Use of trachea-bronchial swab qPCR testing to confirm seropositivity in an SPF breeding herd.

Background: A dedicated program to monitor for freedom of several economically important diseases is present within most of the breeding companies that currently deliver high health breeding animals to their customers. Serology is therefore the preferential approach in order to screen for most of these diseases, including (). However, in case of positive serology, further decisions on farm health status and the related consequences should be based on additional confirmation tests.

Case Presentation: The current case report demonstrates that tracheo-bronchial swab (TBS) sampling is a suitable alternative to confirm a suspect -seropositive situation. A Central-European SPF herd was shown positive (90% positive, 10% suspect;  = 10) for using the conventional ELISA serology (Idexx HerdChek Mhyo ELISA) and a second ELISA test (IDEIA™ EIA kit) did not exclude potential infection (10% positive, 70% suspect; n = 10). Further follow-up remained inconclusive on both tests. Throughout the entire monitoring period of 6 months, no coughing, necropsy lesions or lesions at slaughter could be detected which could confirm the health status. TBS sampling was used to confirm the health status for . In total, 162 samples were collected at different ages ( = 18 per age category): piglets at 3-6-9-12 and 15 wks of age, rearing gilts at 18-21-24 and 27 weeks of age. Collected TBS samples were negative for until 15 wks of age, but rearing gilts were highly -positive from 18 wks onwards with 87-100% -positive animals and PCR Ct-values between 25 and 33.

Conclusions: This case report shows that collection of TBS samples to confirm the infection status of a breeding herd was able to provide additional information to serology in order to make crucial decisions concerning health management and eradication strategies within the breeding herd.