Johne's disease, improved detection and prevalence

Prevalence of Mycobacterium avium subsp. paratuberculosis fecal shedding in alpacas presented to veterinary hospitals in the United States.

Principal investigator:

Dr. Marie-Eve Fecteau
School of Veterinary Medicine, University of Pennsylvania


Background—The prevalence of Johne’s disease (JD) in alpacas in the United States (US) is unknown. Real-time polymerase chain reaction (RT-PCR) has been used in cattle to quickly and accurately identify Mycobacterium avium subsp paratuberculosis (MAP) in fecal specimens. The limits of PCR detection of MAP in alpaca feces have not been determined.

Objectives—To evaluate the use of PCR for MAP detection in alpaca feces; and to estimate the prevalence of MAP fecal shedding in alpacas presented to veterinary teaching hospitals.

Animals—Alpacas presenting to 4 US veterinary teaching hospitals from November 2009 through February 2011.

Methods—Ten dilutions of a wild MAP strain were added to negative alpaca feces and processed for MAP detection using a commercial RT-PCR assay, and cultured on Herrold’s Egg Yolk Medium (HEYM) and liquid broth. The limits of detection for each method were determined. Fecal samples from alpacas included in the prevalence study were evaluated for MAP via PCR and HEYM.

Results—The lowest MAP dilution detectable via PCR was 243 MAP colony forming units (CFU)/g of feces, at which concentration MAP growth was detectable on HEYM. Ten (6%; 95% confidence interval: 3-9%) of the 180 fecal samples collected were positive on PCR.

Conclusions and clinical importance—PCR can provide an accurate and rapid detection of MAP fecal shedding in alpacas; and the prevalence of MAP fecal shedding in hospitalized alpacas in 4 US veterinary teaching hospitals was 6%.