[Serological studies in wild boars in the Veluwe area]

In the second part of 1994, blood samples from 115 wild swine are tested for gE-antibodies to Aujeszky Disease Virus. Three of the blood samples reacted positive. The tests for Classical Swine Fever and for Swine Vesicular Disease were negative in all samples. Perhaps the wild swine do not form a source of infection to the surrounding area with regard to these viral diseases but they may play a role as indicator for circulating viruses in the surrounding area.

[Logbook registration in slaughtering pig farms within the project Integrated Quality Control. II. Drug utilization in relation to clinical observation, farm conditions and prevalence of pathological findings]

During an Integrated Quality Control (IQC) project for finishing pigs, the application of veterinary drugs was registered by means of a logbook on 75 pig finishing farms. Investigated is as to how far the application of veterinary drugs to animals is linked up with clinical observations, management and climatic conditions on the farm and to what extent the application of veterinary drugs is linked up with the occurrence of pathological findings in pigs at the slaughterhouse. The results indicate that more veterinary drugs are used as there are more clinical findings on a pig farm. This is particularly true for the autumn-winter period. Farms that use more veterinary drugs have a higher percentage of pigs with pathological findings at the slaughterhouse. As the point of time of treatment of respiratory disorders is closer to the slaughter date, there is a higher percentage of pigs suffering from pneumonia at the slaughterhouse. Farms treating pigs in the first thirty days of the finishing period against intestinal disorders have a distinct higher percentage of pigs suffering from pneumonia at the slaughterhouse. It appears that less veterinary drugs are used at farms having specific housing and management characteristics.

Variation in seropositivity for some respiratory disease agents in finishing pigs: epidemiological studies on some health parameters and farm and management conditions in the herds

The relationship between the extent of seropositivity for Aujeszky's disease virus (ADV), Actinobacillus pleuropneumoniae (App.) serotype 2 and porcine influenza (PI) viruses serotype H1N1 and H3N2 in pigs on the one hand and the health status of the pigs and some farm and management conditions in the herds on the other hand was studied in 45 pig finishing herds, all members of one integration group. The health status was assessed by the extent of clinical signs, the use of veterinary drugs and the prevalence of pathological lesions in pigs at slaughter. There was no relationship between the extent of seropositivity on the one hand and clinical signs and use of veterinary drugs on the other hand. However, there was a positive relationship between the extent of seropositivity and the percentage of pigs with lesions of the respiratory tract at slaughter. Furthermore, the study indicates that the variation in seropositivity between pigs herds is associated with management related factors that particularly influence the possibility of the spreading of viruses. A sero-epidemiological investigation in 14 pig herds with recurrent pneumonia problems revealed a high percentage of seropositive pigs per herd. Furthermore, in a large number of herds, pigs were simultaneously seropositive for ADV and App. serotype 2, for ADV and PI serotype H1N1 or for ADV and PI serotype H3N2.

Sero-epidemiological screening of pig sera collected at the slaughterhouse to detect herds infected with Aujeszky's disease virus, porcine influenza virus and Actinobacillus (Haemophilus) pleuropneumoniae in the framework of an integrated quality control (IQC) system

Over a period of six months, approximately 4700 blood samples were collected from 97 pig-finishing farms in the provinces of Noord-Brabant and Gelderland and screened for antibodies with respect to Aujeszky's disease virus (ADV), porcine influenza virus (PI) and Actinobacillus (Haemophilus) pleuropneumoniae (App). There were significant differences in the percentages of seropositive pigs between the two provinces, which may be related to the difference in the density of the pig population in the two provinces. In practice, it was possible to perform a reliable sera collecting procedure at the slaughterhouse. No farms remained seronegative with respect to most of the disease agents during the sampling period. There was a high degree of variation in the percentages of seropositive pigs per farm as to most of the disease agents. Evidence was found that animals that were seropositive with respect to ADV were significantly more susceptible to becoming seropositive with respect to App. serotype 2, and vice versa. The same connection was observed for PI serotype H1N1 and PI serotype H3N2. Furthermore, evidence was found that pigs seropositive with respect to PI serotype H1Ni only, or to PI serotype H1N1 and ADV or PI serotype H3N2 show a significant decrease in average daily weight gain compared to pigs that were seronegative.

[Log book registration of farms for slaughtering pigs in the Integrated Quality Control Project. I. Use of drugs and vaccines]

Log book recording was done for twelve months on approximately 100 pig finishing farms in an Integrated Quality Control (IQC) project. This recording was designed to gain a better understanding of the extent and nature of the medication and vaccination on these farms. Vaccination against Aujeszky's disease was done on the majority of farms. This vaccination mainly consisted in a single, frequently intramuscular, injection. Vaccinations against swine influenza and infections due to Actinobacillus (Haemophilus) pleuropneumoniae were merely sporadic. The animals were dewormed in 58 per cent of the finishing periods, whereas they were given preventive treatment for sarcoptic mange in 23 per cent of the finishing periods. Not a single pig was treated with antibiotics and/or chemotherapeutic agents in 12.5 per cent of the finishing periods. The majority of finishing periods in which treatment was not carried out, were those having closed pig herds. To the extent that the farms were supplied with piglets by more breeders, there were fewer finishing periods during which treatment was omitted. The great majority of cases in which individual therapy was given, were treated for respiratory disorders. On 27 per cent of the farms, more than 10 per cent of the animals per finishing period were treated for respiratory disorders. Group medication was much less frequent: intestinal disorders did not have to be treated on 31 per cent of the farms, and 16 per cent did not require treatment for respiratory disorders. In the great majority of cases in which group treatment was required, this was given during the first sixty days of the finishing period. In view of the fact that there are marked differences in the degree to which pigs have to be medicated on the farms, recording the use of veterinary drugs on farms, could fulfil the function of a signal. On the basis of these signals, measures may be suggested in herd management programmes to ensure an effective and minimum use of veterinary drugs. Using a log book will also enable the pig farmer to estimate whether groups of animals may be sent to the slaughter-house without involving risks to public health.

[Streptococcus suis type 2 in swine. An imported problem?]

Investigations were carried out on eighteen farms in the Province of Gelderland to determine whether it was possible to use biopsy specimens of the tonsils to differentiate between farms with clinical problems caused by Streptococcus suis type 2 and farms without these problems. The proportion of carriers of this organism on the farms was 14 per cent and 2 per cent respectively, so that this differentiation is feasible. It was also studied whether this proportion differed on farms which imported pigs from Great Britain and farms which did not do so; the proportion of carriers on farms having animals imported from Great Britain was found to be higher than that on farms not using these importations, viz., 17 per cent and one per cent respectively.