Infection rates and pathogenicity of trypanosomatid gut parasites in the water strider Gerris odontogaster (Zett.) (Heteroptera: Gerridae)

Summary Trypanosomatid flagellates are common protozoan gut parasites of a wide range of insect species. Water striders (Gerridae) harbour the trypanosomatid Blastocrithidia gerridis. Three different populations of the water strider Gerris odontogaster in northern Sweden were sampled to assess the infection rate dynamics of trypanosomatids. The initially very low infection rates (0%–15%) early in the season were followed by a rapid increase during the reproductive period of the water striders, reaching very high levels (80%–90%). The pathogenic effects of trypanosomatids on G. odontogaster adults were studied in laboratory experiments. The parasites caused a general reduction of host vigour. Male skating endurance was negatively correlated with the intensity of the trypanosomatid infection. However, infection of trypanosomatids increased the mortality among adults only when the water striders were subjected to food stress. The trypanosomatids did not reduce the fecundity of females provided with food. We suggest that trypanosomatid gut parasites may be an important mortality factor in water strider populations. Since the pathogenicity of the parasites is enhanced by stress, parasitism by trypanosomatids may contribute to the regulation of host populations.     

Parasite infection and sand coarseness increase sand crab (Emerita analoga) burrowing time

Parasites with indirect life cycles require trophic transmission from intermediate hosts to definitive (vertebrate) hosts. Transmission may be facilitated if parasite infection alters the behavior of intermediate hosts such that they are more vulnerable to predation. Vulnerability to predation may also be influenced by abiotic factors; however, rarely are the effects of parasites and abiotic factors examined simultaneously. The swash zone of sandy beaches is a particularly harsh environment. Sand crabs (Emerita analoga) burrow rapidly in the swash zone to avoid predators and dislodgment. We examined prevalence and abundance of the acanthocephalan parasite Profilicollis altmani in sand crabs, and investigated the synergistic effects of sand grain size (an important abiotic factor), parasite infection, body size and reproductive condition on burrowing speed in females, from three California sites. More heavily parasitized crabs burrowed more slowly, making them potentially more vulnerable to predation by marine bird definitive hosts. Ovigerous females harbored more parasites than non-ovigerous females, but burrowed more quickly. All crabs burrowed slowest in the coarsest sand, and burrowing times increased with repeated testing, suggesting that it is energetically costly. Abiotic and biotic factors influence burrowing, and behavioral variation across sites may reflect the response to natural variation in these factors.     

Community of parasites in Triportheus curtus and Triportheus angulatus (Characidae) from a tributary of the Amazon River system (Brazil)

The present study compared the community of parasites in populations of Triportheus angulatus and T. curtus from a tributary of the Amazon River in northern Brazil. All hosts had one or more parasite species, 862,687 parasites were collected from T. curtus and 302,008 from T. angulatus. Species richness of parasites, Shannon diversity index and evenness index were higher for T. angulatus. The parasite communities of both hosts was similar (99%) and composed by Ichthyophthirius multifiliis, Anacanthorus pitophallus, metacercariae and Procamallanus (Spirocamallanus) inopinatus, with dominance of I. multifiliis. However, low infection level by Piscinodinium pilullare, Dolops sp. and Contracaecum larvae occurred only in T. angulatus, and Spironucleus sp. was found only in T. curtus. There were differences in the prevalence, intensity and mean abundance for some parasites of both hosts. There was aggregated dispersion of parasites in both hosts, but the infection of P. (S.) inopinatus in T. angulatus showed a random dispersion. For T. angulatus and T. curtus, the diversity and abundance of parasites were influenced by the host size. This was the first report of these parasite species for T. curtus, as well as of I. multifiliis, P. pilullare, Dolops sp., P. (S.) inopinatus and Contracecum sp. for T. angulatus.     

Parasite-induced parthenogenesis in a freshwater snail: stable,persistent patterns of parasitism

Summary The role of parasites in the evolution of host reproductive modes has gained renewed interest in evolutionary ecology. It was previously argued that obligate parthenogenesis (all-female reproduction) arose in a freshwater snail, Campeloma decisum, as a consequence of severe sperm limitation caused by an unencysted trematode, Leucochloridiomorpha constantiae. In the present study, certain conditions are examined for parasitic castration to account for the maintenance of parthenogenesis: the spatial patterns of the prevalence and intensity of infection on a broad geographical scale and its relationship to host genotype; the recovery from infection after isolation from sources of infection; age-related patterns of infections; and the effects of L. constantiae on snail fecundity.In contrast to the common pattern of the aggregated distribution of parasites within host populations, many snail populations with high prevalence and intensity of infection have non-aggregated parasite distributions. Clonal genotype of the host explained little of the variation in intensity and prevalence of infection by the parasite. Female snails maintained similar prevalence and intensity of infection after isolation, and individuals accumulated parasites throughout their lifespan, both of which suggest there is no effective immune response to infection by L. constantiae. Snail fecundity is not significantly influenced by the intensity of infection. These results suggest that L. constantiae may have represented a strong selective force against males during the initial introduction of this parasite into sexual snail populations because of the persistent nature of infection.     

Assortative pairing in Gammarus insensibilis (Amphipoda) infected by a trematode parasite

We have investigated the influence of Microphallus papillorobustus (Trematoda) on the reproductive biology and mating patterns of its intermediate host Gammarus insensibilis (Amphipoda). Infected Gammarus species show altered behaviour which renders them more susceptible to predation by Charadriiform birds, the parasite's definitive hosts. In a natural population of G. insensibilis, mean parasite intensity was higher for unpaired individuals than for paired individuals. Fecundity was reduced in infected amphipods. Size-assortative pairing was significant, although infected males were found with smaller females compared to uninfected males of the same size. There was also a positive assortative pairing by parasitic prevalence. Vertical segregation between infected and uninfected individuals, male-male competition for access to uninfected females, and female choice may explain assortative mating for prevalence. This study provides the first empirical evidence that parasites can have a direct effect on patterns of mating in gammarids.     

Saliva of laboratory-reared Lutzomyia longipalpis exacerbates Leishmania (Leishmania) amazonensis infection more potently than saliva of wild-caught Lutzomyia longipalpis

In order to compare the saliva effect from wild-caught and lab-reared L. longipalpis on the development of experimental cutaneous leishmaniasis, C57BL/6 mice were inoculated subcutaneously into the hind footpads with promastigotes of L. (L.) amazonensis plus salivary gland lysate from wild-caught (SGL-W) and lab-colonized (SGL-C) vectors. Lesion sizes were significantly larger in the mice infected with both saliva compared to mice infected with parasites alone; moreover, the lesions caused by parasite + SGL-C were significantly larger than the lesions caused by parasite + SGL-W. Histopathological morphometric studies regarding the acute phase of infections showed lower numbers of polymorphonuclear cells, greater numbers of mononuclear cells and parasites in SGL-C infected mice compared to SGL-W infected mice. In the chronic phase of infection, the number of mononuclear cells was lower and the number of parasites was greater in SGL-C infected mice than SGL-W infected mice. In vitro studies showed increased infection index of macrophages infected with parasites plus saliva compared to infection with parasites alone, with no difference between the saliva infection indices. SDS-PAGE gel for SGL-C and SGL-W showed differences in the composition and quantity of protein bands, determined by densitometry. These results call attention to the experimental saliva model, which shows exacerbation of infection caused by sandfly saliva.     

Honey bee and bumblebee trypanosomatids: specificity and potential for transmission

Abstract 1. Experimental studies of multihost parasite dynamics are scarce. Understanding the transmission dynamics of parasites in these systems is a key task in developing better models of parasite evolution and to make more accurate predictions of disease dynamics. 2. Bumblebee species (Bombus spp.) host the trypanosomatid parasite, Crithidia bombi. Its transmission in the field occurs through the shared use of flowers. Flowers are a perfect scenario for inter‐taxa transmission of diseases because they are used by a wide range of animals. 3. Honey bees host a poorly studied trypanosomatid, Crithidia mellificae. In this study, five questions have been experimentally addressed: (a) Can C. bombi infect honey bees? (b) Can C. mellificae infect bumblebees? (c) Can the honey bee act as a vector for C. bombi? (d) Are C. bombi cells present in honey‐bee faeces? (e) Does C. bombi have an effect on the mortality of honey bees after ingestion? 4. While both parasites were found to be specific to their hosts at the genus level, results suggest that honey bees may play a role in the epidemiology of C. bombi transmission.     

Focus: Zoonotic Disease: An Ecologically Framed Comparison of The Potential for Zoonotic Transmission of Non-Human and Human-Infecting Species of Malaria Parasite

The threats, both real and perceived, surrounding the development of new and emerging infectious diseases of humans are of critical concern to public health and well-being. Among these risks is the potential for zoonotic transmission to humans of species of the malaria parasite, Plasmodium, that have been considered historically to infect exclusively non-human hosts. Recently observed shifts in the mode, transmission, and presentation of malaria among several species studied are evidenced by shared vectors, atypical symptoms, and novel host-seeking behavior. Collectively, these changes indicate the presence of environmental and ecological pressures that are likely to influence the dynamics of these parasite life cycles and physiological make-up. These may be further affected and amplified by such factors as increased urban development and accelerated rate of climate change. In particular, the extended host-seeking behavior of what were once considered non-human malaria species indicates the specialist niche of human malaria parasites is not a limiting factor that drives the success of blood-borne parasites. While zoonotic transmission of non-human malaria parasites is generally considered to not be possible for the vast majority of Plasmodium species, failure to consider the feasibility of its occurrence may lead to the emergence of a potentially life-threatening blood-borne disease of humans. Here, we argue that recent trends in behavior among what were hitherto considered to be non-human malaria parasites to infect humans call for a cross-disciplinary, ecologically-focused approach to understanding the complexities of the vertebrate host/mosquito vector/malaria parasite triangular relationship. This highlights a pressing need to conduct a multi-species investigation for which we recommend the construction of a database to determine ecological differences among all known Plasmodium species, vectors, and hosts. Closing this knowledge gap may help to inform alternative means of malaria prevention and control.     

The relationship between flat periwinkle life histories and digenean infections

Larval digenean parasites were studied in Littorina obtusata (L.) and L. mariae Sacchi & Rastelli at Sawdern Point in West Wales. Shell parameters, ovipositor and shell colour, penis morphology and sex ratios were scored, and the influence of parasitism studied. A total of 7 species of parasites were found, although the prevalence was very low in L. mariae, especially in the females. The parasitic gigantism that has been described in other species of gastropod was not found in this study. Parasitic castration does occur in some infected male L. obtusata, resulting in severe stunting of the penis. However, this phenomena was never observed in L. mariae. The winkle species are congeneric and inhabit broadly similar niches on the shore; their life histories are however quite different — one being annual and the other perennial. This probably affects exposure to infection, and might explain the differing prevalence of the parasites.     

Global warming will reshuffle the areas of high prevalence and richness of three genera of avian blood parasites

The importance of parasitism for host populations depends on local parasite richness and prevalence: usually host individuals face higher infection risk in areas where parasites are most diverse, and host dispersal to or from these areas may have fitness consequences. Knowing how parasites are and will be distributed in space and time (in a context of global change) is thus crucial from both an ecological and a biological conservation perspective. Nevertheless, most research articles focus just on elaborating models of parasite distribution instead of parasite diversity. We produced distribution models of the areas where haemosporidian parasites are currently highly diverse (both at community and at within‐host levels) and prevalent among Iberian populations of a model passerine host: the blackcap Sylvia atricapilla; and how these areas are expected to vary according to three scenarios of climate change. On the basis of these models, we analysed whether variation among populations in parasite richness or prevalence are expected to remain the same or change in the future, thereby reshuffling the geographic mosaic of host‐parasite interactions as we observe it today. Our models predict a rearrangement of areas of high prevalence and richness of parasites in the future, with Haemoproteus and Leucocytozoon parasites (today the most diverse genera in blackcaps) losing areas of high diversity and Plasmodium parasites (the most virulent ones) gaining them. Likewise, the prevalence of multiple infections and parasite infracommunity richness would be reduced. Importantly, differences among populations in the prevalence and richness of parasites are expected to decrease in the future, creating a more homogeneous parasitic landscape. This predicts an altered geographic mosaic of host‐parasite relationships, which will modify the interaction arena in which parasite virulence evolves.     

A checklist of parasites in non‐native populations of rotan Perccottus glenii Dybowski, 1877 (Odontobutidae)

This review presents data on diversity, prevalence, and distribution of protistan and metazoan parasites in non‐native populations of the rotan Perccottus glenii. The information was collected using peer reviewed journals, difficult to access grey literature, and original data of the authors. As a whole, 70 literature sources from 1971 to 2012 were analyzed. The data originate from five of the 17 countries already colonized by P. glenii. A total of 97 parasite species/taxa are listed, each with the location in/on the host, geographical localities, countries, and literature sources. Where available, the number of fish examined as well as the prevalence and range of infection intensity are cited from the respective sources. Attention is given to host‐specific parasites because the rotan is a vector of their new geographical distribution. The current state and perspectives for further research are discussed.     

Manipulation of oviposition patterns of the parasitoidCyzenis albicans (Tachinidae) in the field using plant extracts

We examine the oviposition behavior of the parasitic fly Cyzenis albicans(Fall.) to determine if long-distance or contact chemical cues given off by damaged oak and apple foliage influences the attack of their host the winter moth Operophtera brumata(L.). Wind-tunnel experiments indicate the presence of an attractive odor in oak leaves and the absence of an attractant in apple leaves. The application of oak foliage extracts to apple trees increased the number of parasitoid eggs laid and the level of parasitism of winter moths in the field. The impact of altered host-seeking behavior by the parastoid is discussed in the context of the population ecology of its host.     

Heavy infestation by endoparasitic copepod crustaceans (Poecilostomatoida: Splanchnotrophidae) in Chilean opisthobranch gastropods, with aspects of splanchnotrophid evolution

Copepods of the family Splanchnotrophidae are very significant parasites of shell-less opisthobranchs, but little information exists on their occurrence, infection frequencies, and local or seasonal abundances. Using a quantitative faunistic approach, 2257 potential hosts belonging to 47 opisthobranch species were collected from 1991 to 1996 off the Chilean and Argentinian coasts, mainly by SCUBA. Endoparasitic splanchnotrophids of the genus Ismaila were found in 303 host specimens, corresponding to a 13% prevalence of infection. The opisthobranch hosts were one sacoglossan, three doridoidean and four aeolidoidean nudibranch species. In total, 12 Chilean opisthobranch species are known to be infected with splanchnotrophids. This amounts to about 20% of all shell-less opisthobranch species from Chile, and a remarkable 26% of all splanchnotrophid hosts worldwide. Infection frequencies are low in most host species, but reached 89–100% in certain populations of Thecacera darwini, Okenia luna, Flabellina sp. 1 and Elysia patagonica, representing the highest rates of infestation by splanchnotrophids ever documented. In Thecacera darwini, the prevalence was very low in northern Chile, consistently high in central Chile, and low in the south. High infestation coupled with a high number of sympatric but host-specific species indicate the coast of central Chile is a centre of Ismaila evolution. The biogeography of splanchnotrophid genera is discussed, and a hypothesis on their distributional history is presented.See also Electronic Supplement (Parts 1 and 2) at http://www.senckenberg.de/odes/02-03.htm     

Prevalence of coccidia parasites (Protozoa) in red squirrels ( Sciurus vulgaris): effects of host phenotype and environmental factors

We investigated the relative importance of environmental factors versus host phenotype in determining parasite prevalence in Eurasian red squirrels ( Sciurus vulgaris). One hundred and forty-three fecal samples of 116 different squirrels collected in 2000 and 2001 from five study areas in the Italian Alps, were examined for intestinal protozoans. Two species of Eimeria were present with a medium to high prevalence in both years and in all areas, while two other species were rare, occurring only in some areas and not in all years. Cryptosporidium parvum had a high prevalence in the two study areas of the Western Alps, while in the three areas of the Central Alps it was recorded only once. The prevalence of Eimeria sciurorum and C. parvum fluctuated in parallel with squirrel density, suggesting a possible correlation between the presence of these protozoans and host density. A gender effect on E. sciurorum prevalence at low density could be explained by different space use patterns and social organization of males and females. C. parvum occurred more frequently in young squirrels, suggesting an acquired immunity in adults, but age-related susceptibility was not found for eimerian species. The coccidian community was more similar within than between regions, and study area and year were key parameters in predicting coccidia infection. There was no evidence of competition between coccidian species, but one positive interaction between E. sciurorum and E. andrewsi was observed. Our results suggest that the effects of geographic region, area features, and year effects probably related to fluctuations in host population density, were more important than individual phenotypic host characteristics in structuring the coccidian assemblage and determining levels of parasite prevalence in red squirrel populations.     

Fine‐scale distribution modeling of avian malaria vectors in north‐central Kansas

Infectious diseases increasingly play a role in the decline of wildlife populations. Vector‐borne diseases, in particular, have been implicated in mass mortality events and localized population declines are threatening some species with extinction. Transmission patterns for vector‐borne diseases are influenced by the spatial distribution of vectors and are therefore not uniform across the landscape. Avian malaria is a globally distributed vector‐borne disease that has been shown to affect endemic bird populations of North America. We evaluated shared habitat use between avian malaria vectors, mosquitoes in the genus Culex and a native grassland bird, the Greater Prairie‐Chicken (Tympanuchus cupido), by (1) modeling the distribution of Culex spp. occurrence across the Smoky Hills of north‐central Kansas using detection data and habitat variables, (2) assessing the occurrence of these vectors at nests of female Greater Prairie‐Chickens, and (3) evaluating if shared habitat use between vectors and hosts is correlated with malarial infection status of the Greater Prairie‐Chicken. Our results indicate that Culex occurrence increased at nest locations compared to other available but unoccupied grassland habitats; however the shared habitat use between vectors and hosts did not result in an increased prevalence of malarial parasites in Greater Prairie‐Chickens that occupied habitats with high vector occurrence. We developed a predictive map to illustrate the associations between Culex occurrence and infection status with malarial parasites in an obligate grassland bird that may be used to guide management decisions to limit the spread of vector‐borne diseases.     

Higher infection probability of haemosporidian parasites in Blue-black Grassquits (Volatinia jacarina) inhabiting native vegetation across Brazil

Human induced changes on landscape can alter the biotic and abiotic factors that influence the transmission of vector-borne parasites. To examine how infection rates of vector-transmitted parasites respond to changes on natural landscapes, we captured 330 Blue-black Grassquits (Volatinia jacarina) in Brazilian biomes and assessed the prevalence and diversity of avian haemosporidian parasites (Plasmodium and Haemoproteus) across avian host populations inhabiting environment under different disturbance and climatic conditions. Overall prevalence in Blue-black Grassquits was low (11%) and infection rates exhibited considerable spatial variation, ranging from zero to 39%. Based on genetic divergence of cytochrome b gene, we found two lineages of Haemoproteus (Parahaemoproteus) and 10 of Plasmodium. We showed that Blue-black Grassquit populations inhabiting sites with higher proportion of native vegetation cover were more infected across Brazil. Other landscape metrics (number of water bodies and distance to urban areas) and climatic condition (temperature and precipitation) known to influence vector activity and promote avian malaria transmission did not explain infection probability in Blue-black Grassquit populations. Moreover, breeding season did not explain prevalence across avian host populations. Our findings suggest that avian haemosporidian prevalence and diversity in Blue-black Grassquit populations are determined by recent anthropogenic changes in vegetation cover that may alter microclimate, thus influencing vector activity and parasite transmission.     

Beyond immunity: quantifying the effects of host anti-parasite behavior on parasite transmission

A host’s first line of defense in response to the threat of parasitic infection is behavior, yet the efficacy of anti-parasite behaviors in reducing infection are rarely quantified relative to immunological defense mechanisms. Larval amphibians developing in aquatic habitats are at risk of infection from a diverse assemblage of pathogens, some of which cause substantial morbidity and mortality, suggesting that behavioral avoidance and resistance could be significant defensive strategies. To quantify the importance of anti-parasite behaviors in reducing infection, we exposed larval Pacific chorus frogs (Pseudacris regilla) to pathogenic trematodes (Ribeiroia and Echinostoma) in one of two experimental conditions: behaviorally active (unmanipulated) or behaviorally impaired (anesthetized). By quantifying both the number of successful and unsuccessful parasites, we show that host behavior reduces infection prevalence and intensity for both parasites. Anesthetized hosts were 20–39% more likely to become infected and, when infected, supported 2.8-fold more parasitic cysts. Echinostoma had a 60% lower infection success relative to the more deadly Ribeiroia and was also more vulnerable to behaviorally mediated reductions in transmission. For Ribeiroia, increases in host mass enhanced infection success, consistent with epidemiological theory, but this relationship was eroded among active hosts. Our results underscore the importance of host behavior in mitigating disease risk and suggest that, in some systems, anti-parasite behaviors can be as or more effective than immune-mediated defenses in reducing infection. Considering the severe pathologies induced by these and other pathogens of amphibians, we emphasize the value of a broader understanding of anti-parasite behaviors and how co-occurring stressors affect them.     

Leishmania infantum and Toxoplasma gondii: Mixed infection of macrophages in vitro and in vivo

Although macrophages have a microbicidal role in the immune system they themselves can be infected by pathogens. Often a simultaneous infection by more than one microbe may occur in a single cell. This is the first report of coinfection of macrophages with Toxoplasma gondii and Leishmania infantum, in vitro and in vivo. L. infantum does not cause severe disease in mice but T. gondii, RH strain, is lethal. Cell culture studies using THP-1 macrophages dually infected in vitro revealed that 4.3% harbored both parasites 24 h after infection. When mice were infected with both parasites on the same day 7.3% of the infected cells carried both parasites 7 days later. Yet, if mice were first infected with L. infantum and then with Toxoplasma (5 days post-infection) 18.7% of the macrophages hosted either parasite but concomitant infection could not be found and mice, already harboring L. infantum, survived Toxoplasma’s lethal effect.     

Gastrointestinal Parasites in Free-Ranging Kenyan Baboons (Papio cynocephalus and P. anubis)

We screened fecal samples from 3 groups of wild-living baboons (Papio cynocephalus and P. anubis), involved in longitudinal behavioral studies, for evidence of gastrointestinal parasites. The two objectives of the study were: 1) to compare parasites from two of the groups with different foraging behavior from the same area and 2) to obtain fecal parasitic data on 3 groups of baboons to provide baseline reference data. We sampled individual baboons opportunistically from Lodge and Hook's groups, Amboseli National Park and from Mpala Group, Mpala Wildlife Research Centre, Kenya. Lodge Group baboons supplemented foraging on wild foods by daily foraging in human-source refuse, whereas Hook's and Mpala groups did not. We collected fecal samples from 55, 30 and 42 individuals in Hook's, Lodge and Mpala groups, respectively, and processed them via ether sedimentation. We identified strongylids, Streptopharagus sp., Physaloptera sp., Trichuris sp., Enterobius sp., and Strongyloides sp., in the feces, but no parasite directly attributable to exposure to people. Garbage- and wild-feeding Amboseli baboons differed in the prevalence of Streptopharagus sp., Physaloptera sp. and Trichuris sp.