INTERACTION BETWEEN INFECTIOUS BURSAL DISEASE VIRUS AND NEWCASTLE DISEASE VIRUS IN CHICKENS

The Australian strain of infectious bursal disease virus (IBDV), 002/73, affected the response of chickens to Newcastle disease virus (NDV). The titre of serum antibodies to NDV in chickens infected with IBDV was significantly lower than that of birds infected with NDV alone. It also appeared that IBDV affected NDV excretion from chickens as NDV was more frequently isolated from chickens infected with IBDV, IBDV infection did not alter the pathogenicity of NDV in chickens. This Australian strain of IBDV therefore appeared to be immunodepressive in one-day-old chickens.     

CONGENITAL AND DEVELOPMENTAL ANOMALIES OF THE GENITALIA OF SLAUGHTERED BULLS

The genital tracts of 968 slaughtered bulls (46% of which were young post-puberal animals) were examined for defects of a congenital or developmental nature. The overall occurrence of such lesions was 7%. These comprised persistent penile frenulum (0.5%), hypospadias (0.3%), detached urethral process (0.4%), testicular hypoplasia (0.2%), cryptorchidism (0.6%), mesonephric duct abnormalities (1.1%) and bulbourethral cysts, fusion and aplasia (3.6%). Segmental aplasia of the mesonephric duct, not previously recorded in the study area, was found in 4 Shorthorn bulls (0.4%); 2 affected animals were from one herd. In 3 cases of hypospadias (2 from one herd), the urethra communicated with the ventral surface of the penis at the junction of the body and glans through a slit-like orifice. The occurrence of defects observed was generally comparable to that found in bull populations elsewhere but elevated occurrence of several defects in particular herds emphasized the need for further study.     

THE PATHOGENESIS OF INFECTIOUS AVIAN ENCEPHALOMYELITIS

Infectious avian encephalomyelitis virus (IAEV) maternal antibody was detected in the serum of chickens for up to 21 days following hatching. This antibody protected chickens against clinical IAE after intracerebral inoculation with van Roekel strain or oral administration of the NSW-1 strain of IAEV. Maternal antibody to IAEV also protected testosterone bursectomised chickens against the development of clinical disease. IAEV maternal antibody also influeced the pattern of virus excretion in faeces and serological responsiveness. This influence on antibody responses persisted beyond the time that IAEV maternal antibody could be detected. The importance of IAEV maternal antibody on the strategy of vaccination against IAE is discussed.     

Parainfluenza-3 virus exposure of beef heifers prior to natural breeding.

Ninety-six Hereford heifers (approximately 7 months of age) were randomly divided into 2 equal groups and housed 1.6 km apart (with 2 replications in time, 1 year apart). At 15 months of age, 1 group/replicate was inoculated with parainfluenza-3 virus, and the other group was given virus-free spent culture medium. Twenty-four hours later, 2 virgin bulls (2 years old) were placed with each group (24 cows) for natural breeding. Viral inoculation caused a twofold increase in parainfluenza-3 titer and a 0.3 C body temperature increase. There was no effect recognized from the virus on natural breeding efficiency.     

Indirect solid-phase microradioimmunoassay for detection of pseudorabies virus antibody in swine sera.

An indirect solid-phase microradioimmunoassay (IRIA) was developed for detection and quantitation of antibodies to pseudorabies virus (PRV) in swine serum. Qualitative results of the IRIA compared closely with results of the serum neutralization test (NT) and the microimmunodiffusion test (MIDT). The IRIA was more sensitive than the NT for detection of antibodies to PRV in swine serum. The IRIA result is expressed numerically. With the IRIA and NT, antibody to PRV was first detectable in 3 experimentally infected pigs at 9 days after inoculation. With MIDT, antibody was detected in the 3 experimentally infected pigs at 9 days after inoculation. With the MIDT, antibody was detected in the 3 experimentally infected pigs at 7, 8, and 9 days after inoculation. The IRIA results are obtainable within a few hours; the NT and MIDT require 48 hours for completion.     

Isolation of bovine adenovirus type 7 from calves with pneumonia and enteritis.

Bovine adenovirus type 7 was isolated from a 10-month-old calf with fibrinopurulent pneumonia and from 2 newborn calves with pneumoenteritis. The viruses were isolated on calf lung and adrenal gland cell cultures and were identified as serotype 7 by immunoelectron microscopy and serum-neutralization tests.