swabs. Turbinate, trachea, lung, mediastinal lymph node, liver, kidney, duodenum, jejunum, ileum, mesenteric lymph node, colon, and brain specimens were collected for histologic evaluation.

Results

Kids developed mild-to-moderate clinical respiratory tract infection. Virus was recovered consistently from nasal secretion and sporadically from fecal specimens. Grossly, there were multiple areas of atelectasis and hyperemia, principally in the cranioventral portion of the lungs. Microscopically, there was detachment and sloughing of foci of epithelial cells of the terminal bronchioles and alveoli. In kids necropsied late in the disease, these changes were accompanied by hyperplasia of type-II epithelial cells. Viral inclusions were not an obvious feature, but a few cells contained probable inclusions.

Conclusions and Clinical Relevance

The caprine adenovirus reported here is capable of inducing respiratory tract disease and lesions in the lungs of young kids. (Am J Vet Res 1997;58:608–611)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To compare the virulence of selected strains of porcine reproductive and respiratory syndrome virus (PRRSV) relative to reproductive performance of pregnant gilts.

Design

16 pregnant gilts (principals) were exposed oronasally to 4 strains (vaccine strain RespPRRS, field strains VR-2385, VR-2431, and NADC-8, 4 gilts/strain) of PRRSV on or about day 90 of gestation. 4 pregnant gilts (controls) were kept under similar conditions, except for exposure to PRRSV. Samples and specimens obtained from gilts, pigs (before ingestion of colostrum), and fetuses were tested for PRRSV and homologous antibody.

Animals

20 pregnant gilts.

Procedure

The virulence of each strain of PRRSV was evaluated mainly on the clinical status of the corresponding litters at farrowing.

Results

Most gilts remained clinically normal throughout the study and farrowed normally at or near the expected farrowing time. All virus strains crossed the placenta of principal gilts to infect fetuses in utero. The number of late-term dead fetuses (which appeared to be the best measure of relative virulence) ranged from 0 for litters of control gilts and gilts exposed to strain RespPRRS, to 38 for gilts exposed to strain NADC-8. All principal gilts became viremic and developed antibody against PRRSV. All strains persisted in alveolar macrophages of at least some principal gilts for at least 7 weeks after exposure.

Conclusion

Strains of PRRSV vary in virulence.

Clinical Relevance

The effects of PRRSV on reproductive performance are strain dependent and this should be considered in making a tentative diagnosis on the basis of clinical observations. (Am J Vet Res 1996;57:834–839)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To test the ability of porcine respiratory coronavirus (PRCV) to induce protective immunity to antigenically related transmissible gastroenteritis virus (TGEV) in neonatal pigs.

Design

Neonatal pigs were exposed to PRCV when they were 2, 4, or 6 days old and challenge-exposed to virulent TGEV at 10 days of age.

Animals

34 hysterectomy-derived, colostrum-deprived pigs.

Procedure

After challenge exposure, clinical signs were observed, body weight, antibody response, and virus shedding were measured, and mortality was determined.

Results

After exposure to PRCV, principals had a slightly slower rate of weight gain than did controls; with 1 exception (a PRCV-exposed pig that was dyspneic for 1 day), principals and controls remained clinically normal until shortly after challenge exposure, when all pigs became listless and anorectic and developed watery diarrhea. However, by day 3, most of the pigs that had been exposed to PRCV when they were either 2 or 4 days old began to recover and most (15/18) survived. Conversely, the clinical condition of most of the other pigs worsened and most (14/16) died. Pigs exposed to PRCV when they were 2 or 4 days old also differed from all other pigs in that they had serum virus-neutralizing antibodies for PRCV and TGEV at the time of challenge exposure.

Conclusions

The PRCV can induce protective immunity to TGEV in neonatal pigs and such immunity develops at or about 6 days after exposure to PRCV. Moreover, protective immunity may be coincident with the appearance of virus-neutralizing antibody.

Clinical Relevance

Exposure to PRCV should enhance a TGE herd vaccination program.

Free access
in American Journal of Veterinary Research

Summary

To determine whether intrauterine transmission of Borrelia burgdorferi could exist in dogs, 10 female Beagles were inoculated intradermally with approximately 1,000 B burgdorferi on day 1 of proestrus; inoculation was repeated every 2 weeks during the gestation period. Ten female control Beagles were similarly inoculated with phosphate-buffered saline solution. Prior to the start of the study, all females and 3 males used for breeding were seronegative for B burgdorferi on the basis of results of the indirect fluorescent antibody test and immunoblot (western blot) analysis. Similarly, results of culture of blood for B burgdorferi were negative. All 20 of the females were bred naturally. Blood samples were collected weekly for serologic testing and culture. Blood samples were obtained from live pups on day 1 of life, then weekly until pups were 6 weeks old when they were euthanatized. Tissues were obtained for culture and testing by use of polymerase chain reaction (pcr). Of 10 spirochete-inoculated (si) females, 8 became infected with B burgdorferi as evidenced by spirochete culture results and/or pcr-detected B burgdorferi dna in the tissues of females or their pups. Of the 10 si females, 8 delivered litters (3 to 7 pups) that had at least 1 neonatal or 6-week-old pup with B burgdorferi dna-positive tissues (by pcr), and spirochetes were cultured from tissues from pups of 2 litters. Four pups of 3 separate litters (a stillborn, a neonate that survived to 30 minutes of age, a 20- hour-old, and a 48-hour-old) had B burgdorferi-positive tissues (by pcr), and the 20-hour-old pup was also culture-positive, indicating intrauterine infection. Further evidence of intrauterine exposure was the presence of IgM antibodies to B burgdorferi detectable by western blot in 3 of 7 one-day-old pups that did not receive colostrum, indicating a primary immune response. Eight of 10 si females and 10 of 10 control females carried litters to term. Differences between si and control Beagles were seen in the duration of gestation, number of resorptions, and number of dystocias. All control females and pups remained seronegative, culture-negative, and B burgdorfer-inegative throughout the study.

Intrauterine infection by B burgdorferi does occur in dogs and is a potential means by which the spirochete can be transmitted in a breeding population in the absence of a tick vector.

Free access
in American Journal of Veterinary Research

Summary

Pregnant sows, immune against pseudorabies after vaccination, were inoculated at 70 days of gestation either with autologous blood mononuclear cells that had been infected in vitro with pseudorabies virus (prv) or with cell-free prv. The infected cells or cell-free prv were inoculated surgically into the arteria uterina.

Eight sows (A to H) had been vaccinated with an inactivated vaccine. The titer of seroneutralizing antibodies in their serum varied between 12 and 48. Five sows (A to E) were inoculated with autologous mononuclear cells, infected either with a Belgian prv field strain or with the Northern Ireland prv strain NIA3. These 5 sows aborted their fetuses: 2 of them (B and C) 3 days after inoculation, and the other 3 (A, D, and E) 10, 11, and 12 days after inoculation, respectively. Sows F, G, and H were inoculated with a cell-free prv field strain. They farrowed healthy litters after normal gestation. Neutralizing antibodies were absent against prv in the sera of the newborn pigs, which were obtained prior to the uptake of colostrum.

The 23 fetuses that were aborted in sows B and C 3 days after the inoculation were homogeneous in appearance and size. Foci of necrosis were not detected in the liver. Viral antigens were located by immunofluorescence in individual cells in lungs, liver, and spleen of 15 fetuses. Virus was isolated from the liver, lungs, or body fluids of 12 fetuses.

The 39 fetuses that were aborted in sows A, D, and E between 10 and 12 days after inoculation were of 2 types: 17 were mummified and 22 were normal-appearing. Foci of necrosis were found in the liver of all mummified fetuses and 13 of the normal-appearing fetuses. In fetuses with foci of necrosis in the liver, viral antigens were located in groups of cells in the liver, lungs, and spleen. Virus was isolated from 16 normal-appearing fetuses and from 11 mummified fetuses.

Pseudorabies virus was isolated from vaginal excretions of sows A and D until 1 and 2 days after abortion, respectively, and of sows B and C until 4 and 5 days after abortion, respectively. Virus was not isolated from sow E.

It was concluded that prv can reach the uterine and fetal tissues, via infected mononuclear cells, in the presence of circulating antibodies induced on vaccination. This cell-associated spread led to abortion. Cell-free virus did not induce abortion under similar circumstances.

Free access
in American Journal of Veterinary Research

Summary

Genetically altered stable nonreverting aromatic-dependent (aro -) Salmonella dublin, strain SL5631, was administered orally to healthy colostrum-fed calves as vaccine. Twenty-six calves were allotted to 4 groups. There were 2 experiments, each with a vaccinated and nonvaccinated control group. Skin testing with 0.1 ml of sonicated S dublin was performed 3 days prior to challenge exposure. The IgG and IgM titers to S dublin lipopolysaccharide (lps) antigen were determined by elisa on sera before initial vaccination and at 1.5 to 2 weeks after each vaccination.

In experiment 1, six calves received a dose of 1.7 × 1010 colony-forming units (cfu) of aro-S dublin SL5631 orally at 2 and 4 weeks of age. After the first vaccination, 2 of 6 calves developed fever, but all 6 calves continued to have normal appetite and mental attitude. Adverse changes were not observed after the second vaccination. At the time of challenge exposure at 6 weeks of age, all 12 calves were seronegative for IgG and IgM lps-specific antibodies, and the difference in percentage increase in skin test reaction at 48 hours was not significant. At 6 weeks of age, the 6 vaccinates and 6 controls were orally challenge-exposed with 1.5 × 1011 cfu of virulent S dublin T2340. Protection from challenge was not evident, as 3 of 6 controls and 5 of 6 vaccinates died after challenge exposure.

In experiment 2, eight calves received a dose of 5 × 1011 cfu of aro-S dublin SL5631 orally at 2, 3.5, and 5 weeks of age. The vaccine dose and volume (300 ml) were 30 times that of experiment 1. After each vaccination, some calves (7, 6, and 2 calves for first, second, and third doses, respectively) developed fever, but all calves continued to have normal appetite and attitude. At 7 weeks of age, the 8 vaccinates and 6 controls were orally challenge-exposed with 1.5 × 1011 cfu of virulent S dublin T2340 (same dose as experiment 1). At the time of challenge exposure, all 8 vaccinated calves had elisa titers to IgG and IgM lps-specific antibodies significantly above those of nonvaccinated calves (P < 0.01 and P < 0.05, respectively), 5 of 8 had a strongly posisitive skin test reaction to lps, and the group mean percentage increase in skin thickness 48 hours after intradermal injection was 135% (P = 0.01). The 6 control calves had negative elisa results and mean increase in skin thickness of 34%. Protection from challenge exposure was evident as vaccinates remained blood culture-negative, whereas 5 of 6 controls were blood culture-positive; vaccinates did not develop diarrhea, whereas all controls developed diarrhea. All vaccinates survived, but 3 of 6 controls died after challenge exposure (P = 0.05).

Failure of orally administered vaccine to protect calves in experiment 1 appeared attributable to insufficient antigenic stimulation when 1.7 × 1010 cfu of aroS dublin SL5631 was administered. In experiment 2, a larger number of vaccinal organisms given orally was able to induce a measurable systemic immune response and protection, but the vaccine volume makes it unlikely to be practical for field use.

Free access
in American Journal of Veterinary Research