False-positive Trichuris suis egg counts in pigs in relation to coprophagia.

Sixteen non-infected control pigs housed together with 16 pigs infected with Trichuris suis, excreted T. suis eggs in their faeces (range 20-4, 960 eggs per gram faeces (EPG)). When the control pigs were moved to clean pens, their egg counts dropped to zero EPG within five days. A significant correlation was found between T. suis egg counts of infected and control pigs penned together (r = 0.89, P < 0.001). These results suggest that false-positive faecal egg counts may be the result of coprophagia.