Parasite Pairs Research Articles

Micro-epidemiological structuring of Plasmodium falciparum parasite populations in regions with varying transmission intensities in Africa.

Background: The first models of malaria transmission assumed a completely mixed and homogeneous population of parasites. Recent models include spatial heterogeneity and variably mixed populations. However, there are few empiric estimates of parasite mixing with which to parametize such models. Methods: Here we genotype 276 single nucleotide polymorphisms (SNPs) in 5199 P. falciparum isolates from two Kenyan sites and one Gambian site to determine the spatio-temporal extent of parasite mixing, and use Principal Component Analysis (PCA) and linear regression to examine the relationship between genetic relatedness and relatedness in space and time for parasite pairs. Results: We show that there are no discrete geographically restricted parasite sub-populations, but instead we see a diffuse spatio-temporal structure to parasite genotypes. Genetic relatedness of sample pairs is predicted by relatedness in space and time. Conclusions: Our findings suggest that targeted malaria control will benefit the surrounding community, but unfortunately also that emerging drug resistance will spread rapidly through the population.

Genetic gradient of a host–parasite pair along a river persisted ten years against physical mobility: Baltic Salmo salar vs. Gyrodactylus salaris

The Atlantic salmon, Salmo salar L., in the Tornio River in the Northern Baltic Sea basin accommodates a monogenean ectoparasite, Gyrodactylus salaris. The aim of the study was to understand the population structure of apparently co-adapted host-parasite system: no parasite-associated mortality has been reported. The parasite burden among salmon juveniles (parr) was monitored along 460km of the river in 2000–2009. Among the parr, 33.0% were infected (nfish=1913). The genetic structure of the parasite population was studied by sequencing an anonymous nuclear DNA marker (ADNAM1, three main genotypes) and mitochondrial CO1 (three clades, six haplotypes). During the ten years, the parasite population was strongly and stably genetically differentiated among up- and downstream nurseries (nADNAM1=411, FST=0.579; nCO1=443, FST=0.534). Infection prevalence among the smolts migrating to sea was higher than in the sedentary parr populations (82.2%, nfish=129). The spatial differentiation observed among the sedentary juveniles was reflected temporally in the smolt run: parasite genotypes dominating the upper part of the river arrived later than downstream dwellers (medians June 4 and June 2) to the trap 7km from the river mouth. The nuclear and mitochondrial markers were in stable disequilibrium which was not relaxed in the contact zone or among the smolts where the parasite clones often met on individual fish. Only five parasite specimens on smolts (nworms=217) were putative recent sexual recombinants. The contribution of extant salmon hatcheries into the infection was negligible. The host salmon population in Tornio River is known to show significant spatial differentiation (FST=0.022). The stable spatial genetic structure of the parasite against the high physical mobility suggested a possibility of local co-adaptation of the host-parasite subpopulations.

“She’s got the ticket to ride, but she don’t care” (The Beatles, 1965) The epidemiology of Gyrodactylus salaris in the best wild salmon river in the Baltic Sea basin

Event Abstract Back to Event “She’s got the ticket to ride, but she don’t care” (The Beatles, 1965) The epidemiology of Gyrodactylus salaris in the best wild salmon river in the Baltic Sea basin Perttu Koski1* and Jaakko Lumme2 1 Finnish Food Safety Authority Evira, Finland 2 University of Oulu, Department of Biology, Finland Tornionjoki river system is nowadays the most productive wild salmon river in the Baltic Sea water catchment area. We followed the subclinical Gyrodactylus salaris infection of salmon parr at four indicator areas during 2000-2012 (number of fish, nfish=2571). The uppermost tributary, River Lätäseno (460 km from the river mouth), had the highest mean apparent prevalence (47.4%) and the lowest part, R. Tornionjoki along the Finnish-Swedish border, the lowest (11.0%). The infection was more common in two summer old and older (mean 31.1%) than in the parr of the first summer (mean 10.1%). The associations of the watercourse sections and the age of the parr with the infection were clear in binary logistic regression. Adjusted odds ratio was 6.7 in R. Lätäseno, 2.4 in R. Könkämäeno and 1.9 in R. Muonionjoki in comparison with R. Tornionjoki. Possible water quality determinants (e.g. high aqueous aluminum concentrations) behind this upside-down pattern need further research. The genetic structure of the parasite population was studied by sequencing an anonymous nuclear DNA marker (ADNAM1, three main genotypes) and mitochondrial CO1 (three clades, six haplotypes). During the ten years 2000-2009, the parasite population was strongly and stably genetically differentiated among up- and downstream nurseries (nADNAM1 = 411, fixation index based on genotype/haplotype frequencies, FST = 0.579; nCO1 = 443, FST = 0.534). The nuclear and mitochondrial markers were in stable disequilibrium which was not relaxed in the contact zone or among the smolt where the parasite clones often met on individual fish. The host salmon population in Tornio River is known to show significant spatial differentiation (FST = 0.022). The stable spatial genetic structure of the parasite against the high physical mobility suggested a possibility of local co-adaptation of the host-parasite subpopulations. Acknowledgements Several other researches in addition to the authors of the references participated in the monitoring or molecular biology work of Gyrodactylus: Ville Vähä and Kari Pulkkinen, Natural Resources Institute Finland (LUKE), Petra Heikkinen and Liisa Alaoutinen, Evira and Laura Törmänen, University of Oulu. References Anttila, P., Romakkaniemi, A., Kuusela, J., Koski, P.. 2008. Epidemiology of Gyrodactylus salaris (Monogenea) in the River Tornionjoki, a Baltic wild salmon river. Journal of Fish Diseases 31, 373-382. Lumme, J., Anttila, P., Rintamäki, P., Koski, P., Romakkaniemi, A.. 2016. Genetic gradient of a host – parasite pair along a river persisted ten years against physical mobility: Baltic Salmo salar vs. Gyrodactylus salaris. Infection, Genetics and Evolution 45, 33-39. Keywords: Gyrodactylus salaris, Salmo salar, Epidemiology, Prevalence, Parasite dispersal, Baltic Sea, local adaptation Conference: AquaEpi I - 2016, Oslo, Norway, 20 Sep - 22 Sep, 2016. Presentation Type: Poster Topic: Aquatic Animal Epidemiology Citation: Koski P and Lumme J (2016). “She’s got the ticket to ride, but she don’t care” (The Beatles, 1965) The epidemiology of Gyrodactylus salaris in the best wild salmon river in the Baltic Sea basin. Front. Vet. Sci. Conference Abstract: AquaEpi I - 2016. doi: 10.3389/conf.FVETS.2016.02.00007 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 05 Sep 2016; Published Online: 14 Sep 2016. * Correspondence: PhD. Perttu Koski, Finnish Food Safety Authority Evira, Oulu, Finland, perttu.koski@evira.fi Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Perttu Koski Jaakko Lumme Google Perttu Koski Jaakko Lumme Google Scholar Perttu Koski Jaakko Lumme PubMed Perttu Koski Jaakko Lumme Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Mating isolation between the ant Myrmica rubra and its microgynous social parasite

Sympatric speciation has been suggested for several pairs of social parasites and their hosts. Little is known, however, about how they have become reproductively isolated from each other. The ant Myrmica rubra has an intraspecific microgynous social parasite, which is probably speciating from its macrogynous host morph. Mating of the host and parasite is suggested to be spatially isolated, microgynes mating in the nest and macrogynes usually joining mating swarms. The mating biology of the microgyne is, however, still poorly known. We studied mating isolation and potential gene flow between these morphs by assessing whether host males are produced in naturally parasitized nests, and by testing experimentally cross-mating of the morphs when brought together. Both parasite and host males mated with both female morphs, but host males seemed to mate more often than the parasite males with their own kind. Although most males in the parasitized nests were produced by the parasites, the host queens and workers also produced some males, thus providing the morphs an opportunity for cross-mating. Previous studies have shown, however, that genetic divergence between sympatric parasite and host populations is substantial, which indicates that hybridization is rare. This implies that even if cross-mating between the morphs took place in the wild, introgression would be weak. Our results, together with earlier studies, indicate that the parasite and host of M. rubra are not fully reproductively isolated, even though gene flow between the morphs is restricted enough to allow ongoing speciation of the parasite.

Genetic divergence between the sympatric queen morphs of the ant Myrmica rubra.

Pairs of obligate social parasites and their hosts, where some of the parasites have recently diverged from their host through intraspecific social parasitism, provide intriguing systems for studying the modes and processes of speciation. Such speciation, probably in sympatry, has also been propounded in the ant Myrmica rubra and its intraspecific social parasite. In this species, parasitism is associated with queen size dimorphism, and the small microgyne has become a social parasite of the large macrogyne. Here, we investigated the genetic divergence of the host and the parasite queen morphs in 11 localities in southern Finland, using nuclear and mitochondrial markers of queens and workers. We formulated and tested four speciation-related hypotheses that differed in the degree of genetic divergence between the morphs. The queen morphs were genetically distinct from each other with little hybridization. In the nuclear data, when localities were nested within queen morphs in the hierarchical amova, 39% of the genetic variation was explained by the queen morph (standardized F'CT = 0.63, uncorrected FCT = 0.39), whereas 18% was explained by the locality (F'SC = 0.39, FSC = 0.29). This result corroborated the hypothesis of advanced sympatric speciation. In contrast, the mitochondrial DNA could not settle between the hierarchical levels of locality and queen morph, thus substantiating equally the hypotheses of incipient and advanced sympatric speciation. Together, our results support the view that the microgynous parasite has genetically diverged from its macrogynous host to the level of a nascent species.

Genome-wide polymorphisms and development of a microarray platform to detect genetic variations in Plasmodium yoelii

The rodent malaria parasite Plasmodium yoelii is an important model for studying malaria immunity and pathogenesis. One approach for studying malaria disease phenotypes is genetic mapping, which requires typing a large number of genetic markers from multiple parasite strains and/or progeny from genetic crosses. Hundreds of microsatellite (MS) markers have been developed to genotype the P. yoelii genome; however, typing a large number of MS markers can be labor intensive, time consuming, and expensive. Thus, development of high-throughput genotyping tools such as DNA microarrays that enable rapid and accurate large-scale genotyping of the malaria parasite will be highly desirable. In this study, we sequenced the genomes of two P. yoelii strains (33X and N67) and obtained a large number of single nucleotide polymorphisms (SNPs). Based on the SNPs obtained, we designed sets of oligonucleotide probes to develop a microarray that could interrogate ∼11,000 SNPs across the 14 chromosomes of the parasite in a single hybridization. Results from hybridizations of DNA samples of five P. yoelii strains or cloned lines (17XNL, YM, 33X, N67 and N67C) and two progeny from a genetic cross (N67×17XNL) to the microarray showed that the array had a high call rate (∼97%) and accuracy (99.9%) in calling SNPs, providing a simple and reliable tool for typing the P. yoelii genome. Our data show that the P. yoelii genome is highly polymorphic, although isogenic pairs of parasites were also detected. Additionally, our results indicate that the 33X parasite is a progeny of 17XNL (or YM) and an unknown parasite. The highly accurate and reliable microarray developed in this study will greatly facilitate our ability to study the genetic basis of important traits and the disease it causes.

A Passive RFID Tag Embedded Temperature Sensor With Improved Process Spreads Immunity for a $-{\hbox {30}}^{\circ}{\hbox {C}}$ to 60$^{\circ}{\hbox {C}}$ Sensing Range

We present an ultra-low power temperature sensor embedded in the passive RFID tag using the TSMC 1P6M 0.18 μm standard CMOS process. Substrate parasitic NPN bipolar pair is exploited to generate the temperature dependent current signals for thermal sensing. A time-domain readout scheme which has high immunity to the on-chip resistor, capacitor and clock frequency process-voltage-temperature (PVT) spreads is further proposed. Measurement results of the embedded sensor within the tag system shows a sensing accuracy of ±1.5 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C (3σ) from -30 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C to 60 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C after one-point calibration at 20 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C, with a sensing resolution of 0.3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C and a sampling rate of 68 samples per second. The embedded sensor draws 0.35 μA from a 1 V supply at room temperature and occupies a chip area of 0.14 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Excretory products of the cestode, Schistocephalus solidus, modulate in vitro responses of leukocytes from its specific host, the three-spined stickleback (Gasterosteus aculeatus)

Helminth parasites have evolved remarkable strategies to manipulate the immune system of their hosts. During infections of three-spined stickleback (Gasterosteus aculeatus) with the cestode Schistocephalus solidus prominent immunological changes occur, presumably due to manipulative activity of the parasite. We hypothesise that excretory/secretory products of the parasite are involved in the manipulation of the stickleback's immune system and that this may depend on the individual parasite and its origin. We therefore produced S. solidus conditioned cell culture media (SSCM) with parasites from different origins (Norway, Spain and Germany) and exposed head kidney leukocytes (HKL) from un-infected sticklebacks in cell cultures to SSCM. After in vitro culture, HKL were subjected to differential cell counts (granulocytes/lymphocytes) by means of flow cytometry. Leukocyte sub-populations were analysed for cell viability and changes in cell morphology. The respiratory burst activity was measured with a luminescence assay. Exposure of HKL to SSCM induced an up-regulation of respiratory burst activity after already 1 h, which was still elevated at 24 h, but which was in some cases significantly down-regulated after 96 h. Respiratory burst was positively correlated with the number of live granulocytes in the culture, suggesting that the respiratory burst activity was changed by SSCM effects on granulocyte viability. After 1 h and 24 h of HKL culture, no lymphocyte responses to SSCM were detectable, but after 96 h lymphocyte viability was significantly decreased with SSCM from Spanish S. solidus. In these cultures, residual lymphocytes increased in size, suggesting that cell death and activation might have occurred in parallel. The highest respiratory burst activity was induced by SSCM from Spanish parasites, in particular when they were grown in sympatric sticklebacks. The in vitro HKL responses to SSCM depended on the individual parasite and its population of origin, suggesting that in vivo, S. solidus excretory products are regulated individually, possibly to balance the interplay of each individual host–parasite pair.

A Coupled Hidden Markov Model for Disease Interactions

To investigate interactions between parasite species in a host, a population of field voles was studied longitudinally, with presence or absence of six different parasites measured repeatedly. Although trapping sessions were regular, a different set of voles was caught at each session, leading to incomplete profiles for all subjects. We use a discrete time hidden Markov model for each disease with transition probabilities dependent on covariates via a set of logistic regressions. For each disease the hidden states for each of the other diseases at a given time point form part of the covariate set for the Markov transition probabilities from that time point. This allows us to gauge the influence of each parasite species on the transition probabilities for each of the other parasite species. Inference is performed via a Gibbs sampler, which cycles through each of the diseases, first using an adaptive Metropolis–Hastings step to sample from the conditional posterior of the covariate parameters for that particular disease given the hidden states for all other diseases and then sampling from the hidden states for that disease given the parameters. We find evidence for interactions between several pairs of parasites and of an acquired immune response for two of the parasites.

BROADBAND SERIES-FED DIPOLE PAIR ANTENNA WITH PARASITIC STRIP PAIR DIRECTOR

A method to increase the bandwidth of a series-fed dipole pair (SDP) antenna by using a parasitic strip pair director is presented in this paper. A conventional SDP antenna consists of two dipole elements having difierent lengths and a ground re∞ector, which are serially connected with a transmission line. In the proposed antenna, a parasitic strip pair director is appended to the conventional SDP antenna. Initially, a conventional SDP antenna that operates in a frequency range of 1.7{2.7GHz is designed by optimizing the lengths of the elements (two dipoles and ground re∞ector) and the distances between these elements. Subsequently, a parasitic director containing a pair of strips is placed near the top dipole element to improve the bandwidth and gain of the conventional SDP antenna. Then, the efiects of the location and size of the director on the impedance bandwidth and realized gain are investigated. A prototype of the proposed antenna is fabricated on an FR4 substrate, and its performance is compared with that of the conventional SDP antenna. The experimental results show that the proposed antenna has an enhanced bandwidth of 1.63{2.97GHz (58.26%) and an increased gain of 5.6{6.8dBi.

HepatozoonParasites (Apicomplexa: Adeleorina) in Bats

We provide the first evidence of Hepatozoon parasites infecting bats. We sequenced a short fragment of the 18S rRNA gene (~600 base pairs) of Hepatozoon parasites from 3 Hipposideros cervinus bats from Borneo. Phylogenies inferred by model-based methods place these Hepatozoon within a clade formed by parasites of reptiles, rodents, and marsupials. We discuss the scenario that bats might be common hosts of Hepatozoon.

Seroprevalence of Trypanosoma cruzi in immigrant women living in Basque Country, Spain

Toxoplasma gondii RH tachyzoites replicated in VERO cell cultures. A rosette of many tachyzoites is shown at left and several parasite pairs at right (arrows) Results: In both cell types invasion with either strain increased along time; however, proportion of infected cells was lower for HUVECs than for HMEC-1. Also, the strains differed in invasion kinetics: ME49 parasites were faster than RH ones, regardless of cell type. Finally, both HMEC-1 and HUVECs showed higher numberofparasitic vacuolesper cellwhen infectedbyME49 tazhyzoites than by RH protozoan, i.e ≈30 vs ≈20 at 4 hours, respectively. Conclusion:Results suggest thatHMEC-1 cells aremore susceptible to infection by T. gondii than HUVECs. This might be related to cell cycle-progress -which is usually badly regulated in cell linesand T. gondii is more invasive during the G1-S phase. The unexpected observation that RH parasites are slower than ME49 ones might be related to their higher ability to survive out of the cell.

Prevalence of Mammomonogamus laryngeus(Strongylida:Syngamidae) nematodes in a bovine slaughterhouse

Mammomonogamus laryngeus is a nematode parasite that is usually found in the larynx of mammals in the tropics, especially in cattle, sheep and cats. The prevalence of M. laryngeus was determined in cattle brought to an abattoir as an indicator of its prevalence in the general population. Materials and methods. The present study was undertaken in the municipality of La Tebaida, Quindio, Colombia, to determine the presence of M. laryngeus infection in cattle brought to a local abattoir between December and February 2009. The tracheae and lungs of 500 slaughtered cattle were examined. Parasite prevalence was 14.8% (n=74). The majority of worms were located on aryteno-epiglottic folds, but never in the tracheae or bronchi. The infection rate was highest (47%) in 2 to 2.5 year old animals. In infected animals, an average of 6.4 parasite pairs was found, with higher numbers in older animals. The prevalence of infection in cattle was greater than seen in the provinces of Valle del Cauca (10.0%), Quindío(3,0%) pr Caquetá (1.2%). Reports of this parasite in cattle indicate its circulation throughout Colombia and recommend surveillance studies where cattle are raised and prepared for human consumption.

Prevalencia de Mammomonogamus laryngeus (Strongylida: Syngamidae) en ganado bovino de la central de beneficio del municipio de La Tebaida, Quindío, Colombia

Introduction. Mammomonogamus laryngeus is a nematode parasite that is usually found in the larynx of mammals in the tropics, especially in cattle, sheep and cats.Objective. The prevalence of M. laryngeus was determined in cattle brought to an abattoir as an indicator of its prevalence in the general population.Materials and methods. The present study was undertaken in the municipality of La Tebaida, Quindio, Colombia, to determine the presence of M. laryngeus infection in cattle brought to a local abattoir between December and February 2009. The tracheae and lungs of 500 slaughtered cattle were examined.Results. Parasite prevalence was 14.8% (n=74). The majority of worms were located on aryteno-epiglottic folds, but never in the tracheae or bronchi. The infection rate was highest (47%) in 2 to 2.5 year old animals. In infected animals, an average of 6.4 parasite pairs was found, with higher numbers in older animals. The prevalence of infection in cattle was greater than seen in the provinces of Valle del Cauca (10.0%), Quindío(3,0%) pr Caquetá (1.2%).Conclusions. Reports of this parasite in cattle indicate its circulation throughout Colombia and recommend surveillance studies where cattle are raised and prepared for human consumption.

Changes in Secondary Sexual Characters of Males of Thor Floridanus (Decapoda, Hippolytidae), Infested by Bopyrinella Thorii (Isopoda, Bopyridae)

Abstract This study describes changes in the secondary sexual characters of Thor floridanus Kingsley, 1878 males, caused by the isopod Bopyrinella thorii (Richardson, 1904). Of 380 specimens of T. floridanus examined, the females were more often infested (n = 313) than the males (n = 41), and had a wider size range (0.7-2.85 mm POCL) compared to the males (0.9-2.32 mm POCL); no ovigerous females of T. floridanus were found. In 25 males the appendix masculina was reduced in size, the endopod of the second pleopod was barely ornamented, and the flexor margin of the propod of the third pereiopod was similar to that of the female of the species; all those males were classified as “feminized”. Those individuals were infested mainly by pairs of mature parasites, and 75% of the “primary” males carried cryptoniscus larvae, suggesting that the “feminization” of the males is caused by the parasite, as a result of the sexual development of hosts and parasites.

Host density drives the postglacial migration of the tree parasite, Epifagus virginiana

To survive changes in climate, successful species shift their geographic ranges to remain in suitable habitats. For parasites and other highly specialized species, distributional changes not only are dictated by climate but can also be engineered by their hosts. The extent of host control on parasite range expansion is revealed through comparisons of host and parasite migration and demographic histories. However, understanding the codistributional history of entire forest communities is complicated by challenges in synthesizing datasets from multiple interacting species of differing datatypes. Here we integrate genetic and fossil pollen datasets from a host-parasite pair; specifically, the population structure of the parasitic plant (Epifagus virginiana) was compared with both its host (Fagus grandifolia) genetic patterns and abundance data from the paleopollen record of the last 21,000 y. Through tests of phylogeographic structure and spatial linear regression models we find, surprisingly, host range changes had little effect on the parasite's range expansion and instead host density is the main driver of parasite spread. Unlike other symbionts that have been used as proxies to track their host's movements, this parasite's migration routes are incongruent with the host and instead reflect the greater importance of host density in this community's assembly. Furthermore, these results confirm predictions of disease ecological models regarding the role of host density in the spread of pathogens. Due to host density constraints, highly specialized species may have low migration capacities and long lag times before colonization of new areas.

Intra‐specific body size variation inPolistespaper wasps as a response to social parasite pressure

1. Like avian brood parasites, obligate insect social parasites exploit the parental care of a host species to rear their brood, causing an evident loss of host reproductive success. This fitness cost imposes selective pressure on the host to reduce the parasite effect. A possible outcome of an evolutionary arms race is the selection of host morphological counter‐adaptations to resist parasite attacks.2. We studied host–parasite pairs ofPolisteswasps in which the fighting equipment of the parasite's body allows it to enter the host colony.3. We searched for host morphological traits related to fighting ability that could be considered counter‐adaptations. As a host–parasite co‐evolutionary arms race can only occur where the two lineages co‐exist, we compared morphological traits of hosts belonging to populations with or without parasite pressure. We report that host foundresses belonging to populations under strong parasite pressure have a larger body size than those belonging to populations without parasite pressure.4. Behavioural experiments carried out to test if an increase in host body size is useful to oppose parasite usurpation show that large body size foundresses exhibit a greater ability of nest defence.

Temporal, spatial and between-host comparisons of patterns of parasitism in lake zooplankton

In nature, multiple parasite species infect multiple host species and are influenced by processes operating across different spatial and temporal scales. Data sets incorporating these complexities offer exciting opportunities to examine factors that shape epidemics. We present a method using generalized linear mixed models in a multilevel modeling framework to analyze patterns of variances and correlations in binomially distributed prevalence data. We then apply it to a multi-lake, multiyear data set involving two Daphnia host species and nine microparasite species. We found that the largest source of variation in parasite prevalence was the species identities of host–parasite pairs, indicating strong host–parasite specificity. Within host–parasite combinations, spatial variation (among lakes) exceeded interannual variation. This suggests that factors promoting differences among lakes (e.g., habitat characteristics and species interactions) better explain variation in peak infection prevalence in our data set than factors driving differences among years (e.g., climate). Prevalences of parasites in D. dentifera were more positively correlated than those for D. pulicaria, suggesting that similar factors influenced epidemic size among parasites in D. dentifera. Overall, this study demonstrates a method for parsing patterns of variation and covariation in infection prevalence data, providing greater insight into the relative importance of different underlying drivers of parasitism.

A new ovine Babesia species transmitted by Hyalomma anatolicum anatolicum

The pathogenicity and morphology of a large Babesia species, Babesia sp. Xinjiang, are described here. The parasite has very low virulence for sheep, and caused no detectable clinical symptoms. Splenectomized sheep infected with the parasite showed mild fever and low parasitemia and would recover gradually. If splenectomized sheep were immuno-suppressed with dexamethasone, the parasitemia could reach 8.5%, and death occurred. A splenectomized calf could not be infected with the Babesia species. Paired parasites were the typical form of the Babesia species in erythrocytes and the average size of a pair of parasites was 2.42 (±0.35) μm × 1.06 (±0.22) μm. Merozoites were found in the gut, salivary gland, haemolymph, ovary and eggs of female Hyalomma anatolicum anatolicum engorged on sheep infected with the parasites. The results of experimental transmission showed that the larval, nymph and adult stages of H. a. anatolicum could transmit the Babesia species to sheep.

Coevolution of daily activity timing in a host-parasite system

Coevolutionary theories applied in the study of host–parasite systems indicate that lineages exhibit progressive trends in response to reciprocal selective pressures. Avian brood parasites have generated intense interest as models for coevolutionary processes. Similar to avian cuckoos, Polistes wasp social parasites usurp a nest and exploit the parental care of a congeneric species to rear their own brood. In the present study, we show a coevolutionary arms race in the daily activity pattern in a Polistes host–parasite pair. We measured the daily activity rate, in constant laboratory conditions, of both host and parasite females during the period in which nest usurpations occur. The parasites showed a hyperkinesis in the middle of the day. As the field observations suggested, this mid-day activity is used to perform host nest usurpation attempts. Timing the usurpations allows the parasite to maximize its usurpation attempts during daytime when the host defence is lower. A field comparison of host presence on the nest in two populations with different parasitism rates showed that populations under strong parasitic pressure exhibit timing counteradaptations to optimize nest defence. This study provides the first example of a mutual coadaptation in timing activity in a parasite–host system. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 399–405.