Variable effect of vaccination against highly pathogenic avian influenza (H7N7) virus on disease and transmission in pheasants and teals.

Highly pathogenic avian influenza viruses can affect many bird species, with disease symptoms ranging from severe morbidity and high mortality to mild transient illness. Much is known about infections in chickens, but for other captive birds the relations between disease symptoms, excretion patterns, and transmission, as well as the effect of vaccination on these relations are not clear. We report results from experimental transmission studies with a highly pathogenic H7N7 virus and two commonly kept bird species (ringed teals and golden pheasants).

Effect of vaccination on transmission of HPAI H5N1: the effect of a single vaccination dose on transmission of highly pathogenic avian influenza H5N1 in Peking ducks.

The highly pathogenic H5N1 avian influenza virus is widespread among domestic ducks throughout Southeast Asia. Many aspects of the poultry industry and social habits hinder the containment and eradication of AI. Vaccination is often put forward as a tool for the control of AI.

Occurrence and characteristics of class 1, 2 and 3 integrons in Escherichia coli, Salmonella and Campylobacter spp. in the Netherlands.

Objectives: To determine the occurrence and transmission of class 1, 2 and 3 integrons in multidrug-resistant or sulfamethoxazole-resistant Salmonella from human and animal sources and in Campylobacter spp. and Escherichia coli from broilers isolated in the Netherlands in 2004.

Methods: PCR, restriction fragment length polymorphism (RFLP) and DNA sequencing were used to detect integrase genes and gene cassettes within 234 E.

Limited BVDV transmission and full protection against CSFV transmission in pigs experimentally infected with BVDV type 1b.

Bovine viral diarrhea virus (BVDV) in pigs may interfere with the detection and epidemiology of classical swine fever virus (CSFV). To investigate the importance of BVDV infections in pigs, first we studied the transmission dynamics of a recent BVDV field isolate. Subsequently, the protection of BVD antibodies against transmission and clinical disease of CSF virus was studied.

Rapid and discriminatory diagnosis of scrapie and BSE in retro-pharyngeal lymph nodes of sheep.

Background: Diagnosis based on prion detection in lymph nodes of sheep and goats can improve active surveillance for scrapie and, if it were circulating, for bovine spongiform encephalopathy (BSE). With sizes that allow repetitive testing and a location that is easily accessible at slaughter, retropharyngeal lymph nodes (RLN) are considered suitable organs for testing. Western blotting (WB) of brain homogenates is, in principle, a technique well suited to both detect and discriminate between scrapie and BSE.

Quantification of the effect of vaccination on transmission of avian influenza (H7N7) in chickens.

Recent outbreaks of highly pathogenic avian influenza (HPAI) viruses in poultry and their threatening zoonotic consequences emphasize the need for effective control measures. Although vaccination of poultry against avian influenza provides a potentially attractive control measure, little is known about the effect of vaccination on epidemiologically relevant parameters, such as transmissibility and the infectious period. We used transmission experiments to study the effect of vaccination on the transmission characteristics of HPAI A/Chicken/Netherlands/03 H7N7 in chickens.

Performance of clinical signs in poultry for the detection of outbreaks during the avian influenza A (H7N7) epidemic in The Netherlands in 2003.

The aim of this study was to make an inventory of the clinical signs of high-pathogenicity avian influenza (HPAI), to facilitate the development of an operational syndrome-reporting system (SRS) in The Netherlands as an early warning system for HPAI outbreaks. A total of 537 poultry flocks (240 infected and 297 non-infected) with a clinical suspicion of an infection with HPAI virus were investigated with respect to the clinical signs observed. Standardized reports were analysed with respect to observed clinical signs in the flocks.

Ability of veterinary pathologists to diagnose classical swine fever from clinical signs and gross pathological findings.

Clinical signs recorded in a classical swine fever (CSF)-suspect situation and the results of the subsequent post-mortem examination (PME) from swine submitted to post-mortem during the 1997-1998 CSF epidemic in the Netherlands, were presented in an experiment as anonymous cases (without knowledge of the actual infection status of the submission) to five veterinary pathologists for their judgment: CSF-suspect or non-suspect. It was presented to them in two hypothetical situations: country was free of CSF for 5 years and CSF was detected in the country 2 weeks ago. Subsequently, their judgment was compared to the gold standard (infection status of the submission on the basis of an immunofluoresence assay on tissue samples) and the sensitivity (Se) and specificity (Sp) of clinical diagnosis was estimated.

The highly pathogenic avian influenza A (H7N7) virus epidemic in The Netherlands in 2003--lessons learned from the first five outbreaks.

Clinical signs and gross lesions observed in poultry submitted for postmortem examination (PME) from the first five infected poultry flocks preceding the detection of the primary outbreak of highly pathogenic avian influenza (HPAI) of subtype H7N7 during the 2003 epidemic in the Netherlands are described. The absence of HPAI from the Netherlands for more than 75 yr created a situation in which poultry farmers and veterinary practitioners did not think of AI in the differential diagnosis as a possible cause of the clinical problems seen. Increased and progressive mortality was not reported to the governmental authorities by farmers or veterinary practitioners.

Performance of gross lesions at postmortem for the detection of outbreaks during the avian influenza A virus (H7N7) epidemic in The Netherlands in 2003.

A total of 123 submissions (on average, five birds per submission) from poultry flocks with a suspicion of an infection with highly pathogenic avian influenza virus were investigated at postmortem during the 2003 epidemic in The Netherlands. A total of 86 of these submissions were from infected flocks (positive submissions), and 37 submissions were from non-infected flocks (negative submissions). Peritonitis was the most frequently (62%) recorded pathological finding in positive submissions, followed by tracheitis (43%), oedema of the neck and/or wattles (12%) and (petechial) haemorrhages in the proventriculus (4%).

Classification of Dutch and German avian reoviruses by sequencing the sigma C protein.

We have amplified, cloned and sequenced (part of) the open reading frame of the S1 segment encoding the sigma C protein of avian reoviruses isolated from chickens with different disease conditions in Germany and The Netherlands during 1980 up to 2000. These avian reoviruses were analysed phylogenetically and compared with sequences of avian reoviruses in the Genbank database. The avian reoviruses could be grouped in 5 different genotyping clusters and this classification was identical when the sequences were compared of the 5' end, the 3' end or the whole open reading frame of the sigma C protein.