[Value of the antigen with molecular mass of 32 000 in immunodiagnosis of Angiostrongylus cantonensis].

OBJECTIVE: To evaluate the specificity and sensitivity of immunodiagnosis with the antigen with molecular mass of 32 000 of Angiostrongyliasis cantonensis(AC32). METHODS: The major antigenic protein AC32 was purified from the antigens of A.cantonensis adult worm by electroelution from SDS-polyacrylamide gels. AC32-enzyme linked immunosorbent assay (ELISA) and adult worm antigen (AWA)-ELISA were used to detect the specific IgG in the sera of normal rats (n=5) and rats with angiostrongyliasis (n=61), sera of healthy individuals (n=50) and patients (n=50) with angiostrongyliasis, schistosomiasis and other parasitosis. RESULTS: The positivity rate in AC32-ELISA of the sera from rats with angiostrongyliasis was 100%; without false positive results or cross reaction between AC32 and the sera of the normal control and patients infected with parasites other than A.cantonensis. CONCLUSION: AC32 of A.cantonensis is a valuable candidate antigen for immunodiagnosis of angiostrongyliasis with high sensitivity and specificity.

[Antigen analysis of Angiostrongylus cantonensis in different developmental stages].

OBJECTIVE: To analyze the difference among antigens of Angiostrongylus cantonensis in different developmental stages and identify dominant diagnostic antigen for angiostrongyliasis. METHODS: Antigens of A. cantonensis in different developmental stages were analyzed by SDS-PAGE and immunoblot. RESULTS: The protein bands of all developmental stages were similar on SDS-PAGE. The Mr 40000, 50000, 66000 and 80000 antigens reacted not only with the sera of rats infected by A. cantonensis but also with the sera of normal rats. The Mr 104000 antigen could be discerned by sera of rats infected with A. cantonensis for 2 weeks. The Mr 32000 antigen could be recognized by sera of rats 2 weeks after infection, and the reaction became stronger with the infection continued. CONCLUSION: The Mr 40000, 50000, 66000 and 80000 antigens might result in the unspecific reaction in the immunodiagnosis of angiostrongyliasis using the crude antigen of A. cantonensis. The Mr 104000 of larva, Mr 33000 of adult females and Mr 32000 of the worms might be used as candidate antigens in early diagnosis and epidemiological survey of angiostrongyliasis.

[Geographic distribution and gene sequencing of Paragonimus westermani in some areas of Guangdong Province].

OBJECTIVE: To investigate the current distribution of Paragonimus westermani in Guangdong Province. METHOD: Snails and crabs collected from mountain streams in regional survey sites were dissected to detect cercarial and metacercarial infections of P. westermani. Domestic cats and dogs artificially infected with the collected metacercariae were also dissected to detect adult worms of P. westermani. The COI and ITS2 gene sequences of those adult worms were compared with those of known Paragonimus specimen deposited in the GenBank. RESULTS: All of the first intermediate hosts in five survey sites of Liangkou, Nankun, Mountain, Dadong, Muxi, Guowu, were identified as Semisulcospira libertina, whose cercariae infection rates were 0.33%, 0.15%, 0.058%, 0.10%, and 0.05%, respectively; the second intermediate hosts in above five sites were all identified as Sinopotamon denticulatum, whose metacercariae infection rates were 100%, 100%, 38.09%, 55.36%, and 65.26%, respectively. The numbers of metacercariae in the five sites were 79.4, 105.66, 9.16, 16.18, and 15.6 per positive crab, respectively, and 11.12, 7.87, 0.58, 0.69, and 0.85 per gram of crab, respectively. All the metacercariae were identical to those of P. westermani. Adult worms and eggs of P. westermani were found in both reservoir hosts of domestic cats and dogs infected artificially. By comparing the COI genes of five representative samples from each survey site with that of Paragonimus #AF219379.21, AF540958.1 from GenBank, we found out the homology to be 99%, 99%, 99%, 98%, and 99%, respectively. In addition, a comparison of the ITS2 gene sequences between the above five samples and Paragonimus #DQ836243.1, DQ351845.1, AB354217.1 from GenBank revealed 98%, 99%, 98%, 98%, and 98% gene homology, respectively. CONCLUSION: Two ultra-high and three high endemic areas of P. westermani are discovered in Guangdong Province. No obvious differences were found among the types of P. westermani in the above five endemic areas.

[Investigation on spread and hazards of human parasites in Qushui Village, Suixi County, Zhanjiang City].

OBJECTIVE: To understand the transmission of human parasites in Qushui Village, Yangqing Town, Suixi County, Zhanjing City, Guangdong Province. METHODS: The direct stool smear, floatation, Kato-Katz technique, and hookworm larva culture were used for the parasite infections. The questionnaire survey was applied for the hazards of parasites. The dissections on rats and snails were used for Angiostrongylus cantonensis infection. RESULTS: Five parasites were found and the total infection rate was 10.75%. The infection rates of hookworm (Necator americanus), Ascaris lumbricoides and Trichuris trichiura were 6.07%, 1.87% and 1.87%, respectively, and the infection rates of Enterobius vermicularis and Tyroglyrhus farinae were both 0.47%. The infections were not correlated with the career and age but preferred to males. The densities of infections were slight. The rate of dermatitis caused by hookworm larvae was 69.23%. The infection rates of Angiostrongylus cantonensis were 16.66%, 13.04% and 10.00%, respectively in rats, Achatina fulica and Ampularum crossean. CONCLUSION: The main species of human parasites are nematodes, with hookworm predominately, in Qushui Village, Suixi County. This area is the natural foci of Angiostrongylus cantonensis.

[Investigation on snails Achatina fulica and Pomacea canaliculata infected with Angiostrongylus cantonensis in Panyu region of Guangzhou City].

OBJECTIVE: To understand the natural infection status of Angiostrongylus cantonensis in snails Achatina fulica and Pomacea canaliculata from Panyu region of Guangzhou City. METHODS: The snails Achatina fulica and Pomacea canaliculata captured from the field were digested with the artificial stomach fluid. The third-stage larvae of A. cantonensis were examined and counted under a microscope. The collected third-stage larvae were used to infect SD rats. RESULTS: A total of 367 Achatina fulica and 357 Pomacea canaliculata were examined. The infection rate of A. cantonensis in Achatina fulica was 22.62%, with a mean intensity of 57.00 larvae per positive snail. The infection rate of A. cantonensis in Pomacea canaliculata was 3.08%, with a mean intensity of 1.64 larvae per positive snail. The infection rates of A. cantonensis in Achatina fulica from Dagang, Shiqi, Hualong, and Lanhe towns and Nansha District, were 13.33%, 15.00%, 20.93%, 73.68% and 8.41%, respectively. Those in Pomacea canaliculata were 5.88%, 2.88%, 1.89%, 0% and 3.96%, respectively. CONCLUSIONS: A. cantonensis infection exists in Achatina fulica and Pomacea canaliculata from Panyu region of Guangzhou City, and the infection in Achatina fulica is more serious than that in Pomacea canaliculata. The infection rates of the snails among five sites are different.

[Screening and identification of therapeutic effect evaluation antigens of angiostrongyliasis].

OBJECTIVE: To identify antigens which may help evaluate the therapeutic effect of angiostrongyliasis from adult worm antigen of Angiostrongylus cantonensis. METHODS: The adult worm antigens of A. cantonensis were analyzed by Western blotting with the sera of rats infected with A. cantonensis before and after treatment. The sera of rats were tested by enzyme-linked immunosorbent assay (ELISA). RESULTS: The antigens with relative molecular mass between 38,000 and 78,000 reacted not only with the sera of rats before treatment, but also with that after treatment. The antigens with M(r) between 190,000 and 17,000 reacted with the sera of rats before treatment but not with that after treatment; those with M(r) between 32,000 and 24,000 antigens strongly reacted with the former, but the reaction became much weakened with the latter. The AC32-IgG antibody appeared earlier than the AC-IgG, and disappeared rapidly after treatment. Six of the 10 treated rats became negative for AC-IgG as found by ELISA. CONCLUSION: The antigens of adult worm antigen of A. cantonensis with M(r) of 190,000, 32,000, 24,000, 17,000 and 16,000 may serve as candidate antigens for therapeutic effect evaluation of angiostrongyliasis.