Usefulness of sero-surveillance for Trichinella infections in animal populations.

In this paper we evaluate serology as a tool to monitor Trichinella-free pig herds. Indoor, industrial-raised fattening pigs in the Netherlands are practically Trichinella-free, and were used as a negative reference cohort. A positive cohort was not available but we used sera from an endemic region in Argentina to model a plausible distribution of serological responses (as OD levels) in positive sera, employing the difference between the endemic sera and the negative Dutch sera. We describe a method for correcting for variation among ELISA plates using on-plate reference sera, and demonstrate how to apply these corrections to a collection of test sera from pig farms. The positive and negative reference distributions can be used to estimate fractions true and false positives, necessary for defining appropriate cutoffs to be used for classifying positive and negative animals. Based on this analysis, the serological test was shown to lack the predictive power required for its large scale deployment. The properties of the serological test were also compared to the conventional digestion assay, which is highly specific but considerably less sensitive.

A survey of gastrointestinal pig parasites on free-range, organic and conventional pig farms in The Netherlands.

The prevalence of gastrointestinal parasites in suckling piglets, weaners, fattening pigs and sows was studied from November 2001 to October 2002 on 16 free-range farms (FRF), 11 organic farms (OF) and 9 conventional farms (CF) by means of faecal examinations of composite samples. Each farm was visited four times with a 3-month interval. Infections with coccidia were found on 43.8% of the FRF, 90.9% of the OF and 66.7% of the CF. Sows had the highest prevalence, particularly on FRF (87.5%) and OF (80%). Ascaris suum was present on 50% of the FRF, 72.7% of the OF and 11.1% of the CF, whereas fattening pigs on FRF (42.9%) and OF (54.5%) had the highest prevalence. Oesophagostomum spp. were observed on 25% of the FRF, 27.2% of the OF and 22.2% of the CF. The infection was most prevalent in the sows on all farm types: 37.5% on FRF, 30% on OF and 22.2% on CF.Trichuris suis was found on 37.5% of the FRF, 36.4% of the OF and 11.1% of the CF. Again, this infection was most prevalent in the sows, particularly on the FRF (50%) and OF (30%). No other gastrointestinal parasite species were found and no clinical signs were observed. No seasonal trends could be distinguished. In many cases, when an age group on a farm was positive for a certain parasite, it remained so during the whole study. This indicates that this parasite was really 'endemic' on that farm. The results of this study demonstrate that the prevalence of helminth infections of pigs on farms with outdoor facilities is higher than in pigs on conventional farms.

[Vaccinations in pig health care in the Netherlands--analysis of a questionnaire among veterinarians]. / Vaccinaties in de Nederlandse varkensgezondheidszorg--analyse van een enquête onder dierenartsen.

Veterinarians specializing in pig health care responded to a questionnaire regarding their experiences with vaccinations. The goal of the questionnaire was to gain insight into a) the reasons for vaccination and b) the factors involved in the efficacy of vaccination. The results indicated that vaccinations were typically initiated because of health problems at the farm. Veterinarians worked together with farmers and other concerned parties to initiate vaccinations. Respondents predicted that the number of vaccinations would decrease substantially with optimal farm management, but would increase if farmers were allowed (under strict conditions) to vaccinate their own pigs. The results further indicated that the nature of financial compensation predicted the rate of vaccination. Veterinarians paid according to a fixed 'fee for service' system vaccinated less frequently than did veterinarians who were paid according to an ongoing farm management contract. In conclusion, veterinarians appear to be restricted in their capacity to disseminate their experience and knowledge due to the competing needs of the farming network (animals, farmers, retailers).