29.05.2015

Source: Egg-Cite

A detailed epidemiologic evaluation on the risk factors for rapid and extensive dissemination of HPAI virus has yet to be released, although there is a growing consensus that many of the outbreaks have resulted from deficiencies in biosecurity. Previously I commented on the need to establish and maintain a hierarchy of biosecurity extending from Conceptual Biosecurity (where complexes are located and their scope and size) through Structural Biosecurity (capital investment in facilities to exclude disease) and then Operational Biosecurity (how facilities are managed to prevent introduction of pathogens). Each component is in turn is dependent on the preceding level involving a sequence of appropriate strategic decisions, adequate investment and direct training and supervision of personnel and movement of flocks and equipment.
The establishment of mega-complexes of up to 5 million hens in close proximity especially in Iowa and other Midwest states represented a deficiency in Conceptual Biosecurity. It is axiomatic that if Conceptual Biosecurity elevates the risk and consequences of introducing an infection, the subsequent barriers represented by Structural Biosecurity must be proportionately intensified. In the case of many units, there are deficiencies with regard to fencing, controlled access, hardened roads, ability to decontaminate personnel and vehicles. These installations were not considered in the design of complexes due to the fact that catastrophic diseases such as END and HPAI have to date been exotic. In the desire to achieve lowest possible capital investment and correspondingly lower production costs, a facility which may have represented an initial investment of $120 million, it was not seen necessary to expend $250,000 for installations to maintain a barrier against introduction of infection.
With deficiencies in both Conceptual and Structural Biosecurity and inherent factors favoring introduction and dissemination of bacterial and viral diseases, Operational Biosecurity has also been neglected. Even in the face of massive mortality, there is evidence that personnel involved in movement of pullets, depletion of hens, beak trimming and vaccination of pullets and other activities were not subject to acceptable personal biosecurity precautions. A press report by journalists based in Chicago confirmed unrestricted access to a large complex currently undergoing depletion as a result of exposure to HPAI.
Invoking aerogenous transmission as a major route of disseminating of HPAI although valid in some cases may become an excuse for “business as usual”. There is circumstantial evidence based on the temporal relationship of diagnoses among farms under common ownership that H5N2 infection may well have been tracked by movement of personnel, equipment or products between complexes in different states.
In one specific case, aerogenous transmission could well be accepted given the proximity of the index farm to the second outbreak about three miles away. The larger farm of two-million hens, confirmed positive by surveillance within the infected zone, approximately one week after the initial case was diagnosed, operated with strict biosecurity with no direct biological connection with the index farm of 200,000 hens confined to houses with aviaries. In this case, aerogenous transmission was a real possibility and is consistent with experience gained in the 1972 outbreak of velogenic viscerotropic Newcastle disease (END) in the UK.
At present the industry, APHIS and state departments of agriculture are overwhelmed with a unprecedented incidence rate. To date, 30 million laying hens and 7 million turkeys have been infected during the past six weeks. It is evident that the industry and the public sector must do everything possible to bring an end to the infection. This will require effective biosecurity at the operational level, rapid depletion and disposal of dead and euthanized hens a