This short communication reports on the isolation of QX-like infectious bronchitis virus (IBV) from the proventriculus of broiler chicken in England, and its pathogenesis in specific-pathogen-free (SPF) chicks. This appears to be the first report of the isolation of this virus from the proventriculus of affected chicks in the UK. The virus was first recovered from this tissue in chickens in China in 1996 (YuDong and others 1998), and later, more cases were reported, including in flocks vaccinated against IBV (Yu and others 2001). We received samples of kidney and proventriculus from a flock of 56-days-old commercial broiler chickens, where the submitting field veterinarian reported respiratory signs, increased levels of mortality, a poor feed conversion ratio and suboptimal live body weight gain. At necropsy, proventriculitis and swollen kidneys were reported. Similar tissues were pooled and processed for IBV detection by reverse-transcriptase PCRs (RT-PCR), as previously described (Worthington and others 2008), and virus isolation (VI) were attempted. RT-PCR tests on the supernatant of the pooled tissues of kidneys were negative for IBV, while the proventriculus samples were positive. The proventriculus was negative for avian metapneumovirus (aMPV), Newcastle disease virus (NDV) and infectious bursal disease virus (IBDV), but positive for fowl adenovirus by PCR tests. Subsequent sequencing of the IBV showed that it closely resembled a vaccinal strain belonging to IBV 793B. Since the flock had been vaccinated with a 793B-type vaccine two weeks prior to the sampling, it was likely that residual genome of the vaccine was detected. The tissue supernatant was subjected to VI, both in tracheal organ cultures (TOC) and embryonated chicken eggs (ECE).

The aim of this study was to compare the ability of a live incomplete strain (Strain 48) and a live complete strain (Strain 89) of Toxoplasma gondii to protect against abortion and congenital infection following an oral challenge of T. gondii oocysts. Sixty-nine two-tooth ewes were immunised pre-tupping with live Strain 48 of T. gondii tachyzoites and seventy ewes were immunised with Strain 89. Eighty-two serologically negative ewes served as controls. At mid-pregnancy half of the ewes were challenged orally with T. gondii oocysts (2x10(5)/ewe). The ewes vaccinated with Strain 48 were significantly (p<0.05) protected against the effects of experimental challenge and the rate of congenital infection was also significantly (p<0.15) reduced. The ewes vaccinated with Strain 89 were also significantly (p<0.05) protected. The serological response to challenge as measured by both the Dye test and the Indirect Haemagglutination test varied considerably between the two vaccinated groups.

Two-tooth ewes (n=48) were immunized pre-tupping with a live Toxoplasma gondii vaccine. At midpregnancy these ewes were challenged intravenously with 1 x 105 live T. gondii tachyzoites. The strain of T. gondii used for vaccination was an incomplete strain that did not produce oocysts. It was derived by continuous twice weekly passage in mice. The lambing percentage for ewes immunized with the live vaccine was significantly higher (P<0.001 normal score) than non-vaccinated control ewes. However, vaccination did not prevent foetal or placental infection. The serological response to vaccination and challenge was measured by both the Dye test and the Indirect Haemagglutination test. No significant relationship between titre of antibody and protection in the vaccinated ewes was observed.

Further studies are required to confirm the clinical significance of flock-based antibody responses, and to validate their use in identifying recently aborted ewes, especially where there are no aborted fetuses for examination.

No abstract