Infectious stunting syndrome of chickens in Great Britain: Intestinal ultrastructural pathology

Arrest of Cell Cycle by Avian Reovirus p17 through Its Interaction with Bub3

Avian reoviruses (ARV) are a group of poultry pathogens that cause runting and stunting syndrome (RSS), a condition otherwise known as "frozen chicken", which are characterized by dramatically delayed growth in broilers. It has been known that p17, a nonstructural protein encoded by ARV, prohibits cellular proliferation by halting the cell cycle at the G2/M phase, the result of which is directly associated with the typical clinical sign of RSS. Nevertheless, the mechanism by which p17 modulates cell-cycle progression remains largely unknown. Here, we screened the interactome of ectopically expressed p17 through a yeast two-hybrid assay and identified Bub3, a cellular mitotic checkpoint protein, as a binding partner of p17. The infection of the Vero cells by ARV downregulated the Bub3 expression, while the knockdown of Bub3 alleviated the p17-modulated cell-cycle arrest during ARV infection. Remarkably, the suppression of Bub3 by RNAi in the Vero cells significantly reduced the viral mRNA and protein abundance, which eventually led to diminished virus replication. Altogether, our findings reveal that ARV p17 impedes host cell proliferation through a Bub3-dependent cell-cycle arrest, which eventually contributes to efficient virus replication. These results also unveil a hitherto unknown therapeutic target for RSS.

Dietary supplementation with anti-IL-10 antibody during a severe Eimeria challenge in broiler chickens

Attenuation of host IL-10 activity during Eimeria infection may elicit a robust Th1 response to eliminate the parasite from the gut epithelium. An experiment was conducted to study the effects of feeding IL-10 neutralizing antibody delivered via a dried egg product (DEP) on growth performance, immune responsivity, and gut health outcomes during a severe challenge with either Eimeria acervulina (study 1) or Eimeria tenella (study 2) following FDA CVM #217 protocol to test anticoccidial products. A total of 720 male Ross 308 chicks were used in each study, with 15 replicate cages of 12 birds and the following 4 treatments: sham-inoculated (uninfected) control diet (UCON), Eimeria-infected control diet (ICON), and Eimeria-infected control diet supplemented with DEP at 2 levels (165 [I-165] or 287 [I-287] U/tonne in study 1 and 143 [I-143] or 287 [I-287] U/tonne in study 2). Individual birds assigned to infected treatment groups received a single oral dose of either 200,000 E. acervulina (study 1) or 80,000 E. tenella (study 2) oocysts at 12 d of age (i.e., d post inoculation [DPI] 0), whereas uninfected birds were sham-inoculated with tap water. A one-way ANOVA was performed on outcomes including growth performance, hematology, serum chemistry profiles, immunophenotyping profiles, and intestinal lesion scores. In both studies, DPI 0 to 7 weight gain, feed intake, and feed conversion ratio were worse (P < 0.05) in all infected groups compared with the UCON group. Compared with ICON, DEP supplementation elicited no differences on overall growth performance. Histopathology and lesion scores revealed severe damage to the gut epithelium owing to the Eimeria challenge, yet DEP supplementation did not improve these outcomes or oocyst shedding, hematological measurements, or serum chemistry. However, DEP supplementation improved (P < 0.05) the percentage of circulating CD3⁺ cells at 6 DPI in study 2. These results indicate that DEP does not appear to elicit a coccidiostatic effect during a severe infection with E. acervulina or E. tenella.

A purified recombinant baculovirus expressed capsid protein of a new astrovirus provides partial protection to runting-stunting syndrome in chickens

A new viral sequence likely belonging to a virus of the family Astroviridae was determined using the gut content of chickens affected with the runting-stunting syndrome (RSS) in chickens. Since the appropriate virus could not be isolated in cell culture the open reading frame of the viral capsid protein was cloned to generate a recombinant baculovirus. The protein was purified and used as an experimental vaccine in broiler breeders to provide maternal derived antibodies for the protection of the offspring. The presence of specific antibodies was monitored by an ELISA. The offspring of vaccinated breeder hens were partially protected in a RSS challenge model.

Concurrent cryptosporidiosis and chicken anaemia virus infection in broiler chickens

Concurrent infection with Cryptosporidium baileyi and chicken anaemia virus (CAV) was observed in a flock of 8000 4-week-old broiler chickens. The birds, showing overt symptoms of stunted growth and 25% mortality from hatching to 4 weeks of age, harboured the protozoan in the epithelial cells of the bursa of Fabricius and the urodeal portion of the cloaca. This is the first report on an outbreak of avian cryptosporidiosis associated with CAV.

Avian influenza A virus induced stunting syndrome-like disease in chicks

Two-day-old specific-pathogen free chicks were inoculated with type A influenza virus (A/whistling swan/Shimane/499/83 (H5N3) through the air sac. Inoculated chicks showed mild to severe diarrhea and lesions of pancreatitis and atrophy of the pancreas, thymus and bursa of Fabricius. One chick died on each of days 4, 6 and 14 postinoculation (PI). Reduced weight gain was conspicuous from day 22 PI. Positive immunoreaction to the virus antigen was detected in the pancreas, kidneys, liver, lungs and air sacs, and cecal lamina propria. Virus recovery persisted longer in the pancreas. Some of these findings conformed to those of stunting syndrome.

Recent advances in avian virology

Selected, recent research on the following avian diseases, and their causative viruses, has been reviewed: chicken anaemia, infectious bursal disease, turkey rhinotracheitis, avian nephritis, fowlpox, influenza, infectious bronchitis and turkey enteritis.