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1 CHAPTER ONE BACKGROUND Since times immemorial, all things have been known to interact. This interaction ranges from plants- mineral nutrients relationship to Algae- Fungus relationship (Lichens) and even human- micro organisms relationship. The result of these interaction are diverse in nature, it can be beneficial as in the bacteria in the digestive tract of cattle, while the adverse results ends up in diseases1. Diseases can either be communicable or incommunicable. Communicable diseases are diseases that can be transmitted from one person to another. This may occur by the direct physical contact by common handling of an object that has picked up infective microorganisms through a disease, or by spread of infected droplets coughed or exhaled into the air. Table 1 shows some communicable diseases, their causative agents and mode of transmission. Micro organisms e.g. bacteria, fungus viruses etc are small organisms invisible to the naked eyes but visible by the aid of a microscope that cause various diseases to man and animals alike. Vectors, on the other hand are organisms that carry about these disease- causing micro organisms. Transmission of diseases is by diverse mode. This can be as in the case of AIDSsexual intercourse, blood transfusion; or by insect bite, infected food and water and so on. 1 A disease is a disorder with a specific cause and recognizable signs and symptoms; any bodily abnormality or failure to function properly, except that resulting directly from physical injury the latter, however may open the way for disease. 2 Table 1 Some Diseases, their Mode of Transmission and Causative Organisms Disease AIDS Chancroid Chicken Pox Cholera Cryptosporidiosis Diphtheria German Measles Transmission Mode Sexual Intercourse, Blood Transmission Sex Air Borne Water Borne -----Air- Borne Air Borne Micro organism Virus Bacterium Virus Bacteria Protozoa Bacteria Virus Giardiasis Gonorrhea Contact, Sex Sex Protozoa Bacterium Hepatitis Influenza Leishmaniasis Leprosy Malaria Measles Mumps Pneumonia, Poliomyelitis Rabies Shigellosis Sleeping Sickness Smallpox Strep Throat Syphilis Water, Blood, Feaces Air Borne Sand fly Bite ------Mosquito Air Borne and Body Ants Air Air Water, Food Animal Bite (Infected Dogs) Water Tse-Tse Air ------Sex Virus Virus Protozoa Bacteria Protozoa Virus Virus Bacteria Virus Virus Bacterium Protozoa Virus Bacteria Bacterium Tetanus Toxoplasmosis Tuberculosis Typhoid Fever Whooping Cough Yellow Fever Water And Air Raw meat Air Water- Borne Air Aedes Mosquito Bite Bacteria Protozoa Bacteria Bacteria Bacterium Virus 3 CHAPTER TWO SOME COMMUNICABLE DISEASES 2.1 Influenza- a viral disease Influenza, also known as flu, is a contagious infection primarily of the respiratory tract. Influenza is sometimes referred to as grippe. Influenza is caused by a virus transmitted from one person to another in droplets coughed or sneezed into the air. It is characterized by cold-like symptoms plus chills, fever, headaches, muscle aches, and fatigue. Most people recover completely in about a week. But some people are vulnerable to complications such as bronchitis and pneumonia. This group includes children with asthma, people with heart or lung disease, and the elderly. In addition to humans, influenza occurs in pigs, horses, and several other mammals as well as in certain wild and domesticated birds. At least some influenza viruses can jump from one species to another. Also Avian Flu that occurred briefly recently. Because influenza is highly contagious and spreads easily, it usually appears as epidemics—that is, outbreaks involving many people. If an outbreak spreads around the world—not uncommon in this age of rapid international travel—it is called a pandemic. 2.1.1 Cause Today, scientists know that members of the family Orthomyxoviridae, a group of viruses that infect vertebrate animals, cause influenza. The virus consists of an inner core of the genetic material ribonucleic acid (RNA) surrounded by a protein coat and an outer lipid (fatty) envelope. From this envelope, spikes of proteins called hemagglutinin and neuraminidase stick out. 4 Once a person has been infected by a specific strain of influenza, he or she has built up immunity to that strain in the form of antibodies. The person’s immune system then can recognize the strain’s hemagglutinin or neuraminidase and attack them if they reappear. The antibodies offer some protection against antigenic drifts, Scientists do not understand exactly what causes antigenic shifts. One leading theory suggests that a human strain and an animal strain recombine to create a new strain. This strain has the ability to infect humans but has antigens on its surface that are unfamiliar to the human immune system. 2.2.1 Transmission Influenza viruses pass from person to person mainly in droplets expelled during sneezes and coughs. When a person breathes in virus-laden droplets, the hemagglutinin on the surface of the virus binds to enzymes in the mucous membranes that line the respiratory tract. The enzymes, known as proteases, cut the hemagglutinin in two, which enables the virus to gain entry into cells and begin to multiply. These proteases are common in the respiratory and digestive tracts but not elsewhere, which is why the flu causes primarily a respiratory illness with occasional gastrointestinal symptoms. Although an influenza epidemic can occur at any time of year, flu season in temperate regions typically begins with the approach of winter—November in the Northern Hemisphere, April in the Southern Hemisphere. Flu viruses spread more easily during cold weather. 2.1.3 Prevention and Treatment There is no specific cure for influenza. Recommended treatment usually consists of bed rest and increased intake of nonalcoholic fluids until fever and other symptoms lessen in severity. Certain drugs have been found effective in lessening flu symptoms, but 5 medical efforts against the disease focus chiefly on prevention by means of vaccines that create immunity.(Microsoft Encarta, 2009) 2.2 Tuberculosis- bacterial disease Tuberculosis (TB) is a chronic or acute bacterial infection that primarily attacks the lungs, but which may also affect the kidneys, bones, lymph nodes, and brain. The disease is caused by Mycobacterium tuberculosis, a rod-shaped bacterium. Many people harbor the bacteria but have no symptoms of disease. When symptoms develop, they include coughing, chest pain, shortness of breath, loss of appetite, weight loss, fever, chills, and fatigue. 2.2.1 Transmission The TB-causing bacteria are transmitted from person to person, usually in infected air droplets. When someone who has symptomatic TB coughs, sneezes, or speaks, small particles that carry two to three bacteria surrounded by a layer of moisture are released in the air. When someone else inhales these particles, the bacteria may lodge in that person’s lungs. A less common route of transmission is through the skin. A person may become infected with TB bacteria and not develop the disease. The immune system may destroy the bacteria completely. Someone with an inactive infection cannot transmit the disease. 2.2.2 Treatment and Prevention General preventive measures can be taken to reduce the spread of TB in public places. Ventilation systems lessen the chance of infection by dispersing the bacteria. Ultraviolet lighting also reduces, but does not eliminate, the threat of infection by killing TB bacteria in confined spaces. Vaccines, such as the bacillus Calmette-Guerin (BCG) vaccine, prepared from bacteria that have been weakened, are another 6 preventive measure. The BCG vaccine is most effective in preventing childhood cases of TB.(Microsoft Encarta, 2009) 2.3 Toxoplasmosis- protozoan disease Toxoplasmosis, is a common parasitic infection in humans, warm-blooded animals, and birds, transmitted by contact with the microorganism Toxoplasma gondii. The disease normally runs a mild course, with a few noticeable symptoms resembling those of the common cold. If contracted by a woman during pregnancy, however, toxoplasmosis can cause serious birth defects. In people whose immune system has been suppressed by age or other diseases, such as acquired immunodeficiency syndrome (AIDS), toxoplasmosis can cause severe nervous system disease. 2.3.1 Transmission The toxoplasmosis parasite is commonly present in cattle, poultry, and many domestic animals without any harmful effects; however, it continues to live in raw meat after slaughter until the meat is cooked, dried, or frozen for a prolonged period. The two major causes of human toxoplasmosis infection are the consumption of raw or undercooked meat and contact with the feces of the domestic cat. 2.3.2 Prevention A single infection normally ensures immunity. Serious infection by toxoplasmosis can be effectively prevented by the avoidance of raw meat and by ensuring that all rarecooked meats are heated throughout to at least 60° C (140° F). Contact with infected or unfamiliar cats and cat feces should be avoided, and the cat litter box should be emptied every day because the parasite eggs in cat feces do not become infective until two to four days after excretion.(Microsoft Encarta, 2009) 7 CHAPTER THREE CONCLUSION Diseases have diverse causes, which can be classified into two broad groups: infectious and noninfectious. Infectious diseases can spread from one person to another and are caused by microscopic organisms that invade the body. Noninfectious diseases are not communicated from person to person and do not have, or are not known to involve, infectious agents. Since the mode of transmission of most of these diseases are known, and as popularly said that prevention is better than cure, it is the role of the Environmental Engineer to Manage water treatment plants, so as to make potable water available Manage the Solid wastes in the environment Treat wastewater, design good sewage systems and control all sorts of pollution. When all these are properly done, the transmission of diseases will be greatly reduced because of the hygienic and healthy environment that will ensue. 8 References Microsoft Encarta, 2009. Microsoft Corporation. Racamond USA.