Early Decision Indicators for Foot-and-Mouth Disease Outbreaks in Non-Endemic Countries.

Disease managers face many challenges when deciding on the most effective control strategy to manage an outbreak of foot-and-mouth disease (FMD). Decisions have to be made under conditions of uncertainty and where the situation is continually evolving. In addition, resources for control are often limited. A modeling study was carried out to identify characteristics measurable during the early phase of a FMD outbreak that might be useful as predictors of the total number of infected places, outbreak duration, and the total area under control (AUC). The study involved two modeling platforms in two countries (Australia and New Zealand) and encompassed a large number of incursion scenarios. Linear regression, classification and regression tree, and boosted regression tree analyses were used to quantify the predictive value of a set of parameters on three outcome variables of interest: the total number of infected places, outbreak duration, and the total AUC. The number of infected premises (IPs), number of pending culls, AUC, estimated dissemination ratio, and cattle density around the index herd at days 7, 14, and 21 following first detection were associated with each of the outcome variables. Regression models for the size of the AUC had the highest predictive value (R2 = 0.51-0.9) followed by the number of IPs (R2 = 0.3-0.75) and outbreak duration (R2 = 0.28-0.57). Predictability improved at later time points in the outbreak. Predictive regression models using various cut-points at day 14 to define small and large outbreaks had positive predictive values of 0.85-0.98 and negative predictive values of 0.52-0.91, with 79-97% of outbreaks correctly classified. On the strict assumption that each of the simulation models used in this study provide a realistic indication of the spread of FMD in animal populations. Our conclusion is that relatively simple metrics available early in a control program can be used to indicate the likely magnitude of an FMD outbreak under Australian and New Zealand conditions.

Identifying areas of Australia at risk for H5N1 avian influenza infection from exposure to nomadic waterfowl moving throughout the Australo-Papuan region.

Since 2003, highly pathogenic avian influenza (HPAI) due to the H5N1 virus has been reported from both domestic poultry and wild birds in over 60 countries and this has resulted in the direct death or slaughter of over 250 million birds. The potential for HPAI to be introduced to Australian commercial poultry via migratory shorebirds returning from Asia has previously been assessed as a low risk. However, introduction of HPAI from areas to the immediate north of Australia via nomadic waterfowl that range throughout the Australo-Papuan region provides a second potential pathway of entry. Surveillance programmes provide an important early warning for Australia's estimated 2,000 commercial poultry farms but to be efficient they should be risk-based and target resources at those areas and sectors of the industry at higher risk of exposure. In order to address this need, this study compared the distribution and movement patterns of native waterfowl to identify regions where the likelihood of HPAI incursion and establishment was highest. Analysis of bird banding records provided information on the maximum distances moved and dispersal patterns of the species of waterfowl of interest. Introduction via Cape York was found to be most likely and all poultry farms in Queensland were found to be within range of waterfowl that can shed H5N1 virus for up to 17 days. The final analysis showed that the area at greatest risk of HPAI introduction is the Atherton tableland near Cairns.

Identifying areas of Australia at risk of H5N1 avian influenza infection from exposure to migratory birds: a spatial analysis.

Since 2003, highly pathogenic avian influenza (HPAI) due to H5N1 virus has been reported from both domestic poultry and wild birds in 60 countries resulting in the direct death or slaughter of over 250,000,000 birds. The potential exists for HPAI to spread to Australia via migratory shorebirds returning from Asia with the most likely pathway of introduction into commercial poultry flocks involving the transfer of HPAI from migrating shorebirds to native waterfowl species that subsequently interact with poultry on low security poultry farms. Surveillance programmes provide an important early-warning for Australia's estimated 2,000 commercial poultry farms but, to be efficient, they should be risk-based and target resources at those areas and sectors of the industry at higher risk of exposure. This study compared the distributions of migratory shorebirds and native waterfowl to identify six regions where the likelihood of exotic HPAI incursion and establishment in native waterfowl is highest. Analysis of bird banding records showed that native waterfowl did not move further than 10 km during the spring breeding season when migratory shorebirds arrived in Australia. Therefore, poultry farms within 10 km of significant shorebird habitat in these six regions of highest comparative risk were identified. The final analysis showed that the estimated risk to Australia is low with only two poultry farms, one at Broome and one at Carnarvon, located in the regions of highest risk.

Detection of gill-associated virus (GAV) by in situ hybridization during acute and chronic infections of Penaeus monodon and P. esculentus.

Chronic and acute gill-associated virus (GAV) infections were examined by in situ hybridization (ISH) using a DNA probe targeting a 779 nucleotide region of the ORF1b-gene. Chronic GAV infections were observed in healthy Penaeus monodon collected from farms and healthy P. esculentus surviving experimental infection. During chronic-phase infections in both species, GAV was detected only in partitioned foci of cells with hypertrophied nuclei (spheroids) within the lymphoid organ. Acute-phase infections were observed in moribund P. monodon and P. esculentus infected experimentally with a high dose of GAV, and in moribund P. monodon collected from farms during outbreaks of disease. During acute experimental infections in P. monodon, ISH detected GAV throughout the lymphoid organ, in gills and in connective tissues throughout the cephalothorax. In moribund P. monodon collected from natural outbreaks of disease, GAV was also detected in the gills and in connective tissues of the cephalothorax, but the distribution of virus within the lymphoid organ varied. In acutely infected P. esculentus, GAV was detected in connective tissues, but was restricted to the inner stromal matrix cells and endothelial cells of intact lymphoid organ tubules. The tissue distribution of GAV identified by ISH suggests that shrimp are able to control and maintain chronic asymptomatic infection by a process involving lymphoid organ spheroids. Acute phase infections and the development of disease appear to be dose-related and involve the systemic distribution of virus in connective tissues throughout the cephalothorax.

A single amino acid deletion in the antigen binding site of BoLA-DRB3 is predicted to affect peptide binding.

Two bovine MHC class II alleles, BoLA-DRB3*0201 and BoLA-DRB3*3301, contain a three base pair deletion which results in the deletion of a lysine (K beta 65) in the antigen recognition site (ARS). Modelling of BoLA-DRB3*0201 with the conserved lysine K beta 65 and BoLA-DRB3*0201 without K beta 65 indicated that this deletion altered the peptide specificity of the ARS, and may impact on the immune response. To test this hypothesis, the presence of K beta 65 was analysed in a sample of cattle vaccinated with the commercial cattle tick vaccine (TickGARD). Homozygous deletion of K beta 65 was significantly associated with high response to TickGARD (P<0.05). Screening of the TickGARD antigen identified a potential T cell epitope that is recognised better by animals that are homozygous for the K beta 65 deletion. This study provides evidence that changes in the ARS of MHC class II molecules may be associated with the well recognised animal to animal variation in magnitude of vaccine response.