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PubMed2006

A quantitative trait locus for recognition of foreign eggs in the host of a brood parasite.

Avian brood parasites reduce the reproductive output of their hosts and thereby select for defence mechanisms such as ejection of parasitic eggs. Such defence mechanisms simultaneously select for counter-defences in brood parasites, causing a coevolutionary arms race. Although coevolutionary models assume that defences and counter-defences are genetically influenced, this has never been demonstrated for brood parasites. Here, we give strong evidence for genetic differences between ejector and nonejectors, which could allow the study of such host defence at the genetic level, as well as studies of maintenance of genetic variation in defences. Briefly, we found that magpies, that are the main host of the great spotted cuckoo in Europe, have alleles of one microsatellite locus (Ase64) that segregate between accepters and rejecters of experimental parasitic eggs. Furthermore, differences in ejection rate among host populations exploited by the brood parasite covaried significantly with the genetic distance for this locus.

Animals↗
PubMed2006

Testing the pluralist approach to sex: the influence of environment on synergistic interactions between mutation load and parasitism in Daphnia magna.

Both deleterious mutations and parasites have been acknowledged as potential selective forces responsible for the evolutionary maintenance of sexual reproduction. The pluralist approach to sex proposes that these two factors may have to interact synergistically in order to stabilize sex, and one of the simplest ways this could occur is if parasites are capable of causing synergistic epistasis between mutations in their hosts. However, the effects of both deleterious mutations and parasitism are known to be influenced by a range of environmental factors, so the nature of the interaction may depend upon the organisms' environment. Using chemically mutated Daphnia magna lines, we examined the effects of mutation and parasitism under a range of temperature and food regimes. We found that although parasites were capable of causing synergistic epistasis between mutations in their hosts, these effects were dependent upon an interaction between parasite genotype and temperature.

Animals↗
PubMed2006

The evolution of virulence and host specialization in malaria parasites of primates.

Parasite virulence, i.e. the damage done to the host, may be a by-product of the parasite's effort to maximize its fitness. Accordingly, several life-history trade-offs may explain interspecific differences in virulence, but such constraints remain little tested in an evolutionary context. In this phylogenetic study of primate malarias, I investigated the relationship between virulence and other parasite life-history traits. I used peak parasitaemia as a proxy for virulence, because it reflected parasite reproductive success and parasite-induced mortality. Peak parasitaemia was higher in specialist than in generalist species, even when confounding life-history traits were controlled. While there was a significant phylogenetic relationship between the number of competitors per host and host specialization, peak parasitaemia was unrelated to within-host competition. Therefore, the key evolutionary factor that favours virulence is host specialization, and the evolutionary success of virulent parasites, such as Plasmodium falciparum, may be better understood when the trade-off in virulence between different hosts is considered. Such phylogenetic results may help us design better protection programmes against malaria.

Animals↗
PubMedDate not supplied

Infection of Gymnodinium sanguineum by the dinoflagellate Amoebophrya sp.: effect of nutrient environment on parasite generation time, reproduction, and infectivity.

Preliminary attempts to culture Amoebophrya sp., a parasite of Gymnodinium sanguineum from Chesapeake Bay, indicated that success may be influenced by water quality. To explore that possibility, we determined development time, reproductive output, and infectivity of progeny (i.e. dinospores) for Amoebophyra sp. maintained on G. sanguineum grown in four different culture media. The duration of the parasite's intracellular growth phase showed no significant difference among treatments; however, the time required for completion of multiple parasite generations did, with elapsed time to the middle of the third generation being shorter in nutrient-replete media. Parasites of hosts grown in nutrient-replete medium also produced three to four times more dinospores than those infecting hosts under low-nutrient conditions, with mean values of 380 and 130 dinospores/host, respectively. Dinospore production relative to host biovolume also differed, with peak values of 7.4 per 1,000 microm3 host for nutrient-replete medium and 4.8 per 1,000 microm3 host for nutrient-limited medium. Furthermore, dinospores produced by "high-nutrient" parasites had a higher success rate than those formed by "low-nutrient" parasites. Results suggest that Amoebophrya sp. is well adapted to exploit G. sanguineum populations in nutrient-enriched environments.

Animals↗
PubMed1989

What is the significance of the presence of MHC molecules on the surface of parasites in human neurocysticercosis?

Sixteen cysticerci excised from 15 surgery patients were examined for the presence of HLA molecules on their surface, to confirm the role of these molecules in parasite damage and to investigate if HLA products are host specific or perhaps host-like antigens synthesized by the parasite. MoAbs against monomorphic and polymorphic HLA were chosen according to the patients HLA phenotypes. MoAbs against host and non-host antigens were selected and tested on cyst slides by indirect immunofluorescence assays. Host molecules were present in 43.7% of the cysts, but non-host antigens were also apparent in 62.5%. These results suggest mimicry as a possible mechanism to explain the presence of MHC products on the surface of the parasite; inflammation may also induce the expression of HLA that could become associated with the parasite. In vitro cellular immune response to specific antigens was also performed and positive responses correlated with the presence of HLA molecules on the cyst's surface. Moreover, damaged parasites had host molecules as well. Parasites from responder patients had all kind of HLA molecules or at least, antigenic determinants while the cysts from non-responders did not have molecules on their surface. These data support the role of HLA in cyst destruction.

Adult↗
PubMed1998

[Prevalence of intestinal parasites among Japanese residents in developing countries].

We examined fecal specimens of Japanese residents in developing countries in order to know the prevalence of intestinal parasites in the group. One fecal specimen was collected from each 981 (in 1995) and 1275 (in 1996) Japanese living in Asia, the Middle East, Europe, Africa and Latin America. The specimens were fixed with 10% formalin in each area, and were examined in Japan by concentration method (formalin-ether sedimentation) to find protozoan cysts or helminth eggs. The infection rate of intestinal parasites was 3.0% in 1995 and 2.4% in 1996. The rate was high in Africa (1995: 5.7%, 1996: 4.7%) and Asia (1995: 3.8%, 1996: 3.0%). Regarding to the species of the parasites, Giardia lamblia (17 cases), Trichuris trichiura (14) and Ascaris lumbricoides (11) were detected frequently. Additionally, 7 cases of Heterophyes heterophyes infection were found in Asia and the Middle East. The infection rate was higher in adults than that in children, and a positive relationship between the infection rate and duration of stay was observed. Among the Japanese infected with intestinal parasites, abdominal symptoms such as diarrhea or abdominal pain were common (36.8%). It is also noteworthy that 28.1% of the Japanese infected had a history of gastric diseases such as gastric ulcer. Although the infection rate of intestinal parasites among Japanese residents in developing countries was low, compared to that of the natives in the countries, the rate is still higher than that in Japanese living in the home country. It is necessary to continue preventive measures such as health education in order to eradicate intestinal parasitic infections from this group.

Adolescent↗
PubMed1970

Nest parasitism, productivity, and clutch size in purple martins.

Mean maximum nestling weight of purple martins decreased with increase in brood size from three to five. Martins in the absence of acarine nest parasites produced young heavier than parasitized young of the same brood size; in addition, unparasitized nestlings tended to reach a maximum weight equivalent to that of young in parasitized broods of one less member. Modal brood size for parasitized and unparasitized martins was four, but there was a significant trend toward production of broods of five by mite-free birds, and of broods of three by parasitized parents. This suggests a potentially important role for nest parasitism in the determination of clutch size in martins and other birds.

Animals↗
PubMed2005

A class of pantothenic acid analogs inhibits Plasmodium falciparum pantothenate kinase and represses the proliferation of malaria parasites.

The growth and proliferation of the human malaria parasite Plasmodium falciparum are dependent on the parasite's ability to obtain essential nutrients. One nutrient for which the parasite has an absolute requirement is the water-soluble vitamin pantothenic acid (vitamin B5). In this study, a series of pantothenic acid analogs which retain the 2,4-dihydroxy-3,3-dimethylbutyramide core of pantothenic acid but deviate in structure from one another and from pantothenic acid in the nature of the substituent attached to the amide nitrogen were synthesized using an efficient single-step synthetic route. Eight of 10 analogs tested inhibited the proliferation of intraerythrocytic P. falciparum parasites in vitro, doing so with 50% inhibitory concentrations between 15 and 200 microM. The compounds were generally selective, inhibiting the proliferation of a human cell line (the Jurkat cell line) only at concentrations severalfold higher than those required for inhibition of parasite growth. It was demonstrated that compounds in this series inhibited the phosphorylation of pantothenic acid by pantothenate kinase, the first step in the parasite's biosynthesis of the essential enzyme cofactor coenzyme A, doing so competitively, with K(i) values in the nanomolar range.

Animals↗
PubMed2007

Differential impact of simultaneous migration on coevolving hosts and parasites.

BACKGROUND: The dynamics of antagonistic host-parasite coevolution are believed to be crucially dependent on the rate of migration between populations. We addressed how the rate of simultaneous migration of host and parasite affected resistance and infectivity evolution of coevolving meta-populations of the bacterium Pseudomonas fluorescens and a viral parasite (bacteriophage). The increase in genetic variation resulting from small amounts of migration is expected to increase rates of adaptation of both host and parasite. However, previous studies suggest phages should benefit more from migration than bacteria; because in the absence of migration, phages are more genetically limited and have a lower evolutionary potential compared to the bacteria. RESULTS: The results supported the hypothesis: migration increased the resistance of bacteria to their local (sympatric) hosts. Moreover, migration benefited phages more than hosts with respect to 'global' (measured with respect to the whole range of migration regimes) patterns of resistance and infectivity, because of the differential evolutionary responses of bacteria and phage to different migration regimes. Specifically, we found bacterial global resistance peaked at intermediate rates of migration, whereas phage global infectivity plateaued when migration rates were greater than zero. CONCLUSION: These results suggest that simultaneous migration of hosts and parasites can dramatically affect the interaction of host and parasite. More specifically, the organism with the lower evolutionary potential may gain the greater evolutionary advantage from migration.

Biological Evolution↗
PubMed2005

Role of cholesterol in parasitic infections.

The requirement of cholesterol for internalization of eukaryotic pathogens like protozoa (Leishmaniasis, Malaria and Toxoplasmosis) and the exchange of cholesterol along with other metabolites during reproduction in Schistosomes (helminths) under variable circumstances are poorly understood. In patients infected with some other helminthes, alterations in the lipid profile have been observed. Also, the mechanisms involved in lipid changes especially in membrane proteins related to parasite infections remain uncertain. Present review of literature shows that parasites induce significant changes in lipid parameters, as has been shown in the in vitro study where substitution of serum by lipid/cholesterol in medium and in experimental models (in vivo). Thus changes in lipid profile occur in patients having active infections with most of the parasites. Membrane proteins are probably involved in such reactions. All parasites may be metabolising cholesterol, but the exact relationship with pathogenic mechanism is not clear. So far, studies suggest that there may be some factors or enzymes, which allow the parasite to breakup and consume lipid/cholesterol. Further studies are needed for better understanding of the mechanisms involved in vivo. The present review analysis the various studies till date and the role of cholesterol in pathogenesis of different parasitic infections.

Animals↗
PubMed2002

Host cells: mobilizable lipid resources for the intracellular parasite Toxoplasma gondii.

Successful replication of the intracellular parasite Toxoplasma gondii within its parasitophorous vacuole necessitates a substantial increase in membrane mass. The possible diversion and metabolism of host cell lipids and lipid precursors by Toxoplasma was therefore investigated using radioisotopic and fluorophore-conjugated compounds. Confocal microscopic analyses demonstrated that Toxoplasma is selective with regards to both the acquisition and compartmentalization of host cell lipids. Lipids were compartmentalized into parasite endomembranes and, in some cases, were apparently integrated into the surrounding vacuolar membrane. Additionally, some labels became concentrated in discrete lipid bodies that were biochemically and morphologically distinct from the parasite apical secretory organelles. Thin layer chromatography established that parasites readily scavenged long-chain fatty acids as well as cholesterol, and in certain cases modified the host-derived lipids. When provided with radiolabeled phospholipid precursors, including polar head groups, phosphatidic acid and small fatty acids, intracellular parasites preferentially accrued phosphatidylcholine (PtdCho) over other phospholipids. Moreover, Toxoplasma was found to be competent to synthesize PtdCho from radiolabeled precursors obtained from its environment. Together, these studies underscore the ability of Toxoplasma gondii to divert and use lipid resources from its host, a process that may contribute to the biogenesis of parasite membranes.

Animals↗
PubMed2005

Host-parasite interactions and the evolution of gene expression.

Interactions between hosts and parasites provide an ongoing source of selection that promotes the evolution of a variety of features in the interacting species. Here, we use a genetically explicit mathematical model to explore how patterns of gene expression evolve at genetic loci responsible for host resistance and parasite infection. Our results reveal the striking yet intuitive conclusion that gene expression should evolve along very different trajectories in the two interacting species. Specifically, host resistance loci should frequently evolve to co-express alleles, whereas parasite infection loci should evolve to express only a single allele. This result arises because hosts that co-express resistance alleles are able to recognize and clear a greater diversity of parasite genotypes. By the same token, parasites that co-express antigen or elicitor alleles are more likely to be recognized and cleared by the host, and this favours the expression of only a single allele. Our model provides testable predictions that can help interpret accumulating data on expression levels for genes relevant to host-parasite interactions.

Biological Evolution↗
PubMed2000

Aspects of the ecology of proteocephalid cestodes parasites of Sorubim lima (Pimelodidae) of the upper Paraná River, Brazil: I. Structure and influence of host's size and sex.

Between March 1992 and February 1996, 107 specimens of Sorubim lima were collected in the floodplain of the upper Paraná river. Ninety-five (88.78%) specimens were parasitized with at least one species of proteocephalid cestodes. 7,573 specimens of four different species were collected (average intensity 79.71 parasites/host): Paramonticellia itaipuensis Pavanelli & Rego, 1991; Nupelia portoriquensis Pavanelli & Rego, 1991; Spatulifer maringaensis Pavanelli & Rego, 1989 and Spasskyellina spinulifera Woodland, 1935. S. maringaensis was the most prevalent and abundant. There were three dominant species P. itaipuensis, S. maringaensis and N. portoriquensis) and one co-dominant species (S. spinulifera). The three environments (lotic, semilotic and lentic) in which collection was undertaken showed high similarity with regard to parasitic fauna. A high Simpson index value (0.359) indicates dominance tendency among species of parasites. Concerning S. maringaensis significant positive correlation was observed between parasite intensity and standard length of hosts. No species had negative correlation. With regard to S. maringaensis and N. portoriquensis prevalence was positive and significantly correlated with standard length of hosts. No species had negative correlation. In the case of S. maringaensis and N. portoriquensis influence of host's sex was noted on parasite intensity. There was no sex influence on parasite prevalence in any species.

Animals↗
PubMedDate not supplied

Control of parasitic infections among school children in the peri-urban area of Botucatu, São Paulo, Brazil.

The prevalence of intestinal parasitosis was investigated in a primary school located in Rubião Júnior, a peri-urban district of Botucatu, São Paulo state, Brazil, in order to assess the effect of treatment and practical measures of prophylaxis in the control of parasitic infections among 7-to-18-year-old school children of a low socio-economic status. The first series of parasitological examinations included 219 school children, of which 123 (56.1%) were found to be infected with one or more parasite species. Eighty-four children carrying pathogenic parasites were submitted to various anti-parasitic treatment schedules. We re-evaluated 75 (89%) students after 4 to 6 months post-chemotherapy. The results indicate that the combination of treatment with prophylactic measures has been successful in the control of parasitic infections, since reinfection rates were generally low (< or = 5.3%), except for Giardia lamblia infections (18.6%), and a marked reduction on the prevalence rates was observed with a significant percentage of cure (> or = 73.1%) in children infected with most parasite species. The reasons for the apparent failure in the control of infections caused by Hymenolepis nana and Strongyloides stercoralis are discussed.

Adolescent↗
PubMedDate not supplied

[Risk factors for multiple intestinal parasites in an indigenous community of the State of Pernambuco, Brazil].

An investigation into the ethno-epidemiological profile of the Pankararu indigenous group in the State of Pernambuco, Brazil, identified multiple intestinal parasites in nearly all members of the community. To detect possible environmental risk factors, we used the data base from a previous survey to test relations between daily living conditions (housing, sanitation, water supply and treatment, and garbage disposal) and the number of different parasite species found in the same household. The sample consisted of 84 families from the original sample of 112. Selection was based on the number of stool tests performed in the family. The mean number of parasite species was 5.0 per family, for a mean family size of 6.1 members. This number was greater for wattle-and-daub houses (mean 6.0 parasite species vs. 4.9 for brick houses; p < 0.03) and when water used in the household was not treated (mean 5.1 parasite species, vs. 4.5 for treated water; p < 0.05). Other household characteristics and hygienic habits did not significantly influence this number. We concluded that multiple intestinal parasitism in the Pernambuco Pankararu community is frequent, to the point of being the rule, and that it relates essentially to water source and treatment.

Adolescent↗
PubMed2001

Comparison of Diadegma insulare (Hymenoptera: Ichneumonidae) and Microplitis plutellae (Hymenoptera: Braconidae) as biological control agents of Plutella xylostella (Lepidoptera: Plutellidae): field parasitism, insecticide susceptibility, and host-searching.

Parasitism of Plutella xylostella (L.) third and fourth instars was evaluated in a cabbage field in Geneva, NY, in 1999. Over the entire season, average parasitism was 33.6% for third instars and 53.6% for fourth instars, and the main parasitoids were Diadegma insulare (Cresson) and Microplitis plutellae Muesbeck. In the early season, total parasitism was low, and mainly caused by D. insulare. However, later in the season, parasitism reached >80% for the fouth instars and 50% for the third instars. Our survey indicated that M. plutellae heavily parasitized P. xylostella, and provided higher parasitism rates than D. insulare in the late season. Comparison of these two species in laboratory bioassays indicated there were no significant differences in susceptibility to four insecticides commonly used in crucifer fields. For both parasitoids, an experience with P. xylostella on a damaged leaf increased their host-searching efficacy. Compared with M. plutellae, D. insulare was a better host-searcher both for the naive and the experienced adults. Although both parasitoids can cause high mortality rates of P. xylostella, D. insulare may be more suitable to be released in fields to enhance natural control against P. xylostella.

Animals↗
PubMed2000

Intestinal parasites of baboons (Papio cynocephalus anubis) and chimpanzees (Pan troglodytes) in Gombe National Park.

A survey of gastrointestinal parasites of nonhuman primates in Gombe National Park, Tanzania, was conducted during July and August 1989. Fresh fecal samples collected from 35 baboons (Papio cynocephalus anubis) and 20 chimpanzees (Pan troglodytes) were analyzed for intestinal parasites. Parasite identifications were based upon the size and appearance of eggs and larvae on both direct and fecal flotation examinations. Seven species of helminths and three species of protozoa were noted in the chimpanzees, and seven species of helminths, two species of trematodes, and one species of protozoa were noted in baboons. An unidentified parasite, with a thick egg shell similar to that of ascarids, was noted in both the chimpanzee and baboon population. Unfortunately a definitive identification of this parasite could not be made based upon egg size and morphology alone and insufficient numbers of larva were present to aid identification. One previously unreported parasite, Schistosoma mansoni, was identified in the baboon population. This is the first report of a schistosome in Gombe's nonhuman primate population.

Animals↗
PubMed2001

Seasonal transmission of gastrointestinal parasites of equids in southern Louisiana.

Parasite-naive pony foals were used as sentinels to monitor transmission of gastrointestinal parasites of equids in Louisiana during 4 seasons of the year. Two annual periods were studied, 1988-1989 and 1992-1993. Two or 3 foals each season were turned out to graze a contaminated pasture along with resident parasitized mares and their foals. After a grazing period of 8 wk, sentinel ponies were held in a parasite-free box stall for a period of 6 wk to allow parasites to develop, thus enhancing the evaluation of hypobiotic stages. Following this holding period, necropsies were performed for complete parasite recoveries. Data show that transmission of large and small strongyles occurs during all seasons in southern Louisiana, with highest levels of transmission occurring in the winter and only minimal transmission taking place in the summer. Numbers of mucosal cyathostomes, as well as total cyathostome numbers, were highest in the winter, and luminal cyathostome numbers were highest in the spring. Transmission of Anoplocephala perfoliata and Parascaris equorum occurred during all seasons of the year, although numbers of P. equorum were reduced in spring 1989 and 1993. Gasterophilus intestinalis instars were recovered from fall and winter sentinels only. Oxyuris equi L4 were found all seasons 1 yr, but only during the fall and winter of the final year.

Animal Husbandry↗