ABSTRACT
Nationwide disease surveillance at a high spatial resolution is desired for many infectious diseases, including Visceral Leishmaniasis. Statistical and mathematical models using data collected from surveillance activities often use a spatial resolution and scale either constrained by data availability or chosen arbitrarily. Sensitivity of model results to the choice of spatial resolution and scale is not, however, frequently evaluated. This study aims to determine if the choice of spatial resolution and scale are likely to impact statistical and mathematical analyses. Visceral Leishmaniasis in Brazil is used as a case study. Probabilistic characteristics of disease incidence, representing a likely outcome in a model, are compared across spatial resolutions and scales. Best fitting distributions were fit to annual incidence from 2004 to 2014 by municipality and by state. Best fits were defined as the distribution family and parameterization minimizing the sum of absolute error, evaluated through a simulated annealing algorithm. Gamma and Poisson distributions provided best fits for incidence, both among individual states and nationwide. Comparisons of distributions using Kullback-Leibler divergence shows that incidence by state and by municipality do not follow distributions that provide equivalent information. Few states with Gamma distributed incidence follow a distribution closely resembling that for national incidence. These results demonstrate empirically how choice of spatial resolution and scale can impact mathematical and statistical models.
Subject(s)
Epidemiological Monitoring , Leishmaniasis, Visceral/epidemiology , Brazil/epidemiology , Humans , Incidence , Spatial AnalysisABSTRACT
BACKGROUND: Visceral leishmaniasis (VL) is a neglected tropical disease of public health relevance in Brazil. To prioritize disease control measures, the Secretaria de Vigilância em Saúde of Brazil's Ministry of Health (SVS/MH) uses retrospective human case counts from VL surveillance data to inform a municipality-based risk classification. In this study, we compared the underlying VL risk, using a spatiotemporal explicit Bayesian hierarchical model (BHM), with the risk classification currently in use by the Brazil's Ministry of Health. We aim to assess how well the current risk classes capture the underlying VL risk as modelled by the BHM. METHODS: Annual counts of human VL cases and the population at risk for all Brazil's 5564 municipalities between 2004 and 2014 were used to fit a relative risk BHM. We then computed the predicted counts and exceedence risk for each municipality and classified them into four categories to allow comparison with the four risk categories by the SVS/MH. RESULTS: Municipalities identified as high-risk by the model partially agreed with the current risk classification by the SVS/MH. Our results suggest that counts of VL cases may suffice as general indicators of the underlying risk, but can underestimate risks, especially in areas with intense transmission. CONCLUSION: According to our BHM the SVS/MH risk classification underestimated the risk in several municipalities with moderate to intense VL transmission. Newly identified high-risk areas should be further evaluated to identify potential risk factors and assess the needs for additional surveillance and mitigation efforts.
Subject(s)
Leishmaniasis, Visceral/epidemiology , Bayes Theorem , Brazil/epidemiology , Cities , Humans , Neglected Diseases/epidemiology , Public Health , Retrospective Studies , Risk Factors , Spatio-Temporal AnalysisABSTRACT
Este trabalho teve como objetivo mensurar as atividades das enzimas fosfatase alcalina (FA) e lactato desidrogenase (LDH)no fluido abdominal e no soro de cães, estabelecendo sua utilidade para diferenciação dos fluidos classificados comotransudato, transudato modificado e exsudato. Foram utilizados 16 cães portadores de efusão abdominal, atendidos pelosetor de clínica médica de pequenos animais do Hospital Veterinário da Universidade Federal Fluminense (UFF) e demaisclínicas veterinárias de Niterói e Rio de Janeiro (RJ). Foram coletadas amostras de sangue e fluido abdominal e encaminhadaspara análise laboratorial. Após o processamento das amostras, quatro foram classificadas como transudatos, oito comotransudatos modificados e quatro como exsudatos. A atividade da LDH no fluido e sua relação fluido/soro conseguiramdiferenciar os transudatos dos transudatos modificados e exsudatos. Já a atividade sérica de LDH desses cães nãopossibilitou a diferenciação entre os três grupos. Os níveis de FA no fluido e no soro desses cães também não conseguiramestabelecer diferenças entre os três grupos. Em contraste, a relação fluido/soro de FA conseguiu diferenciar os transudatosdos transudatos modificados e exsudatos. Os resultados sugerem que a LDH pode ser mais eficiente como marcadorbioquímico que a FA, auxiliando na classificação das efusões abdominais.
