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Pizzatto L.,University of Sydney | Shilton C.M.,Berrimah Veterinary Laboratories | Shine R.,University of Sydney
Journal of Wildlife Diseases | Year: 2010

Host-parasite systems have often evolved over time, such that infection dynamics may become greatly modified from the time of initial contact of the host with the parasite. Biological invasions may be useful to clarify processes in the initial contact of hosts with parasites, and allow us to compare parasite uptake between the ancestral (coevolved) host and novel (noncoevolved) hosts. Cane toads (Bufo marinus) are spreading rapidly through tropical Australia, carrying with them a nematode lungworm (Rhabdias pseudosphaerocephala) congeneric with those found in Australian frogs. We investigated the dynamics of infections of the toad parasite by conducting histologic examinations of cane toads and three native Australian frogs (Litoria dahlii, Litoria nasuta, and Opisthodon ornatus) at 2, 6, and 10 days after experimental exposure to the toad lungworm. More worms were found in toads than in frogs, especially at longer periods postexposure. In toads, the infective larvae entered the skin and muscles within 2 days postexposure, passed into the coelom in 6 days, and reached the lungs at 10 days. In frogs, larvae were found in many organs rather than migrating to consistent target tissues; a few larvae reached the lungs of L. dahlii. Migratory larvae caused increasing inflammation (primarily granulomatous admixed with granulocytes then lymphocytes) through time, especially in frogs. Evolution has resulted in an enhanced ability of the lungworm to locate the target organ (the lungs) of the toad, and an increase in rates of parasite survival within this host. © Wildlife Disease Association 2010. Source


Brown G.P.,University of Sydney | Shilton C.M.,Berrimah Veterinary Laboratories | Shine R.,University of Sydney
Methods in Ecology and Evolution | Year: 2011

1. Measuring the degree of skin-swelling induced by intradermal injection of phytohemagglutinin (PHA) is simple, quick and inexpensive, does not require specialized equipment and is easily conducted under field conditions. 2.PHA is perhaps the most frequently used assay of immunocompetence in field studies of birds. However, the method has rarely been used, and never validated, for studies on ectothermic vertebrates. 3.Here, we document its use in an amphibian. In response to PHA injected into a toe web, cane toads exhibited a 35% increase in web thickness 24h postinjection. 4.Histologically, PHA injection initiated a rapid (<12h) infiltration of neutrophils, eosinophils and macrophages at the injection site, followed by an influx of lymphocytes by 24h postinjection. A second exposure to PHA stimulated a faster, more intense swelling response. 5.In cane toads, PHA injection elicits a rapid innate immune response, followed by a secondary response that may reflect cell-mediated immune activity. Both components are easily quantifiable by the degree of skin-swelling. 6.Hence, PHA injection offers a convenient assay to quantify immune function in anurans and could usefully be incorporated into studies on the reasons for global amphibian declines. © 2011 The Authors. Methods in Ecology and Evolution © 2011 British Ecological Society. Source


Nelson F.B.L.,University of Sydney | Brown G.P.,University of Sydney | Shilton C.,Berrimah Veterinary Laboratories | Shine R.,University of Sydney
International Journal for Parasitology: Parasites and Wildlife | Year: 2015

The cane toad invasion in Australia provides a robust opportunity to clarify the infection process in co-evolved versus de novo host-parasite interactions. We investigated these infection dynamics through histological examination following experimental infections of metamorphs of native frogs (Cyclorana australis) and cane toads (Rhinella marina) with Rhabdias hylae (the lungworm found in native frogs) and Rhabdias pseudosphaerocephala (the lungworm found in cane toads). Cane toads reared under continuous exposure to infective larvae of the frog lungworm were examined after periods of 2, 6, 10 and 15 days. Additionally, both toads and frogs were exposed for 24 h to larvae of either the toad or the frog lungworm, and examined 2, 5, 10 and 20 days post-treatment. R. hylae (frog) lungworms entered cane toads and migrated through the body but were not found in the target tissue, the lungs. Larvae of both lungworm species induced inflammation in both types of hosts, although the immune response (relative numbers of different cell types) differed between hosts and between parasite species. Co-evolution has modified the immune response elicited by infection and (perhaps for that reason) has enhanced the parasite's ability to survive and to reach the host's lungs. © 2015 The Authors. Source


Milic N.L.,Charles Darwin University | Davis S.,Berrimah Veterinary Laboratories | Carr J.M.,Flinders University | Isberg S.,Charles Darwin University | And 3 more authors.
Developmental and Comparative Immunology | Year: 2015

A number of pathogens have been detected in crocodiles, however little is known about their ability to control these pathogens. The interferon stimulated gene (ISG), viperin, has gained attention recently as an important host protein involved in multiple arms of the immune response. Viperin in concert with a number of other ISGs was upregulated in response to viral nucleic acid mimics and sendai virus in the C. porosus cell line, LV-1, indicating an intact early innate response to viral infection in these animals for the first time. Viperin was cloned from the LV-1 cell line and shown to have similar localisation patterns as human viperin, as well as demonstrating extremely high conservation with the human orthologue, excepting at the N-terminus. Interestingly, C. porosus viperin was also able to inhibit Dengue virus replication in vitro, showing a high level of intact functionality for this protein across divergent animal species, and perhaps demonstrating its importance in the early innate response to pathogens in the animal kingdom. © 2015 Elsevier Ltd. Source


Hick P.,University of Sydney | Schipp G.,Berrimah Veterinary Laboratories | Bosmans J.,Darwin Aquaculture Center | Humphrey J.,Berrimah Veterinary Laboratories | Whittington R.,University of Sydney
Aquaculture | Year: 2011

Betanodavirus is a significant constraint to marine finfish aquaculture worldwide and the development of control strategies will depend on accurate data about mechanisms of infection. A repeated cross-sectional survey for betanodavirus infection using a real-time reverse transcriptase-polymerase chain reaction assay and virus isolation was conducted in barramundi (Lates calcarifer) at a hatchery in Australia to determine whether transmission occurred vertically from the broodstock or horizontally from the environment. Six consecutive production batches were studied in 2007-2008. Subclinical infection was detected in Batch 2007-1 with onset of infection after 26. d of age, reaching a true prevalence > 90.9% (lower 95% probability limit) by 40. d. Two days later an outbreak of VNN with 100% mortality occurred in 12. d old larvae in Batch 2007-2, due to infection with an identical betanodavirus, which was not detected in this batch 7. d previously. A point source epidemic initiated by horizontal transmission from the environment (probably seawater) to Batch 1 then Batch 2 was confirmed. Betanodavirus was not endemic in the hatchery and was probably not vertically transmitted because: (i) infection was not detected in the eggs or larvae of any batch; (ii) infection was not detected in 4 out of 6 batches; (iii) infection was not identified in 20 broodstock; iv) freedom from infection of life history stages was determined with a very high degree of confidence; v) similar data were derived from archival samples from a batch in 2005. The data suggested that outbreaks were initiated because of vulnerabilities in the water supply and spread because biosecurity measures failed. The age of fish appeared to be a major risk factor for susceptibility to disease. © 2011 Elsevier B.V. Source

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