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Mycobacterium avium subsp. hominissuis infection in horses with granulomatous enterocolitis – first report in Poland Cover

Mycobacterium avium subsp. hominissuis infection in horses with granulomatous enterocolitis – first report in Poland

Journal of Veterinary Research
AHEAD OF PRINT
By: Beata Nowicka,  Wojciech Łopuszyński,  Monika Krajewska-Wędzina,  Anna Biazik,  Magdalena Sobuś,  Izabela Polkowska and  Ewelina Szacawa  
Open Access
|Dec 2025

Figures & Tables

Fig. 1.

Gross pathology photographs of tissue sections from Polish horses with granulomatous enterocolitis. a – Markedly enlarged mesenteric lymph nodes, the segment of the small intestine drained by thick, dilated mesenteric lymphatic vessels (mesenteric lymphangitis/lymphangiectasia); b – Large colon (sternal/diaphragmatic flexure): colonic lymph nodes enlarged to a size of 1–3 cm in diameter; c – Large colon (pelvic flexure) with diffusely, markedly thickened mucosa; d – Large colon, irregularly transversely folded mucosal rugae with multifocal superficial erosions
Gross pathology photographs of tissue sections from Polish horses with granulomatous enterocolitis. a – Markedly enlarged mesenteric lymph nodes, the segment of the small intestine drained by thick, dilated mesenteric lymphatic vessels (mesenteric lymphangitis/lymphangiectasia); b – Large colon (sternal/diaphragmatic flexure): colonic lymph nodes enlarged to a size of 1–3 cm in diameter; c – Large colon (pelvic flexure) with diffusely, markedly thickened mucosa; d – Large colon, irregularly transversely folded mucosal rugae with multifocal superficial erosions

Fig. 2.

Micrographs of tissue samples from Polish horses with granulomatous enterocolitis. a – Haematoxylin and eosin (HE)-stained cross section through a large colon wall and adjacent lymph nodes. Massive granulomatous inflammatory infiltrates in the mucosa and submucosa and in the adjacent lymph node parenchyma. Remnants of lymphoid follicles visible in the cortex. Scale bar = 2000 μm; b – HE-stained lamina propria and submucosa of the large colon widely infiltrated by epithelioid macrophages and aggregates of lymphocytes and plasma cells; multinucleated giant cells with peripherally located nuclei (insert). Scale bar = 200 μm; c – HE-stained cross section through a mesenteric lymphatic vessel occluded by epithelioid macrophages, multinucleated giant cells and fewer lymphocytes and plasma cells. Scale bar = 500 μm; d – Ziehl–Neelsen-stained large colon with numerous macrophages in the lamina propria and submucosa containing intracellular acid-fast bacteria. Scale bar = 100 μm
Micrographs of tissue samples from Polish horses with granulomatous enterocolitis. a – Haematoxylin and eosin (HE)-stained cross section through a large colon wall and adjacent lymph nodes. Massive granulomatous inflammatory infiltrates in the mucosa and submucosa and in the adjacent lymph node parenchyma. Remnants of lymphoid follicles visible in the cortex. Scale bar = 2000 μm; b – HE-stained lamina propria and submucosa of the large colon widely infiltrated by epithelioid macrophages and aggregates of lymphocytes and plasma cells; multinucleated giant cells with peripherally located nuclei (insert). Scale bar = 200 μm; c – HE-stained cross section through a mesenteric lymphatic vessel occluded by epithelioid macrophages, multinucleated giant cells and fewer lymphocytes and plasma cells. Scale bar = 500 μm; d – Ziehl–Neelsen-stained large colon with numerous macrophages in the lamina propria and submucosa containing intracellular acid-fast bacteria. Scale bar = 100 μm

Matrix-assisted laser desorption/ionisation–time-of-flight mass spectrometry (MALDI-TOF MS) results of Mycobacterium species identification in tissue samples from Polish horses with granulomatous enterocolitis

No.MALDI-TOF MS results
SpeciesPointsProbabilitySymbols/colour
Horse No. 1Mycobacterium avium subsp. hominissuis≥2,300Highly probable+++/green
Horse No. 2Mycobacterium avium subsp. hominissuis≥2,300Highly probable+++/green
Horse No. 3Mycobacterium avium subsp. hominissuis≥2,300Highly probable+++/green

Starter and probe sequences used in the reaction to screen equine tissue samples for Mycobacterium tuberculosis complex species

NameSequence 5′–3′
Starter F6110GGT AGC AGA CCT CAC CTA TGT GT
Starter R6110AGG CGT CGG TGA CAA AGG
Pr6110FAM-CAC GTA GGC GAA CCC-MGB NFQ

Components in the PCR reaction to screen equine tissue samples for Mycobacterium tuberculosis complex species

ReagentConcentrationVolume (μL)
Nuclease-free water-7.5
QuantiFast mix5×5
Assay internal control10×2.5
Internal control DNA10×2.5
F61105 pmol/μL1
R61105 pmol/μL1
Pr61105 pmol/μL0.5
DNA-5
Total volume25

The clinical data of horses suffering granulomatous enterocolitis and the results of laboratory investigations

Clinical and laboratory dataHorse No. 1Horse No. 2Horse No. 3
Age3 months10 months3 years
SexMaleMaleFemale
Duration of illness2 months7 months1.5 years
Symptoms:
Diarrhoea+++
Weight loss+++
Gastric ulcers+++
Serum biochemistry:
Hypoalbuminaemia- (10.7 g/L)- (12.1 g/L)- (9.8 g/L)
Parasitological findings after examination of faecal samples-Parascaris univalens, Cryptosporidium sp. and Giardia sp.-
Ultrasonographic findingsThickened intestinal wallHyperechoic mass in the lower left area (12-14 intercostal spaces), presence of free fluid in the abdominal cavity, thickened small intestinal wallFree fluid present in the abdominal cavity, thickened intestinal wall
DOI: https://doi.org/10.2478/jvetres-2025-0067 | Journal eISSN: 2450-8608
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Language: English
Submitted on: May 24, 2025
Accepted on: Dec 2, 2025
Published on: Dec 10, 2025
Published by: National Veterinary Research Institute in Pulawy
In partnership with: Paradigm Publishing Services
Publication frequency: 4 issues per year
Keywords:
abdominocentesis,
enterocolitis,
intractable equine diarrhoea,
MAH,
MALDI-TOF
Related subjects:
Life sciences,
Molecular biology,
Microbiology and virology,
Life sciences, other,
Medicine,
Veterinary medicine

© 2025 Beata Nowicka, Wojciech Łopuszyński, Monika Krajewska-Wędzina, Anna Biazik, Magdalena Sobuś, Izabela Polkowska, Ewelina Szacawa, published by National Veterinary Research Institute in Pulawy
This work is licensed under the Creative Commons Attribution 4.0 License.

AHEAD OF PRINT