Using PCR-Based Sequencing to DiagnoseHaycocknema perplexumInfection in Human Myositis Case, Australia

Abstract

We report a case of myositis in a male patient in Australia who had progressive weakness and wasting in his left lower limb. Although clinical, pathologic, and laboratory assessments were inconclusive, a new, nested PCR–coupled sequencing method enabled the unequivocal diagnosis of myositis caused by the enigmatic nematode Haycocknema perplexum.

Imported Haycocknema perplexum Infection, United States1

“…A PCR was developed that enabled diagnosis of the 10th case of H. perplexum nematode infection from a muscle biopsy in the absence of visible nematodes (2,8). This PCR was unsuccessful when performed for our case-patient.…”

“…H aycocknema perplexum is an enigmatic nematode that is a rare cause of human parasitic myositis (1)(2)(3)(4). Twelve cases have been reported since its initial description in 1998, all in humans (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). The mode of transmission is unclear, but 9 patients reported contact with native wildlife in Tasmania or tropical regions of Queensland, Australia.…”

Global Medicine, Parasites, and Tasmania

“…Subsequent cases diagnosed had all lived in or visited Tasmania. Many had histories of contact with native animals or eating bush meat and it was thought that the infection was an endemic zoonosis from Tasmania [55,56]. A subsequent case from tropical North Queensland had no contact with Tasmania and a re-evaluation of all the recorded cases showed that they all had contact with the tropical north of Australia.…”

“…The result that the condition was considered to be endemic there and being redescribed the disease as "tropical parasitic myositis" [57]. However, the most recently reported case from Tasmania had no travel history, except to Melbourne in southern Victoria [56], confirming that H. perplexum is indeed endemic to Tasmania. The natural reservoir of H. perplexum has not been found to date and the mode of transmission to humans is also unknown.…”

“…While most infections in Australia have been controlled it has led to over-confidence regarding their importance (or even existence) today. Unfortunately, while ubiquitous protozoan species have been reported in wildlife across Australia [51][52][53][54][55][56][57][58][59][60][61] the life cycles, ecology, and general biology of most parasites of wildlife in Australia are poorly understood. Much of the work to date has been opportunistic with unreliable funding opportunities, but with modern methods and 'omic' technology [62] offering an avenue for major advances in the field, there is potential for renewed support and interest.…”