Molecular detection of Aphanomyces astaci - An improved species specific qPCR assay

The parasitic oomycete Aphanomyces astaci is the causative agent of crayfish plague, a devastating disease for European freshwater crayfish. Species specific quantitative real-time PCR (qPCR) can offer rapid detection of the pathogen. However, the well established A. astaci qPCR assay recommended by the World Organization for Animal Health (WOAH) amplifies the recently described Aphanomyces fennicus. Consequently, false-positive results may occur. This calls for the improvement of the established species specific A. astaci qPCR assay in order to avoid amplifying A. fennicus while screening for A. astaci. We developed an improved species specific A. astaci qPCR assay and validated the assay across three laboratories, using established procedures including different qPCR master mixes for each respective laboratory. Genomic DNA from A. astaci, A. fennicus and closely related Aphanomyces spp. was analysed and compared with both the improved and established assay. Additionally, DNA from crayfish tissue and environmental samples were analysed with both assays. The improved assay showed similar sensitivity with the established assay for all sample types, while proving highly specific for A. astaci avoiding amplification of A. fennicus and the other tested Aphanomyces spp. Environmental DNA (eDNA) samples collected at River Lierelva in Norway amplified with the established assay, but not with the improved assay indicating false positive. We were able to sequence a 530 bp fragment of the ITS region from these eDNA samples and the consensus sequence showed 99.9-100 % pairwise identity with A. fennicus and 97.2-98 % pairwise identity with A. astaci, suggesting that the occurrence of A. fennicus is not limited to Finland, where it was first discovered.

A Comprehensive Review on Crustaceans' Immune System With a Focus on Freshwater Crayfish in Relation to Crayfish Plague Disease

Freshwater crayfish immunity has received great attention due to the need for urgent conservation. This concern has increased the understanding of the cellular and humoral defense systems, although the regulatory mechanisms involved in these processes need updating. There are, however, aspects of the immune response that require clarification and integration. The particular issues addressed in this review include an overall description of the oomycete Aphanomyces astaci, the causative agent of the pandemic plague disease, which affects freshwater crayfish, and an overview of crustaceans' immunity with a focus on freshwater crayfish. It includes a classification system of hemocyte sub-types, the molecular factors involved in hematopoiesis and the differential role of the hemocyte subpopulations in cell-mediated responses, including hemocyte infiltration, inflammation, encapsulation and the link with the extracellular trap cell death pathway (ETosis). In addition, other topics discussed include the identity and functions of hyaline cells, the generation of neoplasia, and the emerging topic of the role of sessile hemocytes in peripheral immunity. Finally, attention is paid to the molecular execution of the immune response, from recognition by the pattern recognition receptors (PRRs), the role of the signaling network in propagating and maintaining the immune signals, to the effector elements such as the putative function of the Down syndrome adhesion molecules (Dscam) in innate immune memory.

Recovery of Hafnia alvei from diseased brown trout, Salmo trutta L., and healthy noble crayfish, Astacus astacus (L.), in Bulgaria

Hafnia alvei was isolated in Bulgaria from healthy noble crayfish, Astacus astacus (L.), and then from farmed diseased brown trout, Salmo trutta L., with signs of haemorrhagic septicaemia. The isolates were identified initially with conventional phenotyping and commercial Merlin Micronaut and API 20E rapid identification systems, followed by sequencing of the 16S rRNA gene. Hafnia alvei Bt1, Bt2 and Aa4 were of low virulence to rainbow trout and brown trout, although cytotoxicity was demonstrated by Bt1 and Bt2, but not by Aa4.

Prevalence of the crayfish plague pathogen Aphanomyces astaci in populations of the signal crayfish Pacifastacus leniusculus in France: evaluating the threat to native crayfish

Aphanomyces astaci, the crayfish plague pathogen, first appeared in Europe in the mid-19^th century and is still responsible for mass mortalities of native European crayfish. The spread of this parasite across the continent is especially facilitated by invasive North American crayfish species that serve as its reservoir. In France, multiple cases of native crayfish mortalities have been suggested to be connected with the presence of the signal crayfish Pacifastacus leniusculus, which is highly abundant in the country. It shares similar habitats as the native white-clawed crayfish Austropotamobius pallipes and, when infected, the signal crayfish might therefore easily transmit the pathogen to the native species. We investigated the prevalence of A. astaci in French signal crayfish populations to evaluate the danger they represent to local populations of native crayfish. Over 500 individuals of Pacifastacus leniusculus from 45 French populations were analysed, plus several additional individuals of other non-indigenous crayfish species Orconectes limosus, O. immunis and Procambarus clarkii. Altogether, 20% of analysed signal crayfish tested positive for Aphanomyces astaci, and the pathogen was detected in more than half of the studied populations. Local prevalence varied significantly, ranging from 0% up to 80%, but wide confidence intervals suggest that the number of populations infected by A. astaci may be even higher than our results show. Analysis of several individuals of other introduced species revealed infections among two of these, O. immunis and P. clarkii. Our results confirm that the widespread signal crayfish serves as a key reservoir of Aphanomyces astaci in France and therefore represents a serious danger to native crayfish species, especially the white-clawed crayfish. The prevalence in other non-indigenous crayfish should also be investigated as they likely contribute to pathogen transmission in the country.

Self-limiting outbreak of crayfish plague in an Austropotamobius pallipes population of a river basin in the Abruzzi region (central Italy)

Crayfish plague, caused by the oomycete Aphanomyces astaci, is a serious disease of European freshwater crayfish and has eliminated entire populations in several European countries. In September 2011, mortality was observed among the Austropotamobius pallipes population of a river basin in the Abruzzi region (central Italy), and A. astaci DNA was detected by PCR in dead crayfish. A systematic survey was carried out to evaluate the spread and the effects of the plague in the river basin. The source of the outbreak remained unknown since North American crayfish species, which frequently act as subclinical carriers of the infection, were not detected in the area. The A. pallipes population disappeared from a river stretch of ~1 km, where A. astaci infection was detected in dead crayfish. However, apparently unaffected crayfish were still present upstream of that area as well as in a tributary that joined the brook in the apparently depopulated stretch. A. astaci infection was not detected in dead individuals collected in the upstream area and tributary. A follow-up visit conducted in the following season showed the presence of A. pallipes in the river stretch hit by the plague. In this outbreak, the spread of the infection could have been limited by a low density of the crayfish population and by the geographic conformation of the river basin, which includes a dense network of small tributaries, characterized by high flow velocity and low water temperature. In this particular setting, crayfish plague outbreaks can remain undetected. This underlines the importance of active monitoring programs aimed at the prompt recognition of both episodes of mortality and the presence of non-indigenous crayfish species.

Aphanomyces astaci in wild crayfish populations in Slovenia: first report of persistent infection in a stone crayfish Austropotamobius torrentium population

All 5 crayfish species inhabiting Slovenian freshwaters, of which 3 are indigenous crayfish species (ICS: Astacus astacus, Austropotamobius pallipes, and A. torrentium) and 2 are non-indigenous (NICS: Pacifastacus leniusculus and Cherax quadricarinatus), were inspected for the presence of Aphanomyces astaci, the causative agent of crayfish plague. Wild crayfish populations showing no clinical signs of infection were inspected using A. astaci-specific real-time PCR. In addition, a conventional PCR assay was employed and confirmative sequencing was performed. Out of 88 analyzed crayfish, 15/27 (55.6%) specimens of A. torrentium from Borovnišcˇ%%KERN_ERR%%ica Brook and 4/35 (11.4%) of P. leniusculus from the Mura River tested positive, showing low to moderate levels of infection (agent levels A1-A4 and A1-A3, respectively). Results revealed the presence of A. astaci not only in the resistant NICS but also in ICS, since the infected population of A. torrentium presumably had no contact with the NICS carrier and appeared to sustain A. astaci infection in the 2 sampling years. Although the A. astaci genotype has not yet been identified, a connection between the latent infection in ICS and a Group A strain of A. astaci, co-evolving with A. torrentium since its first introduction to Slovenia, is suggested as the most plausible conclusion. This is the first reported population of the genus Austropotamobius with persistent infection, in addition to the already known populations of the genus Astacus. Findings of the presumed co-evolution of A. astaci and ICS hosts open new perspectives, necessitating additional studies on the presence of A. astaci genotypes in the persistently infected ICS populations.

Paragonimus kellicotti flukes in Missouri, USA

Paragonimiasis is an infection caused by lung flukes of the genus Paragonimus. In Asia, P. westermani infections are relatively common because of dietary practices. However, in North America, cases of paragonimiasis, which are caused by P. kellicotti flukes, are rare. Only 7 autochthonous cases of paragonimiasis were reported during 1968-2008. In 2009, we reported 3 new case-patients with paragonimiasis who had been seen at our medical center over an 18-month period. Six additional case-patients were identified in St. Louis, Missouri, USA, and treated at Washington University-affiliated health centers in 2009-2010. We report detailed descriptions of these case-patients, which includes unusual clinical manifestations. We also describe public health interventions that were undertaken to inform the general public and physicians about the disease and its mode of transmission.

Re-examination of the prevalence of Aphanomyces astaci in North American crayfish populations in Central Europe by TaqMan MGB real-time PCR

We applied quantitative TaqMan minor groove binder real-time polymerase chain reaction (PCR) on DNA isolates from soft abdominal cuticle of 460 North American crayfish Orconectes limosus and Pacifastacus leniusculus, previously tested for Aphanomyces astaci presence by conventional semi-nested PCR. Both approaches target the internal transcribed spacers of the pathogen nuclear ribosomal DNA, but apply different specific sequence motifs and technologies. The real-time PCR approach seems to provide higher sensitivity; the number of crayfish that tested positive increased from 23 to 32%, and 10 additional crayfish populations were indicated as hosting the disease agent. However, the vast majority of newly recorded positives contained very low agent levels, from 5 to 50 PCR-forming units. An isolate producing a false positive result by the semi-nested PCR (apparently undescribed Aphanomyces related to A. astaci) remained negative using the real-time PCR. The present study shows that previous results based on the semi-nested PCR were not substantially influenced by false positives but might have suffered from some false negatives at low agent levels. Combining alternative methods may therefore provide more reliable conclusions on the pathogen's presence. Further, we found positive correlation between the prevalence of infection carriers in American crayfish populations and the average amounts of A. astaci DNA detected in infected local crayfish individuals.

Boil before eating: paragonimiasis after eating raw crayfish in the Mississippi River Basin

Paragonimiasis is a parasitic infection of the lungs caused by zoonotic lung flukes of the genus Paragonimus. Most cases are reported from Asia and caused by P. westermani following consumption of raw crustaceans. With the exception of imported cases, human paragonimiasis was rarely described prior to 1984 in the United States (US), which has only one indigenous lung fluke species, P. kellicotti. Between 1984 and 2010, 15 cases of P. kellicotti paragonimiasis were reported in the United States. This study will analyze all US cases and compare an earlier series of six cases reported during the period 1984-2005 with a recently reported cluster of nine cases from Missouri during the period 2006-2010 in order to determine any significant behavioral and/ or recreational risk factors for paragonimiasis and to recommend early diagnostic, treatment and preventive strategies. Significant behavioral and recreational risk factors included eating raw crayfish while on canoeing trips on local rivers (p = 0.002), eating raw crayfish while on canoeing trips in Missouri (p = 0.002), and eating raw crayfish while intoxicated (p = 0.007). The male:female case ratio was 9.3:1.0 and more than 80% of cases presented with fever, cough, pleural effusions and peripheral eosinophilia. One patient developed cerebral paragonimiasis, and one patient died of pneumonic sepsis. Clinicians should inquire about consumption of raw or undercooked crayfish in all patients with unexplained fever, cough, eosinophilia and pleural effusions returning from camping or canoeing adventures in P. kellicotti-endemic areas of the Mississippi River Drainage Basin; institute diagnostic evaluation by specific parasitological and serological methods and treat all cases as soon as possible to avoid the pulmonary and cerebral complications of paragonimiasis.

Detection and quantification of the crayfish plague agent in natural waters: direct monitoring approach for aquatic environments

Aphanomyces astaci, a specialised parasite of North American freshwater crayfish, is the disease agent of crayfish plague that is lethal to European freshwater crayfish. The life cycle of A. astaci has been inferred from experimental laboratory studies, but less is known about its natural sustainability and ecology. To address such questions, tools for monitoring of A. astaci directly in aquatic environments are needed. Here, we present an approach for detecting and quantifying A. astaci directly from water samples using species-specific TaqMan minor groove binder real-time PCR. Samples of a 10-fold dilution series from approximately 10(4) to approximately 1 spore of A. astaci were repeatedly tested, and reliable detection down to 1 spore was demonstrated. Further, to simulate real-life samples from natural water bodies, water samples from lakes of various water qualities were spiked with spores. The results demonstrated that co-extracted humic acids inhibit detection significantly. However, use of bovine serum albumin or the TaqMan Environmental Master Mix largely removes this problem. The practical application of the approach was successfully demonstrated on real-life water samples from crayfish farms in Finland hosting infected North American signal crayfish Pacifastacus leniusculus. Direct monitoring of A. astaci from aquatic environments may find application in the management of wild noble crayfish Astacus astacus stocks, improved aquaculture practices and more targeted conservation actions. The approach will further facilitate studies of A. astaci spore dynamics during plague outbreaks and in carrier crayfish populations, which will broaden our knowledge of the biology of this devastating crayfish pathogen.

Human paragonimiasis after eating raw or undercooked crayfish --- Missouri, July 2006-September 2010

Paragonimiasis is a parasitic disease caused by Paragonimus trematodes, commonly known as lung flukes. Humans become infected by eating raw or undercooked crayfish (also known as crawfish and crawdads) or freshwater crabs that harbor the parasites. Paragonimiasis most frequently involves the lungs, but can affect other organs, including the brain and skin. In North America, Paragonimus kellicotti causes infections among dogs, cats, and wild carnivores, but rarely infects humans. Paragonimiasis is not a nationally notifiable condition. In September 2009, physicians from the Washington University School of Medicine (WUSM) in St. Louis published details of three paragonimiasis cases diagnosed since July 2006 in persons who had eaten raw crayfish from rivers in Missouri, prompting the Missouri Department of Health and Senior Services (MDHSS), CDC, and WUSM to collaborate in paragonimiasis surveillance and prevention. During September 2009-September 2010, six additional cases were diagnosed in Missouri. These nine patients, aged 10-32 years, had fever, cough, pleural effusion, and eosinophilia. All had eaten raw or undercooked crayfish from rivers in Missouri while on canoeing or camping trips within 4 months of illness onset. Health-care providers should consider paragonimiasis when examining patients with unexplained fever, cough, eosinophilia, and pleural effusion or other chest radiographic abnormalities and should ask those patients whether they have eaten raw or undercooked crayfish.

Ulcerative disease outbreak in crayfish Orconectes propinquus linked to Saprolegnia australis in big Muskellunge Lake, Wisconsin

Crayfish populations in the area of the North Temperate Lakes Long Term Ecological Research (LTER) project, Wisconsin, USA, have been monitored for >25 yr. In 2005, native crayfish Orconectes propinquus from Big Muskellunge Lake were found with ulcerated lesions in the cuticle. In 2006, lesions occurred in 9.5% of sampled crayfish from the lake (n=3146). Ulcers generally occurred on the appendages of affected individuals but varied in location and severity. The prevalence of ulcers varied widely among sites, sample depths, and sampling dates, ranging from < 2% to >20%. The prevalence of ulcers in crayfish increased from a minimum in early June to a maximum in late July and August. In aquarium trials, healthy crayfish representing either O. propinquus or O. rusticus co-housed with ulcerated crayfish did not develop ulcers within 4 wk of exposure. Gross and histopathologic analyses of ulcerated crayfish revealed the presence of filamentous hyphae in the lesions while hemocytic infiltrates, melanotic reactions and silver-stained sections indicated that the ulcers had an oomycete etiology. Excised samples of ulcerated crayfish cuticle grown in culture developed an oomycete that was identified as Saprolegnia australis by PCR amplification and sequence analysis of 2 different DNA fragments. This is the first report of the occurrence of ulcers in wild crayfish associated with S. australis infection in the U.S.A. The advent of the outbreak and its underlying ecological causes are still under investigation.

Prevalence of the crayfish plague pathogen Aphanomyces astaci in invasive American crayfishes in the Czech Republic

In Central Europe invasive North American crayfishes are carriers of the oomycete Aphanomyces astaci, which causes crayfish plague. This lethal disease currently represents one of the major threats to native European crayfishes. We used molecular methods-species--specific amplification and sequencing of the pathogen DNA--to investigate the prevalence of individuals latently infected with A. astaci in 28 populations of two invasive American crayfish species (6 of the signal crayfish [Pacifastacus leniusculus] and 22 of the spiny-cheek crayfish [Orconectes limosus]) in the Czech Republic. The pathogen occurred in 17 investigated populations. We recorded a high variation in positive reactions, ranging from 0% to 100%, in populations of O. limosus. In P. leniusculus, however, only one individual out of 124 tested positive for the pathogen. There was a clear relationship between the water body type and pathogen prevalence in O. limosus. Infection ratios in isolated standing waters were usually low, whereas in running waters, pathogen prevalence often exceeded 50%. Other evaluated characteristics of potential plague pathogen carriers (size, sex, and the presence of melanized spots in the cuticle) seemed to be unrelated to infection. Our data suggest that in contrast to other European countries, O. limosus seems to be the primary reservoir of crayfish plague in the Czech Republic. Although all populations of alien American crayfishes may be potential sources of infections and should be managed as such, knowledge on the prevalence of the plague pathogen at various localities may allow managers to focus conservation efforts on the most directly endangered populations of native crayfishes.

Autochthonous Human Paragonimiasis in North America

Imported human paragonimiasis has been reported in the United States. However, autochthonous cases are rare. We describe a case of probable Paragonimus kellicotti infection associated with ingestion of crayfish and review all autochthonous cases in this country.

Early cysteine protease activity in excretory bladder triggers metacercaria excystment of Paragonimus westermani

The cysteine proteases of Paragonimus westermani metacercaria are known to initiate metacercaria excystment. However, their secretory sites, such as the intestine, tegument, and excretory bladder are not well defined. In this study, the metacercariae were labeled with bromodeoxyuridine (BrdU) to distinguish the initial activation sites. BrdU was labeled mainly at the excretory bladder and the excretory granules of the metacercariae and the newly excysted juvenile worms. This result shows that early 'defecation' of the proteases from the excretory bladder may accelerate the excystment of P. westermani metacercariae.

Molecular and biochemical characterization of hemoglobinase, a cysteine proteinase, in Paragonimus westermani

The mammalian trematode Paragonimus westermani is a typical digenetic parasite, which can cause paragonimiasis in humans. Host tissues and blood cells are important sources of nutrients for development, growth and reproduction of P. westermani. In this study, a cDNA clone encoding a 47 kDa hemoglobinase of P. westermani was characterized by sequencing analysis, and its localization was investigated immunohistochemically. The phylogenetic tree prepared based on the hemoglobinase gene showed high homology with hemoglobinases of Fasciola hepatica and Schistosoma spp. Moreover, recombinant P. westermani hemoglobinase degradaded human hemoglobin at acidic pH (from 3.0 to 5.5) and its activity was almost completely inhibited by E-64, a cysteine proteinase inhibitor. Immunohistochemical studies showed that P. westermani hemoglobinase was localized in the epithelium of the adult worm intestine implying that the protein has a specific function. These observations suggest that hemoglobinase may act as a digestive enzyme for acquisition of nutrients from host hemoglobin. Further investigations may provide insights into hemoglobin catabolism in P. westermani.

Ultrastructural characteristics and small subunit ribosomal DNA sequence of Vairimorpha cheracis sp. nov., (Microspora: Burenellidae), a parasite of the Australian yabby, Cherax destructor (Decapoda: Parastacidae)

This is the first record of a species of Vairimorpha infecting a crustacean host. Vairimorpha cheracis sp. nov. was found in a highland population of the Australian freshwater crayfish, Cherax destructor. The majority of spores and earlier developmental stages of V. cheracis sp. nov. were found within striated muscle cells of the thorax, abdomen, and appendages of the crayfish. Only octosporoblastic sporogony within sporophorous vesicles (SPVs) was observed. Diplokaryotic sporonts separated into two uninucleate daughter cells, each of which gave rise to four sporoblasts in a rosette-shaped plasmodium, so that eight uninucleate spores were produced within the persistent ovoid SPV. Ultrastructural features of stages in the octosporoblastic sequence were similar to those described for Vairimorpha necatrix, the type species. Mature spores were pyriform in shape and averaged 3.4x1.9 microm in dimensions. The anterior polaroplast was lamellar in structure, and the posterior polaroplast vesicular. The polar filament was coiled 10-12 times, lateral to the posterior vacuole. The small subunit ribosomal DNA (SSU rDNA) of V. cheracis sp. nov. was sequenced and compared with other microsporidia. V. cheracis sp. nov. showed over 97% sequence identity with Vairimorpha imperfecta and five species of Nosema, and only 86% sequence identity with V. necatrix. The need for a taxonomic revision of the Nosema/Vairimorpha group of species is discussed.

Thelohania montirivulorum sp. nov. (Microspora: Thelohaniidae), a parasite of the Australian freshwater crayfish, Cherax destructor (Decapoda: Parastacidae): fine ultrastructure, molecular characteristics and phylogenetic relationships

Thelohania montirivulorum sp. nov., a new species of microsporidian parasite, was found in a highland population of the Australian yabby, Cherax destructor. Data are presented on fine ultrastructure, developmental morphology and DNA sequence of the small subunit ribosomal DNA (SSU rDNA) and internal transcribed spacer region. The phylogenetic relationships of T. montrivulorum sp. nov. and other crayfish parasites in the genus Thelohania, based on the SSU rDNA sequence, are investigated. Fine ultrastructure, patterns of sporogony and SSU rDNA sequence similarities indicate T. montirivulorum sp. nov. is congeneric with T. parastaci, a parasite of lowland populations of C. destructor, and with T. contejeani, a parasite of European freshwater crayfish. SSU rDNA data suggests Thelohania species found in crustacean hosts are more closely related to the Vairimorpha/ Nosema clade of species from insect and crustacean hosts than to the fire ant parasites, T. solenopsae and Thelohania sp.

Thelohania parastaci sp. nov. (Microspora: Thelohaniidae), a parasite of the Australian freshwater crayfish, Cherax destructor (Decapoda: Parastacidae)

Thelohania parastaci sp. nov. infects the Australian freshwater crayfish, Cherax destructor. Data on morphology, developmental patterns and sequences from the small subunit (SSU) and internal transcribed spacer (ITS) regions of the ribosomal DNA (rDNA) of T. parastaci sp. nov. are described. The ultrastructural features of different life cycle stages are very similar to those of the European crayfish parasite Thelohania contejeani. T. parastaci sp. nov. exhibits simultaneous dimorphic sporogony in muscle tissue. Meronts, sporonts and spores are found in muscle tissue, within haemocytes in the hepatopancreas, and in the intestinal wall of infected crayfish. T. parastaci sp. nov. shows 92% sequence identity with T. contejeani and only 67% sequence identity with the fire ant pathogen T. solenopsae, when SSU rDNA sequences are compared. Analysis of SSU rDNA and ITS sequences of T. parastaci sp. nov. from crayfish from Victoria, Western Australia, and New South Wales indicate that the parasite has a wide geographical distribution in Australia.

Recovery, growth and development of Macroorchis spinulosus in albino rats

The developmental features, growth and organogenesis of Macroorchis spinulosus were observed in albino rats. Globular and thick walled metacercariae, possessed a stylet, Y-shaped excretory bladder and extracecal testes. In albino rats, M. spinulosus showed habitat shifting. The majority of M. spinulosus reside in the jejunum for the first four days post infection (p.i.) and migrate to the duodenum at the later stage of infection. M. spinulosus grew rapidly during the first four days and reached full maturity at 14 days p.i. and later reduced in size. The ovary was separated from the genital primodium at one day p.i. The seminal vesicle appeared on the third day and divided into two sacs on the fourth day p.i. and intrauterine eggs and sperm mass were produced on the fourth day. Organogenesis and enlargement of reproductive organs governed the growth of M. spinulosus. The similarity of related species of the genus Macroorchis to M. spinulosus was discussed in consideration to developmental features.

Occurrence of a diploid type and a new first intermediate host of a human lung fluke, Paragonimus westermani, in Korea

The biology, chromosome number, and karyotype of a lung fluke, Paragonimus westermani (Kerbert, 1878) collected in Haenam, Haenam-gun Chollanam-do, Korea were analyzed. We compared the size of metacercariae from Haenam with those taken from a crayfish collected at Youngam, Youngam-gun, Chollanam-do, Korea. The mean length of P. westermani metacercariae from Haenam was 300.3 microm and that from Youngam was 362.0 microm. Adult worms were recovered from the lungs of experimentally infected dogs. The mean egg sizes obtained from adult flukes were 72.1 x 46.8 microm from Haenam and 93.5 x 54.2 microm from Youngam. Semisulcospira tegulata collected in the Youngam area were found to be infected with cercariae of P. westermani, one of the snail-borne human lung fluke trematodes in Korea. Of 4218 snails studied, 5 (0.12%) harbored P. westrermani larvae. This is the first report of S. tegulata serving as the initial intermediate host of P. westermani. The chromosome numbers of P. westermani from Haenam and Youngam were 2n = 22 and 3n = 33. The diploid type of P. westermani has not been previously reported in Korea.

Sequence analysis of the ribosomal internal transcribed spacer DNA of the crayfish parasite Psorospermium haeckeli

Two morphotypes of the crayfish parasite Psorospermium haeckeli were isolated from 2 crayfish species of different geographical origin. The oval-shaped sporocysts were obtained from the epidermal and connective tissue beneath the carapace of the noble crayfish Astacus astacus from Sweden and Finland. Elongated spores were isolated from the abdominal muscle tissue of the red swamp crayfish Procambarus clarkii from USA. To compare genetic divergence of 2 morphotypes of the parasite, the ribosomal internal transcribed spacer (ITS) DNA (ITS 1 and ITS 2) and the 5.8S rRNA gene were cloned and sequenced. The analysed region is variable in length, with the ribosomal ITS sequence of the European morphotype longer than the North American one. Sequence diversity is found mainly in ITS 1 and ITS 2 regions, and there is 66% and 58% similarity between the 2 morphotypes, respectively. Thus, analysis of the ribosomal ITS DNA suggests that P. haeckeli forms obtained from Europe and North America are genetically diverse, which supports the previously reported morphological characteristics.

Theloiania contejeani Henneguy, 1892: dimorphic life cycle and taxonomic affinities, as indicated by ultrastructural and molecular study

Thelohania contejeani is a dimorphic species with two simultaneous routes for sporogony. In the first, diplokaryotic sporonts produce 8 uninucleate spores with 9-10 turns of polar tube, within a sporophorous vesicle wall. The episporontal space contains two kinds of tubules and a spongiform mass. In the second, single diplokaryotic sporonts produce small membrane-bound compartments in which they transform into mature diplokaryotic spores with 5-6 turns of polar tube. Analysis of the small subunit (SSU) rRNA revealed two copies of 16S-like rDNA, one of them 1,311 bp, the other 1,361 bp long, with an overall identity of 93%. The majority of sequence differences were located in a 120-bp stretch between positions 336 and 456, with only 40.5% identity between the sequences. Careful consideration suggests that the shorter sequence represents a pseudogene. According to the SSU rDNA sequence, T. contejeani is not closely related to any of the microsporidians where this sequence is available and could not be unambiguously placed in the 16S phylogenetic tree.

First record of Lagenophrys dennisi (Ciliophora: Peritrichia) on the exoskeleton of crayfish Cambarellus patzcuarensis

Lagenophrys dennisi, a peritrich ciliate, was observed attached to the exoskeleton of the crayfish Cambarellus patzcuarensis in Lake Pátzcuaro, Michoacán, Mexico. Lagenophrys dennisi presents a hemispheroidal, suboval or oval lorica in dorsal view, the distinctive lorica aperture consists of a pair of lips highly arched, unthickened, and smooth. Comparison of morphometric characters of the ciliate with previous records is made. Structures such as a "V"-shaped lorica suture, collar ridges, and myoneme are proposed for species identification. An anterior crescentic thickening on the dorsal surface of the lorica was observed under the scanning electron microscope. Lagenophryids were associated with 11 of 13 body parts with antennules and rostrum showing the highest prevalence. Lagenophrys dennisi was also found attached to submerged glass slides. This study represents the first record of L. dennisi on C. patzcuarensis and the first record of its presence in Mexico.

North American paragonimiasis. A case report

BACKGROUND

Paragonimiasis is a parasitic infection with a predilection for pulmonary involvement. Paragonimus species occur throughout the world and exist in nature in a snail-crustacean-mammalian life cycle. Human disease is most frequently encountered in cultures that ingest raw or undercooked crustaceans. North American paragonimiasis, caused by an endemic Paragonimus species, Paragonimus kellicotti, predominantly causes disease in carnivorous and omnivorous animals but may cause human disease if the intermediate host, the crayfish, is ingested raw or undercooked.

CASE

A previously healthy, 21-year-old male was infected with P kellicotti and developed parasitic hemoptysis. The disease was contracted through the ingestion of local, undercooked crayfish. Diagnosis was established through the morphologic examination of eggs in the cytologic preparation of bronchioalveolar lavage fluid. The patient was successfully treated with praziquantel and recovered without incident.

CONCLUSION

Paragonimiasis is a cause of parasitic hemoptysis worldwide. Paragonimiasis is infrequently encountered in North America and is usually not considered in the differential diagnosis of hemoptysis unless specific risk factors are known. The cytologist or cytopathologist, therefore, may be the first to encounter the diagnostic eggs and should be familiar with this disease.

Reintroduction of Profilicollis Meyer, 1931, as a genus in acenthocephala: significance of the intermediate host

Polymorphid acanthocephalans with long necks, spheroid proboscides, and eggs without polar swellings of the fertilization membrane constitute a morphologically distinct group of species. In the past, this taxon was considered a separate genus, Profilicollis. More recently, workers have been unwilling to accept these features as generic-level characters, and presently the group is considered a subgenus of Polymorphus. An analysis prompted by our studies of various polymorphid cystacanths in crabs along the coasts of Scotland and the U.S.A. reveals that all records of Polymorphus in decapods refer to species with 6 cement glands frequently assigned to Hexaglandula, to incidental occurrences of species purported to be Polymorphus minutus, or to species of the subgenus Profilicollis. Occurrence in decapod crustaceans implies substantial life history differences from the other species of the genus occurring in amphipod crustaceans. We conclude this, together with morphological distinctiveness, justifies return of Profilicollis to full generic status within Polymorphidae.

Infection status of Paragonimus westermani metacercariae in crayfish (Cambaroides similis) collected from Bogildo (Islet), Wando-gun, Chollanam-do, Korea

During the period from October 1996 to November 1998, the infection status of Paragonimus westermani metacercariae in freshwater crayfish (Cambaroides similis) collected from Bogildo (islet). Wando-gun, Chollanam-do, which is known for an endemic area of P. westermani in Korea, were examined. The average infection rate of Paragonimus metacercariae in crayfish was 88.6%, and mean number of metacercariae per infected crayfish was 30.2. This metacercarial density was the highest in the group of weight in 7.1-9.0 g. These results suggest that the natural life cycle of P. westermani is still well-preserved in Bogildo.

Effect of fixed epimastigote forms of Trypanosoma cruzi on the hemocytes and the prophenoloxidase-activating system of the crayfish Pacifastacus leniusculus

The effect of the parasite Trypanosoma cruzi on the hemocytes and the prophenoloxidase (proPO)-activating system of the crayfish Pacifastacus leniusculus was studied. Incubation of the crayfish hemocyte lysate with fixed epimastigote forms of the parasites (4 x 10(5) cells/ml) induced a marked activation of the crayfish proPO system, measured as phenoloxidase activity. The activation of proPO by the parasite was much stronger (7-fold) than that induced by beta-1, 3-glucans (1 mg/ml) which are known to be efficient elicitors of the proPO system. The fixed parasites promoted the spreading and degranulation of different populations of the crayfish hemocytes isolated by Percoll gradients, and were often observed to be attached to the crayfish hemocytes in rosette-like fashion. The attachment of the epimastigote forms of T. cruzi to the crayfish blood cell surface was not dependent on the adhesive 76-kDa protein released by the crayfish hemocytes, since the exocytotic inhibitor SITS and monospecific antibodies to the 76-kDa protein did not prevent parasite adhesion. The crayfish hemocytes apparently are able to phagocytose the fixed epimastigote forms of T. cruzi in vitro.

Redescription of Macroorchis spinulosus Ando, 1918 (Digenea: Nanophyetidae) encysted in the fresh water crayfish, Cambaroides similis

Macroorchis spinulosus Ando, 1918 (Digenea: Nanophyetidae) is redescribed based on adult flukes recovered from experimental mice, rats and cats which were fed with metacercariae encysted in the muscle of the crayfish. Cambaroides similis. A total of 117 adult flukes were harvested from the small intestine of the experimental animals at 5-21 days post-infection. The worm recovery rate was 31-37%, not significantly different among the three kinds of animals. The metacercariae were round, 0.18 mm in average diameter, encysted with two layers of thick walls, and possessing a stylet on the oral sucker and Y-shaped excretory bladder. The adult flukes were oval, 0.66-0.71 mm long and 0.36-0.41 mm wide, and characterized by the presence of a stylet on the oral sucker, variable location of the ovary near the mid-portion of the body, bilobed seminal vesicle, and anterolateral location of two testes. These morphological features were a little different from the original description, hence, an emended version of M. spinulosus was given. M. spinulosus is a new intestinal trematode of animals and possibly man in Korea.

[The biology of Paragonimus westermani ichunensis in the Maritime Territory. Experimental research]

It has been experimentally found that larval and pulmonary paragonimiasis types are caused by the trematode Paragonimus westermani ichunensis. The development of either paragonimiasis in nontypical definitive hosts depends on the stage of larval development when they penetrate into the mammal. Only the P. westermani ichunensis trematode is likely to develop with the participation of Juga mollusks on the territory of the Primorye.

Changes of IgE production, splenic helper and suppressor T lymphocytes in mice infected with Paragonimus westermani

Effects of Paragonims westermani infection were observed in mice on the change of serum IgE level, the number of peripheral eosinophils and the distribution of Thy 1.2+ (CD3), L3T4+ (CD4), and Lyt-2+ (CD8) splenic T lymphocytes without mitogen stimulation. BALB/c mice were infected with 20 metacercariae of P. westermani each. Total serum IgE increased at 3 weeks after the infection and reached a peak on week 4 and maintained high levels of IgE until the 23rd week. Peripheral eosinophil numbers increased at the second week and attained peak level on week 9. The frequency of L3T4+ (CD4) and Lyt-2+ (CD8) T lymphocytes decreased slightly until 4 weeks after the infection, but not significantly. Absolute number of L3T4+ and Lyt-2+ T lymphocytes, and the ratio of L3T4/Lyt-2 were not markedly changed over the period of observation. The frequency of Thy 1.2+ (CD3) T lymphocytes in the infected group slightly decreased until 4 weeks after the infection and showed significant reductions at the 2nd and 4th week of the infection (p < 0.05).

[A investigation on the types of chromosomes and epidemiology of Paragonimus westermanni in Huadian city of Jilin Province]

An investigation on the types of chromosomes and epidemiology of Paragomanni westermanni in five Villages and towns of Huadian city was carried out. The data showed that the infection rate of crayfish, the first intermediate host, was 100% and the infectiosities varied from 99 to 160/per crayfish in the five areas. The genetic patterns of all the cysticercus, ovum and imagoes had been proved to be diploid by morphological and genetic studies. The infection rate of animal final host such as dogs and cats reached as highly as 94.3%, and all the infected animals presented typical pathological changes. Among the total 1008 examined people, the positive rate of skin test of hypersensitivity was 25.1%, and only 0.4% was positive sputum test. Moreover, very few infected people had remarkable clinical expressions, suggesting that the infection of most people was only "transient", or of the larval parasitisim. The results showed that diploid Paragonimus westermanni were not strongly pathogenic to human beings.

[Changes in the monocercus cercomer in the cysticercoid cavity and the hemocoel of the nonspecific host]

In order to elucidate the functional role of cercomer in larvae of the monocercus type their transplantation from the specific host Chironomus obtusidens to Gammarus lacustris was conducted. At early stages after the transplantation proceeds an increase in the functional activity of the tegument of follicles of the cercomer followed by their complete destruction in 3 or 4 days. On the surface of the exocyst membrane an adhesion of the host's haemocytes occurs, which becomes more distinct in 3-4 days when the process acquires a character of local encapsulation. Within the same period, in the places of haemocytes aggregation, a local resorption of the exocyst external membrane takes place. Later intensification of the host response to transplant is associated with the destruction of follicles of the cercomer. In one case the occurrence of follicles of the cercomer in the cavity of cysticercoid was observed that is caused by the microbe affection of the latter. In the zone of contact of the tegument of scolex and neck with follicles of the cercomer an increased secretion (the microapocrine type) of the tegument, disturbance of the microvillous tegument of the cercomer's follicles and their destruction are observed. Incompatibility of the tegument of definitive departments and cercomer, which arises during differentiation of larvae, is supposed to affect the formation of scolex invagination in the evolution of larvae of Hymenolepis.

[A new method of therapy for branchiobdellosis in crayfish]

Crayfish (Astacus fluviatilis Fabricius, 1793) were treated three times with a bath of diluted ammonia water and proflavine for four and six minutes at a temperature of 18 degrees C to get rid of the ectoparasitic worms of Branchiobdella parasita Henle, 1835; the hatching ability of the Branchiobdella parasita eggs was stopped after the treatment. No lethal effect of the bath on the crayfish of 5 to 14 cm was observed, the lethal effect on the young crayfish borne on the uropods of the female crayfish cannot be eliminated: during the baths the young crayfish died (the death rate was approximately 6% of the average fertility of crayfish); the young crayfish may have been damaged during the treatment operations with the crayfish. The bath of diluted ammonia water and proflavine may be recommended for the treatment of branchiobdellosis in crayfish to be planted, or after several-hour storage of crayfish supplied to the market. One replication of the above cycle is sufficient according to the results obtained. The ammonia content in the ammonia water depends also on the duration of storage and on the storage temperature--it can drop during the storage. Therefore the ammonia water should be used as soon as possible after the despatchment from the place of production; the ammonia content should be determined by means of titration before preparing the bath, and according to this content the dilution ratio should be adjusted.