It has been well documented that snakes are a dietary component of various raptor species. Interestingly, research has documented that Red-tailed Hawks are especially known to prey on snakes. When all goes correctly, the raptor tends to grab the snake by the head for control. Unfortunately, however, bites can occur and there can be devastating consequences from the bite of a venomous snake.
Venomous snakes occur worldwide and are considered a threat to public health and safety. Over 3000 species of snakes have been identified, with at least 600 considered venomous.
The World Health Organization (WHO) has defined two categories of venomous snakes. Category 1 snakes hold the highest medical importance. These are highly venomous snakes with the ability to cause high levels of morbidity, disability or mortality. Category 2 snakes are considered of secondary medical importance. These venomous snakes also have the ability to cause morbidity, disability and death, but are less frequently implicated. This may be due to their activity cycles, behavior, habitat preference, or occurrence in areas considered remote to human populations. The WHO recommends that venomous snakes from category 1 should be considered as highest priority for antivenom production. A complete list of the venomous snakes listed in each category can be found on the WHO website. www.who.int
Types of venom: There are three types of venom from venomous snakes. It is possible for certain species to produce more than one type of venom.
Neurotoxins will cause paralysis of the respiratory system (examples are mamba, coral and cobra snakes). Some of these will be deadly to humans and animals.
Hemotoxins will affect the heart and cardiovascular system. Most vipers are in this category. A neurotoxin may also be present in some vipers, like the Mojave rattlesnake.
Cytotoxins will cause localized effects at the bite area. An example is the spitting cobras that have more cytotoxic versus neurotoxin effects. However, the localized effects can spread systemically if not treated.
Clinical signs The wide variability of the venomous components between snakes, even between the same species, will lead to a variety of pathological changes in the tissue and systemically. Localized tissue destruction at the site of the bite can lead to secondary bacterial infections, tetanus, or gas gangrene situations. As the toxin spreads, bleeding disorders leading to a fatal hemorrhage or kidney failure is possible. Cardiac arrhythmias will lead to myocardial weakness and failure. Neurotoxins will cause flaccid paralysis and respiratory failure.
The following are examples of venomous snakes and what they can do. The Cerastes cerastes is also known as the Saharan Horned Viper, native to the deserts of Northern Africa and parts of the Middle East. Although this snake is considered Category 2, the venom has more than 13 different toxins depending on the geographical location of the snake’s range. Cerastes cerastes has hemotoxin venom. The bite can cause cytotoxic (localized) and hemorrhagic effects which are often not fatal. However, if the bite is severe enough it can cause life threatening coagulopathies, thrombocytopenia, hemolytic anemia, and acute renal failure.
The Western Diamondback, Crotalus atrox, and the Mojave Rattlesnake Crotalus scutulatus, are found in the southwestern United States and central Mexico. These snakes are considered Category 1 snakes. The Western Diamondback can release a large volume of venom with one bite. This venom is hemotoxic and attacks the blood system. The Mojave Rattlesnake is one of the world’s most venomous snakes and has a neurotoxin and hemotoxin that are extremely lethal.
Antivenom Birds are not immune to the toxic affects of venomous snakebites. In humans, the preferred treatment for any venomous snake bite is the use of snake antivenom immunoglobulins (antivenoms). Antivenoms have the ability to prevent or reverse the snakebite envenoming effects. They play a crucial role in minimizing mortality and morbidity.
The same can be held true in our animal world. It is important to realize that antivenoms are produced from specific species of snakes from specific regions. There is not a universal antivenom. If antivenom is produced from a specific species, the antivenom may not be effective against the effects of bites from venomous snakes in a geographical location where that snake is not found.
There is limited research and papers documenting how much antivenom to give a bird. Doses are often extrapolated from human medicine. In one documented case, a dose of 1.5 ampules (15 mls) of antivenom in a 1:2 dilution of sterile saline was administered slowly intravenously to a domestic duck. In addition to aggressive medical supportive care, this treatment was successful for this patient.
Treatment: Time is of utmost importance. Seeking medical help within the first thirty minutes is preferable. As the toxins spread, irrevocable damage can be done.
If the bird is bitten on the leg or foot, remove the cuff immediately.
Cleanse the area with water and chlorhexidine, if you have this in your first aid kit. Diluted betadine would also be acceptable and of course water if that is all you have.
Keep the bird calm and still as you head to the nearest veterinary emergency clinic. Most veterinary emergency clinics carry antivenom for their area.
Call ahead and let them know you are on your way and ask if they have the antivenom. They may direct you to another facility if they do not have the products.
Do not use venom extractors, for they may do more harm and for your own safety, do not try to suck out the venom.
Often, a bird will need to be hospitalized for aggressive therapy. Antivenom, fluids, antibiotics, anti-inflammatory medications, pain control, and support for renal and cardiac events are all part of the treatment. The bird may need to be hospitalized for several days, depending on the severity of the bite and the reaction. Diagnostic blood testing to monitor organ functions will also be part of the therapy plan. The prognosis is often guarded until the bird can be stabilized and the response to treatment evaluated.