oligochaete worms , as the second largest group of the annelida , occur in a wide variety of freshwater environments . within this diverse group , limnodrilus hoffmeisteri claparde , 1862 ( oligochaeta : tubificinae ) , is one of the most common and abundant aquatic oligochaetes . like all other oligochaetes , the species is a hermaphrodite , with a complex reproductive system . typically , each body segment possesses 4 bundles of chaetae ( chitinous bristles projecting from the body ) . the chaetae , vary considerably in size and shape between families , and consequently are used extensively in identification . the life cycle of this species includes a stage that involves shedding of eggs into aquatic or moist environments with subsequent development into earthworms . these worms are capable of producing high population densities in paddy fields , eutrophic lakes , and rivers . thus , bathing , picnicking , or field working without protection measures may bring the potential risk of ingress . along with helminths and parasitic nematodes , occasional cases of non - parasitic worm infections ( caused by enchytraeus sp . however , aquatic oligochaete human infections have not been reported in china up till now . in this study , we are reporting a case of oligochaete nasal infection in a 25-year - old chinese man . after detailed microscopic examinations and molecular identification , the infected specimen was identified as l. hoffmeisteri . the infectious agent was eliminated and was no longer detectable in the patient s nasal cavities after treatment with zentel ( albendazole ) . these data will assist clinicians to be aware of this diagnosis and properly guide preventable measures to those who are in risk ( such as aquaculture farmers , fishery workers , and ornamental fish hobbyists ) . the patient was a 25-year - old male residing in zhangjiakou city , hebei province , china employed by a coalmine machinery factory . he initially presented with severe nasal itching , rhinorrhea , and continuous sneezing followed by a nose bleed 2 days prior to consultation . mucosal damage to kiesselbach s area ( on the antero - inferior part of the nasal septum ) , was diagnosed by nasal endoscopy . the worms extracted from the nasal discharge of the patient were identified by using morphological and molecular methods . the observed worm length was 1545 mm , and worm width was 0.60.8 mm ( fig . the prostomium of the observed worms was cone - shaped , and contained about 110 proglottids ( fig . long and thin bifid chaetae with a curved distal end were observed on the dorsal pre- and post - clitellar regions ( fig . the ratio of the length of the dorsal bifid chaetae to the ventral chaetae was approximately 1.15 . the penile sheath was long and tubular , and the length to width ratio ranged from 10.3 to 11.3 ( fig . the morphological characteristics of the species were consistent with a previously published description of l. hoffmeisteri . furthermore , genomic dna was extracted from individual worms using a genomic dna purification kit ( tiangen , china ) for amplification of the small subunit ribosomal rna ( rrna ) region ( fig . 2 ) . the sequences obtained showed 99% identity with l. hoffmeisteri ncbi genbank entries ( nos . a neighbor - joining ( nj ) tree constructed from ssu sequences grouped the worm isolated from the patient into the same cluster as l. hoffmeisteri ( fig . , the morphological characteristics and molecular data confirmed that the species isolated from the patient was l. hoffmeisteri . fortunately , the oligochaete worms were no longer detectable in the patient s nasal cavities following treatment with 400 mg zentel ( albendazole ) and yunnan baiyao ( also called yunnan paiyao , a hemostatic powdered medicine ) once daily for 6 days . l. hoffmeisteri is the best known and is considered to be the dominant species of the genus . although uncommon , the infection can occur in people after exposure to contaminated water . in the present study , for the first time we have reported the case of l. hoffmeisteri infection in the nasal cavity of a chinese man . as a result of this study , total 444 live red worms were isolated and examined from the nasal discharge of the patient by the first affiliated hospital of hebei north university . measurements of l. hoffmeisteri , including the body and penile sheath size , prostomium shape , and the ratio of the length of the dorsal bifid chaetae to the ventral chaetae , were performed . the specimens were identified as microdrile tubificid l. hoffmeisteri claparde , 1862 ( tubificidae ) and megadrile dichogastrid dichogaster bolaui michaelsen , 1891 ( octochaetidae ) , respectively . in our study , we demonstrated a case of human nasal infection with l. hoffmeisteri in china . the likely source of infection of the chinese patient was fish bait used by the patient to feed domestically maintained tropical fish . it is likely that finger - to - nose contact with the fish bait gave rise to the associated infection . a second potential infection source may be a local reservoir used by the patient for recreational purposes 6 months prior to the infection . such opportunistic infection by l. hoffmeisteri occurs more frequently in individuals who are exposed to aquatic environments through labor occupation or leisure activities , usually with skin or mucosal lesions , paresthesia or itching at the ingress site , as well as associated systemic manifestations . accurate identification of pathogenic agents of these opportunistic infections is critical for the proper selection of clinical complementary tests and detailed anamnesis . to summarize , this is the first report of nasal infection with l. hoffmeisteri in a human in china . this l. hoffmeisteri nasal infection can serve as a reminder that oligochaete worms can result in human infections . this also demonstrates that appropriate hygiene precautions are important during field working and leisure activities .