Heat inactivation of serotype 1 infectious bursal disease virus.

Heat inactivation curves for infectious bursal disease virus serotype 1 (IBDV) strain 52/70 in bursal homogenate supernatant were constructed for 70 degrees C, 75 degrees C and 80 degrees C. Biphasic, multiple kinetics curves were produced with an initial rapid drop in infectivity followed by a more gradual decline. In this second phase the approximate times taken to reduce the infectivity by 1 log(10) at each temperature were: 70 degrees C (18.8 min), 75 degrees C (11.4 min) and 80 degrees C (3.0 min), confirming the heat resistance of this virus.

Use of an inactivated infectious bursal disease oil emulsion vaccine in commercial layer chicks.

Commercial layer chicks of different ages were inoculated with either one-fifth, two-fifths or a full dose of an inactivated infectious bursal disease oil emulsion vaccine and then challenged with virulent virus. The partial doses given at seven or 10 days old gave only partial protection. A full dose given at 10, 14 or 28 days old failed to give full protection but a full dose administered at seven days old protected all the chicks after each challenge.

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.

Use of infectious bursal disease vaccines in chicks with maternally derived antibodies.

Day-old chicks with maternally derived infectious bursal disease (IBD) antibodies were inoculated with IBD oil emulsion vaccine. The vaccine protected at least 85 per cent of the chicks when they were challenged at four weeks old with virulent IBD virus and at least 90 per cent of those challenged at seven weeks of age. There was no benefit in using a combination of the oil emulsion vaccine and a live IBD vaccine.

An outbreak of disease due to chicken anaemia agent in broiler chickens in England.

Outbreaks of clinical chicken anaemia in four broiler chicken flocks affected chicks which were all the progeny of the same parent flock. Three of the flocks were reared on farms in the south-east of England and in these flocks clinical disease did not occur in other chicks of the same age. The fourth flock was reared in a positive-pressure isolator and clinical disease appeared at 10 days of age. Chicken anaemia agent was isolated from three of the flocks. The clinical signs, post mortem lesions and histopathological changes were similar to those reported in outbreaks of the disease in other countries. The parent flock seroconverted to chicken anaemia agent, as determined by fluorescent antibody tests, during the course of the outbreaks.

Failure of maternally derived infectious bursal disease antibodies to serotypes 1 and 2 to protect against heterologous virus.

Chicks with maternally derived infectious bursal disease antibodies to either serotype 1 or 2 were challenged at intervals between day-old and 7 weeks of age using the homologous and the heterologous viruses. With both serotypes good protection was demonstrated against the homologous challenge, but not against the heterologous virus.

Infectious stunting syndrome: evidence of vertical transmission.

Day-old broiler chicks were collected while in transit from a hatchery to a farm and reared in isolation. These chicks did not develop clinical signs of infectious stunting syndrome. When they were 14 days old, susceptible day-old chicks were placed in contact with them and these subsequently developed typical signs and lesions of the disease.

Antibody responses and virus reisolation in turkeys experimentally infected with an infectious bursal disease isolate.

Following the infection of turkey poults with a field isolate of infectious bursal disease virus, antibody levels were examined and reisolation of the virus was attempted. After inoculation at 36 days of age, peak titres in both the inoculated and a contact-exposed group were obtained after 13 days. The titres fell slightly during the next week and then remained level until the experiment was terminated at 91 days of age. Virus was reisolated from faeces from day 3 until day 8 after inoculation in the inoculated group and from day 4 until day 9 in the contact-exposed group. In the inoculated group, virus was recovered from the bursae, spleens and intestines on both days 4 and 6 after inoculation, but the thymuses on day 6 only. No clinical signs were observed.

Resistance of chickens to challenge with the virulent Herts 33 strain of Newcastle disease virus induced by prior infection with serologically distinct avian paramyxoviruses.

Results indicate that some degree of protection from challenge by Newcastle disease virus (NDV)/Herts 33 was conferred on chickens by prior infection with PMV/turkey/Wisconsin/68, PMV/turkey/Ontario/6661/68, PMV/Netherlands/449/75 and PMV/parakeet/England/39/78 viruses, all of which are serologically related but distinguishable from NDV. Except for one bird which survived challenge three weeks after infection with Robin/Hiddensee/19/75, no protection was seen in chickens infected with other unrelated avian paramyxoviruses. In contrast to infection with NDV-B1, birds protected by infection with avian paramyxoviruses showed large increases in NDV haemagglutination inhibition (HI) titres after challenge. In these birds considerable increases in the homologous HI titres were also seen after challenge.

Properties of a newly isolated, serologically distinct avian paramyxovirus.

The morphological, bio-physical and growth properties of the isolate duck/Hong Kong/D3/75 (D3/75) were consistent with this virus being a member of the paramyxovirus group. Using haemagglutination inhibition and neuraminidase inhibition tests no serological relationships between D3/75 and other paramyxoviruses could be demonstrated. The structural polypeptides of D3/75 were also typical of paramyxoviruses, consisting of 6--7 polypeptides ranging in molecular weight from 46,000--200,000 under reduced conditions. Two polypeptides were glycosylated.

Relationship of parakeet/Netherlands/449/75 virus to other avian paramyxoviruses.

Serological and physico-chemical properties of parakeet/Netherlands/449/75 (449) virus indicated a close relationship to paramyxovirus/Turkey/Wisconsin/68.