D.M. Bontje’s scientific contributions

Between 2006 and 2009 the largest human Q fever epidemic ever described occurred in the Netherlands. The source of infection was traced back to dairy goat herds with abortion problems due to Q fever. The first aim of control measures taken in these herds was the reduction of human exposure. To analyze Q fever dynamics in goat herds and to study the effect of control measures, a within-herd model of Coxiella burnetii transmission in dairy goat herds was developed. With this individual-based stochastic model we evaluated six control strategies and three herd management styles and studied which strategy leads to a lower Q fever prevalence and/or to disease extinction in a goat herd. Parameter values were based on literature and on experimental work. The model could not be validated with independent data.

In this report, we investigate the expected effects of reducing the area in which live piglet transports are banned on transmission risk and on the piglet surplus (in the area of the transport ban) during a CSF epidemic in the Netherlands.

Even though low pathogenic avian influenza viruses (LPAIv) affect the poultry industry of several countries in the world, information about their transmission characteristics in poultry is sparse. Outbreak reports of LPAIv in layer chickens have described drops in egg production that appear to be correlated with the virus transmission dynamics. The objective of this study was to use egg production data from LPAIv infected layer flocks to quantify the within-flock transmission parameters of the virus. Egg production data from two commercial layer chicken flocks which were infected with an H7N3 LPAIv were used for this study. In addition, an isolate of the H7N3 LPAIv causing these outbreaks was used in a transmission experiment. The field and experimental estimates showed that this is a virus with high transmission characteristics. Furthermore, with the field method, the day of introduction of the virus into the flock was estimated. The method here presented uses compartmental models that assume homogeneous mixing. This method is, therefore, best suited to study transmission in commercial flocks with a litter (floor-reared) housing system. It would also perform better, when used to study transmission retrospectively, after the outbreak has finished and there is egg production data from recovered chickens. This method cannot be used when a flock was affected with a LPAIv with low transmission characteristics (R(0)<2), since the drop in egg production would be low and likely to be confounded with the expected decrease in production due to aging of the flock. Because only two flocks were used for this analysis, this study is a preliminary basis for a proof of principle that transmission parameters of LPAIv infections in layer chicken flocks could be quantified using the egg production data from affected flocks.

De vraagstelling voor deze studie luidt: in welke mate neemt het risico op verspreiding van Mond-en-Klauwzeer toe als de huidige Regeling Preventie, bestrijding en monitoring van besmettelijke dierziekten en zoönosen en TSE’s (Regeling preventie) zodanig zou worden aangepast dat schapen vanaf een verzamelcentrum naar een weidebedrijf vervoerd mogen worden? Vervolgens bestaat de aanpak van deze studie uit de volgende onderdelen: - studie van de huidige verplaatsingen zoals gemeld in Identificatie & Registratie (I&R); - interviews met deskundigen; - epidemiologische risicoberekeningen; - economische analyse van de directe kosten; - gevoeligheidsanalyse van de uitkomsten voor (parameter)onzekerheden. De berekeningen richten zich op het scenario dat insleep van MKZ in Nederland op een schapenbedrijf plaatsvindt dat is gelegen in de Gelderse Vallei. De focus ligt hierbij op het percentage waarmee het risico van MKZ-verspreiding zou veranderen na aanpassing van de Regeling preventie.