Uitroeiing van schurft op varkensbedrijven

De Projectgroep “Vrijwaring Schurft” heeft van het Programmateam “Diergezondheid in Beweging” de opdracht gekregen om, indien mogelijk, een haalbaar en controleerbaar schurftvrij-programma voor de Nederlandse varkenshouderij te ontwikkelen. De volgende onderzoeksvragen zijn hierbij beantwoord: 1 - Is het mogelijk een ELISA te ontwikkelen voor het aantonen van antilichamen in het bloed tegen de schurftmijt van het varken (Sarcoptes scabiei var. suis), die op het laboratorium routinematig kan worden toegepast? 2- Is het mogelijk om met schurft besmette varkensbedrijven door middel van een tweemalige ivermectine-behandeling van alle aanwezige varkens, aangevuld met hygiënische maatregelen maar zonder ontschurfting van de omgeving, vrij te krijgen van schurft? 3 - Kan een bedrijf dat eenmaal schurftvrij is door middel van uitsluitend hygiënische maatregelen gedurende tenminste één jaar schurftvrij blijven? 4 - Wat is het ingeschatte economische effect van uitroeiing van schurft op praktijkbedrijven

Effect of maternally derived antibodies on the clinical signs and immune response in pigs after primary and secondary infection with an influenza H1N1 virus

The aim of this study was to determine the role of maternally derived antibodies (MDA) against an influenza H1N1 virus in the clinical protection of piglets and especially their effect on the development of the active immunity after an infection with a homologous influenza H1N1 virus. Twenty piglets with MDA and 10 piglets without MDA were housed together and inoculated twice with influenza H1N1 virus, at 7 and 15 weeks of age. Nine piglets without MDA were added to these groups at 12 weeks of age to be inoculated at 15 weeks of age only. Clinical signs, body temperature, growth performance, virus excretion, antibody responses, and influenza-specific T-cell response were monitored. It was shown that MDA protect piglets against the clinical consequences of a primary influenza infection, but that this protection is not complete. A short but significant rise in body temperature was observed and growth seemed to be inhibited due to the infection. Piglets with MDA shed virus for a longer period after an infection than piglets without MDA. Piglets with and without MDA were protected against the clinical consequences of a secondary infection. However, both after primary and secondary infection significant differences in immune responses were observed that indicated that pigs with MDA developed a weaker immunity than pigs without MDA. Furthermore, overall growth performances from weaning to slaughter show a trend in favour of pigs without maternal antibodies, compared to pigs with maternal antibodies, mainly caused by a significant better performance in the second half of the finishing period. The results of this study provide us insight in the role of MDA in clinical protection and their influence on active immunity after an influenza virus infection of pigs. Furthermore, it leads us to the discussion about the profitability of massive sow herd vaccinations in an attempt to increase MDA levels in piglets, taking into account the overall performance of these piglets and the possible effects on antigenic drift

Population dynamics of swine influenza virus in farrow-to-finish and specialised finishing herds in the Netherlands

Influenza virus infections with subtypes H1N1, H3N2 and H1N2 are very common in domestic pigs in Europe. Data on possible differences of population dynamics in finishing pigs in farrow-to-finish herds and in specialised finishing herds are, however, scarce. The presence of sows and weaned piglets on the same premises may, however, affect the exposure of finishing pigs to influenza viruses. In a longitudinal study on 14 farrow-to-finish herds and 15 finishing herds, groups of pigs were followed by repeatedly testing the same animals for antibodies against all three influenza virus subtypes (H1N1, H3N2 and H1N2). At the end of the finishing period, the seroprevalences in farrow-to-finish and specialised finishing herds were 44.3% and 62.0%, respectively for H1N1, 6.6% and 19.3%, respectively for H3N2, and 57.2% and 25.6%, respectively for H1N2. For all three subtypes, the incidence of influenza virus infections was highest at the beginning of the finishing period in farrow-to-finish herds, while the incidence of influenza virus infections was highest at the end of the finishing period in finishing herds. Respiratory disease, probably related to the influenza infections, was observed in five of these herds only, but also occurred at the beginning of the finishing period in farrow-to-finish herds and at the end of the finishing period in finishing herds. The observed differences of population dynamics of influenza virus may affect choice and timing of intervention measure

Estimating the incidence of influenza-virus infections in Dutch weaned piglets using blood samples from a cross-sectional study.

A cross-sectional study was carried out on 32 Dutch breeding herds to estimate the incidence of influenza-virus infections in piglets before the start of the finishing period, at the age of approximately 10 weeks. Longitudinal studies on two herds (8 and 10 litters, respectively) were done to obtain an average decay function for maternal antibodies.Each participating farm in the cross-sectional study was visited twice within 5 months; each time, blood samples were taken randomly from one compartment (a separate room with separate air flow) of 4-5-week-old piglets and one compartment of 8-9-week-old piglets. These blood samples (a total of 2598; 16-23 per compartment, depending on its size) were tested in a haemagglutination inhibition test for antibodies against influenza-virus subtypes H1 and H3. Samples from 8-9-week-old piglets from the first sampling period (n=660) were also tested in an IgM ELISA.For each individual herd and each influenza-virus subtype separately, the decay function derived from the longitudinal studies was used to calculate an expected seroprevalence in 8-9-week-old piglets, which was then compared to the observed seroprevalence. Depending on subtype and sampling period, between 10 and 15 of the 32 herds were suspected of virus circulation during the weaning period because the observed seroprevalence was significantly higher than the expected seroprevalence (

Administration of acidified drinking water to finishing pigs in order to prevent Salmonella infections

The aim of the study was to test whether acidified drinking water, with two millilitres of an acid mixture per litre, was able to reduce the number of Salmonella infections in finishing pig herds. In each compartment, half of the pens were supplied with acidified water and the other pens served as negative control. In three herds the required dose was not applied to the pigs as a result of various practical problems. In another herd, all pigs remained seronegative throughout the study. Analysis of the remaining three herds showed a large and significant treatment effect in one herd (P<0.001). As a result of the small number of observations and the overall lower seroprevalence in the control groups, the other two herds only showed a statistical trend to a treatment effect (0.10<P<0.05). The main practical problem was the clogging of drinking nipples as a result of fungal growth in the pipelines

Administration of acidified drinking water to finishing pigs in order to prevent Salmonella infections

The aim of the study was to test whether acidified drinking water, with two millilitres of an acid mixture per litre, was able to reduce the number of Salmonella infections in finishing pig herds. In each compartment, half of the pens were supplied with acidified water and the other pens served as negative control. In three herds the required dose was not applied to the pigs as a result of various practical problems. In another herd, all pigs remained seronegative throughout the study. Analysis of the remaining three herds showed a large and significant treatment effect in one herd (P<0.001). As a result of the small number of observations and the overall lower seroprevalence in the control groups, the other two herds only showed a statistical trend to a treatment effect (0.10<P<0.05). The main practical problem was the clogging of drinking nipples as a result of fungal growth in the pipelines