Disease: Poisoning
Poisoning of wildlife species may be suspected when large numbers of animals die over a short period of time, in a particular area. The investigation of a suspected poisoning can be complex due to the large number of possible poisonous substances. Furthermore, poisoning may be natural (e.g. algal blooms) or related to human activities which can be categorized as accidental or intentional in which case the investigation becomes a criminal matter.
Some of the most common natural poisons are the toxins produced by blue-green algae (cyanobacteria). Phycotoxicosis has caused mass die-offs in aquatic bird populations throughout Europe; these tend to occur during the summer months when nutrient-rich waters are warmed-up permitting rapid growth of the algal population (blooms). Whilst associated with sporadic death and disease (phycotoxicosis) in livestock and pet animals across the world, there are very few reports of poisoning in wild mammal species.
Mycotoxins are poisonous substances produced by certain species of fungi. For example, Fusarium and Aspergillus fungi which can grow on cereal crops, may be a source of fumonisin toxins and aflatoxin (repsectively) poisoning in domestic animal feeds and human products. In wildlife in the United States, poisoning with mycotoxins has been reported predominantly in birds including some species of ducks and geese which presumably reflects the tendency of these species to feed on arable crops. Ergot is produced by Claviceps fungi growing in grass seed and cereal crops at the end of summer. It can cause disease known as gangrenous ergotism in domestic and wild animals consuming the upper parts of these plants. In Europe there a scattered reports of this condition causing gangrene of the extremities, in deer and moose.
The list of human-activity-related wildlife poisonings that occur accidentally is vast. Often reports of these so-called ‘secondary poisonings’ reflect accidental exposure to high levels of pesticides used in agriculture (e.g. carbamates and organophosphate insecticides, although many of these substances are banned in Europe) or consumption of poisons (e.g. anticoagulant compounds) used in pest control programs by non-target species. Furthermore, predator species or scavengers may be affected after consuming poisoned prey or inappropriately disposed of carcasses.
Bio-accumulation, is the process by which a substance builds up in an organism due high levels of intake, possibly exceeding the ability to break-down or excrete it. Bio-magnification refers to the increasing concentration of a poison along the food chain and may explain why, in some cases, end-consumers may show signs of poisoning whilst prey animals do not.
Intentional poisoning of wildlife species can be seen in some areas where the target birds or animals are considered by some to be pests. Examples of this include the laying of poisonous baits for red kite and other birds of prey that may predate farmed partridge and pheasant chicks. Such practices are illegal and suspicion of intentional wildlife poisoning should be reported to the police.
Infectious Diseases of Wild Mammals and Birds in Europe (1). Somerset, GB: Wiley-Blackwell, 2012. ProQuest ebrary. Web. 30 September 2016.
Philippe Berny and Jean-Roch Gaillet. Acute poisoning of red kites (milvus milvus) in france: data from the sagir network. Journal of Wildlife Diseases Apr 2008, Vol. 44, No. 2 (April 2008) pp. 417-426
Ward B. Stone, Joseph C. Okoniewski and James R. Stedelin. Poisoning of wildlife with anticoagulant rodenticides in new york. Journal of Wildlife Diseases Apr 1999, Vol. 35, No. 2 (April 1999) pp. 187-193
Y-K. Kwon, S-H. Wee and J-H. Kim. Pesticide Poisoning Events in Wild Birds in Korea from 1998 to 2002
Journal of Wildlife Diseases Oct 2004, Vol. 40, No. 4 (October 2004) pp. 737-740
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