TY - CHAP
T1 - Effectiveness of control measures on the transmission of avian influenza (H7N7) between flocks
AU - Stegeman, J.A.
AU - Bouma, A.
AU - Elbers, A.R.W.
AU - van Boven, R.M.
AU - de Jong, M.C.M.
AU - Koch, G.
PY - 2005
Y1 - 2005
N2 - On 28 February 2003 an epidemic of fowl plague started in The Netherlands,
caused by a highly pathogenic avian influenza virus (HPAIV) of type H7N7. The
epidemic started in the `Gelderse Vallei¿, spread to adjacent areas and to the province
of Limburg. During the epidemic, 255 flocks were diagnosed as infected. The
epidemic was combated by stamping out infected flocks and pre-emptive culling of
flocks within a 1-km radius. Moreover, screening and tracing activities were
implemented to enhance the detection of infected flocks. In addition, a transportation
ban was enforced. In a further stage of the epidemic, poultry-free buffer zones were
created, contacts between different parts of the country were reduced by
compartmentalization and large areas were depopulated of all poultry. In all, 1,000
commercial flocks were pre-emptively culled, in addition to over 17,000 flocks of
smallholders.
In this study we quantified the transmission of HPAIV between flocks during
different phases of the epidemic. To stop an epidemic, infected flocks should be
detected and depopulated before they have infected on average more than one other
flock. This average number of secondary infections caused by one infectious flock is
called the reproduction ratio (Rh). Upon the implementation of the control measures in
the Gelderse Vallei, Rh dropped from 5.0 (95% confidence interval (CI): 2.9-8.6) to
0.91 (95%CI: 0.39-2.13). Moreover, in Limburg, Rh dropped from 2.5 to 0.86
(95%CI: 0.28-2.68) after the control measures came into force. Apparently, the
measures significantly reduced the transmission of the virus. However, because the
95% confidence intervals of Rh after the implementation of control measures include
one, it is uncertain whether the implemented measures are really sufficient to
eliminate the virus in an area with a high poultry density. Consequently, additional
control measures should be considered.
Key words: avian influenza; fowl plague; transmission; control measures
AB - On 28 February 2003 an epidemic of fowl plague started in The Netherlands,
caused by a highly pathogenic avian influenza virus (HPAIV) of type H7N7. The
epidemic started in the `Gelderse Vallei¿, spread to adjacent areas and to the province
of Limburg. During the epidemic, 255 flocks were diagnosed as infected. The
epidemic was combated by stamping out infected flocks and pre-emptive culling of
flocks within a 1-km radius. Moreover, screening and tracing activities were
implemented to enhance the detection of infected flocks. In addition, a transportation
ban was enforced. In a further stage of the epidemic, poultry-free buffer zones were
created, contacts between different parts of the country were reduced by
compartmentalization and large areas were depopulated of all poultry. In all, 1,000
commercial flocks were pre-emptively culled, in addition to over 17,000 flocks of
smallholders.
In this study we quantified the transmission of HPAIV between flocks during
different phases of the epidemic. To stop an epidemic, infected flocks should be
detected and depopulated before they have infected on average more than one other
flock. This average number of secondary infections caused by one infectious flock is
called the reproduction ratio (Rh). Upon the implementation of the control measures in
the Gelderse Vallei, Rh dropped from 5.0 (95% confidence interval (CI): 2.9-8.6) to
0.91 (95%CI: 0.39-2.13). Moreover, in Limburg, Rh dropped from 2.5 to 0.86
(95%CI: 0.28-2.68) after the control measures came into force. Apparently, the
measures significantly reduced the transmission of the virus. However, because the
95% confidence intervals of Rh after the implementation of control measures include
one, it is uncertain whether the implemented measures are really sufficient to
eliminate the virus in an area with a high poultry density. Consequently, additional
control measures should be considered.
Key words: avian influenza; fowl plague; transmission; control measures
M3 - Chapter
SN - 9781402034398
T3 - Wageningen UR Frontis series
SP - 57
EP - 63
BT - Avian Influenza: Prevention and Control
A2 - Schrijver, R.
A2 - Koch, G.
ER -