Publications by authors named "Walkden-Brown S"

Clinical signs of respiratory disease are common in Lao goats. To identify the causative agents involved in this clinical syndrome, a matched case-control study was conducted across 70 smallholder goat holdings in Savannakhet province. Fifty paired nasal swab samples were collected from goats with respiratory signs (cases) and unaffected (control) goats from 27 goat holdings.

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Pinkeye is a highly contagious disease of goats with different aetiologies. Surveys in Lao PDR have identified eye lesions typical of pinkeye as a common condition, however, this has not been confirmed diagnostically, and the responsible pathogens have not been identified. A matched case-control study was implemented in 70 goat holdings from Savannakhet province, Lao PDR, to detect agents causing pinkeye and conduct phylogenetic analysis of the identified pathogens.

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Maintaining genetic diversity and variation in livestock populations is critical for natural and artificial selection promoting genetic improvement while avoiding problems due to inbreeding. In Laos, there are concerns that there has been a decline in genetic diversity and a rise in inbreeding among native goats in their village-based smallholder system. In this study, we investigated the genetic diversity of Lao native goats in Phin, Songkhone and Sepon districts in Central Laos for the first time using Illumina's Goat SNP50 BeadChip.

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Oriental theileriosis, a disease primarily impacting cattle is caused by an apicomplexan hemoprotozoan parasite, . It has now become established in the Australasia region. The organism was long considered a benign cause of persistent infections; however, an increase in clinical outbreaks since 2006 in the eastern Australian states and New Zealand was associated with the identification of the pathogenic Ikeda (Type 2) and Chitose (Type 1) genotypes.

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Mass vaccination against infectious laryngotracheitis virus (ILTV) in drinking water can result in variable initial vaccine take. Partial initial vaccine coverage of 20% with an Australian ILT vaccine (A20) previously resulted in significant protection against virulent ILTV challenge. This follow-up study used the international Serva ILT vaccine strain in a factorial design testing four levels of vaccination coverage (0%, 10%, 20%, or 100% of chicks eye-drop vaccinated with the live vaccine at 7 days of age) and three levels of ILTV challenge (no challenge or challenge at 7 or 21 days postvaccination [DPV]).

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Helminth infections have been re-emerging with the growing popularity of free-range and floor-based chicken production systems. The aim of this study was to determine the prevalence and worm burdens of intestinal helminth infection in cage-free laying chickens in Australia. In an online survey about worm prevalence, a high proportion of respondents reported the detection of Ascaridia galli (77%), followed by tapeworms (69%) and caecal worms (Heterakis gallinarum) (62%), whereas fewer respondents (23%) reported the presence of hair worms (Capillaria spp.

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A moderate to high seroprevalence of exposure to Newcastle disease (NDV), avian metapneumovirus (aMPV), infectious laryngotracheitis virus (ILTV), infectious bronchitis virus (IBV) and Mycoplasma gallisepticum (MG) has recently been reported in Ethiopia, but it is unclear to what extent these contribute to clinical cases of respiratory disease. This study investigated the presence of these pathogens in chickens exhibiting respiratory disease in two live markets in Addis Ababa. Markets were visited weekly for three months, and 18 chickens displaying respiratory clinical signs were acquired.

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Population-level sampling based on qPCR detection of infectious laryngotracheitis virus (ILTV) in poultry dust can be used to assess ILT vaccination outcomes following mass administration in drinking water. We report on the field application of this approach to assess the success of vaccine administration and its use in ILT outbreak control in meat chickens. In Study 1, dust samples were collected from 26 meat chicken flocks at 0, 4, 7, 14, and 21 days post drinking water vaccination (DPV) given between 7 to 13 days of age with the Serva or A20 live attenuated ILT vaccines.

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Ascaridia galli infection models use eggs isolated from chicken excreta, worm uteri and worms cultured in artificial media. The aim of this study was to compare the infectivity of A. galli eggs isolated from these sources under two infection regimens.

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In Ethiopia, most chicken disease outbreaks and mortalities are attributed to a respiratory syndrome known as "fengil" with variable clinical signs and undefined etiology. The main goal of this study was to determine whether key respiratory pathogens that could contribute to the fengil syndrome circulate in Ethiopia. Specifically, we aimed to determine the seroprevalence of infectious laryngotracheitis virus (ILTV), infectious bronchitis virus (IBV), Newcastle disease virus (NDV), Mycoplasma gallisepticum (Mg), and avian metapneumovirus (aMPV).

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Eggs in the infective stage of the chicken nematode Ascaridia galli are often required for in vivo and in vitro studies on this parasite. The reliability of any artificial A. galli infection depends on the viability and embryonation capacity of A.

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Blowfly strike or cutaneous myiasis, caused principally by the Australian sheep blowfly Lucilia cuprina is endemic to Australian sheep producing areas and is a major cause of suffering and economic loss. This article reports incidence and control practices as determined by three cross-sectional surveys of Australian sheep farmers covering the years 2003 (n = 1365), 2011 (n = 575) and 2018 (n = 354) with more questions relating to blowfly strike in the latter two surveys. Breech strike was reported at a higher rate than body strike in all survey years.

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To investigate methods for in vitro assessment of anthelmintic efficacy against the chicken nematode Ascaridia galli this study firstly evaluated sample preparation methods including recovery of eggs from excreta using different flotation fluids and induced larval hatching by the deshelling-centrifugation method and the glass-bead method with or without bile. It then evaluated two in vitro assays, the in-ovo larval development assay (LDA) and larval migration inhibition assay (LMIA), for anthelmintic efficacy testing against A. galli using fresh eggs and artificially hatched larvae, respectively.

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This study investigated worm control practices by free-range egg farmers and the efficacy of the commercial anthelmintics levamisole (LEV), piperazine (PIP), flubendazole (FLBZ) and fenbendazole (FBZ) against gastrointestinal nematodes on two free-range layer farms in Australia. An online survey comprising 36 questions was designed and implemented using SurveyMonkey. The survey contained questions about participant demographics, farm and flock characteristics, perceived intestinal worm importance, infection monitoring, deworming and other worm control practices.

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Currently, there is no available vaccine against hemorrhagic enteritis virus (HEV) in Australia. Although it is assumed that subclinical HEV infections occur and may be associated with an increase in colibacillosis in Australian commercial turkey flocks, the prevalence of infection with this virus in the country is largely unknown. The aims of this study were to determine the extent of HEV infection in commercial flocks in Australia and to investigate the diversity of Australian HEV strains.

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The sheep body louse (Bovicola ovis) is a parasite of major economic concern in Australia. This article reports lice incidence and control practices on Australian sheep farms as determined by three cross-sectional surveys of the years 2003, 2011 and 2018. The incidence of live lice detected within a flock was similar across the survey years with a slight decline in 2018 (2003: 20%, 2011: 18.

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Despite the high cost of vaccination programmes, conventional methods to evaluate vaccine uptake are often impractical and costly. More recently, molecular-based testing of poultry dust has been used to monitor the "take" of Marek's disease virus and infectious laryngotracheitis virus (ILTV) live vaccines. This study aimed to provide proof-of-concept for detecting other poultry pathogens by using molecular detection of vaccine microorganisms in poultry dust of vaccinated flocks.

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This study was conducted to investigate whether co-administration of Barbervax® (Bvax) with Haemonchus contortus surface larval antigen (HcsL3) would increase the protective efficacy and duration of protection against H. contortus infection in weaner Merino sheep. A total of 132 10-month-old weaned Merino ewe lambs were randomly allocated into six treatment groups (n = 22).

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The efficacy of commercially available anthelmintics against mature and immature stages (including ovicidal effects) of two Australian field isolates of Ascaridia galli was evaluated in two separate experiments. The anthelmintics tested were levamisole (LEV), piperazine (PIP) and flubendazole (FBZ) plus LEV-PIP. A total of 192 artificially trickle-infected young cockerels (96 birds per isolate) were randomized into sixteen experimental groups of 12 cockerels each (7 treatments and 1 untreated control per isolate).

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With the continued growth of free-range egg production, the importance of the chicken roundworm Ascaridia galli is increasing. Investigations into this parasite would be facilitated by the availability of characterised strains and clear guidelines on optimal methods of multiplication and maintenance. Currently, there is lack of well-defined in vivo models for maintaining A.

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Infectious laryngotracheitis virus (ILTV) DNA has been detected in blood fractions, but the cell phenotype with which the virus is associated is unknown. This study investigated the presence of ILTV antigen in peripheral blood cells of six acutely ILTV-infected chickens (5 or 9 days post ocular inoculation with a virulent isolate) and three sham-inoculated chickens using immunofluorescent staining. Blood fractions were separated by Ficoll-Paque density gradient centrifugation, and smears were prepared from erythrocyte and leukocyte fractions.

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Cross-sectional surveys of sheep parasite control practices in Australia were conducted in 2004, 2012 and 2019 to document parasite problems, control practices and measure change over time. This article reports the results pertaining to gastrointestinal nematode infection; comparisons between years are mostly descriptive and not based on statistical inference. There was a general increase in the use of grazing management to prepare clean pastures for sheep to control gastrointestinal nematode infections with the largest increases in the use of: cropping, long acting anthelmintics to prepare clean pastures, feeding strategies, selecting rams for resistance to nematodes, and leaving some sheep untreated.

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Excreta egg counting techniques are used for indirectly estimating the magnitude of gastrointestinal nematode infection in live animals. The aim of this study was to optimise laboratory and field sampling methods for routine monitoring of nematode infections in chickens by evaluating the sensitivity, accuracy, and precision of the Modified McMaster (MM) and Mini-FLOTAC (MF) methods using laying chicken excreta samples spiked with estimated true numbers of eggs (Experiment 1 = 5-1500 EPG (eggs/g); Experiment 2 = 5-500 EPG) without and with operator effects, respectively or using individual fresh excreta (n = 230) and fresh floor excreta (n = 42) from naturally infected free-range layer farms. The Coefficient of Variation (CV) was assessed within and between operators and the time spent on sample preparation and counting was also evaluated.

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Background: A major focus of research on the gut microbiota of poultry has been to define signatures of a healthy gut and identify microbiota components that correlate with feed conversion. However, there is a high variation in individual gut microbiota profiles and their association with performance. Population level samples such as dust and pooled excreta could be useful to investigate bacterial signatures associated with productivity at the flock-level.

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Local animal health services in rural communities in Cambodia are mainly provided by village animal health workers (VAHWs), although the participation and contribution of VAHWs to livestock disease prevention are uncertain. The participation of the VAHWs as identified by their 'dropout rate' was examined in a desktop review in December 2020 of the national data on VAHWs recorded between 2011 and 2020. The contribution and involvement of VAHWs in disease prevention programmes were examined in a survey conducted between February and March 2014, then analyzed in the context of other surveys of VAHW knowledge, attitudes and practices.

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