Disseminated alimentary mycobacteriosis in the horse: a retrospective study of nine cases

Abstract

Summary This paper summarises the clinical findings of 9 cases of disseminated alimentary mycobacteriosis in horses presented at a Finnish referral equine hospital 2009–2014. Four of 9 horses were Standardbreds and 8/9 horses were male. The median age was 2 years, ranging from 6 months to 15 years. The duration of clinical signs before admission ranged from 2 weeks to 6 months. All horses demonstrated deterioration of the clinical signs after a protracted period of the disease and were finally subjected to euthanasia after poor response to multiple medical therapies. The most common complaints on admission were weight loss and diarrhoea (9/9), pyrexia (7/9), ventral oedema (7/9), lethargy (7/9) and inappetance (6/9). The most common clinicopathological abnormalities were hypoalbuminaemia and hyperfibrinogenaemia, which were present in all horses. Rectal biopsy specimens were examined from 5/9 horses and specimens were stained with Ziehl‐Nielsen (ZN). At rectal biopsy, mild multifocal neutrophilic or mild granulomatous proctitis was recognised in all 5 horses, but the ZN stain for mycobacteria was positive in only one biopsy. A liver biopsy was taken from one horse in which hepatomegaly was observed clinically and revealed marked granulomatous hepatitis with the presence of mycobacteria. The rectal biopsy from this horse was ZN negative. At post mortem examination, chronic, multifocal to coalescing granulomatous typhlocolitis and lymphadenitis were found in all horses with the small intestine less frequently involved. At histopathological examination of post mortem samples, a ZN stain was performed and intracellular acid‐fast bacilli were identified in macrophages and multinucleated giant cells in the large intestine, liver and lymph nodes in 9/9 horses and in the small intestine in 5/9 horses. Mycobacterium avium ssp. hominissuis was isolated in 5/9 horses from post mortem samples.

Multisystemic bovine mycobacteriosis in a pony with neurological signs and weight loss

“…The mode of transmission of mycobacterial infections in horses is unclear (Mönki et al . ). An oral route of infection in equids is most likely (Pavlik et al .…”

Mycobacterial infections in equids: Clinical characteristics and diagnostic techniques

“…; Mönki et al . ). Mesenteric lymph nodes are likely to be enlarged on palpation per rectum and there may be a nodular profile to the spleen.…”

“…Detection of features such as thickening of the wall of the small or large intestine and mesenteric lymph node enlargement (Mönki et al . ) or granulomatous hepatic/splenic densities on ultrasound examination of the abdomen should increase the suspicion of mycobacterial involvement. Similarly, detection of multiple areas of pulmonary consolidation on thoracic ultrasound should increase the suspicion of pulmonary bTB or MAC involvement, and thoracic radiographs should be obtained.…”

Granulomatous Rhinitis in a Horse due to Mycobacterium intracellulare Infection

“…sylvaticum (Chiers et al, 2012) and M. avium subsp. hominissuis (Kriz et al, 2010;Mönki et al, 2016). Horses have a strong innate resistance to mycobacterial infections by the MTC (Mair, 1996), and this resistance presumably extends to the MAC as well.…”