Identification of an avian schistosome recovered from Aythya novaeseelandia and infectivity of its miracidia to Lymnaea tomentosa snails

A partial life cycle involving miracidia hatched from the eggs of Trichobilharzia sp. recovered from New Zealand scaup (Aythya novaeseelandia) to the release of furcocercariae by laboratory snails (Lymnaea tomentosa) was accomplished. Challenges with five and ten miracidia per snail were lethal. Challenge with three miracidia resulted in development to the daughter sporocyst stage and death in five, development to furcocercarial stage and death in one, and shedding of furcocercariae in one of seven snails. Observed lethality of schistosome miracidia to L. tomentosa may explain the low infection prevalence observed in the wild. Future work should plan challenge exposures of three or fewer miracidia to ensure snail survival and successful recovery of furcocercariae. The Trichobilharzia sp. found in the New Zealand scaup does not key morphologically to the literature. It may be a new species and further work is needed.     

Karyologic research on trematodes of the family Schistosomatidae from northwestern Chukota

Peculiarities of chromosome sets of 4 schistosome species, parasitic in different mollusks from the Chaun lowland were investigated. The karyotype of parthenitae of Trichobilharzia sp. 1 (the intermediate host Sibirenauta picta) consists of 18 elements, of which the 2nd and 6th pairs are submetacentric-metacentric, the other chromosomes are metacentric. The diploid chromosome set of Trichobilharzia sp. 2 (the intermediate host Anisus acronicus) includes 16 biarmed units. The first pair of metacentric chromosomes amounts to 28.02% of the whole haploid set length. Austrobilharzia variglandis have 14 biarmed autosomes and 2 sex chromosomes. Females are the heterogametic sex, Z-chromosomes are of a metacentric-submetacentric type, W have an acrocentric structure. The chromosome complex of Shistosomatium sp. (the intermediate host Lymnaea zazurensis) consists of 14 elements, of which the largest pair is sex chromosomes. The female sex is determined by an exclusively large metacentric Z-chromosomes (relative length 38.36%) and a small acrocentric W-chromosome (relative length only 7.08%). The chromosome sets of Schistosomatium sp. have undergone the most considerable evolutionary transformations among schistosomes, as a result it has the least linkage groups of genes and the most expressed differentiation of sex chromosomes.     

A survey of waterfowl for echinostomes and schistosomes from Lake Wanaka and the Waitaki River watershed, New Zealand

Waterfowl from Lake Wanaka and the Waitaki Lakes watershed of New Zealand's South Island were surveyed to find natural hosts with adult echinostomes and schistosomes to provide sufficient numbers of eggs for laboratory studies. The Canada goose (Branta canadensis) was found to host an echinostome determined to be a New Zealand strain of Echinostoma revolutum. The New Zealand scaup (Aythya novaeseelandia) concurrently hosts three species of echinostomes (E. revolutum, Echinoparyphium cinctum and E. recurvatum) plus two species of avian schistosomes (Trichobilharzia sp. and Dendritobilharzia pulverulenta). In the Canada goose and the New Zealand scaup, adult gravid echinostomes predominated over juveniles. In other waterfowl surveyed, very few echinostomes were found, with juveniles predominating.     

Allobilharzia visceralis gen. nov., sp. nov. (Schistosomatidae-Trematoda) from Cygnus cygnus (L.) (Anatidae)

In Iceland, the examination of whooper swans (Cygnus cygnus L.) viscera resulted in the detection of adult digenean flukes of the family Schistosomatidae. The mature worms occurring in the blood vessels of the large intestine and mesenterium caused vascular lesions, around the eggs deposited in the intestinal mucosa and liver granulomatous reactions developed. The morphology of the isolated schistosomes shows certain similarity with the flukes of the genus Trichobilharzia; in males reduced gynecophoral canal, and on both sexes both suckers and spatulate ends are present. However, the Icelandic flukes possess other morphological features which are distinct from the genus: the point of caecal reunion in males takes place posterior to gynecophoral canal and the genital pore is behind acetabulum and anterior to caecal reunion. In order to evaluate the identity of Icelandic schistosomes, sequencing of ITS region of DNA was performed, and the obtained sequence was deposited in GenBank under the accession no. DQ067561. Following phylogenetic analysis of relationship between the sequence of Icelandic flukes and database sequences of other bird schistosome genera (Trichobilharzia, Gigantobilharzia and Dendritobilharzia) showed different position of Icelandic worms in the phylogenetic tree. In conclusion, our study revealed new genus and species of schistosome flukes--Allobilharzia visceralis gen. et sp. n.     

Detection of bird schistosomes in lakes by PCR and filter-hybridization

Many lakes around the world are contaminated with bird schistosome cercariae, which penetrate into human skin, causing an itching dermatitis called "swimmers' itch." Bathers could be forewarned from exposure to the larvae and ecological examinations could be performed, when a sensitive method to detect the parasites in aquatic systems, where lots of organisms hinder microscopic examinations, would be available. For this purpose we cloned, sequenced, and analyzed a 396 bp tandem repeated DNA sequence from Trichobilharzia ocellata (ToSau3A), and employed it for developing molecular detection assays. It hybridized with less than 100 pg DNA from different Trichobilharzia species (T. ocellata, Trichobilharzia franki, and Trichobilharzia regenti), but not with 10 ng DNA from other related or sympatric trematodes. A PCR assay, amplifying this sequence with the same specificity, detected 100 fg T. ocellata DNA, 1 cercaria in 0.5 g plankton, and 2 cercariae in 0.5 g host snail tissues.     

Molecular taxonomic identification of Schistosomatidae from Naroch Lake and Polonevichi Lake in Belarus

In Belarus, Naroch Lake is the only area with a high incidence of the human cercarial dermatitis (HCD). However, very little is known about the taxonomy of avian schistosomes, the causative agents of the disease, which are found in Naroch Lake and other lakes in Belarus. In this study, we used a molecular approach to investigate the systematic position and biodiversity of avian schistosomes from Naroch Lake and Polonevichi Lake. Based on the sequence analysis of the ITS genomic region, we were able to detect four different species of bird schistosomes in Naroch Lake (Trichobilharzia szidati, Trichobilharzia franki, Bilharziella polonica and a novel Trichobilharzia species) and two species in Polonevichi Lake (T. szidati and B. polonica). The data were used to reveal the phylogenetic position of HCD causative cercariae found in Belarusian water reservoirs and to establish their relationships within the group of avian schistosomes. We discuss the possibility of identifying species of Trichobilharzia using the fragment length polymorphism analysis of the ITS region. Possible epidemiological causes of HCD incidence in Belarus are also discussed.     

Ecological factors in schistosome transmission, and an environmentally benign method for controlling snails in a recreational lake with a record of schistosome dermatitis

The avian schistosomes, Trichobilharzia stagnicolae, T. physellae and Gigantobilharzia sp., that cause Schistosome Dermatitis (Swimmers' Itch) in humans were studied in the laboratory and at Cultus Lake, British Columbia, Canada in relation to the biology and behavior of their intermediate snail hosts, Stagnicola catascopium, Physa sp. and Gyraulus parvus, respectively, and their definite bird hosts. Wind-driven, surface currents were measured. Populations of snails, close to host-bird roosting logs had a very high prevalence of schistosome infections. An experiment that mechanically disturbed the epilithic habitat of the snails using a boat-mounted rototiller or a tractor and rake, eliminated almost all of the snails if the disturbance was done in areas of high snail concentration in shallow areas of the lake during the breeding and early development phase of the snail. It is proposed that the incorporation of snail habitat disturbance into management programs is an effective way to control Schistosome Dermatitis.     

Individual and population variation in cercariae of bird schistosomes of the Trichobilharzia ocellata species group as revealed with the polymerase chain reaction

The polymerase chain reaction with arbitrary (RAPD-PCR) or specific primers was used to study the population variation and to identify the species in cercariae of schistosomes of the Trichobilharzia ocellata species group (Trematoda, Schistosomatidae). In total, 28 cercariae were obtained from two spontaneously invaded mollusks Lymnaea stagnalis (LS) and L. ovata (LO), which were collected in different water bodies of Moscow. RAPD-PCR was carried out with two arbitrary primers, OPA9 and OPB11, which each detected different levels of individual and among-group variation and revealed considerable genetic differentiation of cercariae from different host mollusks. To check whether the cercariae of the two samples belong to one species, sequencing was performed with a region corresponding to intergenic transcribed spacer 2 (ITS2), which was earlier proposed for cercaria identification in three European species of bird schistosomes of the genus Trichobilharzia (T. franki, T. regenti, and T. szidati). The ITS2 sequences of two LO cercariae were identical, each consisted of 319 bp, and showed 100% homology to the T. franki ITS2 sequence. The ITS2 sequences of two LS cercariae were identical, each consisted of 323 bp, and showed 99.4% homology to the T. szidati counterpart. The causes of genetic variation in cercariae and prospects of using RAPD markers to study different stages of the life cycle in trematodes are discussed.     

Morphological peculiarities of schistosomatid cercariae of Trichobilharzia cf. ocellata group occuring in Moscow and Saint-Petersburg populations

Morphology of schistosomatid cercariae of the genus Trichobilharzia (ocellata group) is described based on original and reference data. The material (Trichobilharzia cercariae) was collected in 1999-2000 from naturally 'infected snails Lymnaea stagnalis from Moscow and Saint-Petersburg megalopolises. The more accurate flame cell formula for these cercariae, as well as some aspects of chaetotaxy and eye morphology are given. The differences between cercariae from these regions were found. Based on a comparison of nef data with the reference data, it was found that the cercariae examined differ from those from the Central Europe.     

Observations on cercarial chaetotaxy as a means for the identification of European species of Trichobilharzia Skrjabin & Zakharow, 1920 (Digenea: Schistosomatidae)

In order to evaluate the importance of cercarial chaetotaxy in the identification of European avian schistosomatids of the genus Trichobilharzia Skrjabin & Zakharow, 1920, papillary patterns of T. franki Müller & Kimmig, 1994 and T. ocellata (La Valette, 1855) Brumpt, 1931 were examined and compared. Scanning electron microscopy (SEM) was also employed to confirm the number and distribution of the sensory papillae. The chaetotaxy of T. franki and T. ocellata were identical, which suggests a close kinship between the two species. Some sensory papillae stained insufficiently with silver nitrate or were difficult to examine using light microscopy. Thus, the use of SEM in future examinations of Trichobilharzia chaetotaxy will ensure the collection of data that are comparable between studies, even though some argentophilic structures are not visible using SEM.     

Karyotype of an avian schistosome Trichobilharzia szidati (Digenea: Schistosomatidae)

Somatic chromosomes of Trichobilharzia szidati Neuhaus, 1952 are described from larval stages dissected from snoils, air-dried on slides and stained with Giemsa and C-banding technique, used for the first time in Trichobilharzia sp. The karyotype consisted of 7 autosomal pairs and 1 pair of sex chromosomes, ZZ in the male and ZW in the female, where Z and W chromosomes are of different sizes and both are classified as submetaceatric. C-banding aided in identification of chromosomes Nos 4, satellited 6 and 8. No heterochromatin was observed in the W chromosome. The results were not in agreement with those previously reported and represent new findings. The possible explanation for this fact is given.     

The Effect ofBacillus thuringiensisM-exotoxin on Trematode Cercariae

The effect ofBacillus thuringiensis israelensiseluate containing water-soluble exotoxin (M-exotoxin) was observed by its use on cercariae of seven trematode species. To the most sensitive species to the toxic effect of the mentioned toxin belonged schistosome furcocercariae (human speciesSchistosoma mansoniand avian parasiteTrichobilharzia szidati). Under the influence of the toxin, surface syncytial structure (tegument) was separated from underlying tissues, with subsequent disintegration of internal organs connected with disruption of acetabular glands and release of their proteolytic content.     

New intermediate host records for the avian schistosomes Dendritobilharzia pulverulenta, Gigantobilharzia huronensis, and Trichobilharzia querquedulae from North America

Here we provide the first North American report of a naturally infected snail, Gyraulus parvus, harboring the larval stages of the cosmopolitan, arterial schistosome, Dendritobilharzia pulverulenta. The relatively small cercariae of this species are shed in the early morning, are sticky, and adhere to the water's surface film. We also provide a report of the snail host, Physa gyrina, of the widespread North American passerine schistosome, Gigantobilharzia huronensis. Finally, we provide unambiguous documentation that Physa gyrina is a natural snail host for Trichobilharzia querquedulae, a schistosome primarily of dabbling ducks.     

Schistosomes in the North: A unique finding from a prosobranch snail using molecular tools

Samples of schistosome cercariae from three different snail species (Lymnaea stagnalis, Radix auricularia and Valvata (Tropidina) macrostoma) collected from lakes in Central Finland were analyzed using molecular techniques. Based on sequences of ITS region of rDNA, the parasite isolates from L. stagnalis and R. auricularia belong to Trichobilharzia szidati and T. franki, respectively. This confirms a wide distribution of these two species in Europe. On the other hand, the isolates from V. macrostoma represent a unique finding — they belong to yet unknown schistosome species falling into the bird schistosome clade. Therefore, identification of natural final hosts and morphological characterization of particular developmental stages need to be performed in the future.     

陕西红脂大小蠹天敌种类调查

对陕西红脂大小蠹Dendroctonus valens LeConte危害区的天敌种类调查表明,寄生于红脂大小蠹的病原真菌共有5种,其中幼虫期有头孢霉Cephalosporium sp.、球孢白僵菌Beauveria bassiana和拟卵孢霉Ovulariopsis sp.,成虫期有球孢白僵菌Beauveria bassiana、枝顶孢霉Acremonium sp.、头孢霉Cephalosporium sp.、木霉Trichoderma sp.4种,其中以球孢白僵菌和枝顶孢霉Acremonium sp.的致病能力最为显著。捕食性天敌昆虫主要有西岳蛇蛉Agulla xiyue Yang et Chou、日本弓背蚁Camponotus japionicus Mayr、中华红林蚁Formica sinensis Wheeler、蚁形郭公甲Thanasimus formicarius(L.)及纤细阎甲Platysoma attenuata(LeConte),它们对红脂大小蠹均有较明显的控制作用。寄生性天敌主要有1种寄生蝇和1种茧蜂。     

Ciliate protozoa in the rumen of Kafue lechwe, Kobus leche kafuensis, in Zambia, with the description of four new species.

The composition of the rumen ciliate fauna in 76 Kafue lechwe inhabiting a limited area in Zambia was surveyed and five genera containing 24 species with 16 formae belonging to the family Ophryoscolecidae were identified. Four new species belonging to Diplodiniinae were recognized and described as Diplodinium lochinvarense n. sp., Diplodinium leche n. sp., Diplodinium zambiense n. sp., and Metadinium ossiculi n. sp. In addition, Ostracodinium gracile form fissilaminatum Dogiel, 1932 was found for the second time and described as Metadinium fissilaminatum n. comb. The species composition was fairly unusual. Seven of the species have been found only in African wild antelopes and these species were found more frequently than cosmopolitan species. There was no evidence of isotrichid species. The average density of ciliates per 1 ml of the rumen fluid was 25.7 x 10(4), and the number of ciliate species per head of host was 10.8.     

Trichobilharzia mergi sp. nov. (Trematoda: Digenea: Schistosomatidae), a visceral schistosome of Mergus serrator (L.) (Aves: Anatidae)

Parasitological investigations on red-breasted mergansers (Mergus serrator L.) in Iceland revealed digenean flukes of the family Schistosomatidae. Adult worms were detected in blood vessels of the large intestine and eggs were deposited in the mucosa and surrounded by granulomatous reactions. Traditional morphological methods showed that the flukes have very slender filiform bodies, males are equipped with a short gynaecophoric canal and both suckers and spatulate ends are present on each sex. Among characteristics of the flukes which render them morphologically distinct from other Trichobilharzia species are: i) males—well developed vesicula seminalis (v.s.) consisting of a short v.s. externa and a significantly longer (approx. 3 times) v.s. interna, unusually well developed genital papilla and localization of the first testis a relatively long distance posterior to the gynaecophoric canal; ii) eggs—small and elongated with slightly rounded poles and a short terminal spine. DNA taxonomic techniques confirmed that a new species had been identified, Trichobilharzia mergi sp. n. The sequence data were deposited in GenBank under the accession numbers JX456151 to JX456172. Comparison of the results with our previously published data on characterization of DNA of cercariae isolated from freshwater lymnaeid snails showed that larval development of T. mergi is associated with Radix balthica L. (=Radix peregra Müller, 1774; = Radix ovata Draparnaud, 1805).     

In vitro culture of intramolluscan stages of the avian schistosome Trichobilharzia ocellata

Several different procedures for in vitro cultivation of intramolluscan stages of the avian schistosome Trichobilharzia ocellata were tried. A medium was found and culture conditions were established that not only supported in vitro transformation of miracidia into mother sporocysts, but also resulted in substantial subsequent growth; moreover, some degree of germinative development appeared to occur as well. Cerebral ganglia from uninfected adult snails of the intermediate host species, Lymnaea stagnalis, could produce factors promoting in vitro development of young mother sporocysts. Results are compared with data from the literature and it is concluded that greater success in in vitro culturing of young mother sporocysts of T. ocellata can be achieved than has hitherto been reported for other schistosome species. The same culture procedures were less successful when applied to other intramolluscan stages of T. ocellata, but can be used for in vitro maintenance of these stages. The procedures described here will be a useful tool in the study of schistosome-snail interactions in T. ocellata-L. stagnalis and possibly in other systems as well.     

New species of Mycosphaerella from Myrtaceae in plantations and native forests in eastern Australia

The majority of Mycosphaerella species from eucalypts (Eucalyptus, Corymbia and Angophora) in Australia have been recorded only from trees growing in plantations. This illustrates a bias in research in the past two decades toward commercial enterprise, and it emphasises a lack of understanding of the occurrence of these important fungi under natural conditions. Surveys of foliar fungi in native forests in eastern Australia, as well as adjacent plantations, thus have been initiated in recent years. In this study we describe four new species of Mycosphaerella from Eucalyptus spp. as well as other Myrtaceae. Mycosphaerella tumulosa sp. nov. (anamorph: Pseudocercospora sp.) was found on more than seven species of Eucalyptus and Corymbia in native forests and plantations in northeastern New South Wales and southeastern Queensland and appears to be relatively common, although not damaging to these trees. Mycosphaerella multiseptata sp. nov. was recorded from several locations on species of Angophora in native forests and amenity plantings. Mycosphaerella pseudovespa sp. nov. was found in one location in native forest on E. biturbinata. The first species of Mycosphaerella to be described from Syncarpia, M. syncarpiae sp. nov., was found in native forests in numerous locations from Sydney through to northeastern New South Wales and appears to be relatively common.     

Azteca Ants as Antiherbivore Agents of Tococa formicaria (Melastomataceae) in Brazilian Cerrado

Several ant species have been found associated with domatia of plant species of the genus Tococa (Melastomataceae). In the present study we investigated the relationships between Tococa formicaria Mart. and ants in the Cerrado (savanna-like vegetation) from central Brazil. We addressed questions about the utilisation of domatia by different ant species and their efficiency in reducing herbivory. We found 8 ant species in the domatia, with Azteca sp. 1 being present in 47.2% of the sampled individuals. The other species found were: Azteca sp. 2, Camponotus sp., Dolichoderus gr. diversus, Dolichoderus lutosus, Leptothorax sp., Oligomyrmex sp. and Linepithema sp. The dominance of Azteca sp. 1 was significantly higher in the larger individuals, with about 85% of individuals in the highest size class being occupied by this species. We performed experiments of attack to live baits (termites) on T. formicaria leaves and on leaves of control species (any other neighbouring plant species of similar size). The recruitment rates were significantly higher on T. formicaria leaves. We also showed that herbivory was significantly lower in T. formicaria individuals occupied by Azteca sp. 1 than in individuals occupied by other ant species. The results of this study may be considered as evidence to support the assumption of a mutualistic relationship through defence against herbivory between Azteca ants and T. formicaria.