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PubMed2003

The syndermatan phylogeny and the evolution of acanthocephalan endoparasitism as inferred from 18S rDNA sequences.

The phylogeny of the Syndermata (Rotifera: Monogononta, Bdelloidea, Seisonidea; Acanthocephala: Palaeacanthocephala, Eoacanthocephala, Archiacanthocephala) is key to understanding the evolution of acanthocephalan endoparasitism from free-living ancestors. In the present study, maximum likelihood, distance/neighbor-joining, and maximum parsimony analyses have been carried out based on 18S rDNA data of 22 species (four new sequences). The results suggest a monophyletic origin of the Eurotatoria (Monogononta+Bdelloidea). Seison appears as the acanthocephalan sistergroup. Palaeacanthocephala split into an "Echinorhynchus"-and a "Leptorhynchoides"-group, the latter sharing a monophyletic origin with the Eoacanthocephala and Archiacanthocephala. As inferred from the phylogeny obtained acanthocephalan endoparasitism evolved from a common ancestor of Seison and Acanthocephala that lived epizoically on an early mandibulate. Probably, an acanthocephalan stem species invaded the mandibulate host, thus establishing an endoparasitic lifestyle. Subsequently, vertebrates (or gnathostomes) became part of the parasite's life cycle. In the stem line of the Archiacanthocephala, a terrestrial life cycle has evolved, with an ancestor of the Tracheata (Insecta, Myriapoda) acting as intermediate host.

Acanthocephala↗

PubMed2000

Vaccination against cysticercosis and hydatid disease.

Infections with the larval stages of taeniid cestode parasites cause substantial human morbidity as well as economic losses in domestic livestock species. Despite ongoing efforts around the world, few countries have been able substantially to reduce or eradicate these infections through the use of anthelmintics and lifestyle changes. Vaccines offer an additional potential tool to assist with the control of parasite transmission. Here, Marshall Lightowlers and colleagues review the substantial progress that has been made towards developing practical vaccines against hydatid disease in sheep and cysticercosis in sheep and cattle. Recombinant antigens have been used to induce more than 90% protection against challenge infections. Such success in animals encourages investigation of the potential use of vaccines in humans to prevent hydatid disease arising from infection with Echinococcus granulosus and cysticercosis from infection with Taenia solium.

Amino Acid Sequence↗

PubMed2004

Ant parasite queens revert to mating singly.

Multiple mating (polyandry) is widespread among animal groups, particularly insects. But the factors that maintain it and underlie its evolution are hard to verify because benefits and costs are not easily quantified and they tend to be similar in related species. Here we compare the mating strategies of the leaf-cutting ant Acromyrmex echinatior and its recently derived social parasite Acromyrmex insinuator, which is also its closest relative. We find that although the host queens mate with up to a dozen different males, the social parasite mates only singly. This rapid and surprising reversion to single mating in a socially parasitic ant indicates that the costs of polyandry are probably specific to a free-living lifestyle.

Animals↗

PubMed2005

Analysis of FMRFamide-like peptide (FLP) diversity in phylum Nematoda.

This study reports a series of systematic BLAST searches of nematode ESTs on the Genbank database, using search strings derived from known nematode FLPs (those encoded by Caenorhabditis elegans flp genes as well as those isolated from other nematodes including Ascaris suum), as well as query sequences representative of theoretical FLPs. Over 1000 putative FLP-encoding ESTs were identified from multiple nematode species. A total of 969 ESTs representing sequelogs of the 23 known C. elegans flp genes were identified in 32 species, from clades I, III, IV and V. Numerical analysis of EST numbers suggests that flp-1, flp-11 and flp-14 are amongst the most highly expressed flp genes. Speculative BLAST searches were performed using theoretical FLP C-termini as queries, in an attempt to identify putative novel FLP sequences in the EST database. These searches yielded eight multi-species sequelogs encoding FLPs with novel signatures that are believed to identify distinct flp genes. These novel genes encode 25 distinct previously unidentified FLPs, and raise the current total of known nematode flp genes to 31. Additionally, software-based analyses of the presence of signal peptides were performed, with signal peptides being identified on at least one member of each group of flp ESTs, further confirming their status as secreted peptides. The data reveal that nematode FLPs encompass the most complex neuropeptide family known within the metazoa. Moreover, individual FLPs and FLP motifs are highly conserved across the nematodes with little evidence for inter-clade or inter-lifestyle variation, supporting their fundamental role in free-living and parasitic species.

Amino Acid Sequence↗

PubMed1983

National case-control study of Kaposi's sarcoma and Pneumocystis carinii pneumonia in homosexual men: Part 1. Epidemiologic results.

To identify risk factors for the occurrence of Kaposi's sarcoma and Pneumocystis carinii pneumonia in homosexual men, we conducted a case-control study in New York City, San Francisco, Los Angeles, and Atlanta. Fifty patients (cases) (39 with Kaposi's sarcoma, 8 with pneumocystis pneumonia, and 3 with both) and 120 matched homosexual male controls (from sexually transmitted disease clinics and private medical practices) participated in the study. The variable most strongly associated with illness was a larger number of male sex partners per year (median, 61 for patients; 27 and 25 for clinic and private practice controls, respectively). Compared with controls, cases were also more likely to have been exposed to feces during sex, have had syphilis and non-B hepatitis, have been treated for enteric parasites, and have used various illicit substances. Certain aspects of a lifestyle shared by a subgroup of the male homosexual population are associated with an increased risk of Kaposi's sarcoma and pneumocystis pneumonia.

Acquired Immunodeficiency Syndrome↗

PubMed2006

Wolbachia genomes: revealing the biology of parasitism and mutualism.

Wolbachia bacteria are endosymbiotic partners of many animal species, in which they behave as either parasites (in arthropod hosts) or mutualists (in nematode hosts). What biochemistry and biology underpin these diverse lifestyles? The recent complete sequencing of genomes from Wolbachia that infect the arthropod Drosophila melanogaster and the nematode Brugia malayi, together with the partial genome sequencing of three Wolbachia strains found in drosophilids, enables this question to begin to be addressed. Parasitic arthropod Wolbachia are characterized by the presence of phages that carry ankyrin-repeat proteins; these proteins might be exported to the host cell to manipulate reproduction. In nematode Wolbachia, which lack these phages, several biochemical pathways can deliver essential metabolites to the nematode hosts. Nematode Wolbachia might also have a role in modulating the mammalian host immune system but the sequenced Wolbachia genomes lack the genes to synthesize lipopolysaccharide, raising questions about the nature of the inducing molecule. The Wolbachia surface protein might carry out this function.

Animals↗

PubMed2000

Does the presence of ant nests matter for oviposition to a specialized myrmecophilous Maculinea butterfly?

More than 50% of the lycaenid butterflies have an ant-associated lifestyle (myrmecophily) which may vary from coexistence to specific mutualistic or even parasitic interactions. Ant-related host-plant selection and oviposition has been observed in some myrmecophilous lycaenids. Therefore, it is remarkable that there is no evidence for this behaviour in the highly specialized, obligate myrmecophilous butterflies of the genus Maculinea. In contrast with previous findings, our results provide evidence for ant-related oviposition patterns in Maculinea alcon in relation to the distribution of specific host-ant nests (i.e. Myrmica ruginodis) based on repeated egg counts during the flight period in two populations. We also show that ant-related oviposition can be counterbalanced by intraspecific competition and oviposition deterrency when host plants already carry several eggs. Therefore, the absence of a correlation between egg load and the presence of host-ant nests at the end of the flight period should be interpreted carefully Whether ovipositional cues are obtained either directly (from ants or their nests) or indirectly (from vegetation structure), and whether alternative explanations based on the phenology and growth form of host plants are possible, is discussed.

Animals↗

PubMed2003

The evolution of myiasis in blowflies (Calliphoridae).

Blowflies (Calliphoridae) are characterised by the ability of their larvae to develop in animal flesh. Where the host is a living vertebrate, such parasitism by dipterous larvae is known as myiasis. However, the evolutionary origins of the myiasis habit in the Calliphoridae, a family which includes the blowflies and screwworm flies, remain unclear. Species associated with an ectoparasitic lifestyle can be divided generally into three groups based on their larval feeding habits: saprophagy, facultative ectoparasitism, and obligate parasitism, and it has been proposed that this functional division may reflect the progressive evolution of parasitism in the Calliphoridae. In order to evaluate this hypothesis, phylogenetic analysis of 32 blowfly species displaying a range of forms of ectoparasitism from key subfamilies, i.e. Calliphorinae, Luciliinae, Chrysomyinae, Auchmeromyiinae and Polleniinae, was undertaken using likelihood and parsimony methods. Phylogenies were constructed from the nuclear 28S large subunit ribosomal RNA gene (28S rRNA), sequenced from each of the 32 calliphorid species, together with suitable outgroup taxa, and mitochondrial cytochrome oxidase subunit I and II (COI+II) sequences, derived primarily from published data. Phylogenies derived from each of the two markers (28S rRNA, COI+II) were largely (though not completely) congruent, as determined by incongruence-length difference and Kishino-Hasegawa tests. However, the phylogenetic relationships of blowfly subfamilies based on molecular data did not concur with the pattern of relationships defined by previous morphological analysis; significantly, molecular analysis supported the monophyly of blowflies (Calliphoridae), distinct from the bot and warble flies (Oestridae). Comparative analysis of the myiasis habit based primarily on the 28S rRNA phylogeny indicated that obligate parasitism, and the ability to initiate myiasis in higher vertebrates, has multiple independent origins across myiasis-causing flies (Calliphoridae and Oestridae) and in at least three subfamilies of blowfly (Calliphoridae). Finally, the general association of various blowfly genera and subfamily clades with particular continental and geographical regions suggests that these groups probably came into existence in the Late Cretaceous period, following the break-up of Gondwana.

Animals↗

PubMed1980

Modes of ectoparasite reinfestations of deer mice (peromyscus maniculatus).

Modes of ectoparasite reinfestations were studied on ectoparasite-free deer mice (Peromyscus maniculatus) returned to their natural habitat on the Tule Lake National Wildlife Refuge, Siskiyou County, California, during the summer of 1977. The age of the host made no significant difference in the mode of reinfestation of lice, fleas, or mites. Flea reinfestation rates were related to the sex of the host, requiring 4 and 2 days, respectively, to reach control levels on male and female hosts. Mite populations reached the control level within 1 day, regardless of the sex of the host. No statistically significant louse reinfestations were noted within 8 days after the hosts were released. The percent of the host population reinfested with each ectoparsite followed the same patterns of reinfestation as the numbers of each parasite per host. It is suggested that the mode of ectoparasite reinfestations is a function of the behavior of the host relative to the lifestyles of the ectoparasite species.

Age Factors↗

PubMed2005

Unusual intestinal lamellae in the nematode Rhabditophanes sp. KR3021 (Nematoda: Alloinematidae).

The free-living nematode Rhabditophanes sp. has recently been placed in a clade of animal parasites and may be a unique example of a reversal to a nonparasitic lifestyle. Detailed morphological analysis of the intestine reveals the unusual and unique structure of splitting microlamellae forming a meshwork with cavities along the entire intestinal tract. Secretion vesicles were observed along the whole tract and along the length of the lamellae. It is suggested that these lamellae are adaptations to a different digestive strategy where low food availability and a low absorption surface are compensated for by maximizing the nutrient uptake efficiency along the entire length of the intestine. The likely reversal to a free-living life cycle may have caused drastic changes in diet, providing the necessary driving forces to such morphological changes.

Animals↗

PubMed2005

Prokaryotic K(+) channels: from crystal structures to diversity.

The deep roots and wide branches of the K(+)-channel family are evident from genome surveys and laboratory experimentation. K(+)-channel genes are widespread and found in nearly all the free-living bacteria, archaea and eukarya. The conservation of basic structures and mechanisms such as the K(+) filter, the gate, and some of the gate's regulatory domains have allowed general insights on animal K(+) channels to be gained from crystal structures of prokaryotic channels. Since microbes are the great majority of life's diversity, it is not surprising that microbial genomes reveal structural motifs beyond those found in animals. There are open-reading frames that encode K(+)-channel subunits with unconventional filter sequences, or regulatory domains of different sizes and numbers not previously known. Parasitic or symbiotic bacteria tend not to have K(+) channels, while those showing lifestyle versatility often have more than one K(+)-channel gene. It is speculated that prokaryotic K(+) channels function to allow adaptation to environmental and metabolic changes, although the actual roles of these channels in prokaryotes are not yet known. Unlike enzymes in basic metabolism, K(+) channel, though evolved early, appear to play more diverse roles than revealed by animal research. Finding and sorting out these roles will be the goal and challenge of the near future.

Archaea↗

PubMed2006

Ethnobotany of the Samburu of Mt. Nyiru, South Turkana, Kenya.

Traditional plant use is of extremely high importance in many societies, and prevalent in African communities. This knowledge is however dwindling rapidly due to changes towards a more Western lifestyle. The influence of modern tourism cannot be neglected in this context. This paper examines the plant use of the Samburu of the Mt. Nyiru area in Northern Kenya. The Samburu pastoralists of Kenya are still amongst the most traditional communities of the country and have retained most of their knowledge about the use of a large part of the plants in their environment for a wide variety of purposes. The results indicate that the local population has a very high knowledge of the plants in their surroundings, and attributes a purpose to a large percentage of the plants found. 448 plant species were collected, identified and their Samburu names and traditional uses recorded. 199 species were reported as of "no use". The high proportion of 249 plant species however had some traditional use: The highest number (180 species) was used as fodder, followed by 80 species that had medicinal use. Firewood (59 species), construction (42 species), tools (31 species), food (29 species) and ceremonial use (19 species) ranked far behind. Traditionally the Samburu attribute most illnesses to the effect of pollutants that block or inhibit digestion. This can include "polluted" food, contagion through sick people as well as witchcraft. In most cases the treatment of illness involves herbal purgatives to cleanse the patient. There are however frequent indications of plant use for common problems like wounds, parasites, body aches and burns. The change from a nomadic to a more sedentary lifestyle, often observed in other areas of the country, has affected the Samburu of remote Mt. Nyiru to a much lesser extent and did so far not lead to a major loss of traditional plant knowledge. However, overgrazing and over-exploitation of plant resources have already led to a decline of the plant material available.

Animal Feed↗

PubMed2005

Early life risk factors for atopic dermatitis in Ethiopian children.

BACKGROUND: Atopic dermatitis (AD) has increased in prevalence in many countries in recent decades, but the risk factors for AD in developing countries are unknown. Helminthic parasites may play a role in protecting against allergic disease, but few studies have investigated the association of AD with parasitic infection. OBJECTIVE: To establish the independent effects of parasitic infection and other early life factors on the risk of AD in Ethiopia. METHODS: We conducted a cross-sectional survey and nested case-control study of children age 1 to 5 years in Jimma and surrounding rural areas in southwest Ethiopia. Cases were defined according to the International Study of Asthma and Allergies in Childhood criteria for AD and confirmed by clinical examination. Information on lifestyle and other potential risk factors was collected by parental questionnaire, and stool samples were analyzed for parasites. RESULTS: Complete data were obtained on 306 AD cases defined by International Study of Asthma and Allergies in Childhood criteria (prevalence, 4.4%) and 426 controls. There was no reduction in the risk of AD in relation to intestinal parasite infection; in fact, AD was increased in subjects with Trichuris (1.61; 95% CI, 1.14-2.26). The risk of AD was also unrelated to family size, crowding in the home, or breast-feeding, but was related to previously unrecognized factors including malaria and access to piped drinking water. Similar findings were apparent in cases and controls confirmed by clinical examination. CONCLUSION: Neither intestinal parasite infection nor other proposed risk factors for AD appear to be related to the presence of the condition in young children in Ethiopia, suggesting that other factors may be more important in this population.

Allergens↗

PubMed2006

Pyruvate-converting activity in the spores of the microsporidian genus Paranosema (Antonospora).

Microsporidia, a large group of fungi-related protozoa with an obligate intracellular lifestyle, are characterized by a drastically reduced cell machinery and a unique metabolism. These parasites possess genes encoding glycolysis components and glycerol-phosphate shuttle, but lack typical mitochondria, Krebs cycle, respiratory chain and pyruvate-converting enzymes, except for two subunits of the E(1) enzyme of the pyruvate dehydrogenase complex. This study demonstrates that in spite of the above, destroyed spores of the microsporidian Paranosema (Antonospora) grylli and P. locustae deplete pyruvate content in the incubation medium. This activity is sensitive to heat, proportionally distributed between the soluble and the insoluble fractions and does not depend on additional ions or cofactors.

Culture Media↗

PubMed2004

Host gender in parasitic infections of mammals: an evaluation of the female host supremacy paradigm.

A review of current literature on mammalian hosts' sexual dimorphism (SD) in parasitic infections revealed that (1) it is a scarcely and superficially studied biological phenomenon of considerable significance for individual health, behavior, and lifestyles and for the evolution of species; (2) there are many notable exceptions to the rule of a favorable female bias in susceptibility to infection; (3) a complex network of molecular and cellular reactions connecting the host's immuno-neuroendocrine systems with those of the parasite is responsible for the host-parasite relationship rather than just an adaptive immune response and sex hormones; (4) a lack of gender-specific immune profiles in response to different infections; (5) the direct effects of the host hormones on parasite physiology may significantly contribute to SD in parasitism; and (6) the need to enrich the reductionist approach to complex biological issues, like SD, with more penetrating approaches to the study of cause-effect relationships, i.e., network theory. The review concludes by advising against generalization regarding SD and parasitism and by pointing to some of the most promising lines of research.

Animals↗

PubMedDate not supplied

Have gastrointestinal nematodes outwitted the immune system?

Gastrointestinal (GI) nematodes are incredibly successful parasites. Choosing to live in an exposed extracellular niche, in confrontation with a potentially hostile environment, their persistent, chronic lifestyle is persuasive evidence in itself for their profound ability to modulate their hosts' immune response. Modulation is essential to avoid their own destruction but also subtly balanced to avoid compromising host survival. This review describes the early circumstantial evidence that gave clues to the immunomodulatory capabilities of the GI nematodes, the roles that T regulatory cells and alternatively activated macrophages play in this immunomodulation and provides examples of the types of specific parasite-derived factors that are known to modulate host immunity, potentiating parasite survival.

Animals↗

PubMed2006

Subversion of innate and adaptive immune responses by Toxoplasma gondii.

The intracellular apicomplexan parasite Toxoplasma gondii is able to survive and persist in immunocompetent intermediate hosts for the host's life span. This is despite the induction of a vigorous humoral and -- more importantly -- cell-mediated immune response during infection. In order to establish and maintain such chronic infections, however, T. gondii has evolved multiple strategies to avoid or to interfere with potentially efficient anti-parasitic immune responses of the host. Such immune evasion includes (1) indirect mechanisms by altering the expression and secretion of immunomodulatory cytokines or by altering the viability of immune cells and (2) direct mechanisms by establishing a lifestyle within a suitable intracellular niche and by interference with intracellular signaling cascades, thereby abolishing a number of antimicrobial effector mechanisms of the host. Despite the parasite's ability to interfere successfully with the host's efforts to eradicate the infection, the immune response is, however, not completely abrogated but is rather partially diminished after infection. T. gondii thus keeps a delicate balance between induction and suppression of the host's immune response in order to guarantee the survival of the host as a safe harbor for parasite development and to allow its transmission to the definitive host.

Animals↗

PubMed2003

Immune deviation and the hygiene hypothesis: a review of the epidemiological evidence.

The epidemiological evidence for the proposal that early life immune deviation is the principal mechanism by which microbial agents prevent the development of atopy has been reviewed. Seven criteria are proposed which should ideally be fulfilled. The majority of studies only fulfill two or three criteria. For mycobacteria, measles and respiratory viruses there are studies that demonstrate a significant increase in atopy or allergic disease. Parasite infections, which provide a strong TH2 stimulus, are associated with reduced rather than enhanced allergen sensitization. The available epidemiological evidence does not provide support for a mechanism of early life immune deviation. The principal environmental influences on atopic disease are likely to occur throughout life and involve interactions between microbes and other non-infective and lifestyle factors.

Bacterial Infections↗