Seroepidemiological study of Toxoplasma gondii infection in the rural area Okcheon-gun, Korea

There have been some reports about the prevalence of anti-Toxoplasma gondii antibody among Koreans, and most of all data were taken from patients visiting hospitals. However, the epidemiological data of the community-based study in Korea are rare. This study was performed to evaluate the seroprevalence of toxoplasmosis among the inhabitants of the rural area Okcheon-gun, Korea. A total of 1,109 serum samples (499 males, 610 females) were examined for the IgG antibodies by ELISA. To set up the cut-off point for ELISA, we used a commercial latex agglutination (LA) kit. The sensitivity and specificity of ELISA against LA test were 89.5%, and 98.6% respectively. Among 1,109 sera, 6.9% showed seropositivity by ELISA. The positive rates of males and females were 6.0% and 7.2%, respectively. However, there were no significant differences between sexes. Comparing the age groups, the highest seropositive rate showed in the seventies or higher, and their rates had a tendency to increase with age (0.05 < p < 0.3). These results revealed that the seroprevalence of toxoplasmosis in rural inhabitants is similar to previous reports in Korea; however we need further investigation to clarify the prevalence of toxoplasmosis in the general population.     

Seroprevalence of toxocariasis among healthy people with eosinophilia

The aim of this study is to determine the Toxocara seropositive rate among healthy people with eosinophilia. A total of 97 people residing in Seoul who were healthy and whose blood eosinophilia was over 10%, as shown by regular health check-ups in 2004, were subjected to this study. Their sera were tested by immunoblotting and ELISA with the antigen of larval Toxocara canis excretory-secretory (ES) protein. Sixty-five sera were band-positive (67.0%). The seropositve control sera were positive to band sizes of 66 kDa, 56 kDa, 32 kDa, and 13 kDa. In ELISA, 63 sera (65.0%) were positive to T. canis ES protein. There was no significant correlation between the IgG ELISA titer and the level of eosinophilia (r = 0.156, P = 0.156). As there were insufficient data to determine whether there were cross-reactions with other helminthic infections, or whether atopy occurred, further studies are required to verify the cause of the seropositive reactions against T. canis ES antigen. Toxocariasis seropositivity is suggested to be the major cause of eosinophilia, since the Toxocara seroprevalence among Korean rural adults was shown to be approximately 5%.     

A Hospital-Based Serological Survey of Cryptosporidiosis in the Republic of Korea

The seroprevalence of cryptosporidiosis was examined using patients'' sera collected from hospitals located in 4 different areas of the Republic of Korea. ELISA was used to measure antibody titers against Cryptosporidium parvum antigens from a total of 2,394 serum samples, which were collected randomly from patients in local hospitals; 1) Chungbuk National University Hospital, 2) Konkuk University Hospital, 3) local hospitals in Chuncheon, Gangwon-do (province), 4) Jeonnam National University Hospital, from 2002 through 2003. Of the 2,394 samples assayed, 34%, 26%, and 56% were positive for C. parvum-specific IgG, IgM, and IgA antibodies, respectively. Positive IgG titers were most common in sera from Jeonnam National University Hospital, Gwangju, Jeollanam-do, and positive IgM titers were most common in sera from Chungbuk National University Hospital, Cheongju, Chuncheongbuk-do. The seropositivity was positively correlated with age for both the IgG and IgA antibodies but was negatively correlated with age for the IgM antibodies. Western blotting revealed that 92%, 83%, and 77% of sera positive for IgG, IgM, and IgA ELISA reacted with 27-kDa antigens, respectively. These results suggested that infection with Cryptosporidium in hospital patients occurs more commonly than previously reported in the Republic of Korea.     

Analysis of larval antigens of Oestrus ovis for the diagnosis of oestrosis by enzyme-linked immunosorbent assay

A serodiagnostic test for the diagnosis of infestation by the sheep nasal bot fly, Oestrus ovis (Linné) was examined. The enzyme-linked immunosorbent assay (ELISA) technique was used to analyze and compare the production of immunoglobulin G (IgG) antibodies against excretory-secretory products (ESP) and crude extract (CE) antigens from all the different larval stages of O. ovis in the sera of 276 adult sheep sampled in summer (n = 135) and winter (n = 141). ESP from first stage larvae was the most sensitive, coating antigen in winter and ESP from second stage larvae during summer. The most specific values were obtained by ESP against L1 in winter and by CE against L3 in summer. These results show that the stage of larval development has a significant impact on the humoral immune response over the course of a season. A significant correlation (P < 0.001) was found between the number of O. ovis larvae and the serum antibody levels using all differents antigens, except L3 CE. In Spain, where a long favourable period exists for the evolution and development of the different stage larvae between March and November, the ELISA test using L1 ESP antigen during winter and L2 ESP antigen in summer may be used for ovine oestrosis immunodiagnosis.     

A seroepidemiological survey for toxocariasis in apparently healthy residents in Gangwon-do,Korea

We investigated the sero-prevalence of toxocariasis among healthy Korean adults in 1999. A total of 314 sera from normal inhabitants in Whachon-gun, Gangwondo, Korea was examined for specific antibody levels against excretory-secretory products of second stage larvae of Toxocara (TES). The presence of cross-reactions with other helminthiases such as cysticercosis, paragonimiasis, sparganosis or clonorchiasis was also checked by specific IgG ELISA. Sera showing positive reaction against TES were also tested by IgG immunoblot and by IgE ELISA. Out of 314 subjects, 16 was found to be positive by TES IgG ELISA and immunoblot, among whom 12 were also positive by TES IgE ELISA. Among the 16 seropositive samples, two sera showed positive reaction against Paragonimus and sparganum antigen, respectively. These results inferred that cross-reactions were negligible between toxocariasis and other helminthiases. Toxocariasis seroprevalence among Korean rural adults was detected to be approximately 5%.     

Serologic Survey of Toxoplasmosis in Seoul and Jeju-do, and a Brief Review of Its Seroprevalence in Korea

Knowledge of the prevalence of human Toxoplasma gondii infection is required in the Republic of Korea. In this study, we surveyed the seroprevalence of T. gondii infection and analyzed the risk factors associated with seropositivity among residents in 2 administrative districts; Seoul and the island of Jeju-do, which have contrasting epidemiologic characteristics. Sera and blood collected from 2,150 residents (1,114 in Seoul and 1,036 in Jeju-do) were checked for IgG antibody titers using ELISA and for the T. gondii B1 gene using PCR. In addition, participants completed a questionnaire that solicited information on gender, age, occupation, eating habits, history of contact with animals, and travel abroad. The T. gondii B1 gene was not detected in all residents examined. However, ELISA showed 8.0% (89 of 1,114 sera) positive for IgG antibodies against T. gondii in Seoul and 11.3% (117 of 1,036 sera) in Jeju-do. In both districts, the positive rates were higher in males than in females, and those 40-79 years of age showed higher rates than other ages. In Seoul, residents older than 70 years of age showed the highest positive rate, 14.9%, whereas in Jeju-do the highest prevalence, 15.6%, was in those in their sixties. The higher seropositive rate in Jeju-do than in Seoul may be related to eating habits and occupations. The present results and a review of related literature are indicative of an increased seroprevalence of T. gondii in Korea in recent years.     

Western blot antibody determination in sera from patients diagnosed with Anisakis sensitization with different antigenic fractions of Anisakis simplex purified by affinity chromatography

Using Western blot techniques, the specificities of crude and purified (PAK and PAS) Anisakis simplex antigens were compared against 24 sera from patients diagnosed with Anisakis sensitization. All patients recognized a 60 kDa protein against the A. simplex crude extract, while 37.5% and 12.5% reacted with proteins of 40 and 25 kDa, respectively, when IgG was tested. In the case of IgE determination, 41.6% of sera were negative, while 12.5% and 20.8% appeared to cross-react against Toxocara canis and Ascaris suum, respectively. When the PAK antigen (A. simplex antigen purified by means of a column of IgG anti-A. simplex) was tested, immune recognition towards the 60, 40 and 25 kDa proteins increased in 83.3%, 16.7% and 4.2%, respectively, when the Ig antibodies were tested. In the case of the PAS antigen (PAK antigen purified by means of a column of IgG anti-A. suum), the reaction against the 40 and 25 kDa proteins increased to 45.8% and 25%, respectively, when Ig antibodies were used. Finally, when the EAS antigen (eluted from the anti-A. suum column after PAK purification) was tested, 83.3% of the assayed sera reacted against the 14 kDa protein, when the Ig antibodies, IgG and IgM immunoglobulins were measured. With the IgE determination, the reactions were observed in 41.7% of patients with proteins between 60 and 35 kDa against the PAS antigen. With the EAS antigen, reactive bands of 184, 84 and 14 kDa appeared. In conclusion, in the purification process of the A. simplex larval crude extract, the proteins implicated in cross-reactions with Ascaris and Toxocara were eliminated, with an important concentration of proteins responsible for the induction of specific responses.     

Anisakis simplex: the activity of larval products on the complement system

The effects of the larval products (crude extract and excretory-secretory) of Anisakis simplex on the classical and alternative pathways of human complement system were investigated. This could constitute a mechanism to evade host defences, similarly than in other parasitic diseases. The larval products showed a stronger effect on the classical pathway than on the alternative pathway. The most pronounced modulating effects were found for the excretory-secretory products. Chelation of bivalent cations (Ca(2+) or Mg(2+)) by these larval products may be responsible for their mode of action on the alternative pathway, whereas the chelation is not likely to be particularly involved in the anticomplementary activity found on the classical pathway. Detailed studies revealed that the larval products of A. simplex act at the level of the C3 and other complement components. Heating the crude parasite extract led to a notable loss of haemolysis inhibition activity, and the addition of PMSF (a serine protease inhibitor) also cause variation in the activity of the crude extract.     

Immune reactions and allergy in experimental anisakiasis

The third-stage larvae (L3) of the parasitic nematode, Anisakis simplex, have been implicated in the induction of hyperimmune allergic reactions in orally infected humans. In this work, we have conducted a review of an investigation into immune reactions occurring in animals experimentally infected with A. simplex L3. The patterns of serum antibody productions in the experimental animals against excretory-secretory products (ESP) of A. simplex L3 contributed to our current knowledge regarding specific humoral immune reactions in humans. In our review, we were able to determine that L3 infection of experimental animals may constitute a good model system for further exploration of immune mechanisms and allergy in anisakiasis of humans.     

Seroprevalence of toxoplasmosis in Korean pregnant women

This study was performed in order to evaluate the sero-epidemiological status of toxoplasmosis in pregnant Korean women. Among 5,175 sera and 750 amniotic fluid samples obtained from pregnant women, 41 serum samples (0.79%) and 10 (1.33%) amniotic fluid samples tested positive for IgG antibodies by ELISA. Fifty one cases showing a score more than 0.25 on ELISA were tested for PCR reaction against the SAG1 gene. Only one case of the 51 ELISA positive cases exhibited a positive reaction on all tests. This case had a history of acute nephropyelitis during early pregnancy, but fortunately, had delivered a phenotypically healthy baby. In this study, the seroprevalence of toxoplasmosis in pregnant women was found to be comparatively low, consistent with previous reports from Korea. However our trials, performed with a variety of diagnostic tools, were considered to be useful for the precise diagnosis of congenital toxoplasmosis.     

A potentially important excretory-secretory product of Giardia lamblia

In this study we have reported the detailed characterization of a 58 kDa excretory-secretory product (ESP) of Giardia lamblia. The method of purification has been simplified which has improved the purification fold as well as the yield of the ESP. The binding efficacy of disialoganglioside (GD2) to the purified ESP was found to be maximum among all other gangliosides used. The N-terminal sequence of the immunoreactive 29 kDa peptide obtained from partial tryptic digest of the ESP was found to be AD-FVPQVST. The IgG against the purified ESP (IgGES) showed cross-reactivity with the binding subunit of the commercially available cholera toxin and also with two protein bands of western cottonmouth moccasin snake toxin. The ESP could accumulate fluid in the intestine of sealed adult mice and also induce morphological changes in HEp-2 cells. The crude extract of G. lamblia trophozoites preincubated with Escherichia coli revealed 8-fold augmentation in the cytopathic activity on HEp-2 cells as compared to that of crude preparation from trophozoites only.     

Seroprevalence of Toxoplasmosis in the Residents of Cheorwon-gun, Gangwon-do, Korea

The seroepidemiological status of toxoplasmosis was surveyed among the residents of Cheorwon-gun, Gangwon-do by means of ELISA using a crude extract antigen of Toxoplasma gondii. The sera of 1,661 adult residents (866 males and 795 females) were collected and checked for IgG antibody titers, which showed 17.0% positive rate (282 sera). The positive rate was significantly different between the sex; 20.6% for males and 13.1% for females (P<0.05). The positive rates were higher in fifties of males (28.7%) and forties of females (20.0%). This positive rate of toxoplasmosis in Cheorwon-gun residents is regarded as the highest among the surveys of different geographical regions of Korea. This high positive rate may due in part to peculiar geographical locality of the surveyed area near the naturally well preserved demilitarized zone (DMZ) or presumably consumption of the pork imported from high endemic nations. Therefore, it is necessary to study further the epidemiology of toxoplasmosis in Cheorwon-gun.     

Protease activity of 80 kDa protein secreted from the apicomplexan parasite Toxoplasma gondii

This study describes the characterization of 80 kDa protease showing gelationlytic property among three proteases in the excretory/secretory proteins (ESP) from Toxoplasma gondii. The protease activity was detected in the ESP but not in the somatic extract of RH tachyzoites. This protease was active only in the presence of calcium ion but not other divalent cationic ions such as Cu(2+), Zn(2+), Mg(2+), and Mn(2+), implying that Ca(2+) is critical factor for the activation of the protease. The 80 kDa protease was optimally active at pH 7.5. Its gelatinolytic activity was maximal at 37 degrees C, and significant level of enzyme activity of the protease remained after heat treatment at 56 degrees C for 30 min or 100 degrees C for 10 min. This thermostable enzyme was strongly inhibited by metal chelators, i.e., EDTA, EGTA, and 1,10- phenanthroline. Thus, the 80 kDa protease in the ESP secreted by T. gondii was classified as a calcium dependent neutral metalloprotease.     

A Surge in the Seroprevalence of Toxoplasmosis among the Residents of Islands in Gangwha-gun, Incheon, Korea

Seroepidemiological changes of Toxoplasma gondii infection among the residents of the islands of Gangwha-gun, Incheon for 2 years were surveyed and evaluated by ELISA using a crude extract antigen. In 2010, sera of 919 adult residents in Gyodong-myeon and 313 adults in Samsan-myeon were collected and checked for IgG antibody titers, which showed 14.5% (133 sera) and 19.8% (62 sera) positive rates, respectively. In 2011, sera of 955 adults in Gyodong-myeon and 341 adults in Samsan-myeon were examined, which showed an increase of positive rates to 23.8% (227 sera) and 31.7% (108 sera), respectively. Totally, the seroprevalence of the first year was 15.8% and it increased rapidly to 25.8% in the second year. The positive rates of both sexes increased simultaneously with the significant ratio of males to females by 1.7-2.2 fold (P<0.05). In both myeons, 661 sera were collected every year and showed changes in optical density (OD) in 177 sera; newly found as positives in 73 persons (11.0%), negative conversion in 10 persons (1.5%), and maintained or increased in 94 persons (14.2%). This rapid increase in the prevalence of toxoplasmosis in Gangwha islands may be due to in part peculiar changes in the toxoplasmic environment of the islands and presumably the consumption of the pork bred domestically within the islands or imported from high endemic nations. It is necessary to find out symptomatic toxoplasmic patients and confirm the risk factors for further infection in the islands of Gangwha-gun.     

Cross-reactivity between sera from dogs experimentally infected with Dirofilaria immitis and crude extract of Toxocara canis

This study was performed to investigate whethere there is cross-reactivity between Dirofilaria immitis and three intestinal nematodes of dogs. In ELISA, D. immitis-infected dog sera obtained at the 4th molting stage (9-11 weeks) and microfilaremic stage (25-30 weeks) were shown to be highly reactive with crude extract of T. canis. In immunoblotting, some antigenic fractions, 44, 57, 88, 100 kDa of crude extract of T. canis, were found to be positive reaction with sera of dogs infected with D. immitis. However, little or no cross-reaction were observed between sera of D. immitis-infected dogs and crude extract antigen of T. vulpis or A. caninum. These result suggest that there are partial cross reaction between sera of D. immitis-infected dogs and the antigen of T. canis.     

Seroprevalence of Encephalitozoon cuniculi in Pet Rabbits in Korea

Encephalitozoon cuniculi is a microsporidian parasite commonly found in rabbits that can infect humans, causing encephalitozoonosis. The prevalence of encephalitozoonosis is not well documented, even when many clinics suspect pet rabbits as being highly infected. This study investigated the seropositivity of E. cuniculi using ELISA. The examination of 186 rabbits using ELISA showed that 22.6% (42/186) were seropositive against E. cuniculi. In analysis with healthy status, all 42 seropositive sera were collected from clinically normal rabbits. Moreover, the gender and age of pet rabbits did not have anysignificant effect on E. cuniculi infection. To the best of our knowledge, this is the first report to describe the seroprevalence of E. cuniculi in pet rabbits and suggests that pet rabbits could act as an important reservoir of encephalitozoonosis for both pet animals and humans in Korea.     

High Toxoplasma gondii Seropositivity among Brain Tumor Patients in Korea

Toxoplasma gondii is an intracellular protozoan that can modulate the environment of the infected host. An unfavorable environment modulated by T. gondii in the brain includes tumor microenvironment. Literature has suggested that T. gondii infection is associated with development of brain tumors. However, in Korea, epidemiological data regarding this correlation have been scarce. In this study, in order to investigate the relationship between T. gondii infection and brain tumor development, we investigated the seroprevalence of T. gondii among 93 confirmed brain tumor patients (various histological types, including meningioma and astrocytoma) in Korea using ELISA. The results revealed that T. gondii seropositivity among brain tumor patients (18.3%) was significantly (P<0.05) higher compared with that of healthy controls (8.6%). The seropositivity of brain tumor patients showed a significant age-tendency, i.e., higher in younger age group, compared with age-matched healthy controls (P<0.05). In conclusion, this study supports the close relationship between T. gondii infection and incidence of brain tumors.     

Maintained seroprevalence of toxoplasmosis among the residents of Jeju island, Korea

Seroepidemiological status of toxoplasmosis among the residents of Jeju island was surveyed and evaluated by ELISA with crude extract of Toxoplasma gondii. The sera of 2,348 residents (male 1,157 and female 1,191) were collected and checked for the IgG antibody titers, which showed 13.2% positive rate (309 sera). The positive rates were increasing gradually according to the age from 4.3% in teenage to 20.6% in seventies. The positive rates were significantly different between the sex by 16.2% for male and 10.2% for female (P<0.05). This positive rate of toxoplasmosis in Jeju island residents is regarded relatively higher than any other regions of Korea. And the high positive rate may be maintained continuously among Jeju island residents without any clear reasons until now but due to some parts peculiar socio-cultural tradition of Jeju island. Therefore, it is necessary to study further the epidemiology of toxoplasmosis of Jeju island.     

A Recombinant Matrix Metalloproteinase Protein from Gnathostoma spinigerum for Serodiagnosis of Neurognathostomiasis

Neurognathostomiasis is a severe form of human gnathostomiasis which can lead to disease and death. Diagnosis of neurognathostomiasis is made presumptively by using clinical manifestations. Immunoblotting, which recognizes antigenic components of molecular mass 21 kDa and 24 kDa in larval extracts of Gnathostoma spinigerum (Gs 21/24), has high sensitivity and specificity for diagnosis of neurognathostomiasis. However, only very small amounts of the Gs 21/24 antigens can be prepared from parasites harvested from natural or experimental animals. To overcome this problem, we recently produced a recombinant matrix metalloproteinase (rMMP) protein from G. spinigerum. In this study, we evaluated this rMMP alongside the Gs 21/24 antigens for serodiagnosis of human neurognathostomiasis. We studied sera from 40 patients from Srinagarind Hospital, Khon Kaen University, Thailand, with clinical criteria consistent with those of neurognathostomiasis, and sera from 30 healthy control adults from Thailand. All sera were tested for specific IgG antibodies against both G. spinigerum crude larval extract and rMMP protein using immunoblot analysis. The sensitivity and specificity for both antigenic preparations were all 100%. These results show that G. spinigerum rMMP protein can be used as an alternative diagnostic antigen, in place of larval extract, for serodiagnosis of neurognathostomiasis.     

Seroprevalence of antibodies to Neospora caninum in dogs and raccoon dogs in Korea

Neospora caninum is an important cause of abortion in cattle, and dogs are its only known definitive host. Its seroprevalence among domestic urban and rural dogs and feral raccoon dogs (Nyctereutes procyonoides koreensis) in Korea was studied by indirect fluorescent antibody test (IFAT) and by the neospora agglutination test (NAT), respectively. Antibodies to N. caninum were found in 8.3% of urban dogs and in 21.6% of dogs at dairy farms. Antibody titers ranged from 1:50 to 1:400. Antibodies to N. caninum were found in six (23%) of 26 raccoon dogs. However, the potential role of raccoon dogs as a source of horizontal transmission of bovine neosporosis needs further investigation. The results of this study suggest that there is a close relationship between N. caninum infection among dairy farm dogs and cattle in Korea. This study reports for the first time upon the seroprevalence of N. caninum infection in raccoon dogs in Korea.