Modelling control of avian influenza in poultry: the link with data

In this paper the authors discuss the use of modelling in the evaluation of strategies designed to control epidemics of highly pathogenic avian influenza (HPAI) in poultry. Referring to a number of published models for HPAI transmission in poultry, the authors describe the different ways that modellers use quantitative information. Quantitative information can be used for model building, parameter estimation, and model validation. The authors emphasise that in the case of HPAI transmission in poultry there are important gaps in our understanding. Due to these gaps the models for the effects of certain control strategies, especially those involving vaccination of poultry, need to be based on provisional assumptions. Hence, it is necessary to validate these models and to do research to improve our understanding of the underlying processes in order to better parameterise the models and better estimate the parameter

Verslag van de workshop "Indirecte transmissie", 25 september 2008

Een samenvatting van 10 presentaties met de bijbehorende discussies: Introduction: indirect transmission; Indirect transmission, implications from a policy point of view; Transmission by air of micro-organisms in poultry: experimental and hatchery studies; Indirect transmission of Campylobacter in broilers; Experimental studies to evaluate the transmission of Classical Swine Fever; Underlying mechanisms of transmission - quantification of CSFV excretion; Experimental quantification of transmission over a distance: an evolutionary point of view; Use of data on contact-structure in InterSpread simulation; Go with the flow: water and foodborne health risks; Avian influenza: survival studie

Between-farm transmission routes of highly transmissible diseases in livestock: a literature study on the quantitative knowns and unknowns = Routes van tussen-bedrijfstransmissie van zeer besmettelijke dierziekten: een literatuurstudie van de kwantitatieve kennis en kennislacunes

Dit rapport inventariseert de kwantitatieve kennis die beschikbaar is in de literatuur, alsmede de huidige kennislacunes, over de rol van specifieke transmissieroutes in de tussen-bedrijfstransmissie van bestrijdingsplichtige dierziekten in Nederland. Dit om na te gaan in hoeverre een kwantitatieve inschatting van de effecten van specifieke hygienemaatregelen (zowel in vredestijd als in crisis) en contact- en vervoersverboden (in crisistijd) mogelijk is. Op basis van zo’n kwantitatieve inschatting zou namelijk de (kosten)effectiviteit van maatregelenpakketten kunnen worden bestudeerd en mogelijk verbeterd. Daarnaast zou deze informatie ook meer houvast kunnen bieden om voor nieuwe dierhouderijsystemen risico’s van tussen-bedrijfstransmissie in te schatten. Tenslotte zou deze kennis het draagvlak voor naleving van de maatregelen kunnen vergrote

Detection of airborne Campylobacter with three bioaerosol samplers for alarming bacteria transmission in broilers.

In an airborne transmission experiment, Campylobacter in the air was sampled by three types of bioaerosol samplers (all-glass impinger AGI-30, Andersen six-stage impactor, and OMNI-3000) in four broiler rooms. In each room, five 14-day- old broilers inoculated with Campylobacter jejuni were kept in a central cage located in the middle of the room. Another ten broilers, as susceptible animals, were kept individually in ten cages surrounding the central cage at a distance of approximately 75 cm. Air samples were taken on eight days: the day before inoculation (BI) as a negative control, and 1, 3, 6, 9, 14, 21, and 29 days post-inoculation (PI). Presence of C. jejuni was investigated with the culture method for culturable bacteria and with the PCR test for bacterial DNA. Results showed that Campylobacter infection of susceptible broilers occurred in all four rooms; however, no culturable C. jejuni could be detected in any of the air samples. This might have been the result of the low number of broilers in the room and the unfavorable conditions for Campylobacter survival, leading to Campylobacter concentrations below the detection limits of the bioaerosol samplers. The PCR test showed that DNA of C. jejuni was detected in the air samples on the first day PI, but no bacterial DNA was detected on the following days. It is concluded that the three samplers used in this study are not able to alarm Campylobacter outbreaks through an airborne route when low bacterial concentrations are present. Developments of new sampling techniques with low detection limits are required for biosecurity assessment