London, 31 Aug (AIM) – A study published in the academic journal “PLOS Neglected Tropical Diseases” has found that snakebites in Mopeia district, in the central Mozambican province of Zambezia, result in about three thousand lost days of work and schooling a year with an economic cost to the victims on average of 17 US dollars.
The researchers calculate that this makes it “almost 5-fold the cost of uncomplicated malaria cases”.
The research was carried out by the Manhiça Health Research Centre (CISM) as part of a project funded by the Barcelona Institute for Global Health (ISGlobal). It found that in Mopeia there are 393 snakebites per 100,000 inhabitants per year, impacting two per cent of households.
It found that although most snakebites were on people between the ages of 20 and 25, when taking into account the population profile, the rate of bites per 1,000 is much higher in adults older than 64 (who also have a lower recovery rate).
According to the authors of the report, “snakebite is a neglected disease with a dearth of data and research funding”. They highlight that it was possible to carry out the study by piggy-backing onto a demographic survey conducted in preparation for a malaria cluster-randomised trial, which “enabled us to reveal the burden and identify risk factors of snakebite with minimal disruption or expense to the parent trial team or participants”.
The paper notes that snakebite is a devastating condition that can take away lives and livelihoods, with an estimated 80,000 to 138,000 deaths globally each year.
It suggests that this is a gross underestimate because snakebites take place most frequently in rural settings. In addition, the economic impact of snakebite disproportionally affects the rural poor, and its “associated productivity costs perpetuate the poverty traps in these communities”.
A total of 70,947 people and 13,140 households were included in the study. A total of 272 individuals from 254 different households reported that they were bitten by a snake over the previous 12 months. Of these, five were bitten twice and one was bitten three times bringing the total number of bites to 279. Of those bitten, 77 per cent were envenomated (the others received what is known as a “dry bite” and did not receive venom from the snake). Of all those bitten, over 17 per cent reported not making a full recovery at the time of the survey with four people reporting that they had lost a limb.
The authors note that a surprising result from this study is the lack of reported mortality. They postulate that this is explained by the main source of snakebites in Mopeia: Bitis arietans (puff adder) and Naja mossambica (Mozambique spitting cobra).
They hypothesise that the higher morbidity seen in those bitten at home is compatible with the presence of Mozambique spitting cobras which are described as “an aggressive species known to enter houses and whose bites often result in severe injury but not usually rapid death”. In addition, it is thought that some bites could come from Proatheris superciliaris (Obscure viper or lowland swamp viper) or Atractaspis bibronii (southern stiletto snake).
The advantage of low-cost surveys like this is that they can reveal correlations that could provide clues to the causes of snakebites. For example, this survey found an increased risk of snakebite amongst owners of cats, dogs, and goats which could be the result of animal food and waste attracting rodents which are common prey for snakes. Meanwhile, ownership of pigs, cattle, and poultry was not found to be associated with an increased risk of snakebite – perhaps because they are less likely to roam around the home.
The Manhiça Health Research Centre was set up in 1996 with the purpose of conducting biomedical research in priority areas and is supported by the Government of Mozambique and the Spanish Agency for International Development Cooperation (AECID).