Pathologic findings of highly pathogenic avian influenza virus A/Duck/Vietnam/12/05 (H5N1) in experimentally infected pekin ducks, based on immunohistochemistry and in situ hybridization.

The ongoing H5N1 Asian epidemic is currently affecting a number of avian species including ducks. These birds are an important part of the poultry industry in the affected countries, and it is likely that they are acting as a reservoir of infection. Ten Pekin ducks were challenged with 100 microl containing 10(7) 50% egg infective dose of the highly pathogenic avian influenza virus (HPAIV) A/Duck/Vietnam/12/05 (H5N1), administered by an intra-nasal and oral route. Clinical symptoms were recorded twice a day up to 14 days postinfection (dpi). Clinical signs were first noted at 2 dpi, with conjunctivitis and slight depression, and progressed over a period of 1-3 days to severe neurologic signs consisting of torticollis, incoordination, tremors, and seizures. Survival times varied from 3 to 7 dpi. On postmortem examination, hemorrhages were observed in the duodenum, ceca, proventriculus, ventriculus, trachea, pancreas, and brain. Histologic lesions, as well as immunohistochemistry positivity, were recorded in the pancreas and brain. In situ hybridization revealed viral antigen associated with acinar pancreatic cells, bronchial epithelial cells, and with cells of the central nervous system as well as neurons of the submucosal plexus of the duodenum. Our experimental findings agree with those previously observed in ducks naturally infected with HPAIV H5N1 viruses, confirming the acquired viral neurotropism and pancreatotropism, as previously noted in other avian species, as well as in humans.

Diagnosis and PrP genotype target of scrapie in clinically healthy sheep of Massese breed in the framework of a scrapie eradication programme.

The application of a selective culling programme in two scrapie affected flocks of Massese breed sheep is described. The genetic susceptibility of this breed and the sensitivity of different diagnostic methods in the pre-clinical diagnosis of scrapie were also investigated. Overall, 2,068 clinically healthy sheep underwent PrP genotyping, providing the basis for selective culling. The prevalence of scrapie infection was investigated in susceptible sheep by two independent diagnostic methods. All the sheep older than 18 months (n = 620) were tested by Prionics Check Western rapid test on the obex, with a prevalence of infection of 3.9%. Furthermore, 385 sheep underwent immunohistochemistry (IHC) on retropharyngeal lymph node (RPLN), with a prevalence of infection of 5.2%. Overall, 32 sheep were diagnosed with pre-clinical scrapie. Of these, 31 were positive by Western blot on the spleen, 29 by IHC on the RPLN and tonsil, 28 by IHC on the obex, 24 by rapid test, and only 18 by IHC on the third eyelid. All the scrapie positive sheep were of the ARQ/ARQ, ARQ/AHQ or ARQ/VRQ genotypes. No significant differences in scrapie prevalence were observed among these genotypes. The estimated risk of the three targeted alleles was also similar, suggesting that in this breed the VRQ allele was not at higher risk for scrapie, compared to the ARQ and AHQ alleles.