Relieving barriers and increasing free flowing rivers is a global imperative to restore habitat connectivity for migratory fish stocks. While reducing river fragmentation will certainly improve biodiversity, the spread of non-native species throughout a river system may be facilitated as an inadvertent outcome. Environmental assessment of river systems tabled for barrier alleviation is thus essential to appraise the risk posed by non-native species on a site-by-site basis. Non-native freshwater crayfish are species of concern globally and are implicated as a stressor to native salmonid populations and multiple invertebrates. Here, we demonstrate and compare the use of trapping, remote underwater video (RUV), baited RUV (BRUV) and eDNA to risk assess the implications of removing in-stream barriers and invasive signal crayfish (Pacifastacus leniusculus) throughout the River Calder catchment, United Kingdom. There was no difference between the detection probability of trapping, remote underwater video (RUV) and baited RUV (BRUV) for signal crayfish. No crayfish were detected by eDNA in any of our sites, suggesting a lack of utility in eDNA for rapid and accurate crayfish species occurrence at our sampling level. Distance from barriers played a key role in determining crayfish presence, with populations of crayfish more likely to be found directly downstream from the nearest upstream barrier. Crayfish abundance was higher at locations with lower Oxidation-Reduction Potential (ORP), although it is unclear whether low ORP is caused by the crayfish. There were 53 barriers encapsulated by our survey; over half (50.9%) of these barriers were found to have invasive crayfish both above and below them, and a further 17% had crayfish directly below them. Both tributaries that had reported presence of native white-clawed crayfish (Austropotamobius pallipes) had several barriers between them and the nearest record of signal crayfish; it is recommended that these barriers remain in place and are potentially reinforced, while those that have been identified as breached be the focus of barrier alleviation. In-stream barriers may be creating micro-habitats and relief from strong flow which support crayfish persistence and therefore removal may facilitate flow regimes which are less conducive for non-native crayfish.

Despite increasing awareness of invasive non‐native species (INNS) and enhanced biosecurity controls in many countries, INNS are still arriving and establishing in new destinations, remaining a globally acknowledged threat to native biodiversity. Preventing the introduction of INNS, as opposed to controlling them once they have arrived, is recognised as the most effective approach to their management. Horizon scanning represents one of the key tools to identify high‐risk INNS that have yet to arrive within a region and has been applied in many contexts around the world, but to date there have been no studies that systematically assess the effectiveness of this approach. Here, we revisit the horizon scan for Great Britain conducted in 2013 that assessed the likelihood of high‐risk INNS arriving within the next 10 years, establishing and having an impact on biodiversity and ecosystems. We evaluated the success of this exercise in predicting arrival of these species within the subsequent 10 years. Ninety‐two species were shortlisted in the 2013 horizon scan. In total, 31 of the 92 species identified in the 2013 horizon scan had arrived by 2023. We found that 12 of the top 20 species had arrived within 10 years. In predicting arrival, there was a significant effect of species having arrived previously to Great Britain, and the number of countries in Western Europe and Baltic countries in which an INNS was found prior to 2013. Policy implications : We conclude that horizon scanning provides a rapid, affordable and successful mechanism to predict the arrival of high‐risk INNS. We highlight the importance of citizen science, including biological recording, and of local expertise for detecting and documenting arrival of INNS. We discuss knowledge gaps that could help inform and improve future horizon scanning. In addition, we recommend regularly repeating horizon scanning exercises to support biosecurity and awareness raising for INNS.

Introduction Community engagement with public health efforts often depends on existing knowledge of a health issue.Methods Here, qualitative analysis of archival material from the Jamaica Hookworm Commission (1919-1936) and quantitative analysis of prevalence data are used to assess knowledge of and ecological interactions between different helminths during a historical hookworm eradication campaign.Results Archival sources demonstrate that Jamaicans were familiar with Ascaris lumbricoides. Surveys revealed a high prevalence of hookworm (62% of individuals infected), Ascaris (30%) and Trichuris trichiura (32%) in communities targeted for hookworm control. Community prevalence of Trichuris was positively associated with the prevalence of Ascaris and hookworm. Many individuals were infected with more than one parasite. At an individual level, data from hospital patients and soldiers showed significant associations between all three parasites. The co-occurrence of hookworm and Ascaris, alongside folk treatment of Ascaris with the same plant used by the Hookworm Commission (Chenopodium ambrisoides) to treat hookworm, made biomedical claims about hookworm credible and biomedical treatment more acceptable. Expulsions of Ascaris following treatment also provided dramatic proof of the effectiveness of treatment, further facilitating engagement.Discussion/Conclusion Knowledge of Ascaris and other helminths directly shaped engagement with hookworm treatment, demonstrating how folk medical knowledge, grounded in the biology of the worms, aided a biomedical public health program.

Climate change is likely to affect infectious diseases that are facilitated by biological invasions, with repercussions for wildlife conservation and zoonotic risks. Current invasion management and policy are underprepared for the future risks associated with such invasion-related wildlife diseases. By considering evidence from bioclimatology, invasion biology, and disease research, we illustrate how climate change is anticipated to affect disease agents (parasites and pathogens), hosts, and vectors across the different stages of invasions. We highlight the opportunity to integrate these disciplines to identify the effects of climate change on invasion-related wildlife diseases. In addition, shifting to a proactive stance in implementing management and policy, such as by incorporating climate-change effects either into preventative and mitigation measures for biosecurity or with rapid response protocols to limit disease spread and impacts, could help to combat future ecological, economic, and human health risks stemming from invasion-related wildlife diseases.

The insect mass-rearing industry to produce feed and food is expanding rapidly. Insects in production frequently encounter multiple pathogens and environmental stressors simultaneously, which can lead to significant economic losses. Our understanding of the interactions between different stressors remains limited, and existing methods primarily focus on determining overall patterns of additivity, synergism, or antagonism. However, the interactions between different stressors may exhibit more intricate response patterns, such as time or dose dependency. With the expanding industry of insect production, it becomes vital to conduct comprehensive risk assessment of diseases, using approaches that can detect both lethal and sublethal effects. Here, we assessed the risk of co-exposure to a fungal (Metarhizium brunneum) and a bacterial (Bacillus thuringiensis) pathogen in the yellow mealworm (Tenebrio molitor) at ambient and elevated carbon dioxide (CO2) concentrations. We assessed total larval biomass per treatment group, survival, and individual weight gain 14 and 20 days after pathogen exposure. To analyse the data, we used a mixture toxicity (MIXTox) model, which identifies dose ratio or dose level dependency in addition to overall antagonism or synergism. The interactions between the two pathogens were mostly antagonistic or additive at both CO2 concentrations and time points, indicating that the observed effects during co-exposure did not exceed the expected combined effects of the individual exposure. We did not find evidence that the interactions between the pathogens substantially change at elevated CO2. The antagonistic interactions measured in the bioassays are likely to be indirect via the insect host, as we did not detect direct inhibition between the two pathogens in in vitro experiments. Here we show that using the MIXTox model is a powerful tool to assess the effects of co-exposure to pathogens and quantify risk of disease in mass-reared insects.

Biological invasions are intrinsically linked to introducing associated symbiotic organisms, some of which can be parasitic or pathogenic. The pathogenic risk of an 'invasive parasite' (aka. exotic pathogen) stems from its potential to infect native hosts and induce behavioural change or mortality, with the pathogen potentially presenting a greater risk than the host. Conversely, parasites translocated by invasive hosts may also reduce the impact of their host, indirectly curbing the hosts impact on the invaded ecosystem. In this study, we develop a pathogen profile for the narrow-clawed crayfish, Pontastacus leptodactylus. This is a non-native species in the United Kingdom, and poses a possible risk as a sink for invasive parasites. We use histopathology, metagenomics and metratranscriptomics to outline the symbiotic diversity harboured by a P. leptodactylus population from West Yorkshire, England. We discovered several protozoan and bacterial species that appear to be putatively commensal with this invader, as well as several RNA viruses (Hepelivirales; Picornavirales; Nodaviridae, and others) that may be more pathogenic in nature. Microsporidia and Nudiviridae were absent in our population sample set, as were all metazoan obligate parasites, such as trematodes and acanthocephalans. Using the novel genomic and pathological data available to us, we have explored the evolutionary history of each symbiotic species and provided an initial assessment on the putative risk to native species.

Parasites represent a significant proportion of Earth's biodiversity and play important roles in the ecology and biology of ecosystems and hosts, making them an important target for conservation. Despite increasing calls to prioritize protection for parasites in the academic literature, they remain undervalued and underrepresented in global biodiversity conservation efforts, not least due to the perception that the interests of parasite and host conservation are opposing and the common misconception that parasites are a threat, rather than a benefit, to conservation. We considered whether taking an interdisciplinary approach to parasite conservation research will generate novel insights and solutions concerning why and how parasite conservation should be practiced for the benefit of parasites, their hosts, ecosystems, and people. We argue that 2 of the main barriers to more widespread parasite conservation are the knowledge gap concerning the role of sociocultural factors affecting the willingness to enact parasite conservation and the lack of a consistent and cohesive philosophical basis for parasite conservation. Possible sociocultural barriers to parasite conservation include misconceptions of the risks posed by parasites, taxonomic bias, differences in conservation values, economic constraints, and technical challenges. The use of social science can generate insights into levels of awareness and support for parasite conservation and improve understanding of how human values and attitudes mediate conservation practices concerning parasites. Such knowledge will have a critical role in addressing sociocultural barriers and improving support for parasite conservation. Issues with the current philosophical basis for parasite conservation include contradictory accounts of which parasites merit conservation, insufficient explanation of how different conservation values apply to parasite biodiversity, and the existence of a false antagonism between host and parasite conservation. Greater engagement with philosophical work on environmental ethics and biological unitization will strengthen existing arguments for parasite conservation and will support conservation decision-making processes.

Narrow-clawed crayfish (Pontastacus leptodactylus) are a data deficient invasive non-native species in the UK. Boshaw Whams (West Yorkshire, UK) contains the only known population of narrow-clawed crayfish in Yorkshire. The risk of further spread of these crayfish is high and it is important to establish the extent of the current invasion on the Generalised Invasion Curve to identify potential management options. We used a combination of methods over a 15-month period including trapping, Remote Underwater Video (RUV) and Baited RUV (BRUV) to establish the most efficient method for narrow clawed crayfish monitoring and determine annual population dynamics. There was no significant difference between the three methods in terms of detection efficiency thus we recommend a mixed approach in the future dependent on practitioner capacity. Significantly more males were observed through trapping than females and berried females were detected between February and April. A mark-recapture survey estimated the population to have a minimum size of 10,045 ± 5602 (95% CI) individuals in a waterbody spanning 50,000 m2. Boshaw Whams Reservoir should be considered as in the ‘Containment’ or ‘Asset Protection’ stage of the Generalised Invasion Curve, and action urgently required to prevent further spread.

Raw water transfers between waterbodies are crucial to water utility companies' abilities to balance water supply and demand. However, raw water transfers have been highlighted as a high-risk pathway for the spread of invasive alien species (IAS). Implementing biosecurity at the scale of raw water transfers is a considerable undertaking and the impact on water resources and the environment need to be considered when researching methods to biosecure raw water transfers. We explored the effectiveness of pH changes in causing mortality in aquatic IAS. We used two invasive invertebrate species; Dreissena polymorpha, Dikerogammarus villosus and two invasive plant species; Hydrocotyle ranunculoides, Crassula helmsii. pH was adjusted using chemicals already widely utilised within the water treatment process (ferric sulfate-acid and calcium hydroxide-alkali) to produce treatments of acid (pHs 3, 4, 5, 6) and alkali (pHs 9, 10, 11, 12) pH. For D. villosus, complete mortality was only seen following immersion at pH 12 for >= 1 hour. For D. polymorpha, 100% mortality was not achieved in any treatment. Mortality was highest in more extreme treatments of pH4 (44%) and pH12 (40%) following immersion for 8 hours. Incomplete mortality of H. ranunculoides was seen for all pH treatments, with the highest mortality (50%) at pH4 and pH 10. Crassula helmsii experienced no mortality following immersion in any of the pH treatments. These results indicate that immersion in water with altered pH is unlikely to be suitable as a biosecurity treatment to slow the spread of aquatic invasive invertebrates and macrophytes in raw water transfers.

Studies of extinction typically focus on unintended losses of biodiversity and culture. This study, however, examines an attempt to induce extinction of a parasite: human hookworm (Necator americanus and Ancylostoma duodenale). Our interdisciplinary approach integrates medical history and epidemiology using records created by the Jamaica Hookworm Commission of 1919-1936. We show that the attempt to induce the extinction of hookworms was driven by its perceived effects on labour productivity and consequent status as an ideological and economic threat. We use spatial epidemiology to describe the relationships between parasites, environments and the working conditions of plantation labourers. Using data from 330 locations across Jamaica in which 169,380 individuals were tested for hookworm infection we show that the prevalence of hookworm infection was higher in districts surrounding plantations. Prevalence decreased with the temperature of the coldest month, increased with the amount of rainfall in the driest month, and increased with vegetation quantity (normalised difference vegetation index). Worm burden (and thus pathology) varied greatly between individuals, even those living together; hookworm infection varied between environments, socioeconomic conditions and individuals. Nevertheless, the conditions of labour shaped the distribution of hookworms. Plantations both spread and problematised hookworms, driving efforts to bring it to extinction.

The yellow mealworm (Tenebrio molitor) is a promising insect species for mass-rearing for the production of feed and food. In mass-production systems, insects may be exposed to abiotic stressors such as heat stress as well as potentially lethal pathogens. To ensure mass-reared T. molitor populations are healthy and productive there is a need to understand both the risks, and potential benefits of heat stress, on the fitness of insects and their susceptibility to pathogens. In this study, we investigated the effects of a short (2 h) or a long (14 h) heat stress (38 degrees C) exposure on the susceptibility and the immune responses of T. molitor larvae exposed to a fungal pathogen (Metarhizium brunneum). Larvae were exposed to the pathogen either immediately or five days after the heat stress treatments. The development of heat stressed larvae and their offspring was also assessed. A short heat stress immediately before exposure to M. brunneum increased the survival probability of T. molitor larvae, which correlated with increased antibacterial activity in the hemolymph. The exposure of larvae to short, or long heat stresses five days before pathogen exposure did not affect their survival, despite a temporary lowered body mass gain of heat stressed larvae. However, heat stressed larvae showed decreased hemocyte concentrations when exposed to M. brunneum. We also found an increased body weight in larval offspring of females that had been exposed to a short heat stress as larvae themselves. These findings demonstrate the importance of understanding the effects of heat stress in the long-term. The beneficial effects of heat stress on pathogen susceptibility in T. molitor and the negative effects on body mass gain are only transient, whereas negative effects on immune response (hemocyte concentrations) persist over an extended period.

Numerous insect species and their associated microbial pathogens are exposed to elevated CO2 concentrations in both artificial and natural environments. However, the impacts of elevated CO2 on the fitness of these pathogens and the susceptibility of insects to pathogen infections are not well understood. The yellow mealworm, Tenebrio molitor, is commonly produced for food and feed purposes in mass-rearing systems, which increases risk of pathogen infections. Additionally, entomopathogens are used to control T. molitor, which is also a pest of stored grains. It is therefore important to understand how elevated CO2 may affect both the pathogen directly and impact on host-pathogen interactions. We demonstrate that elevated CO2 concentrations reduced the viability and persistence of the spores of the bacterial pathogen Bacillus thuringiensis. In contrast, conidia of the fungal pathogen Metarhizium brunneum germinated faster under elevated CO2. Pre-exposure of the two pathogens to elevated CO2 prior to host infection did not affect the survival probability of T. molitor larvae. However, larvae reared at elevated CO2 concentrations were less susceptible to both pathogens compared to larvae reared at ambient CO2 concentrations. Our findings indicate that whilst elevated CO2 concentrations may be beneficial in reducing host susceptibility in mass-rearing systems, they may potentially reduce the efficacy of the tested entomopathogens when used as biological control agents of T. molitor larvae. We conclude that CO2 concentrations should be carefully selected and monitored as an additional environmental factor in laboratory experiments investigating insect-pathogen interactions.

Global connectivity is increasing the number of biological invasions. In turn, further anthropogenic stressors including a changing climate are increasing the establishment and impact of invasive alien species (IAS). IAS may provide novel hosts for parasites in the new range. Furthermore, parasites may be co-introduced with their invasive hosts, with opportunities for spillover to new hosts. IAS may themselves be parasites. In this chapter, we explore the effect of global change (climate, pollution, etc.) on biological invasions that are directly associated with invasive, co-invasive or acquired parasitic species (viruses, bacteria, Protozoa, Metazoa, etc.), as well as their role in disease emergence of native parasites. We provide a table of 23 examples from mammalian, avian, reptilian, amphibian, piscine, insect, crustacean, molluscan and plant invasions, which are associated with both global change and parasitism. We demonstrate the impact of climate warming and pollution at each stage of a biological invasion, and ecological and economic consequences for natural and managed populations across terrestrial, marine and freshwater ecosystems.

The mass production of insects is rapidly expanding globally, supporting multiple industrial needs. However, parasite infections in insect mass-production systems can lower productivity and can lead to devastating losses. High rearing densities and artificial environmental conditions in mass-rearing facilities affect the insect hosts as well as their parasites. Environmental conditions such as temperature, gases, light, vibration, and ionizing radiation can affect productivity in insect mass-production facilities by altering insect development and susceptibility to parasites. This review explores the recent literature on environment-host-parasite interactions with a specific focus on mass-reared insect species. Understanding these complex interactions offers opportunities to optimise environmental conditions for the prevention of infectious diseases in mass-reared insects.

Biological invasions can result in the co-introduction of parasitic hitchhikers. These ‘invasive parasites’ include viruses, bacteria, fungi, protists and metazoan symbionts, and they can have diverse effects on the ecological and evolutionary dynamics of their invasive hosts and recipient communities. Some invasive parasites are agents of disease, and the spread of these parasites could ultimately harm biodiversity, global economies and human health. In this introduction, we highlight the significance of researching and understanding parasite invasions, and we include key examples that demonstrate why investigations of parasite invasions should be a critical scientific objective across institutions and management agencies around the globe. The introduction to this book provides an overview of each chapter and their broad aims. The layout of chapters follow the ‘introduction, arrival, establishment and impact’ process of a biological invasion, but the examples in this book specifically draw upon bioinvasions that are understood to have accompanying parasitological implications.

Invasive non-native species and climate change are two of the greatest pressures facing freshwater communities; however, how they interact to impact ecosystem function remains poorly understood despite the potential for impacts on key functional behaviours, such as detritivory, which could have wide-reaching impacts.We quantified the rates of detrital processing and survival of one U.K. native (Gammarus pulex) and two invasive non-native (Dikerogammarus villosus and Dikerogammarus haemobaphes) freshwater amphipod species, across three temperatures (8 degrees C, 14 degrees C, and 20 degrees C), and three leaf diets of varying resource quality (oak, sycamore, and alder) in laboratory microcosms. We also compared amphipod survival across the different temperature and diet treatments.Rates of detrital processing varied between the native and invasive non-native amphipod species, with native G. pulex having a faster processing rate than both invasive non-native species at the lower temperatures. However, as the temperature treatments increased, between-species differences decreased, while the effects of leaf diets became more apparent. Although the survival probability did not vary with amphipod species, amphipod survival was higher at lower temperatures and in treatments containing higher quality leaf diets.We propose that the invasive non-native Dikerogammarus species will affect native communities through lower rates of detrital processing; however, this impact may change under predicted climatic warming and be increasingly similar to native amphipod species.

Anthropogenic stressors such as climate warming and invasive species and natural stressors such as parasites exert pressures that can interact to impact the function of ecosystems. This study investigated how these stressors interact to impact the vital ecosystem process of shredding by keystone species in temperate freshwater ecosystems. We compared metabolic rates and rates of shredding at a range of temperatures up to extreme levels, from 5 °C to 30 °C, between invasive and native amphipods that were unparasitised or parasitised by a common acanthocephalan, Echinorhynchus truttae. Shredding results were compared using the relative impact potential (RIP) metric to investigate how they impacted the scale with a numerical response. Although per capita shredding was higher for the native amphipod at all temperatures, the higher abundance of the invader led to higher relative impact scores; hence, the replacement of the native by the invasive amphipod is predicted to drive an increase in shredding. This could be interpreted as a positive effect on the ecosystem function, leading to a faster accumulation of amphipod biomass and a greater rate of fine particulate organic matter (FPOM) provisioning for the ecosystem. However, the high density of invaders compared with natives may lead to the exhaustion of the resource in sites with relatively low leaf detritus levels.