Stakeholder perceptions of thoroughbred yearling sales endoscopy in Australia: can we do better?

OBJECTIVE

To identify thoroughbred industry stakeholders' views on the yearling sales endoscopy in Australia.

DESIGN

Semi-structured qualitative group interviews with equine veterinarians, thoroughbred breeders and yearling purchasers.

METHODS

Twenty-nine experienced thoroughbred industry stakeholders participated in online focus groups: (1) equine veterinarians involved in yearling endoscopy; (2) thoroughbred breeders; and (3) yearling buyers. The focus groups were audio and video recorded and digital whiteboards were available. Data was transcribed, live-coded and analysed thematically.

RESULTS

The main themes identified included the uncertainty surrounding the relationship between yearling laryngeal function and future performance, especially the significance of yearlings with grade 3 out of 5 laryngeal function; interobserver variability in the laryngeal function grade assigned by veterinarians to the same endoscopic exam; and the presence of intra-horse variability in laryngeal function over different time points.

DISCUSSION

Stakeholders raised multiple concerns about the current yearling sales endoscopy process in Australia. Recommendations to address these concerns include further investigation into the race performance of yearlings identified with grade 3 laryngeal function; training of veterinarians to reduce inter-observer variability; and the need to determine the most appropriate grading system to use in yearlings. Future research should evaluate the significance of intra-horse variability in a yearling population.

Discovery of insecticide resistance in field-collected populations of the aphid pest, Acyrthosiphon kondoi Shinji

BACKGROUND

The bluegreen aphid (Acyrthosiphon kondoi) is a worldwide pest of alfalfa, pulses, and other legume crops. An overreliance on insecticides to control A. kondoi has potentially placed populations under selection pressure favouring resistant phenotypes, but to date, there have been no documented cases of insecticide resistance. Recently, Australian growers began reporting that conventional insecticides were failing to adequately control A. kondoi populations, prompting this laboratory-based investigation into whether these populations have evolved resistance.

RESULTS

We discovered four A. kondoi populations with moderate resistance (10-40-fold) to three different insecticide groups: organophosphates, carbamates and pyrethroids. However, A. kondoi populations showed no resistance to the butenolide, flupyradifurone. We were unable to identify general metabolic mechanisms using synergist assays (cytochromes P450, glutathione S-transferases, or esterases), indicating that further detailed molecular investigations to characterise the putative resistance mechanism are needed.

CONCLUSION

Insecticide-resistant A. kondoi present an emerging challenge to Australian agriculture. Growers require new tools and updated strategies, including access to newer chemistries, to alleviate their reliance on the few insecticides currently registered against A. kondoi. The implications of insecticide resistant A. kondoi for future management, the potential mechanisms of resistance, and future research priorities are discussed. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Source attribution of campylobacteriosis in Australia, 2017-2019

Campylobacter jejuni and Campylobacter coli infections are the leading cause of foodborne gastroenteritis in high-income countries. Campylobacter colonizes a variety of warm-blooded hosts that are reservoirs for human campylobacteriosis. The proportions of Australian cases attributable to different animal reservoirs are unknown but can be estimated by comparing the frequency of different sequence types in cases and reservoirs. Campylobacter isolates were obtained from notified human cases and raw meat and offal from the major livestock in Australia between 2017 and 2019. Isolates were typed using multi-locus sequence genotyping. We used Bayesian source attribution models including the asymmetric island model, the modified Hald model, and their generalizations. Some models included an "unsampled" source to estimate the proportion of cases attributable to wild, feral, or domestic animal reservoirs not sampled in our study. Model fits were compared using the Watanabe-Akaike information criterion. We included 612 food and 710 human case isolates. The best fitting models attributed >80% of Campylobacter cases to chickens, with a greater proportion of C. coli (>84%) than C. jejuni (>77%). The best fitting model that included an unsampled source attributed 14% (95% credible interval [CrI]: 0.3%-32%) to the unsampled source and only 2% to ruminants (95% CrI: 0.3%-12%) and 2% to pigs (95% CrI: 0.2%-11%) The best fitting model that did not include an unsampled source attributed 12% to ruminants (95% CrI: 1.3%-33%) and 6% to pigs (95% CrI: 1.1%-19%). Chickens were the leading source of human Campylobacter infections in Australia in 2017-2019 and should remain the focus of interventions to reduce burden.

Bioactivities and Phenolic Profiles of Honeys Derived from Plants of the Goldfields, Esperance and Wheatbelt Regions of Western Australia

The aim of this study was to examine a collection of 79 honeys derived from plants endemic to several Western Australian unique bioregions for bioactivity and physicochemical characteristics. For physicochemical analyses, total phenolic content, high performance thin layer chromatography (HPTLC) fingerprints, pH, Brix, colour and hydrogen peroxide generation were examined. Brix (82.6±1.3) and pH (4.34±0.24) values were within expected ranges, whereas hydrogen peroxide levels determined using an o-dianisidine/horseradish peroxidase assay were relatively low, ranging from 0-244 μM. Antibacterial activity determined by the broth microdilution assay showed that Moort (Eucalyptus platypus) and Yate (Eucalyptus occidentalis) honeys had the highest overall activity with mean minimum inhibitory concentrations of 24.8 % and 25.1 % (w/v) honey, respectively. Yate honey also had the highest overall antioxidant activity (4.38±0.58 mmol Fe2+ /kg of honey), followed by Mallee honeys from various eucalypts, as determined by FRAP (Ferric reducing antioxidant power) and DPPH⋅ (2,2-Diphenyl-1-picrylhydrazyl) assays. This study identified new sources of honeys with potentially useful therapeutic properties from bioregions within Western Australia.

Dominant Salmonella Serovars in Australian Broiler Breeder Flocks and Hatcheries: a Longitudinal Study

A longitudinal study was conducted to determine the dominance and prevalence of Salmonella enterica subsp in Australian broiler breeder flocks and hatcheries. Twenty-two flocks (n = 3339 samples) were sampled over 6 time points beginning at placement until week 40. Hatcheries (n = 274 samples) were sampled following removal of chicks hatched from eggs originating from the 22 donor parent flocks. The percent of positive flocks (36%) and frequency of positive samples (15.6%) were highest during rearing at week 7. The frequency of positive samples decreased over the 40 weeks; however, the number of positive flocks remained relatively consistent. Geographical location had a greater influence on Salmonella detection frequency than company sample origin, despite differing management and vaccination protocols within and between companies. Twelve serovars were detected in total. The predominant serovars during rearing were Salmonella Mbandaka (32%), S. Saintpaul (27%), and S. Liverpool (18%). The predominant serovars detected during production were S. Cubana (27%), S. Saintpaul (24%), and S. Havana (13%). Salmonella Typhimurium, S. Ohio, and S. Hessarek were detected in the hatcheries. Of the serovars detected, only S. Typhimurium and S. Ohio were found in both broiler breeder flocks and hatcheries. However, detection did not correspond to the status of the flock eggs feeding into the hatchery. This study provides an up-to-date capture of the current Salmonella serovars circulating in the broiler breeder industry. Continued surveillance within the Australian Chicken Meat industry is imperative to mitigate and reduce the risk of salmonellosis in the community related to chicken meat. IMPORTANCE This study identified prevalent and dominant Salmonella enterica subsp in Australian Broiler Breeder flocks, as well as in hatcheries post chick hatch and removal, from eggs originating from these donor parent flocks. The captured Salmonella data was further compared to the most common Salmonella serovars isolated from broilers, as well as human salmonellosis notification data, which is useful for consideration of the circulating serovars within the chicken meat industry and their significance in public health. As there are multiple entry points for Salmonella during the entire chicken meat production chain that can lead to carcass contamination, it is important to distinguish serovars present between the different stages of vertical integration to implement and enable Salmonella control strategies.

National participation levels in the 2017-2018 Australian thoroughbred racing season

INTRODUCTION

The social licence of the Australian thoroughbred (TB) industry relies on the general public's perception of how they manage the animal in their care.

METHOD

This study examines the horse, race and activity records for the 37,704 horses racing and training in Australia from 1 August 2017 to 31 July 2018. Three-quarters (75%, n = 28,184) of TBs started in one of the 180, 933 race starts that occurred during the 2017-2018 Australian racing season.

RESULTS

Horses participating in the 2017-2018 Australian racing season had a median age of 4 years, with geldings more likely to be aged 5 years and older. The majority of the TB racehorse population were geldings (51%, n = 19,210), with 44% (n = 16,617) females and only 5% (n = 1877) entire males. Horses aged 2 years were three times more likely to not start in a race in that year compared with older horses. At the end of the 2017-2018 racing season, 34% of the population had an inactive status recorded. Horses aged 2 years (median two starts) and 3 years (median five starts) had fewer starts than older horses (median seven starts). Eighty-eight percent (n = 158,339) of race starts were over distances of 1700 metres or less. Race starts by horses aged 2 years (46%, 3264 of 7100) were more likely to have occurred at a metropolitan meeting compared with starts by older horses.

CONCLUSION

This study provides a national overview of the racing and training activities and TBs participating in the 2017-2018 Australian racing season.

Effects of 2 modes of positive pressure ventilation on respiratory mechanics and gas exchange in foals

BACKGROUND

Continuous positive airway pressure (CPAP) and pressure support ventilation (PSV) can improve respiratory mechanics and gas exchange, but different airway pressures have not been compared in foals.

HYPOTHESIS/OBJECTIVES

Assess the effect of different airway pressures during CPAP and PSV have on respiratory function in healthy foals with pharmacologically induced respiratory insufficiency. We hypothesized that increased airway pressures would improve respiratory mechanics and increased positive end-expiratory pressure (PEEP) would be associated with hypercapnia.

ANIMALS

Six healthy foals from a university teaching herd.

METHODS

A prospective, 2-phase, 2-treatment, randomized cross-over study design was used to evaluate sequential interventions in sedated foals using 2 protocols (CPAP and PSV). Outcome measures included arterial blood gases, spirometry, volumetric capnography, lung volume and aeration assessed using computed tomography (CT).

RESULTS

Sedation and dorsal recumbency were associated with significant reductions in arterial oxygen pressure (PaO₂ ), respiratory rate, and tidal volume. Continuous positive airway pressure was associated with improved PaO₂ , without concurrent hypercapnia. Volumetric capnography identified improved ventilation:perfusion (V/Q) matching and increased carbon dioxide elimination during ventilation, and spirometry identified decreased respiratory rate and increased tidal volume. Peak inspiratory pressure was moderately associated with PaO₂ and lung volume. Improved pulmonary aeration was evident in CT images, and lung volume was increased, particularly during CPAP.

CONCLUSIONS AND CLINICAL IMPORTANCE

Both CPAP and PSV improved lung mechanics and gas exchange in healthy foals with induced respiratory insufficiency.

A chronology of subterranean clover burr detachment mechanics and implications for seed harvestability

Seed retention has not been evaluated for subterranean clover (Trifolium subterraneum L.), because its geocarpic seed-bearing burrs are currently harvested by suction systems. Development of improved harvest methods requires knowledge of subterranean clover seed retention characteristics and their changes with plant development. This study evaluates burr attachment and peduncle tensile strength during burr maturity until plant senescence across the three subspecies: subterraneum (cv. Dalkeith), yanninicum (cv. Monti) and brachycalycinum (cv. Mawson). Peduncle tensile strength was greater than burr-to-peduncle attachment strength for each subspecies, with peak mean peduncle strength 30-130% greater than peak mean burr-to-peduncle attachment strength. Both strength measurements decreased significantly (greater than 50% for each subspecies) as the plant senesced, which was associated with reductions in burr moisture content, and burr and peduncle diameters. Microscopy indicated a ductile to brittle transition as peduncles senesced, reducing energy absorption and increasing the likelihood of failure at defects. These results are important for the commercial production of subterranean clover seed and suggest it may be possible to harvest seed before plant senescence with dig-invert machinery, similar to that used for peanut harvesting. However, this approach would require harvesting prior to maximum seed development and the implications for seed viability and yield need to be further evaluated.

Metagenomic investigation of potential abortigenic pathogens in foetal tissues from Australian horses

BACKGROUND

Abortion in horses leads to economic and welfare losses to the equine industry. Most cases of equine abortions are sporadic, and the cause is often unknown. This study aimed to detect potential abortigenic pathogens in equine abortion cases in Australia using metagenomic deep sequencing methods.

RESULTS

After sequencing and analysis, a total of 68 and 86 phyla were detected in the material originating from 49 equine abortion samples and 8 samples from normal deliveries, respectively. Most phyla were present in both groups, with the exception of Chlamydiae that were only present in abortion samples. Around 2886 genera were present in the abortion samples and samples from normal deliveries at a cut off value of 0.001% of relative abundance. Significant differences in species diversity between aborted and normal tissues was observed. Several potential abortigenic pathogens were identified at a high level of relative abundance in a number of the abortion cases, including Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Streptococcus equi subspecies zooepidemicus, Pantoea agglomerans, Acinetobacter lwoffii, Acinetobacter calcoaceticus and Chlamydia psittaci.

CONCLUSIONS

This work revealed the presence of several potentially abortigenic pathogens in aborted specimens. No novel potential abortigenic agents were detected. The ability to screen samples for multiple pathogens that may not have been specifically targeted broadens the frontiers of diagnostic potential. The future use of metagenomic approaches for diagnostic purposes is likely to be facilitated by further improvements in deep sequencing technologies.

Drivers of exit and outcomes for Thoroughbred racehorses participating in the 2017-2018 Australian racing season

The destinations of Thoroughbred (TB) racehorses exiting the racing industry is a high-profile issue with ethical and welfare implications of interest to both animal welfare groups and racing regulators. This cross-sectional study investigated the reasons that TBs temporarily or permanently exited racing and training in Australia in the 2017–2018 racing season and the outcomes for these horses post-racing. An online questionnaire was sent to the last registered trainers of a representative sample of 2,509 ‘inactive’ TBs. Inactive horses were defined as those horses that were recorded as ‘active’ but had not trialled or raced in the last 6 months of the racing season or had an inactive status recorded in the Racing Australia database. Of the 1,750 responses received, the largest group of inactive TBs had permanently exited the racing industry (45% retired, 5.3% deceased). A relatively large group exited racing temporarily (43%) but participated in the racing industry in the following season. The reasons for retirement were predominantly voluntary, such as poor performance or owner’s request. Almost one third of retirements were due to injuries with tendon or ligament problems the most frequently conditions listed. The median age at retirement was five (Q1 4; Q3 7) years. Extrapolation of the survey results to the population of horses racing or training in Australia in 2017–2018 (n = 37,750) show that that 17% of the population retire each year and 2.1% die. These estimates provide benchmarks for industry and animal welfare organisations to resource and measure the effectiveness of interventions.

Transmission of infectious laryngotracheitis virus vaccine and field strains: the role of degree of contact and transmission by whole blood, plasma and poultry dust

Understanding the mechanisms of transmission of infectious laryngotracheitis virus (ILTV) is critical to proper control as both vaccine and wild-type strains circulate within chicken flocks with potential adverse consequences. The relative efficiency of transmission by direct contact between chickens and airborne transmission has not been investigated. Furthermore, relatively high levels of ILTV DNA have been detected in poultry dust and blood but the infectivity of these is unknown. In this study, comparison of in-contact and airborne transmission of two vaccine and one field strain of ILTV revealed that all transmitted to 100% of in-contact birds by 6 days post-exposure (dpe). Airborne transmission without contact resulted in 100% transmission by 14 and 17 dpe for the wild-type and Serva vaccine virus but only 27% transmission by 21 dpe for the A20 vaccine virus. The infectivity of dust or extracts of dust and blood or plasma from infected chickens at various stages of infection was assessed by inoculation into susceptible chickens. There was no transmission by any of these materials. In conclusion, direct contact facilitated efficient ILTV transmission but the virus was unable to be transmitted by dust from infected chickens suggestive of a limited role in the epidemiology of ILTV.

Comparison of tracheal and choanal cleft swabs and poultry dust samples for detection of Newcastle disease virus and infectious bronchitis virus genome in vaccinated meat chicken flocks

This study assessed different methods (tracheal and choanal cleft swabs from individual birds, and poultry dust as a population level measure) to evaluate the shedding kinetics of infectious bronchitis virus (IBV) and Newcastle disease virus (NDV) genome in meat chicken flocks after spray vaccination at hatchery. Dust samples and tracheal and choanal cleft swabs were collected from four meat chicken flocks at 10, 14, 21 and 31 days post vaccination (dpv) and tested for IBV and NDV genome copies (GC) by reverse transcriptase (RT)-PCR. IBV and NDV GC were detected in all sample types throughout the study period. Detection rates for choanal cleft and tracheal swabs were comparable, with moderate and fair agreement between sample types for IBV (McNemar's = 0.27, kappa = 0.44) and NDV (McNemar's = 0.09; kappa = 0.31) GC respectively. There was no significant association for IBV GC in swabs and dust samples (R2 = 0.15, P = 0.13) but NDV detection rates and viral load in swabs were strongly associated with NDV GC in dust samples (R2 = 0.86 and R2 = 0.90, P<0.001). There was no difference in IBV and NDV GC in dust samples collected from different locations within a poultry house. In conclusion, dust samples collected from any location within poultry house show promise for monitoring IBV and NDV GC in meat chickens at a population level and choanal cleft swabs can be used for detection of IBV and NDV GC instead of tracheal swabs in individual birds.

Stable and Novel Quantitative Trait Loci (QTL) Confer Narrow Root Cone Angle in an Aerobic Rice (Oryza sativa L.) Production System

BACKGROUND

Aerobic rice production (AP) may be a solution to the looming water crisis by utilising less water compared to traditional flooded culture. As such, development of genotypes with narrow root cone angle (RCA) is considered a key AP adaptation trait as it could lead to deeper rooting and ensure water uptake at depth. Quantitative trait loci (QTL) and genes associated with rooting angle have been identified in rice, but usually in conventional transplanted systems or in upland and drought conditions. This study aimed to identify QTL associated with RCA in AP systems using a recombinant inbred line population derived from IRAT109.

RESULTS

Four experiments conducted in glasshouse and aerobic field conditions revealed significant genotypic variation existed for RCA in the population. Single and multiple QTL models identified the presence of eight QTL distributed in chromosomes 1, 2, 3, 4, and 11. Combined, these QTL explained 36.7-51.2% of the genotypic variance in RCA present in the population. Two QTL, qRCA1.1 and qRCA1.3, were novel and may be new targets for improvement of RCA. Genotypes with higher number of favourable QTL alleles tended to have narrower RCA. qRCA4 was shown to be a major and stable QTL explaining up to 24.3% of the genotypic variation, and the presence of the target allele resulted in as much as 8.6° narrower RCA. Several genes related to abiotic stress stimulus response were found in the qRCA4 region.

CONCLUSION

Stable and novel genomic regions associated with RCA have been identified. Genotypes which had combinations of these QTL, resulted in a narrower RCA phenotype. Allele mining, gene cloning, and physiological dissection should aid in understanding the molecular function and mechanisms underlying RCA and these QTL. Ultimately, our work provides an opportunity for breeding programs to develop genotypes with narrow RCA and deep roots for improved adaptation in an AP system for sustainable rice production.

Inhibition of Dermatophyte Fungi by Australian Jarrah Honey

Superficial dermatophyte infections, commonly known as tineas, are the most prevalent fungal ailment and are increasing in incidence, leading to an interest in alternative treatments. Many floral honeys possess antimicrobial activity due to high sugar, low pH, and the production of hydrogen peroxide (H2O2) from the activity of the bee-derived enzyme glucose oxidase. Australian jarrah (Eucalyptus marginata) honey produces particularly high levels of H2O2 and has been found to be potently antifungal. This study characterized the activity of jarrah honey on fungal dermatophyte species. Jarrah honey inhibited dermatophytes with minimum inhibitory concentrations (MICs) of 1.5-3.5% (w/v), which increased to ≥25% (w/v) when catalase was added. Microscopic analysis found jarrah honey inhibited the germination of Trichophyton rubrum conidia and scanning electron microscopy of mature T. rubrum hyphae after honey treatment revealed bulging and collapsed regions. When treated hyphae were stained using REDOX fluorophores these did not detect any internal oxidative stress, suggesting jarrah honey acts largely on the hyphal surface. Although H2O2 appears critical for the antifungal activity of jarrah honey and its action on fungal cells, these effects persisted when H2O2 was eliminated and could not be replicated using synthetic honey spiked with H2O2, indicating jarrah honey contains agents that augment antifungal activity.

Initial assessment of protein and amino acid digestive dynamics in protein-rich feedstuffs for broiler chickens

A study evaluating apparent digestibilities of protein and amino acids and their corresponding digestion rates in four small intestinal sites in broiler chickens was completed to further investigate dietary optimisation via synchronised nutrient digestion and absorption. A total of 288 male Ross 308 broiler chickens were offered semi-purified diets with eight protein-rich feedstuffs, including; blood meal (BM), plasma protein meal (PPM), cold pressed (CCM) and expeller-pressed (ECM) canola meal, high (SBM HCP) and low (SBM LCP) crude protein soybean meals, lupins and peas. Diets were iso-caloric, iso-nitrogenous and the test ingredient was the sole source of dietary nitrogen. Each diet was offered to 6 bioassay cages with 6 birds per cage from day 21 to 28 post hatch. On day 28, all birds were euthanized and digesta samples were collected from the proximal jejunum, distal jejunum, proximal ileum and distal ileum to determine apparent protein and amino acids digestibility coefficients, digestion rates and potential digestible protein and amino acids. Dietary protein source significantly influenced energy utilisation, nitrogen retention, apparent protein (N) digestibilities, digestion rates and potential digestible protein along the small intestine. Diets containing BM and SBM LCP exhibited the highest protein digestion rate and potential digestible protein, respectively. Digestibility coefficients and disappearance rates of the majority of amino acids in four sections of the small intestine were influenced by dietary protein source (P < 0.01) and blood meal had the fastest protein digestion rate. In general, jejunal amino acid and protein digestibilities were more variable in comparison to ileal digestibilities, and the differences in protein and amino acid disappearance rates were more pronounced between types of feedstuffs than sources of similar feedstuffs.

Barriers to entering race training before 4 years of age for Thoroughbred horses born in the 2014 Australian foal crop

Currently, there is a paucity of data on the barriers for Australian Thoroughbred horses transitioning from stud farm to racetrack. This paper reports the reasons why horses failed to enter race training and documents their exit destinations. Biographical records of Australian Thoroughbred horses born in 2014 were investigated to determine the number of horses that had not officially entered race training by the start of the 4-year old racing season (1 August 2018). Of the 13,677 foals born in 2014, 66% had commenced training and 51% had raced before the beginning of their 4-year-old season in Australia. A sampling frame based on the post code of the premises where foals were born and records from Racing Australia were used to select a geographically representative sample of the 2014 Australian Thoroughbred foal crop (n = 4,124). From the population eligible for sampling 1,275 horses that had not entered training were enrolled in the survey and their breeders were sent an online questionnaire with follow-up phone calls for those who had not responded. Of the 633 responses (50% of 1275) the most frequent outcomes for horses were: death (38%, n = 239), participation in the racing industry in their 4-year old racing season (24%, n = 154) and retirement (16%, n = 100) either as Australian Stud Book (ASB) bloodstock (n = 17), or as horses rehomed outside the Thoroughbred industry (n = 83). Illness or injury was the most frequent reason for horses not entering race training that were ASB bloodstock, rehomed or deceased. There was a loss of traceability at the point of sale with most horses sold at 1 year of age. This study provides important information on the reasons, alternative outcomes and gaps in traceability for horses not entering training prior to the 4-year-old racing season.

Methods to prevent PCR amplification of DNA from non-viable virus were not successful for infectious laryngotracheitis virus

Molecular-based testing of poultry dust has been used as a fast, sensitive and specific way to monitor viruses in chicken flocks but it provides no information on viral viability. Differentiation of viable and nonviable virus would expand the usefulness of PCR-based detection. This study tested three treatments (1. DNAse, 2. propidium monoazide [PMA], 3. immunomagnetic separation [IMS]) applied to dust or virus stock prior to nucleic acid extraction for their ability to exclude nonviable virus from PCR amplification. Infectious laryngotracheitis virus (ILTV) was used as a model. These treatments assume loss of viral viability due to damage to the capsid or to denaturation of epitope proteins. DNAse and PMA assess the integrity of the capsid to penetration by enzyme or intercalating dye, while IMS assesses the integrity of epitope proteins. Treatments were evaluated for their ability to reduce PCR signal, measured as ILTV log₁₀ genomic copies (ILTV GC), of heat and chemically inactivated ILTV in poultry dust and virus stock. Compared to untreated dust samples, there was an overall reduction of 1.7 ILTV GC after IMS treatment (p<0.01), and a reduction of 2.0 ILTV GC after PMA treatment (p<0.0001). DNAse treatment did not reduce ILTV GC in dust (p = 0.68). Compared to untreated virus stocks, there was an overall reduction of 0.5 ILTV GC after DNAse treatment (p = 0.04), a reduction of 1.8 ILTV GC after IMS treatment (p<0.001) and a reduction of 1.4 ILTV GC after PMA treatment (p<0.0001). None of the treatments completely suppressed the detection of inactivated ILTV GC. In conclusion, treatments that use capsid integrity or protein epitope denaturation as markers to assess ILTV infectivity are unsuitable to accurately estimate proportions of viable virus in poultry dust and virus stocks.

Hygienic behaviour selection via freeze-killed honey bee brood not associated with chalkbrood resistance in eastern Australia

Hygienic behaviour is a social immune response in honey bees shown to help provide resistance to honey bee pests and diseases. A survey of hygienic behaviour and brood diseases was conducted on 649 colonies in eastern Australia to initiate a selective breeding program targeting disease resistance and provide a level of resistance to Varroa (Varroa destructor Anderson and Trueman and V. jacobsoni Oudemans) mites should they become established in Australia. The test population showed a remarkably high baseline level of hygienic behaviour with 17% of colonies meeting or exceeding breeding selection thresholds. Colonies belonging to a breeding program were 5.8 times more likely to be highly hygienic and colonies headed by queens raised from hygienic queen mothers were 2.2 times more likely. Nectar availability (nectar yielding flowering plants within honey bee forage range) influenced hygienic behaviour expression but was not a significant predictor of level of hygienic behaviour. Surprisingly, hygienic behaviour was not a significant predictor of the presence of infection of the honey bee brood disease chalkbrood (Ascosphaera apis) and was not influential in predicting severity of chalkbrood infection in surveyed honey bee colonies. This study, along with reports from commercial beekeepers that chalkbrood infection is on the rise, warrants a deeper exploration of the host-pathogen relationship between Apis mellifera and Ascosphaera apis in Australia.