[Two new species of freshwater crabs (Decapoda: Potamidae) serving as intermediate hosts of Paragonimus in Fujian, China].

OBJECTIVE: To investigate the natural resources of the freshwater crab which can serve as the intermediate hosts of Paragonimus in Pinghe and Youxi of Fujian Province. METHODS: Freshwater crabs were collected. The morphological characteristics of the crabs and the habitats were observed. The crabs were dissected and examined for the presence of Paragonimus metacercariae. RESULTS: Two new species of crabs were described, named as Sinopotamon zhangzhouense sp. nov. and Bottapotamon youxiense sp. nov.. S. zhangzhouense sp. nov., holotype: male, carapace length 35.9 mm, breadth 42.8 mm, thickness 18.6 mm, collected from Pinghe County in southwest of Fujian. (24 degrees 14.206' N, 117 degrees 12.594' E). Distal segment of the first pleopod of male tended flattish, and showed palm nest-shaped concave, which divided into two point leafs, and longitudinal crack clearly identified in back. The end half of distal segment reversed to ventral outwardly. This species usually lived in the sluggish stream. The infection rate of Paragonimus westermani and P. cenocopiosus in S. zhangzhouense sp. nov. was 44.9% (35/78). B. youxiense sp. nov., holotype: male, carapace length 13.35 mm, breadth 16.63 mm, thickness 7.20 mm, collected from Youxi County in central Fujian (26 degrees 10.558' N, 118 degrees 22.012' E). The first pleopod of male was in slightly flat shape, ample and developed, as bow-like uplift. This species usually lived in the relatively flat terrain of stream. The infection rate of P. skrjabini metacercariae in B. youxiense sp. nov. was 92.1% (58/63). CONCLUSION: Two new species of freshwater crabs (S. zhangzhouense sp nov. and Ryouxiense sp. nov.) serving as the intermediate hosts of Paragonimus have been described.

[Study on the infectivity of Angiostronglus cantonensis in the epidemic foci].

OBJECTIVE: To analyze the degrees on the epidemic foci of Angiostronglus cantonensis and to explore the measurement methods. METHODS: Snails (Pila gigas) were collected from the spots of Wenzhou, Cangnan, Yongjia, Yueqing in Zhejiang province and Minhou, Changle, Ningde in Fujian province. The snails were examined microscopically in order to calculate their infection rates and the average worm number in the positive snails, then taking the product of multiplication of both values as infestation index. RESULTS: The infection rates of the epidemic foci were 10.59% (9/85), 60.74% (181/298), 34.96% (79/226), 32.90% (76/231), 57.50% (184/320), 40.00% (82/205), 17.65% (12/68) and the rates of infectivity were 6.57, 183.54, 121.73, 93.45, 276.36, 76.08, 12.65, respectively. CONCLUSION: The epidemic foci were divided into five ranks (super, high, mid-range, low and non-epidemic foci) according to the value of infestation index which ranked from > 75, 30-75, 5-29, < 5 to 0.

[Studies on the growth-development and infectivity of Angiostrongylus cantonensis in dormant Pomacea canaliculata].

OBJECTIVE: To study the impact of dormancy of Pomacea canaliculata on the growth-development and infectivity of Angiostrongylus cantonensis. METHODS: The intermediate host snails (P. canaliculata) were infected with the first stage larvae of A. cantonensis from the laboratory. One day after infection the snails were kept dormant under 25.0-25.5 degrees C, and a sample of the snails was selected and dissected to examine the larval growth-development at various interval. Twenty days after infection, they were placed in room with natural winter conditions. Every 10 days a sample of the snails was dissected for larval activity. The third-stage larval infectivity from each group was identified by infecting SD rats. Meanwhile the survival and weight change of snails in the two groups were recorded, and were compared with those snails cultured in water under the corresponding temperature conditions mentioned above. RESULTS: The time for first-stage larvae of A. cantonensis in dormant snails to develop to third stage was shorter than that in the snails in aquarium. All the third stage larvae at various degree of activity recovered from snails in winter room conditions, including dormant snails and active snails in water, infected rats successfully. The dormant snails in winter room conditions stopped growing with decreased weight, but the survival rate was significantly lower than that of the snails in aquarium with the same condition along with an extending time of dormancy. CONCLUSION: The development of A. cantonensis larvae has not been affected when snails are kept dormant under 25.0-25.5 degrees C. The third stage larvae from snails at natural winter room temperature or in aquarium were all infective. As of the overwintering ways, it is better to keep the infected snails dormant than in the aquarium.

[Development of PCR assay for detection of Angiostrongylus cantonensis in Pomacea canaliculata].

OBJECTIVE: To establish a PCR assay for detecting the third-stage larvae of Angiostrongylus cantonensis in Pomacea canaliculata. METHODS: Polymerase chain reaction primers were designed by the software Lasergene, based on the specific cDNA of the third-stage larvae of A.cantonensis in Genbank. The total RNA was prepared from the third-stage larvae of A.cantonensis and of the snails by TRIzol one-step protocol. Amplification by RT-PCR was carried out following the kit protocol. RESULTS: RT-PCR assay revealed a clear differentiation between infected and negative snails. When a mixture of the total RNA from the negative snails and the third-stage larvae of A.cantonensis was tested by the PCR assay, the detectable level was 128 pg RNA, a concentration close to one third-stage larva of A.cantonensis, minimum concentration that could be found by naked eyes. The minimum detected total RNA concentration of the third-stage larvae of A.cantonensis was 105 pg by PCR assay. CONCLUSION: A PCR assay has been developed for detecting A.cantonensis larva in Pomacea canaliculata.

[Studies on susceptibility of Pomacea canaliculata of different developmental stages to infection with Angiostrongylus cantonensis].

UNLABELLED: OBJECTIVE To study the susceptibility of Pomacea canaliculata of different developmental stages to Angiostrongylus cantonensis infection. METHODS: P. canaliculata snails breeding at laboratory were divided into four rank (I-IV) according to the weight, and infected with the first stage larvae of A. cantonensis from Fujian Province. Their mortality, infection rate, worm burden, and the size, development and distribution of larvae in snails were examined. RESULTS: Snails at different developmental stages were readily infected with A. cantonensis. The infection rate was between 76% and 100%, with no significant difference among the groups (P>0.05). Snails at earlier developmental stage showed higher mortality. The heaviest worm burden and the largest number of snails harboring more than 100 larvae were found in snails of rank III. In general the larvae in snails showed a synchronous development in the groups. Sizes of the third stage larvae in snails of various ranks were homogeneous. The period before the third stage larva emergence and the time for a peak percentage of the larvae exhibited no significant difference among the four ranks. The larvae widely distributed in various parts of snails, with more in the lung and foot, and larvae from snails of different ranks could all infect rats successfully. CONCLUSION: P. canaliculata of the four ranks can all be infected by the first stage larvae of A. cantonensis. Rank III snails may be better for studying the relationship between P. canaliculata and A. cantonensis. The potential role of young snails in angiostrongyliasis transmission should be recognized.

[Survey on the current status of important human parasitic infections in Fujian province].

OBJECTIVE: To understand the prevalence of important human parasitic diseases in Fujian province. METHODS: According to the national guidelines, clustered random sampling was made for the survey. Modified Kato-Katz thick smear was applied to examine helminth eggs for soil-transmitted nematodes and Clonorchis sinensis. Cellophane and swab technique was applied for detecting Enterobius vermicularis eggs in children under 12. Questionnairing, skin test, serological test and eosinophil examination were carried out for Paragonimus infection. Questionnairing and serological test were used for Taenia infection and cysticercosis. Retrospective investigation was conducted with the data on outpatient and hospitalized cases with parasitic diseases. RESULTS: 45,736 people at 73 spots of 24 counties were investigated and 14 species of parasites were found. The overall infection rate of intestinal helminth infections was 36.15%. The prevalence of Ascaris lumbricoides, hookworms and Trichuris trichiura was 9.55%, 19.73% and 11.48% respectively. The infection rate of Enterobius vermicularis and Clonorchis sinensis was 22.06% and 0.60% respectively. The positive rate of skin test and serological test among skin test positives for Paragonimus infection was 7.07% and 9.23% respectively. The serology positive rate for cysticercosis was 2.28%, only 3 cases of taenia infection were found from 16371 persons investigated. Human infections with Angiostrongylus cantonensis, Diphyllobothrium latus, Taenia saginata, and Gnathostoma spinigerum were found for the first time in the Province. Metorchis orientalis and Echinostoma aegyptiaca infections in human were first recorded. CONCLUSION: The overall prevalence of soil-transmitted nematodes has decreased significantly in the province, although still highly prevalent in social-economically less developed areas. Meanwhile, attention should be paid to the food-borne parasitic infections in human population.

[Epidemiological survey on the infection of Paragonimus westermani in Jiangxi Province].

OBJECTIVE: To investigate Paragonimus westermani infection in the intermediate hosts and animal reservoivs in Jiangxi Province. METHODS: Two forest farms in Jingan and Wanzai Counties and one town in Yushan County of Jiangxi Province were selected as pilots for epidemiological and retrospective survey. The intermediate hosts (snails, crabs) and reservoir hosts (cat, dog, civet cat, wildcat, etc.) were collected and examined. Data on the changes of ecological environment and people's behaviors were also collected. RESULTS: The average infection rate in Semisulcospira libertina and Sinopotamon spp. was 0.21% and 54.3% respectively, and that of reservoir hosts was 5.6%. Compared with those in 20 years ago, the infection rate in Sinopotamon spp. decreased considerably. CONCLUSION: The three areas are still endemic for P. westermani with lower prevalence than before possibly due to the change of ecological environment.

[Epidemiological study on group infection of Angiostrongylus cantonensis in Changle City].

OBJECTIVE: To make etiological and epidemiological investigation on the infection of Angiostrongylus cantonensis in 8 pupils in Changle City. METHODS: 1. CSF of patients was examined with the conventional method to detect pathogens and eosinophiles. 2. The fecal samples of wild rodents were collected from the spot and examined microscopically to discover the first stage larvae of A. cantonensis. 3. Snails (Pila gigas) were collected in the spot. The smashed head tissue was examined for the third stage larvae of A. cantonensis. 4. The patient's clinical symptoms and physical signs were recorded with an emphasis on central nervous system. RESULTS: 1. Two larvae of the third stage of A. cantonensis were found in CSF of one patient. Eosinophiles occupied 68% of the cell number in average (ranged from 47% to 83%) in CSF of the 8 patients. 2. The infection rate of the first stage larvae of A. cantonensis was 39.3% (44/112) in feces of the rodents. 3. The infection rate of the third stage larvae of A. cantonensis was 40.0% (82/205) in the snails. 4. Major clinical manifestations in the 8 patients included: severe headache(8/8), dizziness(8/8), nausea(8/8), vomiting(8/8), lethargy(7/8), lower limb hypodynamia(7/8). CONCLUSION: The confirmation of severe infection of A. cantonensis in 8 child patients demonstrated that a natural nidus of angiostrongyliasis is present in Chengle City.

[Morphological observation of Haplorchis pumilio].

OBJECTIVE: To provide the basis for the differentiation with similar species of intestinal flukes through observing the figure of Haplorchis pumilio. METHODS: Adults of H. pumilio were collected from the intestine of the cat which was infected with the encysted cercariae of H. pumilio for 45 days. The worms were observed after staining. Eggs and metacercariae of H. pumilio were collected and examined for their shape, size and morphological characteristics. Pseudorasbora parva, the fish host, was examined for the parasitized sites of metacercariae. RESULTS: The principal characteristics of the adults is the acetabulum degradation. There are only the genital sucker with 44-48 hamuli. The average measurement of eggs is 31.2 x 16.7 microns with a smooth shell. Its aceromion is not evident. The average diameter of metacercariae is 168.5 microns. There are squamous spines on metacercaria. The metacercariae only parasitize in the muscle between the basis of the fin and the fish body. The average measurement of metacercaria cyst is 445 x 95 microns, with squamous spines on the body surface. Hamuli are found on the genital sucker of metacercaria cyst. CONCLUSION: The morphological figures and parasitic sites of metacercaria, the genital sucker of the adult, and the number and form of the hamulus on the genital sucker provide basis for distinguishing H. pumilio from other intestinal flukes.