Seoi Infection Research Articles

STAT6 Expression and IL-13 Production in Association with Goblet Cell Hyperplasia and Worm Expulsion of Gymnophalloides seoi from C57BL/6 Mice

In intestinal helminth infections, Th2 immune respones are generally associated with mucin secretion for worm expulsion from the host intestine. In particular, IL-4 and IL-13 are the important cytokines related with intestinal mucus production via STAT6 signalling in nematode infections. However, this perspective has never been studied in Gymnophalloides seoi infection. The present study aimed to observe the STAT6 signalling and cytokine responses in C57BL/6 mice, a mouse strain resistant to infection with this trematode. The results showed that worm expulsion occurred actively during days 1-2 post-infection (PI), when goblet cells began to proliferate in the small intestine. The STAT6 gene expression in the mouse spleen became remarkable from day 2 PI. Moreover, G. seoi infection induced a significant increase of IL-13 from day 4 PI in the spleen of infected mice. Our results suggested that goblet cell hyperplasia and worm expulsion in G. seoi-infected mice should be induced by STAT6 signalling, in which IL-13 may be involved as a dominant triggering cytokine.

Sixteenth CenturyGymnophalloides seoiInfection on the Coast of the Korean Peninsula

Gymnophalloides seoi is a trematode species discovered as recently as 1993. Interestingly, ancient G. seoi eggs were identified in our earlier study on a 17th Century female mummy unearthed in a Korean county (HD-1) where G. seoi infection, according to a nationwide survey of 2001, was considered not to have been endemic. Although we suspected that the geographical distribution of G. seoi might have contracted over the past several hundred years from wider coastal areas on the Korean peninsula to the much more restricted region delineated by the survey, there has been only the single, above-noted report of an ancient G. seoi infection in a currently non-endemic area. As such, more evidence is needed before our contraction theory of G. seoi infection prevalence can be confirmed as fact. Our current report in this regard will perhaps help to end the controversy. In a newly discovered 17th Century male mummy found in another Korean county considered non-endemic by the 2001 survey, we identified a large number of ancient G. seoi eggs. We believe that this additional evidence for a wider distribution of G. seoi infection prior to the 20th Century is invaluable support for our earlier hypothesis.

Gymnophalloides seoi Eggs from the Stool of a 17th Century Female Mummy Found in Hadong, Republic of Korea

It was previously reported that paleoparasitological clues for parasites infecting humans could be found in the feces of mummies of the Joseon Dynasty (1392-1910) in the Republic of Korea. Here, we report the presence of trematode eggs, including Clonorchis sinensis, Metagonimus yokogawai, and Gymnophalloides seoi (a human parasite known in Korea since 1993) in the feces of a recently excavated female mummy in Hadong, Republic of Korea. This is the first report of the discovery of a G. seoi infection in a human mummy. Since Hadong is currently not an endemic area for G. seoi, we speculate that the parasite might have occurred frequently along coastal areas of the Korean peninsula several hundred years ago and that the endemic areas contracted to, more or less, restricted regions since that time.

A new endemic focus of Gymnophalloides seoi infection on Aphae Island, Shinan-gun, Jeollanam-do

A new endemic focus of Gymnophalloides seoi infection has been discovered on Aphae Island (Shinangun, Jeollanam-do), Republic of Korea. This area, which is referred to as Bokyong-ri, is a small seashore village located in the northern portion of the island. Fecal samples were collected from a total of 57 residents and examined by the Kato-Katz and formalin-ether sedimentation techniques. Helminth eggs were detected in 37 samples (64.9%); 33 samples were positive for G. seoi eggs (57.9%), 4 for Pygidiopsis summa (7.0%), 13 for other heterophyids (22.8%), 1 for Clonorchis sinensis (1.7%), and 1 for Trichuris trichiura (1.7%). Women (70.4%) revealed higher rates of G. seoi infection than did men (46.7%), and individuals older than 50 years of age also evidenced higher rates of G. seoi infection than in other age groups (P < 0.05). In worm collection from 13 G. seoi egg positive cases, G. seoi (total 86,558 specimens), Heterophyes nocens (278), Stictodora sp. (10), Heterophyopsis continua (3), P. summa (3), and unidentified flukes (42) were collected. Oysters, the source of G. seoi infection, were collected from an area proximal to the village and 50 were examined for metacercariae; 47 (94%) were found infected and the observed metacercarial density was 9.5 +/- 8.9 per oyster. The results of this study indicate that Bokyong-ri is a new endemic area of G. seoi infection, with high rates of infection in humans and oysters.

Susceptibility of Avian Hosts to ExperimentalGymnophalloides seoiInfection

To determine whether avian species are susceptible to infection with Gymnophalloides seoi (a human-infecting intestinal trematode), we exposed 7 species of birds with metacercariae obtained from oysters. The birds were necropsied at days 2, 4, and 6 postinfection (PI). The highest worm recovery at day 6 PI was obtained from the Kentish plover (Charadrius alexandrinus; mean = 56.0%), followed by the Mongolian plover (C. mongolus; 49.3%), and the grey plover (Pluvialis squatarola; 32.3%). In contrast, no mature worms were recovered from the great knot (Calidris tenuirostris), dunlin (C. alpina), black-tailed gull (Larus crassirostris), and mallard (Anas platyrhynchos). Among the plovers, the worms attained the greatest size at day 6 PI (254.1 x 190.4 microm) in the Kentish plover, with a significantly higher number of eggs in the uterus. The 3 species of plovers are highly susceptible to experimental G. seoi infection, suggesting that they could play a role as definitive hosts for these worms in nature.

A nationwide survey of the prevalence of human Gymnophalloides seoi infection on western and southern coastal islands in the Republic of Korea.

A nationwide survey was performed to know the distribution and prevalence of human Gymnophalloides seoi infection on western and southern coastal islands in the Republic of Korea. A total of 4,178 fecal specimens were collected from residents on 45 (24 western and 21 southern) islands, and examined by Kato-Katz and formalin-ether sedimentation techniques. Eggs of G. seoi were detected from 160 (3.8%) people living on 22 (13 western and 9 southern) islands. The prevalence varied by the location of islands; higher on western islands than on southern islands. The highest prevalence was found on Amtaedo (25.3%), followed by Cheungdo (25.0%), and Anchwado (20.9%) (Shinan-gun). A little lower prevalence was observed on Munyodo (13.3%), Shinshido (12.9%), and Sonyudo (10.3%) (Kunsan-shi). Of the remaining islands, the regions showing the prevalence greater than 5% included Kohado, Dallido (Mokpo-shi), Pyeongildo, Kogumdo (Wando-gun), and Keogumdo (Kohung-gun). A strong age predilection was noted (p < 0.05); 95% of the infected people were over 40 years old. Females showed a little higher prevalence than males. The results indicate that human G. seoi infection is more widely distributed than previously considered. Nine of 11 islands (excluding the 2 known areas Munyodo and Sunyudo) that showed greater prevalence than 5% are regarded as new endemic foci of G. seoi.

Persistent endemicity of Gymnophalloides seoi infection in a southwestern coastal village of Korea with special reference to its egg laying capacity in the human host.

Follow-up studies have been conducted every three years on the endemicity of Gymnophalloides seoi infection in a small coastal village of Chollanam-do (Province), Korea, since it was first known as an endemic area in 1994. Special attention was given to its egg laying capacity in the human host. In fecal examinations, the overall helminth egg and/or cyst positive rate was 78.7% (74/94) in 1997 and 76.6% (82/107) in 2000. Among them G. seoi eggs showed the highest rate; 71.3% (67/94) in 1997 and 72.0% (77/107) in 2000. The average number of eggs per gram of feces (EPG) was 1,015 in 1997, while a reduced rate of 353 was observed in 2000. In 1997, total of 320,677 adult flukes of G. seoi (av. 10,344/person, 94-69,125 in range) were collected from the diarrheic stools of 31 treated patients. The EPG/worm obtained from 21 cases ranged from 0.04 to 0.77 (av. 0.23), suggesting density-dependent constraints on the worm fecundity. The relationship between the worm burden (X) and EPG/worm (Y) can be expressed as Y = 0.42.e-1.2 chi (r = 0.49). The results showed that G. seoi infection is persistently endemic in this village.

Purification and Characterization of a 16-kDa Cysteine Proteinase of Gymnophalloides seoi (Gymnophallidae) Metacercariae

Gymnophalloides seoi, a new human intestinal trematode transmitted by oysters, is highly prevalent in southwestern coastal areas of Korea. The aim of this preliminary study was to acquire an understanding of the pathogenesis of G. seoi infection, and, to this end, we followed 2 consecutive steps, Sephacryl S-300 HR and CM-Trisacryl M chromatography, to purifiy a 16-kDa proteinase from crude extract of G. seoi metacercariae. Enzyme activities were completely inhibited by L-trans-epoxysuccinylleucylamide (4-guanidino) butane (E-64) and iodoacetic acid, cysteine proteinase inhibitors, strongly suggesting that the enzyme is a cysteine proteinase. Activity of the proteinase was maximal at pH 5.0 in 0.1 M of buffer and potentiated in the presence of 5 mM dithiothreitol. The proteinase showed differential abilities to hydrolyze macromolecules and immunoglobulins; it completely degraded extracellular matrix proteins such as collagen and fibronectin during overnight incubation but digested hemoglobin very slowly. The proteinase also cleaved human immunoglobulins IgG2a and sIgA; heavy chains were more susceptible than light chains to its digestive activity. The proteinase showed no antigenicity on both enzyme-linked immunosorbent assay and immunoblots, however. Our results strongly suggest that the cysteine proteinase of G. seoi metacercariae is potentially significant in nutrient uptake and evasion by the worm of the host immune response.

Susceptibility of Various Species of Animals and Strains of Mice to Gymnophalloides seoi Infection and the Effects of Immunosuppression in C3H/HeN Mice

Susceptibility to Gymnophalloides seoi infection was studied in 8 species of animals, including 7 strains of mice; the effects of immunosuppression on susceptibility were examined in C3H/HeN mice. One hundred metacercariae of G. seoi isolated from naturally infected oysters were orally administered to each animal. Worm recovery rate (WRR), worm dimensions, and the number of uterine eggs were obtained at day 3 and day 7 postinfection (PI). Average WRR from gerbils, hamsters, and cats at day 7 PI was 28.0%, 14.2%, and 10.9%, respectively, the former 2 figures of which were significantly higher than the rate of 0.0-4.0% from Sprague-Dawley rats, dogs, ducks, guinea pigs, and chicks. In the case of mice, average WRR at day 7 PI was 12.4% (KK strain), 11.8% (C3H/HeN), 9.6% (ICR), 6.4% (BALB/c), and 6.3% (ddY), respectively; the first 3 figures were significantly higher than the rates from other strains, which were 1.8% (A) and 0% (C57BL/6). At day 3 PI, WRR was much higher in all strains except C57BL/6. Worm maturation was the highest in C3H/HeN mice. Immunosuppression of C3H/HeN mice by injecting prednisolone for 7, 14, or 21 days prior to infection increased WRR at day 7 PI to 27.8%, 33.8%, or 67.5%, respectively. The results show that gerbils, hamsters, cats, and KK, C3H/HeN, ICR. BALB/c, and ddY mice are laboratory hosts that are fairly susceptible to G. seoi infection. In C3H/HeN mice, susceptibility was markedly enhanced by immunosuppression.

A nationwide survey of naturally produced oysters for infection with Gymnophalloides seoi metacercariae.

A nationwide survey was performed to know the geographical distribution of Gymnophalloides seoi (Digenea: Gymnophallidae) metacercariae in Korea, by examining the infection status of locally produced oysters, Crassostrea gigas. A total of 24 coastal areas (myons) of 14 guns ( = counties) in Kyonggi-do, Chollabuk-do, Chollanam-do, Kyongsangnam-do, Kyongsangbuk-do, or Kangwon-do, where natural oysters are produced but G. seoi has never been reported, and 13 areas (myons) of Shinan-gun, Chollanam-do, nearby the known endemic area, were surveyed. Oysters from nonendemic areas were free from G. seoi infection, except Byonsan-myon of Buan-gun, Chollabuk-do, where one of 50 oysters examined was infected with 15 metacercariae of G. seoi. In Shinan-gun, oysters from 10 areas including Aphae-myon ( = township) and Anjwa-myon were infected with the metacercariae, with the infection rate ranging from 1.7% to 100% by areas. The intensity of infection was the highest in Aphae-myon. 785.9 metacercariae per oyster. The results indicate that high prevalence of G. seoi is confined to Shinan-gun, but low grade prevalence is also present in adjacent areas such as Buan-gun, Chollabuk-do.

High Prevalence of Gymnophalloides Seoi Infection in a Village on a Southwestern Island of the Republic of Korea

Gymnophalloides seoi (Digenea: Gymnophallidae), a new human intestinal trematode reported from a Korean woman who complained of epigastric discomfort, has been shown to be highly prevalent among the villagers of a southwestern island of the Republic of Korea. For the detection of human infections, fecal examinations were conducted on the inhabitants of a seashore village, where the first patient with a G. seoi infection had resided. Of 98 inhabitants examined, 70 (71.4%) were infected with various intestinal parasites; among them, G. seoi showed the highest rate of egg positivity 48 of 98 (49.0%). Individual worm burdens of G. seoi, as measured by collection of adult flukes after anthelmintic treatment and purgation, ranged from 106 to 26,373 specimens (average per infected case = 3,326). There was no sex-related difference in the prevalence of G. seoi, and the age distribution of the infected cases showed a relatively even pattern. This study confirms that human infection by G. seoi is not an incidental one and provides the first evidence of its high prevalence on this Korean island.