Protection against bovine respiratory syncytial virus challenge following a single dose of vaccine in young calves with maternal antibody

Twenty-one young calves with maternally derived antibody to bovine respiratory syncytial virus (BRSV) were divided into three groups of seven, each group balanced for BRSV antibody titre. The calves had no evidence of previous exposure to BRSV. The calves in one group were given a single dose of a monovalent modified live BRSV vaccine; the calves in the second group were given a single dose of an inactivated combined BRSV, parainfluenza virus type 3, Mannheimia haemolytica vaccine and the calves in the third group were left as unvaccinated controls. Three weeks after the single doses of vaccine, all the calves were challenged with BRSV. The clinical signs of disease were mild, and virus excretion was limited to two calves in the group given the inactivated vaccine, compared with six in the negative controls (P = 0.05) and five in the group given the live vaccine. The mean virus excretion titres after the challenge were not significantly different between the groups. There was little seroconversion before the challenge, but six of the seven calves in the group given the inactivated vaccine showed significant seroconversion within two weeks after the challenge, compared with only one calf in each of the other two groups (P = 0.015).     

Transfer of maternal antibody against group A rotavirus from sows to piglets and serological responses following natural infection

An enzyme-linked immunosorbent assay (ELISA) was developed for the measurement of antirotaviral antibody in sera and faeces from pigs and used to study the dynamics of antirotaviral antibody responses in three cohorts of pigs. Piglets acquired antirotaviral antibody by sucking their dams soon after birth. Antirotaviral antibodies of IgA and IgG classes were detected in both colostrum and milk of all sows tested but IgM class antibodies were not. The antibody levels in colostrum were eight to 32 times higher than those in milk which was collected 18 days post partum. The levels of antibody in piglets' sera were comparable to those in colostrum but declined quickly to low levels by one month old. Maternal antibody was also detected in the faeces of piglets up to 18 days old. Natural rotavirus infection occurred in each of these cohorts when the geometric mean ELISA titres of maternal antibody in their sera declined to 1/1600 (by days 21, 25 and 30 for cohorts 1, 2 and 3, respectively). However, a positive correlation was not obtained between the levels of antirotaviral antibody and protection in individual litters within each of the cohort groups. In each of the cohorts, rotavirus infection usually occurred in one or two piglets first and then spread to other piglets in the same cohort. It is therefore suggested that maternally derived antibody is protective against rotavirus infection in piglets only for the first one or two weeks. Following natural infection with rotavirus, increases in serum antibodies were detected in two of the three cohorts by 20 to 30 days after the average time of onset of faecal shedding of virus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Antibody levels and protection to canine parvovirus type 2

The relationship between maternally derived antibody (MDA) levels and protection to canine parvovirus (CPV) infection in pups is reported. Twelve pups with a wide range of haemagglutination inhibiting (HI) titres of MDA to CPV were divided into four groups, with each group balanced for antibody titres. The dogs were inoculated with a field CPV-2b strain and clinical signs, virus shedding and antibody response were assessed. The CPV was not detected in the faeces of dogs with HI titres of 320 at any time. In dogs with HI titres up to 160, active CPV replication after challenge was demonstrated by real-time polymerase chain reaction. The successful infection of dogs with HI titres of 80 and 160 was confirmed by seroconversion, evaluated at day 14 post-infection. These findings demonstrated that CPV infection could also occur in the presence of MDA HI titres (> or =80) usually considered fully protective.     

Evaluation of efficacy of an inactivated vaccine against bovine respiratory syncytial virus in calves with maternal antibodies

OBJECTIVE: To assess short- and long-term efficacy of an inactivated bovine respiratory syncytial virus (BRSV) vaccine administered i.m. to calves with maternally derived antibodies. ANIMALS: 28 two-week-old calves with neutralizing, maternally derived antibodies against BRSV. PROCEDURE: For evaluation of short-term efficacy, 6 calves were vaccinated i.m. at 2 and 6 weeks of age and challenged intranasally and intratracheally along with a matched group of 4 unvaccinated control calves at 10 weeks of age. For evaluation of long-term efficacy, 2 groups of 6 calves each were vaccinated i.m. at 2, 6, and 18 weeks of age or 14 and 18 weeks of age; these calves were challenged intranasally and intratracheally along with 6 matched unvaccinated control calves at 43 weeks of age. Serum virus neutralizing antibody titer, clinical reactions, and virus shedding in nasal mucus and lung washings were assessed. RESULTS: None of the vaccination regimens resulted in a significant increase in serum virus neutralizing antibody titer. As judged by virus shedding in nasal mucus and lung washings, vaccinated calves were protected against challenge, compared with unvaccinated control groups. Clinical signs attributable to challenge were coughing (short-term efficacy study) and tachypnea and dyspnea (long-term efficacy study). The severity and incidence of disease were significantly lower in the vaccinated groups, compared with that in the unvaccinated groups. CONCLUSIONS AND CLINICAL RELEVANCE: Through vaccination, it is possible to protect vulnerable calves with maternal antibodies against BRSV infection and reduce respiratory tract disease.     

Measurement of faecal corticoid metabolites in domestic dogs

In the present study we established a method for the determination of faecal glucocorticoid metabolites in dogs and then used the assay to evaluate the adrenocortical activity in 12 dogs divided into two groups. In group A faecal samples were collected at their domestic setting. In group B, faecal samples were collected at home prior to transport to a boarding kennel, where faecal samples were then collected. In faecal samples most of the steroids were extracted with methanol and determined using a radioimmunoassay with an anti-cortisol antibody. Dogs in group A did not show any statistically significant inter-day variations in the basal levels of faecal corticoid metabolites. Faecal corticoid metabolites in dogs in group B were significantly higher on the first day at the kennel compared to animals kept at home. The peak concentration was found after 24 hours and followed by a slow decline. These results suggest that extraction with methanol and dosage with an anti-cortisol antibody by radioimmunoassay represents a valid approach technique for determination of faecal glucocorticoid metabolites and accurately reflects adrenocortical activity.     

THE SEROLOGICAL RESPONSE OF CHICKENS TO AUSTRALIAN LENTOGENIC STRAINS OF NEWCASTLE DISEASE VIRUS

SUMMARY: Australian lentogenic Newcastle disease viruses were evaluated as uninactivated vaccines in Australian chickens, the response being evaluated by the production of haemagglutination-inhibition (HI) antibodies. Two viruses, V4 and PM9, induced high levels of antibody and were readily transmissible between chickens by contact exposure. Three other viruses were poorly immunogenic and poorly transmissible. Chickens vaccinated intramuscularly with the V4 strain produced higher HI antibody titres than chickens vaccinated by the orotracheal, intranasal and intraocular routes. HI antibody titres in chickens vaccinated with the V4 strain reached peak levels 3 to 5 weeks after vaccination and waned considerably during the next 2 to 4 weeks. However, low levels of HI antibody persisted for at least 36 weeks after vaccination. Intramuscular vaccination with the V4 strain of one-day-old chicks lacking maternal antibody to Newcastle disease virus resulted in 42–70% mortality and the survivors developed very high titres of HI antibody. Similar chickens inoculated orotracheally showed signs of depression and developed high titres of HI antibody, but there were no mortalities. Chickens 1-, 2-, 3- and 4-weeks-old and lacking maternally derived HI antibody to Newcastle disease virus suffered no adverse reaction to intramuscular or orotracheal vaccination. The antibody response of the 1-week-old chickens was considerably poorer than that of the older chickens. Following orotracheal vaccination with the V4 strain, chickens with low levels of maternally derived antibody responded with low levels of HI antibody. On the other hand, in the progeny of hens hyperimmunised with the V4 strain the production of active antibody following orotracheal vaccination was delayed until the level of passive antibody had declined considerably. There was no response to intramuscular vaccination in congenitally hyperimmune chickens. The minimum HI antibody inducing dose of V4 vaccine, when measured 3 weeks after vaccination of 6-weeks-old chickens, was 10^5.6 50% egg infectious doses.     

A field trial to assess the effect of vaccination against feline herpesvirus, feline calicivirus and feline panleucopenia virus in 6-week-old kittens.

A trivalent (feline panleucopenia, feline herpesvirus, feline calicivirus), modified live, commercially available cat vaccine was used at either 6, 9 and 12 weeks of age (early schedule) or 9 and 12 weeks of age (conventional schedule), and the serological response to vaccination was assessed. The level of maternally derived antibody present at 6 weeks of age was also established. The use of early vaccination at 6 weeks of age induced an antibody response to each virus by 9 weeks of age in a significant proportion of kittens compared with unvaccinated littermates. There was no difference between the conventionally and early-vaccinated groups in terms of antibody response to any antigen by 12 and 15 weeks of age.     

Use of inactivated oil emulsion infectious bursal disease vaccines in breeder chickens to prevent immunosuppression in progeny chicks

Two chicken flocks, vaccinated with different inactivated infectious bursal disease vaccines, and one unvaccinated flock provided chicks with high and low levels of and no maternally derived immunity. Following challenge at three ages with a subclinical strain of infectious bursal disease virus the chicks were assessed for bursal damage and suppression of the immune response to Newcastle disease virus. Both high and low levels of maternally derived antibody prevented immunosuppression but the lower level provided only partial protection against bursal damage.     

Antibody to alcelaphine herpesvirus-1 (AHV-1) in hamsters experimentally infected with AHV-1 and the 'sheep-associated' agent of malignant catarrhal fever

Malignant catarrhal fever was induced in four groups of hamsters by the inoculation of cells infected with either the C/500 isolate of alcelaphine herpes-virus-1 (AHV-1) or the sheep-associated agent derived from cattle, red deer or Père David's deer. Using an indirect immunofluorescence assay, antibody to AHV-1 was detected in sera of clinically affected animals of all four groups. The reaction of sera from hamsters affected with malignant catarrhal fever induced by AHV-1 caused diffuse cytoplasmic staining while that from sera of hamsters with the sheep-associated form of the disease stained particulate nuclear antigens. Tests employing three other bovid herpesviruses were negative and no reaction was found with sera from normal hamsters. These studies provide convincing evidence that a virus antigenically related to AHV-1 is the cause of sheep-associated malignant catarrhal fever and that the same virus probably causes this form of the disease in both cattle and deer.     

Pathophysiology of the periparturient egg rise in sheep: a possible role for IgA.

The relationship between anti-parasite IgA antibody levels in plasma and the periparturient egg rise in sheep was investigated. Ostertagia circumcincta larvae (5000 third stage larvae three times weekly) were administered to three groups of seven adult immune ewes from 12 weeks before until three weeks after lambing (group 1) or from six (group 2) or 14 (group 3) weeks before until three weeks before lambing. Seven additional ewes were not challenged (group 4 controls). Ewes in groups 1, 2 and 4 received anthelmintics 14 weeks before lambing. Challenge of the pregnant ewes with O circumcincta larvae resulted in substantial increases in faecal egg counts only during the periparturient period regardless of the larval dosing regimen. Furthermore, the periparturient rise in faecal egg counts was closely associated with a significant increase in anti-parasite IgA antibody levels in plasma. This rise in IgA antibody levels occurred at a time when IgA is transported from the gut to milk during early lactation. It is postulated that this may lead to a temporary reduction in abomasal antibody levels of ewes and hence permit the establishment of larvae and, or, the emergence and development of inhibited larvae and thereby lead to the periparturient rise in faecal egg count.     

Border disease: virus persistence, antibody response and transmission studies

Three groups of five and one group of four oestrus-synchronised sheep were inoculated with Border disease (BD) virus at 52 +/- 2 days after their first service. Transmission of virus to offspring as demonstrated by virus isolation, detection of viral antigen and, or antibody response occurred in 12 of 19 sheep and probably in four others which aborted or produced stillborn lambs. Both apparently normal and clinically affected animals excreted virus in saliva, urine and faeces, and excretion and contact transmission to sheep and pigs persisted for up to two and a half years. Most of the tissues of infected sheep contained virus titres between 10(3.5) and 10(5.5) TCID50 per g. The immune response in the lambs varied, in some it began before birth, in others a transient or low level response was observed in the first or second year, while others remained serologically negative for two and a half years.     

Efficacy of an intranasal immunization with gEgC and gEgI double-deletion mutants of Aujeszky's disease virus in maternally immune pigs and the effects of a successive intramuscular booster with commercial vaccines

In this study, an intranasal immunization strategy was set up in maternally immune pigs in order to protect them not only clinically but also virologically. Two genetically engineered Aujeszky's disease virus (ADV) strains, Kaplan gE-gI- and Kaplan gE-gC-, were used for intranasal immunization. Both strains were safe for 4-week-old pigs. A single intranasal inoculation of 10(6.0) TCID50 of Kaplan gE-gI- and Kaplan gE-gC- at 4 weeks of age in the presence of moderate titres of maternally derived antibodies (SN titres: 12-16) reduced the amount of weight loss, fever and virus excretion upon challenge 6 weeks later. In a second experiment, the effect of an additional intramuscular booster with three different commercial vaccines (containing attenuated Bartha or NIA3-783 or inactivated Phylaxia; all suspended in an oil-in-water emulsion) at 10 weeks of age was evaluated. One month after the last intramuscular booster, between five and seven pigs from each group were selected for challenge. All intranasally/intramuscularly immunized pigs showed a significantly better clinical and virological protection after challenge than the single intranasally immunized pigs. In the double immunized group, the protection was better when Kaplan gE-gC- was used for the intranasal priming (only two of 14 pigs excreted virus with a duration of 4 days) than when Kaplan gE-gI- was used (13 of 18 pigs excreted virus with a duration ranging from 1 to 4 days). The virological protection was not influenced by the type of vaccine used for booster vaccination. Because the intranasal/intramuscular immunization approach is very compatible with current pig movements on farms and pigs with moderate levels of maternally derived antibodies can effectively be immunized, it can be considered as a good alternative to intramuscular/intramuscular vaccinations especially in regions with a high ADV prevalence.     

ADMINISTRATION OF A VACCINE PREPARED FROM THE AUSTRALIAN V4 STRAIN OF NEWCASTLE DISEASE VIRUS BY AEROSOL AND DRINKING WATER

SUMMARY An experimental vaccine containing the avirulent Australian V4 strain of Newcastle disease virus was used to vaccinate 3- or 6-week-old chickens by aerosol and drinking water application. The chickens lacked maternally derived antibody to Newcastle disease virus. When the vaccine virus was diluted in tap water more than 90% of the infectivity was destroyed immediately. The addition of 0.25% skim milk prevented this loss and there was no loss in distilled water. Rates of inactivation at 37°C were similar in tap water and distilled water and were unaffected by the addition of skim milk. Both methods of vaccination resulted in the production of haemagglutination-inhibition antibodies which persisted for at least 8 to 12 weeks. The antibody response to aerosol vaccination was significantly better than that following drinking water vaccination. No clinical disease was induced by exposure to vaccine virus. Serum neutralisation antibodies paralleled those detected by haemagglutination-inhibition in chicks vaccinated once by drinking water. After revaccination through the drinking water, haemagglutination-inhibition antibodies were boosted temporarily while neutralising antibodies were maintained at an enhanced level. From chickens vaccinated by aerosol, Newcastle disease virus was recovered for 10 days from lungs and for 7 days from tracheas and caecal tonsils. Peak viraemia was detected 2 and 3 days after vaccination while both neutralising and haemagglutination-inhibition antibodies became detectable 5 days after vaccination.     

Immunization of day-old chicks having maternally derived antibodies against infectious bronchitis: degree of protection as monitored by ciliary activity after intratracheal challenge.

One-day-old chicks with maternally derived antibodies were vaccinated against infectious bronchitis (IB) with 3000 EID50 of the IB vaccine virus designated H120. The degree of protection induced by intranasal-eye drop (IE) vaccination was compared to that achieved by spray (S) vaccination. The protection afforded by vaccination was monitored by intratracheal challenge with IBV strain M-41 (clinical signs, ciliary activity in tracheal explants, virus isolation) and by serological tests (ovoneutralization, microneutralization in cell culture, haemagglutination inhibition (HI) test, ELISA). Intranasal-eye drop vaccination provided protection against intratracheal challenge. Immunity developed around 31 days of age. Spray vaccination failed to give protection against challenge by the same route. No difference was demonstrable in effectiveness between the two routes of vaccination by serological tests. No elevation of the antibody level occurred in either group. The level of maternally derived antibodies declined with age.     

The effect of colostrum-derived antibody on neo-natal transmission of caprine arthritis-encephalitis virus infection

Two groups of 6 newborn goat kids were artificially fed colostrum containing antibody to caprine arthritis-encephalitis (CAE) virus, obtained from clinically affected does. Kids in group A were fed the colostrum from birth until 7 days of age, while kids in group B were fed colostrum from 1 to 3 days after birth for 7 days. Kids were fed cow's milk at all other times. Serum antibody resulting from the consumption of colostrum, detected by agar gel immunodiffusion (AGID) tests, lasted for up to 8 weeks in group A, but none was detected in group B. Four kids from each group became infected with CAE virus as demonstrated by the emergence of active immunity and by virus isolation procedures. It appeared that uptake of colostral antibody by group A did not prevent viral transmission, interfere with development of active immunity, or modify the outcome of the CAE virus infection.     

Intranasal vaccination of pigs against Aujeszky's disease: comparison with one or two doses of attenuated vaccines in pigs with high maternal antibody titres

Ten-week-old pigs with high levels of maternally derived antibody (MDA) against Aujeszky's disease virus (ADV) were given either a single intranasal vaccination or one or two doses (with an interval of three weeks) of commercially available attenuated ADV vaccines intramuscularly. The pigs did not produce a clear neutralising antibody response to ADV. However, pigs vaccinated intranasally and pigs given two doses of attenuated ADV vaccines were protected against intranasal challenge with virulent ADV two months after the first vaccination. Pigs given one parenteral dose of attenuated ADV vaccine were insufficiently protected. Protection was shown by shorter periods of growth arrest and fever and a greater reduction of virulent virus shedding after challenge in vaccinated pigs than in unvaccinated control pigs. Although intranasal vaccination conferred protection comparable to two parenteral doses of attenuated vaccines, it reduced shedding of virulent virus much more effectively. These results, together with those of other studies, show that intranasal vaccination confers better protection against Aujeszky's disease in pigs with MDA than parenteral vaccination. However, the efficacy of intranasal vaccination also decreases with increasing levels of MDA at the time of vaccination.     

A comparison of serum neutralisation, immunofluorescence and immunoperoxidase tests for the detection of antibodies to chicken anaemia agent

A comparison was made of the serum neutralisation, immunofluorescent antibody and immunoperoxidase tests for the detection of antibodies to chicken anaemia agent. Serum samples from groups of chicks with and without maternally derived antibody to the agent were tested and the response of chicks after inoculation with the agent was also measured. The serum neutralisation test was reliable and sensitive, but expensive and could take up to three weeks to obtain a result. The immunofluorescent antibody test was cheaper and required only one day to obtain a result, but it was not as sensitive in detecting low levels of antibody to the chicken anaemia agent. The immunoperoxidase test was also cheaper but took two days to obtain a result and required one more manipulation than the immunofluorescence test. It was comparable to the serum neutralisation test in its ability to detect low levels of antibody.     

Pseudorabies virus is transmitted among vaccinated conventional pigs, but not among vaccinated SPF pigs

Whereas the reproduction ratio (R) of pseudorabies virus (PRV) in vaccinated specific pathogen free (SPF) pigs without maternally derived antibodies under experimental conditions has repeatedly been shown to be significantly below 1, R in vaccinated conventional pigs in the field with maternally derived antibodies was significantly above 1. To exclude the difference in husbandry conditions as a cause for this discrepancy, we quantified and compared the transmission of PRV in both groups under identical experimental conditions. Whereas none of the SPF sentinel pigs became infected (R=0, significantly<1), all conventional sentinel pigs did become infected (R=2.5, significantly>1). Moreover, only one SPF pigs shed virus in saliva, the mean cumulative titre being almost a 100-fold less than in conventional pigs (17 pigs, P=0.003). In addition, the mean proliferation of peripheral blood lymphocytes in response to PRV antigens was significantly higher in SPF pigs than in conventional pigs at all points studied (P<0.0001). Moreover, the virus-neutralising antibody titre after vaccination was significantly higher in SPF pigs than in conventional pigs. We conclude that the discrepancy in transmission between vaccinated SPF pigs and vaccinated conventional pigs cannot be attributed to the experimental conditions.     

Intranasal vaccination of pigs against Aujeszky's disease: protective immunity at 2 weeks, 2 months and 4 months after vaccination in pigs with maternal antibodies.

The purpose of the study was to evaluate the short- and long-term immunity after intranasal vaccination in pigs with maternally derived antibodies (MDA). In two experiments, 10-week-old pigs with moderate MDA titres against Aujeszky's disease virus (ADV) were vaccinated intranasally with the Bartha strain of ADV to evaluate the protective immunity conferred at 2 weeks, 2 months and 4 months after vaccination. Protection was evaluated on the basis of severity of clinical signs, periods of fever and growth arrest, and duration and amount of virus excreted after challenge with a virulent ADV. During the first 2-3 weeks after vaccination, antibodies to ADV continued to decline as in unvaccinated control pigs. After that, antibody titres stabilized or gradually increased. At 2 weeks, 2 months and 4 months after vaccination, vaccinated pigs were significantly better protected than unvaccinated controls. The vaccinated pigs challenged 2 weeks after vaccination hardly developed any sign of disease. Mild signs of Aujeszky's disease and a growth arrest period of 5 days were observed in vaccinated pigs challenged 2 months after vaccination, whereas vaccinated pigs challenged 4 months after vaccination developed severe signs of disease and a growth arrest period of 13 days. Vaccinated pigs challenged 2 weeks after vaccination did not excrete challenge virus, and pigs challenged 2 or 4 months after vaccination excreted far less virus than unvaccinated controls. The results demonstrate that intranasal ADV vaccination of pigs with moderate MDA titres protected them from 2 weeks to at least 4 months after vaccination. Immunity steadily declined, however, after vaccination.     

Subclinical infectious bursal disease in commercial broiler flocks in Saskatchewan.

Five commercial broiler flocks, not vaccinated for infectious bursal disease virus, derived from infectious bursal disease virus-vaccinated breeder flocks were surveyed for evidence of bursal damage and infectious bursal disease virus infection. They were compared with two groups of birds raised in isolation. Serum samples from one day old chicks contained maternal anti-infectious bursal disease virus antibodies which declined to undetectable levels by four weeks of age. Serum antibody levels remained undetectable in both control groups and one commercial flock, whereas four of the five commercial flocks had actively produced anti-infectious bursal disease virus antibodies by slaughter age. The weight of bursae from infectious bursal disease virus-positive flocks declined as compared to controls after four weeks of age. The decline in weight correlated with the appearance of histopathological lesions. Infectious bursal disease virus antigen was demonstrated in selected infected bursae and infectious bursal disease bursae and infectious bursal disease virus was isolated from some of these damaged bursae. Clinical infectious bursal disease was not observed in any of the commercial flocks. The importance of subclinical bursal damage and immunosuppression is discussed.