NECROPSY AND SAMPLING
Any Australian mammal with suspected mycobacteriosis that dies or is euthanased should be necropsied. Most NTM have zoonotic potential and it is recommended that PPE including respiratory, oral and eye protection is used when performing necropsies when mycobacteriosis is suspected.
Tuberculous mycobacteriosis of all species is a serious zoonotic disease. If suspected, PPE should include additional respiratory protection, such as a full-face positive-pressure respirator, or at the very minimum an N95- rated respiratory mask and eye protection.At necropsy, alongside routine sampling of a set of fixed tissues, it is important to collect fresh tissue samples from suspected mycobacterial lesions for microbiological work-up and/or freezing. A list of recommended samples that should be taken together with the recommended testing protocol is provided in Table 22.6.
Table 22.6. Recommend necropsy sampling and testing protocol for cases of suspected or known mycobacteriosis
| Sample | Test details | Ideal location of testing |
| Samples for immediate testing | ||
| Fresh tissue from lesions | Microscopy: impression smear with ZN stain Culture: mycobacterial specific culture ± PCR PCR: confirmation of mycobacterial species if culture alone is inconclusive PCR: rapid inclusion or exclusion of M. tuberculosis complex if indicated | Routine diagnostic laboratory, or mycobacterial reference laboratory Mycobacterial reference laboratory Ideally, send tissue to laboratory immediately and chilled (4°C) or if there is a necessary delay, freeze tissue (at -80°C if available) |
| Formalin-fixed tissues (10% | Ideally, a 'full set' of tissues as per routine necropsy. | Routine examination by a diagnostic |
| neutral buffered formalin) | Include thoracic and abdominal lymph nodes and any suspected abnormal tissues | anatomical veterinary pathologist |
| Samples for storage | ||
| Frozen tissue from lesions | Future culture and/or PCR if not conducted immediately at necropsy | Samples from suspected and confirmed cases should be held long-term, ideally at -80°C or -20°C. Keep on site or at trusted laboratory/facility |