Sources of poisoning in livestock

SOURCES OF POISONING

Poisoning and the intensity of harmful effects depend on the form of exposure to toxic substances. Poisoning in human beings may be accidental, intentional, malicious or as an occupational hazard.  Poisoning in animals is generally either accidental or malicious. Intoxication of animals may occur from various sources. However, intentional toxicity in humans may be through abuse (narcotics) or by way of therapy through inadvertent use of drugs (adverse effects of drugs) or for committing suicides.

Sources of poisoning are diverse. These may enter the body by way of contact, inhalation, ingestion etc. may be accidentally, unintentionally or intentionally. Depending on the sources, these are categorized as:

l. Natural sources: Most of the intoxicants of natural origin enter the body through food chain (food or water). Some of the rocks and soils are very rich in some of the toxic minerals e.g. fluorine, arsenic, selenium, lead, etc. Thus, the plants, crops or grasses grown in these areas are rich sources of these intoxicants e.g. high quantity of nitrates in well water, copper in non-graminous plants, nitrate in spinach and selenium in seleniferous plants, etc.

Toxic plants: Certain areas are rich in poisonous plants depending on the agroclimatic conditions, geographical locations, etc. Despite the existence of literally hundreds of toxic plants, plant intoxication is less important except as a local prob­lem. Toxic plants are often refused by animals (as many times they have repulsive smell or contain highly irritant juices) and are eaten only when other herbage is scarce during the peak summer or winter months, e.g. Lantana, Datura, Quercus incana, Acacia leucophloea, Sudan grass, oleander, etc. Some of the fodder crops are very rich in toxic principles such as cyanogenetic glycosides, nitrates, nitrites, oxalates, selenium, etc.

Mycotoxins are another common natural source of poisoning in both, human beings and animals as stored feed stuffs, particularly the concentrates rich in maize, groundnut, rice bran, oil cakes, etc. are very rich in mycotoxins. Several reports of mycotoxicosis in humans, animals and birds are there.

Other natural sources of toxins are: bacterial toxins, venoms and other zootoxins e.g. scorpion toxin, tick toxins, bufotoxin, etc.

Toxic animals: Accidental biting or stinging by poisonous reptiles, insects, etc. often leads to poisoning in animals, e.g. snakes, spiders, scorpions, and bees.

Toxic minerals: Minerals are usually dangerous when they con­taminate water or when accumulate in plants from mineral rich soil. Poisoning may occur in animals after continuous ingestion of forages, feed, feed supplements, or water high in mineral contents, e.g. arsenic, selenium, fluoride, molybdenum, and copper.

II. Man-made sources: Humans are one of the biggest, most common and threatening sources of poisoning. Humans induced poisoning may be accidental, malicious or occupational. These toxicants are common sources of poisoning in animals and human beings as they are readily available and some are potentially toxic.

I.                    Accidental Poisoning: Accidental poisoning may occur when animal takes some toxicant accidentally or is added unintentionally in its feed, fodder or drinking water. Such toxicants come either from natural sources or from manmade sources.

II.                  Malicious Poisoning: Numerous cases of malicious poisoning in animals are recorded every year. In such cases, the toxicant employed is almost a readily available compound, e.g. insecticides, datura, strych­nine and warfarin.

(i) Accidental poisoning: Poisoning through the contamination of food and water with toxicants, industrial effluents, improper and injudicious use of drugs and chemicals including food additives, food preservatives or colouring agents, rodenticides, pesticides, herbicides, fumigants, accidents in chemical processing units like Bhopal gas tragedy (Dec. 3-4, 1984), chemical and biological warfares, radiation hazards or accidents in atomic energy generating units (Chernobyl episode). Similarly, animals are also poisoned due to dumping of industrial wastes and pasture treatments. Careless handling and use of agrochemicals, disposal of containers of chemicals or agrochemicals and domestic materials add to manmade sources of poisoning. Industrial and petrochemical emissions and other environmental pollutants have over the years been recognized as one of the greatest threat not only to human and animal health but also the entire ecosystem. Environmental problems have assumed dimensions of global magnitude.

Industrial toxicants: Contamination of water and herbage by in­dustrial effluents often leads to outbreak of poisonings among animals. Besides this, industrial gases, vapours, and dusts also produce adverse effects on the health of animals, e.g. chromium, nickel, lead, sulphur dioxide, nitrogen dioxide and chlorine.

Agrochemicals: Agrochemicals constitute the biggest source of accidental poisoning in all species. Careless use of pesticides is responsible for innumerable cases of fatal poisoning in animals. Rat baits (rodenticides) are the worst offenders in small animals and birds. Other important agrochemicals causing intoxication in animals are phosphorus, insecticides, fertilizers and fungicides.

Domestic materials: Various commonly used household chemicals and substances may cause intoxication in domestic animals especially pets, e.g. lead paint, disinfectants (mainly phenol), solvents, paraffin, and spot removers.

Therapeutic agents: Drugs when used in high dosage or by improper route may give rise to toxic effects. Toxic reactions occasionally seen following the correct dosage are due to idiosyncrasy or impurities in drugs. Indiscriminate use of drugs may also lead to toxic and undesirable effects in animals.

Food/Feed and water: Almost any food/feed given in excess cause harmful effects. Food becomes toxic, if not stored properly or if get contaminated with harmful substances. Contamination of drinking water is a frequent cause of poisoning, e.g. aflatoxins, rubratoxins, botulinum toxin and castor cake.

Environmental pollution: Many of the adverse effects seen in the animals are due to increasing environmental pollutants, e.g. carbon monoxide and pesticides.

Improper management practices: Improper management conditions often accelerate the toxic effects of toxicants, e.g. poor ventilation, overcrowding, and diet deficient in essential nutrients.

(ii) Malicious or intentional poisoning: It is the unlawful or criminal killing of human beings or animals by administering certain toxic/poisonous agents. Incidence of such poisonings is more prevalent in human beings and less in animals. Yet some of the reports are there where Abrus, strychnine, rodenticides, arsenic trioxide or agrochemicals are mixed in food or drinking water or administered through some other route to kill the animals.