Trematode Metacercariae Research Articles

The Biology of Echinostomes: From the Molecule To the Community

Bernard Fried and Rafael Toledo (Editors), Springer, New York, NY 10013, USA (Springer Science + Business Media LLC, 2009), 333 p, ISBN 978-0-387-09576-9. The Biology of Echinostomes: From the Molecule to the Community is comprised of 13 review articles. The first chapter (Chapter 1) provides a review of the most significant literature on the recent findings in echinostomatid systematics and life-cycles (by Esteban and Munoz-Antoli). The second chapter (Chapter 2) reviews the complex interactions in the first intermediate snail host, especially Biomphalaria-Echinostoma system and recent advances in their immunological and molecular interactions (by Coustau et al.). Chapter 3 is on the host-parasite dynamics in the second intermediate hosts: the biology of metacercariae (encystment, site selection, development and excystation), species of second intermediate hosts, behavioral and morphological changes of infected hosts, pathology of metacercariae in infected hosts and the effects of pesticides, herbicides, and marinades on the echinostome metacercariae (by Keeler and Huffman). Chapter 4 is on the establishment and development within the definitive hosts: host specificity and infectivity, excystment, habitat and distribution, growth and development, mating behavior, and fecundity of echinostomes in the definitive hosts (by Toledo). In Chapter 5, the studies on maintenance, cultivation, and excystation of echinostomes (on maintenance of life-cycles in the laboratory) were reviewed, studies of which were mainly carried out in Bernard Fried's laboratory from 1999 to 2007 (by Fried and Peoples). Chapter 6 is on some aspects of the biology of certain species of echinostomes in the wild and the experimental models developed with the purpose to gain a better understanding of the biology of this group of parasites (by Maldonado and Lanfredi). The following chapter, Chapter 7, treats the echinostomes infecting humans. It contains the valuable and wide-ranging information on the taxonomy, biology, epidemiology, pathology, symptomatology, diagnosis, treatment, prevention, and control of these food-borne trematode infections (by Chai). Chapter 8 reviews the literature on the pathology and immunology in animal host-parasite systems. This chapter provides useful information on the manifestations and mechanisms of resistance to infection, experimental strategies, and antigenic characterizations of echinostomes (by Toledo). In Chapter 9, genomic and proteomic studies are analyzed in detail to indicate advantages and pitfalls in the research using echinostome organisms. Despite the lack of a genome sequence project and the low number of sequences deposited in the databases, genomic studies have been preceded by some research groups, and their genomic data will deeply affect the future studies. The proteomic studies are focused on the excretory/secretory proteins and their role in host-parasite relationships (by Marcilla). Chapter 10 treats the chromatographic and atomic spectrometric methods used for the qualitative and quantitative analysis of organic and inorganic constituents of echinostomatid flukes and occasionally host tissues (by Sherma and Fried). Chapter 11 is a review of host-parasite interactions in nature associated with the emergence of Ribeiroia spp. (members of echinostome group in broader sense) and echinostome infections in the amphibian populations of North America. These trematode metacercariae provoke severe pathological changes, and are important cause of population decreasing in amphibians (by Johnson and McKenzie). Chapter 12 reviews host-parasite interactions in experimental rodent hosts with echinostomes, which are concurrently infected with heterologous species of Echinostoma and other helminths or protozoans (by Noland and Graczyk). Finally, Chapter 13 briefly reviews on the use of echinostomes in chemotherapeutic studies and provides a comprehensive overview of metabolic profiling using an Echinostoma caproni-mouse model (by Saric et al.). Comprehensively, this book provides the most recent information on echinostome researches, and widely covers from the basic biology to the application of novel techniques on the host-parasite interactions. Especially in the field of experimental parasitology, echinostomes will undoubtedly be an excellent experimental model because their life cycles are easily maintained in the laboratory. Therefore, this book will be very useful to obtain the valuable and wide-ranging information on experimental concepts, methodologies, and technologies for the study of helminths, in particular, echinostomes. It will also be useful for researchers of medical and veterinary fields.

Histological survey of symbionts and other conditions in razor clam Ensis arcuatus (Jeffreys, 1865) (Pharidae) of the coast of Galicia (NW Spain)

Symbionts and abnormal conditions of razor clam Ensis arcuatus were surveyed in three commercially important natural beds of Galician estuaries (NW Spain). Samples of 15–20 E. arcuatus were collected every 2 months from January 2003 until July 2004 and processed for histological examination. Prokaryote-like colonies, renal coccidians, gregarines, Trichodina sp. ciliates, haplosporidian-like plasmodia, turbelaria, trematode metacercariae, cestode-like larvae and basophilic inclusion bodies were observed in razor clam tissues without causing host damage. Bucephalid digenean sporocysts and germinoma were seen in some samples causing moderate or severe damage to the host depending on the intensity of infection and both could be a cause for concern if prevalence reached epizootic levels in Galician E. arcuatus populations. None of the parasites detected is OIE notifiable and, in general, the commercially exploited beds studied seem to be devoid of serious pathogens.

Occurrence of Ascocotyle ( Phagicola) longa Ransom, 1920 (Digenea: Heterophyidae) in Mugil incilis from Cartagena Bay, Colombia

Fishborne metacercariae have not been reported in Colombia. During an 8-month period, 250 mullet/lisa ( Mugil incilis) were examined for trematode metacercariae in the liver. Average prevalence and intensity were 93.4 ± 2.5% and 8476 ± 1238 cysts per gram of liver, respectively. Monthly prevalence of the trematode, identified as Ascocotyle ( Phagicola) longa Ransom (1920), was always high (>79%) and there was no difference between sampling periods ( P > 0.05). Trematode intensity in lisa had a significant negative effect on host size ( R = −0.325, P < 0.001), condition factor ( R = −0.352, P < 0.001), and liver-somatic index ( R = −0.372, P < 0.001); in contrast, a positive relationship was found with gill-somatic index ( R = 0.446, P < 0.001). Histopathological analysis indicated the presence of abundant cysts together with inflammatory reactions involving macrophage aggregates and necrosis. These results suggest that trematodes infecting the liver of M. incilis affect the growth and well-being of these fish, and their consumption could represent a major risk for human infection.

Survey for Fishborne Zoonotic Metacercariae in Farmed Grouper in Vietnam

Because of the common and growing practice of consuming raw grouper in Vietnam, the potential for transmission of zoonotic parasites is unclear. An investigation of the prevalence of zoonotic parasites in cage-reared grouper (Epinephelus coioides and Epinephelus bleekeri) from marine waters of Cat Ba Island, Hai Phong city, Northern Vietnam, revealed the presence of two zoonotic trematode metacercariae species, Procerovum varium and Heterophysopsis continua. The identity of the metacercariae was confirmed from adult flukes recovered from mice experimentally inoculated with metacercariae. The prevalence of zoonotic parasites in 40 E. coioides was 10.0% and 1.2% in 172 E. bleekeri. Since little is known of their ecology and epidemiology, further investigation of these zoonotic parasites is needed to develop prevention guidelines.

Effects of Climate Variability on Interannual Variation in Parasites, Pathologies, and Physiological Attributes of Bivalves from the U.S. East, Gulf, and West Coasts

We analyzed weighted prevalence of various parasites and pathologies for 1995 to 2006 along with a set of physiological variables to determine the degree of concordancy in their interannual variations over 500-km stretches of coastline using data from the National Oceanic and Atmospheric Administration's (NOAA's) National Status and Trends “Mussel Watch” Program. The variables examined in mytilid mussels fell into three groups based on the temporal patterns observed: ceroid bodies, taxon richness, digestive tubule atrophy, and major pathologies varied concordantly along the Northeast and West Coasts. For reproductive stage, sex ratio, and gill ciliates, concordant temporal trends were limited to the northeast coast. Gregarines, found only in West coast mussels, behaved similarly to those variables falling into the first group. A final group, trematode metacercariae and sporocysts, tissue pathologies, and the prokaryotes, was characterized by limited concordancy. For oysters, a similar triplet of groups wa...

Modeling Stream Network‐Scale Variation in Coho Salmon Overwinter Survival and Smolt Size

AbstractWe used multiple regression and hierarchical mixed‐effects models to examine spatial patterns of overwinter survival and size at smolting in juvenile coho salmon Oncorhynchus kisutch in relation to habitat attributes across an extensive stream network in southwestern Oregon over 3 years. Contributing basin area explained the majority of spatial variation (R2 = 0.57‐0.63) in coho salmon overwinter survival (range = 0.02‐0.63), with highest survival rates observed in smaller headwater and intermittent streams. Other habitat attributes, including proportional pool area, percent exposed bedrock substrate, percent broadleaf canopy cover, and adult salmon carcass density, were relatively poor predictors of survival. Indices of individual fish condition, including fall parr fork length, condition factor, and parasite infestation rates, were also relatively uninformative in coho salmon overwinter survival models. Coho salmon smolt length was primarily a function of length at the time of fall tagging, but stream type, contributing basin area (positive effect), thermal history (positive effect), and black spot infestation (i.e., trematode metacercariae; negative effect) were also important. The consistent, broad spatial gradients in overwinter survival observed in this study can help guide efforts designed to enhance coho salmon production in coastal streams and suggest that habitat protection, restoration, and enhancement strategies will be best guided by a whole‐basin context.

Hypersymbioses in the pinnotherid crabs (Decapoda: Brachyura: Pinnotheridae): a review

Members of the brachyuran family Pinnotheridae are nearly all symbionts of other invertebrates; some crabs are parasitic and others are commensal. Most live inside bivalve molluscs or in the tubes or burrows of polychaetes and other marine organisms. Animals living on or in pinnotherid crabs are considered to be hypersymbiotic and are reviewed here. Hypersymbionts are poorly represented within only 26 members (∼8.6%) of the Pinnotheridae (20 species in the subfamily Pinnotherinae and six species in the Pinnothereliinae). Parasitic hypersymbionts are as follows: three species of fungi; one cestode larva (undescribed procercoid of Trypanorhynchida); one trematode metacercaria (undescribed Microphallidae); nematode cysts (undescribed); three species of Nemertea (Carcinonemertidae, two undescribed); two species of rhizocephalan Cirripedia (Sacculinidae; plus five or more undescribed potential sacculinid species); epicaridean Isopoda [13 species of Bopyridae (one undescribed) and four species of entoniscids (Entoniscidae, three undescribed)]. Preliminary biological information on undescribed entoniscids is presented. Several mainly incidental hypersymbioses involving ectosymbionts are known primarily from Pinnixa chaetopterana, a symbiont of polychaete burrows. The ctenostome bryozoan Triticella elongata is the only known obligate ectosymbiont in P. chaetopterana, but it also infests five other species of pinnotherids. Some of the other ectosymbionts (all incidental) on P. chaetopterana are stalked ciliates, hydroids, juvenile polychaetes, bivalve molluscs, balanomorph barnacles, harpacticoid copepods and urochordates. Species of ectosymbionts including an ectoproct bryozoan have been reported from other pinnotherid species. Factors influencing our meagre knowledge of hypersymbioses in the Pinnotheridae are discussed, among them the inaccessibility of crab hosts and research emphasis on taxonomy within the family.

Echinostoma hortense and Heterophyid Metacercariae Encysted in Yellowfin Goby, Acanthogobius flavimanus, from Shinan-gun and Muan-gun (Jeollanam-do), Korea

Fishborne trematode (FBT) metacercariae were investigated in yellowfin goby, Acanthogobius flavimanus, collected from Shinan-gun and Muan-gun, Jeollanam-do (province), Korea. All collected fishes were examined using the artificial digestion method. In all of 15 gobies from Aphae-myeon in Shinan-gun, metacercariae of Stictodora spp. (334 metacercariae/fish), Heterophyes nocens (153/fish), and Heterophyopsis continua (20/fish) were detected. In 2 of 14 gobies from Jido-myeon in Shinan-gun, 8 Echinostoma hortense metacercariae in total were detected. In 15 gobies from Haeje-myeon in Muan-gun, the metacercariae of H. continua were found in 100%, Stictodora spp. in 86.7%, and H. nocens in 6.7% of fish examined. The average numbers of metacercariae per infected fish were 23.3 (H. continua), 416.0 (Stictodora spp.), and 2.0 (H. nocens), respectively. The metacercariae of E. hortense found in gobies were elliptical, with 150 x 138 microm in average size, and had 27 collar spines on the head crown. The above results suggest that yellowfin gobies from 2 localities may be the potential infection sources of FBT. Moreover, it is proved for the first time that the yellowfin goby, A. flavimanus, acts as a second intermediate host for E. hortense.

Fishborne Trematode Metacercariae in Freshwater Fish from Guangxi Zhuang Autonomous Region, China

A survey was performed to investigate the infection status of fishborne trematode (FBT) metacercariae in freshwater fish from Guangxi Zhuang Autonomous Region, China. A total of 307 freshwater fish of 31 species were collected from 5 administrative regions of Guangxi Zhuang Autonomous Region. They were examined by artificial digestion method from July 2003 to August 2004. No metacercariae were detected in fish from Fusui-xian. In fish from Mashan-xian and a market in Nanning, 3 species of metacercariae, Haplorchis taichui, Haplorchis pumilio, and Centrocestus formosanus, were mainly detected. Metacercariae (8 in number) of Clonorchis sinensis were found in 1 Chanodichthys dabryi purchased from a market in Nanning. In fish from Yangshuo, Metagonimus yokogawai metacercariae were detected from all 18 fish species examined. Total 13 C. sinensis metacercariae were found in 3 out of 10 Hemibarbus maculatus from Yangshuo. All 7 Zacco platypus from Yangshuo were infected with 8-112 Echinochasmus perfoliatus metacercariae. In fish from Binyang-xian, H. pumilo metacercariae were mainly detected in all 5 fish species examined, and only 1 metacercaria of C. sinensis was found in a Hemiculter leucisculus. From the above results, it was confirmed that some species of freshwater fish play a role of second intermediate hosts for FBT in Guangxi Zhuang Autonomous Region, China. In particular, 4 species of intestinal flukes, M. yokogawai, H. taichui, H. pumilio, and C. formosanus, were prevalent in fish hosts, whereas C. sinensis metacercariae were detected only in 3 fish species.

The influence of climatic conditions on long-term changes in the helminth fauna of terrestrial molluscs and the implications for parasite transmission in southern England

The influence of climatic conditions on the prevalence and transmission of helminth parasites in a terrestrial mollusc population was studied in a grassland site in southern England between 1974 and 1983. Molluscs were sampled in each September of 5 years over this period (1974, 1976, 1979, 1981, 1983). Climatic conditions had a variable effect on parasite prevalence. Trematode sporocyst infections increased after wet summer and warm winter conditions and declined in hot, dry periods. Cestode infections increased after combined wet spring and summer weather and low winter temperatures, although trematode metacercariae and nematode infections were less likely to be influenced by climate. The effects on parasite transmission were undertaken by comparing parasite prevalences in the principal definitive hosts, the common shrew (Sorex araneus) and the wood mouse (Apodemus sylvaticus) in the same habitat over the period 1973-1983. Changes in parasite prevalences in the molluscan population were rarely replicated by changes in the small mammal population, except for trematode parasites in small mammals during a period of severe drought in 1976. These results suggest that only long-term persistent modifications in climate are likely to affect host-parasite dynamics.

Size-dependent pattern of metacercariae accumulation in Macomona liliana: the threshold for infection in a dead-end host

While bivalves can acquire trematode metacercariae over their lifetime, the rate at which this accumulation takes place is not necessarily linear. The present study found that the bivalve Macomona liliana acquires very few or no metacercariae until it reaches 30 mm in size, but thereafter the rate at which it becomes infected increases exponentially. It is likely that this ontogenetic change in infection rate is associated with the increased filtration capacity and siphon diameter of larger M. liliana. The echinostome metacercariae that infect M. liliana also infect a much more common sympatric bivalve, Austrovenus stutchburyi, in which they achieve much higher infection intensity. Due to its deeper burying depth, M. liliana most likely represents a dead-end host for the echinostomes: potential definitive hosts preferentially feed upon A. stutchburyi as they are located closer to the sediment surface than M. liliana. However, due to the low infection intensity and population density of M. liliana, its overall impact as a sink for echinostome populations in the ecosystem is probably negligible.

Ten polymorphic microsatellite loci for the trematode Curtuteria australis (Echinostomatidae)

Ten polymorphic loci were isolated and characterised from the intertidal New Zealand trematode Curtuteria australis. This common parasite manipulates the burrowing behaviour of its abundant bivalve host Austrovenus stutchburyi, with cascading impacts on the biodiversity of intertidal communities. Observed heterozygosities of the 10 loci ranged from 0.500 to 0.905, and three to 14 alleles were detected in 24 trematode metacercariae. These loci are currently being used to investigate the molecular ecology of this species within its intermediate hosts.

Pathology survey of the short-neck clam Ruditapes philippinarum occurring on sandy tidal flats along the coast of Ariake Bay, Kyushu, Japan

The pathological condition of the short-neck clam Ruditapes philippinarum was surveyed along the coast of Kumamoto, Japan, in June 2004. DNA sequences of the non-transcribed spacer region and internal transcribed spacer region flanking 5.8S rRNA identified Perkinsus olseni among the clams. Ray’s fluid thioglycollate medium assay indicated that 96.7% of the clams surveyed from the Kiguchi River tidal flat (native clams, Stn KR-N) and 96.7% of the clams surveyed from the Midori River tidal flat (Stn MR) were infected with P. olseni with an infection intensity of 464,278 and 199,937 Perkinsus cells/gram tissue wet weight (gWW), respectively. In contrast, 66.7% of the clams imported from China and stored along the Kiguchi River tidal flat (Stn KR-I) and 20.2% of clams from the Arao tidal flat (Stn AT) were infected with P. olseni with an infection intensity of 37,547 and 3382 Perkinsus cells/gWW, respectively. Brown ring disease was detected in the clam population from Stn KR-I at a prevalence of 90.0%. Polymerase chain reaction and the 16S rRNA sequence suggested that the agents of brown ring disease observed at Stn KR-I were Vibrio tapetis-like bacteria. Sporocysts and metacercariae of unidentified trematodes were also observed in the gonads and mantle of the clams from Stn KR-I, Stn MR, and Stn AT, at prevalences of 7.1–42.9%. Metacestodes (larval tapeworms) were found in the foot and digestive gland at a prevalence of 52.5%, 30.0%, and 14.3% in clams from Stns MR, AT, and KR-N, respectively. Histology also showed massive hemocyte infiltration and inflammation among clams heavily infected with P. olseni. Castration of the follicle was typical among clams infected with the trematode. The data indicate that most of the clams along the coast of Kumamoto are infected with various pathogens at various rates of infection, and these pathogens could have negative effects on the clam population in the long term.

Prevalence of Zoonotic Trematodes in Fish from a Vietnamese Fish-Farming Community

The prevalence of fish-borne zoonotic trematode (FZT) metacercariae was investigated in fish farmed by rural households in Nghe An Province, located in northern Vietnam. In total, 716 fish, including tilapia (Oreochromis niloticus) and 6 carp species, i.e., grass carp (Ctenopharyngodon idellus), bighead carp (Aristichthys nobilis), mrigal (Cirrhinus mrigala), common carp (Cyprinus carpio), silver carp (Hypophthalmychthys molitrix), and roha (Labeo rohita), collected from 53 fish farms were examined. The overall prevalence of FZT metacercariae was 44.6%, ranging from 12.5% to 61.0% in fish species collected from grow-out ponds, which are the production system for growing fish from fingerling size to market size. The overall prevalence was 43.6% in fingerlings cultured in nurseries, ranging from 7.4% to 62.8% for different fish species. The FZT species recovered were heterophyids and echinostomatids and included Haplorchis pumilio, H. taichui, H. yokogawai, Centrocestus formosanus, Stellantchas musfalcatus, and Echinochasmus japonicus, all of which are intestinal flukes in humans, other mammals, and birds. This is the first report of H. yokogawai and E. japonicus in fish in Vietnam, and the first record for S. falcatus in northern Vietnam. Although a previous cross-sectional survey of the people living in these fish farm households revealed a very low prevalence of FZTs (< 1%), our results demonstrate that intestinal flukes are common in farmed fish in this area, suggesting that reservoir hosts such as dogs, cats, and pigs are more important in sustaining the life cycles of these flukes in fish farms than human hosts. This has implications for the effectiveness of control programs focused mainly on treatment of humans.

Larval trematodes (Digenea) of planorbid snails (Gastropoda: Pulmonata) in Central Europe: a survey of species and key to their identification

A survey of the larval stages (cercariae and metacercariae) of trematodes (Digenea) found in planorbid snails in Central Europe (Austria, Czech Republic, south-east Germany, Hungary, Poland and the Slovak Republic) is presented based on a study of 7,628 snails of 12 species examined between 1998-2006. A total of 34 trematode larval stages, comprising cercariae of 28 species and metacercariae of seven species (one species occurred both as cercaria and metacercaria) of nine families were found in 898 (11.5%) snails of eight species. The dominant cercariae were those belonging to the Rubenstrema exasperatum (Rudolphi, 1819)/Neoglyphe locellus (Kossack, 1910) species complex, Tylodelphys excavata (Rudolphi, 1803) and Echinostoma spiniferum (La Valette, 1855) sensu Nasincová (1992), all from Planorbarius corneus (Linnaeus). Almost the same spectrum of cercariae of the families Echinostomatidae, Plagiorchiidae and Omphalometridae was found in the present study as in previous reports; however, a considerably lower spectrum of cercariae of the families Diplostomidae and Strigeidae was recorded. The most frequent metacercariae were those of Echinoparyphium aconiatum Dietz, 1909, Neoglyphe locellus and Moliniella anceps (Molin, 1859), all occurring mainly in P. corneus. The most heavily infected snail species was P. corneus, followed by Planorbis planorbis (Linnaeus) and Segmentina nitida (Müller). The widest spectrum of trematode species was found in P. planorbis and P. corneus. Forty-two cercariae identified to the species level belonging to 15 families, plus an additional 43 taxa recorded under generic or provisional names, were reported from 11 species of planorbids in previous studies carried out in Central Europe. However, the actual number of trematode species occurring in the planorbid snails is probably much lower, because many, if not most, larval stages reported under provisional names or unidentified to the species level may be conspecific with identified adult forms. A key to the cercariae and metacercariae recorded from planorbids in Central Europe, together with illustrations of those species encountered most frequently in the field, is provided to facilitate identification.

Fishborne Trematode Metacercariae Detected in Freshwater Fish from Vientiane Municipality and Savannakhet Province, Lao PDR

Freshwater fish from Vientiane Municipality and Savannakhet Province, Lao PDR were examined by the muscle compression and artificial digestion methods to know the infection status with trematode metacercariae. In the fish from Savannakhet, 2 species of metacercariae, Opisthorchis viverrini and Haplorchis taichui, were detected. O. viverrini metacercariae were found in 6 species of fish, Puntius brevis, Hampala dispar, Esomus metallicus, Mystacoleucus marginatus, Puntioplites falcifer, and Cyclocheilichthys armatus. H. taichui metacercariae were detected in 3 species of fish, P. brevis, P. falcifer, and M. marginatus. In the fish from Vientiane, 4 species of metacercariae, O. viverrini, H. taichui, Haplorchis yokogawai, and Centrocestus formosanus, were detected. Among them, O. viverrini metacercariae were found in 7 species of fish, Onychostoma elongatum, C. armatus, H. dispar, P. brevis, Cyclocheilichthys repasson, Osteochilus hasseltii, and Hypsibarbus lagleri. The metacercariae of H. taichui were detected in 6 species of fish, C. repasson, O. elongatum, C. armatus, H. dispar, Labiobarbus leptocheila, and Cirrhinus molitorella. The metacercariae of H. yokogawai were found in 9 species of fish, C. repasson, O. elongatum, C. armatus, H. dispar, Labiobarbus leptocheila, O. hasseltii. C. molitorella, Hypsibarbus wetmorei, and H. lagleri. The metacercariae of C. formosanus were detected in 4 species of fish, C. repasson, P. brevis, O. hasseltii, and C. molitorella. From these results, it is confirmed that fishborne trematode metacercariae, i.e. O. viverrini, H. taichui, H. yokogawai and C. formosanus, are prevalent in various species of freshwater fish from Savannakhet Province and Vientiane Municipality, Lao PDR.

Prevalence of Haplorchis taichui and Haplorchoides sp. Metacercariae in Freshwater Fish from Water Reservoirs, Chiang Mai, Thailand

A parasitological investigation on trematode metacercariae was made on 62 freshwater fishes of 13 species in northern Thailand; Cyclocheilichthys apogon, Puntioplites proctozysron, Labiobarbus siamensis, Barbodes gonionotus, Barbodes altus, Henicorhynchus siamensis, Osteochilus hasselti, Notopterus notopterus, Mystacoleucus marginatus, Anabas testudineus, Systomus orphoides, Morulius chrysophykadian, and Hampala macrolepidota. The fish were caught over the summer period (February-May 2007) from 2 Chiang Mai water reservoirs, i.e., the Mae Ngad (UTM 47Q E 503200, 47Q N 2119300) and the Mae Kuang Udomtara (UTM 47Q E 513000, 47Q N 2092600) Reservoirs in Chiang Mai province, Thailand. The prevalence of heterophyid (Haplorchis taichui and Haplorchoides sp.) metacercariae in these fish was 83.9% and 74.2% in the Mae Ngad and Mae Kuang Udomtara Reservoirs, respectively. The highest intensity of heterophyid metacercariae in H. siamensis in the Mae Ngad was 120.4 and that in P. proctozysron in the Mae Kuang Udomtara was 180.0. The fish, A. testudineus, C. apogon, and M. chrysophykadian, were not found to be infected with H. taichui metacercariae. The results show that the freshwater fish in Chiang Mai water reservoirs are heavily infected with H. taichui and Haplorchoides sp. metacercariae.

Prevalence of Zoonotic Metacercariae in Two Species of Grouper, Epinephelus coioides and Epinephelus bleekeri, and Flathead Mullet, Mugil cephalus, in Vietnam

Fishborne zoonotic metacercariae have not been reported from brackish water and marine fish from Vietnam waters although these parasites are common in the country's freshwater fish. Both wild-caught and cultured grouper (Epinephelus coioides and Epinephelus bleekeri), and mullet (Mugil cephalus) from brackish and marine waters located in Khanh Hoa province in central coastal Vietnam were examined, and found positive for zoonotic trematode metacercariae. From grouper, Heterophyopsis continua and Procerovum varium were recovered. The prevalence of H. continua ranged from 2.0 to 6.0% and that for P. varium ranged from 11.6 to 15.8%. Mullet were infected with Pygidiopsis summa and H. continua both of these species are new records for Vietnam. The prevalence of P. summa in mullet was generally high, ranging from 17.6 to 75.5%, and was significantly higher than the prevalence of H. continua (2.5 to 32.4%). There were no significant differences in the prevalence of metacercariae between grouper from natural or cultured habitats, indicating that the highest risk of infection occurs in the wild-caught state prior to their placement in culture. Further, there was no difference in metacercarial prevalence between the 2 species of grouper. Infected wild-caught seed were only observed from January to October. Monthly variation in prevalence suggests seasonal variation in mullet infections occurs in this region with the highest transmission taking place from October to December. Basic investigations on the ecology and epidemiology of these intestinal flukes need to be carried out to determine their significance as a public health problem and the aspects of their biology that may be vulnerable to control interventions.

Increased abundance of snails and trematode parasites of Fundulus heteroclitus (L.) in restored New Jersey wetlands

The Hackensack Meadowlands District is a large heavily degraded, brackish marsh system in the urbanized northeastern region of New Jersey, USA. Six study sites were used, three of which were restored (Mill Creek, Skeetkill Creek and Vince Lombardi), and three others were unrestored (Richard DeKorte Park, Cedar Creek and Kingsland Creek). Highly significant differences were found with respect to snail abundance and gill parasite abundance. In the three restored sites, significantly more Littoridinops tenuipes were found, and Fundulus heteroclitus had significantly more digenean trematode metacercariae gill infections than at unrestored sites. As habitat quality improves following restoration, the number of suitable digenean trematode parasite hosts multiplies as substrate for benthic invertebrates (first intermediate host) increases and usage by other species, such as Fundulus spp. (second intermediate host), is encouraged, which then attracts more wading birds (definitive host). Though the restoration process enhances trophic complexity, including primary consumers (gastropods), secondary consumers (fish) and tertiary consumers (wading birds), and ultimately parasite diversity, restoration also helps facilitate parasite life cycles.

Relationship of parasites and pathologies to contaminant body burden in sentinel bivalves: NOAA Status and Trends ‘Mussel Watch’ Program

The 1995-1998 database from NOAA's National Status and Trends 'Mussel Watch' Program was used to compare the distributional patterns of parasites and pathologies with contaminant body burdens. Principal components analysis (PCA) resolved five groups of contaminants in both mussels and oysters: one dominated by polycyclic aromatic hydrocarbons (PAHs), one dominated by pesticides, and three dominated by metals. Metals produced a much more complex picture of spatial trends in body burden than did either the pesticides or PAHs. Contrasted to the relative simplicity of the contaminant groupings, PCA exposed a suite of parasite/pathology groups with few similarities between the sentinel bivalve taxa. Thus, the relationship between parasites/pathologies and contaminants differs significantly between taxa despite the similarity in contaminant pattern. Moreover, the combined effects of many contaminants and parasites may be important, leading to complex biological-contaminant interactions with synergies both of biological and chemical origin. Overall, correlations between parasites/pathologies and contaminants were more frequent with metals, frequent with pesticides, and less frequent with PAHs in mussels. In oysters, correlations with pesticides and metals were about equally frequent, but correlations with PAHs were still rare. In mytilids, correlations with metals predominated. Negative and positive correlations with metals occurred with about the same frequency in both taxa. The majority of correlations with pesticides were negative in oysters; not so for mytilids. Of the many significant correlations involving parasites, few involved single-celled eukaryotes or prokaryotes. The vast majority involved multi-cellular eukaryotes and nearly all of them either cestodes, trematode sporocysts, or trematode metacercariae. The few correlations for single-celled parasites all involved proliferating protozoa or protozoa reaching high body burdens through transmission. The tendency for the larger or more numerous parasites to be involved suggests that unequal sequestration of contaminates between host and parasite tissue is a potential mediator. An alternative is that contaminants differentially affect parasites and their hosts by varying host susceptibility or parasite survival.