Natural Ascaris suum infections in swine diagnosed by coprological and serological (ELISA) methods

Paired samples of faeces and blood were collected from weaners (W), fatteners (F), lactating sows (S) and piglets (P) in 20 Danish sow herds. The samples were examined by a McMaster technique for Ascaris suum eggs and an indirect ELISA for anti-A. suum IgG. The coprological and serological results were significantly correlated for W and F (P < 0.0001) but not for S (P = 0.35). The coproprevalences were much lower (W 4.0%, F 15.5%, S 7.4%) than the seroprevalences (W 20.3%, F 50.5%, S 65.4%). Thus, egg counts greatly underestimate the proportion and number of A. suum-exposed pigs even in the young susceptible age groups. The ELISA ODs of the piglets were closely correlated with those of their mothers (P < 0.0001), although the mean OD decreased gradually from 111% of the mean sow OD in the 1st week of life to 48% at 5-6 weeks of age. It is concluded that the ELISA technique gives a more realistic impression of A. suum exposure levels in swine herds than do faecal egg counts.