Blood Fluke Infection Research Articles

Molecular and morphological identification of Cardicola (Trematoda: Aporocotylidae) eggs in hatchery-reared and migratory Atlantic bluefin tuna (Thunnus thynnus L.)

A microscopic and a molecular approach was used to investigate blood fluke infection in the very first specimens of Atlantic bluefin tuna (Thunnus thynnus, Scombridae) that were born in captivity and that were never moved from their specific cage culture sites in the Mediterranean. Data were compared with infection in wild, migratory bluefin tuna which were captured and fattened along the Spanish Mediterranean coast. Wild and cultured populations sampled in the present study harbored the same Cardicola spp. richness and showed statistically insignificant differences in overall parasite prevalence. Three morphotypes, crescent-shaped, fusiform and oval eggs, were observed in both non-migrant and migrant tuna. According to partial ITS2 and 28S rDNA sequences they belong to Cardicola opisthorchis, Cardicola forsteri, and to Cardicola sp., a recently described species, phylogenetically closely related to Cardicola orientalis. All three species were simultaneously present in some specimens. No significant difference in overall parasite prevalence was observed, though the prevalence of eggs of individual species, i.e. C. opisthorchis and C. forsteri, was significantly higher in fattened bluefin tuna. Our results strongly support a Mediterranean origin of the three Cardicola species encountered in cultured specimens and suggest that the intermediate hosts of these Cardicola species occur along the Mediterranean coast. Thus, infection with these parasites is not exclusively a result of infections happening along the migratory routes of wild bluefin tuna, in the Atlantic Ocean, as previously suggested. Once transferred to the sea for fattening, Atlantic bluefin tuna are at risk of infection with up to three different species of the genus Cardicola in along the Mediterranean coast in southeast Spain. On the contrary, C. orientalis infections might be associated to long-distance migration and an overlapping Thunnus maccoyii and Thunnus orientalis distribution.Statement of relevanceThis is the very first parasitological study conducted in T. thynnus born in captivity and cultured local in the Mediterranean. The results show that once transferred to the sea for fattening, they are at risk of infection with up to three different species of the genus Cardicola. These results strongly imply a Mediterranean distribution of these species.

Factors affecting abundance and prevalence of blood fluke, Cardicola forsteri, infection in commercially ranched southern bluefin tuna, Thunnus maccoyii, in Australia

A survey of blood fluke, Cardicola forsteri, infection in ranched southern bluefin tuna, Thunnus maccoyii, was undertaken over three farming seasons, from March 2004 to September 2006. Analyses of covariance and logistic regression were used to explore the effects of company, year, season, time in culture, and condition index on intensity, abundance and prevalence of blood fluke infection. Average prevalence of blood fluke infection was 62.64% over the period of the survey. Average intensity was 6.20 (±0.57) fluke per infected host and the average abundance was 3.70 (±0.57) fluke per host. Year did not influence mean intensity or abundance although a significant decrease in prevalence in 2005 was evident. Tuna harvested in winter had a significantly greater abundance and prevalence of blood fluke than the tuna harvested in autumn. No effect of intensity or abundance of infection was observed on the condition of the infected tuna. A universal factor in explaining variation in C. forsteri intensity, abundance and prevalence was company. Differences in infection levels between tuna from different companies may be related to differences in husbandry measures employed on each farm, or due to different average sizes of tuna farmed by each of the companies, or due to the location of the operations.

Larval stages of the bluefin tuna blood fluke Cardicola opisthorchis (Trematoda: Aporocotylidae) found from Terebella sp. (Polychaeta: Terebellidae)

We found aporocotylid larval stages (sporocysts and cercariae) from five individuals of terebellid polychaete Terebella sp., which were collected from seabed substrate and ropes and floats attached to tuna cages in a tuna farm on the coast of Tsushima Island, Nagasaki, Japan. Nucleotide sequences of the regions of internal transcribed spacer 2 ribosomal DNA and 28S ribosomal DNA from these larval stages were 100% identical to those of Cardicola opisthorchis registered in GenBank. C. opisthorchis is a pathogen causing blood fluke infection of Pacific bluefin tuna Thunnus orientalis, which is considered to have a significant impact on the Japanese Pacific bluefin tuna aquaculture industry. This is the first description of the intermediate host of C. opisthorchis. This indicates that the life cycle of C. opisthorchis is completed within tuna farms in this area.

Schistosomiasis

Human schistosomiasis is a common blood fluke infection in the tropics and subtropics. The organism requires a specific fresh water snail intermediate as host and this determines its geographical distribution. Humans become infected following water exposure, with rural communities and children having the highest burden of disease. Travellers to areas of high endemicity are at risk of infection as they frequently engage in pursuits that expose them to fresh water. Disease manifestations range from acute hypersensitivity reactions to chronic illness with intestinal, hepatic and bladder disease. Infection can often be asymptomatic and travellers to endemic areas should be screened for schistosomiasis after return. Treatment is highly effective, even in advanced disease, and the diagnosis should be considered in individuals with possible clinical illness who have travelled to or lived in endemic areas.

Oral treatment of praziquantel as an effective control measure against blood fluke infection in Pacific bluefin tuna ( Thunnus orientalis)

Aquaculture of tuna has shown exponential growth in the recent years. In association with the global development of tuna aquaculture, problems with parasitic infections have arisen. Among the parasites found in cultured tuna, blood flukes are considered to be a significant threat as their eggs accumulate in the gills and interfere with the gas exchange process. To date, two species of blood fluke from the genus Cardicola have been found in Pacific bluefin tuna ( Thunnus orientalis, PBT) cultured in Japan. We conducted an experiment to develop a drug treatment against the blood flukes of cultured tuna. Artificially produced juvenile tuna that were naturally infected with blood flukes were orally administered with anthelmintic praziquantel (PZQ) of 150, 15, 1.5 and 0 mg kg −1 BW for three consecutive days, and differences in the abundance of adults and eggs in the gills were assessed. In the fish given 150 and 15 mg kg −1 BW PZQ, adult worms in the heart ventricle were eradicated by day 8 post treatment with the number of eggs in the gills gradually declining over time. However, small numbers of adults re-appeared by week 3 or 5 post treatment. The drug does not seem to affect eggs as viable miracidia were observed throughout the experiment. Mortalities in the two lower dose groups were significantly higher than the groups in which PZQ doses were shown to be effective. The study empirically demonstrated the efficacy of PZQ on Cardicola blood flukes and that the parasite significantly affects the survival of juvenile PBT. The oral PZQ treatment may be an essential practice for sustainable aquaculture of PBT.

Morphology and distribution of blood fluke eggs and associated pathology in the gills of cultured Pacific bluefin tuna, Thunnus orientalis

Infestations of blood flukes of the genus Cardicola have been observed in juvenile Pacific bluefin tuna (PBT) cultured in Japan. Infected fish harbor large numbers of parasite eggs in their gills. Although the link between blood fluke infection and juvenile mortality is not clear, accumulation of parasite eggs appears to be pathogenic to the fish. We investigated the origins, general morphology/distribution, and histopathology of these eggs in artificially produced 0yr old PBT. Dead and live fish were sampled on several occasions from two culture facilities in Wakayama prefecture, Japan. The number of eggs in each gill filament was enumerated under a microscope. In addition, we estimated the total number of eggs by dissolving the gills in a weak NaOH solution. We observed two morphologically distinct egg types in the gill filaments, smaller, oval shaped eggs in the gill lamellae and larger, crescent shaped eggs that occurred primarily in the filamentary arteries. Based on the ITS2 sequence, the ovoid and crescent shaped eggs were identified as C. orientalis and C. opisthorchis, respectively. Eggs of the former species were more abundant (maximum: 6400 per filament) than the latter (maximum: 1400), but the number was highly variable among filaments. The eggs of the latter species were relatively evenly distributed among the filaments. In a heavily infected individual, we estimated a total of >4.5 million eggs were present in the gills on one side of the fish. The number of eggs from the two species was positively correlated to each other and the dead fish tended to harbor more eggs than the live fish. Histological observation revealed host responses around the eggs, including encapsulation by fibroblasts and nodule formation, as seen in response to other aporocotylid eggs. In addition, we observed widespread fusion of gill lamellae and blockage of the filamentary arteries in some instances. Our results provide information that can be used for routine diagnosis of Cardicola blood flukes in cultured tuna and suggest they represent a risk to juvenile PBT.

A new blood fluke of the genus Cardicola (Trematoda: Sanguinicolidae) from Pacific bluefin tuna Thunnus orientalis (Temminck & Schlegel, 1844) cultured in Japan

A new sanguinicolid blood fluke, Cardicola orientalis n. sp., is described from the afferent branchial artery and heart of Pacific bluefin tuna Thunnus orientalis (Temminck & Schlegel) cultured in Mie and Nagasaki Prefectures, Japan. The new species is most similar to C. ambrosioi Braicovich, Etchegoin, Timi et Sardella, 2006 from the Brazilian flathead, Percophis brasiliensis Quoy & Gaimard, but can be differentiated by the position of the female genital pore (in midline or slightly sinistral in C. orientalis vs. sinistral in C. ambrosioi) and much longer distance between male and female genital pore (101 μm vs. 27 μm). In wet mount preparations of infected fish, eggs were accumulated in great numbers in the gill lamellae and afferent filament arteries. Importance of this blood fluke infection of cultured Pacific bluefin tuna in Japan is discussed.

Holidays in the Sun and the Caribbean’s Forgotten Burden of Neglected Tropical Diseases

Holidays in the Sun and the Caribbean’s Forgotten Burden of Neglected Tropical Diseases

Serological evidence of an antibody response in farmed southern bluefin tuna naturally infected with the blood fluke Cardicola forsteri

In this study, adaptive immune response was investigated in farmed southern bluefin tuna, Thunnus maccoyii, infected with a sanguinicolid Cardicola forsteri. A cohort (Cohort 2005) of southern bluefin tuna was sampled between March 2005 and August 2006. Samples were taken at the transfer of wild caught tuna to sea cages and then at regular intervals. Parasite intensity, abundance and prevalence data were recorded. An ELISA was developed to detect and quantify an antibody response against the blood fluke in southern bluefin tuna serum. Intensity and prevalence of the blood fluke were shown to peak in May 2005 at 10.9 flukes per infected fish (SE = 1.72) and 97.5% prevalence and then decreased to low prevalence (10%) and intensity (1.0). There were no significant changes in prevalence or intensity in 2006. Antibody titres and seroprevalence increased from 1.37 U μl −1 and 10% at transfer in March 2005 to reach a peak in December 2005 of 25.86 U μl −1 (SE = 6.26 U μl −1) and 66.66%. No significant changes were observed in antibody titres for the same cohort of fish during 2006. Parasitological and serological values from Cohort 2005 were compared to a 2006 cohort (Cohort 2006) in March 2006 and August 2006 to determine if prior infection in Cohort 2005 elicited any protection against infection in 2006. Although significant differences were not observed in intensities between cohorts it was shown that Cohort 2005 had significantly lower abundances and prevalences of blood fluke infection than Cohort 2006. Although there was no significant difference in mean antibody titres between cohorts in March 2006, the mean antibody titre of Cohort 2006 was significantly greater than that of Cohort 2005 in August 2006. No significant differences were observed in seroprevalence. This is one of the few studies to demonstrate the development of acquired resistance in fish against a parasite in an aquaculture environment under natural infection conditions.

Analysis of the 5q31–33 Locus Shows an Association between Single Nucleotide Polymorphism Variants in the IL-5 Gene and Symptomatic Infection with the Human Blood Fluke, Schistosoma japonicum

Genetic studies of human susceptibility to Schistosoma (blood fluke) infections have previously identified a genetic locus determining infection intensity with the African species, Schistosoma mansoni, in the 5q31-33 region of the human genome that is known to contain the Th2 immune response cluster, including the genes encoding the IL-4, IL-5, and IL-13 cytokines. These cytokines are key players in inflammatory immune responses and have previously been implicated in human susceptibility to infection with the Asian species, S. japonicum. In a nested case control study, we genotyped 30 HapMap tagging single nucleotide polymorphisms (SNPs) across these three genes in 159 individuals identified as putatively susceptible to reinfection with S. japonicum and in 133 putatively resistant individuals. A third group comprising 113 individuals demonstrating symptomatic infection was also included. The results provided no significant association at a global level between reinfection predisposition and any of the individual SNPs or haplotype blocks. However, two tagging SNPs in IL-5 demonstrated globally significant association with susceptibility to symptomatic infection. They were in strong linkage disequilibrium with each other and were found to belong to the same haplotype block that also provided a significant association after permutation testing. This haplotype was located in the 3'-untranslated region of IL-5, suggesting that variants in this region of IL-5 may modulate the immune response in these individuals with symptomatic infection.

Lumbar Intramedullary Spinal Schistosomiasis Presenting as Progressive Paraparesis: Case Report

Blood fluke infection or schistosomiasis affects up to 300 million people worldwide. Although infection of the hepatic and urogenital systems commonly occurs, central nervous system involvement is rare. When presenting in the spinal cord, schistosomiasis can be difficult to diagnose because it can present as mass lesion or transverse myelitis. We describe a patient with lumbar intramedullary spinal schistosomiasis who presented to a tertiary medical center in the United States and discuss the diagnosis and treatment of this rare disease. A 25-year-old Brazilian man presented with progressive, subacute, bilateral lower extremity motor and sensory deficits and disturbances in bladder function. Magnetic resonance imaging revealed a diffusely enhancing mass expanding the region of the conus medullaris. Laboratory investigation disclosed serum and cerebrospinal fluid eosinophilia. Ultimately, cerebrospinal fluid serology demonstrated the presence of Schistosoma mansoni. The patient was treated with praziquantel and steroids and made a marked recovery. The clinical and radiographic manifestations of spinal schistosomiasis can mimic those of intra-axial spinal tumors and transverse myelitis. To avoid unnecessary surgery or delay in treatment, the clinician must have knowledge of this type of presentation. The increasing volume of international travel and high prevalence of the disease worldwide increases the possibility that the practicing neurosurgeon in the United States may encounter this rare but treatable disease.

An epizootic and its decline of a blood fluke, Cardicola forsteri, in farmed southern bluefin tuna, Thunnus maccoyii

The epidemiology of a blood fluke, Cardicola forsteri, was examined in cultured southern bluefin tuna, Thunnus maccoyii, over a 6-month grow-out season in Port Lincoln, South Australia. Ten tuna were sampled during the transfer from tow cages to sea cages in March, and then ten tuna from each cage once a month until August. A total of 210 tuna were sampled. Intensities and prevalences were found to increase rapidly and peak 2 months after transfer with 100% prevalence and an overall average of 27 flukes per infected tuna (S.E. = 3.91), with one tuna having a recorded 99 worms in its heart. After this peak, both prevalence and intensity declined to an average of 3.1 flukes per infected tuna (S.E. = 0.88) and a prevalence of 35%. Condition Indices, calculated from weights and lengths and used as a measure of production, were shown to have no significant relationship with intensity or prevalence. It is concluded that T. maccoyii is able to control blood fluke infection, despite decreasing water temperatures.

Histopathology of cultured marine fish, Seriola purpurascens (Carangidae) infected with Paradeontacylix spp. (Trematoda: Sanguinicolidae) in its vascular system.

Cutured carangid, Seriola purpurascens, infected with sanguinicolid trematodes, Paradeontacylix spp. were examined histopathologically. Fish were sampled bimonthly in Shikoku from March 1984, when mortalities of heavily infected fish occurred, until January 1985. Pathological changes related to the blood fluke infection were limited in the heart and gills. They were summerized as hyperplasia of gills, encapsulation of eggs in the gills and ventricle, and papillate proliferation of the endothelium in the afferent branchial arteries. No necrosis was found in any organs at any stages of infection. The infection had seasonality, and the host reaction changed with it. Survived fish (1+) got milder infection next year than 0+ fish. It is probable from the histological changes in the heart and gills that the cause of mass mortalities among 0+ fish from December 1983 to March 1984 was physical blockage of the blood flow due to accumulation of the eggs in the gill filaments and to papillae formation in the afferent branchial arteries.

Growth, mortality, and hematology of cutthroat trout experimentally infected with the blood fluke Sanguinicola klamathensis.

Studies were made of the growth, mortality, and blood changes of cutthroat trout (Salmo clarki) experimentally infected with the blood fluke, Sanguinicola klamathensis Wales 1958. Five hundred non-infected cutthroat trout fingerlings and 500 exposed to a population of 6000 Fluminicola fusca snails with a 6% prevalence of infection with the blood fluke S. klamathensis were maintained for several months. Following 3 months exposure to the blood fluke infection, the experimental group had 80% mortality. Packed cell volumes and oxyhemoglobin levels were reduced significantly in the experimental fish as compared to the controls. Control fish continued to grow logarithmically in total weight, while the experimental fish declined in total weight due to parasitism and mortality. There were significant differences between the two groups for the average weight per fish and the average length per fish during the period of mortality.

A technique for studying the in vitro effect of serum on activated taeniid hexacanth embryos.

THE in vitro effects of normal and immune serum on various nematode larvae and on schistosome cercariae have been described by a number of workers1. The use of helminth larvae for the detection of natural and acquired immune responses has proved to be a very useful immunological tool, and some progress has been made towards using this method in the diagnosis of some nematode and blood-fluke infections.

Life History of Manson's Blood Fluke (Schistosoma mansoni). I. Extramammalian Phase of the Cycle.

The work of which this contribution forms a part was carried on in Puerto Rico, where Manson's blood fluke infection is an important and extensive clinical entity. The lateral-spined eggs of the parasite were obtained from the feces of human and experimental animals. The stools were washed and concentrated either by centrifugation or by sedimentation. The numbers of these eggs obtained from a 24-hour specimen varied not only with the age of the infection in the mammalian host but also fluctuated from day to day. The majority were viable, and contained ciliated larvae (miracidia), which were studied for detailed morphological features, including the number and pattern of the epithelial plates.Hatching was found to be due to several factors, including the maturity and vitality of the miracidium, the tonicity of the medium and mechanical agitation of the eggs. Some larvae hatch immediately after washing and concentration but the majority require from 12 to 24 hours. After swimming around for several minutes ...