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PubMed2004

Acanthoparyphium tyosenense (Digenea: Echinostomatidae): experimental confirmation of the cercaria and its complete life history in Korea.

Cercaria yamagutii Ito, 1957, was found in the marine mesogastropods Lunatia fortuni and Glossaulax didyma from the tidelands of Simpo located at the estuary of the Mankyoung River, which runs to the western coast of Korea. Metacercariae were found in a marine bivalve Mactra veneriformis after being infected with C. yamagutii experimentally. When a sea gull, Larus crassiostris, was fed with the metacercariae collected from the infected M. veneriformis, adult worms were recovered 10 days later. It was confirmed that the parasites collected from L. crassiostris were Acanthoparyphium tyosenense Yamaguti, 1939. From the results of this life cycle study, it was determined that the first intermediate hosts of A. tyosenense are L. fortuni and G. didyma. The second intermediate and final hosts are M. veneriformis and L. crassiostris, respectively. Mactra veneriformis was experimentally infected with C. yamagutii isolated from L. fortuni and G. didyma by maintaining them in a water tank for 30 min at about 20 C. The cercariae entered M. veneriformis through their incurrent siphons. Five hours after infection, the cercariae tails began to separate from the bodies, and the cercariae formed cysts. Mature cysts were formed 340 hr (14 days) after infection and identified as the metacercariae of A. tyosenense. The prevalence of A. tyosenense metacercariae was 99.5% in naturally infected M. veneriformis. This is the first report of C. yamagutii as the cercaria of A. tyosenense, and the complete life cycle of A. tyosenense was established in Korea.

Animals↗
PubMed1984

[Study on sensory papillae of Metagonimus yokogawai cercaria]

A number of studies on the papillae of cercariae of trematodes reported that the papillar patterns (or chaetotaxy) of cercariae might be an excellent method to attain better understanding of the digenetic trematodes (Richard, 1971; Short and Cartrett, 1973; Bayssade-Dufour, 1979). The present study was aimed to determine the number, distribution pattern and structure of the sensory papillae of Metagonimus yokogawai cercariae, and to elucidate the chaetotaxy of this digenetic trematode. M. yokogawai cercariae were pipetted from a vial in which infected snails (Semisulcospira libertica) had been kept for 3 hours. The snails were collected from an endemic area of M. yokogawai, Boseong river in west-southern part of Korea. Observations of papillae were based on light microscopy of those stained with silver nitrate, and on scanning electron microscopy. The results are summarized as follows: All papillae observed were uniciliated. Cilia in anterior tip were shorter than the others in other portions. The body papillae were arranged in essentially symmetrical patterns. Total number of the papillae was 126(63 pairs) in average; anterior tip 40(20 pairs), ventral 20(10 pairs), lateral 42(21 pairs), and caudal 8(4 pairs). The chaetotaxy of M. yokogawai cercaria was; C(I) cycle (3+3C(I)V, 2+2C(I)L, 2+3C(I)D), C(II) cycle(2C(II)V, 1C(II)L, 2C(II)D), C(III) cycle (1+lC(III)V, 1C(III)L), C(IV) cycle (1C(IV)V, 1C(IV)L) in cephalic region: A(I)(lA(I)V, l+2A(I)L, 1A(I)D), A(II)(1A(II)V, 1+3A(II)L, lA(II)D), A(III) {lA(III)V, l+lA(III)L, lA(III)D) and A(IV)(lA(IV)V, 2A(IV)L) in antacetabular region: 1M(I)V and 2M(I)L in median: 1+lP(I)L, 1P(II)L, lP(II)D lP(III)L, lP(IV)L and 1P(IV)D in postacetabular region: 2-2-2-2 in caudal region.

Journal Article↗
PubMed1989

[Cercarial shedding of Echinostoma cinetorchis and experimental infection of the cercariae to several kinds of snails].

The development of Echinostoma cinetorchis in several snail species reared in laboratory aquaria was observed. The eggs from adult flukes collected from the intestine of rats were cultivated to miracidia, and exposed to Hippeutis sp. snails. Observations were made for cercarial shedding from the exposed snails. The cercariae shed from the snails were again exposed to several species of fresh water snails in order to observe metacercarial formation in the snails and their infectivity to final hosts. The results obtained in this study were as follows: 1. Twenty miracidia were exposed to each snail of Hippeutis sp. About 58.3% of the above snails (7 out of 12) were dead before shedding the cercariae, and the remainder shed the cercariae for a period of 7 to 9 days before death. 2. Cercarial shedding from the infected snails started from the 25th day after the exposure to miracidia, and the total number of cercariae shed per snail was 684 in average (range; 482-904). 3. The size of rediae developed in the infected Hippeutis sp. snails was 1,242 x 214 microns in average, and the number of rediae per snail was 350 in average (range; 120-510). 4. About 40 to 50 cercariae shed from the Hippeutis sp. snails were each exposed to several species of snails reared in the laboratory. The metacercarial formation was confirmed by dissecting the infected snails, 12 to 16 days after the infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Laboratory and field evaluation of a direct filtration technique for recovery of schistosome cercariae.

The use of cercariometry in epidemiological studies has been limited by turbidity, difficulty of recovering cercariae at low concentrations in natural waters, and by complex apparatus that requires a power source. The technique of differential filtration developed by Theron has been modified and tested in the laboratory and in the field in Upper Egypt for detection of Schistosoma haematobium cercariae. A recovery filter with a pore size of 30 micrometer was found to give the best results. The recovery rate in the laboratory was 51% on filtration of 5-liter samples of formalin-treated water, and 19-30% with 10- and 20-liter samples. This moderate efficiency is offset by simplicity of the technique, rapid filtration, and ease of reading the recovery filter, permitting sampling of large volumes of water in the field by persons with little training. Average densities of 0.024 cercariae per liter of water were found at the Nile and 0.029 cercariae per liter in the irrigation canals. Most cercariae were recovered between 0.700 and 0900 hours.

Animals↗
PubMed2000

[Significance of schistosome lectins in the host allergic reaction evoked by penetration of cercaria].

Cercarial dermatitis is a skin allergic response caused by larval stages (cercariae) of the trematode family Schistosomatidae. In the Czech Republic the main causative agents of the disease are bird schistosomes of the genus Trichobilharzia. In the past it was supposed that cercariae of animal schistosomes die soon after the penetration into the human skin. However, we observed a migration and partial development of T. szidati cercariae within a nonspecific (mouse) host. The initial development of parasites in mice was similar to that observed in a specific host (duck) as well as to that described in human schistosomes causing schistosomiasis. After penetration, the transformation of T. szidati cercaria to schistosomulum is characterised by ultrastructural and biochemical changes, resulting in formation of a new parasite surface as well as in differences in specific binding of various lectins and host immunoglobulins to parasite surface components. It seems that the transformation of parasites represents a part of their immune evasion within the infected host. It was observed that T. szidati cercariae possess lectins localized on the parasite surface and in postacetabular penetration glands. It is supposed that, after the penetration into the skin, when glycocalyx disappears and gland material is expelled, the parasite surface may serve as an activator of the alternative complement pathway. The postacetabular gland components have probably a lytic function and facilitate migration of parasites through the skin. Moreover, the gland content is considered to play a role in shedding of surface antigens and in changes of parasite tegumental architecture.

Animals↗
PubMedDate not supplied

[Morphological peculiarities of schistosomatid cercariae of Trichobilharzia cf. ocellata group occuring in Moscow and Saint-Petersburg populations].

Morphology of schistosomatid cercariae of the genus Trichobilharzia (ocellata group) is described based on original and reference data. The material (Trichobilharzia cercariae) was collected in 1999-2000 from naturally 'infected snails Lymnaea stagnalis from Moscow and Saint-Petersburg megalopolises. The more accurate flame cell formula for these cercariae, as well as some aspects of chaetotaxy and eye morphology are given. The differences between cercariae from these regions were found. Based on a comparison of nef data with the reference data, it was found that the cercariae examined differ from those from the Central Europe.

Animals↗
PubMed2002

A survey of trematode cercariae in Bithynia goniomphalos in northeast Thailand.

A survey of trematode larvae in the fresh water snail, Bithynia goniomphalos in the main water reservoir of Huai Thalaeng district, Nakhon Ratchasima Province, Thailand, was conducted. The study site is in an area with a high prevalence of Opisthorchis viverrini infection. Malacological samplings were made during the year 2000 to study the prevalence and intensity of infection. Parasitological examinations of 527 live snails were performed at the Veterinary Parasitology Laboratory, Chulalongkorn University. Of the 527 snails, only 16 (3.04%) were found to be infected with cercariae. Of these 16 snails, 75% were infected with Amphistome cercariae, 6.25% with Armatae cercariae and 18.75% with Virgulate cercariae. Most infected snails (75%) had a density of infection of less than 100 cercariae/snail. No snail was infected with cercariae of Opisthorchis spp. This snail was, therefore, unlikely to be the intermediate host of Opisthorchis viverrini in the main water reservior of Huai Thalaeng district.

Animals↗
PubMed2005

Emergence of Opisthorchis viverrini cercariae from naturally infected Bithynia (Digoniostoma) siamensis goniomphalos.

Under natural conditions, the emergence of Opisthorchis viverrini cercariae from naturally infected Bithynia (Digoniostoma) siamensis goniomphalos showed diurnal periodicity, peaking between 8:00-10:00 AM. The cercariae did not emerge during darkness, but low-intensity light could induce a release. Cercariae shedded from each field infected B.(D.) s. goniomphalos was recorded daily. The maximum output from one snail was 1,728 cercariae in a day. The total cercarial output from all five infected snails was 56,555 and the maximum of total cercariae shed from one snail was 27,692. The field-infected B. (D.) s. goniomphalos could survive for 70 days after the snails were collected.

Animals↗
PubMed1991

Glycocalyx of bodies versus tails of Schistosoma mansoni cercariae. Lectin-binding, size, charge, and electron microscopic characterization.

Infection with Schistosoma mansoni is initiated by penetration of the intact skin of the mammalian host with the head but not the tail of the parasite cercariae. The surface of cercariae is covered by a 1-2-micron thick carbohydrate-rich glycocalyx (gx). Furthermore, the transformation of cercariae to schistosomula (the next parasitic stage in the mammalian host) is associated with loss of gx from the bodies. To understand the role of gx in the host-parasite relationship, we have characterized the gx of both bodies and tails of S. mansoni cercariae. A fluorescent fucose-specific lectin-stained bodies and not tails of the organism. Moreover, when an enriched preparation of gx obtained by extraction with 40% aqueous phenol and exclusion from Sepharose CL-6B was subjected to affinity chromatography on insolubilized Lotus lectin, which binds fucose-containing glycans, only body gx was retained. Body gx is smaller and less negatively charged than tail gx. Electron microscopy showed that gx from bodies and tails is composed of 25-40-nm particles and fibrillar material. Carbohydrate composition of gx of bodies and tails indicate that fucose and glucose are major components, respectively. beta-Elimination experiments indicate that the linkage sugar is N-acetylgalactosamine in both cases. Upon treatment with alkaline borohydride, nearly 90% of gx of both bodies and tails was recovered as two glycan chains: I and II (Mr approximately 10,500 and 5,600, respectively). Glycan I was in both cases more negatively charged than glycan II. Fucose is the predominant sugar in glycan I of the bodies while glycan I of tails is mainly composed of glucose. The gx was resistant to several proteases. This resistance and the abundance of carbohydrate in gx may be of biological importance for survival of cercariae. The substantial differences observed between the gx of bodies and tails may provide the basis for understanding the mechanism of selective release of body gx during transformation.

Animals↗
PubMed1990

[Life span and cercaria shedding of schistosome-infected snails in mountain region of Yunnan].

The life span and cercaria shedding of infected Oncomelania snails in a mountain region of Shitoudi village, Weishan County, Yunnan Province were observed in simulated local ecological environments. 135 infected snails were isolated for observation 3 months after exposure to miracidia in August, 1987. The snail survival rate from the day of initial cercaria shedding to next June, July, August and September was 27.4, 16.3, 13.3 and 11.9% respectively, and the average number of cercariae shed was 139.9, 29.6, 39.2 and 75 per month respectively. The average life span of infected snails was 171.6 days. The average number of cercariae shed per snail in its whole life was 673.0. It was estimated that the average patent period of infected snails was over half a year. As this is the first report in our country in respect to the life span and cercariae shedding of infected snails in a mountain region, the result might be useful for quantitative analysis of epidemiological factors of schistosomiasis in this kind of endemic areas as well as for formulation of control strategy.

Animals↗
PubMed1989

Isolation of microcercous cercariae from snails caught in an endemic focus of Paragonimus uterobilateralis in Liberia, West Africa.

Microcercous cercariae have been recovered from the snail Homorus (Striosubulina) striatella RANG. which were collected in a focus of human lung fluke disease in Liberia, West Africa, and are here described. Metacercariae of Paragonimus uterobilateralis were isolated from freshwater crabs (Liberonautes latidactylus) captured at the same location, and at the same time, as the infected snails. The dimensions of the Liberian cercariae have been found to differ markedly from those of a cercaria from Cameroon previously described as that of Paragonimus africanus. The structure and dimensions of the Liberian cercariae clearly resemble those of the cercariae of other species of Paragonimus from Asia and America.

Animals↗
PubMed1987

The host-parasite relationship between the Saudi Arabian Schistosoma mansoni and its intermediate and definitive hosts. 2. Effects of temperature, salinity and pH on the infection of mice by S. mansoni cercariae.

The infectivity of cercariae of the Saudi Arabian isolate of S. mansoni was found to be influenced by factors such as water temperature, salinity and pH. The optimum exposure temperature which resulted into the highest worm burdens and worm recovery rates in mice was 28 degrees C. However, the percentage infection rate was highest at a temperature range of 10 degrees to 34 degrees C. Mice were successfully infected with cercariae of S. mansoni at salinities of 0.5 to 6,400 mg/l. The highest worm burden and worm recovery rate occurred in mice infected by cercariae at a salinity of 100 mg/l, while the percentage infection rate was highest at a salinity range of 0.5 to 1,600 mg/l. Mice exposed to cercariae at the pH of 4.4 and 9.4 did not develop any infection. The percentage infection rate was highest in mice exposed to cercariae at a pH range of 6.4 to 8.4. However, both the worm burden and worm recovery rates were highest in mice at pH 5.4.

Analysis of Variance↗
PubMed1987

The host-parasite relationship between the Saudi Arabian Schistosoma mansoni and its intermediate and definitive hosts. 3. Effects of duration of exposure and cercarial concentration on the infection of mice by S. mansoni cercariae.

The percentage infection rate, worm burden and worm recovery rate in mice increased with an increase in the duration of exposure to cercariae. However, mice exposed to cercariae for 4 min had the same worm burden and worm recovery rates as those exposed for 16 min. Mice exposed to 80 and 160 cercariae each exhibited the highest percentage infection rates. The worm burden was highest in mice exposed to 160 cercariae each, while the worm recovery rate was highest in those exposed to 80 cercariae per mouse.

Analysis of Variance↗
PubMedDate not supplied

[Additional data on superficial argentophilic structures of the miracidium and cercaria of Fasciola gigantica (Cobbold, 1855) (Trematoda:Fasciolidae) and on the epidemiology of this parasite].

The life cycle of a senegalese strain of Fasciola gigantica was carried out in France from adults recovered in the liver of naturally infected cattle (Bos taurus). Laboratory-reared Lymnaea natalensis experimentally infected shed numerous cercariae. Metacercariae were used for successful infection of sheep. In the miracidium, variations are observed in the disposition of the medio-ventral epithelial cell of the second tier. The distribution of the superficial argentophilic structures is similar to that of the miracidium of F. hepatica. The chaetotaxy of the cercaria is very closely related to that of the cercaria of a strain of F. gigantica from Madagascar shed by Lymnaea hovarum but it differs clearly from that of the cercaria of F. hepatica. The encystment of a great number of cercariae (25 %) on the surface of water suggests that this is an important factor in the extension of the foci of contamination, and therefore increases greatly the risks of infection not only for animal but also for man. It is possible that human fascioliasis caused by F. gigantica is a disease, the importance of which is under-estimated.

Animals↗
PubMed1982

Schistosoma mansoni: is acquired immunity induced by highly x-irradiated cercariae dependent on the size of the challenging dose?

A high degree of immunity, as shown by a 91% reduction of the number of worms recovered was found in five groups of mice that were immunized five times with highly X-irradiated cercariae and then challenged with 10, 20, 50, 100, or 500 normal Schistosoma mansoni cercariae. The results indicated that there were no significant differences in worm reduction in immunized mice challenged with different numbers of cercariae; consequently the immunity induced by this immunization method did not appear to be challenge-dose-dependent. However, the results also showed that when immunized mice were challenged with 500, 100, 50, 20, and 10 cercariae, 0, 13, 26, 56, and 68%, respectively, of the experimental animals were free of worms. Thus, the percentage of worm-negative cases increased as the number of challenge cercariae decreased. When viewed in this manner, the acquired immunity may be considered challenge-dose-dependent as well. If this method of vaccination is used for schistosomiasis control, we may anticipate that in both hypo- and hyperendemic areas, the intensity of infection and the severity of the disease will be reduced owing to a reduction in worms burdens, and in hypoendemic areas, there will be a number of worm-free cases.

Animals↗
PubMed1994

A chemokinetic response in Schistosoma mansoni cercariae.

Schistosoma mansoni cercariae have been shown to aggregate in the presence of glass slides treated with clear nail varnish and linoleic acid. In choice chambers cercariae move toward the stimulant, but this behavior is not seen when linoleic acid is omitted. After 30-45 min, the cercariae were concentrated near the end of the choice-chamber containing the linoleic acid slide. When the cercariae were added in the center of the choice chamber, they formed a diffuse cloud that dispersed slowly in both directions in the absence of linoleic acid. Cercariae aggregating in the vicinity of a stimulant surface are not immediately stimulated to commence penetration; this appears to be time and dose related.

Animals↗
PubMed1993

Penetration of Schistosoma mansoni cercariae into a living skin equivalent.

We evaluated the use of a living skin equivalent (LSE) as a suitable membrane for Schistosoma mansoni cercarial penetration. LSE is a living artificial skin composed of a dermal layer containing human dermal fibroblasts embedded in a collagen lattice and an epidermal layer consisting of differentiated human keratinocytes. The keratinocytes differentiate into a stratum corneumlike layer, whereas the dermal-epidermal junction forms a layer similar, but not identical to, the basement membrane. We exposed LSE to 50 cercariae for 0, 3, 6, 20, and 30 hr at 37 C, and the percentage of penetration was evaluated by counting cercariae remaining on the LSE surface. No cercarial penetration was observed in the first 15 min of exposure; however, penetration was detected at all other times. Maximum penetration rates were observed at 20 hr (80%). In other experiments LSE was pretreated topically with 0 or 4 micrograms/cm2 linoleic acid, then exposed to between 800 and 1,000 cercariae for 18-20 hr at 37 C. LSE pretreated with linoleate had significantly higher penetration rates than untreated membranes (81% +/- 2.51% vs. 65.9% +/- 6.97%, P = 0.03). Increasing linoleate concentrations from 10 to 40 micrograms/cm2 gradually decreased the ability of cercariae to penetrate the membrane. Some LSE membranes also were processed for light microscopy, and we present photomicrographs showing schistosomulae within the epidermal and dermal layers of the LSE. We conclude that despite the time it takes for cercariae to penetrate LSE, these membranes may allow investigators to examine, in vitro, host-parasite interactions at the level of the skin.

Animals↗
PubMed1993

Toxicity of washing soaps to Schistosoma mansoni cercariae and effects of sublethal concentrations on infectivity in mice.

5 brands of washing powders and a brand of local soap made in Nigeria were tested for toxicity to cercariae of the Nigerian strain of S. mansoni. The tests revealed that all washing soaps were super-toxic to cercariae at high concentrations, with soap bars being comparatively less toxic. The detergents killed all cercariae instantly at 250-4000 ppm while soap bars achieved the same effect between 3000-4000 ppm. At lower concentration 25-100 ppm, the detergents required less than 60 min to kill 100% of the cercariae while soap bars required less than 12 h. The 12 hours LC 50 and LC 90 for Omo (detergent) and local soap were determined. Also the effects of sub-lethal concentrations 1.25-10 ppm on the infectivity of cercariae in mice were evaluated. These tests revealed that the treatment suppressed infectivity and that the degree of suppression increased with increase in the sub-lethal concentration, 85.4% at 10 ppm as compared to 42.8% at 1.25 ppm.

Animals↗