Human infections of fish-borne trematodes in Vietnam: prevalence and molecular specific identification at an endemic commune in Nam Dinh province

The prevalence of fish-borne trematodes in humans and their molecular identification was investigated in the Rang Dong commune of Nam Dinh province, Vietnam, between January 2009 and December 2010. A total of 405 people in this commune were interviewed on the habit of eating raw fish and all of their stool samples were collected using the Kato-Katz technique for examination of the presence of fish-borne trematodes. The worms (and eggs) were first morphologically examined, counted, described and identified, then the representative isolates were subjected for molecular species confirmation. A total of 385 adult flukes collected from 10 patients were morphologically identified to species and defined as Clonorchis sinensis (14.58%) in Opisthorchiidae family, Haplorchis taichui (32.29%), Haplorchis pumilio (52.08%) and Centrocestus formosanus (1.04%) in Heterophyidae family. A high rate (77.8%) of the interviewees was found to have the habit of eating raw fish. This habit was attributed to the high infection rate of fish-borne trematode in humans (22.72%; OR = 2.486). The infection rate of fish-borne trematodes in males was higher (29.3%) than that in females (16.0%) and increased by age, reaching the highest in the patients aged 40–59 years (28.2–28.7%). The infection intensity of fish-borne trematode was found light (336 EPG). Adult flukes were collected from a group of the patients with the highest intensity of infection and subjected to molecular and phylogenetic analysis using a portion (326 bp) of mitochondrial cox1. Phylogenetic tree inferred from cox1 sequences using sequence data for 34 isolates of opisthorchid, heterophyid, fasciolid, paragonimid, schistosomid trematodes and taeniid cestodes revealed that they are distinct groups. The newly collected with the known clonorchid and heterophyid isolates form the well defined taxonomic groups, respectively, confirming that C. sinensis and Haplorchis spp. (H. pumilio and H. taichui) were among the collected samples.     

Prevalence of Zoonotic Trematode Metacercariae in Freshwater Fish from Gangwon-do,Korea

The infection status of zoonotic trematode metacercariae was investigated in a total of 2,293 freshwater fish collected from 11 rivers or streams in 9 administrative regions of Gangwon-do, Korea for 5 years (2009-2013). All fish were collected by netting methods and examined using the artificial digestion methods. Clonorchis sinensis metacercariae were detected in 4 fish species, i.e., Pungtungia herzi, Squalidus japonicus coreanus, Acheilognathus rhombeus, and Ladislabia taczanowskii, from only Hantangang in Cheorwon-gun. Metagonimus spp. metacercariae were found in 1,154 (50.3%) fish and their average number per infected fish was 55.8. Among the positive fish species, especially Tribolodon hakonensis from Namdaecheon in Yangyang-gun and Plecoglossus altivelis from Osipcheon in Samcheok-si were most heavily infected. Centrocestus armatus metacercariae were detected in 611 (26.7%) fish and the average metacercarial burden per infected fish was 1,032. Two chub species, Zacco platypus and Zacco temminckii were highly and heavily infected with C. armatus metacercariae in almost all regions surveyed. Echinostoma spp. metacercariae were also found in 24 fish from a few localities, but their numbers per fish infected were very low. From the above results, it is confirmed that the metacercariae of intestinal flukes, especially Metagonimus spp. and C. armatus, were heavily infected, while C. sinensis metacercariae were rarely found in fish from Gangwon-do, Korea.     

Infection Status of Zoonotic Trematode Metacercariae in Fishes from Vientiane Municipality and Champasak Province in Lao PDR

The infection status of fishborne zoonotic trematode (FZT) metacercariae was investigated in fishes from 2 localities of Lao PDR. Total 157 freshwater fishes (17 species) were collected in local markets of Vientiane Municipality and Champasak Province in December 2010 and July 2011, and each fish was examined by the artificial digestion method. Total 6 species of FZT metacercariae, i.e., Opisthorchis viverrini, Haplorchis taichui, Haplorchis yokogawai, Haplorchis pumilio, Centrocestus formosanus, and Procerovum varium, were detected in fishes from Vientiane Municipality. The metacercariae of O. viverrini were detected in 50 (49.5%) out of 101 fishes (6 species), and their average number was 154 per fish infected. The remaining 5 species of heterophyid metacercariae were detected in 36.8%, 65.8%, 9.4%, 23.9%, and 5.1% fishes examined, and their average densities were 12, 1,038, 4, 15, and 13 per infected fish, respectively. In fishes from Champasak Province, 3 species of FZT metacercariae, i.e., O. viverrini, H. taichui, and H. yokogawai, were detected. Only 2 O. viverrini metacercariae were found in only 1 Barbonymus schwanefeldi. The metacercariae of H. taichui and H. yokogawai were detected in 60.0% and 50.0% of fishes examined, and their average densities were 47 and 28 per fish infected. By the present study, it has been confirmed that several species of FZT metacercariae are prevalent in fishes from Vientiane Municipality, with P. varium being a new member of FZT in Lao PDR. In comparison, FZT metacercariae are less prevalent in fishes from Champasak Province.     

Foodborne Trematode Metacercariae in Fish from Northern Vietnam and Their Adults Recovered from Experimental Hamsters

The prevalence of foodborne trematode (FBT) metacercariae was investigated in fish from 2 localities of northern Vietnam in 2004-2005. Freshwater fish (9 species) were collected from local markets in Hanoi City (n=76) and Nam Dinh Province (n=79), and were examined for FBT metacercariae using the artificial digestion technique. Adult flukes were obtained from hamsters experimentally infected with the metacercariae at day 8 post-infection. Three (Haplorchis pumilio, Centrocestus formosanus, and Procerovum varium) and 6 (Haplorchis taichui, H. pumilio, C. formosanus, P. varium, Stellantchasmus falcatus, and Heterophyopsis continua) species of FBT metacercariae were detected in the 2 regions, respectively. Overall, among the positive fish species, H. pumilio metacercariae were detected in 104 (80.0%) of 130 fish examined (metacercarial density per infected fish; 64.2). C. formosanus metacercariae were found in 37 (40.2%) of 92 fish (metacercarial density; 14.7). P. varium metacercariae were detected in 19 (63.3%) of 30 fish (Anabas testudineus and Mugil cephalus) (metacercarial density; 247.7). S. falcatus metacercariae were found in all 10 M. cephalus examined (metacercarial density; 84.4). H. continua metacercariae (2 in number) were detected in 1 fish of Coilia lindmani. Morphologic characteristics of the FBT metacercariae and their experimentally obtained adults were described. The results have demonstrated that various FBT species are prevalent in northen parts of Vietnam.     

草鱼生长与台湾棘带吸虫囊蚴内种群的关系

通过对草鱼鳃上台湾棘带吸虫囊蚴内种群的研究发现,随着草鱼的生长。其感染率,下蚴的平均密度都下降,其感染强度也呈下降的的趋势;草鱼鳃上囊蚴的频率分布,表明有大量的囊蚴寄生于少数草鱼鳃上,多数草鱼感染少量的囊蚴;囊蚴在草鱼不同组鳃片上的分布具有相同的变化规律;     

Estimation of abundance of abyssal demersal fishes; a comparison of data from trawls and baited cameras

The abundance of the macrourid Coryphaenoides (Nematonurus) armatus was investigated using a single warp trawl and baited camera at soundings from 2500 to 5000 m in the north-east Atlantic Ocean. There was no significant relationship between abundance ( n km⁻²) as determined from swept area of the trawl and numbers of fish photographed at standard baits. However, timing of the first arrival ( t _arr s) of the first fish at bait correlated well with the trawl data through the relationship: It is concluded that by measurement of arrival times, the baited camera provides a cost-effective complement to trawl sampling for estimating abundance of deep-water fish including Synaphobranchus kaupi, Anlimora rostratu and C. (N). armatus. However, some abundant species such as the roundnose grenadier Coryphaenoides rupestris were not attracted to baited long-lines or baited cameras and therefore could be sampled only by trawl.     

EFFECT OF IRRADIANCE ON GROWTH AND REPRODUCTIVE PROCESSES DURING THE CELL CYCLE IN SCENEDESMUS ARMATUS (CHLOROPHYTA)1

Synchronized populations of the chlorococcal alga Scenedesmus armatus (Chod.) Chod. were grown under five irradiance levels. During the cell cycles of these populations, reproductive processes such as DNA replication, nuclear division, protoplast fission, and daughter cell release and growth processes such as RNA and protein accumulation were followed. The amount of RNA and proteins increased stepwise with a short time interval between individual steps during which the rate of RNA and protein accumulation decreased. At each of the steps, the amount of RNA and protein approximately doubled and the number of steps increased with irradiance. At the end of each of the growth steps, a commitment to trigger the sequence of reproductive events (DNA replication, nuclear division, protoplast fission) was attained. After attaining the commitment point, the cells were able to trigger and terminate the whole reproductive sequence without any further growth, that is, even in the dark when the external supply of energy was cut off. With increasing irradiance, the number of commitment points attained during one cell cycle increased from one to four. Consequently, one to four sequences of the reproductive steps were triggered, and each of them ended by doubling the reproductive structures, which resulted in the formation of 2, 4, 8, or 16 daughter cells. The length of the precommitment periods shortened with increasing irradiance as the result of an increasing rate in growth. The length of postcommitment periods showed light independence and remained constant at the range of irradiances at which the number of growth steps and, consequently, the number of sequences of reproductive events did not change. At higher irradiances, the number of sequences of reproductive events increased, which caused a prolongation of postcommitment periods. The length of the cell cycle varied as a result of this distinct effect of irradiance on pre- and postcommitment periods.     

Studies on the Genus Chondrus (Gigartinaceae) from Dalian,China

Two species of Chondrus, C. armatus (Harv.)Okam. and C. yendoi Yamada et Mikami from the coast of Dalian, Liaoning, China, are reported in this paper. C. yendoi is new to China.     

台湾棘带吸虫尾蚴的实验生态研究

1994年8-10月作者研究了台湾棘带吸虫尾蚴的实验生态,结果表明:光照对尾蚴的逸出有明显的促进作用,尾蚴具有强烈的趋光性;水温26-28℃时,其LD50的时间为40h左右,LD90的时间为52h左右,全部死亡时间为56-60h,死亡的尾蚴数随时间的关系符合逻辑斯谛方程;尾蚴不断地活动于水体的各个深度,但大部分时间仍停留于水体的底层;尾蚴的逸出数在适温范围内随水温的升高而增多,且尾蚴的活动强度随之增强;处于半数死亡时间的尾蚴仍然具有感染力,90%死亡时间的尾蚴失去活动,也失去了感染力,尾蚴经口被动感染淡水鱼类.       

Hyperendemicity of Haplorchis taichui Infection among Riparian People in Saravane and Champasak Province,Lao PDR

In this study, we found that Haplorchis taichui, a heterophyid intestinal fluke, is highly prevalent, with heavy worm loads, among riparian people in Saravane and Champasak province, Lao PDR. Fecal specimens were collected from 1,460 people (717 men and 743 women) in 12 riparian (Mekong river) districts and were examined by the Kato-Katz fecal smear technique. The overall helminth egg positive rate was 78.8% and 66.4% in Saravane and Champasak province, respectively. The positive rate for small trematode eggs (STE), which included H. taichui and other heterophyids, Opisthorchis viverrini, and lecithodendriids, was 69.9% and 46.3% in Saravane and Champasak province, respectively. To obtain adult flukes, 30 STE-positive people were treated with 40 mg/kg praziquantel and then purged. Whole diarrheic stools were collected 4-5 times for each person and searched for fluke specimens using a stereomicroscope. Mixed infections with various species of trematodes (H. taichui, Haplorchis pumilio, O. viverrini, Prosthodendrium molenkampi, Centrocestus formosanus, and Echinochasmus japonicus) and a species of cestode (Taenia saginata) were found. However, the worm load was exceptionally high for H. taichui compared with other trematode species, with an average of 21,565 and 12,079 specimens per infected person in Saravane and Champasak province, respectively, followed by H. pumilio (41.9 and 22.5, respectively) and O. viverrini (9.4 and 1.5, respectively). These results show that diverse species of intestinal and liver flukes are prevalent among riparian people in Saravane and Champasak province, Lao PDR, with H. taichui being the exceptionally dominant species.