Mycobacterium avium subsp. hominissuis infection in horses.
Article Type: Letter to the editor
Subject: Mycobacterial infections (Risk factors)
Mycobacterial infections (Diagnosis)
Mycobacterial infections (Care and treatment)
Mycobacterial infections (Research)
Polymerase chain reaction (Usage)
Horses (Diseases)
Horses (Risk factors)
Horses (Diagnosis)
Horses (Care and treatment)
Horses (Research)
Authors: Kriz, Petr
Jahn, Petr
Bezdekova, Barbora
Blahutkova, Mariana
Mrlik, Vojtech
Slana, Iva
Pavlik, Ivo
Pub Date: 08/01/2010
Publication: Name: Emerging Infectious Diseases Publisher: U.S. National Center for Infectious Diseases Audience: Academic; Professional Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2010 U.S. National Center for Infectious Diseases ISSN: 1080-6040
Issue: Date: August, 2010 Source Volume: 16 Source Issue: 8
Topic: Event Code: 310 Science & research
Geographic: Geographic Scope: United States Geographic Code: 1USA United States
Accession Number: 237533376
Full Text: To the Editor: Mycobacterium avium subsp. hominissuis infection is often detected in pigs and humans (1-3). In most cases, the main sources of this agent are environmental (4,5). During the past few years, 2 hosts infected by this agent, dogs (6) and pet parrots (7), were identified as a possible source of infection for immunocompromised humans who may have close contact with animals. We report massive M. avium subsp. hominissuis infection in 2 sibling riding-type Fjord horses from an amateur-run horsebreeding farm.

The first horse, a 2-year-old colt, was admitted to a veterinary clinic in the Czech Republic in February 2009 with diarrhea and progressive weight loss of 3 weeks' duration. Multiple diagnostic procedures produced inconclusive results. Cyathostomosis was suspected, so moxidectin was administered twice, and prednisolone was given for 10 consecutive days. The clinical status of the horse initially improved but worsened after 3 weeks. Ultrasonographic examination of the peritoneal cavity showed a nodular mass and a nonperistaltic, thickened portion of the small intestine wall in the left ventrocranial region. Exploratory celiotomy showed enlargement of the mesenteric and colonic lymph nodes and multiple local thickenings of the small intestine wall, large colon, and cecum. The horse was euthanized. Specimens of enlarged lymph nodes and intestinal content were taken during necropsy for histopathologic and microbiologic examination. Microscopically, acid-fast rods (AFR) after Ziehl-Neelsen staining were observed, and quantitative real-time PCR (qPCR) showed 2.89 x 105 and 1.47 x 104 M. avium subsp. hominissuis cells per 1 g of intestinal content and mesenteric lymph node, respectively (8).

The second case, a 1-year-old full sister to the colt described above, was admitted in July 2009 after 1 month of lethargy, weight loss, diarrhea, and nasal discharge. Ultrasonographic examination of the abdominal cavity showed an increased amount of peritoneal fluid and nonperistaltic, corrugated, and thickened parts of the small intestine in the left caudal region. Local thickening of the jejunum and ileum were found during exploratory celiotomy; no lesions on the cecum or colon were observed macroscopically. Mesenteric lymph nodes were enlarged. Microscopically, AFR were observed, and qPCR showed 3.36 x 106 M. avium subsp. hominissuis cells per 1 g of mesenteric lymph node (8). Treatment with clarithromycin and rifampin was begun, but the condition of the filly improved only temporarily. She was euthanized after 4 months because of progressively worsening condition. Postmortem examination showed enlarged colonic lymph nodes with small nodular lesions, hyperemia of the colon mucosa, and corrugation and thickening of the colonic wall. For further examination, samples of feces, colonic lymph nodes and wall, liver, mesenteric lymph nodes, kidney, spleen, and diaphragm were taken. Ziehl-Neelsen staining of tissue smears demonstrated AFR in different tissues. Culture examination following the described method (2) and qPCR confirmed M. avium subsp. hominissuis infection; quantities of this agent were 6.31 x [10.sup.5] and 2.47 x [10.sup.11] in 1 g of feces and mesenteric lymph nodes, respectively (Table).

According to a review (9), infections caused by M. avium subsp. hominissuis have been described in only 6 horses until now. We presume that M. avium subsp. hominissuis infection in both these horses could have been caused by some immunodeficiency related to a genetic predisposition. The shedding of this agent in feces indicates that infected horses can also pose a health risk to humans, particularly immunocompromised persons. M. avium subsp. hominissuis infection is frequently observed in children, in whom it can cause peripheral lymphadenopathy (10). Currently, hippotherapy is a frequently used recreational activity in some countries for various patients, e.g., for children with cerebral palsy. Hippotherapy thus may be associated with a potential risk for humans in contact with clinically ill M. avium subsp. hominissuis-infected horses.


Petr Fictum, Misa Skoric, Radovan Kabes, Lucie Ottova, Radka Jaksova, Libuse Ocenaskova, and Zdenka Gregorova are appreciated for their skillful assistance.

The study was supported by grants MZE0002716202 from the Ministry of Agriculture of the Czech Republic, QH91240 of the National Agency for Agriculture Research and "AdmireVet," and CZ1.05/2.100/01.0006-ED0006/01/01 from the Ministry of Education, Youth and Sports of the Czech Republic.


(1.) Mijs W, de Haas P, Rossau R, van der Laan T, Rigouts L, Portaels F, et al. Molecular evidence to support a proposal to reserve the designation Mycobacterium avium subsp. avium to bird-type isolates and M. avium subsp. hominissuis for the human/porcine type of M. avium. Int J Syst Evol Microbiol. 2002;52:1505-18. DOI: 10.1099/ijs.0.02037-0

(2.) Matlova L, Dvorska L, Ayele WY, Bartos M, Amemori T, Pavlik I. Distribution of Mycobacterium avium complex isolates in tissue samples of pigs fed peat naturally contaminated with mycobacteria as a supplement. J Clin Microbiol. 2005;43:1261-8. DOI: 10.1128/JCM.43.3.1261-1268.2005

(3.) Pavlik I, Matlova L, Dvorska L, Shitaye JE, Parmova I. Mycobacterial infections in cattle and pigs caused by Mycobacterium avium complex members and atypical mycobacteria in the Czech Republic during 2000-2004. Vet Med Czech. 2005;50:281-90.

(4.) Pavlik I, Svastova P, Bartl J, Dvorska L, Rychlik I. Relationship between IS901 in the Mycobacterium avium complex strains isolated from birds, animals, humans and environment and virulence for poultry. Clin Diagn Lab Immunol. 2000;7:212-7.

(5.) Kazda J, Pavlik I, Falkinham J, Hruska K, eds. The ecology of mycobacteria: impact on animal's and human's health. New York: Springer; 2009.

(6.) Haist V, Seehusen F, Moser I, Hotzel H, Deschl U, Baumgartner W, et al. Mycobacterium avium subsp. hominissuis infection in 2 pet dogs, Germany. Emerg Infect Dis. 2008;14:988-90. DOI: 10.3201/eid1406.071463

(7.) Shitaye EJ, Grymova V, Grym M, Halouzka R, Horvathova A, Moravkova M, et al. Mycobacterium avium subsp. hominissuis infection in a pet parrot. Emerg Infect Dis. 2009;15:617-9. DOI: 10.3201/eid1504.081003

(8.) Slana I, Kaevska M, Kralik P, Horvathova A, Pavlik I. Distribution of Mycobacterium avium subsp. avium and M. a. hominissuis in artificially infected pigs studied by culture and IS901 and IS1245 quantitative real time PCR. Vet Micro. 2010;20:[Epub ahead of print].

(9.) Pavlik I, Jahn P, Dvorska L, Bartos M, Novotny L, Halouzka R. Mycobacterial infections in horses: a review of the literature. Vet Med Czech. 2004;49:427-40

(10.) Bruijnesteijn van Coppenraet LE, de Haas PE, Lindeboom JA, Kuijper EJ, van Soolingen D. Lymphadenitis in children is caused by Mycobacterium avium hominissuis and not related to 'bird tuberculosis.' Eur J Clin Microbiol Infect Dis. 2008;27:293-9. DOI: 10.1007/s10096007-0440-z

Petr Kriz, Petr Jahn, Barbora Bezdekova, Mariana Blahutkova, Vojtech Mrlik, Iva Slana, and Ivo Pavlik

Author affiliations: Veterinary Research Institute, Brno, Czech Republic (P. Kriz, M. Blahutkova, V. Mrlik, I. Slana, I. Pavlik); and University of Veterinary and Pharmaceutical Sciences, Brno (P. Jahn, B. Bezdekova)

Address for correspondence: Ivo Pavlik, Veterinary Research Institute, Hudcova 70, 621 00 Brno, Czech Republic; email:

DOI: 10.3201/eid1608.100097
Table. Detection of Mycobacterium avium subsp. hominissuis in
tissues of a 1-year-old Fjord filly *

                                  Mycobacteria detection

Sample source                     Microscopy   Culture

Feces                             -            +
Lymph node of transversal colon   +            +
Lymph node of descending colon    +            +
Transversal colon wall            +            +
Descending colon wall             +            +
Liver                             -            +
Mesenteric lymph node             +++          +
Kidney                            -            +
Spleen                            -            +
Diaphragm                         -            -


Sample source                     IS1245 ([dagger])    IS901

Feces                             6.31 x [10.sup.5]    -
Lymph node of transversal colon   1.84 x [10.sup.9]    -
Lymph node of descending colon    5.89 x [10.sup.9]    -
Transversal colon wall            3.98 x [10.sup.7]    -
Descending colon wall             6.33 x [10.sup.6]    -
Liver                             NT                   NT
Mesenteric lymph node             2.47 x [10.sup.11]   -
Kidney                            NT                   NT
Spleen                            NT                   NT
Diaphragm                         8.22 x [10.sup.4]    -

* qPCR, quantitative real-time PCR;  , negative finding;
+, few acid-fast rods; NT, not tested; +++, >100 AFR (per
50 microscopic fields).

([dagger]) No. IS1245 copies/g.
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