Linear mixed model for weight analysis in mice infected by Trypanosoma cruzi

The use of linear mixed models for nested structure longitudinal data is called hierarchical linear modeling. Thismodeling takes into account the dependence of existing data within each level and between hierarchical levels. The process of modeling, estimating and analyzing diagnoses was illustrated through data on the weights of mice experimentally infected by Trypanosoma cruzi, divided into different treatment groups, with the purpose of verifying the evolution of their body weight as a result of usingdifferent types of biotherapeutics produced from Gallus gallus domesticus(chicken) serum to treat Trypanosoma cruzi. Through the model selection criteria AIC and BIC and the likelihood ratio test, a model was chosen to describe the data correctly. Model diagnoses were then performed by means of residual analysis for both levels and an analysis of influential observations to verify if any observations were signaled as influencing the fixed effects, the components of variance and the adjusted values. After the analysis, it was possible to notice that the observations that were signaled as influential had little impact on the Model chosen initially, so it was maintained, with no differences being evidenced between the treatments with the biotherapeutics tested; only the Time variable and the Random intercept were necessary to describe the weight of the mice.

Analyzing weight evolution in mice infected by Trypanosoma cruzi

Concerning the specificities of a longitudinal study, the trajectories of a subject's mean responses not always present a linear behavior, which calls for tools that take into account the non-linearity of individual trajectories and that describe them towards associating possible random effects with each individual. Generalized additive mixed models (GAMMs) have come to solve this problem, since, in this class of models, it is possible to assign specific random effects to individuals, in addition to rewriting the linear term by summing unknown smooth functions, not parametrically specified, then using the P-splines smoothing technique. Thus, this article aims to introduce this methodology applied to a dataset referring to an experiment involving 57 Swiss mice infected by Trypanosoma cruzi, which had their weights monitored for 12 weeks. The analyses showed significant differences in the weight trajectory of the individuals by treatment group; besides, the assumptions required to validate the model were met. Therefore, it is possible to conclude that this methodology is satisfactory in modeling data of longitudinal sort, because, with this approach, in addition to the possibility of including fixed and random effects, these models allow adding complex correlation structures to residuals.

Sympatry influence in the interaction of Trypanosoma cruzi with triatomine

Abstract INTRODUCTION: Trypanosoma cruzi, the etiologic agent of Chagas disease, is widely distributed in nature, circulating between triatomine bugs and sylvatic mammals, and has large genetic diversity. Both the vector species and the genetic lineages of T. cruzi present a varied geographical distribution. This study aimed to verify the influence of sympatry in the interaction of T. cruzi with triatomines. Methods: The behavior of the strains PR2256 (T. cruzi II) and AM14 (T. cruzi IV) was studied in Triatoma sordida (TS) and Rhodnius robustus (RR). Eleven fifth-stage nymphs were fed by artificial xenodiagnosis with 5.6 × 103 blood trypomastigotes/0.1mL of each T. cruzi strain. Every 20 days, their excreta were examined for up to 100 days, and every 30 days, the intestinal content was examined for up to 120 days, by parasitological (fresh examination and differential count with Giemsa-stained smears) and molecular (PCR) methods. Rates of infectivity, metacyclogenesis and mortality, and mean number of parasites per insect and of excreted parasites were determined. RESULTS: Sympatric groups RR+AM14 and TS+PR2256 showed higher values of the four parameters, except for mortality rate, which was higher (27.3%) in the TS+AM14 group. General infectivity was 72.7%, which was mainly proven by PCR, showing the following decreasing order: RR+AM14 (100%), TS+PR2256 (81.8%), RR+PR2256 (72.7%) and TS+AM14 (36.4%). CONCLUSIONS: Our working hypothesis was confirmed once higher infectivity and vector capacity (flagellate production and elimination of infective metacyclic forms) were recorded in the groups that contained sympatric T. cruzi lineages and triatomine species.

Evaluation of the reference value for the Montenegro skin test

The Montenegro skin test (MST) has good clinical applicability and low cost for the diagnosis of American tegumentary leishmaniasis (ATL). However, no studies have validated the reference value (5mm) typically used to discriminate positive and negative results. We investigated MST results and evaluated its performance using different cut-off points.

A pattern of adult involvement in highway acidentes / Um padrão de envolvimento dos adultos em acidentes rodoviários

This study aimed to identify the set of circumstances that contributed to the involvement of adults in traffic accidents. The study was of the cross-sectional type using secondary data. The patterns were identified through cluster analysis using a method called Hierarchical Ascendant Classification. Five classes were identified. Three classes involved males with minor injuries resulting from accidents between vehicles or vehicle-object, during the daytime and with dry road surface conditions. Two classes involved females, resulting in severe injuries, and were notable for occurring during the night and with a lower rate of use of seat belts. The findings of this study, especially in relation to the more serious accidents involving the female drivers, draw attention to this situation and point to a need for further studies involving these classes, which are increasingly common in traffic patterns.

Este estudo objetivou identificar o conjunto de circunstâncias que contribuíram para o envolvimento de adultos em acidentes de trânsito. Estudo descritivo transversal, utilizando dados secundários. Os padrões são identificados por meio de análise de grupo, através de um método chamado de Classificação Hierárquica Ascendente. Cinco classes foram identificadas. Três envolvendo homens resultando em agravos leves, a partir de acidentes entre veículos ou veículo-objeto, período diurno e em condições de pista seca. Duas envolvendo mulheres, resultando em gravidade, destacando-se a direção noturna e menor utilização do cinto de segurança. Os achados deste estudo, principalmente no que se refere aos acidentes graves envolvendo motoristas mulheres, chama a atenção e aponta novos estudos envolvendo estas, cada vez mais presentes no trânsito.

Toxoplasmosis: an examination of knowledge among health professionals and pregnant women in a municipality of the State of Paraná

Introduction The aim of this study was to investigate the knowledge of toxoplasmosis among professionals and pregnant women in the public health services in Paraná, Brazil. Methods A cross-sectional observational and transversal study of 80 health professionals (44 nurses and 36 physicians) and 330 pregnant women [111 immunoglobulin M (IgM)- and IgG-non-reactive and 219 IgG-reactive] was conducted in 2010. An epidemiological data questionnaire was administered to the professionals and to the pregnant women, and a questionnaire about the clinical aspects and laboratory diagnosis of toxoplasmosis was administered to the professionals. Results The participants frequently provided correct responses about prophylactic measures. Regarding the clinical and laboratory aspects, the physicians provided more correct responses and discussed toxoplasmosis with the pregnant women. The professionals had difficulty interpreting the avidity test results, and the physicians stated that they referred pregnant women with high-risk pregnancies to a county reference center. Of the professionals, 53 (91.4%) reported that they instructed women during prenatal care, but only 54 (48.6%) at-risk pregnant women and 99 (45.2%) women who were not at risk reported receiving information about preventive measures. The physicians provided verbal instructions to 120 (78.4%) women, although instructional materials were available in the county. The pregnant women generally lacked knowledge about preventive measures for congenital toxoplasmosis, but the at-risk pregnant women tended to respond correctly. Conclusions This study provides data to direct public health policies regarding the importance of updating the knowledge of primary care professionals. Mechanisms should be developed to increase public knowledge because prophylactic strategies are important for preventing congenital toxoplasmosis. .