A blowfly strike vaccine requires an understanding of host-pathogen interactions

The current status and outlook for insecticide, acaricide and anthelmintic resistances across the Australian ruminant livestock industries: assessing the threat these resistances pose to the livestock sector

The Australian ruminant livestock industries are faced with the need to control parasitic infectious diseases that can seriously impact the health of animals. However, increasing levels of resistance to insecticides, anthelmintics and acaricides are substantially reducing the ability to control some of these parasites. Here we review the current situation with regard to chemical resistances in parasites across the various sectors of the Australian ruminant livestock industries and assess the level of threat that these resistances pose to the sustainability of these sectors in the short to long terms. We also look at the extent to which testing for resistance occurs across the various industry sectors, and hence how well-informed these sectors are of the extent of chemical resistance. We examine on-farm management practices, breeding of parasite-resistant animals, and non-chemical therapeutics that may act as short to long term means to reduce the current reliance on chemicals for parasite control. Finally, we look at the balance between the prevalence and magnitude of current resistances and the availability and adoption rates of management, breeding and therapeutic alternatives in order to assess the parasite control outlook for the various industry sectors.

Traumatic sheep myiasis: A review of the current understanding

Myiasis, or the infestation of live humans and vertebrate animals by dipterous larvae, is a health issue worldwide. The economic impact and potential threat to animal health and wellbeing of this disease under the animal husbandry sector is considerable. Sheep are a highly vulnerable livestock category exposed to myiasis (sheep strike), due to several unique predisposing factors that attract flies. The successful mitigation of this disease relies on a thorough understanding of fly population dynamics associated with the change in weather patterns and the evaluation of this disease through different branches of science such as chemistry, molecular biology, and microbiology. The present review provides a summary of the existing knowledge of strike in sheep, discussed in relation to the application of volatile organic compounds, metagenomics, and molecular biology, and their use regarding implementing fly control strategies such as traps, and to increase the resilience of sheep to this disease through improving their health and wellbeing.

Control of sheep flystrike: what's been tried in the past and where to from here

Flystrike remains a serious financial and animal welfare issue for the sheep industry in Australia despite many years of research into control methods. The present paper provides an extensive review of past research on flystrike, and highlights areas that hold promise for providing long-term control options. We describe areas where the application of modern scientific advances may provide increased impetus to some novel, as well as some previously explored, control methods. We provide recommendations for research activities: insecticide resistance management, novel delivery methods for therapeutics, improved breeding indices for flystrike-related traits, mechanism of nematode-induced scouring in mature animals. We also identify areas where advances can be made in flystrike control through the greater adoption of well-recognised existing management approaches: optimal insecticide-use patterns, increased use of flystrike-related Australian Sheep Breeding Values, and management practices to prevent scouring in young sheep. We indicate that breeding efforts should be primarily focussed on the adoption and improvement of currently available breeding tools and towards the future integration of genomic selection methods. We describe factors that will impact on the ongoing availability of insecticides for flystrike control and on the feasibility of vaccination. We also describe areas where the blowfly genome may be useful in providing impetus to some flystrike control strategies, such as area-wide approaches that seek to directly suppress or eradicate sheep blowfly populations. However, we also highlight the fact that commercial and feasibility considerations will act to temper the potential for the genome to act as the basis for providing some control options.

Pain Management in Farm Animals: Focus on Cattle, Sheep and Pigs

Pain causes behavioral, autonomic, and neuroendocrine changes and is a common cause of animal welfare compromise in farm animals. Current societal and ethical concerns demand better agricultural practices and improved welfare for food animals. These guidelines focus on cattle, sheep, and pigs, and present the implications of pain in terms of animal welfare and ethical perspectives, and its challenges and misconceptions. We provide an overview of pain management including assessment and treatment applied to the most common husbandry procedures, and recommendations to improve animal welfare in these species. A cost-benefit analysis of pain mitigation is discussed for food animals as well as the use of pain scoring systems for pain assessment in these species. Several recommendations are provided related to husbandry practices that could mitigate pain and improve farm animal welfare. This includes pain assessment as one of the indicators of animal welfare, the use of artificial intelligence for automated methods and research, and the need for better/appropriate legislation, regulations, and recommendations for pain relief during routine and husbandry procedures.

Metazoan Parasite Vaccines: Present Status and Future Prospects

Eukaryotic parasites and pathogens continue to cause some of the most detrimental and difficult to treat diseases (or disease states) in both humans and animals, while also continuously expanding into non-endemic countries. Combined with the ever growing number of reports on drug-resistance and the lack of effective treatment programs for many metazoan diseases, the impact that these organisms will have on quality of life remain a global challenge. Vaccination as an effective prophylactic treatment has been demonstrated for well over 200 years for bacterial and viral diseases. From the earliest variolation procedures to the cutting edge technologies employed today, many protective preparations have been successfully developed for use in both medical and veterinary applications. In spite of the successes of these applications in the discovery of subunit vaccines against prokaryotic pathogens, not many targets have been successfully developed into vaccines directed against metazoan parasites. With the current increase in -omics technologies and metadata for eukaryotic parasites, target discovery for vaccine development can be expedited. However, a good understanding of the host/vector/pathogen interface is needed to understand the underlying biological, biochemical and immunological components that will confer a protective response in the host animal. Therefore, systems biology is rapidly coming of age in the pursuit of effective parasite vaccines. Despite the difficulties, a number of approaches have been developed and applied to parasitic helminths and arthropods. This review will focus on key aspects of vaccine development that require attention in the battle against these metazoan parasites, as well as successes in the field of vaccine development for helminthiases and ectoparasites. Lastly, we propose future direction of applying successes in pursuit of next generation vaccines.

The Battle Against Flystrike - Past Research and New Prospects Through Genomics

Flystrike, or cutaneous myiasis, is caused by blow fly larvae of the genus Lucilia. This disease is a major problem in countries with large sheep populations. In Australia, Lucilia cuprina (Wiedemann, 1830) is the principal fly involved in flystrike. While much research has been conducted on L. cuprina, including physical, chemical, immunological, genetic and biological investigations, the molecular biology of this fly is still poorly understood. The recent sequencing, assembly and annotation of the draft genome and analyses of selected transcriptomes of L. cuprina have given a first global glimpse of its molecular biology and insights into host-fly interactions, insecticide resistance genes and intervention targets. The present article introduces L. cuprina, flystrike and associated issues, details past control efforts and research foci, reviews salient aspects of the L. cuprina genome project and discusses how the new genomic and transcriptomic resources for this fly might accelerate fundamental molecular research of L. cuprina towards developing new methods for the treatment and control of flystrike.

Traumatic Myiasis: A Neglected Disease in a Changing World

Traumatic myiasis, the parasitic infestation by fly larvae in traumatic lesions of the tissues of living vertebrates, is a serious medical condition in humans and a welfare and economic issue in domestic animals. New molecular studies are providing insights into its evolution and epidemiology. Nevertheless, its incidence in humans is generally underreported, particularly in tropical and subtropical regions. Myiasis in domestic animals has been studied more extensively, but continuous management is difficult and expensive. A key concern is the inadvertent introduction and global spread of agents of myiasis into nonendemic areas, facilitated by climate change and global transport. The incursion of the New World screwworm fly (Cochliomyia hominivorax) into Libya is the most notable of many such range shifts and demonstrates the potential risks of these parasites and the costs of removing them once established in a geographic area. Nevertheless, the insect agents of myiasis can be of societal benefit to forensic science and in medicine as an aid to wound treatment (larval therapy).

Lucilia cuprina genome unlocks parasitic fly biology to underpin future interventions

Lucilia cuprina is a parasitic fly of major economic importance worldwide. Larvae of this fly invade their animal host, feed on tissues and excretions and progressively cause severe skin disease (myiasis). Here we report the sequence and annotation of the 458-megabase draft genome of Lucilia cuprina. Analyses of this genome and the 14,544 predicted protein-encoding genes provide unique insights into the fly's molecular biology, interactions with the host animal and insecticide resistance. These insights have broad implications for designing new methods for the prevention and control of myiasis.

The immunobiology of myiasis infections--whatever happened to vaccination?

The current state of myiasis vaccine technologies are reviewed mainly in the primary research genera of Lucilia and Hypoderma. The importance of myiasis flies as primary causes of morbidity and mortality in agricultural species and man has not diminished despite the existence of good control strategies. However, the development of vaccines against myiasis infections has been relatively quiescent for more than 10 years despite the rapid development of genomic and proteomic analysis and of skills in data interpretation. The value of vaccine research in an era of chemical primacy is analysed. In fact, recent findings of drug resistance and the impact of animal welfare concerns should mean a renewed interest in alternative controls. The reasons that this has not been true to date are explored and new possibilities discussed.

Hidden antigens from third instar Hypoderma lineatum: impact of immunization on larval survival in artificial infestations

Soluble fractions of Hypoderma lineatum third instar fat body, haemocytes and haemolymph were formulated with Quil A and used to immunize four groups of calves while a fifth group remained untreated. Calves received two subcutaneous injections of the soluble fractions, or adjuvant only delivered two weeks apart. Two weeks after the last injection the calves were exposed to 50 newly hatched larvae of H. lineatum which were placed on the skin and allowed to penetrate. Survival of larval stages was monitored by weekly palpation and collection of emergent third instars. Antibody responses to the immunogens were evaluated by immunoblots and following infestation antibody responses to first instar antigens were evaluated by an ELISA. Non-immunized calves and calves injected with adjuvant were all palpation positive for cattle grubs. In groups immunized with fat body, haemocyte and haemolymph components 100%, 33% and 33% were palpation positive for grubs respectively. First instar mortality, as reflected in palpable grubs, was high in the groups receiving injections with tissue components (99.3%, 95.1%, 95.8%, 83.9 and 80.4% mortality for those groups receiving fat body, haemocyte, haemolymph, adjuvant or control respectively). Second and third instar mortality was also higher in the immunized groups (100.0%, 91.7%, 91.7% for fat body, haemocyte, and haemolymph respectively) in comparison to the adjuvant only (14.0%) and unvaccinated (33.3%) groups. No viable flies emerged from pupae originating from larvae emergent from any of the immunized groups. Calves receiving the tissue extracts developed antibodies to several protein components following the second immunization which were still present 13 weeks post-infestation. Several proteins appeared to be common among the three tissue extracts and were recognized by antibodies from the immunized calves. All groups of calves became positive for antibodies to first instar antigens, although in some immunized calves the antibodies were transient.

A Lucilia cuprina excretory-secretory protein inhibits the early phase of lymphocyte activation and subsequent proliferation

The development of a protective immune response in sheep towards the presence of the larval stage of Lucilia cuprina has not been reported in the field. Upon investigation of the effects of larval excretory/secretory material on ovine T lymphocyte proliferation, we isolated a 56 kDa protein capable of inhibiting lymphocyte proliferation by at least 70%, compared with that in the presence of mitogen alone. This protein inhibited proliferation induced through cross-linking of the T-cell receptor as well as proliferation induced pharmacologically through the stimulation of the protein kinase C (PKC) pathway. The protein, named blowfly larval immunosuppressive protein (BLIP), was shown to bind directly to lymphocytes. Further investigation revealed that the BLIP prevented a proportion of lymphocytes from entering the first division following stimulation, by affecting the early events in lymphocyte activation. Subsequently, the BLIP reduced CD25 expression on T lymphocytes, reduced IL-2 mRNA expression, in addition to IFN-gamma, IL-4, IL-10 and IL-13 mRNA expression. Conversely, TNF-alpha and TGF-beta gene expression was up-regulated in response to the BLIP. These effects suggest suboptimal activation of T lymphocytes in the presence of the BLIP, and we propose that the BLIP presents an effective immune evasion tactic for the larvae of L. cuprina.

A review of mulesing and other methods to control flystrike (cutaneous myiasis) in sheep

Flystrike (cutaneous myiasis) in sheep has the potential to have a major impact on the welfare of significant numbers of sheep worldwide, but particularly in Australia. The main control method used in Australia, the mulesing operation to remove folds of skin from the hindquarters of the sheep, is effective in controlling the disease, but will be terminated from 2010 as a result of concerns that the operation itself has too great a negative impact on sheep welfare. Alternative treatment methods are considered, and it is proposed that they need to be appraised for each farm separately, based on the conditions prevailing and the potential to apply the different treatments. Sheep are predisposed to flystrike if their fleece is wet or contaminated with faeces or urine. Monitoring and awareness of the weather conditions will enable farmers to strategically treat their sheep with insecticides, or to observe them and treat affected animals more regularly. Frequent removal of wool by crutching, dagging and shearing will aid wool desiccation after rainfall and decrease the likelihood of fleece contamination with excreta. Some control of diarrhoea can be achieved by good grazing management and treatment of diseases that predispose sheep to the disorder. Reducing fly populations can be achieved by the use of traps, and parasitoid wasps also offer some promise. Alternative methods of removing wool and wrinkles from the hindquarters of sheep, including the topical application of quarternary ammonium compounds, phenols, caustic soda or plastic clips, have yet to be proven to be effective, without severely impacting on the welfare of the animal as well as compromising operator safety. In the long term, the breeding of sheep without wrinkles or wool on their hindquarters offers the most likely method of control, although a small proportion of sheep are affected on other parts of their body.

Specific IgG antibody responses in Oestrus ovis L. (Diptera: Oestridae) infected sheep: associations with intensity of infection and larval development

Larvae of Oestrus ovis (Diptera: Oestridae) are ubiquitous parasites of nasal and sinusal cavities of sheep and goats. According to the chronobiology of O. ovis infections in Sardinia and the seasonal pattern of the IgG response, the optimal period to investigate the relationships between O. ovis larval populations and intensity of local and systemic IgG antibody responses was mid-July in the summer season. Sarda x Lacaune ewes (n=186), divided into three ram-families were used in the study. Systemic and local IgG responses were measured by ELISA tests using second stage larval crude extracts (L2CE) and L2 (L2SGC) and L3 (L3SGC) salivary gland contents as coating antigens. The number of larval instars, larval length of L1, L2 and L3 larvae, and larval weight of L2 and L3 larvae were individually recorded after ewe necropsy. Negative correlations among larval establishment and/or larval development on the one hand and intensity of local or systemic IgG responses on the other hand were found in two out of three studied ram-families.