A review of the Acanthocephala parasitising freshwater fishes in Australia.

The acanthocephalan fauna of Australian freshwater fishes was documented from field surveys, a literature survey and examination of specimens registered in Australian museums. From the 4030 fishes, representing 78 of the 354 Australian freshwater fish species (22%), examined for infection seven species of acanthocephalan were recovered. These species comprised five endemic species, three in endemic genera, two species in cosmopolitan genera, one species not fully identified and 1 putative exotic species recovered from eight species of fish. Of these Edmonsacanthus blairi from Melanotaenia splendida, was the only acanthocephalan found at a relatively high prevalence of 38·6%. These findings are indicative of a highly endemic and possibly depauperate acanthocephalan fauna. Species richness was higher in the tropical regions than the temperate regions of the country. Exotic acanthocephalan species have either not been introduced with their exotic hosts or have been unable to establish their life cycles in Australian conditions. Consequently, acanthocephalans have not yet invaded endemic Australian fish hosts.

First detection of Edwardsiella ictaluri (Proteobacteria: Enterobacteriaceae) in wild Australian catfish.

The bacterium Edwardsiella ictaluri is considered to be one of the most significant pathogens of farmed catfish in the United States of America and has also caused mortalities in farmed and wild fishes in many other parts of the world. E. ictaluri is not believed to be present in wild fish populations in Australia, although it has previously been detected in imported ornamental fishes held in quarantine facilities. In an attempt to confirm freedom from the bacterium in Australian native fishes, we undertook a risk-based survey of wild catfishes from 15 sites across northern Australia. E. ictaluri was detected by selective culturing, followed by DNA testing, in Wet Tropics tandan (Tandanus tropicanus) from the Tully River, at a prevalence of 0.40 (95% CI 0.21-0.61). The bacterium was not found in fishes sampled from any of the other 14 sites. This is the first report of E. ictaluri in wild fishes in Australia.

Phylogenetic Pattern, Evolutionary Processes and Species Delimitation in the Genus Echinococcus.

An accurate and stable alpha taxonomy requires a clear conception of what constitutes a species and agreed criteria for delimiting different species. An evolutionary or general lineage concept defines a species as a single lineage of organisms with a common evolutionary trajectory, distinguishable from other such lineages. Delimiting evolutionary species is a two-step process. In the first step, phylogenetic reconstruction identifies putative species as groups of organisms that are monophyletic (share a common ancestor) and exclusive (more closely related to each other than to organisms outside the group). The second step is to assess whether members of the group possess genetic exchangeability (where cohesion is maintained by gene flow among populations) or ecological exchangeability (where cohesion is maintained because populations occupy the same ecological niche). Recent taxonomic reviews have recognized nine species within the genus Echinococcus. Phylogenetic reconstructions of the relationships between these putative species using mtDNA and nuclear gene sequences show that for the most part these nine species are monophyletic, although there are important incongruences that need to be resolved. Applying the criteria of genetic and ecological exchangeability suggests that seven of the currently recognized species represent evolutionarily distinct lineages. The species status of Echinococcus canadensis and Echinococcus ortleppi could not be confirmed. Coalescent-based analyses represent a promising approach to species delimitation in these closely related taxa. It seems likely, from a comparison of sister species groups, that speciation in the genus has been driven by geographic isolation, but biogeographic scenarios are largely speculative and require further testing.

Cryptosporidium species in sheep and goats from Papua New Guinea.

Species of Cryptosporidium are extensively recognised as pathogens of domesticated livestock and poultry, companion animals, wildlife, and are a threat to public health. Little is known of the prevalence of Cryptosporidium spp. in humans, domesticated animals or wildlife in Papua New Guinea (PNG). The aim of the present study was to screen sheep and goats for Cryptosporidium using molecular tools. A total of 504 faecal samples were collected from sheep (n=276) and goats (n=228) in village, government and institutional farms in PNG. Samples were screened by nested PCR and genotyped at the 18S rRNA and at the 60kDa glycoprotein (gp60) loci. The overall prevalences were 2.2% for sheep (6/278) and 4.4% (10/228) for goats. The species/genotypes identified were Cryptosporidium hominis (subtype IdA15G1) in goats (n=6), Cryptosporidium parvum (subtypes IIaA15G2R1and IIaA19G4R1) in sheep (n=4) and in goats (n=2), Cryptosporidium andersoni (n=1) and Cryptosporidium scrofarum (n=1) in sheep, Cryptosporidium xiao (n=1) and Cryptosporidium rat genotype II (n=1) in goats. This is the first report of Cryptosporidium spp. identified in sheep and goats in PNG. Identification of Cryptosporidium in livestock warrants better care of farm animals to avoid contamination and illness in vulnerable population. The detection of zoonotic Cryptosporidium in livestock suggests these animals may serve as reservoirs for human infection.

Identification of novel and zoonotic Cryptosporidium species in fish from Papua New Guinea.

There is still limited information on the distribution of Cryptosporidium species and genotypes in fish. The present study investigated the prevalence of Cryptosporidium species in cultured freshwater (n=132), wild freshwater (n=206) and wild marine (n=276) fish in Papua New Guinea (PNG) by PCR screening at the 18S rRNA locus. A total of seven fish (2 cultured freshwater, 1 wild freshwater and 4 wild marine fish) were identified as positive for Cryptosporidium. Specifically, Cryptosporidium was found in four different host species (Nile tilapia, Oreochromis niloticus; silver barb, Puntius gonionotus; mackerel scad, Decapterus maracellus and oblong silver biddy, Gerres oblongus), giving an overall prevalence of 1.14% (95% CI: 0.3-2%, n=7/614). Of the seven positive isolates, five were identified as C. parvum and two were a novel piscine genotype, which we have named piscine genotype 8. Piscine genotype 8 was identified in two marine oblong silver biddies and exhibited 4.3% genetic distance from piscine genotype 3 at the 18S locus. Further subtyping of C. parvum isolates at the 60 kDa glycoprotein (gp60) locus identified 3 C. parvum subtypes (IIaA14G2R1, IIaA15G2R1 and IIaA19G4R1) all of which are zoonotic and a C. hominis subtype (IdA15G1). The zoonotic Cryptosporidium were identified in fish samples from all three groups; cultured and wild freshwater and wild marine fish. Detection of Cryptosporidium among aquaculture fingerlings warrants further research to gain a better understanding of the epidemiology of Cryptosporidium infection in cultured fish. The identification of zoonotic Cryptosporidium genotypes in fish from PNG has important public health implications and should be investigated further.

A high prevalence of Toxoplasma in Australian chickens.

A small survey was undertaken of commercially reared free-range chickens in Western Australia using serology and molecular detection. Eighteen out of 20 serum samples showed antibody responses with titers of 1:64 in 5 chickens and ≥ 1:128 in 13 chickens. DNA extracted from 22 out of 50 tissue samples, 10 brains and 12 spleens, were positive by nested PCR, and sequencing at the B1 locus on DNA from 3 brain and 3 spleen samples confirmed that 2 isolates were Toxoplasma gondii, Type I, and 4 Type II/III. The high prevalence of Toxoplasma infection found in commercial, free-range chickens raises public health issues with respect to both exposure in the workplace, during carcass processing, and subsequent transmission during food handling and/or consumption as food. The results of this study emphasize the need for more data on the incidence of Toxoplasma infection in domestic animals and humans in Australia.

Identification of Anisakis species (Nematoda: Anisakidae) in marine fish hosts from Papua New Guinea.

The third-stage larvae of several genera of anisakid nematodes are important etiological agents for zoonotic human anisakiasis. The present study investigated the prevalence of potentially zoonotic anisakid larvae in fish collected on the coastal shelves off Madang and Rabaul in Papua New Guinea (PNG) where fish represents a major component of the diet. Nematodes were found in seven fish species including Decapterus macarellus, Gerres oblongus, Pinjalo lewisi, Pinjalo pinjalo, Selar crumenophthalmus, Scomberomorus maculatus and Thunnus albacares. They were identified by both light and scanning electron microscopy as Anisakis Type I larvae. Sequencing and phylogenetic analysis of the ribosomal internal transcribed spacer (ITS) and the mitochondrial cytochrome C oxidase subunit II (cox2) gene identified all nematodes as Anisakis typica. This study represents the first in-depth characterisation of Anisakis larvae from seven new fish hosts in PNG. The overall prevalence of larvae was low (7.6%) and no recognised zoonotic Anisakis species were identified, suggesting a very low threat of anisakiasis in PNG.

Infection levels of gastrointestinal parasites in sheep and goats in Papua New Guinea.

Gastrointestinal parasites of livestock cause diseases of important socio-economic concern worldwide. The present study investigated the prevalence of gastrointestinal parasites in sheep and goats in lowland and highland regions of Papua New Guinea (PNG). Faecal samples were collected from a total of 165 small ruminants (110 sheep and 55 goats) from February to April 2011. Analysis by a modified McMaster technique revealed that 128 animals (72% of sheep and 89% of goats) were infected with one or more species of gastrointestinal parasites. The gastrointestinal parasites found and their prevalences in sheep (S) and in goats (G) were as follows: strongyle 67.3% (S), 85.5% (G); Eimeria 17.3% (S), 16.4% (G); Strongyloides, 8.2% (S), 23.6% (G); Fasciola, 5.5% (S), 18.2% (G); Trichuris, 1.8% (S), 3.6% (G); and Nematodirus, 1.8% (S), 3.6% (G). Two additional genera were found in goats: Moniezia (9.1%) and Dictocaulus (3.6%). This is the first study to quantitatively examine the prevalence of gastrointestinal parasites in goats in PNG. The high rates of parasitism observed in the present study are likely to be associated with poor farming management practices, including lack of pasture recovery time, lack of parasite control measures and poor-quality feed.

Additional novel Cryptosporidium genotypes in ornamental fishes.

Current knowledge on the prevalence and genotypes of Cryptosporidium in fishes is still limited. This study investigated the prevalence of Cryptosporidium species in 171 ornamental fishes, belonging to 33 species, collected from 8 commercial aquariums around Perth, Western Australia. All samples were screened by nested PCR targeting the 18S rRNA locus. A total of 6 positives were identified by PCR at the 18S locus from 4 different species of fishes (red eye tetra, Moenkhausia sanctaefilomenae; gold gourami, Trichogaster trichopterus; neon tetra, Paracheirodon innesi; goldfish, Carassius auratus auratus), giving an overall prevalence of 3.5% (6/171). Four different genotypes were identified, only one of which has been previously reported in fish; piscine genotype 4 in a neon tetra isolate, a rat genotype III-like isolate in a goldfish, a novel genotype in three isolates from red eye (piscine genotype 7) which exhibited a 3.5% genetic distance from piscine genotype 1 and a piscine genotype 6-like from a gold gourami (1% genetic distance). Further biological and genetic characterisation is required to determine the relationship of these genotypes to established species and strains of Cryptosporidium.

The molecular epidemiology of parasite infections: tools and applications.

Molecular epidemiology, broadly defined, is the application of molecular genetic techniques to the dynamics of disease in a population. In this review, we briefly describe molecular and analytical tools available for molecular epidemiological studies and then provide an overview of how they can be applied to better understand parasitic disease. A range of new molecular tools have been developed in recent years, allowing for the direct examination of parasites from clinical or environmental samples, and providing access to relatively cheap, rapid, high throughput molecular assays. At the same time, new analytical approaches, in particular those derived from coalescent theory, have been developed to provide more robust estimates of evolutionary processes and demographic parameters from multilocus, genotypic data. To date, the primary application of molecular epidemiology has been to provide specific and sensitive identification of parasites and to resolve taxonomic issues, particularly at the species level and below. Population genetic studies have also been used to determine the extent of genetic diversity among populations of parasites and the degree to which this diversity is associated with different host cycles or epidemiologically important phenotypes. Many of these studies have also shed new light on transmission cycles of parasites, particularly the extent to which zoonotic transmission occurs, and on the prevalence and importance of mixed infections with different parasite species or intraspecific variants (polyparasitism). A major challenge, and one which is now being addressed by an increasing number of studies, is to find and utilize genetic markers for complex traits of epidemiological significance, such as drug resistance, zoonotic potential and virulence.

Parasites of native and exotic freshwater fishes in south-western Australia.

In this study, 1429 fishes of 18 different species (12 native and six exotic) were sampled from 29 localities to compare the levels of parasitism between native and exotic fish species and to examine the relationship between environmental degradation and parasite diversity. Forty-four putative species of parasites were found and most of these appear to be native parasites, which have not previously been described. Two parasite species, Lernaea cyprinacea and Ligula intestinalis, are probably introduced. Both were found on or in a range of native fish species, where they may cause severe disease. Levels of parasitism and parasite diversity were significantly greater in native fishes than in exotic species, and this may contribute to an enhanced demographic performance and competitive ability in invading exotics. Levels of parasitism and parasite diversity in native fishes were negatively related to habitat disturbance, in particular to a suite of factors that indicate increased human use of the river and surrounding environment. This was due principally to the absence in more disturbed habitats of a number of species of endoparasites with complex life cycles, involving transmission between different host species.

Parasites, emerging disease and wildlife conservation.

In this review some emerging issues of parasite infections in wildlife, particularly in Australia, are considered. We discuss the importance of understanding parasite biodiversity in wildlife in terms of conservation, the role of wildlife as reservoirs of parasite infection, and the role of parasites within the broader context of the ecosystem. Using a number of parasite species, the value of undertaking longitudinal surveillance in natural systems using non-invasive sampling and molecular tools to characterise infectious agents is illustrated in terms of wildlife health, parasite biodiversity and ecology.

Giardia in Western Australian wildlife.

Giardia has been found in numerous species of mammalian wildlife but very little information is available on the species and strains/genotypes that occur naturally in mammals in the wild. Recently, a novel genotype of Giardia was described in Western Australia, in the Southern brown bandicoot, or quenda (Isoodon obesulus). In order to determine the host range, distribution and prevalence of this novel 'quenda' 'genotype of Giardia, a comprehensive survey of this marsupial and cohabiting mammalian species was undertaken throughout the mainland and some off-shore islands of Western Australia, including urban areas. The overall prevalence of Giardia in 351 wildlife samples was low, with only 4.8% (17) samples testing positive. Amongst the 51 quenda samples, 11.8% (6) were positive for the 'quenda' genotype, 5.9% (3) for assemblage C/D and 2% (1) for assemblages A and E. This study has demonstrated that Giardia is a remarkably rare parasite in native wildlife in Western Australia, raising questions about the ecology of Giardia infections in wildlife.

The diversity, distribution and host-parasite associations of trypanosomes in Western Australian wildlife.

Little is known regarding the diversity, distribution or host-parasite associations of Trypanosoma spp. in Australian wildlife. Here we report on an investigation based on divergence of the 18S rRNA gene of trypanosomes isolated from a range of hosts and varied geographical locations. A total of 371 individuals representing 19 species of native animals from 14 different locations were screened. In total, 32 individuals from 9 different species tested positive for the parasite. Phylogenetic analysis revealed considerable parasite diversity with no clear geographical distribution and no evidence of host specificity. In general, it appears that Australian Trypanosoma spp. are widespread, with several genotypes appearing in multiple host species and in varied locations including both mainland areas and offshore islands. Some host species were found to be susceptible to multiple genotypes, but no individuals were infected with more than a single isolate.

Trypanosomes in a declining species of threatened Australian marsupial, the brush-tailed bettong Bettongia penicillata (Marsupialia: Potoroidae).

The brush-tailed bettong (Bettongia penicillata), or woylie, is a medium-sized macropod marsupial that has undergone a rapid and substantial decline throughout its home range in the Upper Warren region of Western Australia over a period of approximately 5 years. As part of an investigation into possible causes of the decline a morphologically distinct Trypanosoma sp. was discovered by light microscopy in the declining population but was absent in a stable population within the Karakamia Wildlife Sanctuary. Further investigations employing molecular methods targeting variations in the 18s rRNA gene determined that the trypanosome was novel and was also present within the Karakamia population albeit at a much lower overall prevalence and individual parasitaemia levels. Phylogenetic analysis suggests the novel Trypanosoma sp. to be closely related to other trypanosomes isolated from native Australian wildlife species. Although it appears unlikely that the parasite is solely responsible for the decline in woylie population size, it may (singularly or in conjunction with other infectious agents) predispose woylies to increased mortality.

Larval anisakid infections of some tropical fish species from north-west Australia.

Despite the commercial and zoonotic importance of larval anisakid infestations of teleosts, their distribution among Australia's diverse marine fish fauna is poorly understood. A preliminary survey of Australia's tropical north-west revealed a generally high prevalence of larval anisakids representing four genera (Anisakis, Terranova, Thynnascaris and Raphidascaris) among only seven fish species. The potential impact of high larval anisakid infections on both the health of recreational fishermen and aquaculture environments is discussed.

Larvae of Contracaecum sp. among inshore fish species of southwestern Australia.

Larval nematode infections were investigated in 236 fish from 17 estuarine and near-shore species in southwestern Australia. Larvae of the genus Contracaecum were found in 4 species of fish (Acanthopagrus butcheri, Sillaginodes punctata, Mugil cephalus and Aldrichetta forsteri). The prevalence and intensity of infection was highest in the 2 species of mullet: 81% infected and 9.8 +/- 1.5 larvae fish(-1) for M. cephalus; 100% and 12.7 +/- 3.7 larvae fish(-1) for A. forsteri. There was no evidence of post-mortem migration of worms from the visceral organs to the musculature of the fish.

Teaching of parasitology to students of veterinary medicine and biomedical sciences.

The teaching of an applied parasitology course suitable for both veterinary and biomedical students is described. A common lecture course is given complemented by separate and specific practical, research and problem-based learning components designed for veterinary and biomedical students. For veterinary and biomedical students, teaching of parasitology during the full course comprises a total of 46 lectures; 13 practical classes for veterinary students and five for biomedical students who also undertake an independent research project.

Mitochondrial DNA polymorphisms and fertility in beef cattle.

Four hundred and twenty-two beef cattle of two different breeds (purebred Hereford and composite multibreed) were characterized by polymerase chain reaction-restriction fragment length polymorphism, using the restriction enzymes ApaI, AvaII, HindIII, PstI, SpeI, SspI and TaqI in two regions (the D-loop and the ND-5 gene) of mitochondrial DNA. The association between molecular haplotypes and records on calving rate, defined as the mean number of live calves born per year over 4 years, were examined by analysis of variance. A significant association was found between calving rate and mitochondrial polymorphisms in both breeds. This may have implications for genetically improving cow fertility.