Anncaliia algerae microsporidial myositis

Emerg Infect Dis. 2014 Feb;20(2):185-91. doi: 10.3201/eid2002.131126.


The insect microsporidian Anncaliia algerae was first described in 2004 as a cause of fatal myositis in an immunosuppressed person from Pennsylvania, USA. Two cases were subsequently reported, and we detail 2 additional cases, including the only nonfatal case. We reviewed all 5 case histories with respect to clinical characteristics, diagnosis, and management and summarized organism life cycle and epidemiology. Before infection, all case-patients were using immunosuppressive medications for rheumatoid arthritis or solid-organ transplantation. Four of the 5 case-patients were from Australia. All diagnoses were confirmed by skeletal muscle biopsy; however, peripheral nerves and other tissues may be infected. The surviving patient received albendazole and had a reduction of immunosuppressive medications and measures to prevent complications. Although insects are the natural hosts for A. algerae, human contact with water contaminated by spores may be a mode of transmission. A. algerae has emerged as a cause of myositis, particularly in coastal Australia.

Keywords: Anncaliia algerae; Australia; arthritis rheumatoid; infection; insects; microporidia; myositis; solid-organ transplantation.

Publication types

  • Case Reports

MeSH terms

  • Aged
  • Apansporoblastina / pathogenicity
  • Apansporoblastina / physiology*
  • Arthritis, Rheumatoid / drug therapy
  • Arthritis, Rheumatoid / immunology*
  • Australia
  • Fatal Outcome
  • Humans
  • Immunocompromised Host*
  • Immunosuppressive Agents / adverse effects
  • Life Cycle Stages
  • Male
  • Microsporidiosis / drug therapy
  • Microsporidiosis / microbiology
  • Microsporidiosis / pathology*
  • Muscle, Skeletal / microbiology
  • Muscle, Skeletal / pathology*
  • Myositis / drug therapy
  • Myositis / microbiology
  • Myositis / pathology*
  • Organ Transplantation


  • Immunosuppressive Agents