QCOSTARICA – Snakebites are environmental and occupational health hazards that mainly affect rural populations worldwide. In Costa Rica, climatic changes are related to the increase in snake bites, is the conclusion by Costa Rican researchers Luis Fernando Chaves, Mahmood Sasa, Jose Maria Gutierrez and Taiwanese Chuang Ting-Wu, published in the Science Advances journal.

The researchers asked whether snakebites reported in Costa Rica from 2005 to 2013 were associated with meteorological fluctuations.

The study, conducted over the nine-year period, recorded 6,424 snakebites in the country. The average incidence of bites in these nine years was 15.24 per 100,000, ranging from 10.63 per 100,000 to 22.98 per 100,000 when the entire population was assumed to be at risk.

Fig. 1 Snakes and snakebites in CR. (A) The terciopelo B. asper. (B) Average annual snakebite incidence, by canton, from 2005 to 2013. County color indicates snakebite incidence rate, county boundary color indicates relative risk, and a marking described in the map legend indicates the primary cluster.
Snakes and snakebites in Costa Rica. (A) The terciopelo B. asper. (B) Average annual snakebite incidence, by canton, from 2005 to 2013. County color indicates snakebite incidence rate, county boundary color indicates relative risk, and a marking described in the map legend indicates the primary cluster.

Nevertheless, those figures underestimate the incidence rate in the at-risk population (mainly rural), with the average rate jumping to 41.27 per 100,000, ranging from 30.53 per 100,000 to 58.94 per 100,000 with a steadily decreasing at-risk population

“The research found that there are variations in the incidence of snake bites, depending on different factors, clearly a correlation between the number of bites and certain regions of the country, particularly the South Pacific,“said José María Gutiérrez, of the Instituto Clodomiro Picado.

The researchers also asked how spatial heterogeneity in snakebites and poverty are associated, given the importance of the latter for neglected tropical diseases (NTDs).

Gutiérrez added that the research indicated a correlation between snakebites and poverty. “We found that periodicity in snakebites reflects snake reproductive phenology and is associated with the El Niño Southern Oscillation (ENSO),” said Gutiérrez.

The ectothermic nature of snakes raises the issue of how climate change’s impact on snake ecology could influence the incidence of snakebites in humans in ways that echo the increased predation pressure of snakes on their prey.

Variables spatially associated with snakebites in CR. (A) Altitude. (B) Rainfall. (C) Poverty gap index. (D) Destitute housing. Coefficients are shown (in the legend of each panel) only when pseudo t values are significant (P < 0.05).
Variables spatially associated with snakebites in Costa Rica. (A) Altitude. (B) Rainfall. (C) Poverty gap index. (D) Destitute housing. Coefficients are shown (in the legend of each panel) only when pseudo t values are significant (P < 0.05).

The study reveals that snakebites are more likely to occur at high temperatures and may be significantly reduced after the rainy season. Nevertheless, snakebites cluster in Costa Rican areas with the heaviest rainfall, increase with poverty indicators, and decrease with altitude.

The investigation found that the highest incidence occurred in the south and in the community of La Cruz Guanacaste, near the border with Nicaragua. The scientists used a database of Costa Rica’s Ministry of Health and compared with climatic fluctuations.

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