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Systemic mycobacteriosis caused by Mycobacterium avium subspecies hominissuis in a sheep

Nagaraja Thirumalapura1, Susan Bender2, Manoj K Sekhwal3

  • 1Wisconsin Veterinary Diagnostic Laboratory, University of Wisconsin-Madison, Madison, WI, USA.

Journal of Veterinary Diagnostic Investigation : Official Publication of the American Association of Veterinary Laboratory Diagnosticians, Inc
|July 11, 2026
PubMed

Insights

Mycobacterium avium subsp. hominissuis (MAH) caused systemic mycobacteriosis in a sheep, presenting with granulomatous lesions. This finding highlights MAH as a potential pathogen in sheep and its implications for diagnostics.

Area of Science:

  • Veterinary Pathology
  • Infectious Diseases
  • Genomics

Background:

  • Mycobacterium avium subsp. hominissuis (MAH) is known to cause infections in humans and pigs.
  • MAH infections are less commonly reported in other animal species, including sheep.

Purpose of the Study:

  • To report a case of systemic mycobacteriosis caused by MAH in a sheep.
  • To characterize the MAH isolate and identify potential diagnostic interferences.

Main Methods:

  • Clinical case reporting and gross pathology.
  • Histopathological examination of tissues.
  • Bacterial isolation and whole-genome sequencing.

Main Results:

  • A sheep presented with hypoproteinemia, weight loss, fever, and disseminated granulomatous lesions.
  • MAH was isolated from multiple tissues and feces.
  • Whole-genome sequencing identified an ISMAP02-like sequence, potentially interfering with MAP PCR detection.

Conclusions:

  • This case demonstrates systemic mycobacteriosis caused by MAH in a sheep.
  • The presence of an ISMAP02-like sequence in MAH may affect diagnostic accuracy for Mycobacterium avium subsp. paratuberculosis (MAP).
Keywords:
Mycobacterium avium subsphominissuismycobacteriosisovinesheep

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