Extracellular ATP triggers proteolysis and cytosolic Ca2+ rise in Plasmodium berghei and Plasmodium yoelii malaria parasites

Background: Plasmodium has a complex cell biology and it is essential to dissect the cell-signalling pathways underlying its survival within the host. Methods: Using the fluorescence resonance energy transfer (FRET) peptide substrate Abz-AIKFFARQ-EDDnp and Fluo4/AM, the effects of extracellular ATP on triggering proteolysis and Ca2+ signalling in Plasmodium berghei and Plasmodium yoelii malaria parasites were investigated. Results: The protease activity was blocked in the presence of the purinergic receptor blockers suramin (50 mu M) and PPADS (50 mu M) or the extracellular and intracellular calcium chelators EGTA (5 mM) and BAPTA/AM (25, 100, 200 and 500 mu M), respectively for P. yoelii and P. berghei. Addition of ATP (50, 70, 200 and 250 mu M) to isolated parasites previously loaded with Fluo4/AM in a Ca2+-containing medium led to an increase in cytosolic calcium. This rise was blocked by pre-incubating the parasites with either purinergic antagonists PPADS (50 mu M), TNP-ATP (50 mu M) or the purinergic blockers KN-62 (10 mu M) and Ip5I (10 mu M). Incubating P. berghei infected cells with KN-62 (200 mu M) resulted in a changed profile of merozoite surface protein 1 (MSP1) processing as revealed by western blot assays. Moreover incubating P. berghei for 17 h with KN-62 (10 mu M) led to an increase in rings forms (82% +/- 4, n = 11) and a decrease in trophozoite forms (18% +/- 4, n = 11). Conclusions: The data clearly show that purinergic signalling modulates P. berghei protease(s) activity and that MSP1 is one target in this pathway.

Prevalence, geographic and seasonal distribution of protozoan and myxozoan parasites of jau (Zungaro jahu)

Adriano E.A., Ceccarelli P.S., Silva M.R.M. & Maia A.A. M. 2012. [Prevalence, geographic and seasonal distribution of protozoan and myxozoan parasites of jau (Zungaro jahu) in the Pantanal of Mato Grosso, Brazil.] Prevalencia, distribuicao geografica e sazonal de protozoarios e mixozoarios parasitos de jau (Zungaro jahu) no Pantanal Matogrossense. Pesquisa Veterinaria Brasileira 32(12):1341-1344. Departamento de Ciencias Basicas, Faculdade de Zootecnia e Engenharia de Alimentos, Universidade de Sao Paulo, Av. Duque de Caxias Norte 225, Pirassununga, SP 13635-900, Brazil. E-mail: antomaia@usp.br In a study carried out in the Pantanal of Mato Grosso, Brazil, the prevalence, geographic and seasonal distribution of protozoan and myxozoan parasites of Zungaro jahu was evaluated. The fish were captured in the southern region of Pantanal Mato-grossense (Aquidauana, Miranda and Paraguay rivers) in 2001, 2002 and 2003, in the central region (Pantanal National Park - PARNA Pantanal) in 2003, 2004, 2005 and 2008, and in the northern region (Cuiaba and Manso rivers, in the municipality of Nobres) in 2003, 2004 and 2005. Trichodina sp. was identified parasitized skin and gills of jau in the three regions studied. Epistylis sp. parasitized skin and Cryptobia sp. the gills and were restricted to the Central region, whilst Ichthyophthirius multifiliis parasitized skin in the three regions studied. The occurrence of myxozoans was also observed: Myxobolus cordeiroi parasitized several organs and Henneguya sp. parasitized the gills of jau in the three regions studied.

Parasites in the neighbourhood: Interactions of the mistletoe Phoradendron affine (Viscaceae) with its dispersers and hosts in urban areas of Brazil

Mistletoes constitute an important food resource for animals in many ecosystems. However, these plants are considered pests in urban areas because of deleterious effects they have on the host trees. Studies in urban areas were mostly focused on listing host species or procedures to control the "pest". In this sense, broader studies including several aspects of mistletoes ecology in urban ecosystems are still missing. We studied the interaction of the mistletoe, Phoradendron affine, with its dispersers and hosts in two urban sites in Uberlandia, Brazil. Phoradendron affine fruits were consumed almost exclusively by Euphonia chlorotica, which was crucial for seed germination. Parasitism was recorded in five hosts, two native (Handroanthus chrysotrichus and Tabebuia roseoalba) and three exotic species (Spathodea campanulata, Ligustrum lucidum and Melia azedarach). Mistletoes were found parasitizing larger host trees, a trend commonly reported for mistletoe-host interaction. Mistletoe seed germination was not affected by the trees species, whether host or non-host, but the radicle of germinated seeds could not penetrate the bark and seedlings invariably died in non-host species. We found a high prevalence of parasitism in our study, in comparison to what previous studies reported for natural areas. The spatial distribution of the hosts and high light incidence on isolated host trees may lead to this high prevalence in urban areas. Rather than eradicated, mistletoes in urban areas should be ecologically managed and their importance for bird species conservation must be considered. More studies to determine which bird species are favoured by mistletoe presence in urban areas will be essential for, this purpose. (C) 2012 Elsevier GmbH. All rights reserved.

HELMINTH PARASITES OF HYPSIBOAS PRASINUS (ANURA: HYLIDAE) FROM TWO ATLANTIC FOREST FRAGMENTS, SAO PAULO STATE, BRAZIL

Seventy-seven males of Hypsiboas prasinus from 2 Atlantic forest fragments in the municipalities of Botucatu and Jundiai, sao Paulo State, Brazil, were examined for endoparasites. The frogs were captured in summer (January until March) and winter (July/August) of 2008 and 2009. Thirty-three males (75%) from Botucatu were infected with Rhabdias cf. fuelleborni, cosmocerciid nematodes, and Cylindrotaenia americana. Twenty-five tree frogs (78.5%) from Jundiai were infected by Rhabdias cf. fuelleborni, Physaloptera sp., and cosmocerciid nematodes. Only cosmocerciid nematodes presented a statistically significance difference in prevalence (z = 4.345; P < 0.001) and mean abundance (t = 562.0; P < 0.001) between Botucatu and Jundiai during the winter. Also, the cosmocerciids exhibited higher mean abundance (t = 196.0; P = 0.034) in winter when compared with summer at the Jundiai site. Moreover, to our knowledge, this is the first report of C. americana in the Brazilian Hylidae. This study presents 4 new records of nematodes in H. prasinus.

Parasites reveal movement of bats between the New and Old Worlds

The global distribution of bat taxa indicates that the Atlantic and Pacific Oceans are effective barriers to movement between the Old and New Worlds. For instance, one of the major suborders, Yinpterochiroptera, has an exclusively Old World distribution, and within the other, Yangochiroptera, no species and only five genera are common to both. However, as bats are sometimes blown out to sea, and have colonised isolated islands, occasional natural movement between the New and Old Worlds does appear to be possible. Here we identify new genotypes of a blood parasite, Trypanosoma dionisii, in Old World bats that are closely related to South American strains. Using highly conservative calibration points, divergence of Old and New World strains is estimated to have occurred 3.2-5.0 million years ago (MYA), depending on the method used (upper 95% CL for maximum time 11.4 MYA). The true date of divergence is likely to be considerably more recent. These results demonstrate that taxon-specific parasites can indicate historical movements of their hosts, even where their hosts may have left no lasting phylogenetic footprint. (C) 2012 Elsevier Inc. All rights reserved.

IgG Antibody responses in mice coinfected with Toxocara canis and other helminths or protozoan parasites

The immune response expressed by IgG antibodies in BALB/c mice experimentally infected with Toxocara canis, was studied with the aim of verifying the possible in vivo cross-reactivity between antigens of T. canis and other parasites (Ascaris suum, Taenia crassiceps, Schistosoma mansoni, Strongyloides venezuelensis and Toxoplasma gondii). Experiments included three groups of mice: one infected only by T. canis, another with one of the other species of parasites and a third concomitantly infected with T. canis and the other species in question. Animals were bled by orbital plexus at 23, 38 and 70 days post infection (p.i.). Sera were analyzed for anti-Toxocara antibodies by ELISA and Immunoblotting, using excretion-secretion antigens (ES), obtained from culture of third-stage larvae of T. canis. For all experiments a control group comprised by ten non-infected mice was used. Only in the case of A. suum infection, in these experimental conditions, the occurrence of cross-reactivity with T. canis was observed. However, in the case of co-infection of T. canis - S. mansoni, T. canis - S. venezuelensis and T. canis - T. crassiceps the production of anti-Toxocara antibodies was found at levels significantly lower than those found in mice infected with T. canis only. Co-infection with S. mansoni or S. venezuelensis showed lower mortality rates compared to what occurred in the animals with single infections. Results obtained in mice infected with T. canis and T. gondii showed significant differences between the mean levels of the optical densities of animals infected with T. canis and concomitantly infected with the protozoan only in the 23rd day p.i.

Pair approximation for a model of vertical and horizontal transmission of parasites.

We apply Stochastic Dynamics method for a differential equations model, proposed by Marc Lipsitch and collaborators (Proc. R. Soc. Lond. B 260, 321, 1995), for which the transmission dynamics of parasites occurs from a parent to its offspring (vertical transmission), and by contact with infected host (horizontal transmission). Herpes, Hepatitis and AIDS are examples of diseases for which both horizontal and vertical transmission occur simultaneously during the virus spreading. Understanding the role of each type of transmission in the infection prevalence on a susceptible host population may provide some information about the factors that contribute for the eradication and/or control of those diseases. We present a pair mean-field approximation obtained from the master equation of the model. The pair approximation is formed by the differential equations of the susceptible and infected population densities and the differential equations of pairs that contribute to the former ones. In terms of the model parameters, we obtain the conditions that lead to the disease eradication, and set up the phase diagram based on the local stability analysis of fixed points. We also perform Monte Carlo simulations of the model on complete graphs and Erdös-Rényi graphs in order to investigate the influence of population size and neighborhood on the previous mean-field results; by this way, we also expect to evaluate the contribution of vertical and horizontal transmission on the elimination of parasite. Pair Approximation for a Model of Vertical and Horizontal Transmission of Parasites.