tetano
Editor, Senior Moderator
Vet Microbiol. 2011 Sep 17. [Epub ahead of print]
Transmission characteristics of low pathogenic avian influenza virus of H7N7 and H5N7 subtypes in layer chickens.
Gonzales JL, Elbers AR, Bouma A, Koch G, de Wit JJ, Stegeman JA.
Source
Department of Epidemiology, Crisis organization and Diagnostics, Central Veterinary Institute (CVI), Part of Wageningen UR, P.O. Box 65, 8200 AB Lelystad, The Netherlands; Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University P.O. Box 80, 151, 3508 TD Utrecht, The Netherlands.
Abstract
Low pathogenic avian influenza virus (LPAIv) infections of H5 and H7 subtypes in poultry are notifiable to the OIE, hence surveillance programmes are implemented. The rate at which LPAIv strains spread within a flock determines the prevalence of infected birds and the time it takes to reach that prevalence and, consequently, optimal sample size and sampling frequency. The aim of this study was to investigate the transmission characteristics of an H7N7 and an H5N7 LPAIv in layer chickens. Two transmission experiments were performed, which consisted of 30 (first experiment) and 20 (second experiment) pairs of conventional layers, respectively. At the start of the experiments, one chicken per pair was inoculated with LPAIv and the other chicken was contact-exposed. Occurrence of infection was monitored by regularly collecting tracheal and cloacal swab samples, which were examined for the presence of virus RNA by RT-PCR. The results of the test were used to estimate the transmission rate parameter (β), the infectious period (T) and the basic reproduction ratio (R(0)). In addition, egg production and virus shedding patterns were quantified. For the H7N7 virus, the β, T and R(0) estimates were 0.10 (95% confidence interval (CI): 0.04-0.18) day(-1), 7.1 (95% CI: 6.5-7.8) days and 0.7 (95% CI: 0.0-1.7), respectively. With the H5N7 virus, only a few inoculated chickens (5 out of 20) became infected and no transmission was observed. This study shows that transmission characteristics of LPAIv strains may vary considerably, which has to be taken into account when designing surveillance programmes.
Copyright ? 2011 Elsevier B.V. All rights reserved.
PMID:
21982127
[PubMed - as supplied by publisher]
http://www.ncbi.nlm.nih.gov/pubmed/21982127
Transmission characteristics of low pathogenic avian influenza virus of H7N7 and H5N7 subtypes in layer chickens.
Gonzales JL, Elbers AR, Bouma A, Koch G, de Wit JJ, Stegeman JA.
Source
Department of Epidemiology, Crisis organization and Diagnostics, Central Veterinary Institute (CVI), Part of Wageningen UR, P.O. Box 65, 8200 AB Lelystad, The Netherlands; Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University P.O. Box 80, 151, 3508 TD Utrecht, The Netherlands.
Abstract
Low pathogenic avian influenza virus (LPAIv) infections of H5 and H7 subtypes in poultry are notifiable to the OIE, hence surveillance programmes are implemented. The rate at which LPAIv strains spread within a flock determines the prevalence of infected birds and the time it takes to reach that prevalence and, consequently, optimal sample size and sampling frequency. The aim of this study was to investigate the transmission characteristics of an H7N7 and an H5N7 LPAIv in layer chickens. Two transmission experiments were performed, which consisted of 30 (first experiment) and 20 (second experiment) pairs of conventional layers, respectively. At the start of the experiments, one chicken per pair was inoculated with LPAIv and the other chicken was contact-exposed. Occurrence of infection was monitored by regularly collecting tracheal and cloacal swab samples, which were examined for the presence of virus RNA by RT-PCR. The results of the test were used to estimate the transmission rate parameter (β), the infectious period (T) and the basic reproduction ratio (R(0)). In addition, egg production and virus shedding patterns were quantified. For the H7N7 virus, the β, T and R(0) estimates were 0.10 (95% confidence interval (CI): 0.04-0.18) day(-1), 7.1 (95% CI: 6.5-7.8) days and 0.7 (95% CI: 0.0-1.7), respectively. With the H5N7 virus, only a few inoculated chickens (5 out of 20) became infected and no transmission was observed. This study shows that transmission characteristics of LPAIv strains may vary considerably, which has to be taken into account when designing surveillance programmes.
Copyright ? 2011 Elsevier B.V. All rights reserved.
PMID:
21982127
[PubMed - as supplied by publisher]
http://www.ncbi.nlm.nih.gov/pubmed/21982127