Considering ivermectin for treatment of schistosomiasis

Because of recent reports of praziquantel resistance in schistosome infections, there have been suggestions to employ ivermectin as a possible alternative, especially as its chemical composition is different from that of praziquantel, so cross-resistance is not expected. In order to ascertain possible damage and elimination of worms, we used ivermectin by oral gavage in infected mice, at a high dose (30.1 mg/kg, bordering toxicity). We also tested the efficacy of the drug at various times postinfection (PI), to check on possible effect on young and mature stages of the parasites. Thus, we treated mice on days 21 and 22 or on days 41 and 42 and even on days 21, 22, 41, and 42 PI. None of the treatment regimens resulted in cure rates or signs of lessened pathology in the mice. We also compared the effect of ivermectin to that of artemisone, an artemisinin derivative which had served us in the past as an effective anti-schistosome drug, and there was a stark difference in the artemisone's efficacy compared to that of ivermectin; while ivermectin was not effective, artemisone eliminated most of the worms, prevented egg production and granulomatous inflammatory response. We assume that the reported lack of activity of ivermectin, in comparison with praziquantel and artemisinins, originates from the difference in their mode of action. In wake of our results, we suggest that ivermectin is not a suitable drug for treatment of schistosomiasis.

An improved medium for in vitro studies of female reproduction and oviposition in Schistosoma japonicum

BACKGROUND

Schistosomiasis is a disease primarily caused by eggs laid by pathogens called schistosomes. Among the schistosome species infecting humans, Schistosoma japonicum possesses the largest fecundity; each adult female produces an average of 3500 eggs per day. The lack of proper culture conditions supporting continuous oviposition in vitro has precluded detailed investigation of mechanisms regulating sexual maturation and egg production in Schistosoma japonicum.

METHODS

We optimized in vitro culture conditions by replacing reagents that are part of the classical ABC169 medium. Fast Blue BB staining and 4',6-diamidino-2-phenylindole (DAPI) labeling were applied to observe the sexual development status of the females. In vitro RNA interference (RNAi) technology was used to validate the capability of the modified medium. The detection of male β-alanyl-tryptamine (BATT) was conducted using liquid chromatography-mass spectrometry (LC-MS).

RESULTS

Both m-AB169 (1640) and AB169 (1640) media are capable of facilitating the sexual development of paired virgin female S. japonicum, as well as sustaining the mature reproductive organs and egg production of adult S. japonicum for at least 22 days in vitro. M-AB169 (1640) provided a more stable condition for supporting the sexual maturity of female S. japonicum, as evidenced by the consistent initiation of egg production compared with AB169 (1640). Through a comparative analysis of S. japonicum and S. mansoni in diverse media, we demonstrated that these closely related species display distinct demands for their sexual development and egg production, suggesting a potential influence of nutritional factors on the observed variations in host ranges among different schistosome species. Importantly, we successfully identified the presence of the pheromone β-alanyl-tryptamine (BATT) in S. japonicum, previously identified in S. mansoni, highlighting its conserved role in schistosome reproductive development. Through the employment of double-stranded RNA (dsRNA) treatment to silence two genes that are involved in either the male (gli1, glioma-associated oncogene homolog 1) or female (vf1, vitellogenic factor 1) side in male-induced female reproductive development of S. mansoni, we confirmed that the combination of m-AB169 (1640) and RNAi technology has the capacity to facilitate in vitro studies of S. japonicum's reproductive and oviposition processes.

CONCLUSIONS

We developed a novel medium, m-AB169 (1640), that not only maintains the mature reproductive organs and continuous oviposition of adult female Schistosoma japonicum for up to 22 days but also supports the reproductive development and subsequent egg-laying of virgin females after pairing with male worms. This study provides a valuable in vitro platform for functional studies of the mechanisms underlying the fascinating biology of the female sexual development and egg production of S. japonicum, which may accelerate the development of new strategies targeting schistosome egg production.

Progress in controlling the transmission of schistosome parasites in Southern Ethiopia: the Geshiyaro Project in the Wolaita Zone

BACKGROUND

This paper describes changes in the prevalence and intensity of schistosome parasite infections in a project integrating mass drug administration (MDA), water, sanitation, and hygiene (WaSH), and behavioral change interventions.

METHODS

The Geshiyaro Project comprises three intervention arms. Arm 1 is subdivided into "Arm 1 pilot" (one district) and Arm 1 (four other districts), both receiving integrated community-wide MDA with intensive WaSH interventions. Arm 2 involves 17 districts with community-wide MDA interventions, while Arm 3 serves as a control with school-based MDA interventions in three districts. A total of 150 individuals, stratified by age group, were randomly selected from each of the 45 sentinel sites. Arm sizes were 584 (Arm 1 pilot), 1636 (Arm 1), 2203 (Arm 2), and 2238 (Arm 3). Statistical tests were employed to compare infection prevalence and intensity across the different arms.

RESULTS

The prevalence of schistosome parasite infection ranged from 0% to 2.6% and from 1.7% to 25.7% across districts, employing the Kato-Katz (KK) and point-of-care circulating cathodic antigen (POC-CCA) diagnostics, respectively. The mean infection intensity level showed no marked difference between baseline and follow-up surveys when measured by KK, except in Arm 2 (t = 6.89, P < 0.0001). Infection prevalence decreased significantly in Arm 1 (t = 8.62, P < 0.0001), Arm 2 (t = 6.94, P < 0.0001), and Arm 3 (t = 8.83, P < 0.0001), but not in Arm 1 pilot (t = 1.69, P = 0.09) by POC-CCA, when trace was considered positive. The decrease was significant only in Arm 1 (t = 3.28, P = 0.0001) and Arm 2 (t = 7.62, P < 0.0001) when the trace was considered negative in POC-CCA. Arm 2 demonstrated a significant difference in difference (DID) compared to the control group, Arm 3, regardless of whether trace in POC-CCA was considered positive (DID = 3.9%, df = 8780, P = 0.025) or negative (DID = -5.2, df = 8780, P = 0.0004).

CONCLUSIONS

The prevalence of schistosomiasis was low when employing the KK diagnostic but moderate in some locations by the POC-CCA diagnostic. The infection level had decreased across all arms of the Geshiyaro study at mid-term of the 7-year project, but further efforts are needed to reduce the rate of parasite transmission based on the POC-CCA diagnostic scores.

Swimmer's itch control: Timely waterfowl brood relocation significantly reduces an avian schistosome population and human cases on recreational lakes

Swimmer's itch (SI) is a dermatitis in humans caused by cercariae of avian and mammalian schistosomes which emerge from infected snails on a daily basis. Mitigation methods for SI have long been sought with little success. Copper sulfate application to the water to kill the snail hosts is the historically employed method, but is localized, temporary, and harmful to many aquatic species. Here, we test an alternative method to control Trichobilharzia stagnicolae, a species well-known to cause SI in northern Michigan and elsewhere in North America. Summer relocation of broods of the only known vertebrate host, common merganser (Mergus merganser), greatly reduced snail infection prevalence the following year on two large, geographically separated lakes in northern Michigan. Subsequent years of host relocation achieved and maintained snail infection prevalence at ~0.05%, more than an order of magnitude lower than pre-intervention. A Before-After-Control-Intervention (BACI) study design using multiple-year snail infection data from two intervention lakes and three control lakes demonstrates that dramatic lake-wide reduction of an avian schistosome can be achieved and is not due to natural fluctuations in the parasite populations. The relevance of reducing snail infection prevalence is demonstrated by a large seven-year data set of SI incidence in swimmers at a high-use beach, which showed a substantial reduction in SI cases in two successive years after relocation began. In addition, data from another Michigan lake where vertebrate-host based intervention occurred in the 1980's are analyzed statistically and show a remarkably similar pattern of reduction in snail infection prevalence. Together, these results demonstrate a highly effective SI mitigation strategy that avoids the use of environmentally suspect chemicals and removes incentive for lethal host removal. Biologically, the results strongly suggest that T. stagnicolae is reliant on the yearly hatch of ducklings to maintain populations at high levels on a lake and that the role of migratory hosts in the spring and fall is much less significant.

Underreported and taxonomically problematic: characterization of sanguinicolid larvae from freshwater limpets (Burnupiidae), with comments on the phylogeny and intermediate hosts of sanguinicolids

Blood flukes of freshwater fish are understudied worldwide. Consequently, genetic information and data on their intramolluscan stages are scarce. In the current study, freshwater limpets of the genus Burnupia (Burnupiidae) from South Africa were examined for digeneans. Of 1645 specimens, 3.10% were infected by Sanguinicolidae larvae. Four sanguinicolids were distinguished by body size, number of penetration glands, tegumental spines’ patterns and relative sizes of the finfolds on the body and furcae. Analyses of 28S, 18S and ITS rDNA sequences showed that the morphotypes were distinct from each other and from sanguinicolids whose genetic data are available. The present study is the first genetic characterization of sanguinicolids from Africa. Phylogenetic reconstruction revealed that the present species clustered with a sanguinicolid from Poland and were sister to Sanguinicola and Pseudosanguinicola from Russia and USA, respectively. The results indicate that the current species represent an unknown genus. What is more, blood fluke sequences from East Africa (presumed to be sanguinicolids), were distant from Sanguinicolidae and showed a closer relationship with acipensericolids from the USA. Freshwater fish blood flukes seem to be more diverse than previously recorded and use species of at least 13 gastropod families as intermediate hosts.

Temperature affects predation of schistosome-competent snails by a novel invader, the marbled crayfish Procambarus virginalis

The human burden of environmentally transmitted infectious diseases can depend strongly on ecological factors, including the presence or absence of natural enemies. The marbled crayfish (Procambarus virginalis) is a novel invasive species that can tolerate a wide range of ecological conditions and colonize diverse habitats. Marbled crayfish first appeared in Madagascar in 2005 and quickly spread across the country, overlapping with the distribution of freshwater snails that serve as the intermediate host of schistosomiasis-a parasitic disease of poverty with human prevalence ranging up to 94% in Madagascar. It has been hypothesized that the marbled crayfish may serve as a predator of schistosome-competent snails in areas where native predators cannot and yet no systematic study to date has been conducted to estimate its predation rate on snails. Here, we experimentally assessed marbled crayfish consumption of uninfected and infected schistosome-competent snails (Biomphalaria glabrata and Bulinus truncatus) across a range of temperatures, reflective of the habitat range of the marbled crayfish in Madagascar. We found that the relationship between crayfish consumption and temperature is unimodal with a peak at ~27.5°C. Per-capita consumption increased with body size and was not affected either by snail species or their infectious status. We detected a possible satiation effect, i.e., a small but significant reduction in per-capita consumption rate over the 72-hour duration of the predation experiment. Our results suggest that ecological parameters, such as temperature and crayfish weight, influence rates of consumption and, in turn, the potential impact of the marbled crayfish invasion on snail host populations.

The transcriptomic analysis of Planorbarius corneus hemocytes (Gastropoda) naturally infected with Bilharziella polonica (Schistosomatidae)

The study of molluscan innate immunity is essential for understanding the evolution of the immune system. An advance in the knowledge of their immune system can be achieved by increasing the number of model species. Our study focuses on the immunity of Planorbarius corneus, a pulmonate snail widely distributed in Eurasia. These snails are intermediate hosts of many trematodes, including Bilharziella polonica (Schistosomatidae). In this paper we obtained and analyzed transcriptomes of hemocytes of uninfected snails Planorbarius corneus and snails naturally infected with Bilharziella polonica. The transcriptomes were found to contain transcripts encoding all major groups of immune factors previously described for other gastropods. Pathogen-recognition molecules were the most diverse group of immune factors. Comparison of the transcriptomes of the infected and the uninfected molluscs showed that the expression of some genes changed during infection. Our results extend the knowledge of immune responses of pulmonate snails to trematode invasion and promote P. corneus as a new model for the study of molluscan defence reactions.

Thinking "outside the box": The effect of nontarget snails in the aquatic community on mollusc-borne diseases

There is a great need to understand the impact of complex communities on the free-living parasite stages that are part of them. This task becomes more complex as nonnative species emerge, changing existing relationships and shaping new interactions in the community. A relevant question would be: Can the coexistence of nontarget snails with the target hosts contribute to trematodasis control? We used field and experimental approaches to investigate nonnative competitor-induced parasite dilution. During a three-year field study, we investigated digenean infection in Lymnaea stagnalis from eight Polish lakes inhabited or uninhabited by Potamopyrgus antipodarum. Additionally, we verified the presence of digenean infections in the populations of P. antipodarum. Moreover, we conducted an experimental infection of L. stagnalis with miracidia of Trichobilharzia szidati under increasing densities of P. antipodarum and aimed to infect P. antipodarum with them separately. The prevalence of avian schistosomes in lymnaeid snails was significantly higher in uninhabited lakes than in lakes inhabited by P. antipodarum. Our study indicates that waters with a higher density of invaders have a lower prevalence of avian schistosomes in lymnaeid hosts. The results of experimental studies confirmed that the presence of high densities of P. antipodarum reduces the probability of target host infection. Both field and experimental studies rule out the role of P. antipodarum as a source of avian schistosome cercariae. Here, a nonnative species was tested as a diluter, which in practice may be harmful to the local environment. This work is not a call for the introduction of nonnative species; it is intended to be a stimulus for researchers to continue searching for natural enemies of parasites because, as our results show, they exist. Finding natural enemies to the most dangerous species of human and animal parasites that will pose no threat to the local environment could be groundbreaking.

Intestinal helminthiasis survey with emphasis on schistosomiasis in Koga irrigation scheme environs, northwest Ethiopia

Background

Distribution of schistosomiasis is more focal due to spatial heterogeneities in intermediate host snail dynamics and water contact behavior of humans. This makes the search for new transmission foci of schistosomiasis and its connection with malacologically receptive water bodies essential for effective control of its transmission. This study was intended to assess the prevalence of intestinal helminth infections among schoolchildren and Schistosoma mansoni transmission in Koga irrigation scheme surroundings, northwest Ethiopia.

Materials and methods

Cross-sectional parasitological and malacological surveys were conducted in three schools and nearby water bodies, respectively around Koga irrigation scheme. Stool specimens were collected from 421 randomly selected schoolchildren and microscopically examined using Kato-Katz and formol-ether concentration methods. Malacological surveys were carried out and the identified Biomphalaria pfeifferi snails were screened for schistosome infection. Swiss albino mice were exposed to schistosome cercariae shed by Biomphalaria pfeifferi for definite identification of Schistosoma species.

Results

Among the examined schoolchildren, 22.6% (95% CI: 18.7%-26.9%) were positive for at least one intestinal helminths species. Ascaris lumbricoides was the most frequent intestinal helminth detected among forty (9.5%) children. Schistosoma mansoni was detected among 4.8% (95% CI: 2.9%-7.2%) of children and its prevalence was significantly higher among male children (p = 0.038) and those attending in Mengesha Jemberie Primary School (p = 0.044). Biomphalaria pfeifferi snails were identified in water bodies in close proximity to Mengesha Jemberie and Wotete Abay Primay schools. Schistosoma mansoni adult worms were harvested after exposure of mice to cercariae shed from Biomphalaria pfeifferi snails collected from water bodies nearby Mengesha Jemberie Primary School.

Conclusions

Schistosoma mansoni infection of schoolchildren, findings of schistosome infected snails and establishment of mice infection confirm that transmission is taking place in the study areas. Hence, snail control and other measures such as provision of sanitary facilities and health education are recommended.

Frequency distribution of cytokine and associated transcription factor single nucleotide polymorphisms in Zimbabweans: Impact on schistosome infection and cytokine levels

Cytokines mediate T-helper (TH) responses that are crucial for determining the course of infection and disease. The expression of cytokines is regulated by transcription factors (TFs). Here we present the frequencies of single nucleotide polymorphisms (SNPs) in cytokine and TF genes in a Zimbabwean population, and further relate SNPs to susceptibility to schistosomiasis and cytokine levels. Individuals (N = 850) were genotyped for SNPs across the cytokines IL4, IL10, IL13, IL33, and IFNG, and their TFs STAT4, STAT5A/B, STAT6, GATA3, FOXP3, and TBX21 to determine allele frequencies. Circulatory levels of systemic and parasite-specific IL-4, IL-5, IL-10, IL-13, and IFNγ were quantified via enzyme-linked immunosorbent assay. Schistosoma haematobium infection was determined by enumerating parasite eggs excreted in urine by microscopy. SNP allele frequencies were related to infection status by case-control analysis and logistic regression, and egg burdens and systemic and parasite-specific cytokine levels by analysis of variance and linear regression. Novel findings were i) IL4 rs2070874*T’s association with protection from schistosomiasis, as carriage of ≥1 allele gave an odds ratio of infection of 0.597 (95% CIs, 0.421–0.848, p = 0.0021) and IFNG rs2069727*G’s association with susceptibility to schistosomiasis as carriage of ≥1 allele gave an odds ratio of infection of 1.692 (1.229–2.33, p = 0.0013). Neither IL4 rs2070874*T nor IFNG rs2069727*G were significantly associated with cytokine levels. This study found TH2-upregulating SNPs were more frequent among the Zimbabwean sample compared to African and European populations, highlighting the value of immunogenetic studies of African populations in the context of infectious diseases and other conditions, including allergic and atopic disease. In addition, the identification of novel infection-associated alleles in both TH1- and TH2-associated genes highlights the role of both in regulating and controlling responses to Schistosoma.

Differential proteomic analysis of laser-microdissected penetration glands of avian schistosome cercariae with a focus on proteins involved in host invasion

Schistosome invasive stages, cercariae, leave intermediate snail hosts, penetrate the skin of definitive hosts, and transform to schistosomula which migrate to the final location. During invasion, cercariae employ histolytic and other bioactive products of specialized holocrine secretory cells - postacetabular (PA) and circumacetabular (CA) penetration glands. Although several studies attempted to characterize protein composition of the in vitro-induced gland secretions in Schistosoma mansoni and Schistosoma japonicum, the results were somewhat inconsistent and dependent on the method of sample collection and processing. Products of both gland types mixed during their secretion did not allow localization of identified proteins to a particular gland. Here we compared proteomes of separately isolated cercarial gland cells of the avian schistosome Trichobilharzia szidati, employing laser-assisted microdissection and shotgun LC-MS/MS, thus obtaining the largest dataset so far of the representation and localization of cercarial penetration gland proteins. We optimized the methods of sample processing with cercarial bodies (heads) first. Alizarin-pre-stained, chemically non-fixed samples provided optimal results of MS analyses, and enabled us to distinguish PA and CA glands for microdissection. Using 7.5 x 10⁶ μm³ sample volume per gland replicate, we identified 3347 peptides assigned to 792 proteins, from which 461 occurred in at least two of three replicates in either gland type (PA = 455, 40 exclusive; CA = 421, six exclusive; 60 proteins differed significantly in their abundance between the glands). Peptidases of five catalytic types accounted for ca. 8% and 6% of reliably identified proteins in PA and CA glands, respectively. Invadolysin, nardilysin, cathepsins B2 and L3, and elastase 2b orthologs were the major gland endopeptidases. Two cystatins and a serpin were highly abundant peptidase inhibitors in the glands. While PA glands generally had rich enzymatic equipment, CA glands were conspicuously abundant in venom allergen-like proteins.

Cercarial dermatitis in Austria: questionnaires as useful tools to estimate risk factors?

Cercarial dermatitis is a worldwide occurring skin disease characterized by itching and skin papulation. It is caused by cercariae of the fluke family Schistosomatidae. In the tropics and subtropics species of the genus Schistosoma can cause severe diseases of man. However, several genera (e.g. Trichobilharzia, Bilharziella) of medical significance are prevalent in Europe as well; they are also known as "bird schistosomes", because waterfowl is the final host. Pulmonate snails act as intermediate hosts. Humans are accidental hosts; they get infested by penetration of the cercariae into the skin of swimmers/bathers in ponds and lakes. They can not mature in humans, but die shortly after penetration. Cercarial dermatitis is known in Austria since 1969, with regularly occurrences nearly every summer. In early 2003 we created a homepage to provide information about the causative agents for the public/patients, to document the occurrences and to get data about the distribution of this parasitic disease. We therefore created a questionnaire and asked people for the following parameters: personal data, information about the waters, activity in the water and details about the dermatitis itself. A total of 34 questionnaires were returned. The results will be discussed according to their relevance as risk factors. The way how people interact with the water seems to be essential, but not demographic features. In addition, this approach revealed a new segment of the public that is at risk - owners/users of swimming ponds.

Cream formulations protecting against cercarial dermatitis by Trichobilharzia

Dermatitis caused by penetrating bird schistosome cercariae is an emerging global public health problem. Infections may be prevented by the use of topical formulations that inhibit cercarial skin penetration. We evaluated nine water resistant formulations by exposing treated arms of volunteers to Trichobilharzia szidati cercariae. Six formulations protected from cercarial invasion. However, after immersion of the treated skin in water (2 x 20 min), only two formulations offered full protection: (1) Safe Sea, a cream protecting against jelly fish, (2) niclosamide in water resistant sun protecting cream formulations at concentrations as low as 0.05%. In an in vitro system Safe Sea and a 0.1% niclosamide formulation caused a high damage rate in T. szidati (92% and 99% after 5 min; only niclosamide with lethal effect) but not in Schistosoma mansoni (1% and 72%; both formulations with lethal effect). However, a 1% niclosamide formulation damaged S. mansoni sufficiently (100% after 5 min) and might offer full penetration protection.

Swimmer's itch: incidence and risk factors

Swimmer's itch (cercarial dermatitis) affects people engaged in open-water activities. We report incidence and risk factors for a US lake. Water exposures and swimmer's itch experience were reported daily for riparian household residents and guests at Douglas Lake, Michigan, in July 2000. Incidence of swimmer's itch was 6.8 episodes per 100 water exposure days. Positive risks were (1) exposures in shallow water and in areas with onshore winds and (2) more days of lake use in July. Further epidemiological studies will help public health agencies address this bothersome problem at recreational lakes.

On the morphology and life history of a new mammalian blood-fluke-Ornithobilharzia dattai n. sp.; preliminary report

Of the fifteen valid species of mammalian blood-flukes so far known, six have been originally described from India. Montgomery (1906) described Schistosoma indicum, S. spindalis and Ornithobilharzia bomfordi (Montgomery, 1906) Price, 1929. Datta (1932) found that nasal granuloma of cattle is due to a new schistosome, which was subsequently obtained and described as Schistosoma nasalis by Rao (1933). Rao & Ayyar (1933) obtained a new schistosome from pigs and described it as S. suis. Mudaliar & Ramanujachari (1945) described S. nairi n.sp., from an elephant, which was transferred to the genus Ornithobilharzia by Bhalerao (1947). Another new species of blood-fluke has now been found in Indian buffaloes and cattle. While studying the larval trematode fauna of the local aquatic snails, large numbers of a new schistosome cercaria were obtained from nine out of three hundred specimens of Limnaea luteola examined during November 1950. When the cercariae were administered to two guinea-pigs, a buffalo-calf and a bull-calf, they developed into an interesting blood-fluke referable to the genus Ornithobilharzia Odhner, 1912. Subsequently, three out of thirteen buffaloes examined post-mortem were found to be naturally infected with the same parasite. The morphology of the adult and of its cercaria is briefly described in this paper.

Public health importance and risk factors for cercarial dermatitis associated with swimming in Lake Leman at Geneva, Switzerland

Fifteen cohorts of healthy bathers were recruited at four Lake Leman beaches between 3 July and 23 August 1996 to assess the public health importance of cercarial dermatitis in Geneva, Switzerland. Telephone follow-up interviews were carried out after 2-7 days. Overall, 153 bathers out of 555 reported probable cercarial dermatitis at follow-up. Median daily attack rate was 27.7% (2.2-57.7%). Of the cases, 11.1% noticed more than 30 skin lesions, 19.6% described severe itching, 50.3% used a drug treatment, 3.9% visited a doctor and 15% claimed they would reduce their bathing activities. History of cercarial dermatitis, time spent in the water, hour of the day, barometric pressure and maximum daily atmospheric temperature predicted disease occurrence in multivariate analysis. While a benign disease, cercarial dermatitis may have a negative impact on the local water recreation industry. The identification of risk factors for the disease may help produce better preventive recommendations for the bathers.

The epidemiology of cercarial dermatitis and its association with limnological characteristics of a northern Michigan lake

Cercarial dermatitis (swimmer's itch) is an annoying inflammatory response to penetration of skin by non-human schistosome parasites while swimming or wading in lakes. The purpose of this survey was to identify risk factors for cercarial dermatitis and to determine whether limnological characteristics of the lake were associated with development of the condition. Starting 1 June 1993, an active case surveillance system was established in the communities around Walloon Lake, Michigan, which continued until 30 August 1993; controls were randomly selected weekly during the same time period through telephone surveys. A total of 317 cases of cercarial dermatitis occurring in 146 clusters was identified over the course of the summer and 295 controls were selected from the weekly telephone surveys. Factors associated with the development of cercarial dermatitis identified in the study included age, the time of day at which exposure to lake water occurred, and the month in which exposure to lake water took place. In addition, development of cercarial dermatitis was significantly associated with exposure to lake water in the area of the lake with the highest algae content and shallowest depth.

Rodents infected with Schistosoma mansoni produce cytolytic IgG and IgM antibodies to the Lewis x antigen

Schistosoma mansoni is a blood fluke that produces glycoconjugates containing the Lewis x antigen (Le(x)) Gal beta 1-->4(Fuc alpha 1-->3) GlcNAc beta 1-->R. However, Le(x) antigen is also normally expressed in many tissues of adult rodents. We now report that mice and hamsters chronically infected with S.mansoni generate high titers of both IgM and IgG antibodies reactive with Le(x) and that no reactivity is present in sera from uninfected animals. Anti-Le(x) antibodies were detected by ELISA using the Le(x)-containing neoglycoprotein lacto-N-fucopentaoseIII-BSA. The IgG in infected animals consists of IgG1, IgG2a, and IgG2b subclasses and binds to Protein A-Sepharose. The sera of infected animals reacts only with Le(x) antigen and has no reactivity toward either Le(a) or sialyl Le(x). The IgM response to Le(x) is detectable at week 2, whereas the IgG response is detectable at weeks 5-6 following infection of mice. The sera of infected mice and hamsters can mediate the complement-dependent cytolysis (CDC) of cells expressing surface Le(x). This cytolytic activity is exclusively effected by the anti-Le(x) antibodies, since their removal from sera by adsorption depletes the sera of CDC activity. Thus, the abundant expression of the Le(x) antigens by the parasite elicits cytolytic antibodies reactive with a host antigen.

[Modification of the liver phospholipid status of cattle by Orientobilharzia turkestanica trematodes]

The paper gives the data on a trematode influence onto the phospholipid (PL) contents in the liver of cows. It is shown, that the decrease of PL basic fraction concentrations, i.e. phosphatidilcholin (PC) by 20% and phosphotidilethanolamin (PE) by 26%, during the period of infection is accompanied by the increase of respective lysoforms, namely, lysoPC by 240%, and lysoPE by 160%, and as well as minor forms, PL-diphosphotidilgleserol by 70%, sphingomielin by 47% and phosphatidilserin by 41%. It is suggested, that the infection of cow liver by trematodes determines such contents and principles of membrane structures, which decrease their functional activity and probably increase its permeability for ions, some metabolites and low molecular carbohydrates.

Modulation of the bacterial clearance activity of haemocytes from the freshwater mollusc, Lymnaea stagnalis, by the avian schistosome, Trichobilharzia ocellata

The ability of haemocytes, from the haemolymph of the gastropod mollusc Lymnaea stagnalis, to recognize and eliminate the bacterium Aeromonas salmonicida was shown using an in vitro bacterial clearance assay. The assay employs a dye which is reduced by A. salmonicida in direct proportion to the number of viable bacteria resulting in a colour change which can be determined spectrophotometrically. Addition of cytochalasin B resulted in a marked decrease in bacterial clearance, implicating both intracellular and extracellular cytotoxicity of haemocytes. A comparison of haemocytes from uninfected snails and snails infected with the avian schistosome parasite Trichobilharzia ocellata showed that both juveniles and adults of L. stagnalis were susceptible to infection with T. ocellata. After exposure to the trematode for 1.5 h the haemocytes from these infected snails had an enhanced clearance capacity, whilst cells obtained from snails with 24-96 h infections showed decreased clearance of the bacteria, indicating suppression by the parasite. Haemocytes, as well as plasma, which was tested on haemocytes from uninfected snails, were used and hence a distinction was made between cell and humoral-associated effects. The results show that both cellular and humoral components of immunity were activated, then suppressed, following exposure to the parasite. Infection with T. ocellata seems to have a modulating effect on the bactericidal activity of the internal defence system of the snail host, L., stagnalis.

[The ecological prerequisites for a worsening of the cercariasis situation in the cities of Russia (exemplified by the Moscow region)]

Conditions favouring the sharp increase of risk to be infected with cercariasis (caused by trematode cercariae Trichobilharzia ocellata Brumpt, 1931, Schistosomatidae) were examined in Moscow region (Russian Federation). Main factors of worsening the cercariasis situation are as follows. a) The increase of environment pollution by everyday wastages and the overgrowing with macrophytes in internal water basins of Moscow, that makes favourable conditions for the development of molluscs, which are intermediate hosts (mainly Lymnaea ovata and L. auricularia). b) The sharp increase of number of ducks (mainly mallard Anas platyrhyncos), which are final hosts, that is a result of bird escaping from farms (approximately in 60-70-th) and of high adaptation of these birds to city water basins. The detailed estimation of the cercariasis situation in 89 water basins of different types in Moscow and recreation zone was carried out. Examples of charting the zones with different risk degree of cercariasis infection are given. It is stated that at current time the cercariasis became a significant and widely distributed medical problem, which is most important in cities (including such large one as Moscow). Prophylaxis recommendations are proposed.

Cercarial dermatitis outbreak at a state park--Delaware, 1991

On October 28, 1991, an employee of the Division of Public Health (DPH), Delaware Department of Health and Social Services, reported that her son and at least 10 other persons who had recently participated in a high school biology class field trip to Cape Henlopen State Park had contracted pruritic dermatitis. The Delaware Health Monitoring and Program Consultation Section conducted an investigation to confirm the reported presumptive diagnosis of cercarial dermatitis and to assess the extent of this outbreak.

The neuropeptide schistosomin and haemolymph from parasitized snails induce similar changes in excitability in neuroendocrine cells controlling reproduction and growth in a freshwater snail

Infection of the snail Lymnaea stagnalis with the schistosome parasite Trichobilharzia ocellata results in inhibition of reproduction and in giant growth. Parasite-related effects on the neuroendocrine centres that control these processes were studied electrophysiologically. Haemolymph from infected snails reduced the excitability of the caudodorsal cells, which control egg laying. In contrast, the excitability of the growth-controlling Light Green Cells was increased under these conditions. The endogenous anti-gonadotropic neuropeptide schistosomin, the presence of which is strongly enhanced in parasitized snails, induced similar effects. Schistosomin apparently plays an important role in the balance between reproduction and growth in Lymnaea. This balance is severely disturbed during parasitic infection, probably as a result of the release of the peptide.

Trichobilharzia ocellata: influence of infection on the interaction between the dorsal body hormone, a female gonadotropic hormone, and the follicle cells in the gonad of the intermediate snail host Lymnaea stagnalis

Activation of adenylate cyclase (AC)-cAMP system in follicle cells of Lymnaea stagnalis by the gonadotropic dorsal body hormone (DBH) is inhibited by schistosomin, an agent present in hemolymph of snails infected with Trichobilharzia ocellata. AC activation was determined enzyme cytochemically. This conclusion is based on the observation that the percentage of oocytes with AC-positive follicle cells in gonads incubated in the presence of schistosomin, i.e., in serum of infected snails (IS) with DBH, is significantly lower than that in gonads incubated in the absence of schistosomin, i.e., in serum of noninfected snails (NS) with DBH. Follicle cells in gonads preincubated in the absence of schistosomin, i.e., in NS, and subsequently incubated with freshly dissolved DBH showed a considerably lower response to DBH than those in not preincubated gonads. This indicates that the number of receptors for DBH on follicle cells had decreased during preincubation. The response to DBH also appeared to decrease when the hormone was preincubated in NS. This indicates that the activity of DBH decreases during preincubation. These data make it impossible to answer the question of whether or not schistosomin acts as an antagonist of DBH at the receptor level.

Schistosomatium douthitti: biochemical and morphological effects of an experimental infection in mice

The pathophysiological changes that occur in mice experimentally infected with Schistosomatium douthitti were studied. Male ICR mice, 6-8 weeks in age, were exposed to 100 cercariae of S. douthitti from infected snails (Lymnaea catascopium) and sacrificed weekly for a total of 13 weeks. Liver homogenates, serum samples, and histological sections of liver tissue were examined. Results showed that body weights of animals with prepatent infections were higher than those of corresponding controls. After patency, which occurred at 5 weeks, body weights were lower and liver weights were higher resulting in significantly increased liver weight/body weight ratios. Hematocrit values declined progressively in patent infections. Total cholesterol in liver was generally higher in the parasitized groups reaching significance during patency. Values rose with age in both control and parasitized groups, but sooner in the latter. Free cholesterol was increased in the liver of animals with patent infections. Total lipid content of the liver was reduced in the infected animals throughout the study. Both liver glycogen and serum glucose levels in the infected animals rose over the control values. The activity of alkaline phosphatase (E.C.3.1.3.1) was elevated in liver tissue of infected mice. Glutamic-pyruvic transaminase (E.C.2.6.1.2) activity was higher in serum but lower in the livers of animals harboring patent infections. Total bile salt concentration in parasitized animals did not differ appreciably from control values; however, gallbladders were enlarged five times in the infected animals. Histologically, liver sections from infected mice showed granulomas in various stages of formation and degeneration. Granulomas contained from 1 to 40 schistosome eggs. After 6 weeks of infection, granulomas were characterized by many neutrophils and monocytes. Few lymphocytes and eosinophils were present. As the granulomas developed, fibroblasts and connective tissue became more prominent. Glycogen deposits were observed surrounding granulomas and were increased in older infections. Adult worms contained abundant amounts of glycogen and cholesterol in their parenchymal tissues.

An outbreak of schistosomiasis in Atlantic brant geese, Branta bernicla hrota

A heavy infection with schistosomes of the genera Trichobilharzia and Dendritobilharzia was considered the cause of 90% mortality in a group of 40 wild-caught Atlantic brant geese (Branta bernicla hrota) that were maintained in captivity on a fresh-water pond in Aurora, Ontario. Numerous adult worms and eggs were disseminated in many organs throughout the body of all birds examined. The main pathological findings, attributed to both eggs and adults, included emaciation, thrombosis of the caudal mesenteric vein and its branches, fibrinohemorrhagic colitis, and in some birds, heptomegaly. Translocation of brant geese from their natural marine environment to a fresh-water pond may have caused them to be exposed to parasites which they would not normally encounter.

Increased activity of the female gonadotropic hormone producing dorsal bodies in Lymnaea stagnalis infected with Trichobilharzia ocellata

Juvenile specimens of Lymnaea stagnalis were exposed to 0 or 4 miracidia of Trichobilharzia ocellata. Dissection followed at day 22 post exposure. The effects of infection on the activity of the female gonadotropic hormone producing Dorsal Bodies (DB) were studied by phase-contrast and electron microscopy. Morphometry shows that the relative volume of DB cells of infected snails is 1.6 times as high as in controls. This is mainly due to a 45% higher cytoplasmic volume. The number of profiles of the Golgi apparatus increases by nearly 90% and the Golgi volume by 40% as a result of infection. Numerous omega-shaped indentations of the plasma membrane of the DB cell processes indicate the release of the contents of the DB hormone containing elementary granules. It is concluded that parasitic infection causes a clear increase in the synthetic activity of the DB. Most probably, the parasites exert the inhibiting effects on reproductive activity at the level of the targets of the reproductive hormones.

Heterologous immunity against Schistosoma mansoni in mice by administration of Heterobilharzia americana

Three groups of Swiss albino mice were exposed to cercariae of Heterobilharzia americana a mammalian schistosome in Southern United States. they were challenged at different intervals with cercariae of a Puerto Rican strain of Schistosoma mansoni, and a fourth group (control for the first two groups) was exposed only to S. mansoni. With a patent infection (two months) of H. americana there was a noticeable reduction of the worm recovery rates of S. mansoni and its eggs deposited in the tissues. In the two other groups exposed simultaneously or at a 3-week interval, there was no significant reduction in the recovery rates of adult S. mansoni and the number of eggs exceeded in some cases that noted for the control group. Thus a patent infection with H. americana is necessary to confer immunity against a challenge infection with S. mansoni.