Older Age and Time to Medical Assistance Are Associated with Severity and Mortality of Snakebites in the Brazilian Amazon: A Case-Control Study

Abstract

The Amazon region reports the highest incidence of snakebite envenomings in Brazil. We aimed to describe the epidemiology of snakebites in the state of Amazonas and to investigate factors associated with disease severity and lethality. We used a nested case-control study, in order to identify factors associated with snakebite severity and mortality using official Brazilian reporting systems, from 2007 to 2012. Patients evolving to severity or death were considered cases and those with non-severe bites were included in the control group. During the study period, 9,191 snakebites were recorded, resulting in an incidence rate of 52.8 cases per 100,000 person/years. Snakebites mostly occurred in males (79.0%) and in rural areas (70.2%). The most affected age group was between 16 and 45 years old (54.6%). Fifty five percent of the snakebites were related to work activities. Age ≤15 years [OR=1.26 (95% CI=1.03-1.52); (p=0.018)], age ≥65 years [OR=1.53 (95% CI=1.09-2.13); (p=0.012)], work related bites [OR=1.39 (95% CI=1.17-1.63); (p<0.001)] and time to medical assistance >6 hours [OR=1.73 (95% CI=1.45-2.07); (p<0.001)] were independently associated with the risk of severity. Age ≥65 years [OR=3.19 (95% CI=1.40-7.25); (p=0.006)] and time to medical assistance >6 hours [OR=2.01 (95% CI=1.15-3.50); (p=0.013)] were independently associated with the risk of death. Snakebites represent an occupational health problem for rural populations in the Brazilian Amazon with a wide distribution. These results highlight the need for public health strategies aiming to reduce occupational injuries. Most cases of severe disease occurred in the extremes of age, in those with delays in medical attention and those caused by Micrurus bites. These features of victims of snakebite demand adequate management according to well-defined protocols, including prompt referral to tertiary centres when necessary, as well as an effective response from surveillance systems and policy makers for these vulnerable groups.

Stepping into a dangerous quagmire: environmental determinants of human-lancehead pit vipers (Bothrops genus) contact resulting in injuries, Brazilian Amazon

“…In the Brazilian Amazon, although urban population predominates, most of the snakebites were recorded in adult males living in rural areas. This epidemiological profile was reported previously in the Amazon (35,36), and probably is related to a significant higher exposition of this population group when exerting agricultural or forestry activities, in the habitat mostly selected by lancehead pit vipers. Several studies have reported on habitat use by B. atrox, the easiest snake to find in comparison to other species in Central Amazonia (46), and concluded that the species is mainly found on the ground or climb into understory vegetation, in the case of juveniles (15)(16)(17).…”

“…In the Brazilian Amazon, snakebites are under the influence of precipitation, likely because snakes in the Amazon exhibit increased activity during months with heaviest rainfall. Moreover, in this period, the snakes look for upland areas during flooding, which increases the likelihood of contact between humans and snakes (35,36). The contact between snakes and human populations is often associated with extractive or agricultural activities, which can increase snakebite burden in…”

Fatal Snakebite Envenoming and Agricultural Work in Brazil: A Case–Control Study

“…Furthermore, older age favors the occurrence of comorbidities, such as diabetes and cardiovascular diseases, that potentialize the risk of renal failure, the main cause of death in snakebite envenomings in Brazil. 18,27 In the study population of Brazilians aged 10 years and older, with complete sets of data, for the period 2004 to 2015, lethality was 1.0%. In the state of Amazonas, Brazil, among people from all age groups, with complete sets of data, for 2007 to 2012, lethality was 0.6%.…”

“…Time to treatment ³ 6 hours has been reported as an important predictor of lethality by snakebite envenoming. 18,19 Late time to treatment is a bad prognostic factor because AV can only neutralize the circulating venom but cannot hamper the local lesions that are useful in staging the clinical picture. Because of this, the snakebite AV must be administered before the physiopathological effects associated with the venom appear.…”

High mortality due to snakebites in French Guiana: Time has come to re-evaluate medical management protocols

“…However, it is difficult to have a precise estimation of the relative proportion of species incriminated in snakebites, as snake identification is possible in less than 5% of the cases; in most cases, patients consult at the emergency ward without the specimen [3]. In recent publications in Manaus, Amazonas, Brazil, genus identification based on clinical and epidemiological criteria was reported in 91% of cases [4]. …”