Nematodes as biocontrol agents Grewal, P. S; Ehlers, R. U; Shapiro-Ilan, D. I
Nematodes as biocontrol agents,
2005
eBook
This book documents and illustrates major developments in the use of nematodes for the biological control of insects and slugs. It covers the use of three main types of nematodes: entomopathogenic ...nematodes, entomophilic nematodes and slug-parasitic nematodes. The biology, commercial production, formulation and quality control, application technology, strategy and safety of each of these three nematode groups is discussed. The book also examines the application of nematodes in different cropping systems, and the efficacy of nematodes against specific pests. The potential of predatory nematodes to control plant-parasitic nematodes and mycophagous nematodes to control fungal pathogens is also reviewed.
This book outlines the economic importance of specific plant parasitic nematode problems on the major food and industrial crops and presents the state-of-the-art management strategies that have been ...developed to reduce specific nematode impacts and outlines their limitations. Case studies to illustrate nematode impact in the field are presented and future changes in nematode disease pressure that might develop as a result of climate change and new cropping systems are discussed.
Root-knot nematodes (Meloidogyne spp.) are the most important plant-parasitic nematodes worldwide, with most temperate and tropical crops suffering yield losses from one or more species ...of Meloidogyne. Root-knot nematodes are the most widely recognized plant-parasitic nematodes because the characteristic galls or knots they cause on plant roots are easily observed symptoms for diagnosis. Meloidogyne graminis is damaging to many turf and forage grasses. Due to the prevalence of this nematode on grasses, and the prevalence of grasses compared to other crops in the state, it is likely the most widespread species of root-knot nematode in Florida. It is of increasing concern due to the rising importance of turfgrasses in the Florida economy, the susceptibility of grasses to this nematode, and implementation of new diagnostic techniques that have brought to light the damaging potential of this nematode.
This document is also available on the Featured Creatures website at http://entomology.ifas.ufl.edu/creatures.
https://edis.ifas.ufl.edu/in1231
Over the past 10–15 years, we have witnessed a rapid increase in both the prevalence and magnitude of anthelmintic resistance, and this increase appears to be a worldwide phenomenon. Reports of ...anthelmintic resistance to multiple drugs in individual parasite species, and in multiple parasite species across virtually all livestock hosts, are increasingly common. In addition, since the introduction of ivermectin in 1981, no novel anthelmintic classes were developed and introduced for use in livestock until recently with the launch of monepantel in New Zealand. Thus, livestock producers are often left with few options for effective treatment against many important parasite species. While new anthelmintic classes with novel mechanisms of action could potentially solve this problem, new drugs are extremely expensive to develop, and can be expected to be more expensive than older drugs. Thus, it seems clear that the “Global Worming” approach that has taken hold over the past 40–50 years must change, and livestock producers must develop a new vision for parasite control and sustainability of production. Furthermore, parasitologists must improve methods for study design and data analysis that are used for diagnosing anthelmintic resistance, especially for the fecal egg count reduction test (FECRT). Currently, standards for diagnosis of anthelmintic resistance using FECRT exist only for sheep. Lack of standards in horses and cattle and arbitrarily defined cutoffs for defining resistance, combined with inadequate analysis of the data, mean that errors in assigning resistance status are common. Similarly, the lack of standards makes it difficult to compare data among different studies. This problem needs to be addressed, because as new drugs are introduced now and in the future, the lack of alternative treatments will make early and accurate diagnosis of anthelmintic resistance increasingly important.
Helminth infections are ubiquitous in grazing ruminant production systems, and are responsible for significant costs and production losses. Anthelmintic Resistance (AR) in parasites is now widespread ...throughout Europe, although there are still gaps in our knowledge in some regions and countries. AR is a major threat to the sustainability of modern ruminant livestock production, resulting in reduced productivity, compromised animal health and welfare, and increased greenhouse gas emissions through increased parasitism and farm inputs. A better understanding of the extent of AR in Europe is needed to develop and advocate more sustainable parasite control approaches. A database of European published and unpublished AR research on gastrointestinal nematodes (GIN) and liver fluke (Fasciola hepatica) was collated by members of the European COST Action "COMBAR" (Combatting Anthelmintic Resistance in Ruminants), and combined with data from a previous systematic review of AR in GIN. A total of 197 publications on AR in GIN were available for analysis, representing 535 studies in 22 countries and spanning the period 1980-2020. Reports of AR were present throughout the European continent and some reports indicated high within-country prevalence. Heuristic sample size-weighted estimates of European AR prevalence over the whole study period, stratified by anthelmintic class, varied between 0 and 48%. Estimated regional (country) prevalence was highly heterogeneous, ranging between 0% and 100% depending on livestock sector and anthelmintic class, and generally increased with increasing research effort in a country. In the few countries with adequate longitudinal data, there was a tendency towards increasing AR over time for all anthelmintic classes in GIN: aggregated results in sheep and goats since 2010 reveal an average prevalence of resistance to benzimidazoles (BZ) of 86%, macrocyclic lactones except moxidectin (ML) 52%, levamisole (LEV) 48%, and moxidectin (MOX) 21%. All major GIN genera survived treatment in various studies. In cattle, prevalence of AR varied between anthelmintic classes from 0-100% (BZ and ML), 0-17% (LEV) and 0-73% (MOX), and both Cooperia and Ostertagia survived treatment. Suspected AR in F. hepatica was reported in 21 studies spanning 6 countries. For GIN and particularly F. hepatica, there was a bias towards preferential sampling of individual farms with suspected AR, and research effort was biased towards Western Europe and particularly the United Kingdom. Ongoing capture of future results in the live database, efforts to avoid bias in farm recruitment, more accurate tests for AR, and stronger appreciation of the importance of AR among the agricultural industry and policy makers, will support more sophisticated analyses of factors contributing to AR and effective strategies to slow its spread.
Various interacting factors have been identified to explain why health plans for nematode parasite control, based on conventional epidemiological knowledge and involving pharmaceutical treatments of ...their sheep hosts have become unsustainable. Of these, the emergence of anthelmintic resistance has had a major impact on the economics of sheep farming, necessitating fundamental managemental changes. This review focusses on the use of anthelmintic drugs for the control of gastrointestinal nematode infections in sheep, emphasising the need to develop sustainable strategies in the face of inevitable parasite evolution in response to exposure to anthelmintic drugs and other noxious stimuli, or favourable opportunities resulting from changing animal management and climatic factors.
Most hosts are infected with multiple parasites, and responses of the immune system to co‐occurring parasites may influence disease spread. Helminth infection can bias the host immune response toward ...a T‐helper type 2 (Th2) over a type 1 (Th1) response, impairing the host’s ability to control concurrent intracellular microparasite infections and potentially modifying disease dynamics. In humans, immune‐mediated interactions between helminths and microparasites can alter host susceptibility to diseases such as HIV, tuberculosis (TB), and malaria. However, the extent to which similar processes operate in natural animal populations and influence disease spread remains unknown. We used cross‐sectional, experimental, and genetic studies to show that gastrointestinal nematode infection alters immunity to intracellular microparasites in free‐ranging African buffalo (Syncerus caffer). Buffalo that were more resistant to nematode infection had weaker Th1 responses, there was significant genotypic variation in nematode resistance, and anthelminthic treatment enhanced Th1 immunity. Using a disease dynamic model parameterized with empirical data, we found that nematode‐induced immune suppression can facilitate the invasion of bovine TB in buffalo. In the absence of nematodes, TB failed to invade the system, illustrating the critical role nematodes may play in disease establishment. Our results suggest that helminths, by influencing the likelihood of microparasite invasion, may influence patterns of disease emergence in the wild.
Nematodes are one of the most important pests globally and can cause up to 14% loss of food crops. In total, nematodes cause over USD 100 billion in global crop damage annually. To date, only a few ...thousand PPN species have been described. Nematode identification has traditionally relied on morphological and anatomical characters using light microscopy and, in some cases, scanning electron microscopy (SCN). Lately, integrative studies combining molecular diagnosis with morphology and taxonomy have been used to accurately identify and describe nematode species. Detailed analyses of morphological and molecular data have both significantly contributed to our overall understanding of the dynamic and complex nature of plant–nematode interactions. This book includes eleven chapters that cover different aspects of nematology research, from classical morphology and taxonomy to DNA analysis and phylogeny. It also includes very useful information on the rapid detection of plant-parasitic nematodes.
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