Introduction
It is well known that the human, animal and wildlife population is continuously exposed to environmental polluting agents that are harmful to health. Among them are natural and manmade chemicals such as metals, pesticides, organic and inorganic substances, animal venoms, animal and animal toxins including algal growth and industrial wastes to which domestic animals and wildlife are frequently exposed. In recent years, despite the increasing level of regulation in the use and sale of such products in Asia, their commercialization has been intensified. Consequently, many cases of accidental poisoning have occurred. In addition, their continuous use or due to spills the poisoning cases have drastically increased all over the world, particularly in developing countries. There is an ongoing need for careful assessment of the risks caused by exposure to these chemicals. Information on the assessment of toxicity caused by these chemicals mainly comes from human and animal studies. However, some supporting information may also be obtained from clinical and in vitro studies. There are no reliable estimates of how many animals suffer from acute poisonings or due to long term exposure. In general, epidemiology has been particularly helpful in the evaluation of working environment or other environments where exposure concentrations are relatively high. However, several factors limit the use of epidemiological studies by regulatory agencies. For example, it is difficult to define the causal elements in epidemiological investigations, particularly when complex exposures are involved. Another limitation is the frequent movement of animal population and a large number of animal species available in the universe. As such studies on one population under controlled conditions may be difficult to apply to predict health effects on other animal population.
In few developed countries such as the United States, have human poison control centres that collect data on animals also. In developing countries where there is hard evidence of poisoning including sporadic incidents involving livestock and pets, surveillance is conducted by the Veterinary Institutions / departments or by the Wildlife Departments of each country. However, a centralized veterinary poison control/information centers do not exist in most of the countries in the Asia. Therefore, in many Asian countries information related to animal poisoning is either unavailable or inadequate and refers only to isolated case reports when it does exist. Occasionally, epidemiological data on animal poisoning gathered by universities, research institutes, government institutions or independent laboratories has been published in some local journals which at times becomes difficult to trace. It is therefore easy to conclude that available data are inadequate to provide sound estimates of the real incidence of poisonings in animal population and are very likely subject to significant under reporting. This chapter focuses on some of the most important poisonous chemicals and plants in Asia Cand provides an overview of the poisoning episodes that have occurred in Asian countries.
Common Chemical Poisonings in Asia
Animals are exposed to potentially toxic agents on a daily basis but the lack of a central reporting agency for animal poisonings makes epidemiological study difficult. With no mandated reporting, many suspected poisoning cases are managed by the attending veterinarian and forgotten. Accidental or malicious poisonings are due to organophosphorus and carbamate insecticides, fumigants such as aluminium phosphide, zinc phosphide, rodenticides and rarely due to other agents. Poisonings are a serious cause of morbidity and mortality in animals, particularly in domestic animals such as cattle (including buffaloes) and dogs; farm animals such as cattle, sheep, goats, poultry; wild animals and vultures, rarely cats or other animals. Poisoning is also common with, metals such as arsenic, lead, mercury and copper; non-metallic such as nitrate/ nitrites, selenium, fluoride and molybdenum.
Drug poisonings in animals occur commonly due to off-label use of medicines, wrong dosage, negligence, accidental ingestion and deliberate poisonings. Most production animals are kept in some form of confinement, which limits the potential for exposure to toxic agents. However, mistakes in management, such as feed mixing errors or improper ventilation, may result in acute or chronic toxicities in large number of animals.
Another most common source of poisoning includes mycotoxins, botulinum and ionophores such as monensin, lasalocid, narasin and salinomycin that are frequently used as feed additives and coccidiostats for cattle, sheep and poultry. Contamination of feed with antibiotics, pesticides, metals and with other toxins is quite common but their long terms effects are still unknown. For example, in the absence of any systematic survey, the extent to which household kerosene and solid fuels-biomass (wood, agricultural residues, and animal dung) and coal fuels cause long term damage including morbidity and mortality in companion animals is currently unclear.
Plastic bags have invaded our lives, almost all garbage and food waste is disposed in plastic bags. Animals, especially cattle, ingest the plastic and develop complications, which finally result in their death. A lot of cases go unreported. The rumen is one of the four compartments of the cattle's digestive system. The feed enters from the reticulum to the rumen, omasum and finally the abomasum (true stomach). But when the plastic in the reticulum blocks the feed from entering the rumen, suffocation occurs and the animal dies. The scarcity of adequate epidemiologic and exposure investigations in various Asian countries, the potential for short and long-term exposure to a vast variety of agents including house hold use products and chemicals suggest a need for agencies for collection of epidemiological data on human beings and animals.
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