Cercarial tail loss in Echinostoma caproni: the influence of in vivo encystment and copper sulphate

Echinostoma caproni tail loss was studied in vitro in the presence of the toxicant copper sulphate (CuSO4) in concentrations ranging from 1 to 10 000 mg l(-1) in standardized artificial spring water (pH 7.4, osmolarity 34 mOsm kg(-1) H2O, Ca(2+) 20 mg l(-1)) at 23 degrees C. Tail loss was also studied in the absence of toxicants during in vivo encystment of the cercariae in juvenile Biomphalaria glabrata. As the concentration of CuSO4 increased, the percentage of cercarial tail loss increased. By 2 h in 10 000 mg l(-1), 1000 mg l(-1) and 100 mg l(-1) CuSO4, 50%, 23% and 13%, respectively, of the cercariae had lost their tails. In the in vivo studies, by 1 h PI, 59+/-5% of cercariae had lost their tails and only 4+/-1% of the cercariae were actively swimming in the multi-well dishes. At 3 h PI, 72+/-3% of the cercariae began to form cysts within the snails.

Effects of copper sulphate on in vitro encystment of the cercariae of Echinostoma caproni

The effects of various concentrations of copper sulphate were studied on in vitro encystment of Echinostoma caproni in a Locke's-artificial spring water (ASW) (1:1) medium. Cercariae were killed in 10,000 mg l(-1) CuSO4 in Locke's-ASW (1:1) within 24 h and extruded cystogenous material to produce an abnormal cyst wall. The 'emergency response' of encystment to high concentrations of copper reported for Parorchis acanthus cercariae did not occur in E. caproni. Concentrations of 1000 mg l(-1) and 100 mg l(-1) CuSO4 in Locke's-ASW (1:1) also killed the cercariae without encystment by 48 h. A concentration of 10 mg l(-1) CuSO4 in Locke's-ASW (1:1) allowed for normal in vitro encystment within 48 h and these cysts were capable of excystation in a trypsin-bile salts medium.

Effects of Schistosoma mansoni infection on inorganic elements in the snail Biomphalaria glabrata

Inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to study element ions in whole bodies of uninfected Biomphalaria glabrata snails and those experimentally infected with larval Schistosoma mansoni trematodes. Infected snails were analysed 8 weeks post-infection. Cohort snails that were left uninfected were analysed at the same time as the infected snails. Sixteen elements (aluminum, boron, barium, calcium, cadmium, copper, iron, potassium, magnesium, manganese, sodium, nickel, lead, selenium, tin and zinc) were found to be present in infected and uninfected whole bodies at concentrations above the detection limit of the ICP-AES analysis. Of these, calcium, cadmium, manganese and sodium were present in significantly higher amounts (Student's t-test, P<0.05) in whole infected versus whole uninfected snails. Variations in the present results compared with other studies reflect intrinsic differences in the larval trematode-snail systems used.

Effects of glucose on survival, infectivity and linear movement of the cercariae of Echinostoma caproni

The effects of glucose in artificial spring water (ASW) on the survival, infectivity, and linear movement of Echinostoma caproni cercariae were studied. Cercariae maintained at 23 degrees C in 1% glucose in ASW (ASWG) or ASW alone, reached 50% survival at 26 and 23 h, respectively. All cercariae in ASWG and ASW were dead by 50 and 32 h, respectively. Infectivity to juvenile Helisoma trivolvis (Colorado strain) snails was significantly less for cercariae aged 16 h in ASWG compared to cercariae aged 16 h in ASW. Linear movement, i.e. the ability of cercariae to traverse a 1-cm radius, ceased at 16 and 20 h for cercariae maintained in ASWG and ASW, respectively. Glucose added to ASW extended the survival time of E. caproni cercariae but decreased their ability to infect snails or move in a linear direction.

Effects of temperature on survival, infectivity and in vitro encystment of the cercariae of Echinostoma caproni

The effects of temperature on survival, infectivity and in vitro encystment of Echinostoma caproni cercariae in artificial spring water (ASW) were studied. Effects of aging cercariae in ASW at various temperatures showed that at 23 degrees C cercariae achieved 50% survival in 24 h, compared to 92 h at 12 degrees C. Cercariae aged in ASW at 28 and 37.5 degrees C showed 50% survival at 16 and 10 h, respectively. Cercariae aged at different temperatures for various times were used to infect juvenile Helisoma trivolvis (Colorado strain) snails maintained in ASW at 23 degrees C. Index of infectivity was based on counting encysted metacercariae in the snails at 8 to 12 h post-infection. Cercariae aged at 23, 28 and 37.5 degrees C showed 50% encystment at 6, 8 and 4 h, respectively. Cercariae aged at 4 degrees C showed 50% encystment in 10 h and cercariae aged at 12 degrees C showed 50% encystment beyond 16 h. Cercariae showed maximal longevity and infectivity in snails when aged at 12 degrees C in ASW. For E. caproni, as in other digeneans, the infective period of cercariae is markedly shorter than the maximal life-span at any given temperature. Studies on in vitro encystment of E. caproni cercariae in Locke's solution:ASW (1:1) showed that encystment was optimal at 23 degrees C (78% encystment) and that it declined to 44% at 28 degrees C and became almost nil (0.02%) at 12 or 37.5 degrees C.

Organization of the musculature of schistosome cercariae

Phalloidin-fluorescein isothiocyanate staining of filamentous actin was used to identify muscle systems within the cercariae of Schistosoma mansoni. Examination of labeled cercariae by confocal scanning laser microscopy revealed distinct organizational levels of myofiber arrangements within the body wall, anterior cone, acetabulum, and esophagus. The body wall throughout showed a typical latticelike arrangement of outer circular and inner longitudinal myofibers, with an additional innermost layer of diagonal fibers in the anterior portion of the body. Circular and longitudinal fibers were also evident in the anterior organ and esophagus and, to some extent, the ventral acetabulum. Most striking was the striation of the cercarial tail musculature.

Tegumentary papillae of Echinostoma caproni cercariae (Trematoda: Echinostomatidae)

Argentophilic staining and scanning electron microscopy were used to study the tegumentary papillae of Echinostoma caproni cercariae. The most abundant tegumentary papillae were uniciliate, but multiciliate papillae were also found, mainly on the ventral aspect of the oral collar. The distribution pattern of the papillae on the body and tail was in general similar to that seen in the cercariae of other 37-collar-spined Echinostoma species. Some differences were noted between E. caproni and the allopatric species, E. trivolvis. E. caproni has a greater number of papillae associated with the collar spines than does E. trivolvis. E. caproni has uniciliate papillae on the acetabulum, whereas E. trivolvis does not. Chaetotaxy is useful to distinguish subtle morphological differences in cercarial species in the 37-collar-spined Echinostoma complex.

Emergence of cercariae of Echinostoma caproni and Schistosoma mansoni from Biomphalaria glabrata under different laboratory conditions

Release of Echinostoma caproni cercariae and Schistosoma mansoni from experimentally infected Biomphalaria glabrata snails maintained under different laboratory conditions was studied. Infected snails were isolated individually for 1 h in Stender dishes containing 5 ml of artificial spring water and the number of cercariae released during this time was recorded. Of numerous conditions tested, the addition of lettuce, the use of water conditioned by B. glabrata snails and a temperature of 35 degrees C significantly increased the release of E. caproni cercariae. A significant increase in cercarial release of S. mansoni was seen only in cultures fed lettuce. A temperature of 12 degrees C caused a significant decrease in cercarial release of both E. caproni and S. mansoni. Increased snail activity associated with feeding behaviour was probably responsible for the enhanced cercarial sheds observed in this study.

Characterization of rural mental health service systems

This paper explores two mental health systems in rural North Carolina that provide services to people with severe mental disorders. Recent findings show rural people with mental disorders receive less mental health care than their urban counterparts. This study asks whether rural service systems differ from urban systems in the way that their services are coordinated and structured. A popular conception is that public mental health systems in the United States are uncoordinated with many services provided outside the mental health sector. Rural service providers are seen as even more dependent on nonspecialized mental health providers than their urban counterparts. While many rural service barriers are attributed to the rural environment, little is known about rural service systems and how their organization might contribute to or negate barriers to care. Social network methods were used in this study to compare two rural with four urban systems of care. Findings confirm that mental health systems fit the de facto hypothesis, but that rural systems differ in ways not anticipated by the hypothesis. Rather than being more dependent on nonmental health agencies, rural mental health agencies are more interdependent.

Biology of echinostomes except Echinostoma

This review examines the significant literature on the biology of echinostomes, except Echinostoma, for the following species rich genera: Echinoparyphium, Echinochasmus, Himasthla, and Hypoderaeum. Coverage of these genera includes descriptive studies, life cycle studies, experimental and manipulative studies, and biochemical and molecular studies. Coverage of other echinostome genera, i.e., Petasiger, Euparyphium, Stephanoprora, Isthmiophora, Acanthoparyphium, and Patagifer was mainly concerned with descriptive and life cycle studies. Some groups that are considered echinostome-like were covered because species in these genera have medical, economic, or biological significance (particularly Parorchis, Philophthalmus, and Ribeiroia). A dominant theme of the review is the availability of key species of echinostomes for use in biological research; coverage also includes methods for obtaining and maintaining these organisms in the laboratory. Some species with significant medical, veterinary, and biological importance that have been covered extensively include the Echinoparyphium recurvatum species complex, Echinochasmus liliputanus, Himasthla quissetensis, Himasthla rhigadana, and Hypoderaeum conoideum.

Effects of a 100 metacercarial cyst inoculum on the host-parasite relationship of Echinostoma caproni and ICR mice

The host-parasite relationship of a 100 metacercarial cyst inoculum of Echinostoma caproni in the ICR mouse was examined. Three groups of mice, A, B and C, each with six mice per group were used and all mice were necropsied at 14 days postinfection (p.i.), at which time the worms were ovigerous. Group A consisted of uninfected controls, whereas group B received 25 cysts per mouse (low dose) and group C received 100 cysts per mouse (high dose). There was no significant difference in food consumption between any of the groups from 0 to 14 days p.i. Control mice increased their body weight by 12%, group B by 5%, and group C showed a less than 1% increase in body weight between 0 and 14 days p.i. Echinostome parasitism caused a significant increase in the diameter of the mouse gut, with the gut of group C being more significantly dilated than that of either group A or B. The average worm recovery from group B was 20 worms per host, compared to 72 worms per host from group C. The mean wet and dry weights per worm from group B were 2.4 and 0.4 mg, respectively as compared to 0.6 and 0.2 mg respectively for group C. The mean number of uterine eggs per worm from group B was 180 compared to 125 for worms from group C. Worms from group C were more widely distributed in the small intestine than those from group B. Crowding effects associated with the high dose infection were clearly demonstrated in E. caproni from ICR mice.

Crepidula fornicata is not a first intermediate host for trematodes: who is?

Trematode larvae must generally invade a molluscan intermediate host, usually a gastropod, before they can reach reproductive maturity in another definitive host. The research literature to date has focused almost exclusively on the documented specificity between particular trematode species and particular molluscan hosts; little attention has been paid to gastropod species that do not appear to serve as hosts. We sampled Rhode Island and Massachusetts populations of the marine gastropod Crepidula fornicata to determine whether this widespread species serves as a first intermediate host for trematodes. We also sampled from the same habitat populations of Littorina littorea and Ilyanassa obsoleta, gastropods known to serve as first intermediate hosts for several trematode species. All individuals were examined by dissection for the presence of sporocysts, rediae, or developing cercariae. Although 4-28% of L. littorea (N=112) and I. obsoleta (N=84) were infected by larvae of at least one trematode species, no individuals of C. fornicata sampled from the same locations were so infected (N=136). A survey of the Biological Abstracts computer database indicates that snails in only about 10% of marine gastropod families are known to serve as first intermediate hosts for trematodes. We suggest that more attention be paid to marine gastropods that appear not to be infected by trematode miracidia. Such species may productively serve as new models for understanding trematode host specificity and gastropod resistance to infection.

Effects on the neutral lipid contents of the liver, ileum and serum during experimental schistosomiasis

During infection of vertebrate hosts with Schistosoma mansoni,worm eggs trapped in host tissues induce granulomatous lesions that interfere with normal organ functions. Even though both the liver and the intestine are particularly susceptible to egg-induced tissue damage, little information is available on the pathobiochemical changes induced in these organs during infection. Using a mouse model, we investigated whether the lipid profiles of the liver and ileum were altered significantly as a result of infection. We found that triacylglycerol and cholesteryl ester levels decreased significantly as infection progressed.

Effects of a diet deficient in the B complex vitamins on infectivity, growth and distribution of Echinostoma caproni in ICR mice

The effects of a diet deficient in the B vitamins on infectivity, growth, and distribution of Echinostoma caproni in ICR mice were studied. The vitamin-deficient diet (experimental) was isocaloric to the control diet but lacked the B vitamins. Thirty-six female, 6- to 8-week-old ICR mice were each infected with 25 metacercarial cysts. From the day of infection to the day of necropsy, 18 mice were fed the experimental diet and the remaining mice received the control diet. Equal numbers of experimental and control mice were necropsied at 2, 3 and 4 weeks postinfection (p.i.). Mice on the experimental diet showed a significant loss in body weight between 2 and 4 weeks p.i. There was no significant difference in worm recovery at 2 to 4 weeks p.i. from mice on either diet. Worms from hosts on the experimental diet were more dispersed and located more posteriad in the small intestine than those from mice on the control diet. Worm dry weight was significantly less in hosts on the experimental diet at all weeks p.i. compared with that of hosts on the control diet. The body area of worms on the experimental diet was significantly less at 2 and 3 weeks p.i. than that of worms on the control diet. An isocaloric diet deficient in the B vitamins had a detrimental effect on the growth of E. caproni in ICR mice.

Effects of diet on the development of Schistosoma mansoni in Biomphalaria glabrata and on the neutral lipid content of the digestive gland-gonad complex of the snail

In a previous study, when the snail Biomphalaria glabrata was infected with Schistosoma mansoni and maintained on a diet of hen's egg yolk, it produced fully developed cercariae in about one-half the time taken by snails fed Romaine lettuce. Increased lipids were also noted in the snails fed the yolk diet. The purpose of the present study was to further investigate nutritional effects of a high-lipid diet on larval schistosome development and to reexamine the time to cercarial patency in infected snails maintained on either the yolk or lettuce diet and to use high-performance thin-layer chromatography (HPTLC) to analyze the neutral lipids in the digestive gland-gonad complex (DGG) of snails maintained on both diets. Infected snails maintained at 26 C and fed either diet produced fully developed cercariae by 4 wk postinfection (PI). Likewise, infected snails maintained at 23 C and fed either diet produced fully developed cercariae by 6 wk PI. The contention that the yolk diet enhanced the time to cercarial patency was not confirmed. The HPTLC analysis of neutral lipids showed that the DGG of infected snails fed the yolk diet contained significantly greater amounts of free sterols and cholesteryl esters but not triacylglycerols than that of the infected snails fed the lettuce diet.

Fasciolopsiasis: is it a controllable food-borne disease?

Fasciolopsiasis, endemic to the Orient and Southeast Asia, is a snail-transmitted, intestinal, food-borne parasitic zoonosis caused by a trematode, Fasciolopsis buski, which also infects farm pigs. Fasciolopsiasis remains a public health problem despite changes in eating habits, alterations in social and agricultural practices, health education, industrialization, and environmental alterations. The disease occurs focally and is most prevalent in school-age children. In foci of parasite transmission, the prevalence of infection in children ranges from 57% in mainland China to 25% in Taiwan and from 50% in Bangladesh and 60% in India to 10% in Thailand. Control programs implemented for food-borne zoonoses are not fully successful for fasciolopsiasis because of century-old traditions of eating raw aquatic plants and using untreated water. Fasciolopsiasis is aggravated by social and economic factors such as poverty, malnutrition, an explosively growing free-food market, a lack of sufficient food inspection and sanitation, other helminthiases, and declining economic conditions.

Neutral lipids in cercariae, encysted metacercariae, and rediae of Echinostoma caproni

High performance thin-layer chromatography (HPTLC) was used to analyse the neutral lipids in the rediae, cercariae, and encysted metacercariae of Echinostoma caproni from Biomphalaria glabrata snails. Visual observations of the chromatograms showed that the most abundant lipid fraction in all stages was free sterol. Quantification of the free sterol revealed mean weights of 2.7 +/- 0.64 ng per redia, 0.53 +/- 0.023 ng per cercaria, and 0.081 +/- 0.0098 ng per encysted metacercaria. Oil Red O staining of the larval stages confirmed the presence of lipids within the rediae and cercariae but did not show lipids in the encysted metacercariae. The dimunition in neutral lipids from the cercarial to the encysted metacercarial stage does not support a previous observation that fat increases in successive phases of the digenean life cycle.

Neutral lipids in cercariae, encysted metacercariae, and rediae of Zygocotyle lunata

High-performance thin-layer chromatography was used to analyze the neutral lipids in the rediae, cercariae, and encysted metacercariae of the paramphistomid trematode Zygocotyle lunata. Visual observations of the chromatograms showed that the most abundant lipid fractions were free sterols and free fatty acids in all larval stages and triacylglycerols in the metacercariae and rediae. The weight of free sterols (x +/- SE) was 120+/-20 ng/cercaria, 56+/-3.8 ng/redia, and 5.9+/-1.5 ng/encysted metacercaria; the weight of triacylglycerols was 13+/-0.88 ng/encysted metacercaria, 6.3+/-0.063 ng/redia, and was not detectable in the cercaria; the weight of free fatty acids was 160+/-17 ng/ cercaria, 76+/-9.1 ng/redia, and 4.2+/-0.46 ng/encysted metacercaria. Oil red O staining of whole larvae showed the presence of neutral lipids in the rediae but not in the cercariae or encysted metacercariae. A dramatic reduction was seen in the quantity of free sterols and free fatty acids in the encysted metacercariae as compared with the cercariae, suggesting that these neutral lipids are used in some way during the transformation from cercaria to metacercaria.

Analysis of 16S rRNA and 51-kilodalton antigen gene and transmission in mice of Ehrlichia risticii in virgulate trematodes from Elimia livescens snails in Ohio

Operculate snails (the family Pleuroceridae: Elimia livescens) were collected between June and October 1998 from a river in central Ohio where repeated cases of Potomac horse fever (PHF) have occurred. Of collected snails, consistently 50 to 80% carried a combination of cercariae and sporocysts of digenetic virgulate trematodes. The trematodes obtained from each snail were pooled and tested for Ehrlichia risticii, the agent of PHF, by nested PCR using primers specific to the 16S rRNA gene. Out of a total of 209 trematode pools, 50 pools were found to be positive by PCR. The DNA sequence of the 16S rRNA gene identified in one trematode pool was identical to that of the type strain of E. risticii, and the sequence of the gene identified in another pool differed from that of the type strain by 1 nucleotide. Comparison of the deduced amino acid sequence of the partial 51-kDa antigen gene from various sources revealed that Maryland, Ohio (except Ohio 081), and Kentucky strains are in a cluster distinct from the sequences obtained from sources in California and Oregon. Ohio 081 was shown previously by antigenic composition analysis to be distinct from other groups. However, all sequences examined were not segregated according to their sources: horse blood or infected trematodes. E. risticii was found to be transmittable from trematodes to mice and was subsequently passaged from infected mice to additional mice, as determined by PCR analysis. Our findings suggest the evolution of E. risticii in the natural reservoir in separate geographic regions and persistent infection of trematode populations with E. risticii during summer and early fall. The study also suggests that the mouse can be used to isolate E. risticii from the infected trematode.

Postmetacercarial changes in Echinostoma caproni maintained in a defined medium plus calf serum

The present study examined postmetacercarial changes in the excysted metacercariae of Echinostoma caproni maintained in the defined medium Mixture 199 plus 20% calf serum for 7 days at 41 degrees C. The gas phase was atmospheric air. Each culture was inoculated with 25 excysted metacerariae. Cultures were maintained upright in closed 15 ml plastic centrifuge tubes each containing 10 ml of medium plus 200 units of penicillin/ml and 200 micrograms of streptomycin/ml. By 4 days in culture, most metacercariae had voided their excretory concretions. Organisms were clumped or solitary at the bottom of the cultures. Many organisms showed flaring of the oral collar and extension of both the collar and tegumentary spines. By 4 days in culture, posterior protuberances or bumps were noted on many of the organisms and some organisms showed abnormal vesicular growths or blebs at their posterior ends. Some mortality was noted in culture by day 5, but most organisms were still alive when the cultures were terminated on day 7.

High-performance thin-layer chromatographic analysis of lutein and beta-carotene in Cerithidia californica (Gastropoda) infected with two species of larval trematodes

High-performance thin-layer chromatography (HPTLC) analysis was done on lutein and beta-carotene in the digestive gland-gonad complex (DGG) and whole body of uninfected Cerithidia californica snails and those infected with the larval trematodes Mesostephanus appendiculatis or Euhaplorichis californiensis. HPTLC of the DGG extract on C-18 reversed-phase plates developed in petroleum ether-acetonitrile-methanol (1:2:2) mobile phase showed 2 identifiable pigment zones; the least polar zone had a retention factor (Rf) of 0.07, identical to a beta-carotene standard, and the more polar zone had an Rf of 0.41, identical to a lutein standard. Densitometric scanning of the pigment zones in sample versus standard chromatograms showed that the weight percent of lutein in the uninfected DGGs (3.4x10(-3)%) was significantly greater (P<0.05) than that of DGGs infected with either M. appendiculatis (0.35x10(-3)%) or E. californiensis (0.82x10(-3)%). Changes in beta-carotene in the infected DGGs were insignificant compared to the uninfected controls. However, the beta-carotene content of whole snails was significantly reduced (P<0.05) by infection with either trematode.

Immune responses during the acute stages of infection with the intestinal trematode Echinostoma caproni

This study investigated the nature of the immune response of C57BL/6 mice infected with the trematode Echinostoma caproni. To determine the preferential development of either a Th1 or Th2 cytokine pattern during early stages of infection, cytokine production by spleen and mesenteric lymph node (MLN) cells during the first 3 weeks of infection was followed. Whereas spleen cells failed to respond to antigen stimulation, MLN cells produced IFN-gamma and to a lesser extent IL-4. IL-5 levels were elevated throughout the period studied. The humoral response was consistent with a Th1 cytokine pattern as antigen-specific IgG2a antibodies were preferentially developed. We investigated whether IFN-gamma is critical for establishment of E. caproni infection. Worm burden in infected mice treated with a single injection of anti-IFN-gamma mAb was significantly reduced compared to that of animals treated with a control antibody.