Problems can arise when vaccines and wild strains of a chicken herpesvirus recombine.

Our findings have important implications for the conservation of this iconic species, particularly regarding translocation potential of Victorian koalas.

ABSTRACT:Chlamydia infection is known to impact the health of koalas (Phascolarctos cinereus) in New South Wales (NSW) and Queensland, but the clinical significance of Chlamydia infections in Victorian koalas is not well described. We examined the prevalence of Chlamydia infection and assessed associated health parameters in two Victorian koala populations known to be Chlamydia positive. The same testing regimen was applied to a third Victorian population in which Chlamydia had not been detected. We examined 288 koalas and collected samples from the urogenital sinus and conjunctival sacs. Detection and differentiation of Chlamydia species utilized real-time PCR and high-resolution melting curve analysis. Chlamydia pecorum was detected in two populations (prevalences: 25% and 41%, respectively) but only from urogenital sinus swabs. Chlamydia was not detected in the third population. Chlamydia pneumoniae was not detected. Chlamydia pecorum infection was positively associated with wet bottom (indicating chronic urinary tract disease) in one Chlamydia-positive population and with abnormal urogenital ultrasound findings in the other Chlamydia-positive population. The prevalence of wet bottom was similar in all populations (including the Chlamydia-free population), suggesting there is another significant cause (or causes) of wet bottom in Victorian koalas. Ocular disease was not observed. This is the largest study of Chlamydia infection in Victorian koalas, and the results suggest the potential for epidemiologic differences related to Chlamydia infections between Victorian koalas and koalas in Queensland and NSW and also between geographically distinct Victorian populations. Further studies to investigate the genotypes of C. pecorum present in Victorian koalas and to identify additional causes of wet bottom in koalas are indicated.

Recombination in alphaherpesviruses allows evolution to occur in viruses that have an otherwise stable DNA genome with a low rate of nucleotide substitution. High-throughput sequencing of complete viral genomes has recently allowed natural (field) recombination to be studied in a number of different alphaherpesviruses, however, such studies have not been applied to equine herpesvirus 1 (EHV-1) or equine herpesvirus 4 (EHV-4). These two equine alphaherpesviruses are genetically similar, but differ in their pathogenesis and epidemiology. Both cause economically significant disease in horse populations worldwide. This study used highthroughput sequencing to determine the full genome sequences of EHV-1 and EHV-4 isolates (11 and 14 isolates, respectively) from Australian or New Zealand horses. These sequences were then analysed and examined for evidence of recombination. Evidence of widespread recombination was detected in the genomes of the EHV-4 isolates. Only one potential recombination event was detected in the genomes of the EHV-1 isolates, even when the genomes from an additional 11 international EHV-1 isolates were analysed. The results from this study reveal another fundamental difference between the biology of EHV-1 and EHV-4. The results may also be used to help inform the future safe use of attenuated equine herpesvirus vaccines.

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Infectious bronchitis virus (IBV) is a coronavirus that causes upper respiratory, renal and/or reproductive diseases with high morbidity in poultry. Classification of IBV is important for implementation of vaccination strategies to control the disease in commercial poultry. Currently, the lengthy process of sequence analysis of the IBV S1 gene is considered the gold standard for IBV strain identification, with a high nucleotide identity (e.g. > or =95%) indicating related strains. However, this gene has a high propensity to mutate and/or undergo recombination, and alone it may not be reliable for strain identification. A real-time polymerase chain reaction (RT-PCR) combined with high-resolution melt (HRM) curve analysis was developed based on the 3'UTR of IBV for rapid detection and classification of IBV from commercial poultry. HRM curves generated from 230 to 435-bp PCR products of several IBV strains were subjected to further analysis using a mathematical model also developed during this study. It was shown that a combination of HRM curve analysis and the mathematical model could reliably group 189 out of 190 comparisons of pairs of IBV strains in accordance with their 3'UTR and S1 gene identities. The newly developed RT-PCR/HRM curve analysis model could detect and rapidly identify novel and vaccine-related IBV strains, as confirmed by S1 gene and 3'UTR nucleotide sequences. This model is a rapid, reliable, accurate and non-subjective system for detection of IBVs in poultry flocks.

Infectious laryngotracheitis virus (ILTV; Gallid herpesvirus 1) is an alphaherpesvirus that causes acute respiratory disease in chickens. The role of glycoprotein G (gG) in vitro has been investigated in a number of alphaherpesviruses, but the relevance of gG in vivo in the pathogenicity of ILTV or in other alphaherpesviruses is unknown. In this study, gG-deficient mutants of ILTV were generated and inoculated into specific-pathogen-free chickens to assess the role of gG in pathogenicity. In chickens, gG-deficient ILTV reached a similar titre to wild-type (wt) ILTV but was significantly attenuated with respect to induction of clinical signs, effect on weight gain and bird mortality. In addition, an increased tracheal mucosal thickness, reflecting increased inflammatory cell infiltration at the site of infection, was detected in birds inoculated with gG-deficient ILTV compared with birds inoculated with wt ILTV. The reinsertion of gG into gG-deficient ILTV restored the in vivo phenotype of the mutant to that of wt ILTV. Quantitative PCR analysis of the expression of the genes adjacent to gG demonstrated that they were not affected by the deletion of gG and investigations in vitro confirmed that the phenotype of gG-deficient ILTV was consistent with unaltered expression of these adjacent genes. This is the first reported study to demonstrate definitively that gG is a virulence factor in ILTV and that deletion of gG from this alphaherpesvirus genome causes marked attenuation of the virus in its natural host.

In contrast to the RNA viruses, the genome of large DNA viruses such as herpesviruses have been considered to be relatively stable. Intra-specific recombination has been proposed as an important, but underestimated, driving force in herpesvirus evolution. Recently, two distinct field strains of infectious laryngotracheitis virus (ILTV) have been shown to have arisen from independent recombination events between different commercial ILTV vaccines. In this study we sequenced the genomes of additional ILTV strains and also utilized other recently updated complete genome sequences of ILTV to confirm the existence of a number of ILTV recombinants in nature. Multiple recombination events were detected in the unique long and repeat regions of the genome, but not in the unique short region. Most recombinants contained a pair of crossover points between two distinct lineages of ILTV, corresponding to the European origin and the Australian origin vaccine strains of ILTV. These results suggest that there are two distinct genotypic lineages of ILTV and that these commonly recombine in the field.