Should Trypanosoma cruzi be called "cruzi" complex? A review of the parasite diversity and the potential of selecting population after in Vitro culturing and mice infection

Morpho-biological diversity of Trypanosoma cruzi has been known since Chagas' first works in 1909. Several further studies confirmed the morphological differences among the parasite strains, which were isolated from different reservoirs and vectors, as well as from human beings. In the early sixties, antigenic differences were found in the parasite strains from various sources. These differences, coupled to the observation of regional variations of the disease, led to the proposal of the term cruzi complex to designate the taxon T. cruzi. Since then this protozoan has been typed in distinct biodemes, zymodemes and lineages which were consensually grouped into T. cruzi I, T. cruzi II and into non-grouped strains. T. cruzi genotypic characterization, initially carried out by schizodeme analysis and more recently by various other techniques, has shown a great diversity of the parasite strains. In fact, T. cruzi is formed by groups of heterogeneous sub-population, which present specific characteristics, including distinct histotropism. The interaction of the different infecting clones of the cruzi complex and the human host will determine the morbidity of the disease.

How many parasites species a frog might have? determinants of parasite diversity in South American anurans

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Babesia spp. in European wild ruminant species: parasite diversity and risk factors for infection.

Babesia are tick-borne parasites that are increasingly considered as a threat to animal and public health. We aimed to assess the role of European free-ranging wild ruminants as maintenance mammalian hosts for Babesia species and to determine risk factors for infection. EDTA blood was collected from 222 roe deer (Capreolus c. capreolus), 231 red deer (Cervus e. elaphus), 267 Alpine chamois (Rupicapra r. rupicapra) and 264 Alpine ibex (Capra i. ibex) from all over Switzerland and analysed by PCR with pan-Babesia primers targeting the 18S rRNA gene, primers specific for B. capreoli and Babesia sp. EU1, and by sequencing. Babesia species, including B. divergens, B. capreoli, Babesia sp. EU1, Babesia sp. CH1 and B. motasi, were detected in 10.7% of all samples. Five individuals were co-infected with two Babesia species. Infection with specific Babesia varied widely between host species. Cervidae were significantly more infected with Babesia spp. than Caprinae. Babesia capreoli and Babesia sp. EU1 were mostly found in roe deer (prevalences 17.1% and 7.7%, respectively) and B. divergens and Babesia sp. CH1 only in red deer. Factors significantly associated with infection were low altitude and young age. Identification of Babesia sp. CH1 in red deer, co-infection with multiple Babesia species and infection of wild Caprinae with B. motasi and Babesia sp. EU1 are novel findings. We propose wild Caprinae as spillover or accidental hosts for Babesia species but wild Cervidae as mammalian reservoir hosts for B. capreoli, possibly Babesia sp. EU1 and Babesia sp. CH1, whereas their role regarding B. divergens is more elusive.

Predictors of red fox (Vulpes vulpes) helminth parasite diversity in the provinces of Spain

We analysed the viscera of 321 red foxes collected over the last 30 years in 34 of the 47 provinces of peninsular Spain, and identified their helminth parasites. We measured parasite diversity in each sampled province using four diversity indices: Species richness, Marg a l e f’s species richness index, Shannon’s species diversity index, and inverse Simpson’s index. In order to find geographical, environmental, and/or human-related predictors of fox parasite diversity, we recorded 45 variables related to topography, climate, lithology, habitat heterogeneity, land use, spatial situation, human activity, sampling effort, and fox presence probability (obtained after environmental modelling of fox distribution). We then performed a stepwise linear regression of each diversity index on these variables, to find a minimal subset of statistically significant variables that account for the variation in each diversity index. We found that most parasite diversity indices increase with the mean distance to urban centres, or in other words, foxes in more rural provinces have a more diverse helminth fauna. Sampling effort and fox presence probability (probably related to fox density) also appeared as conditioning variables for some indices, as well as soil permeability (related with water availability). We then extrapolated the models to predict these fox parasite diversity indices in non-sampled provinces and have a view of their geographical trends.

Variety matters: adaptive genetic diversity and parasite load in two mouse opossums from the Brazilian Atlantic forest

The adaptive potential of a species to a changing environment and in disease defence is primarily based on genetic variation. Immune genes, such as genes of the major histocompatibility complex (MHC), may thereby be of particular importance. In marsupials, however, there is very little knowledge about natural levels and functional importance of MHC polymorphism, despite their key role in the mammalian evolution. In a previous study, we discovered remarkable differences in the MHC class II diversity between two species of mouse opossums (Gracilinanus microtarsus, Marmosops incanus) from the Brazilian Atlantic forest, which is one of the most endangered hotspots for biodiversity conservation. Since the main forces in generating MHC diversity are assumed to be pathogens, we investigated in this study gastrointestinal parasite burden and functional associations between the individual MHC constitution and parasite load. We tested two contrasting scenarios, which might explain differences in MHC diversity between species. We predicted that a species with low MHC diversity would either be under relaxed selection pressure by low parasite diversity (`Evolutionary equilibrium` scenario), or there was a recent loss in MHC diversity leading to a lack of resistance alleles and increased parasite burden (`Unbalanced situation` scenario). In both species it became apparent that the MHC class II is functionally important in defence against gastrointestinal helminths, which was shown here for the first time in marsupials. On the population level, parasite diversity did not markedly differ between the two host species. However, we did observe considerable differences in the individual parasite load (parasite prevalence and infection intensity): while M. incanus revealed low MHC DAB diversity and high parasite load, G. microtarsus showed a tenfold higher population wide MHC DAB diversity and lower parasite burden. These results support the second scenario of an unbalanced situation.

Parasite abundance and diversity in mammals: correlates with host ecology.

Fecally dispersed parasites of 12 wild mammal species in Mudumalai Sanctuary, southern India, were studied. Fecal propagule densities and parasite diversity measures were correlated with host ecological variables. Host species with higher predatory pressure had lower parasite loads and parasite diversity. Host body weight, home range, population density, gregariousness, and diet did not show predicted effects on parasite loads. Measures of alpha diversity were positively correlated with parasite abundance and were negatively correlated with beta diversity. Based on these data, hypotheses regarding determinants of parasite community are discussed.

Helminths of introduced house sparrows (Passer domesticus) in Brazil: does population age affect parasite richness?

Species introductions have altered host and parasite diversity throughout the world. In the case of introduced hosts, population age appears to be a good predictor of parasite richness. Habitat alteration is another variable that may impact host-parasite interactions by affecting the availability of intermediate hosts. The house sparrow (Passer domesticus (Linnaeus, 1758)) is a good model to test these predictions. It was introduced in several parts of the world and can be found across rural-urban gradients. A total of 160 house sparrows from Porto Alegre, state of Rio Grande do Sul, Brazil, were necropsied. Thirty house sparrows (19 %) were parasitized with at least one out of five helminth species (Digenea: Tamerlania inopina Freitas, 1951 and Eumegacetes sp.; Eucestoda: Choanotaenia passerina (Fuhrmann, 1907) Fuhrmann, 1932; Nematoda: Dispharynx nasuta (Rudolphi, 1819) Stiles & Hassall, 1920 and Cardiofilaria pavlovskyi Strom, 1937). Overall, there was no difference in prevalence and intensity of infection of any parasite species, parasite richness and community diversity between adult males and females and adults and juveniles. The number of infected sparrows among seasons, the richness of helminths and the abundance of species were also similar between rural and urban landscapes. Only the prevalence of C. passerina varied seasonally (p=0.0007). A decrease in the number of parasite species from the original range of P. domesticus (13) to its port of entrance in Brazil, the city of Rio de Janeiro (nine), to Porto Alegre (five) is compatible with the hypothesis that host population age is a good predictor of parasite richness.

Diversity, prevalence and virulence of fungal entomopathogens in colonies of the ant Formica selysi

The richness of the parasitic community associated with social insect colonies has rarely been investigated. Moreover, understanding how hosts and pathogens interact in nature is important to interpret results from laboratory experiments. Here, we assessed the diversity, prevalence and virulence of fungal entomopathogens present around and within colonies of the ant Formica selysi. We detected eight fungal species known to be entomopathogenic in soil sampled from the habitat of ants. Six of these entomopathogens were found in active nests, abandoned nests, and corpses from dump piles or live ants. A systematic search for the presence of three generalist fungal entomopathogens in ant colonies revealed a large variation in their prevalence. The most common of the three pathogens, Paecilomyces lilacinus, was detected in 44% of the colonies. Beauveria bassiana occurred in 17% of the colonies, often in association with P. lilacinus, whereas we did not detect Metarhizium brunneum (formerly M. anisopliae) in active colonies. The three fungal species caused significant mortality to experimentally challenged ants, but varied in their degree of virulence. There was a high level of genetic diversity within B. bassiana isolates, which delineated three genetic strains that also differed significantly in their virulence. Overall, our study indicates that the ants encounter a diversity of fungal entomopathogens in their natural habitat. Moreover, some generalist pathogens vary greatly in their virulence and prevalence in ant colonies, which calls for further studies on the specificity of the interactions between the ant hosts and their fungal pathogens.

The effect of repeated exposure to parasite genotypes of the eyefluke Diplostomum pseudospathaceum on infection rate and immunization in three-spined sticklebacks

Adaptive immunity in vertebrates can confer increased resistance against invading pathogens upon re-infection. But how specific parasite genotypes affect the transition from innate to adaptive immunity is poorly understood. Here, we investigated the effects of homologous and heterologous exposures of genetically distinct parasite lineages of the eye fluke Diplostomum pseudospathaceum on gene expression patterns of adaptive immunity in sticklebacks (Gasterosteus aculeatus). We showed that observable differences were largely attributable to final exposures and that there is no transcription pattern characteristic for a general response to repeated infections with D. pseudospathaceum. Final exposure did not unify expression patterns of heterologous pre-exposed fish. Interestingly, heterologous final exposures showed similarities between different treatment groups subjected to homologous pre-exposure. The observed pattern was supported by parasite infection rates and suggests that host immunization was optimized towards an adaptive immune response that favored effectiveness against parasite diversity over specificity.

Species accumulation curves and their applications in parasite ecology

Species accumulation curves (SACs) chart the increase in recovery of new species as a function of some measure of sampling effort. Studies of parasite diversity can benefit from the application of SACs, both as empirical tools to guide sampling efforts and predict richness, and because their properties are informative about community patterns and the structure of parasite diversity. SACs can be used to infer interactivity in parasite infra-communities, to partition species richness into contributions from different spatial scales and different levels of the host hierarchy (individuals, populations and communities) or to identify modes of community assembly (niche versus dispersal). A historical tendency to treat individual hosts as statistically equivalent replicates (quadrats) seemingly satisfies the sample-based subgroup of SACs but care is required in this because of the inequality of hosts as sampling units. Knowledge of the true distribution of parasite richness over multiple host-derived and spatial scales is far from complete but SACs can improve the understanding of diversity patterns in parasite assemblages.

Communities of parasite metazoans in Piaractus brachypomus (Pisces, Serrasalmidae) in the lower Amazon River (Brazil).

The aim of this study was to investigate the component community of parasite metazoans of Piaractus brachypomus in the lower Amazon River, northern Brazil. From 34 necropsied fish, 27,384 metazoan parasites were collected, such as Anacanthorus spathulatus, Mymarothecium viatorum and Notozothecium janauachensis (Monogenoidea); Spectatus spectatus and Contracaecum sp (Nematoda); Clinostomum marginatum and Dadaytrema oxycephala (Digenea); and Argulus carteri and Ergasilus sp. (Crustacea). The dominant species was S. spectatus followed by monogenoidean species, and there was aggregated dispersion of parasites, except for D. oxycephala and Contracaecum sp., which presented random dispersion. Positive correlation among the abundance of the three monogenoideans species were found, thus indicating that there was no competition between the species of these parasites on the gills of hosts. The abundances of some parasite species showed positive correlations with the size of the hosts, but the condition factor of the fish was not affected by the parasitism levels. It showed that this host had a metazoan community characterized by high species richness of metazoans, low evenness and high diversity of parasites, with prevalence of endoparasites, including larval stages. This was the first record of C. marginatum, A. carteri, Ergasilus sp. and Contracaecum sp. for P. brachypomus.

An ecological and comparative analysis of parasites in juvenile Mugil liza (Pisces, Mugilidae) from two sites in Samborombón bay, Argentina

ABSTRACT Mugil liza Valenciennes, 1836 is an economically important food fish and has been recommended for aquaculture in South America. A total of 278 fishes were collected in the spring and summer of 2009 and 2010. These fish were sorted into sample groups according to their size class. We used Bayesian statistics and 95% credible intervals for each parameter tested were calculated. Fish studied harbored a total of 15 different species of parasites. Diversity of parasite species found on Mugil liza was greatest at the S.R.C. collection site, but evidenced a lower species richness than at A.R. site. The 1st size fishes of both sites evidenced greater parasite diversity than either 2nd or 3rd size fish. Differences observed could be explained by the different use of habitat types at the two sites or differential susceptibility to infection by parasites. The dominance of D. fastigatainfluenced observed results of lower community diversity indexes. New works elucidating different parasite life cycles within juvenile and adults ofM. liza in Argentina, promise to be important for determining the risk of the parasitism by zoonotic metacercariae A. (P.) longa and use of this fish as food and an economic resource, and the possible use of mullet parasites in other promising fields as indicators of biodiversity, and/ or water contamination.

Helminth parasites of Leptodactylus podicipinus (Anura: Leptodactylidae) from south-eastern Pantanal, State of Mato Grosso do Sul, Brazil

Forty-three specimens of Leptodactylus podicipinus (Anura: Leptodactylidae) were collected in the south-eastern Pantanal, municipality of Corumba, State of Mato Grosso do Sul, Brazil in February and July 2007, and examined for endoparasites. Forty (93%) specimens were infected with at least one helminth species. The predominant parasites were nematodes (Aplectana sp., Cosmocerca podicipinus, Oswaldocruzia lopesi, Physalopteroides venancioi, Rhabdias sp.), but the trematode Catadiscus propinquus also showed high prevalence. The trematodes Infidum infidum and Travtrema stenocotyle were also found, but in only one specimen. Adult frogs showed higher parasite diversity than subadults. Leptodactylus podicipinus was preferentially infected by direct life-cycle parasites and was reported as a new host record for seven helminth species.

Diversidade de helmintos de Notothenia coriiceps Richardson, 1844 da Baía do Almirantado, Ilha do Rei George, Antártica

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)