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 .
 the infection by limnodrilus hoffmeisteri claparde , 1862 ( oligochaeta : tubificinae ) in humans is relatively uncommon . 
 the present report is to describe an incidental human infection with oligochaetes in the nasal cavity of a chinese man , a 25-year - old man residing in zhangjiakou city , hebei province , china presenting with nose bleed , severe itching , continuous sneezing , and rhinorrhea . 
 a lot of oligochaete worms were found in the nasal discharge of the patient . 
 the detected worms were identified as limnodrilus hoffmeisteri ( annelida : oligochaeta ) based on morphological and molecular characteristics . 
 this incidental l. hoffmeisteri nasal infection is the first case in china and indicates that oligochaete worms can be encountered in humans . 
INTRODUCTION
CASE RECORD
DISCUSSION