Evaluation of serology to measure exposure of piglets to Ascaris suum during the nursery phase.

The aim of this study was to evaluate whether serology can be used to measure exposure of piglets to Ascaris suum during the nursery phase. Experimental infection studies were performed in which 7 groups of 10 piglets of 4 weeks of age were orally infected with either 10, 20, 40, 60, 80, 100 and 500 A. suum eggs/day during 7 consecutive weeks, mimicking a nursery phase in an A. suum contaminated environment. Serum was collected on a weekly basis to monitor seroconversion on 2 ELISA tests based on the antibody recognition of either a haemoglobin protein purified from the pseudocoelomic fluid of adult A. suum or a water-soluble complete homogenate of the 3rd stage larvae isolated from the lungs (L3-lung). A dose-dependent seroconversion was measurable with the L3-lung ELISA starting from 4 weeks post-infection onwards, whereas this was not measurable with the haemoglobin-based test. After 7 weeks, equivalent to the end of the nursery phase, the L3-lung ELISA showed a 99% specificity and a 90% sensitivity to detect exposure of piglets to A. suum, with a minimum infection level of 20 A. suum eggs per day. To further evaluate the test under field conditions, a seroprevalence study was performed by sampling 10 piglets on 68 different nursery farms in Belgium. The results showed that for 38% of the farms analysed all piglets tested seronegative, whereas for the remaining 62% of the farms the percentage seropositive piglets ranged from 10 to 100%. This indicates contamination of the nursery facilities with A. suum eggs. In conclusion, the outcome of this study shows that serology can be used to measure exposure of nursery piglets to A. suum, thereby providing an additional tool in the control of this widespread parasite.