Diagnostics for parasites - what do we know, where do we go?

Ascaris suum is currently the only parasitic worm that is still highly prevalent in modern intensive pig production systems. However, due to the subclinical nature of the disease, ascariasis often remains undiagnosed, creating a lack of information regarding the worm-status of a farm, which ultimately makes it difficult for the farmers and the veterinarians to evaluate the applied deworming programs. In recent years, our group has developed and evaluated a serological test that can be used to measure parasitic exposure of fattening pigs more accurately. The test is based on the recognition of a haemoglobin protein (AsHb) produced by the parasite leading to a systemic IgG antibody response in exposed animals (Vlaminck et al., 2012). Evaluation of the test under field conditions have demonstrated a superior sensitivity for the detection of A. suum infections in comparison to faecal egg counts and liver white spots. A recent seroprevalence study performed with this test on over 500 European porc production facilities indicated the high prevalence of A. suum in fatteners, with approximately 50 % of the farms analysed testing positive. Furthermore, in order to increase our understanding of the impact of Ascaris on farm productivity, serological data of 20 fattening farms was compared with slaughterhouse data (such as percentage of affected livers, pleuritis and lung lesions) and farm performance parameters (such as feed conversion efficiency, days to market, daily weight gain, carcass quality and mortality). A significant correlation was observed between serology and production parameters, such as days to market and average daily growth, further indicating that A. suum infections can have a significant impact on farm economical parameters (Vlaminck et al., 2015). Furthermore, the results also indicate that serology forms an attractive new diagnostic tool that can be used to measure infection intensities. Currently, we are using serology to identify potential risk-factors associated with Ascaris infections and to measure the impact of applied control strategies. Also, the use of serology in sows and piglets is under further evaluation in order to determine the potential role of these animals in the widespread occurrence of Ascaris in fattening pigs.