A comparative study of lung-microscopy and tissue homogenate in detecting Angiostrongylus cantonensis in the Pomacea canaliculata / 中国热带医学

@#Abstract: Objective　To compare the efficiency of lung-microscopy and tissue homogenate in the detection of Angiostrongylus cantonensis larvae from Pomacea canaliculate, with the amin of finding a simple and rapid method suitable for different scenarios. Methods　Pomacea canaliculata was caught and collected from ponds, ditches, rivers and other environments in the confirmed epidemic areas reported by predecessors. After each snail was weighed one by one, and dissected into two parts: lung sac and muscle. Firstly, each snail lung sac was check for nodules with lung-microscopy, and the nodules were picked out with anatomical needle and press them separately. Then, the worm was found and identified for worm species under microscope, and the lung sac and snail meat then was rechecked with tissue homogenate. Results　A total of 330 snails were detected, with 19.1% (63/330) snails with Angiostrongylus cantonensis stage Ⅲ larvae were detected by tissue homogenate and 15.8% (52/330) snails with nodules were detected by lung-microscopy. Among them, 36 snails with nodules and larvae were detected by the lung-microscopy, and all of them were positive by the tissue homogenate, with a coincidence rate of 100% (36/36); 16 snails with nodules but no larvae, among which 6 snails were positive and 10 snails were negative by the tissue homogenate, The false detection rate was 19.2% (10/52). 278 snails with no nodules, but 21 of them were detected by the tissue homogenate, the missing rate was 7.6% (21/278). There was no significant difference between tissue homogenate and lung-microscopy (taking the positive determination of nodules as the standard) (χ2=1.27, P=0.26, P>0.05). There was significant difference between tissue homogenate and lung-microscopy (taking the detection of larvae as the standard)(χ2=8.66, P = 0.003, P<0.01). There was no significant difference between the two methods and tissue homogenate in the detection rate of large snails ( ≥25 g, χ2=0.08，P=0.777; χ2=2.58, P=0.108), but there was significant difference between the two methods and tissue homogenate in the detection rate of small snail (≤10 g, χ2=5.63, P=0.02). Conclusions　Compared with the tissue homogenate, lung-microscopy is simple in the detection of large snails, requires less instruments and equipment, and its detection speed is faster. It is suitable for the field investigation of the natural focus of Angiostrongylus cantonensis. The tissue homogenate has high sensitivity, can directly display the insect state and activity, has strong insect vitality and high detection rate, it's more suitable for food safety risk monitoring.

[Data Integration and Information Sharing of Parasite Resources in Fujian Province].

Objective: To establish parasite library and database in Fujian Province by integrating information on human-animal coinfecting parasites, vectors and　intermediates, in the aim of resource sharing. Methods: According to the Standards and Technical Regulation for Preservation of Parasitic Germplasm Resources set by the Resource Sharing Platform for Parasitic and Tropical Diseases(referred to as Germplasm Resource Sharing Platform), the preserved and newly discovered parasitic germplasm resources in Fujian Center for Disease Control and Prevention were categorized, information described, preserved and displayed, and the information sharing was made through the Germplasm Resource Sharing Platform. Results: The library and database on parasites, medical vectors, and hosts were established. The library was comprised of 1 020 parasite specimens, vectors and hosts, including 100 （9.8%） adult worm specimens, 120（11.7%） eggs and larvae, and 800（78.4%） vectors and hosts. Information digitalization was achieved for 61 resources, including 9 species of nematodes, 16 species of trematodes, 7 species of tapeworms, 16 different medical mollusks, and 13 different medical arthropods, resulting in 3 150 pieces of information and 6 300 images. The database was integrated into the Germplasm Resource Sharing Platform for resource sharing. Conclusion: The library and database on parasite gemplasm resources in Fujian Province has been established. Information sharing is made available through the Germplasm Resource Sharing Platform.

[A case of imported schistosomiasis haematobia first reported in Fujian Province].

The first case of imported schistosomiasis haematobia in Fujian Province was detected and the patient was cured following treatment with praziquantel.

[Surveillance on the prevalence of soil-transmitted nematode infection in Fujian in 2006-2010].

OBJECTIVE: To analyze the prevalent trend of soil-transmitted nematode infection in Fujian Province during the past 5 year surveillance and evaluate the control effect. METHODS: From 2006 to 2010, fecal samples of the inhabitants of 3 years old and above were collected every November and examined for intestinal helminth eggs by the modified Kato s thick smear technique at the 2 surveillance sites: Punan village of Zhangzhou and Gushan village of Shaowu. Cellophane tapes were used to detect pinworm eggs for children aged 3-12. Soil samples were also collected from vegetable field, lavatory, courtyard and kitchen of 20 randomly selected families (in 2 villages) each with stool egg-positive findings and examined for ascaris eggs by a modified saturated sodium nitrate floatation method. RESULTS: The prevalence of soil-transmitted nematode infection at the surveillance sites decreased from 45.3% (946/2087) in 2006 to 15.1% (226/1494) in 2010, with a reduction of 66.6%. Among the infected subjects, hookworm infection occupied 75%-85%, while ascaris or trichuris infections each accounted for less than 10%. In terms of infection intensity, 65.2%-85.5% of the hookworm infection was light, and majority of the infected subjects were farmers. The pinworm prevalence in children were still high although it had dropped down from 46.1% (140/304) in 2006 to 29.8% (36/121) in 2010, declined by 35.4%. In the 5 years, totally 400 soil samples from 100 families were examined and 21 samples were found ascaris egg positive with viable eggs in only one sample. CONCLUSION: The 5 year surveillance reveals a decreasing trend of the soil-transmitted nematode prevalence but shows a relatively high hookworm infection rate in the population and pinworm infection in children.

[Prevalent trend of the infection of soil-transmitted nematodes in Fujian Province].

OBJECTIVE: To understand the endemic situation of soil-transmitted nematodes in Fujian Province. METHODS: According to the national guidelines, the survey spots were determined by clustered random sampling in nine prefectures (cities) of Fujian Province from 2007 to 2009. Residents of 3 years old and above were investigated. The eggs of roundworm, hookworm and whipworm in feces were checked by Kato-Katz method. Eggs per gram (EPG) in feces were calculated. The gender, age and education status of the investigated subjects were recorded. The results were evaluated in comparison to those in 1992 and 2003. RESULTS: Altogether 93 833 residents in 610 villages of 184 towns from 49 counties were investigated. The overall infection rate of soil-transmitted nematodes was 10.14% (9 511/93 833), decreased by 86.88% and 71.84% compared to that in 1992 and 2003, respectively. The prevalence of roundworm, hookworm and whipworm was 1.32%(1 234/93 833), 7.31% (6 863/93 833) and 1.73% (1 622/93 833), respectively. The average EPG of roundworm, hookworm and whipworm was 9 556, 526 and 156, respectively. The prevalence in males and females was 9.48% (4 385/46 246) and 10.77% (5 126/47 587), respectively, with a statistical difference (chi2 = 42.84, P < 0.01). There was also a statistical difference among the age groups (chi2 = 1 626, P < 0.01). The higher education level of the people, the lower prevalence (chi2 = 1 107, P < 0.01). CONCLUSION: The prevalence of soil-transmitted nematodes is on a downward trend in Fujian Province, but remained high in the underdeveloped areas. The hookworm infection rate is higher than the average of the nation.

[Survey on the foci of Paragonimus in Youxi, Yongtai and Pinghe Counties of Fujian Province].

OBJECTIVE: To investigate the natural foci of paragonimiasis in Youxi, Yongtai and Pinghe Counties of Fujian Province. METHODS: One village each from the three counties was selected according to reported paragonimiasis cases. Freshwater snails collected from fields were examined for cercariae. Freshwater crabs obtained in the fields were examined for metacercariae by washing filtration method or direct compression method. Feces of cats and dogs were collected for the detection of eggs by water precipitation. In order to identify the species of Paragonimus, 4 cats were orally fed with metacercariae. At the same time, the habitat of three survey sites was observed. RESULTS: Three fluke species, namely, P. skrjabini, P. westermani and P. cenocopiosus(Syn. Euparagonimus cenocopiosus) were found. In Banlin Village of Youxi County and Chishui Village of Yongtai County, the seropositive rate by IgG ELISA were 6.8% (21/309) and 6.8% (9/133), respectively. Four species of freshwater snails were found, two species of Tricula and one species of Pseudobythinella were newly identified first intermediate hosts of Paragonimus. Four species of freshwater carbs were found, one species of Nanhaipotamon served as a new second intermediate host of Paragonimus. In Youxi, the infection rate of P. skrjabini cercariae in snails and metacercariae in crabs was 2.1% (27/1 344) and 92.1% (58/63), respectively; the index of crab infection and the positive ratio of Paragonimus eggs in cat feces was 171.91 and 1/7, respectively. In Yongtai, the cercariae infection rate in Pseudobythinella and Tricula snails infected with P. skrjabini was 0.6% (4/690) and 0.1% (2/ 2330), respectively; the infection rate of P. skrjabini metacercariae in crabs was 18.2% (18/99); the index of crab infection was 9.12. In Pinghe, the infection rate of cercariae in Semisulcospira libertina and metacercariae in crabs was 03% (3/1092) and 44.9% (35/78), respectively; the index of crab infection was 616. CONCLUSION: Paragonimus skrjabini P. westermani and P. cenocopiosus have been found from the three counties of Fujian Province with different infection level in snails and crabs.

[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.