Evidence of interaction between Ascaris suum and Metastrongylus apri in experimentally infected pigs.

A study has been carried out with the aim to determine possible interactions between Ascaris suum and Metastrongylus apri under experimentally infected pigs. Twenty-eight Iberian pigs were allocated into four groups. Group 1 was inoculated with 5000 infective A. suum eggs; group 2 received concurrently 5000 infective A. suum eggs and 5000 infective M. apri larvae; group 3 received 5000 infective M. apri larvae; group 4 served as uninfected controls. In each group, pigs were necropsied on day 7 (n = 4) and day 28 (n = 3) post-infection (p.i.). Pigs with single M. apri infections showed earlier and more severe respiratory symptoms compared to pigs with mixed infection, while no clinical signs were observed in pigs single infected with A. suum. Mean burdens of immature A. suum and immature and adult M. apri were reduced in pigs with concomitant infection both on day 7 and 28 p.i., respectively. In contrast, the number of white spots was significantly increased on day 7 in pigs with mixed infection. In addition, pigs of group 1 showed the highest eosinophil levels in blood compared to pigs in groups 2 (intermediate levels) and 3 (moderate levels). The results suggest an antagonistic interaction between A. suum and M. apri in concomitantly infected pigs.