Host Specificity and Ecology of Digenean Parasites of Nassariid Gastropods in Central Queensland, Australia, with Comments on Host-Parasite Associations of the Nassariidae.

Nassariid gastropods are well represented in Australia, and Nassarius dorsatus (Röding), Nassarius olivaceus (Bruguière), and Nassarius pullus (Linnaeus) are common in the intertidal mangroves of the Capricornia region in Central Queensland. A survey of the digenean trematode fauna of nassariids of the region revealed cercariae of 12 species from six trematode families associated with these gastropods. Six species of Acanthocolpidae were found, including three putative species of the genus Stephanostomum. Additionally, two species of Himasthlidae and one species each of Microphallidae, Opecoelidae, Zoogonidae, and Lepocreadiidae were identified. The majority of the trematode species identified were found in only one host species; only four infected more than one species of nassariid. Sixteen new host-parasite combinations were added to the fauna known to infect the Nassariidae. Broader examination of host-parasite associations shows that families using nassariids commonly as first intermediate host are the Acanthocolpidae, Lepocreadiidae, and Zoogonidae, as well as Himasthla spp. from the Himasthlidae. Nassariid gastropods are also the dominant marine first intermediate hosts for the Acanthocolpidae, Lepocreadiidae, and Zoogonidae and one of the three most common first intermediate host families for marine Himasthla spp.

A review of the currently recognised zoogonid cercariae, including the identification and emergence ecology of Cercaria capricornia XI (Digenea: Zoogonidae) from Nassarius olivaceus (Gastropoda: Nassariidae) in Central Queensland, Australia.

In the present study, we review the known zoogonid cercariae, summarise their life-cycles and first intermediate host distributions, and present a new cercaria, Cercaria capricornia XI (Digenea: Zoogonidae), which was found in one of three nassariid gastropods, Nassarius olivaceus (Bruguière), surveyed in the intertidal zone in the Capricornia region of Central Queensland, Australia. Morphological data and molecular analysis of the ITS2 rDNA region support placement of this cercaria in the family Zoogonidae but do not allow any further resolution of its identity. There are now fifteen cercariae described as belonging to the Zoogonidae; thirteen of these, including the present species, infect neogastropods as first intermediate hosts and two use vetigastropods. This study reinforces the pattern that the Nassariidae is by far the most commonly reported family for the Zoogonidae. Given its richness we predict that the Nassariidae will prove to harbour many more zoogonid species.

Phenotypic plasticity of six unusual cercariae in nassariid gastropods and their relationships to the Acanthocolpidae and Brachycladiidae (Digenea).

Species-level relationships of a complex of six putative acanthocolpid cercariae with ventral keels from nassariid gastropods from Capricornia, Queensland (Cercaria capricornia I-VI) were explored using mitochondrial and nuclear DNA sequence data. Analysis of the large subunit of nuclear ribosomal DNA (rDNA), the internal transcribed spacer 2 rDNA and subunit 3 of the nicotinamide-adenine-dinucleotide dehydrogenase mitochondrial gene indicates that the six distinct morphotypes previously identified relate to only three discrete genotypes. Consequently, the six cercarial morphotypes that were inferred to represent six species and distinguished previously based on morphology and behaviour, are considered here to be comprised of three species (i.e. Cercaria capricornia I and II are considered the same species, C. capricornia types III to V are considered to belong to a second species and C. capricornia VI is considered to comprise the third species in this complex). This recognition of reduced diversity following molecular analysis runs contrary to the more frequently reported uncovering of cryptic diversity, especially when larval trematodes are examined. Phylogenetic analysis of these morphologically unusual cercariae supports their inclusion in the Acanthocolpidae. Bayesian inference analysis identifies three distinct clades: (a) Stephanostomum+Monostephanostomum; (b) the Brachycladiidae and Pleorchis; and (c) Tormopsolus and the present cercariae. Genus-level identification of these cercariae remains uncertain given the current lack of available comparative genetic data on nucleic acid databases.

Leptospirosis serology in the common brushtail possum (Trichosurus vulpecula) from urban Sydney, Australia.

The common brushtail possum (Trichosurus vulpecula) is indeed a common marsupial in major cities of Australia. This species is known to be susceptible to leptospirosis and often lives in close contact with humans, raising concerns about the potential for transmission of this disease in urban areas. A total of 192 brushtail possum blood samples were collected from 136 individuals in suburban areas of metropolitan Sydney from November 2002 to November 2004. Sera were screened against a reference panel of 21 Leptospira spp. using the microscopic agglutination test. Leptospiral antibodies were detected in 9.6% (13/136) of tested brushtail possums and represented two serovars; antibodies to Leptospira interrogans serovar Hardjo were most frequently identified (11/136). A representative of the exotic sero-group Ballum, most likely serovar Arborea, was found in two of 136 brushtail possums. Exposure to leptospirosis seemed to be associated with age, as older animals had a higher incidence, but there was no distinction in relation to gender. Antibody prevalence varied between the different sampling sites and seropositive animals were clustered and restricted to a few sites. These data support the possible role of brushtail possums as a maintenance host for Leptospira spp. in urban environments and also identified them as a previously unknown and potential source of serovar Arborea.

A quantitative PCR (TaqMan) assay for pathogenic Leptospira spp.

BACKGROUND: Leptospirosis is an emerging infectious disease. The differential diagnosis of leptospirosis is difficult due to the varied and often "flu like" symptoms which may result in a missed or delayed diagnosis. There are over 230 known serovars in the genus Leptospira. Confirmatory serological diagnosis of leptospirosis is usually made using the microscopic agglutination test (MAT) which relies on the use of live cultures as the source of antigen, often performed using a panel of antigens representative of local serovars. Other techniques, such as the enzyme linked immunosorbent assay (ELISA) and slide agglutination test (SAT), can detect different classes of antibody but may be subject to false positive reactions and require confirmation of these results by the MAT. METHODS: The polymerase chain reaction (PCR) has been used to detect a large number of microorganisms, including those of clinical significance. The sensitivity of PCR often precludes the need for isolation and culture, thus making it ideal for the rapid detection of organisms involved in acute infections. We employed real-time (quantitative) PCR using TaqMan chemistry to detect leptospires in clinical and environmental samples. RESULTS AND CONCLUSIONS: The PCR assay can be applied to either blood or urine samples and does not rely on the isolation and culture of the organism. Capability exists for automation and high throughput testing in a clinical laboratory. It is specific for Leptospira and may discriminate pathogenic and non-pathogenic species. The limit of detection is as low as two cells.

A review of the currently recognised opecoelid cercariae, including the identification and emergence ecology of Cercaria capricornia XII (Digenea: Opecoelidae) from Nassarius olivaceus (Gastropoda: Nassariidae) in Central Queensland, Australia.

A new opecoelid cercaria, Cercaria capricornia XII, is reported from Nassarius olivaceus in Capricornia, Central Queensland, Australia. Combined molecular and morphological data indicate that this cercaria is a member of the subfamily Opecoelinae. Cercaria capricornia XII is the first known opecoeline cercaria reported from a nassariid gastropod. Cercaria capricornia XII can be distinguished from other opecoelid cercariae by the combination of the presence of a 2-pointed stylet, body length and width, and the size of the tail. The emergence pattern for C. capricornia XII in captivity was erratic; rapid emergences of thousands of cercariae were interspersed by periods that sometimes exceeded a month in which no emergence occurred. There was no detectable pattern to or stimulus of the emergence. The molluscan host range of opecoelids is analysed in detail. Gastropods from the Buccinoidea, Cerithioidea and Rissooidea are hosts to both opecoeline and plagioporine cercariae, but the dominant subfamily infecting the Cerithioidea and Rissooidea is the Plagioporinae. The dominant marine host gastropod superfamily for opecoeline cercariae is the Buccinoidea; the family Nassariidae is contained in the Buccinoidea. The range of gastropod superfamilies known as hosts of plagioporines is much broader than that for opecoelines, which may be explained by the relative size of the two opecoelid families and perhaps by indications that the Plagioporinae is polyphyletic.