Eng-Rin Chen

Detection of Kobe-type Babesia microti associated with Japanese human babesiosis in field rodents in central Taiwan and southeastern mainland China

Field rodent surveys for Babesia infection were performed from 2002 to 2005 in the vicinities of human babesiosis occurrences in Taiwan and mainland China. Babesia microti was identified by microscopical examination and/or PCR in 1 Rattus coxinga and 1 Crocidura horsfieldii in central Taiwan and in 13 Niviventer confucianus and 1 Apodemus agrarius in Zhejiang and Fujian Provinces of southeastern China. Of 15 B. microti samples detected by PCR, all except 1 were shown to be the Kobe-type, the aetiological small subunit rRNA gene-type of the first Japanese patient; the exception was also a Kobe-related type. The Kobe-type had been found in rodents only in a few places including the human infection occurrence place in Japan. The internal transcribed spacer 1 to 2 sequences of the Taiwanese and Chinese Kobe-types were very similar to each other but considerably different (approx. 94% pairwise identities) from that of the Japanese Kobe-type. A Taiwanese Kobe-type strain was serologically differentiated from the Kobe strain originating from the Japanese first patient. The distribution of the Kobe-type in the vicinities of human babesiosis occurrences in Taiwan and China as well as in Japan is suggestive of involvement of the Kobe-type in Asian human babesiosis.

Role of T cell subpopulations in mice infected with Angiostrongylus cantonensis

When C57BL/6 mice were infected with Angiostrongylus cantonensis, the percentage of T helper (CD4+) cells and T supressor (CD8+) cells in peripheral blood increased weekly until the third and seventh week respectively, and then gradually decreased. C57BL/6 mice were depleted of CD4+ and CD8+ T cells by in vivo injection of anti-CD4 and anti-CD8 monoclonal antibodies, respectively, and then infected with A. cantonensis. There were significantly more and less worms recovered in the mice depleted of CD4+ and CD8+ T cells respectively than in undepleted mice. Discrete subpopulations of T cells from mice exposed to A. cantonensis for 3 weeks or 7 weeks were adoptively transferred to syngeneic recipients which were then given a challenge infection. Protection was mediated by a CD4+ T cell population present in mice after 3 weeks of infection but was not demonstrable with cells taken 7 weeks after infection. When CD4+ T cells obtained from 3-week infected mice were mixed with 5% CD8+ T cells obtained from mice infected for 7 weeks, no significant transfer of resistance was observed. Thus, immune responses to A. cantonensis in mice were regulated by discrete subpopulations of T lymphocytes.

Antibodies of different immunoglobulin isotypes in serum and bile of patients with clonorchiasis

Specimens of serum and bile from patients were assayed by an enzyme-linked immunosorbent assay to reveal antibodies specific to antigens from adult Clonorchis sinensis. Antibodies of the IgG isotype showed the greatest elevation during infection (Students t-test, P < 0.001), whereas serum IgA and IgE and secretory IgA in bile were moderately elevated (P < 0.05). Major differences in the distribution of antibodies among the IgG subclasses were observed between patients who were and those who were not infected. IgG4 antibody levels were elevated in the serum and bile of infected patients, and there were significant correlations between the levels of IgG and IgG4 antibodies and the intensity of infection.

Experimental infection routes of Angiostrongylus cantonensis in mice

Stomach intubation is the most common method used in the experimental infection of animals with Angiostrongylus cantonensis. In order to compare the effectiveness of other possible transmission methods, groups of BALB/c mice were given infective third-stage larvae of A. cantonensis by different routes including intraperitoneal or subcutaneous injections, and penetration of anal mucosa, vaginal mucosa, conjunctival mucosa, lacerated skin, unabraded skin, foot pad and tail skin, while stomach intubation was used as control. Recovery of fifth-stage larvae was higher in mice inoculated with third-stage larvae subcutaneously. Successful infections were established through all experimental transmission routes except tail skin penetration. This study suggests that oral infection may not be the only route for the transmission of human angiostrongyliasis, and subcutaneous infection may be a better method for experimental infection.

Enterobius vermicularis infection in schoolchildren: a large-scale survey 6 years after a population-based control.

Pinworm infection remains prevalent in children in many parts of the world. This study was designed to determine the prevalence of this infection in schoolchildren in Taiwan after the termination of the 15-year population-based control project in 2001. Our results showed that 2.4% of 118 190 children in 385 primary schools were found to have enterobiasis by two-consecutive-day adhesive cellophane perianal swabs. The prevalences were significantly different in the 25 counties/cities surveyed (0.6-6.6%). A significantly higher prevalence was found in boys (2.6%) than in girls (2.2%) and the prevalence decreased by grade from 3.8% in grade 1 to 1.0% in grade 6. In the primary schools, 9.1% had positive rates 10%. In addition, pinworm infection was found to be significantly associated with the socioeconomic status, personal hygiene and sanitary conditions of the children. The results indicate that the overall prevalence of enterobiasis remains at a low level after the control programme was transferred to the local governments.

Haplorchis infections in intermediate hosts from a clonorchiasis endemic area in Meinung, Taiwan, Republic of China.

Snails and freshwater fish were examined from four ponds in the Meinung township in which Clonorchis sinensis was known to be endemic 18 years ago. No metacercariae were found in 478 Tilapia nilotica, whereas of 451 Ctenopharyngodon idellus examined, 16.2%, 3.3% and 0.9% were found to be infected with Haplorchis pumilio, H. taichui and Clonorchis sinensis, respectively. In addition, there were some unidentified metacercariae in 12.0% of Ctenopharyngodon idellus examined. Overall, no positive correlation between infection rates and sizes of infected fish was shown. Six species of snails were collected in this survey and two frequently-occurring snails, Melanoides tuberculata and Thiara granifera were commonly infected with H. pumilio. Reasons for the prevalence of Haplorchis species and the absence of Clonorchis sinensis in fish and snail hosts in a previously reported endemic area for human clonorchiasis are discussed.

Intestinal Parasitic Infection Detected by Stool Examination in Foreign Laborers in Kaohsiung

Most foreign laborers in Taiwan come from Southeast Asia, where public health is not as well funded as in Taiwan, and parasitic infections are still common. Therefore, we recruited foreign laborers to undergo examination for parasitic infection to determine the infection conditions and follow‐up conditions in foreign laborers whose stools were found to be abnormal. A total of 7,360 foreign laborers were enrolled for stool examination in our hospital, and the merthiolate iodine formaldehyde method was used to diagnose intestinal parasite infection. In total, 331 (4.5%) foreign laborers were found to be infected, and Blastocystis hominis was identified as the most prevalent intestinal parasite (2.54%), followed by Trichuris trichiura (0.54%) and hookworm (0.53%). Parasite infection rates among laborers of different nationalities were also significantly different (p < 0.001). Forty‐two intestinal‐parasite‐infected foreign laborers received anti‐parasitic therapy in our hospital, and treatment was successful. Among the 154 intestinal‐parasite‐infected foreign laborers who did not receive treatment in our hospital but were later re‐examined, 132 were parasite‐free. B. hominis has been the most prevalent intestinal parasite infecting foreign laborers in Taiwan ever since it was added to the list of infections to be screened for stool examination by the Taiwan Centers for Disease Control in 2002. It is important to closely monitor, control and treat parasite‐infected foreign laborers to minimize the danger to public health.

A Survey on the Intestinal Parasites of the School Children in Kaohsiung County

The present study on the prevalence of intestinal parasites infection, from September to December 1999, was conducted among school children in Taoyuan Hsiang, Kaohsiung county. The investigated areas included three (Jiannshan, Shingjong and Taoyuan) primary schools. The overall infection rate in 305 children determined by Merthiolate-Iodine-Formaldehyde Concentration method of stools was 17%. Four confirmed species of helminthes (Ascaris lumbricoides, Hookworm, Trichuris trichiura and Hymenolepis nana) and three species of protozoa (Giardia lamblia, Entamoeba coli and Blastocystis hominis) were detected. Males and females had the infection rates of 24% and 11%. The infection rates of aboriginal and non-aboriginal children were 17% and 14%, respectively. Grade 1 and Grade 6 had the highest infection rate (21%). Following tape perianal examination of 302 children, the overall infection rate of Enterobius vermicularis was 25%. Males and females had the infection rates of 24% and 26%. The infection rates of aboriginal and non-aboriginal children were 27% and 11%, respectively. Grade 1 had the highest infection rate (37%). Based on these data, the infection rate of intestinal parasites among rural primary school children in Kaohsiung county remains high.

Capillaria hepatica: a spurious case with a brief review.

A 12-year-old Bunun aboriginal school student in Sanmin District Kaohsiung County, Southern Taiwan, was found to have Capillaria hepatica eggs in the feces during a survey on intestinal parasitic infection in 1997. Moreover, this student was also infected with Trichuris trichiura and Ascaris lumbricoides. The C. hepatica eggs were light yellowish-brown in color, 54 (40-60) microns in length and 29 (25-35) microns in width with a 3 (3-4) microns thick shell and two colorless egg plugs 7 (5-9) x 6 (5-8) microns. This is the eighth case of human spurious C. hepatica infection in Taiwan. In addition to the reporting of this case, the genuine and spurious infections of C. hepatica in humans as well as its infection in rats around the world are briefly reviewed.

The susceptibility of five stains mice to infections with Angiostrongylus cantonensis.

The susceptibility to the infection of Angiostrongylus cantonensis was studied in five inbred stains of mice including four H-2 haplotypes. Three weeks after infection, C57 BL/10J (H-2b) and C57BL/6J (H-2b) stains of mice showed the lowest, CBA (H-2k) and A/J (H-2a) stains showed intermediate, and the BALB/cJ (H-2d) mice showed the greatest susceptibility to infection. BALB/cJ mice also displayed the most body weight loss, the highest number of worms and showed the least number of days of survival. The s susceptibility of C57BL/6J (H-2b) and C57BL/10J (H-2b) strains of mice sharing same H-2 haplotype was the same despite their different genetic backgrounds. These data suggested that the H-2 gene might influence the susceptibility of mice to A. cantonensis.