The improbable transmission of Trypanosoma cruzi to human: the missing link in the dynamics and control of Chagas disease

Chagas disease has a major impact on human health in Latin America and is becoming of global concern due to international migrations. Trypanosoma cruzi, the etiological agent of the disease, is one of the rare human parasites transmitted by the feces of its vector, as it is unable to reach the salivary gland of the insect. This stercorarian transmission is notoriously poorly understood, despite its crucial role in the ecology and evolution of the pathogen and the disease. The objective of this study was to quantify the probability of T. cruzi vectorial transmission to humans, and to use such an estimate to predict human prevalence from entomological data. We developed several models of T. cruzi transmission to estimate the probability of transmission from vector to host. Using datasets from the literature, we estimated the probability of transmission per contact with an infected triatomine to be 5.8x10(-4) (95%CI: [2.6; 11.0] x 10(-4)). This estimate was consistent across triatomine species, robust to variations in other parameters, and corresponded to 900-4,000 contacts per case. Our models subsequently allowed predicting human prevalence from vector abundance and infection rate in 7/10 independent datasets covering various triatomine species and epidemiological situations. This low probability of T. cruzi transmission reflected well the complex and unlikely mechanism of transmission via insect feces, and allowed predicting human prevalence from basic entomological data. Although a proof of principle study would now be valuable to validate our models' predictive ability in an even broader range of entomological and ecological settings, our quantitative estimate could allow switching the evaluation of disease risk and vector control program from purely entomological indexes to parasitological measures, as commonly done for other major vector borne diseases. This might lead to different quantitative perspectives as these indexes are well known not to be proportional one to another

Medidas e proporções antropométricas orofaciais de crianças respiradoras orais Anthropometric orofacial measurements and proportions in mouth breathing children

OBJETIVO: Descrever as medidas e proporções orofaciais de crianças respiradoras orais e comparar a média do lado direito da face com a média do lado esquerdo da face, segundo a idade. MÉTODOS: Participaram 100 crianças, de ambos os sexos, com idades entre sete anos e 11 anos e 11 meses, leucodermas, em dentição mista, com diagnóstico de respiração oral. As crianças foram submetidas à avaliação antropométrica, sendo que as medidas orofaciais obtidas foram lábio superior, lábio inferior, filtro, terço superior da face, terço médio da face, terço inferior da face e lados da face. O instrumento utilizado foi o paquímetro eletrônico digital da marca Starrett, Série 727. RESULTADOS: Não houve diferença estatisticamente significativa entre as médias das medidas antropométricas orofaciais das crianças respiradoras orais, segundo a idade, com exceção do terço médio da face e dos lados da face. Não houve diferença estatisticamente significativa entre as médias das proporções orofaciais das crianças respiradoras orais, com exceção da proporção entre o terço superior da face e o terço médio da face. Não houve diferença estatisticamente significativa entre as médias dos lados da face, segundo a idade. CONCLUSÕES: Não houve diferença estatisticamente entre a maioria das médias das medidas e proporções orofaciais de crianças respiradoras orais, segundo a idade.<br>PURPOSE: To describe the orofacial measurements and proportions of mouth breathing children and to compare the average of the right side of the face to the average of the left side of the face, according to age. METHODS: One hundred children of both sexes, with ages ranging from seven to 11 years and 11 months, leukoderms, in mixed dentition period and with mouth breathing diagnosis participated in the study. The children were submitted to anthropometric assessment, and the orofacial measurements obtained were upper lip, lower lip, philtrum, upper face, middle face, lower face and sides of the face. The instrument used was the electronic digital sliding caliper Starrett Series 727. RESULTS: There was statistically no difference among the averages of the anthropometric orofacial measurements of mouth breathing children, according to age, with exception of the middle face and the sides of the face. There was also no difference among the averages of the orofacial proportions of mouth breathing children, with exception of the proportion between upper face and middle face, and between the averages of the sides of the face, according to age. CONCLUSIONS: Statistically, no differences were found among most of the averages of the orofacial measurements and proportions of mouth breathing children, according to age

Abiotic and biotic controls of cryptobenthic fish assemblages across a Caribbean seascape

The majority of fish studies on coral reefs consider only non-cryptic species and, despite their functional importance, data on cryptic species are scarce. This study investigates inter-habitat variation in Caribbean cryptobenthic fishes by re-analysing a comprehensive data set from 58 rotenone stations around Buck Island, U.S. Virgin Islands. Boosted regression trees were used to associate the density and diversity of non-piscivorous cryptobenthic fishes, both in the entire data set and on reef habitats alone, with 14 abiotic and biotic variables. The study also models the habitat requirements of the three commonest species. Dead coral cover was the first or second most important variable in six of the eight models constructed. For example, within the entire data set, the number of species and total fish density increased approximately linearly with increasing dead coral cover. Dead coral was also important in multivariate analyses that discriminated 10 assemblages within the entire data set. On reef habitats, the number of species and total fish density increased dramatically when dead coral exceeded ~55 %. Live coral cover was typically less important for explaining variance in fish assemblages than dead coral, but live corals were important for maintaining high fish diversity. Coral species favoured by cryptobenthic species may be particularly susceptible to mortality, but dead coral may also provide abundant food and shelter for many fishes. Piscivore density was a key variable in the final models, but typically increased with increasing cryptobenthic fish diversity and abundance, suggesting both groups of fishes are responding to the same habitat variables. The density of territorial damselfishes reduced the number of cryptobenthic fish species on reef habitats. Finally, habitats delineated by standard remote sensing techniques supported distinct cryptobenthic fish assemblages, suggesting that such maps can be used as surrogates of general patterns of cryptic fish biodiversity in conservation planning