bourgelatia diducta ralliet , henry and bauche , 1919 is a small - sized , milky white - colored nematode parasite with a well - developed mouth and bursa .
this nematode is a member of the subfamily oesophagostominae , family chabertiidae , and order strongylida .
the genus bourgelatia comprises a single species , b. diducta , which was first found in the cecum and colon of pigs in 1919 .
the species was formerly classified as phacochoerostrongylus schwartz , but later was reclassified into the genus bourgelatia by differences in the morphology of buccal capsule , ovejecter , vagina length , and dorsal ray . thus far , little is known about the pathogenesis and clinical symptoms of this parasite to its host , sus scrofa .
previous studies indicated that the infection of this worm is common among domestic pigs in india ( 21.6% ) , papua new guinea   and the solomon islands ( 13% ) .
although the parasite was found in a relatively high prevalence among wild boars in japan ( 95% ) , the parasite so far has not been reported in the republic of korea ( south korea ) .
it has been reported that korean domestic pigs are infected with oesophagostomum detatum only without b. diducta in some surveys performed by fecal examination [ 9 - 12 ] .
recently , the population of wild boars in south korea has gradually increased due to the absence of predators such as panthera tigris .
therefore , the growing number of wild boars has been creating serious problems for human residential life and local agriculture industry .
however , there has been little systematic approach to investigate the disease status among wild boars in south korea .
the purpose of this study , therefore , was to investigate parasitic diseases of wild boars in south korea . in this study
, we examined the gastrointestinal tract of 87 wild boars over a 4-year period in the southwestern part of south korea and found that b. diducta was quite prevalent among wild boars .
together with light and scanning electron microscopic evidences , we provided the identification key and measurements of various parts of the worm .
gastrointestinal tracts of 87 korean wild boars ( sus scrofa coreanus ) hunted in mountains of suncheon - si , gwangyang - si , and boseong - gun between 2009 and 2012 by members of local hunting associations were collected and examined for visceral helminths .
the gastrointestinal tract of each wild boar was removed from the body and brought to the laboratory to examine the presence of parasites .
the cecum and colon were slit open lengthwise and the mucosa and contents were examined carefully in a separate container .
worms were preserved in 70% ethanol , and were mounted on a slide glass using polyvinyl alcohol mounting medium .
measurements were made under a light microscope ( axioscop , zeiss , city , country ) on body dimensions , lengths of corona radiata , eosophagus , spicules , and gubernaculum , width of pharynx and other body parts of adult male and female worms .
species identification of the worm was based on the description by yamaguti   and lichtenfels .
scanning electron microscopy was used to identify b. diducta as previously described by yadav and tandon .
briefly , worms were washed 3 times with 0.85% pbs for 20 min , fixed in 2.5% glutaraldehyde in 0.1 m phosphate buffer ( ph 7.2 ) for 24 hr in a refrigerator at 4 and were post - fixed in 1% oso4 for 2 hr in a refrigerator at 4. after serial dehydration steps in 30 , 50 , 70 , 80 , 90 , and 100% ethanol for 20 min each , critical - point drying in a hitachi hcp-2 ( hitachi ltd , tokyo , japan ) and sputter - coating with gold - palladium in an emitech k550 ( emitech ltd , ashford , kent , england ) , digital photography of worms was taken using a hitachi s-2400 scanning electron microscope ( hitachi ltd , tokyo , japan ) .
gastrointestinal tracts of 87 korean wild boars ( sus scrofa coreanus ) hunted in mountains of suncheon - si , gwangyang - si , and boseong - gun between 2009 and 2012 by members of local hunting associations were collected and examined for visceral helminths .
the gastrointestinal tract of each wild boar was removed from the body and brought to the laboratory to examine the presence of parasites .
the cecum and colon were slit open lengthwise and the mucosa and contents were examined carefully in a separate container .
worms were preserved in 70% ethanol , and were mounted on a slide glass using polyvinyl alcohol mounting medium .
measurements were made under a light microscope ( axioscop , zeiss , city , country ) on body dimensions , lengths of corona radiata , eosophagus , spicules , and gubernaculum , width of pharynx and other body parts of adult male and female worms .
species identification of the worm was based on the description by yamaguti   and lichtenfels .
scanning electron microscopy was used to identify b. diducta as previously described by yadav and tandon .
briefly , worms were washed 3 times with 0.85% pbs for 20 min , fixed in 2.5% glutaraldehyde in 0.1 m phosphate buffer ( ph 7.2 ) for 24 hr in a refrigerator at 4 and were post - fixed in 1% oso4 for 2 hr in a refrigerator at 4. after serial dehydration steps in 30 , 50 , 70 , 80 , 90 , and 100% ethanol for 20 min each , critical - point drying in a hitachi hcp-2 ( hitachi ltd , tokyo , japan ) and sputter - coating with gold - palladium in an emitech k550 ( emitech ltd , ashford , kent , england ) , digital photography of worms was taken using a hitachi s-2400 scanning electron microscope ( hitachi ltd , tokyo , japan ) .
the average length of adult females was 11.30.87 mm , and the thickest part of the body measured 0.540.04 mm in maximum width , while those of males were 9.80.72 and 0.450.03 mm , respectively .
. 1 g , h ) , and males had the type ii dorsal ray with 2 rami ( fig .
the buccal capsule was small , relatively thin - walled , cylindrical , very short , and ring - shaped ( fig .
2c ) , the cervical groove that can be recognized in the genus oesophagostomum was absent ( fig .
the ovijector in the inside of the posterior extremity of females consisted of 3 parts as a thick - walled vestibule that connected to the vagina , a paired thick - walled sphincters and a thinner - walled infundibula which was connected to the uteri ( fig .
the anterior extremity was equipped with 20 - 22 external corona radiata , a well - developed leaf - crown structure surrounding the mouth , 4 cephalic papillae and 2 lateral amphids around the mouth ( fig .
there was an oral collar which was much deeper than transverse ridges of the body cuticle , and an excretory pore and a pair of cervical papillae were also present ( fig .
the vulva was shown as a prominent circular protrusion with a semicircular opening while the anus was shown as a rather flat semicircular hole ( fig .
the tapering tail bore a pair of minute caudal papillae and a spike ( fig .
the posterior extremity of males had a well - developed bursa that consist of a long dorsal and 2 slightly shorter lateral lobes ( fig .
there were 2 conspicuous protrusions at the end of externodorsal and anterolateral rays on its surface ( fig .
the genital cone was observed at the point of the spicules flowing in and out ( fig .
3f ) . from 87 korean wild boars captured in the southwestern area of south korea , 47 ( 54.0% )
were found to harbour b. diducta in the large intestine , mainly in the cecum .
the worm was found in 5 of 13 wild boars ( 38.5% ) from suncheon - si , 38 of 70 ( 54.3 ) from gwangyang - si , and all 4 ( 100% ) from boseong - gun .
no differences between the gender were recognized on the rate of infection ( table 1 ) .
a total of 938 worms ( 551 males and 387 females ) of b. diducta was collected from the cecum and colon with an average number of 20.0 per animal and the infection intensity being the highest in animals from boseong - gun .
the number of female worms present was 1.3 times more prevalent than the number of male worms ( table 2 ) .
from 87 korean wild boars captured from mountains of the suncheon - si , gwangyang - si and boseong - gun , south korea spanning 2009 to 2012 , the infection of b. diducta , with an average number of 20 worms per animal was confirmed in 47 ( 54% ) wild boars . although this is the first report in south korea ,
for instance , the prevalence of b. diducta in wild boars or domestic pigs reported from japan , india , and the solomon islands   was 95% , 21.6% , and 13.0% , respectively .
these reports suggest that the parasite may be distributed over a rather wide area ranging from asia and oceania . up to now , however , there have been few reports on the intensity and pathogenesis of the infection with the parasite among pigs in the rest of the world .
although we carefully observed the large intestine , pathologic changes in the mucosa was hardly recognized . in the infection with oesophagostomum detatum which belongs to the same subfamily oesophagostominae as bourgelatia , infective larvae exsheath in the small intestine and enter the mucosa of the large intestine causing small nodules .
although the parasite is normally regarded as being only mildly pathogenic to pigs , the intestinal walls become edematous and strongly hyperemic in heavy burdens to develop into necrotic enteritis . as observed during the autopsy in this study , the infection of b. diducta did not elicit pathologic lesions in pigs at the population density of 20 worms per animal .
there is a possibility that pathologic changes in the mucosa were not recognized due to the relatively low worm burden . also , it is possible that the worm is relatively non - pathogenic in wild boars .
the infection of domestic pigs with the genus oesophagostomum spp . has been frequently reported in south korea and the prevalences of o. dentatum among domestic pigs based on fecal examination of eggs were 10.5% , 14.8% , 6.4% , and 2.5% .
however , eggs of the genus oesophagostomum and bourgelatia are indistinguishable by size and appearance , and therefore it is possible that previous surveys based on fecal examination might have made mistakes stemming from correct identification of the genus .
similarly , the prevalence of b. diducta ( 17% ) previously reported in pigs from nigeria   by fecal examination might not be based on correct identification .
therefore , the infection status of o. dentatum among domestic pigs in korea requires identification of adult worms for a correct faunistic record in korea .
previous studies on the morphological features of b. diducta are remarkably consistent with those of our present study .
the measurements of the worm body in this study were practically identical with the report by yamaguti   ( table 4 ) .
studies on sem structures by yadav   on external corona radiata , oral collar , cephalic papilla , lateral amphid , bursa , genital cone , externodorsal and anterolateral rays , vulva , anus , and caudal papillae match structurally up with our findings .
in other members of the subfamily oesophagostominae in pigs , morphological structures are varied in shape and size .
the cervical groove is present in daubneyia leroux , 1940 and oesophagostomum molin , 1861 while the buccal capsule of phacochoerostrongylus schwartz , 1928 is twice as wide as deep .
the bourgelatioides traguli differs from b. diducta in lacking the anterior leaf - crown and in other details of the mouth capsule , in the presence of a groove and overlying flaps in the cervical region , and in the presence of terminal convoluted filaments on the spicules .
we provided some identification key aspects regarding the morphological features of the superfamily strongyloidea and the genus bourgelatia ( fig .
the identification keys in this article are adapted from lichtenfels . conclusively , in the present study , b. diducta ( nematoda : chabertiidae ) is recorded for the first time in south korea . in addition , morphological characteristics and differential keys provided in the present study will be helpful in the faunistic and taxonomic studies of strongylid nematodes related .
 this study describes the first record of bourgelatia diducta ( nematoda : chabertiidae ) from wild boars in the republic of korea ( = south korea ) . 
 gastrointestinal tracts of 87 korean wild boars ( sus scrofa coreanus ) hunted in mountains in the south - western part of south korea between 2009 and 2012 were examined for their visceral helminths . 
 b. diducta , as identified by morphological characteristics of the head and tail , were recovered from the large intestine of 47 ( 54% ) wild boars . 
 the average length of adult female worms was 11.30.87 mm and the thickest part of the body measured 0.540.04 mm in maximum width , while those of males were 9.80.72 and 0.450.03 mm , respectively . 
 the characteristic j - shaped type ii ovejector was observed in females , and the type ii dorsal ray with 2 rami on each side of the median fissure was uniquely seen in males . 
 the buccal capsule was small , relatively thin - walled , cylindrical , very short , and ring - shaped . 
 the externodorsal ray arose from a common stem with the dorsal ray . 
 the cervical groove was absent . 
 the anterior extremity was equipped with 20 - 22 external corona radiata , 4 cephalic papillae and 2 lateral amphids around the mouth . 
 the eggs were 66.038.9 m in average size . by the present study , b. diducta ( nematoda : chabertiidae ) 
 is recorded for the first time in south korea . additionally , 
 morphological characteristics and identification keys provided in the present study will be helpful in the faunistic or taxonomic studies for strongylid nematodes related . 