Spitting cobras: Experimental assay employing the model of chicken embryo and the chick chorioallantoic membrane for imaging and evaluation of effects of venom from African and Asian species (Naja ashei, Naja nigricollis, Naja siamensis, Naja sumatrana).

Among the captivating world of venomous snakes, an outstanding group of cobras from the family Elapidae is characterized by a distinctive structure of proteroglyphous venom apparatus that allows the ejection of venom from the fangs and formation of aerosol particles. The venom of "spitting" cobras is innocuous when sprayed over the intact skin, but contact with the eye surface is followed by ophthalmia and a temporary blindness, that may remain permanent, unless immediate and adequate medical interventions are carried out. The aim of this work was to monitor and evaluate induced vasoactive effects as well as embryotoxic effects with the regard to the whole crude venom of four "spitting" cobra species (African species Naja ashei and Naja nigricollis, Asian species Naja siamensis and Naja sumatrana). Vasoactive effects were visualized using the Hen's Egg Test - Chorioallantoic membrane (HET-CAM) test. The Chick Embryotoxicity Screening Test (CHEST) was used to estimate embryotoxicity and the data were then processed using statistical analysis. The highest embryonic mortality rate was observed after administration of venom from Naja nigricollis among the whole crude venoms tested. All tested venoms induced fast spreading of pathological alterations in the blood vessels on the chorioallantoic membrane. Our study discloses a detailed insight into microscopic level processes in venom-induced changes observed on the chicken embryos and on the vascular network in their chorioallantoic membrane. This article also highlights the increasing importance of the role of the chicken embryos and the importance of observing changes in the chorioallantoic membrane applied for toxicological and medical research as an appropriate alternative animal model in relation to 3R's principles.