Experimental infection of Australian brushtail possums, Trichosurus vulpecula (Phalangeridae : Marsupialia), with Ross River and Barmah Forest viruses by use of a natural mosquito vector system

Brushtail possums, Trichosurus vulpecula Kerr, were experimentally infected with Ross River (RR) or Barmah Forest (BF) virus by Aedes vigilax (Skuse) mosquitoes. Eight of 10 animals exposed to RR virus developed neutralizing antibody, and 3 possums developed high viremia for < 48 hr after infection, sufficient to infect recipient mosquitoes. Two of 10 animals exposed to BF virus developed neutralizing antibody. Both infected possums maintained detectable neutralizing antibody to BF for at least 45 days after infection (log neutralization index > 2.0 at 45 days). Eight possums did not develop neutralizing antibody to BF despite exposure to infected mosquitoes. These results suggest that T. vulpecula may potentially act as a reservoir species for RR in urban areas. However, T. vulpecula infected with BF do not develop viremia sufficient to infect mosquitoes and are unlikely to be important hosts for BF.

Evaluation of liquid Bacillus thuringiensis var. israelensis products for control of Australian Aedes arbovirus vectors

Laboratory bioassay studies were conducted in southeast Queensland, Australia,: on the efficacy of Teknar (R), VectoBac (R) 12AS, and Cybate (R) (active ingredient: 1,200 international toxic units Bacillus thuringiensis var, israelensis [Bti]) against 3rd instars of the arbovirus vectors Aedes aegypti. Ae. notoscriptus, Ae. vigilax, and Ae. camptorhynchus. Probit analyses were then used to determine LD,, (median lethal dose), LD95, and lethal dose ratios (LDR). Aedes aegypti and Ae. notoscriptus, both container-habitat species, tolerated the highest Bti concentrations compared with saltmarsh Ae. vigilax and Ae. camptorhynchus. For example, the LDR for Ae. vigilax versus Ae. notoscriptus exposed to Cybate was 0.14 (95% confidence limit [CL] 0.03-0.61). Similarly, the Cybate LDR for Ae. camptorhynchus versus Ae. notoscriptus was 0.22 (95% CL 0.07-0.70). Teknar produced similar results with an LDR of 0.21 (95% CL 0.04-1.10) for Aedes vigilax versus Aedes notoscriptus. Differences in product efficacy were found when tested against the 2 container-breeding species. Cybate was less effective than Teknar with LDRs of 1.55 (95% CL 0.65-3.67) and 1.87 (95% CL 0.68-5.15) for Aedes aegypti and Ae. notoscriptus, respectively. The significant differences in susceptibility between mosquito species and varying efficacy between products highlight the importance of evaluating concentration-response data prior to contracting with distributors of mosquito control products. This information is crucial to resistance management strategies.

Body size and risk of extinction in Australian mammals

The link between body size and risk of extinction has been the focus of much recent attention. For Australian terrestrial mammals this link is of particular interest because it is widely believed that species in the intermediate size range of 35-5500 g (the critical weight range) have been the most prone to recent extinction. But the relationship between body size and extinction risk in Australian mammals has never been subject to a robust statistical analysis. Using a combination of randomization tests and phylogenetic comparative analyses, we found that Australian mammal extinctions and declines have been nonrandom with respect to body size, but we reject the hypothesis of a critical weight range at intermediate sizes. Small species appear to be the least prone to extinction, but extinctions have not been significantly clustered around intermediate sizes. Our results suggest that hypotheses linking intermediate body size with high risk of extinction in Australian mammals are misguided and that the focus of future research should shift to explaining why the smallest species are the most resistant to extinction.

Resolution of natural groups using iterative assignment tests: an example from two species of Australian native rats (Rattus)

Sympatric individuals of Rattus fuscipes and Rattus leucopus, two Australian native rats from the tropical wet forests of north Queensland, are difficult to distinguish morphologically and are often confused in the field. When we started a study on fine-scale movements of these species, using microsatellite markers, we found that the species as identified in the field did not form coherent genetic groups. In this study, we examined the potential of an iterative process of genetic assignment to separate specimens from distinct (e.g. species, populations) natural groups. Five loci with extensive overlap in allele distributions between species were used for the iterative process. Samples were randomly distributed into two starting groups of equal size and then subjected to the test. At each iteration, misassigned samples switched groups, and the output groups from a given round of assignment formed the input groups for the next round. All samples were assigned correctly on the 10th iteration, in which two genetic groups were clearly separated. Mitochondrial DNA sequences were obtained from samples from each genetic group identified by assignment, together with those of museum voucher specimens, to assess which species corresponded to which genetic group. The iterative procedure was also used to resolve groups within species, adequately separating the genetically identified R. leucopus from our two sampling sites. These results show that the iterative assignment process can correctly differentiate samples into their appropriate natural groups when diagnostic genetic markers are not available, which allowed us to resolve accurately the two R. leucopus and R. fuscipes species. Our approach provides an analytical tool that may be applicable to a broad variety of situations where genetic groups need to be resolved.

Revision of Australian Clistoabdominalis (Diptera : Pipunculidae)

The 29 Australian species of Clistoabdominalis Skevington are revised and a phylogenetic analysis is presented. The following 23 new species are proposed: Clistoabdominalis ancylus, C. angelikae, C. capillifascis, C. carnatistylus, C. collessi, C. colophus, C. condylostylus, C. danielsi, C. dasymelus, C. digitatus, C. exallus, C. gaban, C. gremialis, C. lambkinae, C. lingulatus, C. mathiesoni, C. nutatus, C. octiparvus, C. scalenus, C. scintillatus, C. tasmanicus, C. tharra, and C. yeatesi. Pipunculus picrodes Perkins is proposed as a junior synonym of C. trochanteratus (Becker). Diagnoses and an illustrated key to species are provided. A summary of host records for all Australian species of Pipunculidae is presented to clarify confusion in the literature. Pipunculidae are documented hilltopping for the first time. This mating strategy is used by many species of Clistoabdominalis and patterns of hilltopping within the genus are examined.

Alcoholic liver disease: A clinical series in an Australian private practice

Background and Aim: The published literature on alcoholic liver disease (ALD) in Australia lacks a large clinical series out of private practice as distinct from hospital-based hepatology referral units. This series describes the presentation and clinical features of ALD in a consecutive series out of metropolitan private practice in Australia. Methods: A retrospective descriptive study by case-note review found 297 cases of ALD at a Brisbane practice over 20 years. The main outcome measures were: clinical features and stage at presentation, reasons for referral, and the predictive value of aspartate aminotransferase (AST)/alanine aminotransferase (ALT) ratio. Results: Most patients (57.9%) had no symptoms of liver disease and 29 patients (9.8%) had neither symptoms nor signs. Cirrhosis was found in 41% of patients and hepatitis-fibrosis was found in 26% of patients. The male to female (M: F) ratio was 4.7:1. The AST/ALT ratio was not reliably predictive of ALD stage. The average reported daily alcohol intake was 131 g. Females drank less on average and presented a more vigorous clinical picture. Conclusions: This series presents the spectrum of ALD in a metropolitan Australian private practice. Many patients are asymptomatic on presentation. All heavy drinkers should be targeted for early investigation without waiting for volunteered symptoms or abnormal physical signs. The male to female ratio in ALD is higher than hitherto reported. The AST/ALT ratio is not generally applicable in the staging of ALD. The differences from hospital series data suggest the demography and epidemiology of ALD in Australia are incomplete, and further study is warranted. (C) 2001 Blackwell Science Asia Pty Ltd.