Risk factors associated with excretion of Ascaris suum eggs in loose housed sows and gilts

Loose housing systems for sows may have increased the occurrence and importance of Ascaris suum. Anthelmintic treatments can result in resistance development. Therefore identification of risk factors and development of alternative control strategies is relevant.

The objective of this study was to identify risk factors associated with Ascaris suum egg counts in sows and gilts from intensive farms with loose housed sows.

Twenty sow farms (450 – 2500 sows) were selected from different regions of Denmark. Eight of the farms used routine anthelmintic treatment of breeding animals and 12 farms only performed anthelmintic treatment when considered necessary based on the results of faecal egg counts. From 2012 to 2015, faecal samples were collected from the individual farms at three to five time points. The faecal samples were obtained from 10 gilts and 10 sows at each time point. Nematode egg counts were determined using a McMaster technique. Poisson-regression was used to investigate risk factors associated with A. suum egg counts. Farm was included as a random effect, and fixed effects with a p-value below 0.05 was included in the final model. All statistical analyses were performed using Stata IC 13.

Egg counts were obtained from 784 gilts and 767 sows were included in the statistical analysis. A. suum eggs were detected in 20% of the faecal samples and egg counts were significantly different between breeding animals sampled at different time-points within the same herd (p< 0.001). Egg counts were significantly higher in breeding animals excreting Oesophagostomum spp. eggs (p< 0.001) and in sows compared to gilts (p< 0.001). Routine anthelmintic treatment of breeding animals (p< 0.55) and herd size (p< 0.48) were not significantly associated to egg counts.

Breeding animals in large herds did not have higher egg counts, indicating that increasing herd sizes are not causing increasing problems with A. suum despite the use of loose housing systems for gestating sows.

Breeding animals having an Osophagostomum spp infestation were excreting a higher number of eggs suggesting that similar risk factors are associated with the occurrence of both parasites.

Egg counts for A. suum were not different between animals in herds with or without a routine use of anthelmintic treatment of breeding animals. This indicates that monitoring egg counts in faecal samples combined with anthelmintic treatments when necessary can be used to control infestation with A. suum.

The higher egg counts in sows compared to gilts indicate that sows are important targets for such monitoring procedures and anthelmintic treatment strategies.

Disclosure of Interest: None Declared.