REPLICATION OF INFECTIOUS LARYNGOTRACHEITIS VIRUS IN CHICKENS FOLLOWING VACCINATION

SUMMARY The site of replication of infectious laryngotracheitis vaccine virus (ILTV) was studied in chickens vaccinated by drinking water (DW), intraconjunctival (IC) and cloacal (CL) routes. The anatomical sites exposed to vaccine were determined by simulating vaccination with rhodamine red dye. Virus replication was determined by recovering virus from various organs at necropsy.
The dye simulation studies clearly demonstrated that DW vaccination did not usually expose susceptible target organs to virus while the CL and IC routes flooded susceptible organs with vaccine.
Virus replication was confined to the cloaca in CL vaccinated birds while in IC and DW vaccinated birds most replication took place in the nasal cavity. Vaccine virus did not always become established in DW vaccinated birds and its establishment did not appear to be related to the amount of vaccine these birds were exposed.
It was concluded that DW vaccination depends for its success upon the accidental contamination of the nasal cavity with vaccine virus during the act of drinking.     

VACCINATION AGAINST EXPERIMENTAL STAPHYLOCOCCOSIS IN SHEEP - OBSERVATIONS ON BACTERIOLOGY AND PATHOLOGY FOLLOWING CHALLENGE

Sheep were vaccinated with a killed Staphylococcus aureus vaccine (2 doses) which had been cultured in vitro (Group 1), a killed S. aureus vaccine (2 doses) cultured in vivo (Group 2) or a single dose of a live vaccine (Group 3). Other sheep were used as non-vaccinated controls. All sheep were challenged by intravenous injection of 2.6 x 10(11) washed, viable S. aureus organisms, the vaccinated animals being given the challenge inoculum at various intervals after vaccination. The control sheep survived for 29h (mean) after challenge. Animals given killed vaccines survived longer, (particularly Group 2) if challenged less than 40 days post-vaccination, compared with those challenged more than 40 days post-vaccination. Animals in Group 3 survived longer if challenged after 40 days post-vaccination than those in Groups 1 or 2. There were no significant differences between the treatment groups for numbers of S. aureus recovered from blood in the 3h period following challenge. Histological and bacteriological evidence showed that the kidneys were more severely affected by the challenge inoculum than heart, spleen, liver or lungs. The kidneys showed both toxigenic and lymphoreticular reactions and large numbers of staphylococci were recovered more reliably from kidneys than other organs.     

WHITE LIVER DISEASE IN LAMBS

An outbreak of white liver disease in lambs in Western Australia is described. The disease affected 2- to 3-month-old lambs and was characterised by liver damage, severe ill-thrift, depression, serous ocular discharge, photosensitisation, and a high mortality rate. Transient central nervous system signs occurred. A positive response to vitamin B₁₂ therapy was demonstrated.