China
Africa
Explore chapters and articles related to this topic
Parasites and Conservation Biology
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
Examples in which parasites serve as indicators or sentinels of environmental problems or changes also unfortunately occur. Marine mammals ranging from sea otters to harbor seals to killer whales along the Pacific Coast of North America have been found in recent years to be infected with a variety of parasites customarily associated with humans, pets, and farm animals from terrestrial environments. These parasites exemplify what have been called pollutogens. Pollutogens are infectious agents that originate outside a particular ecosystem and are able to develop within a host found in that ecosystem. For instance, co-infections of two related apicomplexans, Toxoplasma gondii and Sarcocystis neurona, have emerged as a major cause of death in southern sea otters, Enhydra lutris nereis. The nematode Capillaria hepatica, normally associated with wild and feral rats (Rattus sp.) in which it is often transmitted by cannibalism, has also appeared in sea otters and implicated in causing mortality. Simultaneous infections with C. hepatica, T. gondii and S. neurona have been found in the otters, pointing out how polyparasitism from these pollutogens could have a devastating combined effect. Other kinds of pathogens associated with terrestrial environments such as Neospora caninum, another apicomplexan normally problematic in both cattle and its canine definitive hosts, have also appeared in marine mammals.
Parasites and Conservation Biology
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2015
Eric S. Loker, Bruce V. Hofkin
Examples in which parasites serve as indicators or sentinels of environmental problems or changes also unfortunately occur. Marine mammals ranging from sea otters to harbor seals to killer whales along the Pacific Coast of North America have been found in recent years to be infected with a variety of parasites customarily associated with humans, pets, and farm animals from terrestrial environments. These parasites exemplify what have been called pollutogens. Pollutogens are infectious agents that originate outside a particular ecosystem and are able to develop within a host found in that ecosystem, yet they do not require that host for reproduction. For instance, co-infections of two related apicomplexans, Toxoplasma gondii and Sarcocystis neurona, have emerged as a major cause of death in southern sea otters, Enhydra lutris nereis. Others kinds of pathogens associated with terrestrial environments such as Neospora caninum, another apicomplexan normally problematic in both cattle and its canine definitive hosts, have also appeared in marine mammals. Several underlying factors combine to create this situation. First, these marine species have had little past exposure to such parasites and so are ill prepared to deal with them. Also, marshlands, which are believed to filter out many parasites, have diminished in extent, allowing parasite-laden freshwater runoff more direct access to the oceans. The ongoing range expansion along the Pacific Coast of the introduced Virginia opossum Didelphis virginianus, the definitive host of S. neurona, has provided a new and ready source of this parasite as well. The number of feral and domestic cats continues to increase, and treatment of cat litter entering sewage systems does not destroy T. gondii oocysts. Wild felids also contribute distinct strains of T. gondii oocysts that find their way into marine waters. Sea otters and other marine mammals have been likened to canaries in a mine, with the parasites they are newly encountering serving as effective indicators of a changing marine ecosystem. In general, changing marine environments (some would say degrading marine environments) pose enormous challenges for the future (see Chapter 10).
Structure-activity relationships of Toxoplasma gondii cytochrome bc 1 inhibitors
Published in Expert Opinion on Drug Discovery, 2022
P. Holland Alday, Aaron Nilsen, J. Stone Doggett
Cytochrome (cyt) bc1 has proven to be a tractable drug target for the majority of veterinary and human apicomplexan pathogens. In addition to T. gondii, cyt bc1 inhibitors have been found to be effective across orders of the phylum Apicomplexa: Haemosporida, Plasmodia spp.; the Piroplasmida, Babesia spp., and Theileria equii; and the Eucoccidiorida, Sarcocystis neurona, Eimeria spp., Neospora caninum, and Besnoitia besnoiti [5–10]. Cryptosporidium, the human gastrointestinal parasite, is a notable exception. It lacks a mitochondrion with genes for enzymes of oxidative phosphorylation, including cyt b and instead contains mitochondrion-related organelles [11]. On the other hand, the human gastrointestinal parasites Cyclospora cayetanensis and Cystoisospora belli encode cyt b in their mitochondrial genomes, although cyt bc1 inhibitors have not been thoroughly evaluated for these diseases.