Research confirms Ornithobacterium rhinotracheale as secondary pathogen in commercial turkeys

Recent research on Ornithobacterium rhinotracheale (ORT) identified the pathogen as a frequent secondary coinfection during respiratory outbreaks in poultry, with a higher incidence in turkeys.

Sara Abdel-Mawgod, DVM, PhD, Iowa State University, conducted the research after detecting ORT in healthy birds without clinical symptoms.

“Although ORT is associated with respiratory manifestation, it is also detected in healthy birds that are not displaying clinical signs of illness,” Abdel-Mawgod said. “Thus, the presence of ORT doesn’t always result in clinical disease.

“This brought us to a question: Is ORT a primary or secondary pathogen?” she continued. “And a second question was, if ORT is a primary pathogen, what is the source and timing of its infections?”

Abdel-Mawgod presented her ORT research at the 2026 North Central Avian Disease Conference.

Testing turkey flocks for ORT

“To answer these questions, our plan of work involved turkey sampling through both cross-sectional sessions and longitudinal sites,” Abdel-Mawgod said.

The cross-sectional sampling was conducted on apparently healthy birds during quarterly gut-health checks for coccidia and included five pooled tracheas and five pooled lungs from different flocks at different times of the year.

“Our workflow started with receiving the tissue samples and processing them using tissue homogenizer, followed by DNA extraction and real-time PCR. If the samples were positive for ORT, we went a step further and conducted bacterial isolation,” she explained.

The cross-sectional sessions involved 177 flocks. Testing demonstrated that 109 of the flocks were positive for ORT — a 62% positivity rate. Before testing, Abdel-Mawgod said that 150 of the flocks appeared healthy, but 95 tested positive, for a 63% positivity rate.

The 27 flocks that appeared diseased were divided into respiratory (13 flocks) and digestive disease groups (14 flocks). The flocks with respiratory illness had 54% positivity for ORT, with seven flocks infected. The flocks with signs of digestive illness had a 50% positivity rate, with seven flocks testing positive for ORT. Both were lower than the positivity rate of apparently healthy flocks, contradicting a correlation between ORT and clinical disease.

Prevalence of ORT with E. coli

“We have a high prevalence of ORT detection in apparently healthy turkey flocks,” Abdel-Mawgod said. “The second step of the research compared the prevalence of ORT with the known secondary pathogen Escherichia coli and the known primary pathogen Pasteurella multocida.”

The research team used 97 turkey flocks, with 84 appearing healthy and the remaining 13 appearing diseased.

PCR results indicated that 80 of the 84 healthy flocks were positive for E. coli, and 61 of the 84 flocks were positive for ORT. Of the 13 flocks showing disease, 11 were positive for E. coli, and seven were positive for ORT. All flocks were negative for P. multocida.

“The ORT detection percentage showed high similarity to the secondary pathogen E. coli,” Abdel-Mawgod stated.

Longitudinal study

“For our longitudinal flocks, we took respiratory samples from the trachea and lung and also obtained environmental samples from litter, feed and drinker swabs,” she said.

They conducted testing from 2022 to 2026 in a sample of flocks from Iowa, Ohio, Minnesota and South Dakota. Each flock was tested at 12 time points, starting on the day of placement through 9 weeks of age.

The samples were processed, followed by DNA extraction and real-time PCR testing for ORT. Bacterial isolation was subsequently performed on samples that tested positive by PCR.

“We obtained 19 longitudinal flocks divided into 10 case sites, with 584 total samples and 125 samples positive for ORT — a 21% positivity rate,” Abdel-Mawgod said. “In our nine control sites, we obtained 508 samples. Of these, 82 tested positive, for a 16% positivity rate.”

This research also included a time-comparison study to determine when a flock’s respiratory organs and environmental samples test positive for ORT.

“We found the earliest ORT detection was in respiratory samples at 4 days old and increasing rapidly to the age of 6 weeks,” she said. “ORT was first detected in environmental samples at 14 days of age. From 7 to 9 weeks of age, we find the highest positivity detection for ORT from both sources.”

ORT as secondary pathogen

“Our take-home message would be that ORT was detected in 63% of the apparently healthy turkey flocks, and flocks with respiratory signs were 54% positive for ORT,” Abdel-Mawgod stated.

“Overall, ORT is behaving more similarly to E. coli than P. multocida, which means that ORT is following the pattern of secondary infection in both the case and control sites,” she concluded.

The post Research confirms Ornithobacterium rhinotracheale as secondary pathogen in commercial turkeys appeared first on Modern Poultry.