[Enterobius gregorii (Oxyuridae, Nematoda), a new human parasite]

Mitochondrial cytochrome c oxidase subunit 1 gene and nuclear rDNA regions of Enterobius vermicularis parasitic in captive chimpanzees with special reference to its relationship with pinworms in humans

Sequences of mitochondrial cytochrome c oxidase subunit 1 (CO1) gene, nuclear internal transcribed spacer 2 (ITS2) region of ribosomal DNA (rDNA), and 5S rDNA of Enterobius vermicularis from captive chimpanzees in five zoos/institutions in Japan were analyzed and compared with those of pinworm eggs from humans in Japan. Three major types of variants appearing in both CO1 and ITS2 sequences, but showing no apparent connection, were observed among materials collected from the chimpanzees. Each one of them was also observed in pinworms in humans. Sequences of 5S rDNA were identical in the materials from chimpanzees and humans. Phylogenetic analysis of CO1 gene revealed three clusters with high bootstrap value, suggesting considerable divergence, presumably correlated with human evolution, has occurred in the human pinworms. The synonymy of E. gregorii with E. vermicularis is supported by the molecular evidence.

Growth of Enterobius vermicularis in a chimpanzee after anthelmintic treatment

The growth of Enterobius vermicularis in a chimpanzee was investigated by observing worms discharged in feces after administration of pyrantel pamoate. Just after the final molting, immature adult male pinworms developed to a fully mature stage in 2 wk, after passing through a stage corresponding to the so-called Enterobius gregorii, which was surmised to be a younger adult form of E. vermicularis. The frequency distribution of body length forms 2 peaks in both male and female pinworms, with a depression in the transitional forms from the immature to the fully mature stage. This depression seems to be the result of more rapid growth or lower susceptibility to the drug in this transitional stage. Pyrantel pamoate effectively eradicated mature males, but gravid females were continuously observed in the feces after treatment. The complete eradication of pinworm infection by pyrantel pamoate could be achieved by repeated treatment at intervals shorter than 2 wk. This treatment would eradicate male worms first, resulting in females producing only unfertilized eggs, from which only males might hatch.

Phylogeny, host-parasite relationship and zoogeography

Phylogeny is the evolutionary history of a group or the lineage of organisms and is reconstructed based on morphological, molecular and other characteristics. The genealogical relationship of a group of taxa is often expressed as a phylogenetic tree. The difficulty in categorizing the phylogeny is mainly due to the existence of frequent homoplasies that deceive observers. At the present time, cladistic analysis is believed to be one of the most effective methods of reconstructing a phylogenetic tree. Excellent computer program software for phylogenetic analysis is available. As an example, cladistic analysis was applied for nematode genera of the family Acuariidae, and the phylogenetic tree formed was compared with the system used currently. Nematodes in the genera Nippostrongylus and Heligmonoides were also analyzed, and the validity of the reconstructed phylogenetic trees was observed from a zoogeographical point of view. Some of the theories of parasite evolution were briefly reviewed as well. Coevolution of parasites and humans was discussed with special reference to the evolutionary relationship between Enterobius and primates.

The Enterobiinae subfam. Nov. (Nematoda, Oxyurida) pinworm parasites of primates and rodents

Recent redescriptions of most members of the Oxyuridae Cobbold, 1864 parasitic in primates revealed that they share following derived characters: sexual dimorphism of lateral alae (single-crested in the males, double-crested in the females); in males a second pair of genital papillae always surrounded by strongly cuticularized rings; in females, uterine tube divided into 2 parts by a cellular wall forming a diaphragm. These characters are interpreted as synapomorphies, providing evidence that these taxa represent a monophyletic group, and we propose to classify them in a new subfamily of the Oxyuridae: the Enterobiinae subfam.nov. The Enterobiinae as recognized herein occurs in both Old World and New World Primates and rodents of the family Sciuridae (tribe Sciurini in the Holarctic region and tribe Xerini in the Ethiopian region). The new subfamily includes the following genera: Enterobius Leach, 1853; Colobenterobius Quentin, Betterton & Krishnasamy, 1979; Rodentoxyuris Quentin & Tenora 1974; Xeroxyuris Hugot, 1995; Lemuricola Chabaud & Petter, 1959; Protenterobius Inglis, 1961; Madoxyuris Chabaud, Brygoo & Petter, 1965; Trypanoxyuris Vevers, 1923; Hapaloxyuris Inglis & Cosgrove, 1965 and Paraoxyuronema Artigas, 1936. The genus Paraoxyuronema is revalidated as a subgenus of Trypanoxyuris due to its specialized buccal structures. This genus groups all pinworm nematodes specific for primates of the family Atelidae, including: P. brachytelesi Artigas, 1937 occurring in Brachyteles arachnoides; P. atelis (Cameron, 1929) occurring in Ateles spp., and P. duplicidens (Buckley, 1931) and P. lagothricis (Buckley, 1931), which are parasites of Lagothrix spp. Inglisoxyuris inglisi Chabaud, Petter & Golvan, 1961, included in the monospecific genus Inglisoxyuris and previously classified as a subgenus of the Lemuricola, does not share the characters of the new subfamily and, until its precise classification can be considered with more information, it is proposed to refer to this species as an Oxyuridae sensu lato. A diagnosis and a key of the genera included in the new subfamily are given.

[Enterobius gregorii Hugot, 1983 recovered from school children in Kangwon-Do, Korea]

Hugot (1983), Hugot and Tourte-Schaefer (1985) reported that nematodes of the genus Enterobius causing human enterobiasis might be classified into two different species on the basis of the size and shape of spicule in male worms. E. gregorii Hugot, 1983 has significantly shorter spicules in males than those in E. vermicularis. A total of 194 male Enterobius were collected from 17 schoolchildren by anthelmintics at Wonju, Kangwon-do. The sizes of spicules and morphologies were comparatively observed. Two different types of spicules in male Enterobius were also observed in Korea. Out of 112 male worms observed, the percentages of E. gregorii (short-spicule type) and E. vermicularis (long-spicule type) were 23.2% and 76.8%, respectively.

Enterobius vermicularis infection in a children's ward

Following the discovery that two patients on a children's orthopaedic ward were excreting Enterobius, all patients and staff on the ward were screened for the presence of pinworms. None of the staff was infected but 11 (55%) of 20 patients either had Enterobius ova on the anal margin or excreted worms following piperazine treatment. Epidemiological investigations indicated that this was unlikely to be a ward outbreak because four of the infected children had been on the ward for under 3 days, i.e., less than the prepatent period for Enterobius. Although none of the children was symptomatic, all children and staff on the ward were treated with piperazine. Faecal samples were collected from nine children and the majority of their worm load was shed within 32 h of starting therapy. Microscopic examination of the adult male worms showed that each patient was excreting both Enterobius vermicularis and E. gregorii.