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Epidemiology of Bluetongue virus serotype 8 outbreaks in the Netherlands in 2006. In August 2006 a major epidemic of Bluetongue (bt) occurred in north-western Europe, affecting the Netherlands, Belgium, Germany, Luxemburg, and the north of France. It was caused by bt virus serotype 8 (btv-8), a serotype previously unknown to the eu. Although clinical disease is usually restricted to sheep, this virus also caused clinical disease in a small proportion of cattle. The last clinical outbreak of bt in the Netherlands occurred mid-December 2006. The delay between observation of the first clinical signs by the owner and reporting of a clinically suspect bt situation to the veterinary authorities was approximately 2 weeks. btv-8-associated clinical signs were more prominent in sheep than in cattle, and the relative frequency of specifi c clinical signs was different in cattle and sheep. Morbidity and mortality rates were signifi cantly higher among sheep than among cattle, and a higher proportion of cattle than sheep recovered from clinical disease

On 26th of july 2007 a new case of bluetongue was notified in the Netherlands and on 2nd of august 2007 food and-mouth disease was diagnosed in Surrey, England, which raised the threat of having both infections simultaniously in one area. Bluetongue and foot-and-mouth disease have a different pathogenesis, but symptoms may resemble each other at a later stage of infection. The pathogenesis and possible clinical symptoms of both infections are discussed and illustrated with pictures.

Control of Parasitic gastroenteritis in small ruminants is threatened by the worldwide growing problem of anthelmintic resistance. Therfore, alternativeapproaches for worm control are imperative. Of utmost importance is to slow down selection pressure for anthelmintic resistance by using alternative control measure combined with minimal anthelmintic usage. New control options for the Netherlands are discussed.

Uitleg over de epidemiologie van maagdarmwormen bij schapen, en adviezen om de ontwikkeling van resistentie tegen wormmiddelen te voorkomen. De huidige praktijk van preventieve behandeling van ooien en lammeren werkt de ontwikkeling van resistentie juist in de hand. Om de selectiedruk voor resistentie bij de wormen te verlagen is het belangrijk om niet meer alle schapen tegelijk te behandelen en wormmiddelen uit de verschillende groepen (benzimidazolen; imidithiazoles; avermectines en milbemycines) af te wisselen. Ook een cocktail van middelen is effectief tegen resistentieontwikkeling

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.

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.

Mastitis is an inflammation of the udder, which leads to economic loss, mainly consisting of discarded milk, reduced milk production and quality, and increased health costs. Somatic cell count (SCC), and therefore somatic cell score (SCS), is widely used as indicator of mastitis. In this thesis, I focus on the genetic parameters of SCS as indicator of mastitis, and on the possibilities of using this trait for selection for mastitis resistance in the Valle del Belice dairy sheep. In Chapter 1, mastitis and SCS are defined and introduced. Chapter 2 deals with the estimation of genetic parameters for SCS and milk production traits in primiparous Valle del Belice ewes. Heritability estimates ranged from 0.09 to 0.14 for milk, fat and protein yields and contents. For SCS, the heritability of 0.14 was relatively high. SCS was genetically positively correlated to milk, fat and protein yields and contents. However, correlations were not extreme, so simultaneous improvement for milk yield and SCS seems possible. In Chapter 3, the level of SCC is included in a survival analysis to evaluate the effect of SCC on functional longevity. Results showed that an increase in SCC was associated with an increase in culling rate.Elevated SCC, therefore, play an indirect role in the culling decisions of Valle del Belice dairy sheep farmers, although, at present, farmers do not directly select for reduced SCC. In Chapter 4, the genetic parameters of the infection status and SCS, according to whether the samples were bacteria negative or positive are reported. Moreover, the impact of imperfect sensitivity and specificity on variance component estimates was investigated. The heritability was 0.10 for bacteria negative SCS, 0.03 for bacteria positive SCS, and 0.09 for infection status, on the liability scale. The genetic correlation between bacteria negative and bacteria positive SCS (0.62) suggests that they may be genetically different traits, confirming that SCSfrom healthy and infected animals should be analyzed separately. Moreover, a positive genetic correlation between bacteria negative SCS and liability to mastitis was found, suggesting that the approach of selecting animals for decreased SCS will help to reduce the prevalence of mastitis. The results also showed that the imperfect diagnosis of infection has an impact on estimated genetic parameters,which may reduce the efficiency of selection strategies aiming at distinguishing between bacteria negative and bacteria positive SCS. In Chapter 5, the diagnostic ability of SCCand California Mastitis Test (CMT) to detect intramammary infectionswas evaluated by using the Receiver-Operating Characteristic(ROC) curves, in order to identify a SCCthreshold that better discriminated healthy from infected udders. The results indicate that the CMT can only discriminate the udders infected from major pathogens. Nevertheless, in general SCS was the best indirect test for the bacteriological status of the udder. The final chapter explores and discusses the opportunities to use SCS as indicator of mastitis in a selection scheme to improve mastitis resistance for the Valle del Belice dairy sheep breed.

Mastitis is an inflammation of the udder, which leads to economic loss, mainly consisting of discarded milk, reduced milk production and quality, and increased health costs. Somatic cell count (SCC), and therefore somatic cell score (SCS), is widely used as indicator of mastitis. In this thesis, I focus on the genetic parameters of SCS as indicator of mastitis, and on the possibilities of using this trait for selection for mastitis resistance in the Valle del Belice dairy sheep. In Chapter 1, mastitis and SCS are defined and introduced. Chapter 2 deals with the estimation of genetic parameters for SCS and milk production traits in primiparous Valle del Belice ewes. Heritability estimates ranged from 0.09 to 0.14 for milk, fat and protein yields and contents. For SCS, the heritability of 0.14 was relatively high. SCS was genetically positively correlated to milk, fat and protein yields and contents. However, correlations were not extreme, so simultaneous improvement for milk yield and SCS seems possible. In Chapter 3, the level of SCC is included in a survival analysis to evaluate the effect of SCC on functional longevity. Results showed that an increase in SCC was associated with an increase in culling rate.Elevated SCC, therefore, play an indirect role in the culling decisions of Valle del Belice dairy sheep farmers, although, at present, farmers do not directly select for reduced SCC. In Chapter 4, the genetic parameters of the infection status and SCS, according to whether the samples were bacteria negative or positive are reported. Moreover, the impact of imperfect sensitivity and specificity on variance component estimates was investigated. The heritability was 0.10 for bacteria negative SCS, 0.03 for bacteria positive SCS, and 0.09 for infection status, on the liability scale. The genetic correlation between bacteria negative and bacteria positive SCS (0.62) suggests that they may be genetically different traits, confirming that SCSfrom healthy and infected animals should be analyzed separately. Moreover, a positive genetic correlation between bacteria negative SCS and liability to mastitis was found, suggesting that the approach of selecting animals for decreased SCS will help to reduce the prevalence of mastitis. The results also showed that the imperfect diagnosis of infection has an impact on estimated genetic parameters,which may reduce the efficiency of selection strategies aiming at distinguishing between bacteria negative and bacteria positive SCS. In Chapter 5, the diagnostic ability of SCCand California Mastitis Test (CMT) to detect intramammary infectionswas evaluated by using the Receiver-Operating Characteristic(ROC) curves, in order to identify a SCCthreshold that better discriminated healthy from infected udders. The results indicate that the CMT can only discriminate the udders infected from major pathogens. Nevertheless, in general SCS was the best indirect test for the bacteriological status of the udder. The final chapter explores and discusses the opportunities to use SCS as indicator of mastitis in a selection scheme to improve mastitis resistance for the Valle del Belice dairy sheep breed.

Rift Valley Fever (RVF) is a zoonotic vector-borne infection and causes a potentially severe disease in both humans and young animals. The Ministry of Economic Affairs, Agriculture and Innovation (EL&I) is interested in the risk of an outbreak of Rift Valley Fever virus (RVFV) for the Netherlands, and more knowledge is needed about the risk of introduction of the virus, the risk of spread (transmission) of the virus in the country once introduced, and the methods for control and surveillance. For this purpose, a mathematical model was developed to study (1) the probability of a RVF outbreak at different days of introduction during the year, (2) the probability of persistence of the infection during the entire year, and (3) outbreak size and duration at different days of introduction during the year.

Rift Valley Fever (RVF) is a zoonotic vector-borne infection and causes a potentially severe disease in both humans and young animals. The Ministry of Economic Affairs, Agriculture and Innovation (EL&I) is interested in the risk of an outbreak of Rift Valley Fever virus (RVFV) for the Netherlands, and more knowledge is needed about the risk of introduction of the virus, the risk of spread (transmission) of the virus in the country once introduced, and the methods for control and surveillance. For this purpose, a mathematical model was developed to study (1) the probability of a RVF outbreak at different days of introduction during the year, (2) the probability of persistence of the infection during the entire year, and (3) outbreak size and duration at different days of introduction during the year.

De rode lebmaagworm Haemonchus zorgde in de zomer van 2007 voor meer problemen dan in andere jaren. Voor de bescherming van de lammeren is het vooral erg belangrijk om de ooien in het voorjaar te ontwormen

Het LEI is door LNV in overleg met het PVE gevraagd om een analyse te doen naar de financiële draagkracht van de schapen- en de geitenhouderij wat betreft de kosten van een centrale registratie van individuele dieren (I&R). De noodzaak of gewenstheid om met het oog op het diergezondheidbeleid een I&R stelsel in te voeren voor schapen en geiten is geen onderwerp van discussie; de dieren moeten getraceerd kunnen worden in geval van een ziekte-uitbraak. De centrale vraag is dan ook wat betekent de lastenverzwaring met (ruim) 2 mln. euro voor de sector schapen- en geitenhouderij en is hiervoor financiële draagkracht. Gevraagd wordt aan het LEI na te gaan met welke financieel-economische gegevens (kengetallen) de draagkracht in beeld gebracht kan worden. In deze notitie geeft het LEI een analyse op basis van gegevens met betrekking tot de structuur en de financiële gegevens en resultaten van de schapen- en geitenhouderij

Epidemiology of Bluetongue virus serotype 8 outbreaks in the Netherlands in 2006. In August 2006 a major epidemic of Bluetongue (bt) occurred in north-western Europe, affecting the Netherlands, Belgium, Germany, Luxemburg, and the north of France. It was caused by bt virus serotype 8 (btv-8), a serotype previously unknown to the eu. Although clinical disease is usually restricted to sheep, this virus also caused clinical disease in a small proportion of cattle. The last clinical outbreak of bt in the Netherlands occurred mid-December 2006. The delay between observation of the first clinical signs by the owner and reporting of a clinically suspect bt situation to the veterinary authorities was approximately 2 weeks. btv-8-associated clinical signs were more prominent in sheep than in cattle, and the relative frequency of specifi c clinical signs was different in cattle and sheep. Morbidity and mortality rates were signifi cantly higher among sheep than among cattle, and a higher proportion of cattle than sheep recovered from clinical disease Beschrijving van de grote bluetongue-epidemie bij rundvee en schapen in Noordwest-Europa van 2006. De epidemie werd veroorzaakt door het bluetongue-virusserotype 8 (BTV-8). Morbiditeit en mortaliteit waren aanzienlijk hoger op bedrijven met schapen dan op bedrijven met rundvee

Het LEI is door LNV in overleg met het PVE gevraagd om een analyse te doen naar de financiële draagkracht van de schapen- en de geitenhouderij wat betreft de kosten van een centrale registratie van individuele dieren (I&R). De noodzaak of gewenstheid om met het oog op het diergezondheidbeleid een I&R stelsel in te voeren voor schapen en geiten is geen onderwerp van discussie; de dieren moeten getraceerd kunnen worden in geval van een ziekte-uitbraak. De centrale vraag is dan ook wat betekent de lastenverzwaring met (ruim) 2 mln. euro voor de sector schapen- en geitenhouderij en is hiervoor financiële draagkracht. Gevraagd wordt aan het LEI na te gaan met welke financieel-economische gegevens (kengetallen) de draagkracht in beeld gebracht kan worden. In deze notitie geeft het LEI een analyse op basis van gegevens met betrekking tot de structuur en de financiële gegevens en resultaten van de schapen- en geitenhouderij