Severity of Scorpion Stings in the Western Brazilian Amazon: A Case-Control Study

Background Scorpion stings are a major public health problem in Brazil, with an increasing number of registered cases every year. Affecting mostly vulnerable populations, the phenomenon is not well described and is considered a neglected disease. In Brazil, the use of anti-venom formulations is provided free of charge. The associate scorpion sting case is subject to compulsory reporting. This paper describes the epidemiology and identifies factors associated with severity of scorpions stings in the state of Amazonas, in the Western Brazilian Amazon. Methodology/Principal Findings This study included all cases of scorpion stings in the state of Amazonas reported to the Brazilian Diseases Surveillance System from January 1, 2007 to December 31, 2014. A case-control study was conducted to identify factors associated with scorpions sting severity. A total of 2,120 cases were reported during this period. The mean incidence rate in the Amazonas was 7.6 per 100,000 inhabitants/year. Scorpion stings showed a large spatial distribution in the state and represent a potential occupational health problem for rural populations. There was a positive correlation between the absolute number of cases and the altimetric river levels in the Central (p<0.001; R-s = 0.479 linear) and Southwest (p = 0.032; linear R-s = 0.261) regions of the state. Cases were mostly classified as mild (68.6%), followed by moderate (26.8%), and severe (4.6%). The overall lethality rate was 0.3%. Lethality rate among children <= 10 years was 1.3%. Age <10 years [OR = 2.58 (95% CI = 1.47-4.55; p = 0.001)], stings occurring in the rural area [OR = 1.97 (95% CI = 1.18-3.29; p = 0.033) and in the South region of the state [OR = 1.85 (95% CI = 1.17-2.93; p = 0.008)] were independently associated with the risk of developing severity. Conclusions/Significance Scorpion stings show an extensive distribution in the Western Brazilian Amazon threatening especially rural populations, children <= 10 in particular. Thus, the mapping of scorpions fauna in different Amazon localities is essential and must be accompanied by the characterization of the main biological activities of the venoms. Urban and farming planning, in parallel with awareness of workers at risk for scorpion stings on the need for personal protective equipment use should be considered as public policies for preventing scorpionism.