Toxicity of the venom of Latrodectus (Araneae: Theridiidae) spiders from different regions of Argentina and neutralization by therapeutic antivenoms

•We studied the toxicity of 18 samples of venom from Latrodectus from different regions of Argentina.•The neutralization of some venoms by three therapeutic antivenoms was tested.•Venoms showed differences in toxicity inclusive in spiders of the same species and region.•All the antivenoms neutralized the venoms although the specific ones seem to be the best choice for the treatment.

“Black widow” spiders belong to the genus Latrodectus and are one of the few spiders in the world whose bite can cause severe envenomation in humans and domestic animals. In Argentina, these spiders are distributed throughout the country and are responsible for the highest number of bites by spiders of toxicological sanitary interest. Here, we studied the toxicity and some biochemical and immunochemical characteristics of eighteen venom samples from Latrodectus spiders from eight different provinces of Argentina, and the neutralization of some of these samples by two therapeutic antivenoms used in the country for the treatment of envenomation and by a anti-Latrodectus antivenom prepared against the venom of Latrodectus mactans from Mexico. We observed important toxicity in all the samples studied and a variation in the toxicity of samples, even in those from the same region and province and even in the same Latrodectus species from the same region. The therapeutic antivenoms efficiently neutralized all the venoms studied.