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PubMed1977

Stereoscan studies of cercariae, metacercariae, and adults of Cryptocotyle lingua (Creplin 1825) Fischoeder 1903 (Trematoda: Heterophyidae).

The cercaria of Cryptocotyle lingua has simple pointed spines all over the body. Four pointed modified spines occur dorsally in the mouth, and similar spines surround the openings of the penetration glands. The modified spines are shed shortly after penetration and encystment in the fish host. Less than a week after encystment, cytoplasmic folds develop all over the tegument. After about 4 weeks the cytoplasmic folds have disappeared and the spines are now flattened and serrated. The external surface of adults from herring gulls is very similar to that of mature metacercariae. It is provided with scalelike serrated spines which are especially well developed ventrally on the anterior end.

Animals↗
PubMed1982

Trematode infections in Pirenella conica in three sites of a mangrove lagoon in Sinai.

Over a period of 11 months, eight samples of Pirenella conica were taken at each of three sites of a mangrove lagoon in Sinai. Infection with larval trematodes, especially of Heterophyidae, was highest at the site within the mangrove thicket with a breeding colony of reef herons, the supposed definitive hosts of the Heterophyidae. The lowest frequency of infection was recorded from a tide-pool on the broad sand-flats surrounding the lagoon, where there was a great variation in the abundance of snails and xiphidiocercariae were more common than heterophyid cercariae. Predation from fish or other molluscs did not appear to be an important factor at either of these two sites. In all three sites, double infections of Heterophyidae and trematodes with xiphidiocercariae as well as of Heterophyidae and Echinostomatidae occurred less frequently than theoretically expected, but there was no competitive exclusion between Echinostomatidae and xiphidiocercariae.

Animals↗
PubMed2003

[Changes in the prevalence of intestinal parasites among Japanese expatriates in developing countries].

In order to study the prevalence of intestinal parasites among Japanese expatriates of developing countries, we conducted fecal specimen examinations annually from 1995 to 2000. Fecal specimens were collected from Japanese expatriates of each area: Asia, the Middle East, East Europe, Africa and Latin America. The specimens were fixed with 10% formalin in the local area, and then examined in Japan. We used the formalin-ether sedimentation method to find protozoan cysts or helminth eggs. In 1995, the infection ratio was 3.0% (N = 981), decreasing to 2.4% (N = 1,275) in 1996, 2.3% (N = 1,620) in 1997 and 1.6% (N = 1,574) in 1998. However, the ratio began to increase in 1999 (2.0%, N = 1,713) and 2000 (2.5%, N = 1,806). The ratio in Africa was the highest in each year, followed by Asia and Latin America. Heterophyidae (51 cases), Giardia lamblia (42) and Trichuris trichiura (30) were detected most frequently. In Egypt, the ratio of Heterophyidae rose by 28.8% in 2000. This was the prime reason for the increase in the overall ratio of infections worldwide. Most of the Japanese infected with Heterophyidae in Egypt had ingested dried mullet roe. This may explain the reason for the increase in the infection ratio there. Although the prevalence of intestinal parasites among Japanese expatriates in developing countries is decreasing, those who eat fish in these areas are still at risk. In order to eradicate intestinal parasitosis from this group, we must continue preventive measures such as health education.

Adult↗
PubMed2004

Food-borne intestinal trematodiases in humans.

Food-borne trematodiases still remain a public health problem world-wide, despite changes in eating habits, alterations in social and agricultural practices, health education, industrialization, environmental alteration, and broad-spectrum anthelmintics. Food-borne trematodiases usually occur focally, are still persistently endemic in some parts of the world, and are most prevalent in remote rural places among school-age children, low-wage earners, and women of child-bearing age. Intestinal fluke diseases are aggravated by socio-economic factors such as poverty, malnutrition, an explosively growing free-food market, a lack of sufficient food inspection and sanitation, other helminthiases, and declining economic conditions. Control programs implemented for food-borne zoonoses and sustained in endemic areas are not fully successful for intestinal food-borne trematodiases because of centuries-old traditions of eating raw or insufficiently cooked food, widespread zoonotic reservoirs, promiscuous defecation, and the use of "night soil" (human excrement collected from latrines) as fertilizer. This review examines food-borne intestinal trematodiases associated with species in families of the Digenea: Brachylaimidae, Diplostomidae, Echinostomatidae, Fasciolidae, Gastrodiscidae, Gymnophallidae, Heterophyidae, Lecithodendriidae, Microphallidae, Nanophyetidae, Paramphistomatidae, Plagiorchiidae, and Strigeidae. Because most of the implicated species are in the Echinostomatidae and Heterophyidae, emphasis in the review is placed on species in these families.

Animals↗
PubMed2003

Seasonal dynamics of the helminths of bluegill (Lepomis macrochirus) in a subtropical region.

Seasonal prevalence and abundance of the helminths of bluegill sunfish in a Louisiana oligohaline bayou were measured by a survey and a field "live-box" experiment. The survey took place from the spring of 1997 to the summer of 1998 and examined fish that were <7 cm. Three trematode species, Phagicola nana (Heterophyidae), Ascocotyle tenuicollis (Heterophyidae), and Posthodiplostomum minimum (Diplostomatidae), and 2 nematode species, Camallanus oxycephalus (Camallanidae) and Spinitectus carolini (Cystidicolidae), were examined. Camallanus oxycephalus was the only helminth that showed a distinct seasonal pattern. Abundance and prevalence peaked in summer, which was likely driven by concerted reproductive cycles of females. The survey data indicated that the other helminths fluctuated over time but did not seem to follow a distinct seasonal pattern. The fluctuations could be attributed to the variable nature of the habitat or to the stochastic events that influence transmission dynamics, particularly isolated events such as tropical storms, which cause dramatic changes in salinity. The live-box experiment successfully measured recruitment of A. tenauicollis and suggested a seasonal component of the distribution of this species, which was possibly caused by temperature-dependent emergence of cercariae from the snail intermediate host.

Animals↗
PubMed2002

A survey of metacercariae in cyprinoid fish in Nakhon Ratchasima, northeast Thailand.

Metacercariae were recovered from freshwater fish taken from a stream in Lum Cha Muak, Nakhon Ratchasima Province, northeast Thailand during the year 2000. Seventy-nine cyprinoid fish comprising 3 species (52 Puntius leiacanthus, 22 Cyclocheilichthys armatus, and 5 Hampla dispar) were collected. The prevalence of infection with metacercariae was 51.9%. Only two genera of metacercariae were found: Haplochinae spp and Heterophyidae spp. Haplochinae metacercariae were found in all 3 species of fish, giving rates of infection of 95.5%, 20% and 1.9% for Puntius leiacanthus, Cyclocheilichthys armatus and Hampla dispar respectively. Heterophyidae metacercariae were found only in Puntius leiacanthus, whose infection rate was 30.77%. There were fish intected at the rate of 3.8% with unclassified metacercariae. Interestingly, no fish infected with Opisthorchis viverrini metacercariae were found, which is at odds with previous reports from Thailand in which a higher infection rate was given. This is the first report of fish infected with Haplorchinae spp in Thailand.

Animals↗
PubMed1991

Intestinal fluke infections in Southeast Asia.

Twenty-three species of intestinal flukes reported in man in Southeast Asia are assigned to seven families: Echinostomatidae, Fasciolidae, Heterophyidae, Lecithodriidae, Microphallidae, Paramphistomatidae and Plagiorchiidae. The majority of species belongs to the Heterophyidae and Echinostomatidae families. Common species are Fasciolopsis buski, Echinostoma ilocanum, E. malayanum, E. revolutum and Haplorchis yokogawai. The countries where large number of species were reported are Thailand (14 species), Philippines (12 species), Indonesia (8 species) and Malaysia (4 species). Only one species was recognized in Laos, and Vietnam. Several species reported in man in the other regions, were reported in animals in Southeast Asia. It is possible that these are present in humans but have not yet been reported.

Animals↗
PubMed1985

Transmission experiments on the host specificity of Heterophyes species in 16 potential definitive hosts.

Sixteen different species of piscivorous mammals and birds were tried as experimental definitive hosts for Heterophyes heterophyes, H. aequalis and H. dispar. The hosts were classified in four categories, by fluke longevity, recovery and size, and the number of uterine eggs (embryonated/unembryonated): (1) Canidae and the cat were highly susceptible hosts for all three species of Heterophyes; (2) several mammals and herons showed a reduced susceptibility to infection (H. aequalis, 6 species; H. dispar, 1 species; H. heterophyes, 0 species); (3) In a group of hosts specific to each trematode, flukes were recovered up to 14 days post infection, but their uterine eggs did not become embryonated; (4) In a fourth category of hosts, chiefly Mustelidae, flukes could not be recovered. Taking also the literature into account it is concluded that man is a highly susceptible host for H. heterophyes, and that probably H. aequalis and H. dispar may reach reproductive maturity in humans also. The described wide host range of H. aequalis appears to be more typical for Heterophyidae than the comparably narrow host range of H. heterophyes.

Animals↗
PubMed2006

Rediae of echinostomatid and heterophyid trematodes suppress phagocytosis of haemocytes in Littorina littorea (Gastropoda: Prosobranchia).

A modulation of the phagocytic activity of hemocytes from the common periwinkle Littorina littorea by secretory-excretory products (SEP) released by trematode rediae during axenic in vitro cultivation was studied. The SEP released by the parasites Himasthla elongata (Echinostomatidae) and Cryptocotyle lingua (Heterophyidae) were found to inhibit the phagocytosis of zymozan particles by periwinkle hemocytes. The specificity of SEP effects was assessed: SEP of Himasthla militaris and Cryptocotyle concavum, two trematodes belonging to the same genera but infecting another closely related prosobranch snail Hydrobia ulvae, were also shown to be able to suppress L. littorea hemocytes phagocytic activity. However, no decrease in phagocytosis rate was observed when SEP of H. elongata and C. lingua were applied to monolayers of hemocytes from the bivalve mollusc Mytilus edulis. SEP from H. elongata was fractionated; only those fractions containing proteins of molecular weight more than 50 kDa were shown to possess inhibitory activity. Different H. elongata SEP concentrations were tested in for their ability to suppress phagocytosis by L. littorea hemocytes. Even very low SEP concentrations were shown to retain their ability to decrease phagocytosis rate, the inhibitory effect being dose-dependent. Hemocytes derived from snails naturally infected with H. elongata were also found to have lower phagocytic ability as compared to healthy individuals.

Animals↗
PubMed2006

Effects of trematode double infection on the shell size and distribution of snail hosts.

Infection with larval trematodes sometimes alters the phenotypes of their snail hosts. While some trematode species have distinct effects on host phenotypes, it is still unclear how snail phenotypes are altered when they are parasitized with multiple trematode species. Here, we report that double infection with trematode species averages the effects of parasitic alteration on host phenotype. We found that snail hosts Batillaria attramentaria (Batillariidae) infected with Cercaria batillariae (Heterophyidae) have abnormally large shells and distribute in lower areas of the intertidal zone. Snails with another dominant trematode species, the renicolid cercaria I (Renicolidae), have slightly larger shells and distribute in upper areas of the intertidal zone. A number of double infections with both trematodes was observed in this study. Snails infected with both trematode species exhibited an intermediate size and inhabited a depth between those of snails solely infected with either trematode species, suggesting that the two trematodes simultaneously affected the snail phenotypes. Because altered host phenotypes are frequently beneficial to parasites, two trematode species may compete for successful transmission through alteration of host phenotypes.

Animals↗
PubMed1993

Cryptocotyle lingua in mullet, Chelon labrosus; significance of metacercarial excretory proteins in the stimulation of the immune response.

'O' group mullet, Chelon labrosus, were experimentally infected with Cryptocotyle lingua (Heterophyidae) by tail dip in a suspension of cercariae. Metacercariae were excised after 1 and 24 hours and prepared for TEM and post-embedding immunogold labelling. Antisera to cercariae of C. lingua were raised in adult mullet by natural infection via the skin and by intra-peritoneal injection of sonicate. The membrane-bound vesicles within the syncytial lining of the metacercarial excretory vesicle were found to be intensely antigenic with both antisera; the epidermal secretory bodies type 5 within the cystogenous glands gave a positive response. Penetration gland contents were not found to be antigenic with either antiserum. Discharge of the membrane-bound vesicles coinciding with both the reorganization of the lining of the metacercarial excretory vesicle and with cyst wall formation appears to be of significance in the initiation of the host immune response. That the term 'excretory vesicle' in Digenea may be a misnomer is discussed in the light of current information regarding the wide range of functions attributed to this structure.

Animals↗
PubMed1998

Surface ultrastructure of juvenile and adult stages of Centrocestus armatus.

Centrocestus armatus (Trematoda: Heterophyidae) develops rapidly and produces eggs at 3 days postinfection in albino rats. Excysted metacercariae are pear-shaped and concave ventrally, with 42-44 peg-like circumoral spines. The entire body surface is densely covered with scale-like serrated spines. On juveniles, serration of the tegumental spines is greatest in the middle of the ventral and dorsal surfaces, and decreases anteriorly and posteriorly. Ciliated sensory papillae are concentrated around the oral sucker. Several nonciliated sensory papillae (type II papillae) occur equidistantly on the acetabulum and are arranged in a linear symmetry on the dorsal surface. On adults, the serration of the tegumental spines decreases to 14-17 tips on the ventrolateral surface. The high density of tegumental spines on posterior half of the body and the distribution of type II papillae on dorsal surface are considered to be characteristic of C. armatus.

Animals↗
PubMed2006

Parasites alter host phenotype and may create a new ecological niche for snail hosts.

By modifying the behaviour and morphology of hosts, parasites may strongly impact host individuals, populations and communities. We examined the effects of a common trematode parasite on its snail host, Batillaria cumingi (Batillariidae). This widespread snail is usually the most abundant invertebrate in salt marshes and mudflats of the northeastern coast of Asia. More than half (52.6%, n=1360) of the snails in our study were infected. We found that snails living in the lower intertidal zone were markedly larger and exhibited different shell morphology than those in the upper intertidal zone. The large morphotypes in the lower tidal zone were all infected by the trematode, Cercaria batillariae (Heterophyidae). We used a transplant experiment, a mark-and-recapture experiment and stable carbon isotope ratios to reveal that snails infected by the trematode move to the lower intertidal zone, resume growth after maturation and consume different resources. By simultaneously changing the morphology and behaviour of individual hosts, this parasite alters the demographics and potentially modifies resource use of the snail population. Since trematodes are common and often abundant in marine and freshwater habitats throughout the world, their effects potentially alter food webs in many systems.

Animals↗