Hemorrhagic Tracheitis Standardized Submissions to Help Find Etiology Supported by SHIC

Hemorrhagic tracheitis syndrome (HTS) has been diagnosed in Canada for years, and recently increasingly recognized in the US. To date, no etiologic agent(s) has been definitively or consistently associated with the syndrome in the cases examined or reported. To investigate etiology, a joint project of the Iowa State University Veterinary Diagnostic Lab (ISU VDL), Animal Health Laboratory, University of Guelph (AHL-UG), and the Laboratoire de santé animale, MAPAQ,Québec has begun with support from SHIC. Diagnostic investigations at both ISU VDL and AHL-UG to date for tracheitis cases have been hampered by dependence on the submitter’s tissue sampling and diagnostic test selection. A standardized diagnostic test plan for swine tracheitis cases has been developed. This joint VDL project will facilitate thorough, consistent testing of these cases, allow staff to exclude common respiratory pathogens as the cause of tracheitis in individual animals and herds, and establish a tissue bank for future NGS to search for novel or emerging pathogens in those cases with no confirmed etiologic diagnosis.

This spring, the Swine Health Information Center (SHIC) and America Association of Swine Veterinarians co-hosted a webinar providing information on the syndrome, its signalments, tissues for postmortem assessment, and management. The webinar is available to view here.

Severe necrohemorrhagic tracheitis syndrome observed in finishing pigs and replacement breeding stock is characterized by severe erosive or ulcerative lesions. Transient outbreaks are reported, with herd resolution over a period of two to three weeks. Opportunistic bacterial infection is common among the tracheal lesions at the time of necropsy and evaluation. The temporal pattern, clinical signs, and gross and histologic lesions of severe necrohemorrhagic tracheitis, together with the failure to consistently identify any known respiratory pathogen in many of the cases, raises concern of either a novel infectious agent or a novel strain of a known infectious agent. Alternatively, the lesion may represent a stereotypic sequel to a variety of primary cause. Contribution of anatomic features (e.g. tracheal diameter, length) compressive effects of cervical lymphadenopathy, genetic factors, and environmental/air quality conditions to the development and severity of tracheitis must be considered.

Morbidity ranges from <1% to 10 to 50%, depending on the herd, with consistently low mortality (<1-3%). Clinical signs resolve over seven to 10 days, sometimes in response to antibiotic and/or anti-inflammatory therapy; however, resolution was noted in some herds with no or minimal treatment or interventions.

The following represents desired submissions for the HTS study at participating VDLs to develop a diagnostic investigation protocol and establishment of a tissue bank. Samples should be sent using each facility’s particular submission forms.