Disseminated Mycobacterium avium infection in a dog with chronic diarrhoea

A 3-year-old Maltese-cross dog presented with a 4-month history of chronic diarrhoea and inappetence. Poorly regenerative anaemia, leukocytosis and hy poproteinaemia were evident on several occasions. Biopsies of stomach, duod enum and colon revealed marked infiltration of mucosae by macrophages conta ining many acid-fast bacilli. Similar organisms were numerous in a faecal s mear. Melaena, haematochezia and severe abdominal pain developed and were u nresponsive to therapy. Following euthanasia and necropsy, histiocytic cell s containing acid-fast bacilli were found throughout the gastrointestinal t ract, mesenteric and peri-pheral lymph nodes, spleen, liver, kidney and lun gs. The organism was identified as Mycobacterium avium by bacterial culture and polymerase chain reaction testing.