The toxicity of snake venoms is mostly determined in mice, the most frequently used mammalian model. These assays are expensive and subject to strict ethical regulations. To overcome these drawbacks, we evaluated the potential use of alternative models for snake venom testing. Caenorhabditis elegans is a free-living nematode widely used in biomedical research.

The wild-type N2 strain was used in all experiments. Ten L4-stage worms were pipetted into each well of a 96-well microplate containing M9 buffer. Worms were then exposed to six different concentrations of snake venom (0, 200, 400, 600, 800, and 1000 µg/ml) in a M9 buffer. The venom used was from Naja kaouthia (monocled cobra). Plates were incubated at 20 °C for 24 hours, after which motility and viability were assessed. Worms exhibiting movement were considered alive, while those that became straight and rigid were considered dead. Motility was quantified using the Wmicrotracker device (Phylumtech).

The results show lethality of N. kaouthia venom in a dose-dependent manner, and the LD50 was estimated to be 520 μg/mL. Increased mortality was preceded by a decrease in motility, and this could be attributed to the neurotoxic activity of the venom.

High doses of N. kaouthia exhibited significant effects on the viability and motility of the free-living nematode C. elegans, suggesting a potential utility for studies on snake venom toxicity and their neutralization. Nevertheless, the mass of venom required for the LD50 determination of L4 mortality was high. Despite this drawback, considering the cost and difficulty of venom obtaining, a study on other early larval stages must be tested in order to determine if the doses of venom required could be lower. Nevertheless, the usefulness of testing toxic mechanisms in wild-type, transgenic, or mutant strains makes C. elegans a suitable model for snake venom toxicity testing.