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At least 19 recordsLinked to original sources
PubMed2003

[Detection of parasites and symptoms of parasitic diseases. 2: Parasites of the gastrointestinal tract, tissue and organ parasites, ecto- and skin parasites].

Intestinal parasites are Giardia lamblia, Cryptosporidium parvum, Entamoeba histolytica, hookworms, ascaris, tape worms and others. As to organ parasites, their life-threatening courses are pointed out: amebiasis in the intestine, liver, lung and brain, toxoplasmosis in the brain, lung and heart muscle, including the danger for the child of a pregnant woman with an acute infection, West African sleeping sickness with encephalitis, the East African form with polyserositis, South American Chagas' disease with intestinal and myocardial involvement, visceral leishmaniasis Kala Azar, the filariasis Onchocerca volvulus with threatening blindness, the dog tapeworm with cysts and Echinococcus multilocularis with carcinoma-like infiltration of the liver and other organs, cysticercosis of the brain, eye and muscle tissue; partly generalizing parasitoses in immuno-suppressed including AIDS patients, finally skin parasites as causes of disease (e.g. scabies), and as potential carriers of pathogens.

Diagnosis, Differential↗
PubMed2002

Paternity-parasitism trade-offs: a model and test of host-parasite cooperation in an avian conspecific brood parasite.

Efforts to evaluate the evolutionary and ecological dynamics of conspecific brood parasitism in birds and other animals have focused on the fitness costs of parasitism to hosts and fitness benefits to parasites. However, it has been speculated recently that, in species with biparental care, host males might cooperate with parasitic females by allowing access to the host nest in exchange for copulations. We develop a cost-benefit model to explore the conditions under which such host-parasite cooperation might occur. When the brood parasite does not have a nest of her own, the only benefit to the host male is siring some of the parasitic eggs (quasi-parasitism). Cooperation with the parasite is favored when the ratio of host male paternity of his own eggs relative to his paternity of parasitic eggs exceeds the cost of parasitism. When the brood parasite has a nest of her own, a host male can gain additional, potentially more important benefits by siring the high-value, low-cost eggs laid by the parasite in her own nest. Under these conditions, host males should be even more likely to accept parasitic eggs in return for copulations with the parasitic female. We tested these predictions for American coots (Fulica americana), a species with a high frequency of conspecific brood parasitism. Multilocus DNA profiling indicated that host males did not sire any of the parasitic eggs laid in host nests, nor did they sire eggs laid by the parasite in her own nest. We used field estimates of the model parameters from a four-year study of coots to predict the minimum levels of paternity required for the costs of parasitism to be offset by the benefits of mating with brood parasites. Observed levels of paternity were significantly lower than those predicted under a variety of assumptions, and we reject the hypothesis that host males cooperated with parasitic females. Our model clarifies the specific costs and benefits that influence host-parasite cooperation and, more generally, yields precise predictions about expected levels of host male paternity. These predictions will enable a more rigorous assessment of field studies designed to test adaptive hypotheses of host-parasite cooperation.

Animals↗
PubMed1999

Mathematical modelling for intra-specific brood-parasitism: coexistence between parasite and non-parasite.

In this paper, we consider an aspect of the intra-specific brood-parasitism with a mathematical modelling. As in case of moorhen Gallinula chloropus, the case dealt with in this paper in such that just a part of the whole population has the parasitising behaviour against the individuals belonging to another part of non-parasite subpopulation that does not have such behaviour. Analysing the expected fitness gain from the brood-parasitism, we consider the condition in order that parasite individuals coexist with non-parasite ones within a population. From the mathematical modelling analysis, it is shown that the stable equilibrium frequency of parasite individuals within a population, if exists, depends on the difference among individuals in terms of the individual quality reflected to the survival probability of bred offsprings.

Animals↗
PubMed2000

Life cycle and parasitic interaction of the lizard-parasitizing mite Ophionyssus galloticolus (Acari: Gamasida: Macronyssidae), with remarks about the evolutionary consequences of parasitism in mites.

Wild-caught specimens of the lacertid lizard Gallotia galloti eisentrauti from the Canary Island of Tenerife were checked for ectoparasites. The parasitic gamasid mite Ophionyssus galloticolus Fain and Bannert (2000) was very abundant on these lizards. Additionally, parasitism by larvae of two species of Trombiculidae (Prostigmata: Parasitengona) was observed. O. galloticolus was reared in the laboratory on its natural host in order to investigate its life cycle, reproductive biology, and development. The life history of O. galloticolus is documented in detail and compared to literature data of other Ophionyssus species. O. galloticolus was found to be similar to other species of the same genus with respect to the duration of development, the precopulatory association of protonymphs, and the arrhenotokous development of eggs. However, it seems to be more tolerant towards low relative humidity and longer starvation periods than other Ophionyssus species. Evolutionary transformations of the life-history pattern of this genus and other parasitic mites in comparison to its predatory precursors involve a reduction or partial suppression of ontogenetic instars in order to decrease mortality during host-seeking phases, and a compensating increase in growth capacity of the remaining feeding instars facilitated by replacement of sclerites through elastic cuticle or by growth of new cuticle unrelated to a moult (neosomy).

Animals↗
PubMedDate not supplied

Batflies parasitic on some phyllostomid bats in southeastern Brazil: parasitism rates and host-parasite relationships.

Ectoparasitic batflies were studied on 12 species of phyllostomid bats, by making 35 nightly collections of bats using mist nets at the "Panga" Ecological Reservation near Uberlândia, State of Minas Gerais, southeastern Brazil, from August 1989 to July 1990. Eleven species of Streblidae and one of Nycteribiidae were collected on 12 species of bats. Prevalence of ectoparasitic flies was lower than those reported by other authors for the New World and may be the result of the lack of caves in the study area, causing bats to roost in less favorable locations, forming smaller colonies. The fly, Trichobius joblingi Wenzel, was found on Carollia perspicillata (Linnaeus), showing preference for adult male bats. This could be explained by the predominance of males in the bat colonies, and by the fact that females rest in isolation during the reproductive period making them less exposed to the parasites. The streblid flies, Aspidoptera falcata Wenzel and Megistopoda proxima (Séguy), were found on Sturnira lilium (Geoffroy). A. falcata occurred mainly on young and adult females, whereas M. proxima did not show any preferences relative to the reproductive condition of the host. Ecological factors are important in determining differential numbers of parasites occurring on the different sexes, ages and reproductive state of the hosts.

Age Factors↗
PubMed1981

[The relationship between host and parasite in the Crustacean Carcinus parasitized by Sacculina carcini: effect of crude extracts of Sacculina and haemolymph of parasitized Crab upon the proteinogramm of experimented healthy crabs (author's transl)].

The injection of crude extracts of Sacculina to healthy crabs induces, after a variable lapse of time, qualitative and quantitative changes in their proteinogramm and a delay in their moulting cycle. These changes are the same as those observed in infested specimens. The injection of haemolymph from parasitized crabs gives similar effects. So, the Sacculina could be able to produce effect from afar upon organs not invaded by the roots of the parasite.

Animals↗
PubMed2002

The ecology of fish parasites with particular reference to helminth parasites and their salmonid fish hosts in Welsh rivers: a review of some of the central questions.

Ecological studies carried out in Welsh rivers on the feeding behaviour of salmonid fish, their helminth parasites and intermediate hosts in the early 1950s and in 1998 have been used as a basis to review the literature dealing with the following questions. First, how are the helminth populations dispersed in space-time? Second, to what extent are the distributional patterns and the life history strategies of the parasites influenced by physicochemical factors? Third, to what extent are populations of helmith parasites in salmonid fish influenced by host characteristics including the genome, sex, age, size, social position and Feeding behaviour? Fourth, are the populations of parasites regulated in a density-dependent manner? Fifth, do the parasites influence the survival and wellbeing of their salmonid hosts and the evolution of sex? Sixth, to what extent is the parasite community influenced by environmental changes including those of an anthropogenic nature and can the parasites be used as bioindicators of pollution? As with most parasites the helminth species found were highly overdispersed thus making it necessary to undertake a log10 (1 + x) conversion for statistical analyses. Statistical analyses confirm that the genome, age and sex of salmonid fish hosts, the station and seasonal change in radiation levels were significant factors in predicting the number of parasites. The evidence given supports the hypothesis that the feeding behaviour and habitat selection by the host fish, their position in the social hierarchy and the overdispersed nature of the transmission sites are the key factors in causing differences in the parasitic fauna related to host species, age, size and sex. Differences in the helminth parasite community related to station can be explained on the basis of differences in water types, sediments and chemistry. Although the evidence presented is in accord with the consensus view that temperature is correlated with seasonal changes in the abundance of many species of helminth parasites, it is argued that it may not be the direct causative mechanism. It is postulated that the life history strategy that results in a decline in abundance of the more vulnerable adult parasites in the gut of the salmonid hosts during the summer has arisen as a result of evolutionary pressures. At this time, the gut environment is particularly inhospitable because of the temperature-related enhancement of the host's immune mechanism and the increased gut turnover rate. In contrast, the larval stages in the immunologically and metabolically more benign intermediate host would be under less intensive selective pressures. It is postulated therefore that evolutionary pressures have caused the parasites to leave the definitive host and concentrate their reproductive efforts in the intermediate hosts during the warmer months. Evidence is given in support of the hypothesis that the parasite populations are regulated in a density-dependent manner and that the regulatory mechanisms may involve the host's immune mechanisms and intraspecies competition and interspecies competition of an exploitative or interference nature. Quantitative studies using 'K' factor analysis and biochemical research to elucidate the nature of the interference mechanisms are required to test this hypothesis. The absence of age-related resistance indicates an old and stable relationship in which the immunosuppressive and immunoavoidance mechanisms of the parasites and hosts, respectively, are in balance. This indicates that the introduction of novel parasites or new genetic strains of host fish could result in harmful epidemics. Despite causing tissue damage, there was no evidence of parasite-induced mortality among the salmonids in the Teifi. This finding is in accord with the generally accepted view that most freshwaters are not troubled by parasite problems. although parasites are present in abundance. In fact, parasite abundance in the salmonid fish in the Teifi was positively correlated with the condition factor and the adipose index. Two testable hypotheses were advanced to explain these observations. First, the more dominant well-conditioned fish in the hierarchy are more likely to acquire parasites because they ingest more food items and spend more time in sheltered habitats with depositing sediments where transmission mainly occurs. Second, the parasites may release factors that stimulate the host's immune and endocrinological systems to produce factors that enhance somatic growth and inhibit reproduction of the host. This benign relationship is considered to be indicative of long-term coevolution. The sex of the fish had a significant influence on the abundance of the parasites in total and also on particular species with the bias in all cases being in favour of the female fish. This review shows that sex bias in parasitism is generally not strong and that male bias in parasitism is not a general rule. Taken as a whole, the results fail to support most of the predictions based on the Hamilton-Zuk and the immunocompetence hypotheses. Possible hypotheses to explain why parasitism tends to be higher in female than in male trout include testosterone immunosuppression, corticosteroid-based immune suppression and differences between the size and behaviour of the sexes. However, the latter two hypotheses have more credence, although testosterone levels are higher in female than male trout. Between the early 1950s and 1998 there has been a marked decline in the prevalence, abundance and diversity of the helminth parasite communities in salmonid fish as well as their intermediate hosts. Possible reasons for these declines include heavy metal pollution, increased acidity and habitat degradation linked to changes in land use. It is concluded that although helminth parasites can provide supplementary information on pollution. the use of biotic indices based on the Biological monitoring working party (BMWP) or River invertebrate prediction and classification system (RIVPACS) methods are preferable. However, as these methods were designed to measure the impact of organic pollution they lack the sensitivity for measuring metal pollution. It is advocated therefore that new biomonitoring methods should be developed to measure the impact of heavy metal pollution using biotic indices based on the sampling of the susceptible invertebrate communities inhabiting depositing sediments in the transmission sites of helminth parasites.

Animals↗
PubMed1999

Apoptosis in parasites and parasite-induced apoptosis in the host immune system: a new approach to parasitic diseases.

Apoptosis, a form of programmed cell death (PCD), has been described as essential for normal organogenesis and tissue development, as well as for the proper function of cell-renewal systems in adult organisms. Apoptosis is also pivotal in the pathogenesis of several different diseases. In this paper we discuss, from two different points of view, the role of apoptosis in parasitic diseases. The description of apoptotic death in three different species of heteroxenic trypanosomatids is reviewed, and considerations on the phylogenesis of apoptosis and on the eventual role of PCD on their mechanism of pathogenesis are made. From a different perspective, an increasing body of evidence is making clear that regulation of host cell apoptosis is an important factor on the definition of a host-pathogen interaction. As an example, the molecular mechanisms by which Trypanosoma cruzi is able to induce apoptosis in immunocompetent cells, in a murine model of Chagas' disease, and the consequences of this phenomenon on the outcome of the experimental disease are discussed.

Animals↗
PubMed2001

A single ancient origin of brood parasitism in African finches: implications for host-parasite coevolution.

Robust phylogenies for brood-parasitic birds, their hosts, and nearest nesting relatives provide the framework to address historical questions about host-parasite coevolution and the origins of parasitic behavior. We tested phylogenetic hypotheses for the two genera of African brood-parasitic finches, Anomalospiza and Vidua, using mitochondrial DNA sequence data from 43 passeriform species. Our analyses strongly support a sister relationship between Vidua and Anomalospiza, leading to the conclusion that obligate brood parasitism evolved only once in African finches rather than twice, as has been the conventional view. In addition, the parasitic finches (Viduidae) are not recently derived from either weavers (Ploceidae) or grassfinches (Estrildidae), but represent a third distinct lineage. Among these three groups, the parasitic finches and estrildids, which includes the hosts of all 19 Vidua species, are sister taxa in all analyses of our full dataset. Many characters shared by Vidua and estrildids, including elaborate mouth markings in nestlings, unusual begging behavior, and immaculate white eggs, can therefore be attributed to common ancestry rather than convergent evolution. The host-specificity of mouth mimicry in Vidua species, however, is clearly the product of subsequent host-parasite coevolution. The lineage leading to Anomalospiza switched to parasitizing more distantly related Old World warblers (Sylviidae) and subsequently lost these characteristics. Substantial sequence divergence between Vidua and Anomalospiza indicates that the origin of parasitic behavior in this clade is ancient (approximately 20 million years ago), a striking contrast to the recent radiation of extant Vidua. We suggest that the parasitic finch lineage has experienced repeated cycles of host colonization, speciation, and extinction through their long history as brood parasites and that extant Vidua species represent only the latest iterations of this process. This dynamic process may account for a significantly faster rate of DNA sequence evolution in parasitic finches as compared to estrildids and other passerines. Our study reduces by one the tally of avian lineages in which obligate brood parasitism has evolved and suggests an origin of parasitism that involved relatively closely related species likely to accept and provide appropriate care to parasitic young. Given the ancient origin of parasitism in African finches, ancestral estrildids must have been parasitized well before the diversification of extant Vidua, suggesting a long history of coevolution between these lineages preceding more recent interactions between specific hosts and parasites.

Animals↗
PubMed2003

[Parasite detection and symptoms of parasitic diseases. 1: Blood parasites].

Blood parasites are malaria plasmodia, microfilaria species, trypanosomes (the causative agents of African sleeping sickness and South American Changas disease) and the causative agents of schistosomiasis of the bladder and the intestine. Their geographical distribution, incubation periods, signs and symptoms, microscopic and serological methods are described. In Germany around 1,000 tourists contract malaria every year, mostly travellers to Africa. Over 70% suffer from the life-threatening P. falciparum infection. Only a few days after the onset of this flu-like disease, complications may evolve. The best diagnostic method is the thin blood film. In case of a negative result this procedure must be repeated twice daily. The thick film requires experience. Rapid diagnostic tests can be helpful but are hampered by false negative results. Filaria loa loa may cause skin swellings, involvement of the eye and even the CNS; Wuchereria bancrofti can cause severe lymphedema. West African sleeping sickness (Trypanosoma gambiense) ends up in encephalitis, the East African form (T. rhodesiense) in a polyserositis. Schistosomiasis of the urinary bladder and the large intestine may cause severe diseases of the urinary tract or the liver.

Animals↗
PubMedDate not supplied

[Host-parasite interactions in Coccus hesperidum L. (Hom. Coccidae) and its parasite Coccophagus scutellaris Dalman (hum. Aphelinidae). III. Effect of the number of hosts and their sanitary conditions on the oviposition of the parasite].

Intensity of egg laying of Coccophagus scutellaris depends on the number of hosts available. It is found to be more important when the female has several hosts. Furthermore a better distribution of eggs is observed in that case. When parasited and parasiteless hosts are available, the female of Coccophagus deposits more eggs on the latter. This discriminating ability in relation to number and kinds of hosts available is discussed.

Animals↗
PubMed1997

Parasite faunas of freshwater fish: the relationship between richness and the specificity of parasites.

The relationship between the host specificity of parasites and the richness of the assemblages in which they occur was examined among the parasite faunas of Canadian freshwater fishes. The prediction tested was that rich faunas would consist of both generalist and specialist parasites, whereas poor faunas would include only generalists, a pattern known as nestedness. An index of nestedness was computed for parasite faunas of fish species in 5 large families (Salmonidae, Cyprinidae, Catostomidae, Centrarchidae and Percidae) and compared with the value expected if parasite faunas are random assemblages of parasites. There was no evidence of nested patterns among any of the 5 families of fish hosts. However, since both measures of host range of parasites (i.e. number of known host species) and richness of parasite faunas are affected by how intensely the different parasites and hosts have been studied, tests of nestedness may be flawed. After correcting both variables for study effort, negative correlations were found between the mean host range of parasites and the richness of the faunas to which they belong. In other words, parasites in rich faunas occurred on average in fewer host species, because of the many specialists, than parasites in poor faunas, which are mainly generalists. This relationship was apparent in all fish but the Salmonidae; fish species in this family have been introduced to new areas much more frequently than other fish, and their parasite faunas have thus had a distinct recent history. The general trend observed in non-salmonid fish suggests that parasite colonization and speciation may have been facilitated in some fish species, but not in others.

Animals↗
PubMed2025

Biomathematical enzyme kinetics model of prebiotic autocatalytic RNA networks: degenerating parasite-specific hyperparasite catalysts confer parasite resistance and herald the birth of molecular immunity.

Catalysis and specifically autocatalysis are the quintessential building blocks of life. Yet, although autocatalytic networks are necessary, they are not sufficient for the emergence of life-like properties, such as replication and adaptation. The ultimate and potentially fatal threat faced by molecular replicators is parasitism; if the polymerase error rate exceeds a critical threshold, even the fittest molecular species will disappear. Here we have developed an autocatalytic RNA early life mathematical network model based on enzyme kinetics, specifically the steady-state approximation. We confirm previous models showing that these second-order autocatalytic cycles are sustainable, provided there is a sufficient nucleotide pool. However, molecular parasites become untenable unless they sequentially degenerate to hyperparasites (i.e. parasites of parasites). Parasite resistance-a parasite-specific host response decreasing parasite fitness-is acquired gradually, and eventually involves an increased binding affinity of hyperparasites for parasites. Our model is supported at three levels; firstly, ribozyme polymerases display Michaelis-Menten saturation kinetics and comply with the steady-state approximation. Secondly, ribozyme polymerases are capable of sustainable auto-amplification and of surmounting the fatal error threshold. Thirdly, with growing sequence divergence of host and parasite catalysts, the probability of self-binding is expected to increase and the trend towards cross-reactivity to diminish. Our model predicts that primordial host-RNA populations evolved via an arms race towards a host-parasite-hyperparasite catalyst trio that conferred parasite resistance within an RNA replicator niche. While molecular parasites have traditionally been viewed as a nuisance, our model argues for their integration into the host habitat rather than their separation. It adds another mechanism-with biochemical precision-by which parasitism can be tamed and offers an attractive explanation for the universal coexistence of catalyst trios within prokaryotes and the virosphere, heralding the birth of a primitive molecular immunity.

Kinetics↗
PubMed1994

Behavioural defense against parasites: interaction with parasite invasiveness.

Behavioural patterns involved in avoiding, repelling, or removing parasites allow mammalian hosts to defend themselves from an array of parasites that threaten the host's fitness in the natural world. Some examples of behavioural defenses and the presumed target parasites are: grooming to remove ticks, grouping to reduce attack rate of biting flies, fly repelling movements to reduce parasitic flies, and selective grazing to reduce intake of faecal-borne parasites. These behavioural defenses are discussed with regard to effectiveness in controlling the target parasites. Parasites have sometimes evolved behavioural strategies of evading, penetrating or disabling these behavioural defenses. These parasite behavioural strategies, though less studied, are discussed. Also discussed is the possibility that host behavioural patterns that may defend against one parasite may be exploited by a different type of parasite to facilitate its own transmission. The interplay between host defensive strategies, the cost versus the effectiveness of such strategies, and a parasite's evasion or exploitation of such strategies, may be useful in understanding some aspects of host-parasite dynamics in nature.

Animals↗
PubMedDate not supplied

Density-dependent parasite establishment suggests infection-associated immunosuppression as an important mechanism for parasite density regulation in onchocerciasis.

The modulation of human immune response by filarial parasites has yielded contradictory experimental findings and attracted much controversy. We address the unresolved question of acquisition, establishment and accumulation of Onchocerca volvulus by using a modelling approach that relates computer simulations to cross-sectional data concerning parasite burdens in 913 West African onchocerciasis patients. It is shown that the acquisition of O. volvulus is not constant with host age; instead, the analysis of age profiles of parasite burdens strongly indicate the operation of immunosuppressive processes within the human host, associated with the presence of adult parasites or microfilariae. It is suggested that these processes suppress immunity against incoming infective larvae (L3), which themselves act as an immune modulating component once they have successfully overcome the barrier of concomitant immunity. Suppression of parasite-specific immunity leads to parasite establishment rates which increase along with the parasite burden, but which hardly depend on hyperendemic annual transmission potentials. Children, still immunocompetent due to low parasite burdens, acquire 0.1-0.5 adult female parasites per year, whereas older people, immunosuppressed due to high burdens, acquire 2-4 adult female parasites per year. Differences in parasite establishment between the forest and the savannah strains of O. volvulus are quantified and dynamic aspects of density-dependent parasite establishment discussed.

Adolescent↗
PubMed1997

Host-parasite coevolution: comparative evidence for covariation of life history traits in primates and oxyurid parasites.

The environmental factors that drive the evolution of parasite life histories are mostly unknown. Given that hosts provide the principal environmental features parasites have to deal with, and given that these features (such as resource availability and immune responses) are well characterized by the life history of the host, we may expect natural selection to result in covariation between parasite and host life histories. Moreover, some parasites show a high degree of host specificity, and cladistic analyses have shown that host and parasite phylogenies can be highly congruent. These considerations suggest that parasite and host life histories may covary. The central argument in the theory of life history evolution concerns the existence of trade-offs between traits. For parasitic nematodes it has been shown that larger body sizes induce higher fecundity, but this is achieved at the expense of delayed maturity. As high adult mortality would select for reduced age at maturity, the selective benefit of increased fecundity is expressed only if adult mortality is low. Parasite adult mortality may depend on a number of factors, including host longevity. Here we tested the hypothesis concerning the positive covariation between parasite body size (which reflects parasite longevity) and host longevity. To achieve this goal, we used the association between the pinworms (Oxyuridae, Nematoda) and their primate hosts. Oxyurids are highly host specific and are supposed to be involved in a coevolutionary process with their hosts. We found that female parasite body length was positively correlated with host longevity after correcting for phylogeny and host body mass. Conversely, male parasite body length and host longevity were not correlated. These results confirm that host longevity may represent a constraint on the evolution of body size in oxyurids, at least in females. The discrepancy between female and male oxyurids is likely to depend on the particular mode of reproduction of this taxon (haplodiploidy), which should result in weak (or even null) selection pressures to an increase of body size in males.

Animals↗