Haycocknema perplexum n. g., n. sp. (Nematoda: Robertdollfusidae): an intramyofibre parasite in man

Abstract

Haycocknema perplexum n. g., n. sp. (Nematoda: Robertdollfusidae) is described from a man in Tasmania, Australia. Adult male and female nematodes and larvae were recovered from myofibres following biopsy of the right vastus lateralis muscle and were associated with a polymyositis. H. perplexum is distinguished from all other genera of the Muspiceoidea by the presence of a large amorphous "cell" supporting a granule-filled, flask- or gourd-shaped reservoir in the rectal region of mature and gravid female nematodes, often containing one or more large, refractile, thick-rimmed "globules" on the external surface of the reservoir, by the small number of ova/eggs/larvae developing in each uterus, by the minute, weakly-sclerotised, almost tubular spicule, by the presence of a pair of ampulla-shaped glands posteriorly and by the presence of lateral bacillary bands comprised of a single row of pore cells spaced irregularly and extending posteriorly to the region of the vulva in immature females.

More parasitic myositis cases in humans in Australia, and the definition of genetic markers for the causative agents as a basis for molecular diagnosis

“…(found in tree kangaroos) was recovered from the abdomen of the biting midge Culicoides victoriae. In addition, an undescribed Robertdollfusidae was found in the gut of the blackfly, Simulium damnosum, in Cameroon (Spratt et al, 1999). With these related nematodes in mind, it could be proposed that H. perplexum uses an arthropod as an intermediate host and has accidentally found its way into humans.…”

“…Although considered as rare, disease caused by H. perplexum in humans in Australia might be an occult or emerging issue, possibly affecting some people by subclinical infection/s in what presently appear to be two endemic foci (Queensland and Tasmania). The definition of nuclear and mitochondrial genetic markers for nematodes that we presently consider to represent H. perplexum (Spratt et al, 1999) now provides a sound basis for routine molecular diagnosis of parasitic myositis in human patients suffering from debilitating and progressive muscle wastage and associated complications, in combination with conventional clinical, biochemical and immunological tests. Moreover, the PCRbased sequencing approach established here would be a useful research tool to undertake surveys of potential reservoir animals or vectors for the occurrence of the present and related nematode genotypes in Australia or elsewhere, and to support studies of the biology and transmission of these/this enigmatic worm/s.…”

“…For instance, since 1998, there have been six human cases of disseminated myositis (inflammation of multiple muscle groups) in the States of Queensland and Tasmania of Australia (McKelvie et al, 2013), attributed to the nematode Haycocknema perplexum (Spratt et al, 1999). In these cases, clinical diagnosis was made on the basis of progressive muscle weakness, weight loss and/or dysphagia, complemented by the microscopic detection/identification of the nematode in muscle biopsies (Dennett et al, 1998;Spratt et al, 1999;Basuroy et al, 2008;McKelvie et al, 2013), elevated eosinophil and creatine kinase levels in blood and an exacerbation of clinical signs following anti-inflammatory (usually corticoid steroid) treatment against the myositis. Parasitological diagnosis from muscle biopsies has relied on the microscopic identification of the non-encysted, intra-fibrillar nematode, which is ~ 350 µm in length and 20 µm in width, and has a rounded cephalic end and a sharply tapered tail; female worms within the muscle are often gravid (Basuroy et al, 2008).…”

The systematics of the genus Trichinella with a key to species

“…Rarely, small intracellular nematodes other than Trichinella larvae may be found in the muscles of vertebrates including man (Andrews et al, 1997). An interesting example in man was described recently in Australia that apparently involved a dual infection with Trichinella (Andrews et al, 1997) and a new nematode (Haycocknema perplexum) of the family Robertdollfusidae (Spratt et al, 1999). Because nematodes other than these, such as Ancylostoma and Dracunculus, may rarely be found in myofibers, the morphological features and/or molecular identification of such larvae must be carefully determined (Spratt et al, 1999).…”

“…An interesting example in man was described recently in Australia that apparently involved a dual infection with Trichinella (Andrews et al, 1997) and a new nematode (Haycocknema perplexum) of the family Robertdollfusidae (Spratt et al, 1999). Because nematodes other than these, such as Ancylostoma and Dracunculus, may rarely be found in myofibers, the morphological features and/or molecular identification of such larvae must be carefully determined (Spratt et al, 1999). It should also be recognized that, under certain conditions, some reptiles can be rendered susceptible to Trichinella.…”