Venomous snake bite without clinical envenoming ('dry-bite'). A neglected problem in Brazil.

Venomous snake bite without envenoming ('dry-bite') has been recognized throughout the world, but neglected in the Brazilian literature. Forty cases of patients bitten by venomous snakes of the genera Bothrops (lance-headed vipers) and Crotalus (South American rattlesnakes), confirmed by identification of the captured or dead snake, were seen in a 34-month prospective study carried out in a teaching hospital in southeastern Brazil. Out of the 33 cases of lance-headed viper and 7 of rattlesnake bite, respectively 10 (30.3%) and 3 (42.9%) had no clinical or laboratory evidence of local or systemic envenoming. Both within the Bothrops and Crotalus groups, there was no significant difference in sex and age of the patients, and time between bite and medical assistance between the patients who had from those who did not have clinical envenoming. The high prevalence of 'dry-bite' in this study may have several possible explanations, and has implications on the indication of antivenom for the treatment of venomous snake bite. Antivenom administration may be postponed or even not indicated for victims of snake bite presenting no manifestations of local or systemic envenoming.