Crotalus cascavella,

- THOMPSON M,
Natural history
Crotalus durissus
Homoeopathic name and abbreviation: Crotalus cascavella; Crot-c.
Common names: Tropical rattlesnake or Mexican cascavel.
Description: It occurs in dry plateaus and is common on ranches and farms where it is greatly feared. It reaches lengths of up to 1.8 m.
Distribution: Mexico
Range: Dry regions of a number of states in Brazil.
Venom: This is a highly dangerous snake with an extremely toxic venom that has a strong neurotoxic component. 75% of all untreated adults die from a cascavel bite.
Authority: Wagler, 1824.
Comments: The name cascavella probably comes form the Spanish cascabel meaning little bell. The cascavel is greatly feared because it venom contains a substantial amount of neurotoxic material. The Sx of a cascavel bite are different from that of North American rattlesnakes whose venom destroys the walls of blood tissues and other tissues. Among South American Indians it is claimed that anyone bitten by a cascavel will suffer a broken neck! One of the most frightening symptoms is a paralysis of the neck muscles which causes the head to drop to one side. Severe neural disturbances appear later inducing auditory and visual disturbances that lead to blindness, unconsciousness and death from asphyxiation. The symptoms at the point where the snake bit the person are not as pronounced as in other rattlesnakes.
There are a number of other subspecies of Crotalus durissus; namely durissus, totonacus, tzabacan.
(T F Allen)
HABITAT This species is usually found in semi-arid regions, including dry to very dry tropical forest and thorn woodland, but also in relatively dry open areas within mesic forests. Other habitats occupied in various parts of the range include tropical deciduous forest; pine-oak forest; arid tropical scrub; grass (Trachipogon), pine, or palm savannahs (including those bordered by rainforest); and, rarely, natural breaks in cloud forest. Crotalus durissus is encountered infrequently in dense forest, and it is largely absent from rainforest, as reflected by its distribution.
Mure: This terrible serpent is found in the province of Ceara, whence it was brought Rio Janeiro. This species generally attains a length of from four to five feet but the animal from which the poison was taken for our provings, was three feet long. Its oval-triangular head one half of which is provided with shields, shows a round depression in front of the eyes, which are covered with a large elliptical shield, serving as a lid. The body is big, conical, its movements are sluggish; its upper surface is covered with scales, the dorsal scales being keeled and somewhat lanceolate, the scales of the tail being quadrangular and smaller. The belly is provided with one hundred and seventy large transversal plates; there are twenty five plates belonging to the tail, the three first of which are divided in shields. The extremity of the tail is furnished with seven or eight capsules of the consistance of parchment which, when agitated, produce a shrill sound. The color of the Crotalus cascavella is a yellowish-brown, much lighter under the belly, with twenty four or twenty six regular long rhomboidal lines on each side of the back. When irritated and during the excessive heat, the Crotalus cascavella spreads a very fetid musk-like odor. The molar teeth which are few in number, but long and excessively poisonous, are inserted in exceedingly dilatable jaws. Every body knows that the poison of this reptile acts with a frightful intensity; and it was not without great danger that Drs Mure and Martins succeeded in obtaining a few drops of it, by compressing from the living animal the gland which secretes it.
DESCRIPTION Crotalus durissus is a stout terrestrial rattlesnake commonly reaching about 1 metre in length. Large males in some populations may attain lengths of 1.4-1.6 metre, and the maximum is at least 1.8 metre.
The defensive coil in C. durissus is spectacular, with the head and anterior third of the body lifted high off the ground, the neck bent like a shepherd's crook, and the snake facing its antagonist. This species is an important cause of snakebite mortality throughout most of its range. Reports of human envenomation by C. durissus can be divided into two distinct clinical pictures represented by C. d. durissus in southern Mexico and Central America and C. d terrificus in South America.
In 21 cases of C. d. durissus envenomation, 10 victims developed swelling of the entire extremity, 3 had hypo-fibrinogenuria, and 3 had local necrosis. All had a satisfactory recovery and there was no case of neurotoxicity or renal failure. This clinical picture was similar to mild to moderate envenomation by Bothrops and Crotalus species of North America. The concept that C. d. durissus envenomation was similar to that by C. d. terrificus in producing neuromuscular paralysis apparently originated with March's (1928b) case report of neck muscle ''paralysis" following C. d durissus envenomation; however, no similar cases have been reported since, and other reports substantiate that envenomation by individuals of the Middle America populations of C. durissus does not produce this effect.
A detailed description of clinical venom effects by C. d. terrifficus in Brazil emphasised the findings of progressive neuromuscular paralysis, and hemolysis of red cells with resultant renal failure. A mortality incidence of 72% without treatment was reduced to 12% with treatment. In the most recent large series reported (1966-1973), fatality was further reduced to 6%. In addition to respiratory paralysis and renal failure, recent investigators have reported hypotension (shock), afibinogenemia, and myoglobinuria with acute renal failure. Uniformly, reports indicate a lack of swelling or other significant local effects of the venom. There is no documented report that envenomation by any other species of pitviper produces clinically significant paralysis, although the venoms of several Crotalus species contain "neurotoxins".