INCIDENCE AND MORTALITY AFTER SNAKEBITE IN THE AMERICAS

Snakebite envenoming is a relevant public health problem in the Americas, especially in Latin America. On the basis of the estimated number of cases presented in the following table, the total number of cases in the Americas would be about 80,000. However, this is likely to represent a conservative estimate since it is based on official and hospital records which, in many countries, are incomplete. According to the estimation performed by Kasturiratne et al. (2008) in their PLoS Medicine paper, the total number of cases in Latin America ranges between 80,329 and 129,084. In terms of mortality, the available data are clearly incomplete. Kasturiratne et al. (2008) estimated a total number of annual deaths due to snakebite envenomings in Latin America to be between 540 and 2,298, although it is very likely that this is an underestimation as well.

The snake species responsible for the highest toll are the rattlesnakes (Crotalus ssp) in North America and a number of species of lanceheads (Bothrops spp.) in Central and South America, particularly B. asper in Central America and B. atrox and B. jararaca in South America, where a lower number of cases are caused by the rattlesnake Crotalus durissus.

The following tables presents an estimation of the number of cases and incidence* per country, and mortality* for some countries.

* Rates for incidence and mortality are per 100,000 persons per year.

NORTH AMERICA

• Medically important species: Copperheads (USA: Agkistrodon contortrix Mexico: Agkistrodon bilineatus, Agkistrodon taylori), water mocassins (Agkistrodon piscivorus), lanceheads (Mexico: Bothrops asper) rattlesnakes (USA: Crotalus adamanteus, Crotalus horridus, Crotalus oreganus, Crotalus viridis Mexico: Crotalus simus, Crotalus totonacus Both: Crotalus atrox, Crotalus scutulatus)

These US numbers represent all snakebite cases. Of the 9,800 cases reported roughly 3,600 involve venomous bites that cause illness. Modern medical case and good quality antivenoms contribute to the very low mortality rates.

CENTRAL AMERICA

• Medically important species: lanceheads (all except El Salvador: Bothrops asper) rattlesnakes (Costa Rica, El Salvador, Guatemala, Nicaragua: Crotalus simus)

CARIBBEAN

Country	Annual Snakebites	Incidence *	Mortality *
Aruba	NA	NA	NA
Martinique	20 cases	5.0	NA
Saint Lucia	12 cases	7.0	NA
Trinidad and Tobago	NA	NA	NA

• Medically important species: lanceheads (Martinique: Bothrops lanceolatus Saint Lucia: Bothrops caribbaeus Trinidad and Tobago: Bothrops atrox) rattlesnakes (Aruba: Crotalus durissus)

SOUTH AMERICA

Medically Important Snakes: bushmasters (Ecuador, Peru: Lachesis muta) lanceheads (all except Argentina: Bothrops atrox Argentina, Bothrops alternatus, Bothrops diporus Bolivia: Bothrops mattogrossensis Brasil: Bothrops jararaca, Bothrops jararacussu, Bothrops leucurus, Bothrops moojeni Colombia, Ecuador: Bothrops asper, Bothrops bilineatus Guyana, French Guyana, Surinam: Bothrops bilineatus, Bothrops brazili Paraguay, Uruguay: Bothrops alternatus Perú: Bothrops bilineatus, Bothrops pictus Venezuela: Bothrops colombiensis, Bothrops venezuelensis) rattlesnakes (all except Ecuador: Crotalus durissus)

NB: The most important species are those classified within category 1 in the WHO Guidelines for the Production, Control and Regulation of Snake Antivenom Immunoglobulins (WHO, 2010). In the case of Venezuela, the species Bothrops colombiensisis added.

Throughout their respectives ranges in Central and South Amercia, the lanceheads (particularly Bothrops asper and Bothrops atrox), and the Central American rattlesnake (Crotalus simus) exact a terrible toll of suffering due to the necrotic and other tissue destroying actions of their venoms. Amputations and permanent disabilities after bites by these snakes are common. It is not uncommon to come across children in rural communities who have had arms or legs amputated as a result of bites by these snakes. Medical and scientific understanding of the damage that the toxins cause is still far from finding a way to arrest the destruction, and scientists are still trying to learn how to design better antivenoms and other treatments than can help save limbs.

• READ MORE: Envenoming in Latin America and the Caribbean (Article in Spanish)