Hymenolepis diminuta, phylogenetic analyses of nuclear rRNA + ITS and mitochondrial cox1 and its infections in non-human primates

Hymenolepis diminuta is a tapeworm commonly found worldwide in small rodents such as rats with occasional reports in other definitive hosts such as primates including chimpanzees and humans. It has not been reported in African green monkey (AGM, Chlorocebus sabaeus), and the parasite's molecular phenotype and phylogeny remain primitively sketchy. The aims of the current study were to determine if H. diminuta infected AGMs, to molecularly characterize H. diminuta and to review its infection in non-human primates. Feces of AGMs were examined visually for adult helminths and microscopically for eggs using centrifugation flotation. Total DNA extracted from eggs was amplified by PCR followed by DNA sequencing of targeted sequences of nuclear rRNA + internal transcribed spacers (ITS) and mitochondrial cox1. Phylogenetic analyses were performed. The DNA sequences of both nuclear rRNA + ITS and mitochondrial cox1 showed more than 98% and 99% identity to the known sequences respectively. Hymenolepis diminuta has been reported in various non-human primates with the highest prevalence of 38.5% in the white-headed capuchin monkey. The study presented here confirms that this tapeworm is capable of infecting various species of non-human primates with the first report of infections in AGM. Phylogenetic analyses of rRNA + ITS and mitochondrial cox1 demonstrated three separated clades I, II and III with the newly described AGM1 isolate belonging to the clade I. Whether these differences are at species level remains to be confirmed.

Worldwide overview of human infections with Hymenolepis diminuta

Hymenolepis diminuta is a zoonotic cestode parasitizing the small intestine of rodents (definitive hosts). Humans can accidentally enter into the life cycle of this tapeworm via the ingestion of infected insects (intermediate hosts) containing cestode cysticercoids in their body cavity. More than two centuries after the first record in humans, there are no accurate estimates of the number of human cases around the world. In order to have a more precise idea about the number of human cases with H. diminuta and the current status of the disease (hymenolepiasis) worldwide, we conducted a literature review of published records on human infection with H. diminuta. One thousand five hundred and sixty-one published records of infection with H. diminuta from 80 countries were identified. This review presents an estimate of the number of human cases with H. diminuta and a current overview of the prevalence, geographic distribution, symptoms, diagnosis, exposure to infective stages, and therapeutic approaches for this underestimated zoonotic tapeworm.

Hymenolepis diminuta Infection in a School Going Child: First Case Report from Uttarakhand

Hymenolepis diminuta (H.diminuta) is prevalent worldwide, and a few hundred human cases have been reported till date. It is primarily a rodent parasite and humans (usually children) can act as accidental hosts. Infections are usually asymptomatic but abdominal pain, irritability, pruritis, mild diarrhoea and eosinophilia are among the existing symptoms in a few of the reported cases. Here, we report a case of an 11-year-old female child from Bijnor, who presented to us with complaints of abdominal pain, fatigue and irregular episodes of fever. Routine stool examination showed characteristic eggs of H.diminuta. Patient was given a single oral dose of praziquantel (25 mg/kg) and she improved. This case is presented to emphasize that till date there are very few reports on H.diminuta and there is limited data regarding its treatment protocols (dose and duration). Furthermore, albendazole which is commonly used drug for deworming helminthic infections is less effective in these infections.