Parasite's Cycle Research Articles

An Aromatic Diamidine That Targets Kinetoplast DNA, Impairs the Cell Cycle in Trypanosoma cruzi, and Diminishes Trypomastigote Release from Infected Mammalian Host Cells.

Trypanosoma cruzi is the etiological agent of Chagas disease, affecting approximately 10 million people in the Americas and with some 40 million people at risk. The objective of this study was to evaluate the anti-T. cruzi activity of three new diamidines that have a 3,4-ethylenedioxy extension of the thiophene core, designated MB17, MB19, and MB38. All three diamidines exhibited dose-dependent inhibition of epimastigote replication. The mechanisms of action of these diamidines were investigated. Unlike MB17 and MB19, MB38 exhibited a significant increase in the number of annexin-propidium iodide double-labeled cells compared to levels in control parasites. As MB17 had shown a lower 50% inhibitory concentration (IC50) against epimastigote growth, the mechanism of action of this drug was studied in more detail. MB17 triggered a decrease in the intracellular ATP levels. As a consequence, MB17 affected the genomic DNA and kinetoplast DNA (kDNA) and impaired the parasite cell cycle. Moreover, MB17 caused DNA fragmentation, with a more severe effect on kDNA than on nuclear DNA, resulting in dyskinetoplastic cells. MB17 was tested for toxicity and effectiveness for the treatment of infected CHO-K1 cells, exhibiting a 50% cytotoxic concentration (CC50) of 13.47 ± 0.37 μM and an IC50 of 0.14 ± 0.12 μM against trypomastigote release. MB17 also diminished the infection index by 60% at 0.5 μM. In conclusion, despite belonging to the same family, these diamidines have different efficiencies. To summarize, MB17 was the most potent of these diamidines against epimastigotes, producing DNA damage preferentially in kDNA, impairing the parasite cell cycle, and decreasing the infection index and trypomastigote release from infected mammalian host cells, with a high selectivity index (SI) (<90). These data suggest that MB17 could be an interesting lead compound against T. cruzi.

Evaluation of the enzyme activity of protozoan protein kinases by using an in vitro kinase assay

The life cycles of parasites are more complicated than those of other biological species. Protein kinases (PKs) encoded by parasites are the main triggers of life stage conversions. Phosphorylation by cellular PKs regulates important cellular processes, and the protozoan genome contains many PKs. Some PK inhibitors inhibit specific parasite life cycle event. In this report, I present a practical approach to expressing and purifying protozoan PKs by using a wheat germ cell-free protein synthesis system and I assess the phosphorylation activities of protozoan PKs by using an in vitro kinase assay.

Molecular detection of Sarcocystis aucheniae in the blood of llamas from Argentina

Sarcocystis aucheniae are apicomplexan protozoa that infect South American camelids (SACs), giving rise to macroscopic cysts similar to rice grains in skeletal muscles. Visual detection of macrocysts in slaughtered animals hampers commercialization of SAC meat, a highly relevant economic exploitation for Andean rural families. Importantly, the consumption of undercooked S. aucheniae-infested meat causes gastroenteritis. A carnivore definitive host, possibly the dog, acquires the parasite when feeding on infected SAC meat, and later eliminates infective oocysts in its feces. The parasite cycle is completed when SACs ingest contaminated water or pastures. We hypothesized that parasite DNA can be detected in SAC blood using molecular methods. In order to test this hypothesis, a seminested PCR format was specifically designed to target the hypervariable 18S rRNA gene region of S. aucheniae. PCR conditions were optimized using genomic DNA extracted from macrocyst bradyzoites. A detection limit of up to 1 parasite in 10μl of llama blood was established based on DNA samples extracted from aliquots of S. aucheniae bradyzoite-spiked non-infected llama blood. The seminested PCR allowed to detect natural infections of S. aucheniae in llama blood samples originating in the Andean flatlands of Argentina. Specific amplification of S. aucheniae DNA was corroborated by amplicon sequencing. This is the first report of S. aucheniae detection in llama blood, which provides a valuable diagnostic tool for epidemiological studies and for the evaluation of the efficacy of control measures for this parasitosis.

Predicting optimal transmission investment in malaria parasites.

In vertebrate hosts, malaria parasites face a tradeoff between replicating and the production of transmission stages that can be passed onto mosquitoes. This tradeoff is analogous to growth-reproduction tradeoffs in multicellular organisms. We use a mathematical model tailored to the life cycle and dynamics of malaria parasites to identify allocation strategies that maximize cumulative transmission potential to mosquitoes. We show that plastic strategies can substantially outperform fixed allocation because parasites can achieve greater fitness by investing in proliferation early and delaying the production of transmission stages. Parasites should further benefit from restraining transmission investment later in infection, because such a strategy can help maintain parasite numbers in the face of resource depletion. Early allocation decisions are predicted to have the greatest impact on parasite fitness. If the immune response saturates as parasite numbers increase, parasites should benefit from even longer delays prior to transmission investment. The presence of a competing strain selects for consistently lower levels of transmission investment and dramatically increased exploitation of the red blood cell resource. While we provide a detailed analysis of tradeoffs pertaining to malaria life history, our approach for identifying optimal plastic allocation strategies may be broadly applicable.

DIVERSIDADE, PREVALÊNCIA E INFECÇÃO NATURAL POR TRIPANOSSOMATÍDEOS EM TRIATOMÍNEOS (HEMIPTERA: REDUVIIDAE) DO CURIMATAÚ E SERIDÓ PARAIBANOS

Os triatomíneos (Hemiptera: Reduviidae) são insetos hematófagos vetores do Trypanosoma cruzi, agente etiológico da doença de Chagas humana. Neste trabalho, objetivou-se avaliar a fauna de triatomíneos capturados em municípios da região do Curimataú e Seridó paraibanos, durante a Campanha do Programa de Controle da Doença de Chagas (PCDCh) em 2013, e fazer um levantamento retrospectivo das espécies capturadas entre 2008 e 2012 na mesma região. Foram realizadas coleta, identificação taxonômica e análise parasitológica das fezes de triatomíneos coletados em pesquisa de campo no ano de 2013. Além disso, analisaramse documentos de registro dos exames realizados nos triatomíneos durante as campanhas do PCDCh, nos anos de 2008 a 2012, arquivados na 4ª Gerência Regional de Saúde. Os indicadores entomológicos analisados foram os seguintes: Índice de colonização (IC), Infestação domiciliar (ID), Densidade triatomínica domiciliar (DTD) e Índice de infecção (II). No período estudado (2008-2012), foram capturados 1.896 exemplares de triatomíneos na região, constatando-se a presença de sete espécies de triatomíneos: Panstrongylus lutzi, P. megistus, Rhodnius nasutus, R. neglectus, Triatoma brasiliensis, T. melanocephala e T. pseudomaculata. Ficaram demonstradas a distribuição geográfica dos triatomíneos nos municípios estudados e a prevalência por ano de estudo. Foram observadas associações significativas (p &lt; 0,05) entre o estádio de desenvolvimento de T. brasilensis e T. pseudomaculata e o local de captura, respectivamente, intradomicílio e peridomicílio. No ano de 2013, os índices verificados foram IC - 41,6%, ID - 13%, DTD - 0,3% e II - 0,7%; para os espécimes examinados entre 2008 e 2012, o índice foi de 0,1%. Os índices entomológicos mostram a colonização intra e peridomiciliar dos vetores e sugerem que o ciclo do parasito permanece ativo na região.

Vital and dispensable roles of Plasmodium multidrug resistance transporters during blood- and mosquito-stage development.

Multidrug resistance (MDR) proteins belong to the B subfamily of the ATP Binding Cassette (ABC) transporters, which export a wide range of compounds including pharmaceuticals. In this study, we used reverse genetics to study the role of all seven Plasmodium MDR proteins during the life cycle of malaria parasites. Four P. berghei genes (encoding MDR1, 4, 6 and 7) were refractory to deletion, indicating a vital role during blood stage multiplication and validating them as potential targets for antimalarial drugs. Mutants lacking expression of MDR2, MDR3 and MDR5 were generated in both P. berghei and P. falciparum, indicating a dispensable role for blood stage development. Whereas P. berghei mutants lacking MDR3 and MDR5 had a reduced blood stage multiplication in vivo, blood stage growth of P. falciparum mutants in vitro was not significantly different. Oocyst maturation and sporozoite formation in Plasmodium mutants lacking MDR2 or MDR5 was reduced. Sporozoites of these P. berghei mutants were capable of infecting mice and life cycle completion, indicating the absence of vital roles during liver stage development. Our results demonstrate vital and dispensable roles of MDR proteins during blood stages and an important function in sporogony for MDR2 and MDR5 in both Plasmodium species.

Analysis of the Approach to Parasitic Cycles in Brazilian Science Textbooks as a Tool for Education in Health and Environment

Analysis of the Approach to Parasitic Cycles in Brazilian Science Textbooks as a Tool for Education in Health and Environment

Impact of the Phoretic Phase on Reproduction and Damage Caused by Varroa destructor (Anderson and Trueman) to Its Host, the European Honey Bee (Apis mellifera L.).

Varroa destructor is a parasitic mite of the honeybee that causes thousands of colony losses worldwide. The parasite cycle is composed of a phoretic and a reproductive phase. During the former, mites stay on adult bees, mostly on nurses, to feed on hemolymph. During the latter, the parasites enter brood cells and reproduce. We investigated if the type of bees on which Varroa stays during the phoretic phase and if the duration of this stay influenced the reproductive success of the parasite and the damage caused to bees. For that purpose, we used an in vitro rearing method developed in our laboratory to assess egg laying rate and the presence and number of fully molted daughters. The expression level of two Varroa vitellogenin genes (VdVg1 and VdVg2), known to vary throughout reproduction, was also quantified. Results showed that the status of the bees or time spent during the phoretic phase impacts neither reproduction parameters nor the Varroa vitellogenin genes levels of expression. However, we correlated these parameters to the gene expression and demonstrated that daughters expressed the vitellogenin genes at lower levels than their mother. Regarding the damage to bees, the data indicated that a longer stay on adult bees during the phoretic phase resulted in more frequent physical deformity in newborn bees. We showed that those mites carry more viral loads of the Deformed Wing Virus and hence trigger more frequently overt infections. This study provides new perspectives towards a better understanding of the Varroa-honeybee interactions.

Tetractinomyxon stages genetically consistent with Sphaerospora dicentrarchi (Myxozoa: Sphaerosporidae) found in Capitella sp. (Polychaeta: Capitellidae) suggest potential role of marine polychaetes in parasite's life cycle.

Known life cycles of myxosporean parasites have two hosts, but very few life cycles have been disclosed, especially in the marine environment. Sphaerospora dicentrarchi Sitjà-Bobadilla and Álvarez-Pellitero, 1992 is a systemic parasite from the European seabass, Dicentrarchus labrax (Linnaeus, 1758), a highly valuable commercial fish. It affects its health, leading to aquaculture production losses. During 2013 and 2014, an actinospore survey was conducted in a total of 5942 annelids collected from a fish farm in Algarve and from the Aveiro Estuary, in Portugal. A new tetractinomyxon actinospore was found in a capitellid polychaete, belonging to the genera Capitella collected at the fish farm. The tetractinomyxons were pyriform measuring 11·1 ± 0·7 µm in length and 7·2 ± 0·4 µm in width, and presented three rounded polar capsules measuring 2·4 ± 0·3 µm in diameter. The molecular analysis of the 18S rRNA gene sequences from the tetractinomyxons revealed a similarity of 100% with the DNA sequences deposited in the GenBank from S. dicentrarchi myxospores collected from the European seabass and the spotted seabass in the same fish farm and 99·9% similarity with the DNA sequence obtained from the myxospores found infecting the European seabass in the Aveiro Estuary. Therefore, the new tetractinomyxons are inferred to represent the actinospore phase of the S. dicentrarchi life cycle.

Using a Genetically Encoded Sensor to Identify Inhibitors of Toxoplasma gondii Ca2+ Signaling

The life cycles of apicomplexan parasites progress in accordance with fluxes in cytosolic Ca2+. Such fluxes are necessary for events like motility and egress from host cells. We used genetically encoded Ca2+ indicators (GCaMPs) to develop a cell-based phenotypic screen for compounds that modulate Ca2+ signaling in the model apicomplexan Toxoplasma gondii. In doing so, we took advantage of the phosphodiesterase inhibitor zaprinast, which we show acts in part through cGMP-dependent protein kinase (protein kinase G; PKG) to raise levels of cytosolic Ca2+. We define the pool of Ca2+ regulated by PKG to be a neutral store distinct from the endoplasmic reticulum. Screening a library of 823 ATP mimetics, we identify both inhibitors and enhancers of Ca2+ signaling. Two such compounds constitute novel PKG inhibitors and prevent zaprinast from increasing cytosolic Ca2+. The enhancers identified are capable of releasing intracellular Ca2+ stores independently of zaprinast or PKG. One of these enhancers blocks parasite egress and invasion and shows strong antiparasitic activity against T. gondii. The same compound inhibits invasion of the most lethal malaria parasite, Plasmodium falciparum. Inhibition of Ca2+-related phenotypes in these two apicomplexan parasites suggests that depletion of intracellular Ca2+ stores by the enhancer may be an effective antiparasitic strategy. These results establish a powerful new strategy for identifying compounds that modulate the essential parasite signaling pathways regulated by Ca2+, underscoring the importance of these pathways and the therapeutic potential of their inhibition.

Identification of Hepatozoon erhardovae Krampitz, 1964 from bank voles (Myodes glareolus) and fleas in Southern Hungary.

In order to investigate the prevalence and life cycle of apicomplexan parasites, small mammals were live-trapped with modified Sherman traps in Southern Hungary between 2010 and 2012. Altogether, 528 rodents (Apodemus flavicollis Melchior, 1834, Apodemus agrarius Pallas, 1771, Myodes glareolus Schreber, 1780, Microtus agrestis Linnaeus, 1761, Mus musculus Linnaeus, 1758 and Micromys minutus Pallas, 1771) were collected and four shrews (Sorex spp.) were by-catched. Captured animals belonging to non-protected species were euthanized, and spleen samples were preserved for histological and molecular analyses. During the examination of spleen smears, Hepatozoon parasites were observed in eight out of 48 bank voles (M. glareolus). DNA was isolated from altogether 221 spleen samples, and 18S rDNA was amplified using two different PCR protocols. The eight bank vole samples were positive with PCR, but none of the other M. glareolus spleen samples or any of the tissue samples from other species were found to be infected. Sequenced amplicons were very similar to Hepatozoon spp. detected in M. glareolus in Spain and Poland. Ectoparasites were collected from the small mammal carcasses and from the vegetation. Hepatozoon DNA was not found in the 181 ticks removed from the small mammals or in the 162 ticks collected with flagging, but was detected in all three flea species (4/43 Megabothris turbidus Rothschild, 1909, 3/10 Ctenophthalmus assimilis Taschenberg, 1880 and 7/78 Ctenophthalmus agyrtes Heller, 1896). Based on gamont morphology, vertebrate and arthropod host species and DNA sequences, the parasites in our study can be identified as Hepatozoon erhardovae.

Spatial analysis of areas likely to harbor American cutaneous leishmaniasis in Seropédica, Rio de Janeiro State, Brazil

&lt;p class="Default"&gt;O objetivo deste estudo foi avaliar a distribuição espacial de leishmaniose tegumentar americana (LTA) no município de Seropédica, segundo graus de favorabilidade para sua ocorrência. O Sistema de Análise Geoambiental Vista-SAGA foi utilizado na preparação das bases de dados (mapas temáticos), análise ambiental, assinaturas e combinação. Os graus de favorabilidade foram obtidos por avaliações procedidas sobre os fatores uso do solo e cobertura vegetal, tipo de solo e geomorfologia (fatores geoambientais) e altitude e declividade (fatores topográficos). Os fatores utilizados nas análises foram selecionados com base na literatura e na viabilidade técnica para a preparação das bases de dados. Pesos e notas foram atribuídos aos fatores e suas categorias, respectivamente, conforme a relevância para o ciclo de vida de parasitos do gênero &lt;em&gt;Leishmania &lt;/em&gt;e de seus vetores. Os resultados das análises ambientais foram categorizados para representarem a distribuição espacial da favorabilidade, classificada como áreas pouquíssimo favorável, pouco favorável, favorável, muito favorável e muitíssimo favorável para ocorrência de LTA. Os resultados das assinaturas evidenciam que o município apresenta 6,81% da área classificada muitíssimo favorável, 65,14% muito favorável, 17,98 % favorável, 2,39% pouco favorável e 0,07% pouquíssimo favorável. As assinaturas sobre os mapas de resultados e temáticos permitiram não só localizar, mas também caracterizar o perfil dos ecossistemas quanto ao risco para a ocorrência de LTA, indicando que o município de Seropédica pode ser classificado como muito favorável para ocorrência desta doença tanto em áreas rurais quanto peri-urbanas e urbanas. Estes resultados poderão subsidiar a tomada de decisões dos órgãos responsáveis pelo controle e prevenção da LTA em Seropédica. Além disso, o geoprocessamento como ferramenta de integração de dados se mostrou uma alternativa de baixo custo para áreas onde haja dificuldade para realização de inquéritos.&lt;/p&gt;

Induction of Haemolysis and DNA Fragmentation in a Normal and Malarial-Infected Blood by Commonly - used Antimalarial Drugs in the North-Western Region of Nigeria.

Antimalarial drugs are medicines that are used to prevent or treat malaria effectively at different stages in the life cycle of the malarial parasites. In spite of this, a good number of these drugs have the potential to cause harm when they are misused or abused. This study was undertaken to evaluate the effects of commonly-used antimalarial drugs in the North Western region of Nigeria on haemolysis and DNA fragmentation in the blood of normal and malarial infected humans ex vivo. The drugs used were artemisinine, artesunate, chloroquine, coartem and quinine (0.5-8.0 mg/ml). Haemolysis, haemoglobin status and DNA fragmentations were assayed for using standard procedures. It was observed that all the drugs induced a remarkable dose-dependent haemolysis with more pronounced effects on apparently healthy humans. There was a significant (P < 0.05) decrease in the level of haemoglobin in normal blood samples when compared with control samples. Contrariwise, in the malaria-infected blood, the haemoglobin level significantly (P < 0.05) increased as compared with control. The drugs caused an exceptional significant (P < 0.05) induction of DNA fragmentation when compared with control. Commonly-used antimalarial drugs induced haemolysis and altered haemoglobin status which may spontaneously increases the cellular iron levels; a substrate for Fenton and Haber Weiss reactions, and eventually induces DNA fragmentation. Hence, adequate care should be taken during prescription with total avoidance for self medications and/or drugs abuse as a result of their adverse effects within the red blood cells and its immediate microenvironment.

Calcium signalling in malaria parasites.

Ca(2+) is a ubiquitous intracellular messenger in malaria parasites with important functions in asexual blood stages responsible for malaria symptoms, the preceding liver-stage infection and transmission through the mosquito. Intracellular messengers amplify signals by binding to effector molecules that trigger physiological changes. The characterisation of some Ca(2+) effector proteins has begun to provide insights into the vast range of biological processes controlled by Ca(2+) signalling in malaria parasites, including host cell egress and invasion, protein secretion, motility and cell cycle regulation. Despite the importance of Ca(2+) signalling during the life cycle of malaria parasites, little is known about Ca(2+) homeostasis. Recent findings highlighted that upstream of stage-specific Ca(2+) effectors is a conserved interplay between second messengers to control critical intracellular Ca(2+) signals throughout the life cycle. The identification of the molecular mechanisms integrating stage-transcending mechanisms of Ca(2+) homeostasis in a network of stage-specific regulator and effector pathways now represents a major challenge for a meaningful understanding of Ca(2+) signalling in malaria parasites.

Structural and functional attributes of malaria parasite diadenosine tetraphosphate hydrolase.

Malaria symptoms are driven by periodic multiplication cycles of Plasmodium parasites in human red blood corpuscles (RBCs). Malaria infection still accounts for ~600,000 annual deaths, and hence discovery of both new drug targets and drugs remains vital. In the present study, we have investigated the malaria parasite enzyme diadenosine tetraphosphate (Ap4A) hydrolase that regulates levels of signalling molecules like Ap4A by hydrolyzing them to ATP and AMP. We have tracked the spatial distribution of parasitic Ap4A hydrolase in infected RBCs, and reveal its unusual localization on the infected RBC membrane in subpopulation of infected cells. Interestingly, enzyme activity assays reveal an interaction between Ap4A hydrolase and the parasite growth inhibitor suramin. We also present a high resolution crystal structure of Ap4A hydrolase in apo- and sulphate- bound state, where the sulphate resides in the enzyme active site by mimicking the phosphate of substrates like Ap4A. The unexpected infected erythrocyte localization of the parasitic Ap4A hydrolase hints at a possible role of this enzyme in purinerigic signaling. In addition, atomic structure of Ap4A hydrolase provides insights for selective drug targeting.

Malaria Vaccine Development: Recent Advances alongside the Barriers

Although malaria control efforts have currently reduced much of the morbidity and mortality, yet malaria remains a hard problem in many parts of Africa. Together with the existing malaria control efforts, an effective malaria vaccine is expected to act as an important weapon to fight against malaria burden. Developing an efficacious malaria vaccine is a top priority in the agenda of global health program. However, the multi-stage life cycle, antigenic variation, and vast genetic diversity of malaria parasites made malaria vaccine development difficult for years. This study was conducted with the aim of reviewing the status of malaria vaccine development through different obstacles in the path. Vaccine trials currently upgraded to yield a partially effective and short-lived immunity with the pre-erythrocytic subunit vaccine, RTS,S/AS01, which is likely to be the first vaccine to be licensed for malaria control and elimination in sub-Saharan Africa. A promising result was also observed in the early trials with parenteral administration of the whole sporozoite vaccine in malaria-naive adults, where a complete protection against malaria was demonstrated. The subunit vaccines may not develop a strong sterile immunity among the malaria endemic community. Therefore, moving forward to the multi-stage vaccine comprising antigens from the pre-erythrocytic, erythrocytic and sexual stages of parasite lifecycle could be the best tool to neutralize the merozoites emerging from hepatocytes and red blood cells, and to break the sexual stage transmission. Furthermore, deep understanding of the potential vaccine targets and how immunity acts is a key roadmap to develop a fully effective vaccine against malaria.

EXPLORING THE PRE-ERYTHROCYTIC STAGE OF THE MALARIA PARASITE FOR POSSIBLE TARGET PROTEINS TO DEVELOP AN EFFECTIVE VACCINE AND LOOKING INTO AVAILABLE PREVENTIVE MEASURES AGAINST MALARIA:CAN SPECT &amp; SPECT2 ACT AS POTENTIAL TARGETS FOR AN EFFECTIVE VACCINE?

Malaria is most commonly found in tropical and sub-tropical countries of Africa. In a year, 3.2 billion people are at risk of getting malaria of which infection occurs in over 200 million of which one million results in death; hence it is one of the most infectious parasite diseases. 90% of the deaths occur in south of Saharan desert and most of the cases are of children under the age of five. In the year 2012, malaria caused estimated total deaths of 627,000. In the year 2013, malaria caused estimated total deaths of 500,000. 40% of total malaria cases in the world are from Nigeria and the Democratic Republic of Congo (Statistics provided by WHO). These stats strongly suggest the need of a preventive malaria vaccine. Here we analyze the malaria parasite cycle, specifically pre-erythrocytic stage, and present some possible target proteins. We also look at the current options for prevention of malaria.

Invaded Invaders: Infection of Invasive Brown Treesnakes on Guam by an Exotic Larval Cestode with a Life Cycle Comprised of Non-Native Hosts.

BackgroundMultiple host introductions to the same non-native environment have the potential to complete life cycles of parasites incidentally transported with them. Our goal was to identify a recently detected parasitic flatworm in the invasive Brown Treesnake (Boiga irregularis) on the remote Pacific island of Guam. We considered possible factors influencing parasite transmission, and tested for correlations between infection status and potential indicators of host fitness. We used genetic data from the parasite and information about the native ranges of other possible non-native hosts to hypothesize how it arrived on Guam and how its life cycle may be currently supported.MethodsWe identified the parasite by comparing larval morphology and mtDNA sequences with other Pseudophyllid tapeworms. We assessed probability of infection in individual snakes using logistic regression and examined different factors influencing presence of parasites in hosts.ResultsWe identified the parasite as the pseudophyllid cestode Spirometra erinaceieuropaei, with all sampled worms from multiple snakes sharing a single mtDNA haplotype. Infection appears to be limited to the only freshwater watershed on the island, where infection prevalence was high (77.5%). Larger snakes had a higher probability of being infected, consistent with the chronic nature of such infections. While infection status was positively correlated with body condition, infected snakes tended to have lower intra-peritoneal fat body mass, potentially indicating a negative effect on energy stores.ConclusionsWe discovered that B. irregularis inhabiting a small area of forested habitat in a freshwater watershed on Guam are often infected by a novel parasite of Asian origin. While further work is needed, this species of Spirometra, itself a non-native species, likely depends on a suite of recently introduced hosts from different parts of the world to complete the life cycle. This baseline study provides little evidence of any effects on host fitness, but additional data are needed to more thoroughly explore the consequences of infection in this invasive snake population.

Evolutionary consequence of a change in life cycle complexity: A link between precocious development and evolution toward female-biased sex allocation in a hermaphroditic parasite.

The evolutionary consequences of changes in the complex life cycles of parasites are not limited to the traits that directly affect transmission. For instance, mating systems that are altered due to precocious sexual maturation in what is typically regarded as an intermediate host may impact opportunities for outcrossing. In turn, reproductive traits may evolve to optimize sex allocation. Here, we test the hypothesis that sex allocation evolved toward a more female-biased function in populations of the hermaphroditic digenean trematode Alloglossidium progeneticum that can precociously reproduce in their second hosts. In these precocious populations, parasites are forced to self-fertilize as they remain encysted in their second hosts. In contrast, parasites in obligate three-host populations have more opportunities to outcross in their third host. We found strong support that in populations with precocious development, allocation to male resources was greatly reduced. We also identified a potential phenotypically plastic response in a body size sex allocation relationship that may be driven by the competition for mates. These results emphasize how changes in life cycle patterns that alter mating systems can impact the evolution of reproductive traits in parasites.

Structure of the parasite infracommunity of Sciades proops from the Japaratuba River Estuary, Sergipe, Brazil.

The catfish species Sciades proops inhabits muddy estuaries and shallow brackish lagoons, as well as freshwater. For these reasons, it is believed that this species may act as an intermediate, definitive and paratenic host in the life cycle of many parasites. From November 2010 to November 2011 and from August 2012 to July 2013, a total of 126 specimens of Sciades proops from the estuarine region of the Japaratuba River in the state of Sergipe, Brazil, were examined for parasites, of which 84.13% were infected by at least one species: Ergasilus sp. (Copepoda) (Prevalence P = 77.78%, Mean of Intensity MI = 10.08 ± 15.48, Mean Abundance MA = 14.27 ± 7.48) in the gills, Contracaecum sp. (P = 23.02%, MI = 20.59 ± 80.58, MA =39.12 ± 4.47) in the general cavity, Procamallanus sp. (P = 0.79%, MI = 1, MA = 0.01 ± 0.09), Raphidascaroides sp. (P = 2.31%, MI = 1.33 ± 0.58, MA = 0.33 ± 0.22) and Cuccullanus sp. (Nematoda) (P = 0.79%, MI = 1, MA = 0.01 ± 0.09) in the intestine, Ancyrocephalinae (Monogenea) (P = 0.79%, MI = 1, MA = 0.01 ± 0.09) in the gills, Pseudoacanthostomumpanamense (P = 1.59%, MI = 9.00 ± 8.49, MA = 0.14 ± 1.36) in the intestine, Clinostomum sp. (P = 1.59%, MI = 17.50 ± 23.33, MA = 0.29 ± 3.03) on the body surface and two unidentified metacercariae, referred to as Metacercaria 1 (P = 0.79%; IM = 1, MA = 0.01 ± 0.09) and Metacercaria 2 (Digenea) (P = 0.79%, MI = 7, MA = 0.06 ± 0.62) in the swim bladder. Ergasilus sp. was the dominant species and thus classified as core, with Contracaecum sp. as the satellite and other species as secondary species. The spatial distribution of infection with Ergasilus sp. and Contracaecum sp. showed a typical pattern of aggregate distribution. The sex of the host did not influence parasitic infections, but infection with Ergasilus sp. showed a positive and significant correlation with biometric and epidemiologic parameters, whereas infection with Contracaecum sp. was correlated only with prevalence and abundance.