Have you ever wondered about poisoning concerns for wildlife and exotics? In this post, we’ll dive into several toxins for five different wildlife species, waterfowl, reptiles, aquarium fish, raptors and fireflies.
- Heavy Metals
- Lead toxicosis has been reported in waterfowl after being exposed to lead shot.
- Zoologic waterfowl developed zinc toxicosis after ingestion of pennies and fence clips found in their exhibits (US pennies minted after 1983 have approximately 98% zinc) and free-flying waterfowl have also been exposed to toxic levels of zinc in areas contaminated by mining and smelting wastes.
- Sources of methyl mercury encountered by waterfowl include grains treated with organomercurial fungicides or by means of bioaccumulation of mercury through industrial contamination of aquatic food chains.
- Sources of copper include formulated diets, mining and industrial wastes, pesticides, fungicides, antifouling marine paints, and wood preservatives.
- Environmental sources of selenium include smelter emissions, sewage sludge, and soils with naturally or artificially elevated levels.
- Pesticides (specifically organochlorines, organophosphates, carbamates)
- Toxicosis has been reported in waterfowl ingesting treated grains or germinating seedlings from golf courses, agricultural fields and other large treated areas.
- Botulism is caused by ingestion of neuroparalytic toxin (usually type C in waterfowl) produced by the gram-positive anaerobic bacillus Clostridium botulinu. Waterfowl ingestion of toxin-laden invertebrates or maggots starts the botulism outbreak. The cycle accelerates as more birds die as a result of botulism, more maggots are produced, and more birds ingest the toxic maggots.
- Mycotoxicosis results from ingestion of toxins produced in fungal contaminated (moldy) food.
- Algal blooms (‘‘red tides’’) have been associated with acute waterfowl mortality. Toxins produced by another blue-green cyanobacterium, Anabaena flos-aquae, have also been documented to cause waterfowl mortality.
- Petroleum Oils
- The most common sources of petroleum exposure include oil spills; however, oil pits (waste storage pits and tanks at oil production facilities) have also been associated with avian mortality.
- Vitamin A
- Reptiles can suffer from not getting enough Vitamin A and from getting too much Vitamin A (turtles and tortoises are particularly sensitive to Vitamin A deficiencies. Reptiles suffering from a lack of Vitamin A typically show ocular discharge, palpebral edema and blindness, hyperkeratosis of skin and mouthparts, and aural abscesses. Reptiles exposed to excessive amounts of Vitamin A can develop inappetence, full-thickness skin sloughing, secondary bacterial infection, discoloration of the skin, and extreme lethargy.
- Vitamin D
- Well-meaning owners, breeders, and veterinarians often over-supplement captive reptiles. Chronic overdosing of Vitamin D can cause calcification of the gastrointestinal tissue, the kidneys, lungs, heart, blood vessels, and joints.
- Pyrethrins and pyrethroids have the same mechanism of action. The difference is that pyrethrins are derived from chrysanthemums and pyrethroids are synthetically made. A variety of pyrethrins and pyrethroids have been recommended for use against reptile parasites. If used appropriately, these agents are safe and effective, a brief exposure to the skin is all that is needed to kill the parasites (the reptile should be rinsed off immediately after the product is used). It is when reptiles are saturated with the sprays, or the sprays are left on, that we can see toxicosis develop.
- This antiparasitic drug have been used in reptiles with minimal toxicity at appropriate doses. Overdoses have been reported to cause death in smaller snake species.
- Soaking living animals in any solution can be potentially life threatening. There have been reports of turtles developing toxicosis after a chlorhexidine bath. Additionally, attention should be paid to the depth of the fluids the reptile is being soaked in and they should never be left unattended in a bath.
- Bleaches can be very effective in treating cage parasites of reptiles but should never be applied directly to the animals. Bleach can cause ocular burns if splashed in the eyes and skin exposed to bleach should be washed with a mild soap and lukewarm water as prolonged contact can cause significant dermal irritation or injury. Animals should be kept out of recently bleached cages for a minimum of 24 hours to prevent respiratory tract irritation. Cages should be allowed to air out, and residual disinfectant should be removed by wiping with a clean cloth or towel.
- Water Quality
- Poor water quality kills more fish than infectious agents and most cases of toxicity are due to deficiencies in husbandry and tank maintenance. Common water quality–related toxicities in aquarium fish include pH, ammonia, nitrite, nitrate, chlorine/chloramines and hydrogen sulfide. Optimal water pH varies between species. A pH outside of the optimal range may not immediately result in acute death; however, chronic exposure may lead to stress and subsequent immunosuppression, predisposing the fish to disease. Rapid fluctuations in pH are generally more problematic for fish than specific individual pH values.
- Ammonia toxicity is one of the most common water quality problems affecting aquarium fish and can cause acute death or chronic stress. Ammonia is more toxic in warmer water, at higher pH, and at lower salinity. Ammonia is a primary waste product of fish and can also originates from the decay of complex nitrogenous/protein compounds in the tank. Non-ionized ammonia is the most toxic form of ammonia. It is excreted from the gills by diffusion. Environmental increases in non-ionized ammonia decrease the rate of diffusion from the gills, resulting in elevated blood and tissue ammonia levels.
- Nitrate toxicity is also known as “brown blood disease” or “methemoglobinemia.” Ammonia is oxidized to nitrite and excess amounts of nitrates in the tank are caused by similar issues as those that cause ammonia elevations. Nitrite is absorbed by the gills and oxidizes hemoglobin to methemoglobin, resulting in methemoglobinemia and hypoxia. The gills may appear pale or tan in color. In severe cases, gills and blood may show brown discoloration due to the methemoglobin.
- Chlorine and Chloramine
- Chlorine is added to municipal water to kill microorganisms and is highly toxic to fish. Chloramines are also sometimes used as disinfectants in municipal water supplies and are also toxic to fish. Chlorine causes gill necrosis resulting in hypoxia (lack of oxygen). Chlorine and chloramine can also result in hemolytic anemia and chloramine may result in methemoglobin formation. The most common cause of chlorine/chloramine toxicity in aquarium fish occurs when water is added to the tank without prior dechlorination. Fish affected by chlorine toxicity typically exhibit respiratory signs and acute death. Chronic exposure to lower levels of chlorine may result in a history of sporadic mortalities. There are test kits available to check a tank’s chlorine and chloramine levels.
- Hydrogen Sulfide
- Hydrogen sulfide can occur at the bottom of aquariums that have excessive organic debris or in deep gravel/sand filter beds that are not completely aerated and is more common in marine systems. Disturbing the filter media or bottom substrate, which can occur when an owner thoroughly cleans the gravel bed after a long period of neglecting routine maintenance, can release hydrogen sulfide into the water column. Presence of hydrogen sulfide can be detected by its characteristic rotten egg odor and can be confirmed with commercial test kits. Additionally, the owner may report a ‘‘black cloud’’ released into the water during cleaning processes. Hydrogen sulfide interferes with respiratory functions resulting in hypoxia.
- Exposure to pesticides is less common in aquarium fish vs. wild fish but is still a concern. Most household pesticides are highly toxic to fish. Indoor pest control is often performed using aerosolized sprays so it is important for the homeowner to turn off air pumps and cover the tank until the danger of pesticide introduction has passed. More rare is the household pet who has let curiosity get the better of them and has fallen into an indoor tank or an outdoor pond. If this pet has recently had a topical pesticide preventative applied, or are wearing a preventative collar, then the fish are at risk for toxicosis.
- Anticoagulant Rodenticides
- Anticoagulant rodenticides are rodent poisons (baits) that cause internal bleeding. Raptors are birds of prey and although they do not typically directly ingest these baits, they do eat the rodents that ingest the bait. Because of this, raptors are very susceptible to secondary poisoning and chronic toxicosis due to the accumulation of the bait in their system.
- Birds have very efficient respiratory systems and are therefore highly sensitive to airborne particles including aerosolized air fresheners, other products that come in sprays and sometimes even candles.
- Teflon is a nonstick coating used on many products including cookware, drip pans, and heat bulbs. Raptors dying from teflon toxicosis have often been exposed to teflon-coated heat lamps. As the bulbs heat up, toxic fumes can be released. The toxic fumes released by overheated teflon cause severe edematous pneumonia (blood capillaries in the lungs hemorrhage and the lungs fill with fluid and blood) leading to acute respiratory distress and most commonly death.
- Carbon Monoxide (CO)
- Like people, birds can be exposed to hazardous levels of CO if housed in an area with a faulty working furnace, or if confined in an operating vehicle with poor ventilation and/or leaks in its exhaust system. CO does not derive the body of oxygen by directly affecting the lungs; it acts by decreasing the oxygen carrying capacity of hemoglobin (found in our red blood cells). In pet birds, clinical signs may include dyspnea, ataxia, depression, and nausea. CO poisoning in raptors is most often fatal, as the exposure is not immediately realized.
- Bleach when used for disinfecting travel crates and housing structures, naphthalene (often used to store spare feathers for imping – feather replacement – purposes), tobacco smoke, and some disinfectant sprays can cause varying degrees of respiratory illness depending on the circumstances of the exposure.
Reptiles and Fireflies
- Many reptile owners or caretakers will supplement the diet of captive reptiles with freshly caught insects. Fireflies of the genus Photinus are known to contain steroidal pyrones (lucibufagins) which are structurally similar to the cardenolides of plants and bufodienolides of toads, both of which can cause nausea and vomiting at low concentrations and can be potentially cardiotoxic at higher doses.
- Lucibufagins protect fireflies from predators and spiders, birds, and several species of lizard have been known to avoid fireflies. However most lizards, including bearded dragons, show indiscriminate eating strategies and may ingest toxic substances.
- In addition to fireflies, other insects that sequester cardenolides, such as monarch butterflies (donaus plexippus), queen butterflies (Donaus gilippus), and lygaeid bug (Oncopeltus fasciatus) should also not be fed to reptiles.