World of Bison

MYCOTOXINS â?? NEW CHALLENGE FOR HUMAN AND ANIMALâ??S HEALTH

MYCOTOXINS â?? NEW CHALLENGE FOR HUMAN AND ANIMALâ??S HEALTH

 

Dr. Kedar Karki

 

 

Mycotoxins are the toxic chemicals produced by fungi for a variety of reasons. The word mycotoxin had been derived from Greek mykes, mukos as “fungus” and from  Latin toxicum as “poison” is a toxic secondary metabolite produced by an organism of the fungus kingdom, including mushrooms, molds, and yeasts. These include to attack or gain access to hosts by helping to dissolve cell membranes, or as protective measures against encroaching organisms. The production of mycotoxins within the fungus depends on food sources and the particular enzymes of the fungus and other environmental factors. Mycotoxins are usually not found in spores, but are generally produced in the next stage, that of mycelium. Many mycotoxins, such as Mycotoxin T2 (Fusariotoxin) or the Amanita-toxins can be lethal to animal and human. Others, such as Psilocybin, are entheogenic, producing altered states of consciousness that are usually associated with shamanism/religion. Others, such as the ergot derivatives are used for migraine and post-partum hemorrhage. Still others, such as penicillin, Fusaric acid, and Wortmannin have antibiotic effects, and Zearelenone with anabolic effects, but which may or may not be beneficial to the host organism depending on the mode of administration and dose.

 

Filamentous fungi, especially those of the Fusarium, Myrotecium, Trichoderma, and Stachybotrys genera, produce trichothecenes mycotoxins. These mycotoxins are extremely heat stable and resist ultraviolet light inactivation.

Mycotoxins are secondary metabolites of molds that have adverse effects on humans, animals, and crops that result in illnesses and economic losses. The worldwide contamination of foods and feeds with mycotoxins is a significant problem. Aflatoxins, ochratoxins, trichothecenes, zearelenone, fumonisins, tremorgenic toxins, and ergot alkaloids are the mycotoxins of greatest agro-economic importance. The majority of mycotoxins of agricultural importance are produced mainly by three genera of fungi- Aspergillus, Fusarium and Penicillium. Mycotoxins are present in more than 30% of the cereal produced in the world.

  The reasons why fungi produce Mycotoxins are largely unknown, but may be as a result of growing stress to the fungus, through harvesting or the use of fungicides. The type and amount of mycotoxins produced is influenced by many factors, including geographic location, climate and agricultural practices. Prediction is complicated especially by the fact that the toxins may persist long after the fungus is removed, and also that a fungal infestation does not always mean that mycotoxins contamination has occurred. Some molds are capable of producing more than one mycotoxin and some mycotoxins are produced by more than one fungal species. Often more than one mycotoxin is found on a contaminated substrate. Factors influencing the presence of mycotoxins in foods or feeds include environmental conditions related to storage that can be controlled. Other extrinsic factors such as climate or intrinsic factors such as fungal strain specificity, strain variation, and instability of toxigenic properties are more difficult to control.

 Health implications

 

Given their wide variety of chemical structures and the synergy with which various mixtures of Mycotoxins can occur in feed grains, it is to be expected that they should exhibit a range of symptoms. Indeed, the toxic effects can differ from animal to animal as well as between species. In general terms, toxicity manifests itself as reduced feed intake (can be as serious as anorexia), reduced growth and production as well as immune and reproductive abnormalities. Mycotoxins can appear in the food chain as a result of fungal infection of crops, either by being eaten directly by humans, or by being used as livestock feed. Mycotoxins greatly resist decomposition or being broken down in digestion, so they remain in the food chain in meat and dairy products. Even temperature treatments, such as cooking and freezing, do not destroy mycotoxins.

 

If the mycotoxins are ingested, they produce a lethal illness called alimentary toxic aleukia (ATA) with the following initial symptoms: abdominal pain, diarrhea, vomiting, and prostration. This progress into fever, chills, myalgias, and bone marrow depression causing granulocytopenia and sepsis. If the patient survives these initial stages, the next set of symptoms are painful pharyngeal/laryngeal ulceration and diffuse bleeding into the skin, bloody diarrhea, hematuria, hematemesis, epistaxis, and vaginal bleeding.

 

Mycotoxins can enter the body through the skin, stomach, or lungs and inhibit protein and nucleic acid synthesis. The first cells attacked are the rapidly dividing cells such as bone marrow, skin, mucosal epithelia, and germ cells. When skin is exposed to mycotoxins, burning, redness, blistering, and skin necrosis occur. When nasal mucosa is exposed to mycotoxins, this produces nasal pain, sneezing, rhinorrhea, dyspnoea, wheezing, cough, and blood tinged saliva and sputum. Exposure of the eyes to mycotoxins produces eye pain, tearing, redness, and blurred vision. Once the mycotoxins enter the system, symptoms include weakness, prostration, dizziness, ataxia, loss of coordination, and in fatal cases, tachycardia, hypothermia, and hypotension. Death may occur in minutes, hours, or days.

The main organs affected are the liver, kidneys, reproductive tract and upper alimentary tract. In poultry, the primary sites are the initial contact organs- the skin around the beak and head, the mucosal surfaces of the beak, and the digestive tract.

 

Thus, reduced feed intake, digestive disorders such as diarrhea, and reduced growth rate, decreased efficiency and reduced rate of lay are common. Liver damage, hemorrhage, kidney disorders and bone lesions are often seen in cases of acute toxicity. The specific symptoms have been found to depend on species, age, sex and especially on the toxin(s) present. Aflatoxin B1 is one of the most potent animal carcinogens found in nature. Young animals which consume 50-100 ng/kg feed on a regular basis can develop fatal liver cancer, though older animals may show only minor symptoms. Susceptibility also varies between species. Aflatoxin contamination of animal feed is not only a hazard to animal health. Although contaminated feed corn containing 100ppb aflatoxin can be fed to nonlactating animals (300ppb for finishing cattle and 150ppb for finishing pigs) without damage to the animals or without harmful toxin or its metabolites appearing in the edible parts of the animals, lactating animals pose a higher risk. Aflatoxin M1 is a metabolite of Aflatoxin B1, and appears in milk at levels which are 3-5 percent of the level of aflatoxin B1 in the feed consumed. Ochratoxin A has been found to appear in edible tissues of animals that received contaminated feed shortly before slaughter. Furthermore, it has also been detected in sausages, ham and bacon. It is a further danger to human health in that after ingestion it can be passed into the blood sera and milk.Mycotoxins have various acute and chronic effects on humans and animals (especially monogastric) depending on species and susceptibility of an animal within a species. Ruminants have, however, generally been more resistant to the adverse effects of mycotoxins. This is because the rumen microbiota is capable of degrading mycotoxins.

There has been problem of disease like Deg Nala in buffaloes in many parts of tarai has been implicated due to moldy rice straw feeding in Pakistan, India, and Nepal since 1939.Likewise there has been too often reports about sudden death of mules in mountain area when these animals are in rout during transportation which are mainly fed grains like maiza, gram. Till dates finding had suggested the likely cause might be due contamination of the grains with fungus like Penicillium and Aspergillus.Likewise now a days commercial broiler farmers in around Kathmandu valley are facing problems in their grown up market age broiler dying suddenly during monsoon season laboratory finding have indicated the cause may be due to contamination of these birdâ??s feed by fungus like Penicillium and Aspergillus.

First time in Nepal farmers in Midwestern parts in districts like Banke immediately after monsoon last year have suffered the loss of goats due to polyneuropathy causing the paralysis of goat on laboratory investigation concern expert found the fodder in pasture in that area was being heavily contaminated with fungus Penicillium.In the light of above facts contamination of grains and livestock products are in increasing trend and many new diseases in livestock and poultry are being identified as fungal origin public consumption of these product may pose a health concern. But how much we are aware about it.

The economic impact of mycotoxins include loss of human and animal life, increased health care and veterinary care costs, reduced livestock production, disposal of contaminated foods and feeds, and investment in research and applications to reduce severity of the mycotoxin problem. Although efforts have continued internationally to set guidelines to control mycotoxins, practical measures have not been adequately implemented.