First report of Lymnaea columella Say, 1817 (Pulmonata: Lymnaeidae) naturally infected with Fasciola hepatica (Linnaeus,1758) (Trematoda: Digenea) in Argentina

We report the first evidence of natural infection of Lymnaea columella with Fasciola hepatica in Argentina. A sample of 601 snails was collected in May 2003 in northeastern Corrientes, a province bounded on the north by Paraguay, on the east by Brazil and on the southeast by Uruguay. Among 500 examined snails, 44 (8.8%) were exclusively infected with F. hepatica. Parasite identification was based on morphological features of cercariae from snails, and of eggs and adult flukes from Wistar rats. We discuss the events suggesting that an enzootic transmission cycle of F. hepatica has been recently established in northeastern Corrientes.     

Identification of Fasciola species isolated from Egypt based on sequence analysis of genomic (ITS1 and ITS2) and mitochondrial (NDI and COI) gene markers

Fascioliasis has a negative impact on the farming industry in both developed and developing countries, rather than a public health challenge. This study was performed to identify Fasciola sp. from different definitive hosts (buffalo, cattle, and sheep) based on the molecular parameters and spermatogenesis. Ninety-one adult flukes were collected from livers of slaughtered animals at abattoirs in different prefectures in Egypt. Microscopic examination of the analyzed flukes showed many normal spermatozoa in the seminal vesicles (spermic), suggesting that they have the ability of spermatogenesis. This study showed that no parthenogenic Fasciola species occurred in Egypt. Molecular analysis was performed utilizing genomic (ITS1 and ITS2) and mitochondrial (NDI and COI) gene markers. Whereas 16 animals proved to have infection with a single Fasciola species, 2 were infected with both F. hepatica and F. gigantica. The results indicated that sheep were prone to F. hepatica (8 out of 10 animals) more than F. gigantica infection. Sequences of ITS1 and ITS2 ribosomal region indicated that the flukes were categorized into 3 groups F. hepatica-type (47), F. gigantica-type (42) and 2 flukes possessed sequences of both types indicating an existence of different alleles at the same loci. Unique overlapping of T/C bases were detected in both ITS1 (Position 96) and ITS2 (Position 416). Based on results of mitochondrial gene markers (NDI and COI), flukes were classified into F. hepatica-type and F. gigantica-type. Extensive intra-sequence polymorphism was detected at both markers. NDI and COI sequences of Egyptian strain of F. gigantica showed pronounced diversity compared with relevant sequences at database.     

DNA-based identification of a hepatic trematode in an elk calf

Liver fluke infection was identified as a probable cause of clinical disease in an approximately 6-mo-old elk (Cervus elaphus) in coastal Oregon. Clinical pathology and necropsy findings are described. The alcohol-fixed flukes that were submitted for identification were similar in size to Fasciola hepatica, but their shape resembled Fascioloides magna in that they lacked a distinctive anterior cone. A few structures consistent with the eggs of F. magna were observed in liver lesions, suggesting that at least some of the worms were sexually maturing. Due to difficulties in morphologic identification associated with improper fixation technique, DNA analysis was used to compare small subunit (SSU) and internal transcribed spacer 2 ribosomal RNA gene sequences of the recovered parasites with those of F. hepatica and F. magna, confirming these small, but sexually mature flukes were F. magna. This is the first publication of the SSU gene sequence for F. magna. Phylogenetic analysis showed that it is related to, but is an outlier, to the genus Fasciola. Due to the high mortality rate associated with this disease outbreak, the overall significance of trematodiasis in the herd is unclear.     

An ultrasensitive capture ELISA for detection of Fasciola hepatica coproantigens in sheep and cattle using a new monoclonal antibody (MM3)

A capture enzyme-linked immunosorbent assay (ELISA) using a new monoclonal antibody (mAb MM3) is reported for the detection of Fasciola hepatica excretory-secretory antigens (ESAs) in feces of infected hosts. The mAb MM3 was produced by immunization of mice with a 7- to 40-kDa purified and O-deglycosylated fraction of F. hepatica ESAs, which has previously been shown to be specific for the parasite. The specificity and sensitivity of the MM3 capture ELISA were assessed using feces from sheep and cattle. Sheep feces were obtained from a fluke-free herd (with most animals harboring other nematodes and cestodes), from lambs experimentally infected with 5-40 F. hepatica metacercariae and in some cases treated with triclabendazole at 14 wk postinfection (PI), and from uninfected control lambs. Cattle feces were collected at the slaughterhouse from adult cows naturally infected with known numbers of flukes (from 1 to 154) or free of F. hepatica infection (though in most cases harboring other helminths). The MM3 capture ELISA assay had detection limits of 0.3 (sheep) and 0.6 (cattle) ng of F. hepatica ESA per milliliter of fecal supernatant. The assay detected 100% of sheep with 1 fluke, 100% of cattle with 2 flukes, and 2 of 7 cattle with 1 fluke. The false-negative animals (5/7) were probably not detected because the F. hepatica individuals in these animals were immature (5-11 mm in length). As expected, coproantigen concentration correlated positively (r = 0.889; P < 0.001) with parasite burden and negatively (r = 0.712; P < 0.01) with the time after infection at which coproantigen was first detected. Nevertheless, even in animals with low fluke burdens (1-36 parasites), the first detection of F. hepatica-specific coproantigens by the MM3 capture ELISA preceded the first detection in egg count by 1-5 wk. In all sheep that were experimentally infected and then untreated, coproantigen remained detectable until at least 18 wk PI, whereas in sheep that were experimentally infected and then flukicide treated, coproantigen became undetectable from 1 to 3 wk after treatment. None of the fecal samples from sheep or cattle negative for fascioliasis but naturally infected with other parasites including Dicroelium dendriticum showed reactivity in the MM3 capture ELISA. These results indicate that this assay is a reliable and ultrasensitive method for detecting subnanogram amounts of F. hepatica antigens in feces from sheep and cattle, facilitating early diagnosis.     

Fascioloides magna (Bassi, 1875) in feral swine from southern Texas.

Between 1971 and 1975, Fascioloides magna was found in 46 of 67 (69%) feral swine (Sus scrofa) in southern Texas. Flukes were recovered from swine in areas where F. magna commonly has been recovered from white-tailed deer and cattle. One to 12 flukes were recovered from each infected animal. Their presence was indicated by black hematin pigment on the liver and various other internal organs. Eggs were not detected in the gallbladder or feces of infected animals although mature flukes and eggs were recovered in the livers suggesting that, like cattle, feral swine can be infected but are aberrant hosts for the parasite and do not disseminate eggs.     

Fasciola hepatica: site of resistance to reinfection in cattle

The effective site of resistance to reinfection of cattle with Fasciola hepatica was examined by recovery of challenge flukes from either the liver or body cavity. Calves infected 18 or 26 weeks previously with F. hepatica showed levels of resistance to reinfection of 56 and 94%, respectively, as assessed by recovery of flukes from the liver 15-16 weeks after challenge. Plasma glutamate dehydrogenase (EC 1.4.1.3; GLDH) enzyme activity estimations revealed only a marginal increase in these latter resistant calves compared with previously naive controls, indicating minimal liver damage as a result of migrating flukes. By comparison, when immature challenge flukes were recovered from the body cavity 4 or 14 days after infection of corresponding previously infected or naive calves, there was no significant difference in numbers. It appears, therefore, that, in cattle, resistance mechanisms are effective against challenge flukes at or soon after penetration of the liver.     

Parasiticidal effects of peroxynitrite on ovine liver flukes in vitro

Peroxynitrite (ONOO-) is a cytotoxic anion, produced by interaction between nitric oxide and superoxide in vivo in some inflammatory cells. This study investigated its effects on Fasciola hepatica and Dicrocoelium dendriticum isolated from ovine livers and kept in bile at room temperature. Peroxynitrite was synthesized using a quenched flow reactor and assayed spectrophotometrically. It was applied at different concentrations (10(-3.5) to 10(-2.3 M)) to the flukes kept in bile. The viability of the peroxynitrite-treated flukes was compared with a control group (n=5-7 per group). Control F. hepatica and D. dendriticum lived for 226+/-11and 208+/-14min, respectively. Life times were decreased by peroxynitrite at all concentrations used (P<0.001). At the highest concentration of peroxynitrite, F. hepatica and D. dendriticum lived only for 6.1+/-0.4 and 4.1+/-4.1+/-0.2min, respectively. Correlation between peroxynitrite concentration and parasite viability was significant in the case of F. hepatica (r= -0.842; P= 0.0035). A single application of peroxynitrite can decrease the life span of ovine liver flukes. A failure in the activation of hepatic macrophages in infected animals may lead to a decreased production of free radicals and, thus, peroxynitrite. Such a failure is likely to deprive the body of a defence tool against multicellular parasites.     

Experimental cross infections of Fasciola hepatica in lambs and calves.

The effects of experimental infections with Fasciola hepatica of ovine and bovine origin in homologous and heterologous hosts and in uninfected controls were compared; groups comprised 5 animals each. The effects of the infections were monitored by biweekly determinations of packed cell volumes (PCV), serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), gamma glutamyl transpeptidase (GGT), serum iron, bilirubin levels, alkaline phosphatase (AlP) and total serum protein levels. Infected animals showed changes in SGOT, SGPT and GGT activity levels, and GGT activity levels, and infected lambs showed changes in PCV and AlP. However, no no significant differences in these serum levels between infected host groups were attributable to fluke strain. At necropsy, calves infected with ovine and bovine strains on an average had about the same number of flukes, but lambs infected with a high dose of the bovine strain on the average had nearly twice the number of flukes as those infected with ovine strain. Weight gains did not differ within host groups; liver damage was extensive in all infected animals. On the basis of these experiments, the pathogenicity of the ovine and the bovine strains of F. hepatica appears to be the same.     

Hepatic fibrosis and Fasciola hepatica infection in cattle

This study focuses on the development of fibrosis of the liver of cattle with Fasciola hepatica infection, correlating with the intensity of infection. Animals with an established diagnosis of chronic F. hepatica infection were identified in a slaughterhouse in Lima, Peru. The study included 24 fresh cattle livers from infected animals and two uninfected controls. Tissues were stored at 4 degrees C for approximately 8 h after which they were brought to a necropsy room and examined. Between 9 and 12 biopsies were randomly obtained from each liver. Histological staining of formalin-fixed liver sections with haematoxylin and eosin (H & E) and Masson's trichrome were performed. Liver samples were examined using a pathology protocol that included 30 items. Histopathologically, 16 out of 30 liver specimens (67.6%) showed diffuse fibrotic lesions (cirrhosis) with a mean number of Fasciola of 116 +/- 30 (range 4-435). Pathological data were matched to number of adult parasites and presence of cirrhosis after being reviewed by two independent pathologists. There was concordance between the two pathologists (K = 0.72). The group with cirrhosis showed an average of 116 +/- 30 adult parasites whereas the group not showing cirrhosis contained 56 +/- 28 flukes (P = 0.2). To measure how number of flukes and diagnosis of cirrhosis are related we used Kendall's tau-b coefficient; the correlation was +0.296 (P = 0.04). Receiver Operating Characteristic (ROC) curve results showed that the best point was 38 parasite adults, which had 93.8% sensitivity and 75% specificity. We conclude that as the number of F. hepatica adult forms increases, the likelihood of developing liver fibrosis will also increase in cattle.     

Aspects of the maintenance of the life cycle of Fasciola hepatica in Lymnaea columella in Minas Gerais,Brazil

Fascioliasis is a parasitic disease of domestic ruminants that occurs worldwide. The lymnaeid intermediate hosts of Fasciola hepatica include Lymnaea columella, which is widely distributed in Brazil. A colony of L. columella from Belo Horizonte, MG, was reared in our laboratory to be used in studies of the F. hepatica life cycle, the intermediate host-parasite relationship and development of an anti-helminthic vaccine. In the first experiment 1,180 snails were exposed to miracidia of F. hepatica eggs removed from the biliary tracts of cattle from the State of Rio Grande do Sul. In the second and third experiments the snails were exposed to miracidia that had emerged from F. hepatica eggs from Uruguay, maintained in rabbits. The rates of infection in the first, second and third experiments were 0, 42.1 and 0% respectively. Over 15,806 metacercariae were obtained and stored at 4 degrees C. Four rabbits weighing 1.5 kg each were infected with 32-44 metacercariae and two with 200. Three rabbits begin to eliminate eggs of the parasite in the feces from 84 days after infection onwards. The biological cycle of F. hepatica in L. columella and the rabbit was completed within 124 days.     

Eimeviu (Protozoa: Coccidia) in wild populations of some British rodents

Four species of wild rodents from the British Isles, Myocustor coypus (the Coypu), Apodemus sylvaticus (the Wood mouse). Mus musculus (the House mouse) and Clethrionomys glureolus (the Bank vole) were examined during 1918 and 1919 for the presence of coccidian parasites of the genus Eimeriu. From an examination of 852 faecal samples a total of 14 species of Eimeriu was found. Species identification was based mainly on the morphology of the sporulated oocyst. The number of host species examined and the overall prevalence of infection were as follows: 252 M. coypus (45·6% infected), 471 A. sylvaticus 56·5%), 59 M. musculus (42·4%) and 70 C. glureolus (22·9%). The results are compared with previous surveys and discussed in the light of the general knowledge concerning coccidial infections. The present work showed that prevalence of infection in the wild rodents studied may be influenced by the age, weight and sex of the host, and by season.     

Patterns in size and shedding of Fasciola hepatica eggs by naturally and experimentally infected murid rodents

Using samples collected on the island of Corsica, a comparative study was done of the morphometry of Fasciola hepatica eggs shed by cattle and by naturally and experimentally infected murid rodents (wild Mus musculus and Rattus rattus and Rattus norvegicus Wistar laboratory strain). Eggs shed by murids are smaller in size than those shed by naturally infected cattle. A second study analyzed the number of F. hepatica eggs shed in murid feces at different time intervals, i.e., months, days, and 6-hr periods, by the Kato-Katz technique. Both experimentally and naturally infected black rats (R. rattus) were used, and Wistar rats were experimentally infected and included for comparison. The present studies prove that black rats R. rattus are able to shed eggs independently from the liver fluke isolate and that egg shedding occurs throughout the life of this host species, uninterrupted during all the months analyzed in a 2-yr period. Moreover, the results suggest that this shedding is continuous, with eggs appearing in the feces daily. The results on egg shedding by wild black rats R. rattus reach their maximum shedding in spring and autumn and a maximum during twilight hr. These chronobiological patterns appear to favor parasite transmission, both seasonally and daily.     

Liver enzymes and blood metabolites in a population of free-ranging red deer (Cervus elaphus) naturally infected with Fascioloides magna

We investigated the effects of Fascioloides magna infection on the serum biochemistry values of the naturally infected red deer population in eastern Croatia. The investigation was performed on 47 red deer with F. magna infection confirmed patho-anatomically in 27 animals (57.4%). Fibrous capsules and migratory lesions were found in 14 deer while only fibrous capsules without migratory lesions were found in 13 deer. In 13 deer both immature and mature flukes were found, in 5 deer only immature flukes were found and in 9 deer only mature flukes were found. Fascioloides magna infected deer with fibrous capsules and migratory lesions had significantly higher values for lactate dehydrogenase (LDH), glutamate dehydrogenase (GLDH) and globulin, and lower values for albumin/globulin ratio and glucose compared to uninfected deer. Fascioloides magna infected deer with fibrous capsules without the presence of migratory lesions had higher values for alanine aminotransferase (ALT) and globulin, and lower values for albumin/globulin ratio and glucose, than the uninfected deer. The number of immature flukes was positively correlated with values of aspartate aminotransferase (AST), γ-glutamyltransferase (GGT), LDH, GLDH, urea and triglycerides. The number of migratory lesions was positively correlated with GGT, GLDH, globulin and urea values. The creatinine value was positively correlated with the number of mature flukes. The trial showed that F. magna infection causes significant changes in serum biochemistry. Moreover, these changes do not completely resemble changes following F. hepatica infection. Further investigation of changes in liver enzymes and other serum metabolites in controlled, experimentally induced fascioloidosis in red deer is needed to better understand the pathogenesis of F. magna.     

Molecular identification of Fasciola spp. (Digenea: Fasciolidae) in Egypt

A total of 134 Egyptian liver flukes were collected from different definitive hosts (cattle, sheep, and buffaloes) to identify them via the use of PCR-RFLP and sequence analysis of the first nuclear ribosomal internal transcribed spacer (ITS1). Specimens of F. hepatica from France, as well as F. gigantica from Cameroon were included in the study for comparison. PCR products of ITS1 were subjected for digestion by RsaI restriction enzyme and visualized on agarose gel. According to RFLP pattern, Egyptian flukes were allocated into two categories. The first was identical to that of French hepatica flukes to have a pattern of 360, 100, and 60 (bp) band size, whereas the second resembled to that of Cameroonian gigantica worms to have a profile of 360, 170, and 60 bp in size. Results of RFLP analysis were confirmed by sequence analysis of representative ITS1 amplicons. No hybrid forms were detected in the present study. Taken together, this study concluded that both species of Fasciola are present in Egypt, whereas the hybrid form may be not very common.     

Development of Fasciola hepatica in Lymnaea columella infected with miracidia derived from cattle and marmoset infections

The development of Fasciola hepatica from two species of definitive hosts, i.e. cattle (Bos taurus) and a marmoset (Callithrix penicillata) in the snail Lymnaea columella was determined based on the production of rediae and cercariae and snail survival rate. More rediae and cercariae at 60-74 days post-infection were produced by snails infected by cattle-derived miracidia (cattle group) than by those infected by marmoset-derived miracidia (marmoset group). Among the L. columella parasitized by the marmoset group, the survival rate and the percentage of positive snails were higher than among those parasitized by the cattle group. Eggs of F. hepatica released in cattle faeces were significantly bigger than those released in marmoset faeces. Miracidia originating from parasites that completed their development in cattle were more efficient in infecting the intermediate host. These results suggest that vertebrate-host origin influences the eggs produced by the parasite and the infection rates in the snail host L. columella.     

The stimulation of resistance in sheep to Fasciola hepatica by infection with Cysticercus tenuicollis

Infection of sheep with Cysticerus tenuicollis for 12 weeks generated a high level of protection (> 95%) against intra-ruminal challenge with metacercariae of Fasciola hepatica as measured by recovery of flukes from liver and bile ducts and counts of fluke eggs in faeces. The animals were resistant to Fasciola whether challenge was superimposed upon the cestode infection or after removal of the cestode with mebendazole.Previous infection with C. tenuicollis also protected against the pathogenic effects of challenge infection with F. hepatica. Liver fibrosis was much less extensive in resistant sheep than controls and PCV's were not affected although these were reduced during fluke infection in the control animals.     

Fasciola hepatica: host responders and nonresponders to parasite glutathione S-transferase.

Fasciola hepatica glutathione S-transferase (FhGST) was isolated from adult worms by glutathione agarose affinity chromatography. SDS-PAGE shows three proteins of M(r) ranging from 29-27.8 kDa. Western immunoblot analyses using SDS-PAGE separated adult worm extracts and probed with a rabbit anti-FhGST antiserum reveal two bands in the same M(r) range. Mice and rabbits immunized with purified FhGST develop copious amounts of anti-FhGST antibodies. Moreover, antisera to F. hepatica adult worms and excretion-secretion products also react with FhGST. Cross-reactivity with schistosomes is evidenced in the reactivity with FhGST of anti-Schistosoma mansoni adult worm antisera and, to a lesser extent, antisera to S. mansoni-soluble egg antigens. The time of appearance of anti-FhGST antibodies in different species of animals infected with F. hepatica was determined. Sheep and a New Zealand white rabbit developed anti-FhGST antibodies detectable by ELISA as early as 2 weeks postexposure with F. hepatica. However, neither mice nor calves infected with F. hepatica developed antibodies to FhGST through the 5-10 weeks of infection tested. But mice infected with S. mansoni developed anti-FhGST cross-reacting antibodies by 6 weeks of infection. Calves immunized with a Fasciola/Schistosoma cross-reactive, cross-protective antigen complex in which a 12,000-kDa protein (Fh12) has been shown to contain immunoprophylactic activity, also developed antibodies to FhGST. Since FhGST is a novel potential vaccine, its protection-inducing capability in a multivalent vaccine combined with Fh12 clearly warrants study. In summary, it appears that hosts with fascioliasis are either responders to FhGST (rabbits, sheep) or nonresponders (mice, cattle), offering interesting models for studying the immune response.     

The metabolic profile of adult Fasciola hepatica obtained from rafoxanide-treated sheep.

Sheep infected with adult Fasciola hepatica were drenched with rafoxanide. At 4, 8, 16 and 24 h after drenching the sheep were killed and the flukes removed, washed and rapidly frozen in liquid nitrogen. The content of key metabolites in the fermentation pathway were determined and compared with those in control F. hepatica, whose hosts were not treated with rafoxanide. Rafoxanide decreased glycogen, malate, NADH and ATP levels. The level of other metabolites in the pathway increased for the first 8-16 h after rafoxanide treatment. The marked decrease in ATP and glycogen, and the increase in total [NAD+]/[NADH] and [oxaloacetate]/[malate], together with the changed content of other metabolites, led to the conclusion that the mode of action of rafoxanide against F. hepatica in vivo is by uncoupling oxidative phosphorylation.     

Mixed infections with Opisthorchis viverrini and intestinal flukes in residents of Vientiane Municipality and Saravane Province in Laos

Faecal examinations for helminth eggs were performed on 1869 people from two riverside localities, Vientiane Municipality and Saravane Province, along the Mekong River, Laos. To obtain adult flukes, 42 people positive for small trematode eggs (Opisthorchis viverrini, heterophyid, or lecithodendriid eggs) were treated with a 20-30 mg kg(-1) single dose of praziquantel and purged. Diarrhoeic stools were then collected from 36 people (18 in each area) and searched for helminth parasites using stereomicroscopes. Faecal examinations revealed positive rates for small trematode eggs of 53.3% and 70.8% (average 65.2%) in Vientiane and Saravane Province, respectively. Infections with O. viverrini and six species of intestinal flukes were found, namely, Haplorchis taichui, H. pumilio, H. yokogawai, Centrocestus caninus, Prosthodendrium molenkampi, and Phaneropsolus bonnei. The total number of flukes collected and the proportion of fluke species recovered were markedly different in the two localities; in Vientiane, 1041 O. viverrini (57.8 per person) and 615 others (34.2 per person), whereas in Saravane, 395 O. viverrini (21.9 per person) and 155207 others (8622.6 per person). Five people from Saravane harboured no O. viverrini but numerous heterophyid and/or lecithodendriid flukes. The results indicate that O. viverrini and several species of heterophyid and lecithodendriid flukes are endemic in these two riverside localities, and suggest that the intensity of infection and the relative proportion of fluke species vary by locality along the Mekong River basin.     

Comparative population dynamics of the bug Mepraia spinolai, a sylvatic vector of Chagas' disease, in different hosts

Abstract.  The aim of this work was to determine the impact of specific hosts on a population of Mepraia spinolai (Porter) (Hemiptera, Reduviidae), a sylvatic vector of Chagas' disease in Chile. We assessed whether a recently introduced host could be an important epidemiological factor in maintaining Chagas' disease in Chile. The study stressed the variations in survival, individual weight and fecundity in the insect population when the vector was raised with a species-specific food supply. The study compared the European rabbit Oryctolagus cuniculus , introduced in Chile ≤ 150 years ago, with a wild endemic rodent, Octodon degus . Hosts were placed separately in experimental glass chambers. Groups of insects maintained with rabbits had greater fecundity than those raised with rodents, but both groups had similar survival times and average weights. Both O. degu s and the European rabbit appear to be suitable hosts for M. spinolai , but the rabbit is better than the rodent. Additional research is needed to determine which factors of O. cuniculus produce the observed results.