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[The cultivation of Fossaria cubensis (Pfeiffer) (Pulmonata: Lymnaeidae), the intermediate host of Fasciola hepatica (Linnaeus) in Cuba].

A method for the culture of Fossaria cubensis (Pfeiffer), the major intermediate host of fascioliasis in Cuba, was assessed. For this purpose, an algae-bearing plate was designed based on a culture of Cyanophyceae algae from Lyngbya, Leotolyngbya, Phormidium, and Schimidleinema on Petri plates 12 cm in diameter with mud substrate and high levels of nitrate and calcium carbonate. Fifteen days after incubation with continuous light, these plates were used as aquaria for mollusc breeding. Under such conditions the generational time is reduced and the growth and reproduction of Fossaria cubensis which allow for their mass production aimed at the research of fascioliasis is guaranteed.

Animals↗

Fasciola hepatica: liver microsomal membrane functions in host rat.

Changes in different microsomal membrane functions were measured in the liver of rats 3, 6, or 9 weeks following an oral infection with 20 metacercariae of Fasciola hepatica. The parasitic pathology noted at autopsy was accompanied by increased levels in both plasma aspartate aminotransferase (EC 2.6.1.1) and microsomal gamma-glutamyltransferase (EC 2.3.2.2). Heme oxygenase activity of microsomes was significantly decreased by Weeks 3 and 6 postinfection and this decrease correlates with those of total microsomal cytochrome P450 and certain P450-dependent monooxygenase activities, namely, benzphetamine demethylation, ethoxycoumarin deethylation, and benzopyrene hydroxylation. Microsomal epoxide hydrolase (EC 3.3.2.3) was only altered 6 weeks after the infection. During the early stages of the parasitism, there were decreases in both microsomal calcium uptake and calcium ATPphosphohydrolase activity (EC 2.6.1.1), whereas membrane fluidity, estimated by the order parameter S, was lower in the infected rats than that in the controls. These alterations could be related to the already described increase in liver cytosolic calcium or lipid peroxidation which occurs in experimental fascioliasis.

Animals↗

A PCR-RFLP assay for the distinction between Fasciola hepatica and Fasciola gigantica.

Fascioliasis is of well-known veterinary importance and an increasing human health problem, with reported cases in the five continents. The causative agents, Fasciola hepatica and Fasciola gigantica, present geographical distributions, which overlap in many regions of Africa and Asia, and in which the differentiation of both species is usually difficult because of the many variations in their morphological characteristics. Moreover, in humans, liver fluke classification cannot be achieved by clinical, pathological, coprological or immunological methods. The differential diagnosis between F. hepatica and F. gigantica infection is very important because of their different transmission and epidemiological characteristics. A simple and rapid PCR-restriction fragment length polymorphism (RFLP) assay, using the common restriction enzymes Ava II and Dra II, is described to distinguish between both fasciolid species. It is based on a 618-bp-long sequence of the 28S rRNA gene recently obtained from liver fluke populations of South America, Europe and Africa. This sequence showed a few nucleotide differences between both fasciolids and no intraspecific variations within each species. This assay provides unambiguous results and may be useful for both individual subject diagnosis and epidemiological surveys of humans and animals in endemic regions of sympatry.

Animals↗

[The rabbit as a reservoir host of Fasciola hepatica? (author's transl)].

Following field observations, the ability of Fasciola hepatica to develop in domestic rabbits as compared with sheep was investigated under experimental conditions. The results indicate the development of F. hepatica is impaired in various phases after rabbit passage. Only 4.2 percent of the metacercariae gained after one rabbit passage developed to adult F. hepatica in sheep, whereas the respective percentage after sheep passage was 51.2 percent. It can be calculated that after rabbit passage 4.5 liver flukes develop from 100 F. hepatica eggs as compared with 2,141.3 parasites after sheep passage. The result justify the assumption that rabbits may play only a minor role in the epidemiology of fascioliasis.

Animals↗

Clinical diagnosis of schistosomiasis in Sudanese cattle.

This study was done in the White Nile Province to characterise the history and signs of naturally occurring Schistosoma bovis infection in cattle (Gorag). Necropsy and laboratory examinations were performed on 10 animals six to 30 months of age which were in poor condition. They were selected because of a history suggestive of schistosomiasis. All the animals showed some degree of S. bovis infection; eight had a moderate or heavy degree of infection. Also all had liver damage due to either past or active Fasciola gigantica infection. Although concurrent infection with these two trematodes is common an owner who diagnoses Gorag is most likely referring to the syndrome caused by S. bovis as being the major cause of the poor performance observed. Fasciolicide treatment may eliminate active fascioliasis as the principal damaging agent. Also differentiating signs of haemorrhagic diarrhoea, severely sunken eyed appearance and only moderate inappetence are common in animals with acute schistosomiasis.

Animals↗

Liver fluke infections of cattle in Mali. An abattoir survey on prevalence and geographic distribution.

Six hundred and ninety two cattle, slaughtered in various abattoirs in Mali between August 1983 and November 1984 were examined for evidence of Fasciola gigantica and Dicrocoelium hospes infections. A great variation in geographic prevalence was observed. Sufficient knowledge was acquired to demonstrate both the importance of fascioliasis in some areas and also the high prevalence of D. hospes in other areas. We suggest that the difference in prevalence from one geographic area to another is influenced by local climatic conditions, presence or absence of rivers and lakes, and differences in livestock management practices by various ethnic groups.

Animals↗

Developmental differences in the uterus of Fasciola hepatica between livestock liver fluke populations from Bolivian highlands and European lowlands.

A morphometric study of the uterus area (UA) of Fasciola hepatica adults was carried out with the aid of a computer linked to a stereomicroscopic 3CCD colour video camera using image analysis software. The UA of adult liver flukes found in naturally infected sheep, cattle and pig from the endemic human fascioliasis zone of the northern Bolivian Altiplano highlands was compared with that of flukes found infecting sheep and cattle from Valencia, Spain and cattle from Corsica, France (collectively, European lowlands). Liver fluke UA was examined using an allometric model. A comparison of the allometry of the liver fluke UA in different host species from Bolivia revealed no significant differences. Similarly, no statistically significant differences were found between UA of Valencian and Corsican populations. However, the Bolivian sheep and cattle liver fluke populations proved to have a UA smaller than that of the European populations. These results indicate differences between the liver fluke population of highlands and lowlands, regarding UA. This paper discusses the possible relationship between the characteristic of having a reduced uterine development and the liver fluke adult stage adapting to host populations living at very high altitudes.

Altitude↗

Behavioural responses of the snail Lymnaea acuminata to carbohydrates in snail-attractant pellets.

Snail control is one of the most important tools in the campaign to reduce the incidence of fascioliasis. In order to attain this objective, the method of bait formulation in order to contain an attractant and a molluscicide is an expedient approach to lure the target snail population to the molluscicide. This study identifies certain carbohydrates, namely sucrose, maltose, glucose, fructose and starch, for preparing such baits. These were tested on Lymnaea acuminata, an intermediate host of the digenean trematodes Fasciola hepatica and Fasciola gigantica. The behavioural responses of snails to these carbohydrates were examined. Significant variations in behavioural responses were observed in the snail even when the five carbohydrates were used in low concentrations in snail-attractant pellets. Starch emerged as the strongest attractant for Lymnaea acuminata, followed by maltose.

Agar↗

Expression and cross-species reactivity of fatty acid-binding protein of Clonorchis sinensis.

Clonorchis sinensis is a Chinese liver fluke that chronically resides in the biliary tract. The fatty acid-binding protein (FABP) is known to play an important role in the intracellular transport of long-chain fatty acids that are obtained by the fluke from the host. Although FABP has stimulated considerable interest as a vaccine target candidate, the nature of FABP from C. sinensis (CsFABP) remains unclear. In this paper, we describe the cloning and expression of recombinant FABP and immune cross-reaction by Western blot analysis. Sequence analysis revealed that the CsFABP cDNA contained a single open reading frame (ORF) coding for 134 amino acids with an estimated molecular mass of a 15.2 kDa. The DNA sequence of CsFABP cDNA showed significant homology to schistosome cytosolic FABPs, with a 49% amino acid sequence identity and 89% similarity to Schistosoma japonicum. This DNA also showed a high sequence similarity at the amino acid level to S. mansoni (Sm14; 83%) and Fasciola hepatica (80%). The CsFABP cDNA was cloned into expression vector pET28a, expressed in Escherichia coli and the recombinant protein purified by affinity chromatography. The recombinant CsFABP was cross-reacted with sera obtained from patients with fascioliasis and paragonimiasis. These results suggest that CsFABP may be useful as a vaccine for clonorchiasis.

Amino Acid Sequence↗

Humoral and cellular immune responses to experimental Fasciola hepatica infections in goats.

Humoral and cellular immune responses to Fasciola hepatica excretory-secretory products (ESPs) in primary and secondary experimental infections in goats were studied. Primary infection induced the development of chronic subclinical fascioliasis that did not affect the establishment of flukes coming from the secondary infection, as the same percentages of recovered flukes were found in both groups. The specific IgG response to F. hepatica ESPs was similar in primary and secondary infections; challenge flukes did not induce any modification in the IgG response. The specific lymphocyte response to F. hepatica ESPs was absent in most of the infected goats, both primarily and secondarily infected. A modulation of the nonspecific cellular responses to mitogens was also observed. All infected goats showed a reduced proliferative response to concanavalin A and phytohemagglutinin. According to our results, humoral and cellular responses to F. hepatica ESPs in goats have no protective effect on the establishment of flukes and the development of disease in either primary or secondary infections.

Animals↗

Fasciola hepatica development in the experimentally infected black rat Rattus rattus.

The finding of natural infection of Rattus rattus by Fasciola hepatica on Corsica has stimulated further research into the role of the black rat in the epidemiology of fascioliasis. Corsican black rats were experimentally individually infected with 20 metacercariae from cattle and murine isolates obtained from naturally infected bovines and black rats. The following results were obtained: (a) in R. rattus infected with the cattle isolate, normal adult fluke development took place and infection persisted for a long period, with emission of eggs showing embryogenic capacity; (b) the development of F. hepatica adults paralleled the ontogenetic trajectories observed in other rodent-F. hepatica models; and (c) fluke adults obtained in R. rattus infected with the murine isolate exhibited a similar pattern. These findings strongly suggest that the black rat may be one of the wild reservoirs of F. hepatica and may have contributed to the large geographical extent of the disease on Corsica.

Animals↗

Fasciola hepatica: collagen deposition and other histopathology in the rat host's bile duct caused by the parasite and by proline infusion.

Bile ducts were examined histochemically to compare the effects of proline infusion with Fasciola hepatica implantation in rats. After 3 weeks of infusion or implantation, both proline and F. hepatica produced increases in the luminal perimeter and collagen content of the bile duct. However, the effect of the parasite was significantly greater than that of proline, and the parasite produced significant increases in the bile duct wall. These results corroborate earlier biochemical and histological studies indicating the important role of proline in the enlargement of the bile duct in fascioliasis.

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.

Animals↗

Attempted immunisation of sheep against Fasciola hepatica using gamma-irradiated metacercariae.

The potential of gamma-irradiated Fasciola hepatica metacercariae to vaccinate sheep against fascioliasis was examined. The effect of the size of the inocula of irradiated metacercariae and the level of gamma-irradiation on the recovery of non-irradiated fluke was assessed following homologous challenge. Groups of Merino wethers were vaccinated with a single infection of either 500 or 2000 metacercariae, previously exposed to either 30, 100 or 400 Gy of gamma-irradiation. No significant reduction of fluke burdens were observed in any group, although a nonsignificant 20% reduction was observed in sheep vaccinated with 2000 metacercariae irradiated with 100 Gy. A second trial was conducted in which groups of sheep were vaccinated with 2 doses, given 4 weeks apart, of 2000 metacercariae, previously irradiated at either 70, 100 or 150 Gy. In both trials parasite viability was severely affected by doses of gamma-irradiation of 30 Gy or greater and no mature flukes were recovered from control sheep given metacercariae attenuated with 70 Gy or greater. A strong humoral immune response to somatic F. hepatica antigens was observed in all sheep. Only sera from sheep receiving 70 Gy irradiated metacercariae recognised the 2 candidate liver fluke vaccine molecules, F. hepatica glutathione S-transferase and cathepsin-L proteases. No reduction was observed in either the number of flukes or the production of fluke eggs in any vaccinated group. Vaccination appeared to affect the development of the challenge fluke population, resulting in reduced hepatic damage during migration, as measured by levels of serum glutamate dehydrogenase, and an increase in mean fluke weight.

Animals↗

Comparison of hepatic and extrahepatic drug-metabolizing enzyme activities in rats given single or multiple challenge infections with Fasciola hepatica.

The activity of drug-metabolizing enzymes was compared in liver, kidneys and lungs of rats given single or repetitive fluke infections. Fascioliasis was induced by oral administration of 20 metacercariae of F. hepatica to rats, either 6, or 12 and 6, or 12, 9 and 6 weeks before sacrifice. In the liver of mono-infected rats, significant reductions (24-67%) were observed in microsomal content of cytochrome P450 and all P450-dependent monooxygenases investigated. Conjugations to glutathione or acetate were lowered by 34-50% in these animals. In multiply infected animals, a majority of specific enzymatic activities were unchanged, while some monooxygenase activities such as aminopyrine demethylation or benzo(a)pyrene hydroxylation were increased by 26-76% in the liver of tri-infected rats. A renal compensatory process occurred in all infected groups, since cytochrome P450, benzphetamine demethylation and glutathione conjugation were significantly increased. By contrast, dealkylation of benzphetamine and pentoxyresorufin were decreased in the lungs of monoinfected rats. The development of parasite resistance would account for the recovery of liver drug metabolizing capabilities in multi-infected animals.

Animals↗

Immunoprecipitation of in vitro translation products of Fasciola hepatica RNA.

Incubation of in vitro translation products of RNA isolated from Fasciola hepatica with immune rat serum and sera from infected sheep resulted in the immunoprecipitation of a number of polypeptides, most of which had similar electrophoretic mobilities. Although only one of these (a 30 kDa species) correlated precisely in mobility with that of biosynthetically labelled excretory-secretory (ES) antigens, this polypeptide (along with several others) was also immunoprecipitated by sheep sera raised against authentic ES antigens. This verified that the isolated RNA contained mRNA species encoding ES antigens of the parasite. In addition, immune rat serum immunoprecipitated a 64 kDa polypeptide which was not immunoprecipitated by infected sheep serum or anti-ES antigen sheep serum. The possible significance of this finding in terms of the ability of rats to develop resistance to fascioliasis in contrast to sheep which apparently cannot is discussed.

Animals↗

Comparative efficacy of albendazole against Fasciola hepatica in sheep and calves: relationship to serum drug metabolite levels.

Calves were given albendazole (ABZ) daily in feed at levels of 0,3 or 5 mg kg-1 day-1. None of the ABZ treatment levels was significantly effective in reducing Fasciola hepatica burdens. A dose rate of 5 mg kd-1 day-1 did significantly reduce the fecal egg count. Measurements of serum drug levels from calves following a single dose of ABZ showed ABZ levels to be low, but sulfoxide and sulfone metabolites of ABZ were present in (significant) larger quantities. The total available sulfoxide present in calves, however, was much lower than in sheep receiving the same dose of ABZ. Measurements of serum metabolite levels from sheep and calves which were given daily low-level doses of ABZ also indicated that the serum sulfoxide levels of calves were much lower than those of sheep receiving the same ABZ dose. These results indicated that ABZ is not an effective prophylactic treatment for bovine fascioliasis and the differences in efficacy between sheep and cattle correlated with the differences in serum metabolite levels.

Albendazole↗

IgG response in natural and experimental infections of cattle with Fasciola gigantica.

A specific IgG response was detectable in serum and bile of cattle infected with Fasciola gigantica. Although there was an increase in both specific and total IgG concentration in the sera of fluke-infected cattle, there was no significant correlation between IgG1 concentration and the worm burden (r = 0.17; P greater than 0.05) in chronic fascioliasis. However, there was a highly significant correlation between the levels of IgG1 in the serum and bile of infected cattle (r = 0.87; P less than 0.01), indicating that the presence of IgG1 in the bile may be due to a leakage of serum antibody into the bile duct.

Animals↗