The Acanthocephalins’ Group of Helminths

The acanthocephalins’ helminths are commonly known as thorny-headed worms (or also spiny-headed worms) and are though to be an intermediate form between cestodes and nematodes. They are present in almost all parts of the world. However, human infections with this type of helminths, called acanthocephaliasis, are considered to be quite rare. Actually, human does not seem to be a natural host for acanthocephalins species and some animal species are usually considered as the final host. As such, acanthocephalins can very occasionally infect people who ingest infected animals. Humans are then considered as accidental hosts for this type of helminths. To date, only eight different thorny-headed worms species have been found in isolates from human.

Although quite rare, the parasite Moniliformis moniliformis is the most common species of acanthocephalins related to human infections. Cases have been reported in Nigeria, Iran, Iraq and the United States. Clinical manifestations of the disease include usually severe gastrointestinal symptoms because of the progressive destruction of the intestinal wall by the worm. However, asymptomatic cases have been reported in the literature. The reason why this infection is quite rare in human is because it is exclusively transmitted by the ingestion of intermediate hosts such as beetles and cockroaches. Children and people living in poor hygiene conditions facilitating the entry of beetles and cockroaches in the kitchen where they can contaminate food are more at risk to be infected by this parasite.

Other thorny-headed worms, such as Macracanthorhynchus hirudinaceous and Bolbosoma species, are also able to infect humans as accidental hosts. These infections occur almost exclusively in areas where insects are ingested as food or as medicines.

Diagnosis of infection with thorny-headed worms is made through the visualisation of parasite’s eggs in the faeces. Adult worms are not often visualised in the faeces, as they are not usually able to mature correctly in an accidental host. However, differential diagnosis could be delay by the fact that this type of infection is very rare. Anti-helminthics seem to work against thorny-headed worms, but the efficacy of this treatment is somewhat debates because of the very low number of patients treated so far.

Source: Centers for Disease Control and Prevention

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