(e)++Pathogens+-+specific+examples


 * __(e) Pathogens – specific examples __**

(11) Choose one human bacterial disease and use it to answer the following questions. The human bacterial disease discussed is tuberculosis. __Causes﻿__ Tuberculosis is a disease caused by mycobacteria, usually //Mycobacterium tuberculosis// in humans. The infection begins when mycobacteria reach the pulmonary alveoli, where they invade and replicate in alveolar macrophages. The bacteria are then picked up by cells which can transport the bacilli to the lymph nodes. The TB bacteria can then further spread inot other tissues and organs via the bloodstream. It can affect all parts of the body including the brain, the kidneys and the bones; but most commonly it affects the lungs (Pulmonary Tuberculosis). Image of Mycobacterium

(b) How is this disease transmitted? Tuberculosis is spread through the air when people suffering from active pulmonary TB cough, speak, sneeze, or spit. By doing so they expel infectious droplets; each one of these droplets may transmit the disease, since the infectious dose of tuberculosis is very low and inhaling less than ten bacteria may cause an infection. A person with active but untreated tuberculosis can infect 10–15 other people per year. TB can also be transmitted by eating meat infected with TB. //Mycobacterium bovis// causes TB in cattle. However, it is no longer a threat in areas where pasteurization of milk and the health of cattle are strictly supervised. (c) What effects does it have on the human body? The first stage of the infection usually lasts for several months. During this period, the body's natural defenses (immune system) resist the disease, and most or all of the bacteria are walled in by a fibrous capsule that develops around the area. In 10% of cases, the disease develops beyond this stage - and is referred to as TB infection. In the secondary stage, there might be a slight fever, night sweats, weight loss, fatigue and various other symptoms, depending on the part of the body affected. The germ multiplies rapidly and destroys/ consumes the tissues of the lungs (or the other affected organ). When the lung is affected, it results in diminished respiratory capacity, associated with other symptoms. There might also be chest pain and shortness of breath. When other organs are affected, even if treated adequately, it may leave permanent, disabling scar tissue. This secondary stage, if affecting the lungs, is the contagious stage - when the bacteria can be spread to others. = (12) AIDS (as an example)  = = (a) Cause? = = AIDS is caused by the weakening of the immune system by the HIV virus. = = The Human Immunodeficiency Virus (HIV), is a virus that infects cells of the immune system. It reduces the number of lymphocytes that are actively involved in the production of antibodies. = = As a result, the infected person makes a much lower number of antibodies and is therefore much more likely to develop a disease. These diseases are called opportunistic diseases and they are the major cause of death of people who have been infected with HIV and developed AIDS. = = A person is diagnosed with AIDS when s/he shows one 　 or more “indicator illnesses” or based on the results of a 　 blood test in which the number of certain lymphocytes 　 are counted. = = (b) Transmission? = Transmission of the HIV virus can take place via: blood semen vaginal secretions breast milk Blood and semen contain the highest concentration of the 　 HIV virus. The most common transmission of the HIV virus occurs during: unprotected sexual contact (no condom), either vaginal or anal contact sharing injection needles (usually by people addicted to intravenously-used drugs) mother to child during birth or breastfeeding = (c) Effect on the human immune system  = The fight between the virus and the immune system for supremacy is continuous. Our body responds to this onslaught through production of more T-cells, some of which mature to become helper T-cells. The virus eventually infects these targets and eliminates them, too. More T-cells are produced; these too become infected, and are killed by the virus. This fight may continue for up to ten years before the body eventually succumbs, apparently because of the inability to any-longer produce T-cells. This loss of helper T-cells finally results in the complete inability of our body to ward-off even the weakest of organisms (all kinds of bacteria and viruses other than HIV) which are normally not ever a problem to us. This acquired condition of immunodeficiency is called, AIDS. = (d) Infection with HIV results in the progressive destruction of T-lymphocytes. Explain why this leads to an increasing number of opportunistic infections in AIDS sufferers = = (e) Social implications? =
 * People with HIV/AIDS can suffer from stigma and discrimination.
 * Women are more likely to contract HIV from sex with an infected partner than men. This further increases the inequality between men and women in some countries.
 * People who die as a result of HIV/AIDS are often at an age where they are the most productive members of society. In countries were AIDS causes many deaths, a relatively large proportion of the work force may be removed, delaying economic growth.
 * If both parents die because of AIDS, the country will need to spend resources on caring for the orphans.
 * If one adult in a household suffers from HIV/AIDS, she/he may face unemployment and not be able to earn an income. This may push the entire household into poverty, further reducing the chances of obtaining anti-viral drugs.
 * Poverty in itself increases the chances of contracting HIV/AIDS due to a lack of information (no school) and/or being forced to have sex in exchange for food/money. Also the incidence of rape may increase, which is also a factor in spreading HIV/AIDS.
 * It is expensive to treat people with HIV/AIDS so obtaining insurance might be a problem.
 * Use of condoms increases.