Bothrops Snakebites in Dogs

Abstract

Background: Snakebites occur frequently among humans and animals. In Brazil, about 23,000 cases of snakebite involving humans were recorded in 2016, 11% of them caused by venomous snakes. In the region of Cuiabá, capital of Mato Grosso, the highest occurrence is of snakes of the genus Bothrops (81%), followed by Crotalus (4%). Bothrops venom has proteolytic, coagulant and hemorrhagic effects, whereas Crotalus venom is neurotoxic, myotoxic and nephrotoxic. This paper reports on three cases of Bothrops snakebites in dogs treated at the Veterinary Hospital of the Federal University of Mato Grosso in 2017.Cases: Three dogs were treated showing clinical signs of snakebite, possibly by Bothrops, since their owners reported that these are the snakes most frequently found where they live. This information is consistent with the known geographic distribution of snakes of the genus Bothrops in the state of Mato Grosso, Brazil. In the first report (Case 11), the patient was bitten on two different occasions in a five-month interval, and died presumably due to anaphylactic shock caused by the venom injected by a second snakebite (Case 12). In both episodes, the animal presented a swollen face and neck, dyspnea and eye bleeding, and these signs were more severe in the second episode. Case 2 was a dog with severe neck and chest swelling and pain. The owner of this dog reported that he had taken his dog for a walk in the countryside, along with the dog of Case 1, and had returned home with both dogs about three hours before the consultation. Case 3 was a Rottweiler living at a small family farm located 67 km from Cuiabá. The animal presented with slight swelling and pain in the left forelimb, and puncture wounds on the lower limb. Neutrophilic leukocytosis was observed in cases 1 and 3.  In addition, Case 12 (the second episode of Case 1) presented with thrombocytopenia and increased prothrombin time and activated partial thromboplastin time. The dog of Case 2 presented no hematological or biochemical alteration. All the dogs received antivenom serum and supportive care.Discussion: Based on the clinical signs of local swelling with bleeding and absence of neurological signs, the snakebites were attributed to the genus Bothrops. In Case 12, blood clotting tests showed non-coagulation. The greater severity of Case 1, which culminated in death, was attributed to anaphylaxis due to prior exposure or the larger amount of venom than that injected in Case 2, since the two injuries were inflicted in the same environment on the same day, probably by the same snake. Neutrophilic leukocytosis may be indicative of an inflammatory reaction, while thrombocytopenia and clotting changes are associated with the hemorrhagic activity of Bothrops venom. Death by snakebite is directly linked to the amount of venom injected, the envenomation site, and the time between the bite and the beginning of treatment. This explains the moderate signs presented by Cases 2 and 3, whose injuries were inflicted on the neck and forelimb, unlike the dog of Case 1, which was bitten on the head on two occasions. It was concluded that Bothrops venom causes systemic and local alterations characterized by pain, swelling, necrosis and bleeding. Early access to antivenom treatment is essential to neutralize clinical signs and prevent worsening of systemic poisoning. The determining factor in snakebite deaths is the amount of injected venom and the time elapsed between the injury and the beginning of treatment.