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PubMed1995

Concentrations of total serum IgE, IgA, and IgG in atopic and parasitized dogs.

Concentrations of total serum IgE, IgA, and IgG were measured in 36 atopic and 16 parasitized dogs, and compared them with 30 healthy control dogs. IgE was measured using enzyme-linked immunosorbent assay. IgA and IgG were measured using radial immunodiffusion assays. Mean total serum immunoglobulin (Ig) E concentrations in healthy, atopic and parasitized dogs were 7.1 units (U) ml-1, 5.8 U ml-1 and 14.3 U ml-1, respectively. Mean total serum IgA concentrations in the same groups were 103.3 mg dl-1, 63.2 mg dl-1 and 67.3 mg dl-1, respectively. Mean total serum IgG concentrations were 1066 mg dl-1, 1621 mg dl-1 and 1480 mg dl-1 in the three groups. There was no significant difference in IgE concentrations between these groups of dogs. IgA levels were significantly lower in atopic and parasitized dogs compared with healthy dogs (P < or = 0.05), whereas IgG levels were significantly higher in the atopic and parasitized dogs (P < or = 0.005). These results suggest that measurement of total serum IgE would be of no benefit in the preliminary clinical investigation of a suspected atopic dog. The lower IgA and higher IgG concentrations in both atopic and parasitized dogs suggest that similar regulatory mechanisms governing immunoglobulin synthesis occur in canine allergic and parasitic disease, promoting IgG synthesis but down-regulating IgA production.

Animals↗

PubMed1994

Swine immunity to selected parasites.

Swine parasitism exerts a significant economic impact worldwide. In the United States, the greatest losses are due directly or indirectly to the costs of zoonotic parasitisms. Three of the six most common foodborne parasitic diseases of humans in the United States are associated with pork consumption. These include toxoplasmosis, taeniasis or cysticercosis (caused by the pork tapeworm Taenia solium), and trichinellosis. Toxoplasmosis is of particular concern because of the fulminating disease that occurs in immunocompromised people. Generalizations and extrapolations of information derived from rodent and human studies, to swine parasitisms, are complicated by immunological differences between the hosts, and by the diverse biological characteristics of internal and external parasites studied. Swine studies thus far reported have demonstrated that protective immunity to helminth infection involves both cellular and humoral mechanisms, with antibodies and antibody-mediated responses playing important roles in preventing establishment of newly acquired larvae. Protection against protozoan parasites is primarily by cell-mediated strategies, whereas protective immunity to arthropod infestation is primarily through humoral mechanisms, principally those associated with type 1 hypersensitivity.

Animals↗

PubMed1982

Immunodeficiency models in characterization of immune responses to parasites--an overview.

The use of selected immunosuppressant agents and genetically immunodeficient animals in studies designed to characterize the immune response to parasitic infections is reviewed. Immunosuppression induced by commonly used chemicals (corticosteroids and alkylating agents) and ionizing radiation is examined briefly. A greater emphasis is placed on congenitally immunodeficient animals and on immunosuppression induced by purified antisera directed against a variety of cellular specificities. The use of such immunodeficient animals has aided our understanding of the complex interrelationship between host and parasite. However, chemical immunosuppressants and the levels of irradiation used in adoptive cell transfer studies are usually indiscriminant in their toxic effects on a variety of tissues other than those targeted. These affected tissues may be crucial in establishment of the delicate physiological balance required for maintenance of equilibrium between host and parasite. Thus the effects of cytotoxic drugs or irradiation on parasite burdens may reflect alteration of not only immunity, but other essential factors leading to misinterpretation of results. Use of congenitally immunodeficient animals, which are readily repaired by introduction of specific cellular components, may be more useful in dissecting host responses to parasites. In addition, depletion of specific components of the immune system through use of anti-isotype antiserum, for example, is another useful probe. These approaches do not suffer from the generalized cytotoxic effects of chemicals and irradiation, and remove a potentially important and misleading variable from experimental designs. They also allow one to discriminate between non-specific inflammatory and specific immunological factors. The potential pitfalls of broadly used induced immunodeficiency states in studies on parasitisms may now be overcome at least partially by use of highly purified and specific cytotoxic reagents coupled with an ever-increasing array of genetically immunodeficient animal models.

Adrenal Cortex Hormones↗

PubMed1993

Economic benefits of parasite control in cattle.

The economic losses often associated with parasitism in cattle are universally accepted. The degree of economic significance related to these losses, the burdens of parasites required to cause such losses, and the specific control measures needed to avoid these losses are, however, topics of serious debate and outright disagreement among parasitologists and veterinarians. This is because most cattle have parasite burdens that are truly subclinical, with no obvious signs of parasitism but significant losses in potential production. These losses are often very insidious in nature and often difficult to prove statistically in a consistent manner. This discussion focuses on the need to: (1) define the benefits related to parasite control in cattle; (2) develop clear and effective parasite control recommendations that will allow the producer to realize these benefits; (3) effectively transfer this information to the cattleman.

Animal Feed↗

PubMed2003

A general test of the interactive-isolationist continuum in gastrointestinal parasite communities of fish.

Parasite communities are generally believed to lie somewhere along the interactive-to-isolationist continuum, i.e. from rich assemblages of species with high colonisation rates in which interspecific interactions play an important structuring role, to species-poor assemblages where interactions are unlikely. This framework has become one of the paradigms of parasite community ecology. There is, however, no objective way of ranking a set of parasite communities in terms of the extent of interactivity among their constituent species. Here, we propose a simple index of interactivity based on the general likelihood of species co-occurrence, and thus on the potential for interactions, and we apply it to component communities of gastrointestinal helminth parasites from 37 species of marine fish hosts. The index essentially collapses several features of parasite communities thought to influence the degree of interactivity into a single number independent of the number of hosts examined or the total number of species in a component community. The range of values obtained here suggests that the potential interactivity in helminth communities of fish covers almost the full spectrum of possibilities, i.e. from isolationist to highly interactive communities. Although derived from presence/absence data only, the index correlates relatively strongly with the total parasite abundance per host, as well as the total prevalence of infection and the mean infracommunity richness. In other words, it captures properties of the community that influence interactivity. The use of the index in comparative studies may help in determining whether interactive helminth communities are, as widely believed, more common in endothermic vertebrate hosts than in fish hosts.

Animals↗

PubMed2005

Spatial and temporal predictability of the parasite community structure of a benthic marine fish along its distributional range.

The search for consistent patterns of organisation in parasite communities remains a central theme in parasite community ecology. However, to date, much evidence comes from studies without replication in both space and time; when replicate communities are examined, repeatable patterns are rarely observed. Here we determine, using nested subset analyses, whether the infracommunities of ectoparasites and endoparasites of a benthic marine fish (Sebastes capensis) show non-random structure. Then we examine the spatial repeatability of parasite community structure across the host's distribution in the southern Pacific, and the temporal repeatability of ectoparasite community structure from one locality. In total, 537 fish were captured from different latitudes (between 11 degrees S and 52 degrees S) along the Pacific coast of South America; a further 122 specimens were captured in two other years from one of the sampling localities, Valdivia (40 degrees S). In spite of variation in fish sizes among samples, fish size generally did not correlate with either ecto- or endoparasite species richness. The ecto- and endoparasite species richness of the component communities were also not correlated with fish sample size across the nine localities. Significant nested patterns were found in the ectoparasite communities of S. capensis at all eight localities, except at latitude 52 degrees S. Significant nested patterns were also found in the endoparasite infracommunities of S. capensis at seven of the nine localities, the exceptions being those from latitudes 11 degrees S and 20 degrees S. On a temporal scale, significant nestedness was observed in the ectoparasite infracommunities of S. capensis during each of the 3 years of sampling at Valdivia. In general, the same parasite species are responsible for the repeatability of nested patterns, though their importance varies among localities. The spatial and temporal predictability of the parasite community structure in S. capensis may be associated with the fish's benthic habitat and territorial behavior, suggesting that host biology may be a key determinant of the structure of parasite communities.

Animals↗

PubMed2006

Parastrongyloides trichosuri, a nematode parasite of mammals that is uniquely suited to genetic analysis.

Commonly studied nematode parasites have not proven amenable to simple genetic analyses and this has significantly reduced the available research options. We introduce here a nematode parasite of mammals, Parastrongyloides trichosuri, which has features uniquely suited for genetic analysis. This parasite has the capacity to undergo multiple reproductive cycles as a free-living worm and thereby amplify the numbers of its infective L3s in faeces. Culture conditions are presented that permit facile laboratory maintenance of this worm for >90 free-living life cycles (to date) without the need for re-entry into a permissive host. Even after long maintenance as a free-living worm, culture conditions can be manipulated to favour development of infective L3 worms, which remain able to successfully infect their marsupial hosts. The switch to infective L3 development is triggered by a secreted factor contained in culture medium conditioned by multiple generations of free-living worm culture. It is simple to perform single pair crosses with P. trichosuri to carry out Mendelian genetics in the laboratory and this has been done multiple times with sibling pairs to generate highly inbred lines. Lines of worms can readily be cryopreserved and recovered. Over 7000 expressed sequence tags have been produced from cDNAs at different life cycle stages and used to identify single nucleotide polymorphisms and microsatellites as genetic markers. Free-living worms live only a few days on average while the patency of parasitic infections can last for several months. Since we show this is not the result of re-infection, we conclude that parasitic worms have a lifespan capacity at least 20-30 times longer than their free-living counterparts. We discuss how it should be possible to exploit these unique features of P. trichosuri as a model for future studies that explore the genetic basis of longevity and parasitism.

Animals↗

PubMed2005

Parasite regulation by host hormones: an old mechanism of host exploitation?

Recent experimental evidence suggests that parasites can not only evade immune responses actively but also exploit the hormonal microenvironment within the host to favor their establishment, growth and reproduction. The benefit for parasites of hormonal exploitation is so great that they have evolved structures similar to the steroid and protein hormone receptors expressed in upper vertebrates that can bind to the hormonal metabolites synthesized by the host. This strategy is exemplified by two parasites that respond to adrenal steroids and sexual steroids, respectively: Schistosoma mansoni and Taenia crassiceps. Understanding how the host endocrine system can, under certain circumstances, favor the establishment of a parasite, and characterizing the parasite hormone receptors that are involved might aid the design of hormonal analogs and drugs that affect the parasite exclusively.

Animals↗

PubMed2006

Parasites: proxies for host genealogy and ecology?

Genetic information is used extensively to reconstruct the evolutionary and demographic history of organisms. Recently, it has been suggested that genetic information from some parasites can complement genetic data from their hosts. This approach relies upon the hypothesis that such parasites share a common history with their host. In some cases, parasites provide an additional source of information because parasite data can better reconstruct the common history. Here, we discuss which parasite traits are important in determining their usefulness for analysing host history. The key is the matching of the traits of the parasite (e.g. effective population size, generation time, mutation rate and level of host specificity) with the timescales (phylogenetic, phylogeographic and demographic) that are relevant to the issues of concern in host history.

Animals↗

PubMed2003

Gastrointestinal parasites of domestic cats in Perth, Western Australia.

A study was conducted to determine the prevalence of gastrointestinal parasites in a sample of domestic cats in Perth and the knowledge of their owners about the control and potential for zoonotic transmission of these parasites. Faecal samples (418), collected from cats originating from five sources, were examined by microscopy and questionnaires administered to cat owners. Forty randomly selected samples were also screened using PCR in order to detect cysts of Giardia and oocysts of Cryptosporidium that may have been present in a faecal sample at very low levels. The overall prevalence of gastrointestinal parasites in domestic cats by microscopy was 8.6%. Pet shop kittens had the highest parasite prevalence (34.3%), followed by cats and kittens from breeding establishments (15.8%), refuge cats and kittens (8.3%), privately owned cats (2.3%), and boarding cats and kittens (1.6%). Surprisingly, 80% of the 40 cats tested by PCR were positive for Giardia duodenalis and 10% for Cryptosporidium. None of these cats were positive on microscopy. After adjusting for other factors with multiple logistic regression, kittens less than 6 months of age, and cats living in households with more than one cat or with a dog were significantly more likely to be parasitised. In the logistic regression model, the presence of parasitism was also significantly influenced by the number of anthelmintic doses administered in the 12 month period prior to the study. The majority (64.5%) of cat owners were aware that feline parasites could be transmitted to humans, however less than half (42.8%) were aware of the modes of transmission to humans.

Age Factors↗

PubMed2003

Presence and persistence of intestinal parasites in canine fecal material collected from the environment in the Province of Chubut, Argentine Patagonia.

We investigated the presence of intestinal parasites in canine feces collected from public squares in Comodoro Rivadavia, Chubut, Argentina (45 degrees S, 68 degrees W) and determined the persistence of Echinococcus granulosus eggs in those droppings under natural environmental conditions in that region. In the first experiment, we analyzed 163 fecal samples collected from urban squares during 8 months time and found parasitic elements in 46.6%. The presence of parasites was independent of the condition of the feces (fresh or dried; P>0.05). Parasites potentially pathogenic in man were present, such as Toxocara species (spp.), Taenia spp./Echinococcus spp., Uncinarias spp., and Entamoeba spp. In the second experiment, we analyzed two canine fecal samples contaminated with E. granulosus eggs, deposited for 41 months within the natural environment. These parasitic elements persisted during the entire study as attested by light microscopy and the ELISA coproantigen test. We propose the study of the presence of intestinal parasites in canine feces within the environment as a general strategy for identifying and monitoring areas of risk for canine-related zoonoses since we were able to demonstrate the persistence of E. granulosus eggs in deposited canine feces for over 3 years within the area studied.

Animals↗

PubMed2004

Prevalence of intestinal parasites in dogs under veterinary care in Maracaibo, Venezuela.

The prevalence of intestinal parasites in dogs presented to the Veterinary Policlinic of the University of Zulia (PVU) was measured between January and December 2001. A total of 614 fecal samples were evaluated by the fecal flotation method. One or more species of parasites was identified in 218 (35.5%) dogs. The parasites most frequently detected were: Ancylostoma spp. (24.5%), Toxocara canis (11.4%) and Isospora spp. (8.1%). Single parasitic infections were present in 149 (24.3%) dogs. The age distribution of intestinal parasites in dogs less than 1 year old had a higher overall prevalence than those dogs over 12 months of age. There was no significant difference in the prevalence between male (38.9%) and female (31.7%) dogs. There was a significantly (P < 0.05) greater prevalence of parasites in mixed-breed dogs (40.3%) as compared with pure-breed dogs (30.8%). A significant difference (P < 0.05) was detected between the general prevalence of January and December compared to August.

Age Factors↗

PubMed2004

Olfactory-mediated parasite recognition and avoidance: linking genes to behavior.

A major cost of social behavior is the increased risk of exposure to parasites and infection. Animals utilize social information, including chemical signals, to recognize and avoid conspecifics infected with either endoparasites or ectoparasites. Here, we briefly discuss the relations among odors, parasite recognition, and avoidance, and consider some of the associated hormonal, neural, and genomic mechanisms. In rodents, odor cues mediate sexual and competitive interactions and are of major importance in individual recognition and mate detection and choice. Female mice distinguish between infected and uninfected males by urinary odors, displaying aversive response to, and avoidance of, the odors of infected individuals. This reduces both the likelihood of the transmission of parasites to themselves and allows females to select for parasite-free males. This set of olfactory and mate choice responses can be further modulated by social factors such as previous experience and exposure to infected males and the mate choices of other females. Male mice, who also face the threat of infection, similarly distinguish and avoid parasitized individuals by odor, thus reducing their likelihood of infection. This recognition and avoidance of the odors of infected individuals involves genes for the neuropeptide, oxytocin (OT), and estrogenic mechanisms. Mice with deletions of the oxytocin gene [OT knockout mice (OTKO)] and mice whose genes for estrogen receptor (ER)-alpha or ER-beta have been disrupted [ER knockout mice (ERKO), alpha-ERKO and beta-ERKO] are specifically impaired in their recognition of, aversion to, and memory of the odors of infected individuals. These findings reveal some of the genes involved in the mediation of social recognition in the ecologically relevant context of parasite recognition and avoidance.

Animals↗

PubMed2001

Adaptive physiological processes in the host during gastrointestinal parasitism.

Parasite infection of the gastrointestinal tract with helminths or protozoa induces detrimental effects on host tissues and host physiology, which have been extensively studied and reviewed. However, parasitism of the digestive system is also associated with adaptive, compensatory phenomena based on changes in host physiology or structures and which tend to counterbalance the negative consequences. The objective of this review is to describe these adaptive processes and their possible underlying mechanisms. Different processes which tend to attenuate the effect of either the loss of appetite, the intestinal malabsorption or the increased tissue losses have been assessed. These processes have been reported both for helminth and protozoan infections, where they present similar characteristics. The mechanisms involved in the adaptation to parasitism remain largely unidentified. The role of feedback mechanisms based on host regulation, possibly through gastrointestinal hormones, has been raised. On the other hand, some data support the proposal that parasites themselves may initiate some of the adaptive processes and consequently favour their own survival. These adaptive phenomena appear to be an essential component in the dynamic balance between host and parasites. Also, parasite infections represent unique models to study the adaptation of the gastrointestinal tract to aggressors.

Adaptation, Physiological↗

PubMed2002

Cysteine proteases of parasitic organisms.

Cysteine proteases play numerous indispensable roles in the biology of parasitic organisms. Aside from previously known general catabolic functions and protein processing, cysteine proteases may be key to parasite immunoevasion, excystment/encystment, exsheathing and cell and tissue invasion. Parasite cysteine proteases are unusually immunogenic and have been exploited as serodiagnostic markers and vaccine targets. Although host homologues exist, parasite cysteine proteases have distinct structural and biochemical properties including, pH optima and stability, the alteration in peptide loops or domain extensions, diverse substrate specificity and cellular location. The disparate nature of parasite cysteine protease compared to the host orthologous proteins has opened opportunities for chemotherapy. This review will highlight recent research on the 'papain-like' class of cysteine proteases, the most abundant family, and the newly discovered class of asparaginyl-endopeptidases. Cysteine protease classification will be re-examined in light of the diversity uncovered within parasitic organisms.

Amino Acid Sequence↗

PubMed1999

Parasites and low temperatures.

Low temperatures affect the rate of growth, development and metabolism of parasites and when temperatures fall below 0 degrees C may expose the parasite to the potentially lethal risk of freezing. Some parasites have mechanisms, such as diapause, which synchronise their life cycle with favourable seasons and the availability of hosts. Parasites of endothermic hosts are protected from low temperatures by the thermoregulatory abilities of their host. Free-living and off-host stages, however, may be exposed to subzero temperatures and both freezing-tolerant and freeze-avoiding strategies of cold hardiness are found. Parasites of ectothermic hosts may be exposed to subzero temperatures within their hosts. They can rely on the cold tolerance adaptations of their host or they may develop their own mechanisms. Exposure to low temperatures may occur within the carcass of the host and this may be of epidemiological significance if the parasite can be transmitted via the consumption of the carcass.

Adaptation, Physiological↗

PubMed1987

Pathophysiology of parasitic infections.

Parasites can have a wide range of pathophysiological effects on the host. This review describes those associated with some parasites of major importance in man and animals. Haemoprotozoan diseases such as trypanosomiasis and malaria are primarily associated with anaemia. Such anaemias have a complex aetiology involving various mechanisms responsible for red cell destruction as well as possible defects in red cell production. In addition to these haematological effects these diseases are associated with marked disturbances in heart function and the nervous, immune and urinary systems. The other major groups of parasitic diseases are those associated with the gastrointestinal tract. The most advanced studies have been conducted on the pathophysiology of gastrointestinal nematode parasites of sheep and have revealed significant effects on feed intake, gastrointestinal function, and protein and energy metabolism. Similar studies have yet to be conducted in other hosts and parasitic diseases. There is also a need to examine in greater detail the factors which can modulate pathophysiological responses by the host to parasitic infections.

Anemia↗

PubMed2002

Revealing the faunal tapestry: co-evolution and historical biogeography of hosts and parasites in marine systems.

Parasites are integral components of marine ecosystems, a general observation accepted by parasitologists, but often considered of trifling significance to the broader community of zoologists. Parasites, however, represent elegant tools to explore the origins, distribution and maintenance of biodiversity. Among these diverse assemblages, host and geographic ranges described by various helminths are structured and historically constrained by genealogical and ecological associations that can be revealed and evaluated using phylogenetic methodologies within the context of frameworks and hypotheses for co-evolution and historical biogeography. Despite over 200 years of sporadic investigations of helminth systematics, knowledge of parasite faunal diversity in chondrichthyan and osteichthyan fishes, seabirds and marine mammals remains to be distilled into a coherent and comprehensive picture that can be assessed using phylogenetic approaches. Phylogenetic studies among complex host-parasite assemblages that encompass varying temporal and geographic scales are the critical context for elucidating biodiversity and faunal structure, and for identifying historical and contemporary determinants of ecological organization and biogeographic patterns across the marine biosphere. Insights from phylogenetic inference indicate (1) the great age of marine parasite faunas; (2) a significant role for colonization in diversification across a taxonomic continuum at deep and relatively recent temporal scales; and (3) a primary role for allopatric speciation. Integration of ecological and phylogenetic knowledge from the study of parasites is synergistic, contributing substantial insights into the history and maintenance of marine systems.

Animals↗