Egg parasitoid wasps as natural enemies of the neotropical stink bug Dichelops melacanthus

The objective of this work was to determine the potential of five species of Scelionidae wasps - Telenomus podisi, Trissolcus basalis, Trissolcus urichi, Trissolcus teretis and Trissolcus brochymenae - as natural enemies of the neotropical stink bug Dichelops melacanthus, and to determine if the presence of eggs of other stink bug species influences the parasitism and development of the parasitoids. Two kinds of experiments were done in laboratory: without choice of hosts (eggs of D. melacanthus) and with choice (eggs of D. melacanthus and of Euschistus heros). Biological parameters, including proportion of parasitism, immature survivorship, progeny sex ratio, immature stage development period, and host preference were recorded. All the evaluated parasitoids can parasitize and develop on D. melacanthus eggs. The first choice of eggs did not influence the proportion of D. melacanthus eggs parasitized by Tr. basalis, Tr. teretis or Tr. brochymenae. However, D. melacanthus eggs as the first choice of Te. podisi and Tr. urichi increased, respectively, 9 and 14 times the chance for parasitism on eggs of this species. Behavioral and ecological aspects of parasitoids should be considered prior to their use in biological control programs.

Biology and parasitic potential of Doryctobracon areolatuson Anastrepha fraterculus larvae

The objective of this work was to study the biology and parasitic potential of Doryctobracon areolatus on larvae of Anastrepha fraterculus. The egg-adult period, the sex ratio, the longevity, the pupal viability, and the parasitism rate of D. areolatus were determined in laboratory, using A. fraterculus as host. The parasitoid development from oviposition to adult emergence required 25.00±1.70 days, the sex ratio was 0.62±0.09, and the mean longevity was 16.36±3.62 days for males and 10.24±1.71 days for females. The mean parasitism rate was 53.50±8.93%, varying from 41.60 to 68.60%, which shows the potential of this parasitoid for biological control of A. fraterculus.

Parasitic fauna in hybrid tambacu from fish farms

The objective of this work was to evaluate the parasitic fauna of hybrid tambacu (Colossoma macropomum x Piaractus mesopotamicus) from fish farms and the host-parasite relationship. A hundred and fourteen fish were collected from four fish farms in Macapá, in the state of Amapá, Brazil, 80.7% of which were infected by: Ichthyophthirius multifiliis (Ciliophora); Piscinoodinium pillulare (Dinoflagellida); Anacanthorus spatulatus, Notozothecium janauachensis, and Mymarothecium viatorum (Monogenoidea); Neoechinorhynchus buttnerae (Acanthocephala); Cucullanus colossomi (Nematoda); Perulernaea gamitanae (Lernaeidae); and Proteocephalidae larvae (Cestoda). A total of 8,136,252 parasites were collected from the examined fish. This is the first record of N. buttnerae, C. colossomi, N. janauachensis, M. viatorum, and Proteocephalidae for hybrid tambacu in Brazil. Ichthyophthirius multifiliis was the most prevalent parasite, whereas endohelminths were the less. A positive correlation was observed between number of I. multifiliis and total length and weight of fish, as well as between number of P. gamitanae and total length. The infection by I. multifiliis had association with the parasitism by Monogenoidea. Low water quality contributes to high parasitism of hybrid tambacu by ectoparasites, which, however, does not influence the relative condition factor of fish.

Development of new dissolution test and HPLC-RP method for anti-parasitic ornidazole coated tablets

This work aimed the development and validation of a new dissolution test for ornidazole coated tablets. The dissolution conditions were determined after testing Sink conditions, dissolution medium, apparatus, stirring speed, 24 h stability and medium filtration influence. The best conditions were paddle at a stirring speed of 75 rpm and 900 mL of 0.1 M HCl. A new HPLC quantification method was developed and validated. The dissolution test and quantification method showed to be adequate for their purposes and could be applied for quality control of ornidazole coated tablets, since there is no official monograph.

Nematicidal effect of volatile organic compounds (VOCs) on the plant-parasitic nematode Meloidogyne javanica

Previous studies have demonstrated that volatile organic compounds (VOCs), produced by the yeast Saccharomyces cerevisiae, were able to inhibit the development of phytopathogenic fungi. In this context, the nematicidal potential of the synthetic mixture of VOCs, constituted of alcohols and esters, was evaluated for the control of the root-knot nematode Meloidogyne javanica, which causes losses to crops of high economic value. The fumigation of substrate containing second-stage juveniles with VOCs exhibited nematicidal effect higher than 30% for the lowest concentration tested (33.3 µL g-1 substrate), whereas at 66.6 and 133.3 µL g-1 substrate, the nematode mortality was 100%. The present results stimulate other studies on VOCs for nematode management.

Inefficacy of albendazole sulphoxide and ivermectin for the treatment of bovine parasitic otitis caused by rhabditiform nematodes

The purpose of this study was to evaluate the efficacy of orally administered albendazole sulphoxide and pour-on ivermectin for the treatment of bovine parasitic otitis caused by rhabditiform nematodes. Eighteen Gyr cows presenting clinical otitis were divided in three groups with six animals each. The first one did not receive any treatment (control group). The second one was treated with 0.5% pour-on ivermectin, 500µg/kg of body weight, and the third group was treated with oral 6% albendazole sulphoxide, at 6.0mg/kg. Both ear canals of each animal were reexamined on days 7 and 21 post treatment. The animals in the control group remained infected throughout the days of observation. Ivermectin treatment did not show effectiveness on days 7 or 21 post treatment. The albendazole sulphoxide treatment had an efficacy of 16.7 and 25% on days 7 and 21, respectively. Further studies are required to assess an effective treatment for this parasitic disease, especially via alternative administration routes, because of its significant impact on Bos taurus indicus cattle breeding in Tropical and Subtropical Regions.

Turgida turgida (Nematoda: Physalopteridae) parasitic in white-bellied opossum, Didelphis albiventris (Marsupialia: Didelphidae), state of Mato Grosso do Sul, Brazil

Turgida turgida have been largely reported parasitizing Didelphis species in North and South America based on light microscopy observation. However, the features that differentiate T. turgida from other physalopterid species should be observed using scanning electron microscopy (SEM). A female white-bellied opossum, Didelphis albiventris, arrived dead at the Centro de Reabilitação de Animais Silvestres (CRAS) in the municipality of Campo Grande, state of Mato Grosso do Sul, Brazil. During the necropsy, adult nematodes were collected from stomach and intestine. The nematodes were determined to be adult specimens and submitted to SEM for the species determination. This is the first report of T. turgida confirmed by SEM in the Neotropical region and the first report in an urban area in the state of Mato Grosso do Sul, Brazil.

Farmers' perception about parasitic otitis in Gyr breed from three states of Brazil

This study aimed to know the perception of Gir cattle breeders and farm employees about parasitic otitis and practices regarding methods of treatment and control. A questionnaire was applied on specific topics about the disease. The results showed that the otitis occurred in 25 (89.3%) of the 28 farms studied, where the main etiologic agents were the nematodes Rhabditis spp. The majority of the farmers regarded the disease as a serious problem, mainly in cattle older than eight years of age. About half of the respondents did not observe a correlation between season and prevalence of the otitis; however, 30.8% reported an increase of its incidence during the rainy season. In addition to various methods and products for the rhabditiosis treatment, a lack of standardized preventive or curative protocols was found, suggesting insufficient knowledge about control of the disease.

Variability in the fecal egg count and the parasitic burden of hair sheep after grazing in nematode infected paddocks

This study aimed to evaluate the variability in the fecal egg count (FEC) and the parasitic burden of naive hair sheep after grazing in nematode infected paddocks. The research was carried out in Tabasco, Mexico, during two periods (August and December). In each period 32 lambs were grazed for one month on African star grass (Cynodon plectostachyus) contaminated with gastrointestinal parasitic nematodes. FEC, packed cell volume (PCV) and body weight (BW) were recorded. Gastrointestinal worms were recovered at necropsy. Data were analyzed with the MIXED procedure of SAS using a model of repeated measurements over time. A higher number of Haemonchus contortus worms was found in December (2814±838) than in August (1166±305). The opposite occurred with Cooperia curticei (2167±393 and 3638±441, respectively). The FEC and correlation coefficient in respect to the worm burden were higher in December (6516 ± 1599, r=0.83, respectively) than in August (4364±771, r=0.44, respectively). A high variability in resistance-susceptibility to gastrointestinal nematodes (GIN) occurred in Katahdin × Pelibuey lambs after grazing.

Parasitic infections in germfree animals

The association of vertebrate hosts with the indigenous microbiota and its effect on the response to infections has long been a subject of scientific curiosity. From the first theory supported by Louis Pasteur that life would be impossible in the absence of associated microorganisms to the development of germfree mammals for research, a lot was learned about how the normal microbiota influences the environment in which pathogens may find themselves. In the present review, we attempt to summarize the more recent results from our group and others on the influence of the normal microbiota on the outcome of parasitic infections. Our results and those of others point to a complex relationship between the mammalian system and its indigenous microbiota, leading to greater resistance to some infections and enhanced susceptibility to others

The use of confocal laser scanning microscopy to analyze the process of parasitic protozoon-host cell interaction

In this communication we review the results obtained with the confocal laser scanning microscope to characterize the interaction of epimastigote and trypomastigote forms of Trypanosoma cruzi and tachyzoites of Toxoplasma gondii with host cells. Early events of the interaction process were studied by the simultaneous localization of sites of protein phosphorylation, revealed by immunocytochemistry, and sites of actin assembly, revealed by the use of labeled phaloidin. The results obtained show that proteins localized in the interaction sites are phosphorylated. The process of formation of the parasitophorous vacuole was monitored by labeling the host cell surface with fluorescent probes for lipids (PKH26), proteins (DTAF) and sialic acid (FITC-thiosemicarbazide) before interaction with the parasites. Evidence was obtained indicating transfer of components of the host cell surface to the parasite surface in the beginning of the interaction process. We also analyzed the distribution of cytoskeletal structures (microtubules and microfilaments visualized with specific antibodies), mitochondria (visualized with rhodamine 123), the Golgi complex (visualized with C6-NBD-ceramide) and the endoplasmic reticulum (visualized with anti-reticulin antibodies and DIOC6) during the evolution of intracellular parasitism. The results obtained show that some, but not all, structures change their position during evolution of the intracellular parasitism.

Differential in vitro pathogenicity of predatory fungi of the genus Monacrosporium for phytonematodes, free-living nematodes and parasitic nematodes of cattle

In vitro tests were carried out on the pathogenicity of nine isolates of the predatory fungi of the genus Monacrosporium (5 M. sinense isolates, 3 M. appendiculatum and 1 M. thaumasium isolate) for a phytonematode (second stage juveniles from Meloidogyne incognita, race 3), a free-living nematode (Panagrellus spp), and two gastrointestinal parasitic nematodes of cattle (infective larvae of Cooperia punctata and Haemonchus placei). A suspension containing 2,000 nematodes from each species was added to Petri dishes containing fungi and grown on 2% water-agar medium at 25oC in the dark for up to 7 days. The dishes were examined every other day for 7 days and predation-free nematodes were counted. The results showed that the free-living nematodes, Panagrellus spp, were the most susceptible (P<0.05), followed by the phytonematode M. incognita, while the controls were ³98.5% viable. However, a variable susceptibility of the nematodes to different fungi was observed. This indicates that the use of predatory fungi for the environmental control of nematodes will be limited by the multiplicity of nematodes in the environment and their differential susceptibility to fungal isolates of the same genus.

Apoptosis in parasites and parasite-induced apoptosis in the host immune system: a new approach to parasitic diseases

Apoptosis, a form of programmed cell death (PCD), has been described as essential for normal organogenesis and tissue development, as well as for the proper function of cell-renewal systems in adult organisms. Apoptosis is also pivotal in the pathogenesis of several different diseases. In this paper we discuss, from two different points of view, the role of apoptosis in parasitic diseases. The description of apoptotic death in three different species of heteroxenic trypanosomatids is reviewed, and considerations on the phylogenesis of apoptosis and on the eventual role of PCD on their mechanism of pathogenesis are made. From a different perspective, an increasing body of evidence is making clear that regulation of host cell apoptosis is an important factor on the definition of a host-pathogen interaction. As an example, the molecular mechanisms by which Trypanosoma cruzi is able to induce apoptosis in immunocompetent cells, in a murine model of Chagas' disease, and the consequences of this phenomenon on the outcome of the experimental disease are discussed.

Anti-parasitic action and elimination of intracellular Toxoplasma gondii in the presence of novel thiosemicarbazone and its 4-thiazolidinone derivatives

Toxoplasma, which infects all eukaryotic cells, is considered to be a good system for the study of drug action and of the behavior of infected host cells. In the present study, we asked if thiosemicarbazone derivatives can be effective against tachyzoites and which morphological and ultrastructural features of host cells and parasites are associated with the destruction of Toxoplasma. The compounds were tested in infected Vero cell culture using concentration screens (0.1 to 20 mM). The final concentration of 1 mM was chosen for biological assay. The following results were obtained: 1) These new derivatives decreased T. gondii infection with an in vitro parasite IC50% of 0.2-0.7 mM, without a significant effect on host cells and the more efficient compounds were 2, 3 (thiosemicarbazone derivatives) and 4 (thiazolidinone derivative); 2) The main feature observed during parasite elimination was continuous morphological disorganization of the tachyzoite secretory system, progressive organelle vesiculation, and then complete disruption; 3) Ultrastructural assays also revealed that progressive vesiculation in the cytoplasm of treated parasites did not occur in the host cell; 4) Vesiculation inside the parasite resulted in death, but this feature occurred asynchronously in different intracellular tachyzoites; 5) The death and elimination of T. gondii was associated with features such as apoptosis-like stage, acidification and digestion of parasites into parasitophorous vacuoles. Our results suggest that these new chemical compounds are promising for the elimination of intracellular parasites by mainly affecting tachyzoite development at 1 mM concentration for 24 h of treatment.

Malaria transmission model for different levels of acquired immunity and temperature-dependent parameters (vector)

OBJECTIVE: Describe the overall transmission of malaria through a compartmental model, considering the human host and mosquito vector. METHODS: A mathematical model was developed based on the following parameters: human host immunity, assuming the existence of acquired immunity and immunological memory, which boosts the protective response upon reinfection; mosquito vector, taking into account that the average period of development from egg to adult mosquito and the extrinsic incubation period of parasites (transformation of infected but non-infectious mosquitoes into infectious mosquitoes) are dependent on the ambient temperature. RESULTS: The steady state equilibrium values obtained with the model allowed the calculation of the basic reproduction ratio in terms of the model's parameters. CONCLUSIONS: The model allowed the calculation of the basic reproduction ratio, one of the most important epidemiological variables.