One toxicology', 'ecosystem health' and 'one health (original) (raw)

Linking Ecology and Epidemiology: The Case of Infected Resource

Cambridge University Press eBooks, 2017

The relationship between parasites and their hosts can have aspects of both trophic and non-trophic interactions. Parasites are in essence consumers of resources, but they are different from typical consumers in several ways. For example, while a typical consumer has more than one victim during its life, parasites as a rule have only one victim per life stage (Lafferty and Kuris, 2002). Also, parasites do not necessarily kill or fully consume their victims. Parasites may also act as prey in a food web, and can be seen as part of trophic interaction in this way as well (Faust, 1975; Marcogliese and Cone, 1997; Johnson et al., 2010; Thieltgets et al., 2013). Inclusion of 47 parasites in an aquatic food web, for example, gave rise to 1093 new interactions of parasites that were prey for other species (Lafferty, 2013). Parasitic interaction can directly or indirectly influence attributes of species in ecological networks, comparable to other non-trophic interactions. The non-trophic interaction that affects attributes of nodes (hosts), and in that way influences the consumer-resource relation, is called "interaction modification" (Kéfi et al., 2012). The attributes could have a direct or indirect influence on the behavior of hosts and non-hosts, handling time of prey, prey preference, assimilation efficiency, conversion efficiency, mortality, reproduction, and growth, and they are common for the different classes of parasites. Parasites are diverse but the magnitude of this diversity is unknown and it is impossible to estimate the number of species (Dobson et al., 2008). The main characteristic is that they use a host individual's energy for growth, reproduction, and survival. They have, however, very different life histories and sizes. We distinguish microparasites (viruses, bacteria, fungi, protozoa), macroparasites (endoparasites such as helminthes), ectoparasites (fleas and ticks), parasitic castrators, and parasitoids (Kuris and Lafferty, 2000; Lafferty and Kuris, 2002). At one end of the size spectrum, viruses vary in length from 30 to 200 nm. For example, rabies virus has a length of 180 nm (Baer, 1991). At the other side of the spectrum, tapeworms, such as Diphyllobothrium, vary from 1 mm to several meters (Faust et al., 1968). Furthermore, the sizes and masses of parasites compared to their hosts are very diverse and depend on the type of parasite. While most microparasites have ratios between 1:10 8 and 1:10 2 , parasitoids and parasitic castrators are sometimes of mass and size comparable to their host (Lafferty and Kuris, 2002). Ectoparasites affect their hosts through energy drain by sucking their blood and by activation of a host's immune response with their saliva. This drain of energy can produce subtle subclinical responses, even when these parasites do not by themselves cause disease in their hosts. However, ticks and fleas can also transmit other parasite species, notably microparasites, initiating infection inside of the host that can lead to strong clinical effects, including substantial morbidity, impairing normal ecological functioning, and mortality. In Ngorongoro Conservation Park in 2000 and 2001 there occurred significant mortality among buffaloes, wildebeests, lions, and rhinoceros that had showed infection with Babesia species transmitted by ticks (Nijhof et al., 2003;

THE NEXUS BETWEEN TOXICOLOGY, ECOSYSTEM HEALTH AND ONE HEALTH

International Journal of Recent Research in Life Sciences , 2024

The "One Health" idea comprises a global strategy emphasizing the need for an approach that is whole and transdisciplinary and integrates multisector expertise in dealing with the health of man, animals, and the environment. It stimulates and promotes the interconnectedness, coexistence, and evolution of living things and their environment, which is itself in a state of constant evolution. Industrialization, geopolitical problems, and an increase in human population have led to increasing global changes causing a lot of damage to biodiversity, extensive deterioration of ecosystems, and considerable migratory movement of both mankind and species in general. Over the years, certain zoonoses, such as bird flu or the Ebola and Zika viral epidemics, have illustrated this fact to the entire world demonstrating the interdependence of human health, animal health, and ecosystem health. Many of the same microbes infect animals and humans, as they share the ecosystems, they live in. Efforts by just one sector cannot prevent or eliminate the problem. One toxicology combines wildlife, human, veterinary, and ecological toxicology to support more logical choices as to what chemicals and what concentrations are permitted to come into contact with human beings and their domestic animals. Ecosystems serve as a life support system to mankind. Humans take great advantage of the resources provided by the planet and by doing so the environment is being modified. The shared environment and food sources of animals and humans allow potential exposure to the same toxic and infectious agents. In this review article, we discuss the connection between toxicology, ecosystem health, and one health.

Evidence for carry-over effects of predator exposure on pathogen transmission potential

Proceedings of the Royal Society B: Biological Sciences, 2015

Accumulating evidence indicates that species interactions such as competition and predation can indirectly alter interactions with other community members, including parasites. For example, presence of predators can induce behavioural defences in the prey, resulting in a change in susceptibility to parasites. Such predator-induced phenotypic changes may be especially pervasive in prey with discrete larval and adult stages, for which exposure to predators during larval development can have strong carry-over effects on adult phenotypes. To the best of our knowledge, no study to date has examined possible carry-over effects of predator exposure on pathogen transmission. We addressed this question using a natural food web consisting of the human malaria parasite Plasmodium falciparum , the mosquito vector Anopheles coluzzii and a backswimmer, an aquatic predator of mosquito larvae. Although predator exposure did not significantly alter mosquito susceptibility to P. falciparum , it incur...

Evaluation of predators as sentinels for emerging infectious diseases

2012

New and emerging diseases in human and animal populations appear to be predominately associated with generalist pathogens that are able to infect multiple hosts. Carnivores are susceptible to a wide range of these pathogens and can act as effective samplers of their vertebrate prey, which are important reservoirs of many emerging diseases. This thesis evaluates the utility of carnivores as sentinels for pathogens present in their prey by exploration of four selected pathogen-prey-sentinel combinations in three rural study sites of varying habitat in northern England and Scotland over a twenty-two month period (2007-2009). Selected pathogens were Coxiella burnetii, Leptospira spp., Encephalitozoon cuniculi, and rabbit haemorrhagic disease virus (RHDV), selected prey species were wild rodents and rabbits, and selected carnivores were foxes, domestic cats and corvids. Seroprevalence to C.burnetii, Leptospira spp and E.cuniculi was assessed using adapted or novel test methodologies to enable their use for multiple mammalian species, however these were not applicable to corvids. RHDV seroprevalence was not assessed due to low acquisition of rabbit samples. Overall, seroprevalence to all three pathogens was significantly higher in predators than prey, at 24.2% and 12.4 % for C.burnetii, 22.73% and 1.95% for Leptospira spp and 39.06% and 5.31% for E.cuniculi in predator and prey species respectively. A similar pattern was found in all study areas and was consistent irrespective of individual prey or predator species, although serological evidence of exposure to E.cuniculi was not detected in domestic cats in any area. A semi-quantitative assessment of the time and financial costs of the study approach and application to hypothetical examples indicates that sampling carnivores is a much more costeffective approach to pathogen detection than sampling prey. The results indicate that carnivores can act as useful sentinels for broad-scale detection of pathogen presence and relative levels of prevalence in prey and predator populations. Careful selection of predator species and methods of sample acquisition are necessary to maximise their utility, and issues associated with diagnostic test performance and validation must also be acknowledged. Suggestions are made as to how this principle might be applied to future surveillance programmes. In addition, the study is the first report on the seroprevalence of C.burnetii, Leptospira spp and E.cuniculi in multiple wildlife species (field voles, bank voles, wood mice, foxes), the first detection of antibodies to C. burnetii in wildlife and cats, the first detection of antibodies to L mini, L hardjo prajitno and L hardjo bovis in wild rodents, and to L mini in cats, and the first detection of antibodies to E.cuniculi in wild rodents and foxes in the UK. Heartfelt thanks to Darren Shaw for all the encouragement, support, supervision and patience, to Sarah Cleaveland for the original inspiration behind this thesis and her continued input and support, and to Jeremy Brown for laboratory support and supervision. Thanks to all the other colleagues who helped me, in particular Alan

Good Medicine for Conservation Biology: the Intersection of Epidemiology and Conservation Theory

Conservation Biology, 2002

Infectious disease can be a concern for several aspects of conservation biology, such as determining threats to species, estimating population viability, and designing reserves, captive breeding, and recovery programs. Several measures are useful for describing infectious diseases in host populations, but it is not straightforward to determine the degree to which a particular disease may affect a host population. The most basic epidemiological theory suggests that populations should be least subject to host-specific infectious disease when they are at low abundance ( paradoxically, the state at which they are in most need of conservation action). There are important exceptions, however, such as when a reservoir host exists or when Allee or stochastic effects occur. Several of the key threats to biodiversity-habitat alteration, introduced species, pollution, resource exploitation, and climate change-can facilitate and/or impair transmission of infectious disease. Common management tools such as population viability analysis rarely address infectious disease explicitly. We suggest that such an inclusion is both possible and warranted. Considerations of infectious disease may influence the way we determine whether a species is in need of protection and how we might design reserves and captive breeding programs. Examples from the literature suggest that (1) introduced pathogens can make abundant species rare and (2) diseases of domestic animals can dramatically affect rare species. For both scenarios, conditions that cause stress or reduce genetic variation may increase susceptibility to disease, whereas crowding and cross-species contact can increase transmission. Southern sea otters ( Enhydra lutris nereis ) make an interesting case study for consideration of the intersection of epidemiology and conservation because disease may be an important factor limiting the growth of otter populations. We conclude that pathogens are of increasing concern for conservation. Because many newly emerging pathogen dynamics often do not conform to the simplifying assumptions used in classic epidemiology, a detailed understanding of pathogen life history will illuminate the intersection of epidemiology and conservation theory.

Wildlife diseases: from individuals to ecosystems

Journal of Animal Ecology, 2011

1. We review our ecological understanding of wildlife infectious diseases from the individual host to the ecosystem scale, highlighting where conceptual thinking lacks verification, discussing difficulties and challenges, and offering potential future research directions. 2. New molecular approaches hold potential to increase our understanding of parasite interactions within hosts. Also, advances in our knowledge of immune systems makes immunological parameters viable measures of parasite exposure, and useful tools for improving our understanding of causal mechanisms. 3. Studies of transmission dynamics have revealed the importance of heterogeneity in host behaviour and physiology, and of contact processes operating at different spatial and temporal scales. An important future challenge is to determine the key transmission mechanisms maintaining the persistence of different types of diseases in the wild. 4. Regulation of host populations is too complex to consider parasite effects in isolation from other factors. One solution is to seek a unified understanding of the conditions under which (and the ecological rules determining when) population scale impacts of parasites can occur. 5. Good evidence now shows that both direct effects of parasites, and trait mediated indirect effects, frequently mediate the success of invasive species and their impacts on recipient communities. A wider exploration of these effects is now needed. 6. At the ecosystem scale, research is needed to characterize the circumstances and conditions under which both fluxes in parasite biomass, and trait mediated effects, are significant in ecosystem processes, and to demonstrate that parasites do indeed increase 'ecosystem health'. 7. There is a general need for more empirical testing of predictions and subsequent development of theory in the classic research cycle. Experimental field studies, meta-analyses, the collection and analysis of long-term data sets, and data constrained modelling, will all be key to advancing our understanding. 8. Finally, we are only now beginning to understand the importance of cross-scale interactions associated with parasitism. Such interactions may offer key insights into bigger picture questions such as when and how different regulatory factors are important, when disease can cause species extinctions, and what characteristics are indicative of functionally resilient ecosystems.