Follow up estimation of Aedes aegypti entomological parameters and mathematical modellings

The dengue virus is a vector-borne disease transmitted by mosquito Aedes aegypti and the incidence is strongly influenced by temperature and humidity which vary seasonally. To assess the effects of temperature on dengue transmission, mathematical models are developed based on the population dynamics theory. However, depending on the hypotheses of the modelling, different outcomes regarding to the risk of epidemics are obtained. We address this question comparing two simple models supplied with model's parameters estimated from temperature-controlled experiments, especially the entomological parameters regarded to the mosquito's life cycle in different temperatures. Once obtained the mortality and transition rates of different stages comprising the life cycle of mosquito and the oviposition rate, we compare the capacity of vector reproduction (the basic offspring number) and the risk of infection (basic reproduction number) provided by two models. The extended model, which is more realistic, showed that both mosquito population and dengue risk are situated at higher values than the simplified model, even that the basic offspring number is lower.     

Triplet entropy analysis of hemagglutinin and neuraminidase sequences measures influenza virus phylodynamics

The influenza virus has been a challenge to science due to its ability to withstand new environmental conditions. Taking into account the development of virus sequence databases, computational approaches can be helpful to understand virus behavior over time. Furthermore, they can suggest new directions to deal with influenza. This work presents triplet entropy analysis as a potential phylodynamic tool to quantify nucleotide organization of viral sequences. The application of this measure to segments of hemagglutinin (HA) and neuraminidase (NA) of H1N1 and H3N2 virus subtypes has shown some variability effects along timeline, inferring about virus evolution. Sequences were divided by year and compared for virus subtype (H1N1 and H3N2). The nonparametric Mann–Whitney test was used for comparison between groups. Results show that differentiation in entropy precedes differentiation in GC content for both groups. Considering the HA fragment, both triplet entropy as well as GC concentration show intersection in 2009, year of the recent pandemic. Some conclusions about possible flu evolutionary lines were drawn.     

Association of insecticide use and alteration on Aedes aegypti susceptibility status

Dengue and dengue hemorrhagic fever, vector-borne diseases transmitted by the mosquito Aedes aegypti, are presently important public health problems in Brazil. As the strategy for disease control is based on vector control through the use of insecticides, the development of resistance is a threat to programs efficacy. The objective of this study was to compare the Aedes aegypti susceptibility in nine vector populations from the state of S?o Paulo and seven from Northeast region of Brazil, since there was a difference on group of insecticide used between the areas. Bioassays with larvae and adult were performed according to the World Health Organization methods. The results showed higher resistance levels to organophosphates group in populations from the Northeast region where this group was used for both larvae and adult control than in S?o Paulo where organophosphates were used for larvae and pyretroids for adult control. Resistance to pyretroids in adults was widespread in S?o Paulo after ten years of use of cypermethrin while in vector populations from the Northeast region it was punctual. The difference in resistance profile between the areas is in accordance to the group of insecticide used.     

Alpha-synuclein pore forming activity upon membrane association

Alpha-synuclein is a natively unfolded protein widely expressed in neurons at the presynaptic level. It is linked to Parkinson's disease by two lines of evidence: amyloid fibrils of the protein accumulate in patients' brains and three genetic mutants cause autosomal dominant forms of the disease. The biological role of the protein and the mechanisms involved in the etiopathogenesis of Parkinson's disease are still unknown. Membrane binding causes the formation of an amphipathic alpha-helix, which lies on the surface without crossing the bilayer. Recent observations however reported that the application of a voltage induces a pore-like activity of alpha-synuclein. This study aims to characterize the pore forming activity of the protein starting from its monomeric form. In particular, experiments with planar lipid membranes allowed recording of conductance activity bursts with a defined and reproducible fingerprint. Additional experiments with deletion mutants and covalently bound alpha-synuclein dimers were performed to understand both pore assembly and stoichiometry. The information acquired allowed formulation of a model for pore formation at different conductance levels.     

Resistance of Aedes aegypti from the state of São Paulo,Brazil, to organophosphates insecticides

Since the reintroduction of Aedes aegypti in the state of S o Paulo, in the middle of the 1980-decade, organophosphate insecticides are being used to control the dengue vector. In 1996, an annual program for monitoring the susceptibility of Ae. aegypti to the insecticides was implemented. Some of the results of this monitoring program are presented. Ae. aegypti populations from ten localities have been submitted to bioassays with the diagnostic dose of temephos and fenitrothion. Only two (Mar lia and Presidente Prudente) remain susceptible to both insecticides and one (Santos) exhibits true resistance. Ae. aegypti from the remaining localities showed an incipient altered susceptibility. Resistance ratios varied from 1.2 to 2.9 for temephos and from 1.5 to 3.2 to fenitrothion, indicating moderate levels of resistance. Biochemical assays did not detect alterations in the enzyme acetilcholinesterase, but indicated that resistance is associated with esterases.     

A new Penicillium echinulatum strain with faster cellulase secretion obtained using hydrogen peroxide mutagenesis and screening with 2-deoxyglucose

Aims: The aim of this study is to improve cellulase production and secretion by Penicillium echinulatum using mutagenesis and selection in association with microfermentation and microanalysis methods. Methods and Results: A new genetic variant was isolated from strain 9A02S1 and named S1M29. It was obtained by mutagenesis with H₂O₂ and two screening steps, which involved selection in Petri dishes using the medium supplemented with 2‐deoxyglucose and microfermentations in submerged culture. The mutant showed higher cellulase productivity than 9A02S1 based on the Filter Paper Activity assay and endoglucanase; the peak activities for these enzymes were reached significantly faster than for the parent strain. Conclusions: The mutant obtained after mutagenesis and selection could produce and secrete cellulase faster than the parent strain. Significance and Impact of the Study: Mutagenesis followed by selection is a useful tool for rapidly generating new cellulase‐producing phenotypes in fungi. Faster production and higher titers of cellulases in mutant strains contribute to reduce the production costs for enzymatic complexes that hydrolyse lignocellulose residues and form fermented syrups, thus contributing to the economic production of bioethanol.     

Larval Breeding Sites of Lutzomyia longipalpis (Diptera: Psychodidae) in Visceral Leishmaniasis Endemic Urban Areas in Southeastern Brazil

Background

The scarcity of information on the immature stages of sand flies and their preferred breeding sites has resulted in the focus of vectorial control on the adult stage using residual insecticide house-spraying. This strategy, along with the treatment of human cases and the euthanasia of infected dogs, has proven inefficient and visceral leishmaniasis continues to expand in Brazil. Identifying the breeding sites of sand flies is essential to the understanding of the vector''s population dynamic and could be used to develop novel control strategies.

Methodology/Principal finding

In the present study, an intensive search for the breeding sites of Lutzomyia longipalpis was conducted in urban and peri-urban areas of two municipalities, Promissão and Dracena, which are endemic for visceral leishmaniasis in São Paulo State, Brazil. During an exploratory period, a total of 962 soil emergence traps were used to investigate possible peridomiciliary breeding site microhabitats such as: leaf litter under tree, chicken sheds, other animal sheds and uncovered debris. A total of 160 sand flies were collected and 148 (92.5%) were L. longipalpis. In Promissão the proportion of chicken sheds positive was significantly higher than in leaf litter under trees. Chicken shed microhabitats presented the highest density of L. longipalpis in both municipalities: 17.29 and 5.71 individuals per square meter sampled in Promissão and Dracena respectively. A contagious spatial distribution pattern of L. longipalpis was identified in the emergence traps located in the chicken sheds.

Conclusion

The results indicate that chicken sheds are the preferential breeding site for L. longipalpis in the present study areas. Thus, control measures targeting the immature stages in chicken sheds could have a great effect on reducing the number of adult flies and consequently the transmission rate of Leishmania (Leishmania) infantum chagasi.