Monoclonal antibodies (mAbs) were prepared against one UK isolate of turkey rhinotracheitis virus (TRTV). Those which were virus-neutralizing were selected and used, together with polyclonal antisera raised to each isolate in turkeys, in cross-neutralization tests against TRTV strains isolated in the UK and elsewhere. Whilst the polyclonal antisera showed that there was some diversity between them, all strains examined belonged to one serotype. The TRTV strains isolated in the UK could clearly be differentiated from those isolated elsewhere by some of the mAbs. Isolates of TRTV made in South Africa in 1978 and UK in 1985 were more closely related than were isolates made in UK and France within a few months. TRTV strains isolated from turkeys and chickens could not be differentiated. Some mAbs were found to be group-specific in that they neutralized all TRTV strains examined. All mAbs were of either the IgGl or IgG2a isotype and recognized the surface G glycoprotein.

Turkey rhinotracheitis virus (TRTV) was recovered in large amounts from the upper respiratory tract of young turkey poults for about 5 days after experimental eyedrop inoculation with either a virulent or an attenuated strain. Thereafter, small amounts of virus were isolated, but only for up to 14 days after inoculation. Virulent TRTV could be recovered infrequently from the internal organs or the intestinal tract but only if bacteria (Bordetella avium and a Pasteurella-like organism) were administered contemporaneously. The results of transmission studies were in agreement with the virus isolation results since they showed that virus could be transmitted from inoculated poults to TRTV-free poults placed in direct contact with them only during the first 9 days after inoculation. Whether inoculated alone or together with TRTV, B. avium colonised the upper respiratory tract to the same degree but apparently did not invade. In contrast, the Pasteurella-like organism did not colonise when inoculated alone but could be recovered from the respiratory tract when administered simultaneously with either a virulent or an attenuated strain of TRTV.

Four apparently serologically closely related isolates of infectious bronchitis virus were obtained from two flocks of vaccinated broiler breeders, one mile apart, which were experiencing increased mortality and decreases in egg production. The isolates were serologically distinct from isolates previously described and capable of causing characteristic infectious bronchitis-like respiratory infection in young chicks. In one experiment, the H120 vaccine strain of the virus did not protect the trachea against challenge with the new isolates 21 days later.

No abstract

Compared with the severe clinical disease caused by two virulent strains of turkey rhinotracheitis virus (TRTV), an attenuated strain has been shown to cause only slight respiratory infection in 7-day-old TRT-free turkey poults, yet still to be capable of stimulating TRT antibodies and of protecting the poults against challenge with virulent TRTV 21 days later. The stability of the attenuation during 12 turkey-turkey passages of the strain has been demonstrated; the poult passaged and prepassaged strains causing only mild respiratory signs even when bacteria, known to be associated with severe outbreaks of TRT in the field, were included in the inoculum.