Paola Vaz

Publications (6) View all

• Article: Detection of a second novel gammaherpesvirus in a free-ranging koala (Phascolarctos cinereus).

  Paola Vaz, Pam L Whiteley, Colin R Wilks, Glenn F Browning, James R Gilkerson, Nino Ficorilli, Joanne M Devlin
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  ABSTRACT: A second novel gammaherpesvirus was detected in a free-ranging koala (Phascolarctos cinereus) shown previously to be infected with phascolarctid herpesvirus 1. Analysis of the DNA polymerase gene showed that the virus was genetically distinct from all known gammaherpesviruses. This is the first reported dual gammaherpesvirus infection in an Australian marsupial.
  Journal of wildlife diseases 01/2012; 48(1):226-9. · 1.08 Impact Factor
• Article: Horizontal transmission dynamics of a glycoprotein G deficient candidate vaccine strain of infectious laryngotracheitis virus and the effect of vaccination on transmission of virulent virus.

  Joanne M Devlin, Carol A Hartley, James R Gilkerson, Mauricio J C Coppo, Paola Vaz, Amir H Noormohammadi, Ben Wells, Ambrosio Rubite, Navneet K Dhand, Glenn F Browning
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  ABSTRACT: Infectious laryngotracheitis virus (ILTV) is an alphaherpesvirus that causes acute respiratory disease in chickens worldwide. The virus is horizontally transmitted and causes large outbreaks of disease. Recent studies have shown that a glycoprotein G deficient candidate vaccine strain of ILTV (ΔgG ILTV) is safe and protects birds from disease following challenge with virulent virus. This study examined the transmission dynamics of this candidate vaccine and of ILTV in field and experimental settings. The reproduction ratio (R₀, average number of secondary infectious cases from a typical infectious case) was calculated from the growth rate of disease epidemics in broiler flocks. Assuming a latent period of 2 days and an infectious period of 4 days R₀ was estimated to be 2.43 (95% CI 2.25-2.69). In experimental settings the transmission characteristics of ΔgG ILTV were similar to those of wildtype virus, and importantly ΔgG ILTV remained safe following one in vivo passage and subsequent infection via contact-exposure. There was minimal transmission of wildtype virus in vaccinated birds. The findings from this study further demonstrate the suitability of ΔgG ILTV for use as a live attenuated vaccine. Knowledge of the basic reproduction ratio of ILTV will be valuable for future studies that aim to improve disease control using vaccination programs.
  Vaccine 06/2011; 29(34):5699-704. · 3.77 Impact Factor
• Article: Detection of a novel gammaherpesvirus in koalas (Phascolarctos cinereus).

  P Vaz, P L Whiteley, C R Wilks, P J Duignan, N Ficorilli, J R Gilkerson, G F Browning, J M Devlin
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  ABSTRACT: A novel gammaherpesvirus was detected in wild koalas (Phascolarctos cinereus) captured at different locations during 2010. Sequence analysis of the DNA polymerase gene revealed that the virus was genetically distinct from all known gammaherpesviruses. This is the first herpesvirus to be definitively identified in the Vombatiforme suborder (koalas and wombats).
  Journal of wildlife diseases 07/2011; 47(3):787-91. · 1.08 Impact Factor
• Article: Gammaherpesvirus infection in a free-ranging eastern grey kangaroo (Macropus giganteus).

  R S Wilcox, P Vaz, N P Ficorilli, P L Whiteley, C R Wilks, J M Devlin
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  ABSTRACT: A gammaherpesvirus was detected by polymerase chain reaction (PCR) in ocular, nasal and oropharyngeal swab samples collected from an adult free-ranging male eastern grey kangaroo (Macropus giganteus) with clinical signs of severe respiratory disease. This is the first time a gammaherpesvirus has been detected in a free-ranging macropod in Australia. The nucleotide sequence of a conserved region of the DNA polymerase gene of the detected virus showed a high degree of identity to a gammaherpesvirus recently detected in a zoological collection of eastern grey kangaroos in North America. The detection of this gammaherpesvirus in a free-ranging, native eastern grey kangaroo provides evidence that this species is a natural host.
  Australian Veterinary Journal 01/2011; 89(1-2):55-7. · 0.94 Impact Factor
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  Available from: Paola Vaz

  Article: NetB, a new toxin that is associated with avian necrotic enteritis caused by Clostridium perfringens.

  Anthony L Keyburn, John D Boyce, Paola Vaz, Trudi L Bannam, Mark E Ford, Dane Parker, Antonio Di Rubbo, Julian I Rood, Robert J Moore
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  ABSTRACT: For over 30 years a phospholipase C enzyme called alpha-toxin was thought to be the key virulence factor in necrotic enteritis caused by Clostridium perfringens. However, using a gene knockout mutant we have recently shown that alpha-toxin is not essential for pathogenesis. We have now discovered a key virulence determinant. A novel toxin (NetB) was identified in a C. perfringens strain isolated from a chicken suffering from necrotic enteritis (NE). The toxin displayed limited amino acid sequence similarity to several pore forming toxins including beta-toxin from C. perfringens (38% identity) and alpha-toxin from Staphylococcus aureus (31% identity). NetB was only identified in C. perfringens type A strains isolated from chickens suffering NE. Both purified native NetB and recombinant NetB displayed cytotoxic activity against the chicken leghorn male hepatoma cell line LMH; inducing cell rounding and lysis. To determine the role of NetB in NE a netB mutant of a virulent C. perfringens chicken isolate was constructed by homologous recombination, and its virulence assessed in a chicken disease model. The netB mutant was unable to cause disease whereas the wild-type parent strain and the netB mutant complemented with a wild-type netB gene caused significant levels of NE. These data show unequivocally that in this isolate a functional NetB toxin is critical for the ability of C. perfringens to cause NE in chickens. This novel toxin is the first definitive virulence factor to be identified in avian C. perfringens strains capable of causing NE. Furthermore, the netB mutant is the first rationally attenuated strain obtained in an NE-causing isolate of C. perfringens; as such it has considerable vaccine potential.
  PLoS Pathogens 03/2008; 4(2):e26. · 9.13 Impact Factor