EVOLUTION, Issue 7 2010
Hélène Magalon
In parasites with mixed modes of transmission, ecological conditions may determine the relative importance of vertical and horizontal transmission for parasite fitness. This may lead to differential selection pressure on the efficiency of the two modes of transmission and on parasite virulence. In populations with high birth rates, increased opportunities for vertical transmission may select for higher vertical transmissibility and possibly lower virulence. We tested this idea in experimental populations of the protozoan Paramecium caudatum and its bacterial parasite Holospora undulata. Serial dilution produced constant host population growth and frequent vertical transmission. Consistent with predictions, evolved parasites from this "high-growth" treatment had higher fidelity of vertical transmission and lower virulence than parasites from host populations constantly kept near their carrying capacity ("low-growth treatment"). High-growth parasites also produced fewer, but more infectious horizontal transmission stages, suggesting the compensation of trade-offs between vertical and horizontal transmission components in this treatment. These results illustrate how environmentally driven changes in host demography can promote evolutionary divergence of parasite life history and transmission strategies. [source]

WHEN SHOULD A TROPHICALLY TRANSMITTED PARASITE MANIPULATE ITS HOST?

EVOLUTION, Issue 2 2009
Geoffrey A. Parker
We investigate evolution of two categories of adaptive host manipulation by trophically transmitted helminths: (1) predation suppression decreases the host's mortality before the helminth is capable of establishing in its next host; (2) predation enhancement increases the existing host's mortality after it can establish in its next host. If all parasite mortality is purely random (time-independent), enhancement must increase predation by the next host sufficiently more (depending on manipulative costs) than it increases the average for all forms of host mortality; thus if host and parasite die only through random predation, manipulation must increase the "right" predation more than the "wrong" predation. But if almost all parasites die in their intermediate host through reaching the end of a fixed life span, enhancement can evolve if it increases the right predation, regardless of how much it attracts wrong predators. Although enhancement is always most favorable when it targets the right host, suppression aids survival to the time when establishment in the next host is possible: it is most favorable if it reduces all aspects of host (and hence parasite) mortality. If constrained to have selective effects, suppression should reduce the commonest form of mortality. [source]

YOU CAN'T KEEP A GOOD PARASITE DOWN: EVOLUTION OF A MALE-KILLER SUPPRESSOR UNCOVERS CYTOPLASMIC INCOMPATIBILITY

EVOLUTION, Issue 5 2008
Emily A. Hornett
Maternally inherited parasites are known to impose a wide variety of reproductive manipulations upon their host. These often produce strong selection on the host to suppress the parasite, resulting in a reduction in the frequency of the parasite. However, in the butterfly Hypolimnas bolina, infected with a Wolbachia bacterium, field data demonstrate that suppression of the male-killing phenotype does not depress parasite frequency. Here we test and verify one hypothesis to explain this apparent paradox,Wolbachia induces a second phenotype, Cytoplasmic Incompatibility (CI), in populations where host suppression has evolved. We further demonstrate that the capacity to induce CI has not evolved de novo, but instead is instantaneously expressed upon the survival of infected males. The significance of these results is threefold: (1) multiple phenotypes can provide Wolbachia with the means to maintain itself in a host following suppression of a single manipulative phenotype; (2) the ability to induce CI can remain hidden in systems in which male-killing is observed, just as the ability to induce male-killing may be obscured in strains exhibiting CI; (3) the evolutionary maintenance of CI in a system in which it is not expressed suggests a functional link with male-killing or other traits under selection. [source]

ADVICE OF THE ROSE: EXPERIMENTAL COEVOLUTION OF A TREMATODE PARASITE AND ITS SNAIL HOST

EVOLUTION, Issue 1 2007
Britt Koskella
Understanding host-parasite coevolution requires multigenerational studies in which changes in both parasite infectivity and host susceptibility are monitored. We conducted a coevolution experiment that examined six generations of interaction between a freshwater snail (Potamopyrgus antipodarum) and one of its common parasites (the sterilizing trematode, Microphallus sp.). In one treatment (recycled), the parasite was reintroduced into the same population of host snails. In the second treatment (lagged), the host snails received parasites from the recycled treatment, but the addition of these parasites did not begin until the second generation. Hence any parasite-mediated genetic changes of the host in the lagged treatment were expected to be one generation behind those in the recycled treatment. The lagged treatment thus allowed us to test for time lags in parasite adaptation, as predicted by the Red Queen model of host,parasite coevolution. Finally, in the third treatment (control), parasites were not added. The results showed that parasites from the recycled treatment were significantly more infective to snails from the lagged treatment than from the recycled treatment. In addition, the hosts from the recycled treatment diverged from the control hosts with regard to their susceptibility to parasites collected from the field. Taken together, the results are consistent with time lagged, frequency-dependent selection and rapid coevolution between hosts and parasites. [source]

MINIMAL SELFING, FEW CLONES, AND NO AMONG-HOST GENETIC STRUCTURE IN A HERMAPHRODITIC PARASITE WITH ASEXUAL LARVAL PROPAGATION

EVOLUTION, Issue 3 2006
Charles D. Criscione
Abstract Little is known about actual mating systems in natural populations of parasites or about what constitutes the limits of a parasite deme. These parameters are interesting because they affect levels of genetic diversity, opportunities for local adaptation, and other evolutionary processes. We expect that transmission dynamics and the distribution of parasites among hosts should have a large effect on mating systems and demic structure, but currently we have mostly speculation and very few data. For example, infrapopulations (all the parasites in a single host) should behave as demes if parasite offspring are transmitted as a clump from host to host over several generations. However, if offspring are well mixed, then the parasite component population (all the parasites among a host population) would function as the deme. Similarly, low mean intensities or a high proportion of worms in single infections should increase the selfing rate. For species having an asexual amplification stage, transmission between intermediate and definitive (final) hosts will control the variance in clonal reproductive success, which in turn could have a large influence on effective sizes and rates of inbreeding. We examined demic structure, selfing rates, and the variance in clonal reproductive success in natural populations of Plagioporus shawi, a hermaphroditic trematode that parasitizes salmon. Overall levels of genetic diversity were very high. An a posteriori inference of population structure overwhelmingly supports the component population as the deme, rather than individual infrapopulations. Only a single pair of 597 adult individuals was identified as clones. Thus, the variance in clonal reproductive success was almost zero. Despite being hermaphroditic, P. shawi appears to be almost entirely outcrossing. Genetic estimates of selfing (<5%) were in accordance with the proportion of parasites from single infections. Thus, it appears that individual flukes outcross whenever possible and only resort to selfing when alone. Finally, our data support the hypothesis that aquatic transmission and the use of several intermediate hosts promotes high genetic diversity and well-mixed infrapopulations. [source]

GEOGRAPHICAL VARIATION OF THE PARASITE, PHYLLOBOTHRIUM DELPHINI (CESTODA), IN BALL'S PORPOISE, PHOCOENOIDES DALLI, IN THE NORTHERN NORTH PACIFIC, BERING SEA, AND SEA OF OKHOTSK

MARINE MAMMAL SCIENCE, Issue 2 2001
William A. Walker
Abstract Prevalence of the larval cestode, Phyllobothrium delphini, was estimated from 2,445 Dall's porpoise, Phocoenoides dalli, from the incidental take of the Japanese high seas salmon drift-net fishery in the northwestern North Pacific Ocean, Bering Sea, and a local hand harpoon fishery in the southern Sea of Okhotsk. Prevalence of P. delphini was 22.7% in the northwestern North Pacific Ocean and 1.4% in the Bering Sea. This parasite was not found in the southern Sea of Okhotsk. Geographical differences in the prevalence of P. delphini may be due, at least in part, to regional differences in abundance of elasmobranchs known to feed on marine mammals and suspected as hosts of the parasite. Estimated intensity of infection of individual porpoises by P. delphini was low (estimated mean intensity of 3.5 plerocercoids per animal). This is a low intensity of infection compared to other species of small cetaceans studied and may be due to both differences in regional abundance of elasmobranchs and the comparatively short life span of P. dalli. [source]

THE UNIDENTIFIED PARASITE: A PROBABLE CASE OF NORTH AMERICAN CUTEREBRID MYIASIS IN A PEDIATRIC PATIENT

PEDIATRIC DERMATOLOGY, Issue 4 2004
ALEXANDRA H. AHMET M.D., B.SC.
No abstract is available for this article. [source]

PARASITES, THEIR RELATIONSHIPS AND THE DISINTEGRATION OF SCROPHULARIACEAE SENSU LATO

CURTIS'S BOTANICAL MAGAZINE, Issue 4 2010
Michael F. Fay
Summary. Plants that parasitise other plants have been among the most difficult plant groups to fit into classification systems due to their modified biology and their often highly reduced morphology. They are now considered to be found in about 16 families of flowering plants. Here we summarise current ideas about their relationships and provide information about their characteristics and utilisation. A major consequence of the revised classification of Orobanchaceae and related families has been the break-up of the traditional Scrophulariaceae, and here we summarise the new classification, focusing on genera of horticultural interest. [source]

ON THE EVOLUTION OF SEXUAL REPRODUCTION IN HOSTS COEVOLVING WITH MULTIPLE PARASITES

EVOLUTION, Issue 6 2010
Rafal Mostowy
Host,parasite coevolution has been studied extensively in the context of the evolution of sex. Although hosts typically coevolve with several parasites, most studies considered one-host/one-parasite interactions. Here, we study population-genetic models in which hosts interact with two parasites. We find that host/multiple-parasite models differ nontrivially from host/single-parasite models. Selection for sex resulting from interactions with a single parasite is often outweighed by detrimental effects due to the interaction between parasites if coinfection affects the host more severely than expected based on single infections, and/or if double infections are more common than expected based on single infections. The resulting selection against sex is caused by strong linkage-disequilibria of constant sign that arise between host loci interacting with different parasites. In contrast, if coinfection affects hosts less severely than expected and double infections are less common than expected, selection for sex due to interactions with individual parasites can now be reinforced by additional rapid linkage-disequilibrium oscillations with changing sign. Thus, our findings indicate that the presence of an additional parasite can strongly affect the evolution of sex in ways that cannot be predicted from single-parasite models, and that thus host/multiparasite models are an important extension of the Red Queen Hypothesis. [source]

THE EFFECTS OF MATING SYSTEM AND GENETIC VARIABILITY ON SUSCEPTIBILITY TO TREMATODE PARASITES IN A FRESHWATER SNAIL, LYMNAEA STAGNALIS

EVOLUTION, Issue 12 2004
Mikael Puurtinen
Abstract The amount and distribution of genetic variability in host populations can have significant effects on the outcome of host-parasite interactions. We studied the effect of mating system and genetic variability on susceptibility of Lymnaea stagnalis snails to trematode parasites. Mating system of snails from eight populations differing in the amount of genetic variability was manipulated, and self- and cross-fertilized offspring were exposed to naturally occurring trematode parasites in a controlled lake experiment. Susceptibility of snails varied between populations, but mating-system treatment did not have a significant effect. Heterozygosity of snails was negatively correlated with the probability of trematode infection, however, suggesting that parasitic diseases may pose a serious threat to populations lacking genetic variability. [source]

MOLECULAR EVIDENCE FOR THE ORIGIN OF WORKERLESS SOCIAL PARASITES IN THE ANT GENUS POGONOMYRMEX

EVOLUTION, Issue 10 2002
Joel D. Parker
Abstract., Speciation of two social parasites from their respective hosts is tested using a molecular phylogeny. Alignment of 711 DNA base pairs of mitochondrial cytochrome b gene was used to assess phylogenetic relationships of inquiline species to their hosts and to other members of the genus. We show that the inquiline social parasites of the North American seed harvester ants are monophyletic, descending from one of the known hosts (Pogonomyrmex barbatus) in the recent past and shifting hosts in a pattern similar to that observed in other Hymenopteran social parasites. In addition, the host populations unexpectedly were found to be polyphyletic. Populations of Pogonomyrmex rugosus from an area east of the Chiricahua Mountains in Southern Arizona belong to a mitochondrial clade separate from the more western clade of P. rugosus from the Sonoran and Chihuahuan Deserts. Evidence of mitochondrial DNA introgression between P. rugosus and P. barbatus was also observed. We conclude that Emery's rule does not strictly hold for this system, but that the hosts and parasites are very closely related, supporting a loose definition of Emery's rule. [source]

Notes: FOOD AND PARASITES FROM TWO HOURGLASS DOLPHINS, LAGENORHYNCHUS CRUCIGER (QUOY AND GAIMARD, 1824), FROM PATAGONIAN WATERS

MARINE MAMMAL SCIENCE, Issue 4 2003
Mercedes Fernández
[source]

Family Changes in the Context of Lowest-Low Fertility: The Case of Japan

INTERNATIONAL JOURNAL OF JAPANESE SOCIOLOGY, Issue 1 2008
Makoto Atoh
Abstract: Japan has currently one of the lowest-low fertility rates in the world. Low fertility in Japan is due to the extreme postponement of marriage and childbearing, and their weak recuperation in women in their 30s, as well as very low levels of cohabitation and extra-marital fertility. Both changing and unchanged aspects of families are related to lowest-low fertility in Japan. Although premarital sexual activities have increased, women's contraceptive initiative is very weak: they may be connected with weak partnership formation. "Parasite singles", "freeters", or "NEETs", probably related to weak family formation, have increased, but they may be connected with strong filial bondage derived from the traditional family system, i.e. Women have been normatively, educationally, and occupationally emancipated, but gender norms are currently divided in half among Japanese people, which may deter the revising of working conditions for women with children, leading to delaying family formation among working women. Lowest-low fertility conversely brings about family changes. Its direct effect is the increase of lifetime celibacy and childless couples, which may jeopardize the universality of families. Its indirect effect is through policy response to low fertility as well as labor shortages and population aging: recently, both family and labor policies have been strengthened to make it easier for working women to continue their jobs after marriage and childbirth, which might in turn promote family formation in Japan. [source]

Specific Isolation of RNA from the Grape Powdery Mildew Pathogen Erysiphe necator, an Epiphytic, Obligate Parasite

JOURNAL OF PHYTOPATHOLOGY, Issue 1 2010
Lance Cadle-Davidson
Abstract RNA expression profiling of obligately parasitic plant microbes is hampered by the requisite interaction of host and parasite. This can be especially problematic in the case of powdery mildews, such as Erysiphe necator (syn. Uncinula necator), which grow superficially but tightly adhere to the plant epidermis. We developed and refined a simple and efficient technique in which nail polish was used to remove conidia, appressoria, hyphae, conidiophores, and developing ascocarps of E. necator from grapevine (Vitis vinifera) leaves and showed that RNA isolated after removal was not contaminated with V. vinifera RNA. This approach can be applied to expression analyses throughout fungal development and could be extended to other epiphytic pathogens and saprophytes. [source]

A parasite-driven wedge: infectious diseases may explain language and other biodiversity

OIKOS, Issue 9 2008
Corey L. Fincher
Parasite,host coevolutionary races are spatially variable across species' or human cultural ranges. Assortative sociality, biased toward local conspecifics, and limited dispersal (philopatry) in humans and other organisms can be adaptive through reduced contact with dangerous contagions harbored by distant/non-local conspecifics. These factors can generate cultural or population divergence. Thus, parasites are like a wedge driving groups apart through their effective creation of anticontagion behaviors. If this proposition is correct, then biological diversity should positively correlate with parasite diversity. Here we show that the worldwide distribution of indigenous human language diversity, a form of biodiversity, is strongly, positively related to human parasite diversity indicative of a legacy of parasite-mediated diversification. The significant pattern remains when potential confounds are removed. The pattern too is seen in each of the six world regions and is not confounded by regional differences in their history of colonization and conquest. We hypothesize that variation in limited dispersal and assortative sociality with conspecifics in response to the worldwide spatial variation in pathogen diversity provides a fundamental mechanism of population divergence explaining many important aspects of the geographic patterns of biodiversity. This hypothesis has broad implications for a diversity of research topics including language diversity, cultural evolution, speciation, phylogeny and biogeography. [source]

Light and Electron Microscopy of the Spore of Myxobolus heckelii n. sp. (Myxozoa), Parasite from the Brazilian Fish Centromochlus heckelii (Teleostei, Auchenipteridae)

THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 6 2009
CARLOS AZEVEDO
ABSTRACT. A myxosporean parasitizing the gill filaments of the freshwater teleost fish Centromochlus heckelii collected in the Tocantins River (Lower Amazonian Region, Brazil) is described using light and electron microscopy. This parasite produces spherical to ellipsoidal cyst-like plasmodia up to 250 ,m in diameter, with a thick wall strengthened by several stratified juxtaposed crossed collagen layers, whose thickness varies according to the number of the layers. Several compressed fibroblasts are observed among the collagen fibrils. Deposits of spherical dense material are scattered at the internal periphery of the cysts. Plasmodia and different developmental stages, including immature and mature spores, filled the central region of the cysts. The spore body is ellipsoidal in valvar view and biconvex in sutural view. It is formed by two equal-sized and symmetric valves measuring 12.7 ,m long (12.2,13.1) (n=50), 6.6 ,m wide (6.3,6.9) (n=25), and 4.0 ,m (3.7,4.4) (n=20) thick. A thin layer formed by fine and anastomosed microfibrils is observed at the spore surface. Two equal, elongated pyriform polar capsules measure 2.9 ,m (2.7,3.3) × 1.7 ,m (1.4,2.0) (n=25), each containing four or five oblique polar filament coils. The binucleated sporoplasm contains numerous spherical sporoplasmosomes, glycogen particles, and a large vacuole with fine granular matrix. Based on the morphological and ultrastructural differences and specificity of the host, we describe this isolate as a new myxosporidian, Myxobolus heckelii n. sp. (Myxozoa, Myxosporea). [source]

Ultrastructural Studies of Henneguya rhamdia n. sp. (Myxozoa) a Parasite from the Amazon Teleost Fish, Rhamdia quelen (Pimelodidae)

THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 6 2005
EDILSON MATOS
Abstract. Henneguya rhamdia n. sp. is described in the gill filaments of the teleost fish Rhamdia quelen, collected from the Peixe Boi River, State of Pará, Brazil. This myxosporean produced spherical to ellipsoidal plasmodia, up to 300 ,m in diameter, which contained developmental stages, including spores. Several dense bodies up to 2 ,m in diameter were observed among the spores. The spore body was ellipsoidal (13.1 ,m in length, 5.2 ,m in width, and 2.5 ,m in thickness) and each of the two valves presented a tapering tail (36.9 ,m in length). These valves surrounded the binucleated sporoplasm cell and two equal ellipsoidal polar capsules (4.7 × 1.1 ,m), which contained 10,11 (rarely 12) polar filament coils. The sporoplasm contained sporoplasmosomes with a laterally eccentric dense structure with a half-crescent section. Based on the data obtained by electron microscopy and on the host specificity, the spores differed from previously described Henneguya species, mainly in their shape and size, number and arrangement of the polar filament coils, and sporoplasmosome morphology. [source]

Identification of a New Microsporidian Parasite Related to Vittaforma corneae in HIV-Positive and HIV-Negative Patients from Portugal

THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2003
IRSHAD M. SULAIMAN
ABSTRACT. Fecal samples from 22 HIV-positive and 3 HIV-negative patients from Portugal with symptomatic diarrhea were diagnosed positive for microsporidia by microscopy, with most parasites detected significantly bigger than Enterocytozoon bieneusi and Encephalitozoon spp. Sequence characterization of the small subunit (SSU) rRNA gene identified a microsporidian parasite with 96% homology to two published Vittaforma corneae sequences. Phylogenetic analysis confirmed the genetic relatedness of this new microsporidian parasite to Vittaforma corneae as well as Cystosporogenes operophterae. Results of the study demonstrate the presence of a new human-pathogenic microsporidian species, which is responsible for significant number of infections in HIV-positive and HIV-negative patients in Portugal. [source]

Parasite loads are higher in the tropics: temperate to tropical variation in a single host-parasite system

ECOGRAPHY, Issue 4 2008
Daniel J. Salkeld
Parasites are important selective forces upon the evolutionary ecology of their hosts. At least one hypothesis suggests that high species diversity in the tropics is associated with higher parasite abundance in tropical climates. Few studies, however, have directly assessed whether parasite abundance is higher in the tropics. To address this question, it is ideal, although seldom achievable, to compare parasite abundance in a single species that occurs over a geographical area including both temperate and tropical regions. We examined variation in blood parasite abundance in seven populations of a single lizard host species (Eulamprus quoyii) using a transect that spans temperate and tropical climates. Parasite prevalence (proportion of the host population infected) showed no geographical pattern. Interestingly though, parasite load was higher in lizard populations in the tropics, and was related to mean annual temperature, but not to rainfall. We speculate that in this system the relationship between latitude and parasite load is most likely due to variation in host life history over their geographic range. [source]

Parasites and the neutral theory of biodiversity

ECOGRAPHY, Issue 1 2004
Robert Poulin
First page of article [source]

Parasites lost , do invaders miss the boat or drown on arrival?

ECOLOGY LETTERS, Issue 4 2010
Catriona J. MacLeod
Ecology Letters (2010) 13: 516,527 Abstract Host species that colonize new regions often lose parasite species. Using population arrival and establishment data for New Zealand's introduced bird species and their ectoparasitic chewing lice species, we test the relative importance of different processes and mechanisms in causing parasite species loss. Few lice failed to arrive in New Zealand with their hosts due to being missed by chance in the sample of hosts from the original population (missing the boat). Rather, most lice were absent because their hosts or the parasite themselves failed to establish populations in their new environment. Given they arrived and their host established, parasite persistence was more strongly related to factors associated with transmission efficiency (number of host individuals introduced, host body size, host sociality and parasite suborder) than parasite propagule pressure and aggregation. Such insights into parasite success are invaluable to both understanding and managing their impact. [source]

Parasites in food webs: the ultimate missing links

ECOLOGY LETTERS, Issue 6 2008
Kevin D. Lafferty
Abstract Parasitism is the most common consumer strategy among organisms, yet only recently has there been a call for the inclusion of infectious disease agents in food webs. The value of this effort hinges on whether parasites affect food-web properties. Increasing evidence suggests that parasites have the potential to uniquely alter food-web topology in terms of chain length, connectance and robustness. In addition, parasites might affect food-web stability, interaction strength and energy flow. Food-web structure also affects infectious disease dynamics because parasites depend on the ecological networks in which they live. Empirically, incorporating parasites into food webs is straightforward. We may start with existing food webs and add parasites as nodes, or we may try to build food webs around systems for which we already have a good understanding of infectious processes. In the future, perhaps researchers will add parasites while they construct food webs. Less clear is how food-web theory can accommodate parasites. This is a deep and central problem in theoretical biology and applied mathematics. For instance, is representing parasites with complex life cycles as a single node equivalent to representing other species with ontogenetic niche shifts as a single node? Can parasitism fit into fundamental frameworks such as the niche model? Can we integrate infectious disease models into the emerging field of dynamic food-web modelling? Future progress will benefit from interdisciplinary collaborations between ecologists and infectious disease biologists. [source]

Parasites in the food web: linking amphibian malformations and aquatic eutrophication

ECOLOGY LETTERS, Issue 7 2004
Pieter T. J. Johnson
Abstract Emerging diseases are an ever-growing affliction of both humans and wildlife. By exploring recent increases in amphibian malformations (e.g. extra or missing limbs), we illustrate the importance of food web theory and community ecology for understanding and controlling emerging infections. Evidence points to a native parasite, Ribeiroia ondatrae, as the primary culprit of these malformations, but reasons for the increase have remained conjectural. We suggest that the increase is a consequence of complex changes to aquatic food webs resulting from anthropogenic disturbance. Our results implicate cultural eutrophication as a driver of elevated parasitic infection: (1) eutrophication causes a predator-mediated shift in snail species composition toward Planorbella spp., (2) Planorbella are the exclusive first intermediate hosts of R. ondatrae and (3) Ribeiroia infection is a strong predictor of amphibian malformation levels. Our study illustrates how the effects of anthropogenic disturbance on epidemic disease can be mediated through direct and indirect changes in food web structure. [source]

Circumferential mural bands in the small intestine causing simple obstructive colic: a case series

EQUINE VETERINARY JOURNAL, Issue 4 2006
J. F. PEREZ OLMOS
Summary Reasons for performing study: Circumferential mural band (CMB) in the small intestine is an emerging condition in Ireland. The clinical presentation is a simple obstruction of the small intestine of unknown aetiology. Hypothesis: Horses affected with CMB in the small intestine have a good prognosis following surgical decompression into the caecum. Methods: A retrospective study was carried out and 28 cases identified from 559 colic surgeries performed over a 5.5 year period. An exploratory celiotomy was performed in every case. A simple obstruction at the mid or distal jejunum was identified caused by a CMB, which was multiple in some cases. All of the horses except 2 had undergone a regular anthelmintic programme. Results: Manual decompression of the small intestine into the caecum resulted in resolution of the simple jejunal obstruction. A constricted segment of small intestine was resected in one case, as the degree of constriction was severe. A full thickness biopsy was taken from another case. Histopathology was performed on both samples. All horses recovered from surgery and were discharged from the hospital 7,32 days post operatively. Short-term complications were observed. Survival rate was 100% at long-term follow-up. Histopathology showed inflammatory infiltration in the submucosa, muscularis and serosa with eosinophils predominating. Parasites were not detected. Conclusion and potential relevance: Small intestine circumferential mural bands have a good prognosis after surgical decompression of the small intestine into the caecum. [source]

Parasitized Salamanders are Inferior Competitors for Territories and Food Resources

ETHOLOGY, Issue 4 2000
Daria S. Maksimowich
Parasites have been shown to impair the behaviour of their hosts, compromising the host's ability to exploit and compete for resources. We conducted two experiments to determine whether infestation with an ectoparasitic mite (Hannemania eltoni) was associated with changes in aggressive and foraging behaviour in the Ozark zigzag salamander, Plethodon angusticlavius. In a first experiment, male salamanders with high parasite loads were less aggressive overall than males with low parasite loads during territorial disputes. In addition, males with high parasite loads were more aggressive toward opponents with high parasite loads (symmetric contests) than toward opponents with low parasite loads (asymmetric contests). In contrast, males with low parasite loads did not adjust their level of aggression according to the parasite load of the opponent. In a second experiment, foraging behaviour of females was tested in response to ,familiar' (Drosophila) prey and ,novel' (termite) prey. Latency to first capture was significantly longer for parasitized than non-parasitized females when tested with ,familiar' prey, but not for ,novel' prey. Our results suggest that parasite-mediated effects may have profound influences on individual fitness in nature. [source]

A review of Evolutionary Ecology of Parasites, by Robert Poulin

EVOLUTION AND DEVELOPMENT, Issue 5 2007
Oliver Balmer
No abstract is available for this article. [source]

Host,parasite interactions and competition between tubificid species in a benthic community

FRESHWATER BIOLOGY, Issue 8 2009
L. C. STEINBACH ELWELL
Summary 1. Parasites can be important determinants of host community structure while host community structure can influence the success of parasites, although both are often overlooked. In two laboratory experiments, we examined interactions among Myxobolus cerebralis syn Myxosoma cerebralis Höfer, the myxozoan parasite that causes salmonid whirling disease, and two coexisting tubificid species: Tubifex tubifex (Müller), which is the alternate host of the parasite, and Limnodrilus hoffmeisteri Claparède, which is not susceptible. In the first experiment, we examined T. tubifex infection prevalence when exposed to nine doses of spores. In the second experiment, we examined tubificid and parasite success under three spore doses when tubificids were combined in a response surface experimental design used to detect interactions among species. 2. The outcomes of interactions between tubificid species were complex. The number and biomass of offspring of both tubificid species were density dependent when in monoculture or in combination with the other species. Adult growth of T. tubifex was also density dependent in monoculture, but when L. hoffmeisteri replaced one-half of the T. tubifex in the high-density treatment, adult growth of T. tubifex was higher than in monoculture. Adult growth of L. hoffmeisteri was always density independent. Whether T. tubifex was exposed to the parasite or not did not change the outcome of these interactions. However, adult growth of T. tubifex, but not L. hoffmeisteri, was highest when M. cerebralis was present. 3. Infection prevalence of T. tubifex increased with increasing spore dose. Infection prevalence was lowest in the high-density T. tubifex monoculture and highest in the low-density T. tubifex monoculture and when T. tubifex was in combination with L. hoffmeisteri. 4. Both intraspecific and interspecific competition influenced tubificid success, but T. tubifex gained some competitive advantage through increased adult growth when in combination with L. hoffmeisteri. Whether T. tubifex was exposed to the parasite or not did not change the outcome of the interactions between the tubificid species. 5. The presence of L. hoffmeisteri did not decrease the prevalence of infection in T. tubifex, suggesting that parasite success was unaltered by the presence of this non-susceptible species. [source]

Parasites can cause selection against migrants following dispersal between environments

FUNCTIONAL ECOLOGY, Issue 4 2010
Andrew D. C. MacColl
Summary 1.,The potential for selection against migrants to promote population divergence and speciation is well established in theory, yet there has been relatively little empirical work that has explicitly considered selection against migrants as a form of reproductive barrier, and its importance in the accumulation of reproductive isolation between populations has been overlooked until recently. 2.,Parasites often differ between environments and can be an important source of selection on hosts, yet their contribution to population divergence in general, and selection against migrants in particular, is poorly understood. 3.,Selection against migrants might be reduced if organisms escape parasitism when they disperse (natural enemy release). Alternatively, parasites could increase selection against migrants if, when they disperse, organisms encounter parasites to which they are poorly adapted. 4.,Here we test experimentally the contribution that parasites could make to selection against migrants in the adaptive radiation of three-spined sticklebacks. These fish have repeatedly colonized freshwater environments from marine ones, and this has repeatedly lead to rapid speciation. 5.,We use transplant experiments of lab-raised fish to simulate dispersal, and antihelminthic treatment to show that ancestral-type marine sticklebacks contract higher burdens of novel parasites when introduced to freshwater, than in saltwater, and suffer a growth cost as a direct result. 6.,Susceptibility to parasites and their detrimental effect is less in derived, freshwater fish from evolutionarily young populations, possibly as a result of selection for resistance. 7.,Our results support a role for parasites in selection against migrants and population diversification. They do not support the hypothesis of ,natural enemy release'. [source]

Parasites, testosterone and honest carotenoid-based signalling of health

FUNCTIONAL ECOLOGY, Issue 5 2007
F. MOUGEOT
Summary 1Among the commonest sexual signals of birds are the red-yellow traits pigmented by carotenoids, but how they reliably advertise individual quality remain poorly understood. Here we tested the hypothesis that carotenoid-based signalling is enhanced by testosterone but reduced by parasites, and that the dual action of testosterone on ornament expression and parasite resistance ensures reliable signalling. 2Tetraonid birds such as the red grouse Lagopus lagopus scoticus have bright red combs pigmented by carotenoids, which function in intra- and inter-sexual selection. In separate experiments, we manipulated a main nematode parasite, Trichostrongylus tenuis (using deparasitation and re-infection) and testosterone (using testosterone or combined Flutamide/ATD treatments) in free-living males and investigated effects on plasma carotenoids and comb colour. 3In untreated males, comb redness positively correlated with plasma carotenoids, testosterone concentration and condition. Plasma carotenoids and comb redness both negatively correlated with T. tenuis abundance. 4Plasma carotenoids decreased in response to a challenge from T. tenuis, but increased when parasites were reduced. Testosterone enhanced comb redness, but tended to deplete plasma carotenoids. Combined Flutamide and ATD treatment had no significant effects on comb colour or plasma carotenoids, indicating that testosterone effects might be direct. 5Our experiments show contrasted effects of testosterone and nematode parasites on carotenoid-based ornamentation. Testosterone and parasites have well documented interactions in the study model. These, together with the opposite effects that testosterone and parasites have on carotenoid availability and use, would shape optimal levels of signalling, depending on individual quality, and might ensure reliable signalling. 6Carotenoid-based and testosterone-dependent traits have rarely been linked. Our study provides such a connection and shows that investigating how parasites, testosterone and carotenoids interact helps in the understanding of the evolution and maintenance of honest carotenoid-based signals of health. [source]

Host,parasite interactions and vectors in the barn swallow in relation to climate change

GLOBAL CHANGE BIOLOGY, Issue 4 2010
A. P. MØLLER
Abstract Recent climate change has affected the phenology of numerous species, and such differential changes may affect host,parasite interactions. Using information on vectors (louseflies, mosquitoes, blackflies) and parasites (tropical fowl mite Ornithonyssus bursa, the lousefly Ornithomyia avicularia, a chewing louse Brueelia sp., two species of feather mites Trouessartia crucifera and Trouessartia appendiculata, and two species of blood parasites Leucozytozoon whitworthi and Haemoproteus prognei) of the barn swallow Hirundo rustica collected during 1971,2008, I analyzed temporal changes in emergence and abundance, relationships with climatic conditions, and changes in the fitness impact of parasites on their hosts. Temperature and rainfall during the summer breeding season of the host increased during the study. The intensity of infestation by mites decreased, but increased for the lousefly during 1982,2008. The prevalence of two species of blood parasites increased during 1988,2008. The timing of first mass emergence of mosquitoes and blackflies advanced. These temporal changes in phenology and abundance of parasites and vectors could be linked to changes in temperature, but less so to changes in precipitation. Parasites had fitness consequences for hosts because intensity of the mite and the chewing louse was significantly associated with delayed breeding of the host, while a greater abundance of feather mites was associated with earlier breeding. Reproductive success of the host decreased with increasing abundance of the chewing louse. The temporal decrease in mite abundance was associated with advanced breeding of the host, while the increase in abundance of the lousefly was associated with earlier breeding. Virulence by the tropical fowl mite decreased with increasing temperature, independent of confounding factors. These findings suggest that climate change affects parasite species differently, hence altering the composition of the parasite community, and that climate change causes changes in the virulence of parasites. Because the changing phenology of different species of parasites had both positive and negative effects on their hosts, and because the abundance of some parasites increased, while that of other decreased, there was no consistent temporal change in host fitness during 1971,2008. [source]