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Lecture 7

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Environmental Science

EESA10 Lecture 7 Biological Hazards and Human Health This lecture overlaps with next lecture on “Food and Food borne Diseases”, because they both have same agents, bacteria, viruses. These can be considered as biological hazards but also they can found in food substances, and cause food borne hazards. Biological Hazards Biological Hazards can be nontransmissible (cannot be transferred from one human to another human). Examples of such nontransmissible diseases include: cardiovascular, cancer, diabetes, asthma. What are cardiovascular diseases? These are diseases related to heart as a result of food (high cholesterol), lack of exercise, lots of stress, smoking, etc. Cancer has many different causes (we cannot specify just one cause for it). Every cancer is caused with many different agents (environmental, genetical, etc.). There is no strong proof that these diseases can be transferred from human to human. Diabetes can be caused because of genetics, food, and obesity. There is no strong evidence that diabetes can be transferred from human to human. Asthma is closely related with some allergens (something in our environment). Everyday many new agents and chemicals and applied to us, and they may cause asthma. There is no proof that asthma can be transmitted from human to human. Transmissible diseases: Diseases caused by bacteria, viruses, or protozoa can be certainly transferred from humans to humans. Bacteria can be cured using anti-biotics. Anti-biotics are medicine that we take if we have bacterial infections. However, Anti-biotics do not work with viral infections. For example, doctors will not prescribe anti-biotics if you have flu, or some other kind of viral infection. If you take anti-biotics for any viral infection or any other infection, you will be overusing anti-biotics (using anti-biotics when we do not need it, or not prescribed by the doctor, or taking anti-biotics more frequently for not very serious disease). What will happen as a result? This can lead to very significant resistance of bacteria to these anti-biotics. Next time, if someone is really serious, and needs anti-biotics, those anti-biotics will not work. This is because growing germ produces resistance to antibiotics. How do the bacterias develop resistance? This is because they are growing very fast. They reproduce very quickly. Also, they very quickly transfer that mutation (that adjustment) to the next generation. This process goes through generation to generation very quickly, much faster than any other organism on the planet can do (High reproductive rate allow them to become genetically resistant quickly). One more reason why bacterias grow resistance to anti-biotics is because of the use of antibiotics in food additives to boost livestock. Veterinarians, agriculture specialists, farmers, they all use antibiotics to prevent diseases in animals. Farmers use antibiotics to prevent disease from happening, and if we consume that kind of meat (with high concentration of anti-biotics), we might become more resistant to antibiotics. Biological Hazards Bacterial Diseases 1) Tuberculosis: When we talk about this disease, we always think about the past (before World War 2, before discovery of antibiotics). This was a big problem. However, it seems that this is not the case. Even today, it is a significant threat to humans. But indeed, this is a very old disease. Scientists found evidence that mummies from Egyptian era had symptoth ofth tuberculosis. This was a very big problem during 18 , 19 , and beginning of 20 centuries. This disease used to run in families, as it was transferred from one family member to another member of the family, very easily. For example, back then, when someone wants to marry someone, they used to look at what family is the bride or groom coming from, does that family have tuberculosis. This is how disease was transferred from one family to another. During 18 and 19 centuries, this disease was related to vampires. This is because sick people from this disease were very pale face, they had watery bloody eyes, and they sometimes spit blood (cough a lot). That time no one knew what tuberculosis was, and people connected these symptoms with vampires. Later on, humans found out the truth, but they could not find any cure, until the discovery of antibiotics. After this discovery, most of the cases (but not all) of tuberculosis were cured. These agents mutate easily, and they change very quickly. This can cause different types of tuberculosis. Most of these kinds of tuberculosis are very resistant to known tuberculosis, which makes it hard to cure. Therefore, they are a threat even today. Some statistics: In 2004, mortality statistics included 14.6 million chronic active TB cases, 8.9 million new cases, 1.6 million deaths, mostly in developing countries. What does chronic active mean? If individual comes in contact with an agent (with this bacteria), that person does not get ill right away. For very long time, that person may not show any symptom of this disease. Active means visible symptoms. Chronic means for a long time. Why is it mostly in developing countries? This disease, in the past and even today, is a socially related disease. Poor people with not adequate supply of food, bad housing, wet walls, unsafe conditions, these get sick more easily because their immune system is reduced (lower) and they catch this disease faster. This disease is always related with social factor. In developing countries, their health system is not very organized, not all people have access to proper health. This adds to one of the reasons for tuberculosis. How can this disease be transferred from person to person? Transmission - cough, sneeze, speak, kiss, or spit of ill person, breathing (basically, any direct contact). This disease most commonly attacks the lungs (through the breathing of the agent). This bacterium is sensitive to UV radiation and oxygen. These were the only ways how people prevented them in the past. They took all clothes, mattress, or anything that came in contact with the ill person (almost 100 years ago), were exposed to the sun and oxygen for long periods of time, because they realized that sun helps. Symptoms include chest pain, coughing up blood, and a productive, prolonged cough for more than three weeks, fever, chills, night sweats, appetite loss, weight loss, paleness and often a tendency to fatigue very easily. Tuberculosis- a growing threat Problem in Africa (mostly southern Africa), South America, Asia. Not a problem in North America, Australia. If you want to travel in tuberculosis affected countries, you have to get a vaccine. Anthrax After 9/11 this disease was of big concerns that it can be used as a biological weapon. Anthrax is normally found in soil (spores of anthrax are usually found in soil). What are the spores? It is a form of bacteria. When bacteria is in unpleasant (something that does not support growth of the bacteria), they become this form to survive, until they are back in the conditions that will be good for them to grow. Bacillus anthracis (large gram-positive, spore-forming bacteria). Gram test is used by microbiologists to test bacterias. These bacterias produce toxins. This toxin is really poisonous. Three major clinical forms of this disease are seen in the literature: Cutaneous – most symptoms are on the skin, and we get contaminated through the skin, Inhalation, Gastrointestinal (foods or drinks). All three may lead to septicaemia and death. What is septicaemia? When the bacterias are in such a huge numbers (reproduce in huge numbers) in our blood that will lead to very serious conditions (will cause septicaemia). No smell or taste. They are so small that they cannot be seen by naked eye. We cannot do anything if we come in contact with the spores. Cannot be transmitted from person to person. Cutaneous Anthrax The most common naturally occurring type of anthrax. More that 95% of all cases of anthrax are cutaneous. The person can be contaminated: after skin contact with contaminated meat, wool, or leather from infected animals, or contact with an animal that was sick with anthrax contamination. The incubation period ranges from 1-12 days. During this period there are no symptoms. After the first 12 days, first symptoms will appear. First symptoms are tiny rash first starting as a bump (like a spider bite, very tiny). Then it will progress into very severe change in the skin (like pimples). Then it will progress into even further severe change. Then it progresses into vesicle and then a painless ulcer. All of these symptoms are painless. Besides these changes in the skin, the person goes through fever, headache, lymph glands swell. This disease is successfully treated with antibiotics if the treatment starts early and about 20% of all cases not treated or not treated in time will result in death. Inhalation Anthrax Inhalation anthrax is the most lethal form. We worry about this form the most. 75% of cases result in death even with all possible supportive care. This is the kind of disease that government believes to be a possible bio- weapon. Person gets sick through inhalation of spores of anthrax. Incubation period 1-60 days. Usually the literature says that the range is from 1 – 7 days, but it can be expanded to 1-60 days. Starts as viral respiratory illness: sore throat, mild fever, muscle aches, flu. Once the symptoms get more severe they may progress to respiratory failure (difficulty breathing and then the person cannot breathe at all) and shock (losing conscience) with developing meningitis (inflammation of the brain or membranes around the brain). Gastrointestinal Anthrax Person gets sick by consumption of raw or undercooked (or uncooked) contaminated meat. Incubational period (period when there is no symptoms) is 1-7 days. Symptoms include nausea, loss of appetite, vomiting, and fever, stomach problems. Once they get more severe these symptoms are followed by abdominal pain, vomiting blood and bloody diarrhoea. 25- 60 % of cases result in death. It is not known how the effect of early treatment can help (its not defined). Bioterrorism Related Anthrax Inhalation anthrax is subject of biggest concern that it can be used as a bio- weapon. How is it possible to do such a thing? Given that spores are not visible, however, they can be mixed with powder. This is how the spores can be transported. It is believed that mail envelopes are one way to transport the spores very effectively. There were a couple of incidents in US that certain government institutions received suspicious mails. What can be suspicious? An inappropriate or unusual labelling, such as excessive postage. Handwritten or poorly typed addresses. Misspellings of common words. Strange or no return address. Marked with restrictions such as personal, combinational, do not X-ray (because
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