Avian malaria co-infections confound infectivity and vector competence assays of Plasmodium homopolare.

Currently, there are very few studies of avian malaria that investigate relationships among the host-vector-parasite triad concomitantly. In the current study, we experimentally measured the vector competence of several Culex mosquitoes for a newly described avian malaria parasite, Plasmodium homopolare. Song sparrow (Melospiza melodia) blood infected with a low P. homopolare parasitemia was inoculated into a naïve domestic canary (Serinus canaria forma domestica). Within 5 to 10 days post infection (dpi), the canary unexpectedly developed a simultaneous high parasitemic infection of Plasmodium cathemerium (Pcat6) and a low parasitemic infection of P. homopolare, both of which were detected in blood smears. During this infection period, PCR detected Pcat6, but not P. homopolare in the canary. Between 10 and 60 dpi, Pcat6 blood stages were no longer visible and PCR no longer amplified Pcat6 parasite DNA from canary blood. However, P. homopolare blood stages remained visible, albeit still at very low parasitemias, and PCR was able to amplify P. homopolare DNA. This pattern of mixed Pcat6 and P. homopolare infection was repeated in three secondary infected canaries that were injected with blood from the first infected canary. Mosquitoes that blood-fed on the secondary infected canaries developed infections with Pcat6 as well as another P. cathemerium lineage (Pcat8); none developed PCR detectable P. homopolare infections. These observations suggest that the original P. homopolare-infected songbird also had two un-detectable P. cathemerium lineages/strains. The vector and host infectivity trials in this study demonstrated that current molecular assays may significantly underreport the extent of mixed avian malaria infections in vectors and hosts

Functional characterization of generalized Langevin equations

We present an exact functional formalism to deal with linear Langevin equations with arbitrary memory kernels and driven by any noise structure characterized through its characteristic functional. No others hypothesis are assumed over the noise, neither the fluctuation dissipation theorem. We found that the characteristic functional of the linear process can be expressed in terms of noise's functional and the Green function of the deterministic (memory-like) dissipative dynamics. This object allow us to get a procedure to calculate all the Kolmogorov hierarchy of the non-Markov process. As examples we have characterized through the 1-time probability a noise-induced interplay between the dissipative dynamics and the structure of different noises. Conditions that lead to non-Gaussian statistics and distributions with long tails are analyzed. The introduction of arbitrary fluctuations in fractional Langevin equations have also been pointed out

Reaction time to judge the temporal inequality of digits numbers

Several studies had consistently lighted mechanisms about the relation between spatial and numerical cognition; parallel to this, a separate research line begin to document similar relationships for the representation of time and quantity as well. However there are still few studies that explore cognitive mechanisms subserving this relation. Starting from the evidence of the SNARC effect (Dehaene et al., 1993), here we investigate about the presence of similar effect in the processing of temporal and numerical information. We studied the effects of numerical exposure when participants are asked to perform a visual detection task in which temporal information is explicitly or implicitly conveyed. The main result shows that, during explicit timing, low digits exposure improve reaction time in the judgment of shorter duration whereas big digits exposure improve reaction time in judgment of longer duration. No interaction between temporal and numerical information is documented when participants perform implicit timing task. Results suggest a role quantity exposure for timing task-dependent attentional orientation. 

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Feeding and defecation behavior of Triatoma rubida (Uhler, 1894) (Hemiptera: Reduviidae) under laboratory conditions, and its potential role as a vector of chagas disease in Arizona, USA

Chagas disease is caused by the parasite Trypanosoma cruzi, which is transmitted to humans by blood-sucking triatomine insects. This disease is endemic throughout Mexico and Central and South America, but only a few autochthonous cases have been reported in the United States, despite the fact that infected insects readily invade houses and feed on humans. Competent vectors defecate during or shortly after feeding so that infective feces contact the host. We thus studied the feeding and defecation behaviors of the prevalent species in southern Arizona, Triatoma rubida. We found that whereas defecation during feeding was frequent in females (93%), it was very rare in immature stages (3%), and absent in males. Furthermore, more than half of the immature insects that exhibited multiple feeding bouts (62%) defecated during interruptions of feeding, i.e., while likely on or near the host. These results indicate that T. rubida potentially could transmit T. cruzi to humans.Fil: Reisenman, Carolina Esther. University of Arizona; Estados UnidosFil: Gregory, Teresa. University of Arizona; Estados UnidosFil: Guerenstein, Pablo Gustavo. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; ArgentinaFil: Hildebrand, John. University of Arizona; Estados Unido

A Systems Theory Perspective

Aktualisierung: Am 12. Oktober 2018 wurde die digitale Version des Buchbeitrags um den fehlenden Teil (Seiten 53-66) ergänzt

A GIS-based multi-criteria evaluation approach to map Rift Valley fever risk areas in Europe

Rift Valley fever (RVF) is a severe mosquito-borne disease affecting domestic ruminants and humans, caused by a Phlebovirus (Bunyaviridae). RVF virus (RVFV) infection may result either from mosquito bites or contact with a viremic animal, or exposure to body fluids. Recently its distribution enlarged, threatening northern Africa, a large outbreak occurred in northern Mauritania in 2010, Middle East and Europe. Even if the probability of introduction and large-scale spread of RVFV in Europe is very low, localized RVF outbreaks may occur in areas where population of ruminants and potential vectors are present. The goal of this study was to identify European suitable areas for RVF transmission. We focused on the risk of transmission of RVFV to three main European potential hosts, i.e. cattle, sheep and goats, considering only the vectorial transmission. Very few is known about European mosquito competency. Based on a literature review, five mosquito species belonging to Culex and Aedes genera, present in Europe and likely to play a role in RVFV transmission in case of virus introduction were identified: Culex (Culex) pipiens, Culex (Culex) theileri, Aedes (Aedimorphus) vexans vexans, Aedes (Ochlerotatus) caspius and Aedes (Stegomyia) albopictus. We first modelled the geographic distribution of each of these five species, based on expert knowledge and using land cover (Corine Land cover database) and elevation as proxy of mosquito presence. Then, the risk of RVFV transmission was modelled using a Multi-Criteria Evaluation (MCE) approach, integrating available experimental data on vector competence, expert knowledge on abundance, host density data and literature knowledge on host sensitivity. A sensitivity analysis was performed to assess the robustness of the results with respect to expert choices in the selection, weights assignments and combination of the different factors. The resulting maps include i) five maps of vector distribution, one for each potential vector species; ii) a map of suitable areas for vectorial transmission of RVFV considering the presence of at least one of the five mosquito species, their potential competency and abundance; and iii) a map of the risk of vector- borne transmission to cattle, sheep and goats. As expected, the resulting RVFV risk maps highlighted a strong spatial heterogeneity throughout Europe. For validation, mosquito distribution maps were compared to mosquito collection data from Italy, showing a good agreement between modelled presence probability and observed presence or absence of each species. The same validation should be performed for other European countries, at least distinguishing the main European regions, i.e. Southern, Northern and Eastern Europe. Additionally, and as far as Africa is concerned, it is well known that sheep are more sensitive than goats that are themselves more sensitive than cattle. In the absence of contradictory evidence for Europe, we considered that the three main hosts were equally sensitive to the virus. This assumption need to be validated by laboratory experiments. Lastly, we did not take into account the direct transmission which is supposed to substantially support the transmission during outbreaks in Africa. The next step could be to improve this model including a direct transmission term when available. As conclusion, we found that MCE offered a valuable framework and flexible tool for the mapping of areas at risk for the transmission of a pathogen which is absent from a region. It helped identifying gaps in knowledge of the transmission of RVFV in Europe. In particular, further lab experiments are needed - as very little is known about the competence of mosquito European species, we used estimations available for African species to estimate the role of each species as potential vectors, but this extrapolation is uncertain. Given the absence of relevant models for Europe, the cost of active surveillance and the numerous potential entry ways for t

Biologically Informed Individual-Based Network Model for Rift Valley Fever in the US and Evaluation of Mitigation Strategies

Citation: Scoglio, C. M., Bosca, C., Riad, M. H., Sahneh, F. D., Britch, S. C., Cohnstaedt, L. W., & Linthicum, K. J. (2016). Biologically Informed Individual-Based Network Model for Rift Valley Fever in the US and Evaluation of Mitigation Strategies. Plos One, 11(9), 26. doi:10.1371/journal.pone.0162759Rift Valley fever (RVF) is a zoonotic disease endemic in sub-Saharan Africa with periodic outbreaks in human and animal populations. Mosquitoes are the primary disease vectors; however, Rift Valley fever virus (RVFV) can also spread by direct contact with infected tissues. The transmission cycle is complex, involving humans, livestock, and multiple species of mosquitoes. The epidemiology of RVFV in endemic areas is strongly affected by climatic conditions and environmental variables. In this research, we adapt and use a network-based modeling framework to simulate the transmission of RVFV among hypothetical cattle operations in Kansas, US. Our model considers geo-located livestock populations at the individual level while incorporating the role of mosquito populations and the environment at a coarse resolution. Extensive simulations show the flexibility of our modeling framework when applied to specific scenarios to quantitatively evaluate the efficacy of mosquito control and livestock movement regulations in reducing the extent and intensity of RVF outbreaks in the United States

Canine Trypanosoma cruzi infection in the Bolivian Chaco

A cross-sectional study on Trypanosoma cruzi was carried out in 2013 to evaluate the role of dogs as possible source of infection for humans in two rural communities of the highly endemic Bolivian Chaco (Bartolo, Chuquisaca Department, n = 57 dogs; and Ivamirapinta, Santa Cruz Department, n = 48 dogs). Giemsa-stained thick and thin smears, rapid immunochromatographic test (ICT) (Chagas Quick test, Cypress Diagnostic, Belgium) and polymerase chain reaction for T. cruzi on dried blood spots were performed. All smears proved negative by microscopic examination, whereas 23/103 (22%) were positive by ICT and 5/105 (5%) blood samples contained T. cruzi DNA, evidencing the potential role of dogs in the domestic transmission of the parasite