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PubMed1988

Impact of internal parasites on beef cattle.

Internal parasitism is a pervasive constant that reduces returns in beef cattle production. Parasitism may influence production sufficiently so that data derived investigating performance response will be erroneous. The interaction of internal parasites of cattle with other facets of their lives makes it imperative that more parasite research be done on cattle to consider their impact. Results of trials designed to determine forage production at various stocking densities may not reflect the nutritive value of the forage, but instead the severity of parasite exposure. Relative resistance or susceptibility to certain parasites vary with the breed of livestock and the species of parasite. Extensive work to evaluate the ability of various breeds and sires to influence parasitic numbers has been conducted in sheep but not in cattle. Some parasite trials have ignored the effects of nutrition on the establishment and retention of parasites. This becomes especially important where multiple parasite exposure may occur. Susceptible cattle, even on an optimal diet, will become parasitized, but if reexposed to the same species of parasite, cattle on an optimal diet may be able to resist reinfection, whereas those on deficient diets will not.

Animals↗

PubMed2006

The distribution of the intestinal parasitic diseases in the Southeast Anatolian (GAP=SEAP) region of Turkey.

OBJECTIVES: The physical alterations put in place by the Southeastern Anatolia Project will undoubtedly provide a remarkable economical growth and a social development in the area. In addition, the influence that formation of dam ponds, enlargement of irrigation areas, change of product and the way of cultivation, urbanization and industrialization will have an impact on the environment. To minimize the adverse effects of this process on human beings, a Community Health Project was completed by the teams participated by Ege, Dicle, Gaziantep and Harran Universities under the Directorate of Turkish Parasitology Association and by Southeastern Anatolia Project Regional Development Administration between 2001 and 2003. RESULTS: To identify individuals with parasite, feces samples were taken from a total of 4,470 individuals. Parasites were found in feces of 41.8% of men, 44.3% of women and 32.2% of children, 0-59 months old, who were included in the research and gave feces samples for parasites tests. These prevalence values indicate how widespread parasitic diseases are in the region. The high prevalence of parasitic diseases in this area is one of the causes of malnutrition in 40% of children. Parasites were detected in 44.2% of feces samples taken from rural areas and in 39.5% taken from urban areas. When the distribution of parasites detected in feces samples was studied, the most common parasites were Giardia intestinalis (18.1%), Entamoeba coli (11.8%), Ascaris lumbricoides (4.8%), Trichuris trichiura (4.5%) and Hymenolepis nana (3.9%). Distribution of parasites according to cities varied widely. The most frequently seen parasites were T. trichiura in Gaziantep; G. intestinalis in Batman, Mardin, Diyarbakir, Sirnak and Sanliurfa; and E. coli in Siirt, Kilis and Adiyaman. CONCLUSIONS: This study is the first investigation of intestinal parasite prevalence in a large region, specifically, in this GAP region and in Turkey, in general. There is no direct relationship between irrigating the cultivation areas and diffusion of parasitic diseases because the existence of intestinal parasites mentioned above is not related to the range of irrigation of cultivation areas, but is related to factors already discussed.

Adult↗

PubMed2002

Effects of brood parasitism on host reproductive success: evidence from larval interactions among dung beetles.

This paper investigates the effect of brood parasitism in a dung beetle assemblage in an arid region of Spain. The study was conducted during the spring season (March-May 1994-1998) using mesh cylinders buried into the ground, filled with sand and with sheep dung on top. We quantified the proportion of nests containing larvae of parasitic beetles and their effect on host larvae survival. Experiments on the effect of parasitic larvae on host-larvae survival were conducted by placing scarab brood masses (raised from captive scarabs in the laboratory) in containers with and without aphodiid larvae. During the spring, dung desiccation is rapid, preventing aphodiids nesting in the dung, and forcing these species to adopt brood parasitism as a nesting strategy. Parasitic aphodiids were found in 12-47% of scarab nests of three species. The incidence of brood parasitization was positively related with the number of brood masses contained in the nests, being also higher in the most abundant species. Field data and experiments showed that brood parasites significantly reduced host larvae survival from 74.8% in non-parasitized nests to 8.8% in parasitized nests. Because different rates of nest parasitization and mortality were caused by parasites, brood parasitism had a differential effect on different host species. Thus, brood parasitism constitutes an important mortality factor reducing the reproductive success of the host species and potentially affecting the beetle abundance in the area.

Animals↗

PubMed2003

Nematoda: genes, genomes and the evolution of parasitism.

Nematodes are remarkably successful, both as free-living organisms and as parasites. The diversity of parasitic lifestyles displayed by nematodes, and the diversity of hosts used, reflects both a propensity towards parasitism in the phylum, and an adaptability to new and challenging environments. Parasitism of plants and animals has evolved many times independently within the Nematoda. Analysis of these origins of parasitism using a molecular phylogeny highlights the diversity underlying the parasitic mode of life. Many vertebrate parasites have arthropod-associated sister taxa, and most invade their hosts as third stage larvae: these features co-occur across the tree and thus suggest that this may have been a shared route to parasitism. Analysis of nematode genes and genomes has been greatly facilitated by the Caenorhabditis elegans project. However, the availability of the whole genome sequence from this free-living rhabditid does not simply permit definition of 'parasitism' genes; each nematode genome is a mosaic of conserved features and evolutionary novelties. The rapid progress of parasitic nematode genome projects focussing on species from across the diversity of the phylum has defined sets of genes that have patterns of evolution that suggest their involvement with various facets of parasitism, in particular the problems of acquisition of nutrients in new hosts and the evasion of host immune defences. With the advent of functional genomics techniques in parasites, and in particular the possibility of gene knockout using RNA interference, the roles of many putative parasitism genes call now be tested.

Animals↗

PubMed1985

The population dynamics of competition between parasites.

A number of published studies of competition between parasite species are examined and compared. It is suggested that two general levels of interaction are discernible: these correspond to the two levels of competition recognized by workers studying free-living animals and plants: 'exploitation' and 'interference' competition. The former may be defined as the joint utilization of a host species by two or more parasite species, while the latter occurs when antagonistic mechanisms are utilized by one species either to reduce the survival or fecundity of a second species or to displace it from a preferred site of attachment. Data illustrating both levels of interaction are collated from a survey of the published literature and these suggest that interference competition invariably operates asymmetrically. The data are also used to estimate a number of population parameters which are important in determining the impact of competition at the population level. Theoretical models of host-parasite associations for both classes of competition are used to examine the expected patterns of population dynamics that will be exhibited by simple two-species communities of parasites that utilize the same host population. The analysis suggests that the most important factor allowing competing species of parasites to coexist is the statistical distribution of the parasites within the host population. A joint stable equilibrium should be possible if both species are aggregated in their distribution. The size of the parasite burdens at equilibrium is then determined by other life-history parameters such as pathogenicity, rates of resource utilization and antagonistic ability. Comparison of these theoretical expectations with a variety of sets of empirical data forms the basis for a discussion about the importance of competition in natural parasite populations. The models are used to assess quantitatively the potential for using competing parasite species as biological control agents for pathogens of economic or medical importance. The most important criterion for identifying a successful control agent is an ability to infect a high proportion of the host population. If such a parasite species also exhibits an intermediate level of pathology or an efficient ability to utilize shared common resources, antagonistic interactions between the parasite species contribute only secondarily to the success of the control. Competition in parasites is compared with competition in free-living animals and plants. The comparison suggests further experimental tests which may help to assess the importance of competition in determining the structure of more complex parasite-host communities.

Animals↗

PubMed2005

The coevolutionary dynamics of obligate ant social parasite systems--between prudence and antagonism.

In this synthesis we apply coevolutionary models to the interactions between socially parasitic ants and their hosts. Obligate social parasite systems are ideal models for coevolution, because the close phylogenetic relationship between these parasites and their hosts results in similar evolutionary potentials, thus making mutual adaptations in a stepwise fashion especially likely to occur. The evolutionary dynamics of host-parasite interactions are influenced by a number of parameters, for example the parasite's transmission mode and rate, the genetic structure of host and parasite populations, the antagonists' migration rates, and the degree of mutual specialisation. For the three types of obligate ant social parasites, queen-tolerant and queen-intolerant inquilines and slavemakers, several of these parameters, and thus the evolutionary trajectory, are likely to differ. Because of the fundamental differences in lifestyle between these social parasite systems, coevolution should further select for different traits in the parasites and their hosts. Queen-tolerant inquilines are true parasites that exert a low selection pressure on their host, because of their rarity and the fact that they do not conduct slave raids to replenish their labour force. Due to their high degree of specialisation and the potential for vertical transmission, coevolutionary theory would predict interactions between these workerless parasites and their hosts to become even more benign over time. Queen-intolerant inquilines that kill the host queen during colony take-over are best described as parasitoids, and their reproductive success is limited by the existing worker force of the invaded host nest. These parasites should therefore evolve strategies to best exploit this fixed resource. Slavemaking ants, by contrast, act as parasites only during colony foundation, while their frequent slave raids follow a predator prey dynamic. They often exploit a number of host species at a given site, and theory predicts that their associations are best described in terms of a highly antagonistic coevolutionary arms race.

Animals↗

PubMed2004

Fish host-cestode parasite stable isotope enrichment patterns in marine, estuarine and freshwater fishes from Northern Canada.

Cestode parasites from freshwater (threespine stickleback, Gasterosteus aculeatus), estuarine (brook charr, Salvelinus fontinalis) and marine (Greenland cod, Gadus ogac) fish from northern Quebec, Canada, were used to investigate the hypotheses that cestode parasites are (13)C and (15)N enriched relative to host food sources, but (15)N depleted with respect to host muscle tissue as a result of differential enrichment during the assimilation of common nutrient sources. Cestode parasites and fish were generally similarly enriched in (13)C with respect to common food sources and, in the case of Greenland cod, cestode parasites were (13)C enriched relative to host tissue. Cestode parasites were also generally (15)N enriched with respect to mean host dietary signatures, but depleted with respect to host muscle tissue. In the case of Greenland cod cestode parasites, no significant (15)N enrichment relative to host dietary signature was observed. Cestode parasites appear generally to experience smaller (15)N enrichment than hosts as a result of trophic transfer of common dietary sources. Differential (15)N enrichment patterns in parasites and fish may be attributed to differences in parasite and host metabolism, particularly the anaerobic and aerobic natures of their respective metabolisms. Results imply that isotope enrichment paradigms developed for the study of aquatic foodwebs cannot be routinely applied to quantitatively assess the role of parasites in aquatic foodwebs and that reference to host muscle tissue measures will not allow accurate characterization of parasite foodweb position. Appropriate reference to assimilated food sources is required to accurately estimate parasite isotopic enrichment patterns and to determine parasite trophic position relative to the host.

Animals↗

PubMed2003

Comparative tests of parasite species richness in primates.

Some hosts harbor diverse parasite communities, whereas others are relatively parasite free. Many factors have been proposed to account for patterns of parasite species richness, but few studies have investigated competing hypotheses among multiple parasite communities in the same host clade. We used a comparative data set of 941 host-parasite combinations, representing 101 anthropoid primate species and 231 parasite taxa, to test the relative importance of four sets of variables that have been proposed as determinants of parasite community diversity in primates: host body mass and life history, social contact and population density, diet, and habitat diversity. We defined parasites broadly to include not only parasitic helminths and arthropods but also viruses, bacteria, fungi, and protozoa, and we controlled for effects of uneven sampling effort on per-host measures of parasite diversity. In nonphylogenetic tests, body mass was correlated with total parasite diversity and the diversity of helminths and viruses. When phylogeny was taken into account, however, body mass became nonsignificant. Host population density, a key determinant of parasite spread in many epidemiological models, was associated consistently with total parasite species richness and the diversity of helminths, protozoa, and viruses tested separately. Geographic range size and day range length explained significant variation in the diversity of viruses.

Animals↗

PubMed2001

Solute flux into parasitic plants.

Parasitic plants form intimate contacts with host tissue in order to gain access to host solutes. There are a variety of cell types within the host which parasitic plants could access to extract solutes. Depending on the degree to which the parasite has embraced the parasitic lifestyle, the extent of solute flux and the pathways used to transfer solutes from host to parasite will vary. To date, a variety of experimental approaches argue for diversity in the mechanisms and the routes by which parasites accumulate host solutes. Contact between host and parasite ranges from direct lumen-to-lumen links between host and parasite xylem and continuity between the sieve elements of host and parasite, to the involvement of transfer cells between host and parasite. Progress has been slow since Solms-Laubach distinguished types of parasitic plants that fed from host phloem or xylem in 1867, but advances in clearly delineating the pathways that link host and parasite should now be possible using fluorescent proteins expressed and restricted to particular cell types of the host. This will initially necessitate using Arabidopsis, but should allow the types of connection, i.e. symplasmic or apoplasmic, to be determined and then the identification of parasite transporters responsible for solute flux.

Adaptation, Physiological↗

PubMed2006

Diversity, distribution and exchange of blood parasites meeting at an avian moving contact zone.

Research on contact zones has paid relatively little attention to host-parasite interactions, although these situations have important but different implications depending on whether one considers the host or the parasite's perspective. We investigated both the role of a host contact zone in parasite expansion and whether parasites could influence contact zone dynamics. We studied the diversity and the patterns of parasite exchange (genera Haemoproteus and Plasmodium) infecting two parapatric sibling passerines meeting at a moving contact zone in western Europe. We amplified and sequenced a fragment of the parasite cytochrome b gene. The expanding host harboured more diverse parasites, which might indicate a superior ability to face a diverse parasite fauna than the receding host. Prevalence was very high in both hosts, due to the frequent occurrence of two sister Haemoproteus lineages. Despite the recent movement of the contact zone, these two parasites fitted almost perfectly to the geographic range of their main host species. Yet, we found several cases of cross-species infection in sympatric areas and evidences of asymmetrical spreading of parasites from the expanding host towards the receding host. Altogether, our results suggest that the host contact zone mainly acts as a barrier to parasite expansion even if recurrent host shifts are observed. Besides, they also support the idea that parasite-mediated competition might contribute to the displacement of hosts' contact zones, thereby emphasizing the role of parasitism on the population dynamics of sympatric species.

Animals↗

PubMed2005

Phenotypic plasticity of host-parasite interactions in response to the route of infection.

The microsporidium Octosporea bayeri can infect its host, the planktonic crustacean Daphnia magna, vertically and horizontally. The two routes differ greatly in the way the parasite leaves the harbouring host (transmission) and in the way it enters a new, susceptible host (infection). Infections resulting from each route may thus vary in the way they affect host and parasite life-histories and, subsequently, host and parasite fitness. We conducted a life-table experiment to compare D. magna infected with O. bayeri either horizontally or vertically, using three different parasite isolates. Both the infection route and the parasite isolate had significant effects on host life-history. Hosts matured at different ages depending on the parasite isolate, and at a size that varied with infection route. The frequency of host sterility and the host's life-time reproductive success were affected by both the infection route and the parasite isolate. The infection route also affected parasite life-history. The production of parasite spores was much higher in vertically than in horizontally infected hosts. We found a trade-off between the production of spores (the parasite's horizontal fitness component) and the production of infected host offspring (the parasite's vertical fitness component). This study shows that hosts and parasites can react plastically to different routes of infection, suggesting that ecological factors that may influence the relative importance of horizontal and vertical transmission can shape the evolution of host and parasite life histories, and, consequently, the evolution of virulence.

Age Factors↗

PubMed1996

[Role of host behavior in the life cycle of parasites].

Parasite is an organism which, at least in a part of its ontogeny uses another living organism as a proper environment for its life. In the "parasite-host" relationships, formed by both these components, the parasite itself bears the burden of formation and maintenance of these relationships in a balance. Three factors play the main role in this process: (1) physiological adaptations of the parasite, enabling survival in the host body and resistance against defence reactions of the host; (2) morphological adaptations, leading to changes in the body structure of the parasite, dependent on location in the host body; and (3) behavioural adaptations assuring contacts of parasites with their hosts. In the process of evolution most groups of parasites evolved a complicated life cycle, with change of host and outer environment, succeeding in maturation of the parasite and production of the offspring. To pursuit this aim the parasite takes advantage from the behaviour of its potential host, its food preferences (e.g. by inclusion into a food chain), periodic or circadian migrations, and generally from its mode of life. The parasite modifies behaviour of its hosts, sometimes to a high degree, especially the behaviour of intermediate hosts, making them more conspicuously displayed for predators, the most often their final hosts. The parasite itself changes also its behaviour to be more attractive for a potential host or to enhance the possibility of finding a proper host. Finally, in a host population the parasite bears upon the position of particular host individuals by degradation of dominants and shifting them from reproduction. This phenomenon may be considered as a self-defence of the host population against reproduction of ill individuals, weaken by a burden of parasites.

Animals↗

PubMed1997

Community ecology of the metazoan parasites of grey mullets, Mugil platanus (Osteichthyes: Mugilidae) from the littoral of the state of Rio de Janeiro, Brazil.

One hundred and fifty specimens of grey mullets, Mugil platanus Günther, collected from the littoral of the State of Rio de Janeiro, Brazil, between June 1984 to August 1988, were necropsied to study their infracommunities of metazoan parasites. Twenty-five species of metazoan parasites were collected. One hundred and forty-nine (99.3%) fishes were parasitized by one or more metazoan species. According to their importance values, 13 species were considered dominant, 7 species codominant and 2 species subordinate (digeneans were the majority of the total number of parasite specimens collected, with 63.7%). The presence of larval stages of digeneans and cestodes suggest that M. platanus is at an intermediate level in the marine trophic web. The Simpson index for all parasite species was low (0.059) indicating lack of dominance by a particular species in the parasite community. The parasites of M. platanus showed a typical overdispersed pattern of distribution. The capture localities of the hosts were consolidated into 3 groups and its parasite communities showed high qualitative and quantitative similarity, with high values for the Sorenson similarity coefficient and Percent similarity coefficient. Six species had a positive correlation between the host's total body length and parasite intensity, while three species had a negative correlation. Four species had a positive correlation between the host's total body length and parasite prevalence and one species had negative correlation. Five parasite species had differences in prevalence and intensity in relation to sex of host, but these differences were confounded with the total length of male and female fishes. The mean diversity in the infracommunities of M. platanus was H' = 0.936 +/- 0.477, without correlation with the host's total length and without significant difference between male and female fishes. In the ectoparasites, the infracommunities showed overall positive association, 6 pairs of copepod species had a significant positive association. One pair of species showed a negative covariation between parasite intensities. Infracommunities of endoparasites also showed overall positive association, and four species pairs of digeneans had a significant positive association. Only one had a negative association. The specialist components with low prevalence values predominated in the parasite community, which, based on these factors, was considered closer to the isolationist type.

Animals↗

PubMed1997

[The fate of parasites of animal origin transmitted to humans].

The fate of a parasite transmitted from an animal to man depends on the ability of the contaminating agent to reach a place where it can thrive, to find necessary nutrients, and to resist host defense mechanisms. The purpose of this study was to evaluate the incidence of transmission of parasites from animals to man and to determine to what extent transmission is followed by development. Stenoxenic parasites whose life cycle requires transmission from animals to man obviously develop in man and then return to animals. These parasites cause holozoonoses of the cyclozoonosis type. Some euryxenic parasites can develop as well in man as in animals. These parasites can cause holozoonoses of the amphixenoses type. Other presumably euryxenic parasites can be transmitted from animals to man but not vice versa. These parasites are hemizoonoses agents. Non-transmission back from man to animals can be observed under several circumstances: incomplete development in man with failure to reach the stage at which transmission back to animals is possible; full development but with immaturity or sterility of the elements of dissemination necessary for transmission back to animals; full development but no way of evacuating elements of dissemination; full development and evacuation but with failure of elements of dissemination to survive. In these four cases man constitutes a dead-end for the parasite. A fifth possibility is that the parasite reaches full development but transmission back to animals cannot occur because man is not preyed upon by a carnivorous animal. In this case parasites are potential agents of holozoonoses and man is a cul-de-sac for the involved parasites.

Angiostrongylus↗

PubMed1999

Egg-laying behaviour by shiny cowbirds parasitizing brown-and-yellow marshbirds.

We studied the laying behaviour of shiny cowbirds, Molothrus bonariensis, parasitizing brown-and-yellow marshbirds, Pseudoleistes virescens. Shiny cowbirds lay two egg morphs, spotted and white immaculate. Brown-and-yellow marshbirds eject the white egg morph but accept the spotted morph. The incidence of parasitism in this host was 66.5%, and half of the parasitized nests had more than one shiny cowbird egg. There was a positive relationship between the number of parasitic events and the availability of nests in the laying stage, but parasitic events reached a plateau when the availability of nests was high. The distribution of parasitic eggs per nest was more clumped than expected by chance. Shiny cowbird females synchronized parasitism with host laying in 80% of the cases. They seldom parasitized nests before the host started laying or after the nest had been deserted or predated. The majority of multiply parasitized nests were parasitized by more than one female. Females that lay white eggs did not avoid parasitizing brown-and-yellow marshbird nests. Egg pecking by cowbird females resulted, on average, in one egg lost per parasitic event and the probability of being broken was greater for host eggs when host and parasitic eggs where both in the nest. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed2004

Protein kinases as targets for anti-parasitic chemotherapy.

Parasitic protozoa infecting humans have a staggering impact on public health, especially in the developing world. Furthermore, several protozoan species are major pathogens of domestic animals and have a considerable impact on food production. In many instances, the parasites have developed resistance against available chemotherapeutic agents, making the search for alternative drugs a priority. In line with the current interest in protein kinases inhibitors as potential drugs against a variety of diseases, the possibility that protein kinases may represent targets for novel anti-parasitic agents is being explored. Research into parasite protein kinases has benefited greatly from genome and EST sequencing projects, with the genomes of a few species fully sequenced (notably that of the human malaria parasite Plasmodium falciparum) and several more under way. The overall picture that emerged from research in this area shows that the phylogenetic isolation of parasitic protozoa is reflected by atypical structural and functional properties of many of their protein kinase homologues. Likewise, evidence is emerging, which suggests that the organisation of some otherwise well-conserved signal transduction pathways is divergent in some parasitic species. The differences between protein kinases of a parasite and their homologues in its host cell suggest that specific inhibition of the former can be achieved. The development of anti-parasitic drugs based on protein kinase inhibition is being pursued following two avenues: one consists of screening chemical libraries on recombinant enzymes; several protein kinases from parasitic protozoa are now available for this approach. The second approach relies on the identification of the molecular targets of kinase inhibitors which display anti-parasitic properties. This has led to promising developments in a few instances, in particular regarding PKG as a drug target against Eimeria and Toxoplasma, and purvalanol B, a purine-based CDK inhibitor which appears to affect unexpected targets in several protozoan parasites. The recent resolution of the structure of a Plasmodium protein kinase complexed with small inhibitory molecules opens the way to a rational approach towards the design of anti-parasitic drugs based on kinase inhibition.

Animals↗

PubMed1997

Heme biosynthesis by the malarial parasite. Import of delta-aminolevulinate dehydrase from the host red cell.

The mouse and human malarial parasites, Plasmodium berghei and Plasmodium falciparum, respectively, synthesize heme de novo following the standard pathway observed in animals despite the availability of large amounts of heme, derived from red cell hemoglobin, which is stored as hemozoin pigment. The enzymes, delta-aminolevulinate dehydrase (ALAD), coproporphyrinogen oxidase, and ferrochelatase are present at strikingly high levels in the P. berghei infected mouse red cell in vivo. The isolated parasite has low levels of ALAD and the data clearly indicate it to be of red cell origin. The purified enzyme preparations from the uninfected red cell and the parasite are identical in kinetic properties, subunit molecular weight, cross-reaction with antibodies to the human enzyme, and N-terminal amino acid sequence. Immunogold electron microscopy of the infected culture indicates that the enzyme is present inside the parasite and, therefore, is not a contaminant. The parasite derives functional ALAD from the host and the enzyme binds specifically to isolated parasite membrane in vitro, suggestive of the involvement of a receptor in its translocation into the parasite. While, ALAD, coproporphyrinogen oxidase, and ferrochelatase from the parasite and the uninfected red cell supernatant have identical subunit molecular weights on SDS-polyacrylamide gel electrophoresis and show immunological cross-reaction with antibodies to the human enzymes, as revealed by Western analysis, the first enzyme of the pathway, namely, delta-aminolevulinate synthase (ALAS) in the parasite, unlike that of the red cell host, does not cross-react with antibodies to the human enzyme. However, ALAS enzyme activity in the parasite is higher than that of the infected red cell supernatant. We therefore conclude that the parasite, while making its own ALAS, imports ALAD and perhaps most of the other enzymes of the pathway from the host to synthesize heme de novo, and this would enable it to segregate this heme from the heme derived from red cell hemoglobin degradation. ALAS of the parasite and the receptor(s) involved in the translocation of the host enzymes into the parasite would be unique drug targets.

Animals↗

PubMed1998

Acute Plasmodium chabaudi chabaudi malaria infection induces antibodies which bind to the surfaces of parasitized erythrocytes and promote their phagocytosis by macrophages in vitro.

CBA/Ca mice infected with 5 x 10(4) Plasmodium chabaudi chabaudi AS-parasitized erythrocytes experience acute but self-limiting infections of relatively short duration. Parasitemia peaks ( approximately 40% infected erythrocytes) on day 10 or 11 and is then partially resolved over the ensuing 5 to 6 days, a period referred to as crisis. How humoral and cellular immune mechanisms contribute to parasite killing and/or clearance during crisis is controversial. Humoral immunity might be parasite variant, line, or species specific, while cellular immune responses would be relatively less specific. For P. c. chabaudi AS, parasite clearance is largely species and line specific during this time, which suggests a primary role for antibody activity. Accordingly, acute-phase plasma (APP; taken from P. c. chabaudi AS-infected mice at day 11 or 12 postinfection) was examined for the presence of parasite-specific antibody activity by enzyme-linked immunosorbent assay. Antibody binding to the surface of intact, live parasitized erythrocytes, particularly those containing mature (trophozoite and schizont) parasites, was demonstrated by immunofluorescence in APP and the immunoglobulin G (IgG)-containing fraction thereof. Unfractionated APP (from P. c. chabaudi AS-infected mice), as well as its IgG fraction, specifically mediated the opsonization and internalization of P. c. chabaudi AS-parasitized erythrocytes by macrophages in vitro. APP from another parasite line (P. c. chabaudi CB) did not mediate the same effect against P. c. chabaudi AS-parasitized erythrocytes. These results, which may represent one mechanism of parasite removal during crisis, are discussed in relation to the parasite variant, line, and species specificity of parasite clearance during this time.

Acute Disease↗