Diseases and Their Causes Blaine Hebert, Pasadena City College & Dr. Geofery Swain, Milwaukee Assistant Director of Public Health February, 1998 (This information was compiled from Foundations in Microbiology, Talaro & Talaro, 2nd ed) Diseases caused by prions (non-DNA and non-RNA diseases caused by a simple protein): Scrapie; in sheep causes a skin rash that results in sheep rubbing against posts and trees. Mad Cow Disease; believed to be transmitted from sheep to cows through protein supplements made from sheep parts. This was an important political issue in Great Britain in the mid 90's. Creutzfeld-Jakobs Disease, degenerative brain disease that may be caused by eating cows infected with Mad Cow disease and cause of considerable political anguish in England where beef production has dropped considerably following several suspected cases of this disease, which some people believe is connected to eating beef. Kuru, a disease in New Guinea, now rare, caused by a prion received from ritual eating of the uncooked brains of dead relatives by women and children. Diseases caused by viruses: Colds, most caused by about 200-300 species of rhinoviruses, paramyxoviruses, enteroviruses, coronaviruses, reoviruses and adenoviruses. Causes sneezing, runny nose, nasal congestion, headache and coughing. Herpesviruses, members of this group cause cold sores, genital herpes and chicken pox, shingles and Epstein-Barr virus. They are persistent viruses, some living in nerve cells and causing repeated sores or outbreaks. Cold Sores, caused by Herpes simplex type I virus which usually lives in the brain stem or one of the facial nerves and reinfects the lips, often following periods of stress or injury. Genital herpes (Herpes simplex type II) lives in the spinal cord and can repeatedly infect the genitals. Usually received from sexual contact with an infected individual. Herpes type II oral infections and Herpes type I genital infections are becoming more and more common. For example, oral sex with a partner who gets cold sores can cause genital herpes. Chicken pox is usually a mild virus that causes itchy poxes (small red sores) in children. But the same virus can live in the spinal nerves and cause shingles rashes in later life. Mumps, is a virus that causes painful swelling of the glands in the neck usually in children. Caused by a Paramyxovirus. In 20%-30% of young adult males this virus can cause infection of the testicles. This is why mumps vaccine is part of the required childhood vaccine schedule. Other common childhood immunizations include vaccines against viruses such as measles, rubella (German measles), polio, and hepatitis B. Measles is usually a mild childhood disease, but outbreaks frequently cause deaths of very young children at a rate of about 1 in 500. The disease causes a dry cough, headache, followed by a rash over most of the body. A similar but separate disease is German Measles which can cause birth defects in the fetuses of pregnant women. Flu (or influenza) is an infection of the ciliated lining of the nose and throat. It is easily spread and causes fever, headache and coughing. New strains seem to come from areas where ducks and pigs are raised near humans. It can cause death in about 1 case in 1000, usually in the elderly and very young. Warts are usually caused by one of the papillomaviruses. They can occur anywhere on the body, commonly on children and young adults. Genital warts are considered to be the most common form of STD in the United States and is linked to some types of cancer. They are most especially linked to development of cervical cancer in women; that's why all sexually active women should have annual pap smears (in order to detect the cellular changes on the cervix caused by human papiloma virus). Hepatitis is any viral disease infecting the liver. There are three major forms of hepatitis; hepatitis A, B and C. A is not generally as serious, A & C are caused by RNA viruses. Hepatitis A is generally caught from food contaminated by unwashed hands of food handlers. Hepatitis B is a serious disease caused by a DNA virus. This disease is usually caught from exposure to contaminated blood (such as by sharing needles when using IV drugs). It causes swelling of the liver, painful joints, a skin rash and jaundice (a yellow skin condition). Additionally, the risk of liver cancer is higher in persons who have had hepatitis B & C. Polio is a serious disease of the nervous system that can cause nerve damage, permanent paralysis or death. Because of vaccinations this disease is now rare in the U.S. but is still a problem in some countries. Two vaccines are used to prevent polio. One, the Salk vaccine is made from killed virus, the Sabin vaccine is a live but weak virus that is capable of causing a normally harmless disease that can spread to other family members and contacts giving them immunity. About one case in four million of these infections can result in an actual polio case. Yellow Fever is usually a tropical disease from monkeys or other humans transmitted by mosquitoes. This disease caused enormous numbers of deaths in the US and tropical countries before its cause was found and mosquito populations were controlled. St. Louis encephalitis is a disease transmitted from birds or horses to humans through mosquitoes that can cause serious brain damage. Symptoms are fever, headache, memory loss and heart disorders. In some areas colonies of chickens are maintained and checked for signs of infection. Rabies is a deadly disease with no known cure. Vaccination can prevent death by the disease if it is given immediately after the infection, but there is only one know case of someone surviving an actual case of rabies infection. Infection is from the bite or saliva of an infected animal. It is even possible to get rabies from viruses entering the body through the eye (this is common in workers handling cats that will spit when upset). The disease attacks the nervous system causing dementia and death. One of the late symptoms of the disease is difficulty swallowing which can cause a fear of water; this gives rabies its other name: hydrophobia (fear of water). HIV is the virus that causes AIDS. This RNA virus is normally transmitted by sexual contact or contact with infected body fluids. HIV does its damage by infecting T cells, which are an important part of the body's immune system. Because HIV kills T cells, the infected person becomes less and less able to fight off other (usually bacterial or parasitic) infections. HIV is currently though to be incurable. Diseases caused by bacteria: Acne is usually caused by infection by a common skin bacteria (Staphylococcus aureus). It is believed to occur more often in young adults because of hormonal changes during growth. Food poisoning is usually caused by two groups of bacteria: the botulin and salmonella bacteria. Botulism food poisoning is caused by the botulin bacteria Clostridium botulinum and is found in improperly prepared food or food that is not properly preserved. The toxin causes paralysis of muscles. Some rare cases of infant botulism have been caused by feeding honey in infant formulas. Salmonella food poisoning is caused by one of the Salmonella bacteria, usually S. typhimurium or S. enteriditis. This disease is often caused by poorly cleaned food especially eggs or chicken. It causes diarrhea, vomiting and fever. Campylobacter jejuni is replacing Salmonella as the most common and serious type of food poisoning in the us. Campylobacter and Salmonella can be cultured from a large percentage of grocery store chicken. This is another reason to cook food well. E. coli 0157:h7 is a particular strain of Eschericia coli that has caused some recent cases of fatal food poisoning. It can be contracted by eating undercooked contaminated beef. E. coli is a normal part of the gut community. Typhoid fever is a serious disease of the digestive system caused by Salmonella typhi. It causes fever, and diarrhea, is easily transmitted and can be deadly. Strep throat is caused by one of the Streptococcus bacteria. Strep throat is a painful sore throat that can occasionally lead to more serious types of infections including infections of the heart and kidneys. Tetanus is a serious disease caused by Clostridium tetani, a common type of soil bacteria. The bacteria grow in infected wounds causing tetanus or lockjaw; uncontrolled muscle spasms. Tetanus is one of many bacterial infections that are also prevented by childhood immunizations. Others include pertussis, diphtheria, and hemophilus b. Whooping cough or pertussis is a serious disease of very young children in which one of the symptoms are fits of coughing followed by a deep hoarse inhalation which sounds like "whoop". The disease is not rare in adults who can transmit the bacteria to children. This is one of the diseases that children are commonly vaccinated against. Unfortunately, because many "enlightened" parents afraid of the side effects refuse to vaccinate their children this disease is still a cause of infection and death in developed countries. Pneumonia is an infection of the lungs caused by several bacteria and some viruses. The most common causes are Streptococcus pneumoniae, which causes such symptoms as chills shaking, fever, and rust colored mucus. Other infections are caused by Staphylococcus aureus, Mycoplasma pneumoniae and the mold Aspergillus fumigatus. Pneumocystis carinii is a fungus- like organism that causes pneumonia and death in AIDS patients. Syphilis is an STD caused by the bacterium Treponema pallidum. The first stage is usually a hard bump, called a chancre, at the site of infection which heals within 3 to 6 weeks. After 3 weeks to six months the secondary stage appears with fever, headache, sore throat and a rash. These symptoms clear eventually and may be followed by tertiary syphilis which can cause blindness, brain and nerve damage, heart damage and painful tumors. The disease can also be passed on to a woman's fetus. Gonorrhea is an STD caused by the bacterium Neisseria gonorrhoeae. This organism does not survive well outside of the body and most cases are from sexual contact. Symptoms are painful urination and a yellow discharge (pus) from the urethra in men and a yellow or bloody discharge in women. In some cases the bacteria can invade the joints or other parts of the body. Gonorrhea, and chlamydia (a similar STD) can lead to painful pelvic inflammatory disease and infertility in women. Chlamydia is the most common bacterial STD in the US. The organism that causes chlamydia (Chlamidia trachomitis) is an extremely simple bacteria, that only lives inside infected cells. Chlamydia originally was thought to be a virus and for a long time was not able to be categorized as either virus or bacteria. Cholera is a dangerous disease caused by infection of the intestinal tract by the bacteria Vibrio cholerae. This bacteria causes a very serious diarrhea that can cause death in 48 hours with a mortality rate of 55% in untreated cases. Treatment is with sugar/salt solutions to replace lost body fluids and antibiotics. It is transmitted by contaminated water, poorly cooked shellfish or contact with an infected person. Plague, is still a common disease in some parts of the world (including Southern California) where it lives in wild animal populations. Plague causes both black death and red death (bubonic plague and pneumonic plague). The organism Yersinea pestis can be transmitted from rats to humans through fleas. In western US this disease lives among native rodents and occasionally causes outbreaks in rodent populations and infects humans. Tuberculosis. This disease, caused by Mycobacterium tuberculosis, infects more people worldwide than any other bacterial infection. It infects the lungs, and is contracted by breathing air in a closed space with an infected individual who is coughing. Of the many people who have been exposed to and infected by TB, only about 1 in 10 develops symptoms of active TB disease (cough, fever, weight loss). However, the risk of converting to active disease increases with the length of time the infection has been present. There has been a significant increase of TB in the US in the past 10 years, primarily due to the fact that people who are HIV positive are much more at risk to develop active tubercular disease. It is worthwhile to note that any bacterium can develop antibiotic resistance. TB, for example, has developed strains that are resistant to every known antitubercular drug. Staph, a common skin bacterium, has become resistant to Methicillin, and more recently even to the best anti-staph antibiotic available, Vancomycin. Many bacteria that used to be sensitive to Penicillin are now resistant to it. In the 1960s and 1970s many people thought that bacterial infections would soon be a thing of the past. But now, they seem to be becoming more and more problematic. Other important bacterial infections include: Bladder infections. More common in women, these are usually caused when fecal bacteria (E. coli, Klebsiella, etc) ascend into the urinary tract. They can progress to very serious kidney infections. Impetigo. A superficial skin infection usually caused by staph, strep, or a combination. Usually not serious, but highly transmissible. Usually found in young children (toddlers and primary school age). Diseases caused by protists: The protist Trichomonas vaginalis is one of the most common causes of vaginal itch. This common infection may have few symptoms or may cause a frothy green to yellow vaginal discharge, swelling and painful itching. In men there may be few symptoms or a white discharge. (Also see Candida albicans under Fungi) Giardia; the protist Giardia lamblia is often called traveler's diarrhea. This is an intestinal disease usually caught from drinking contaminated water. Wild animals commonly carry this intestinal organism and release it into the water. Cysts (resting stages) can survive for years and only a few can cause the disease. This organism is often difficult to kill requiring boiling or iodine to kill the cysts. Amebic dysentery is one of the most common protozoan infection in the world. The organism Entamoeba histolytica is transmitted by contaminated water and poor sanitation. Symptoms include diarrhea, bloody stools, abdominal pain and weight loss. The organism occasionally invades other parts of the body. Chagas disease is a tropical disease caused by a flagellated protist (Trypanosoma cruzi) that is transmitted by the bite of the kissing bug (which often bites near or on the lips). A local, mild form occurs from the bite of our own species of kissing bug in the foothills above Southern California. Malaria is one of the most serious diseases in the world today. Caused by four species of protists in the genus Plasmodium the organism is usually transmitted from one infected person to another through bites of infected mosquitoes. The organism lives in liver and blood cells. Symptoms include bouts of chills followed by fever as the organism spread from blood cells in waves. African sleeping sickness is transmitted by the bite of the tsetse fly. This disease keeps large portions of Africa uninhabitable by man or domestic animals. The organism Trypanosoma brucei causes fever, joint pain, enlarged spleen and death in four weeks to several years. Uncontrolled sleepiness often occurs in the day with sleeplessness at night. Diseases caused by fungi There are about 39 species of fungi that can cause skin, hair and nail infections: Ringworm is a ring shaped infection of the skin caused by the spread of a fungus from a central point. It can occur in the scalp, beard, or other parts of the body. Jock itch usually occurs in the groin area of men, especially in humid climates. Athlete's foot is an infection of the foot, frequently caught from wet locker rooms. Ringworm of the nail causes white patches of the nail and thick, cracked or loose nails. Thrush is a mouth infection common in small children or the elderly. This condition is caused by infection by the fungus Candida albicans. Candida is a common mouth and intestinal fungus that occasionally invades other parts of the body and is common in diabetics (the yeast likes elevated blood sugar levels) and in people with immune deficiency. Vaginal yeast infection is also caused by Candida albicans. It is not clear what is the exact cause of most vaginal infections though hormonal changes and hygiene practices have been suspected. Valley fever is a fungus disease caused by a soil fungus found in desert soils. Humans get this disease from dust containing the spores that are inhaled into the lungs. The organism, Coccidioides immitis, can cause cold-like symptoms or serious lung and body infections. Following the 1994 Northridge earthquake about 200 persons were found to be infected with this organism from dust stirred up in landslides. Severe liver damage may also be caused by eating poisonous mushrooms. Diseases caused by plants: Poison ivy contains an oil (urushiol) that can cause a severe rash in sensitive individuals. The rash results from contact and sensitization of the body by contact (usually repeated contact) and can be only a small itchy patch to widespread blisters and sores. The oil can be removed by washing the areas immediately after contact with soap or detergent. Nettles have stinging hairs that can inject an irritating toxin into the skin after contact. The toxin generally lasts about a half hour and produces a burning or itching sensation. Plant toxins are often contained in leaves or other parts of the plants and can result in serious harm or death if eaten. Diseases caused by animals: Tapeworms are large flatworms that live in the intestines of many animals. The beef tapeworm (Taenia saginata) lives in human gut and lays large numbers of eggs that are released into the feces. If these are eaten by a cow the eggs hatch and form small muscle cysts each containing a young tapeworm. If eaten as poorly cooked beef by a human the tapeworm hatches out and attaches to the intestines where it lives and reproduces. The beef cysts are called measles and poor beef is referred to as measly. Other tapeworms have similar cycles; the dog tapeworm eggs must be eaten by a flea which is then eaten by a dog to infect its intestine. Tapeworms usually cause few reactions, but can occasionally be dangerous when eaten by animals other than its normal host. Liver flukes are flatworms that have a complex life cycle, some alternating between snails and humans. The adult lives in the liver or gall bladder and releases eggs into the feces where the young hatch and reproduce in snails. After this stage they swim out and invade another animal or a human causing fever, vomiting, diarrhea and pain. These animals are usually found in poorly developed countries such as South America, Asia or Africa where poor sanitation and wet agriculture are common. Round worms are a group of worms that are very common inhabitants of animal digestive systems. Ascaris, pinworms, hook worms and filarial worms (the cause of elephantiasis) are important parasites. Pinworms, Enterobius vermicularis, live in the intestines, mostly of children. Adult females lay eggs around the anus where they cause itching. The eggs are spread around the environment where poor hygiene causes infection. Hookworms live in the intestines but the eggs hatch in the soil and infect by penetrating the skin. At one time infections of hookworms were common in agricultural workers and were the cause of prejudices against different groups as being lazy or ignorant. With better sanitation and shoes this has become a much less serious disease. The common species in the US is Necator americanus. Trichinosis is caused by the roundworm Trichinella spiralis. This disease is contracted by eating poorly cooked meat, usually pork, from which the worm hatches, mates and reproduces. The worms burrow into muscle and wait there to be eaten by another animal. There is no known cure. Filarial worms cause two important diseases; elephantiasis and river blindness. Wuchereria bancrofti, which causes elephantiasis, is transmitted by a mosquito and lives in the lymph system. The worms block the lymph system preventing return of fluids to the heart. The resulting swelling causes the enlarged limbs that are the symptoms of the disease. River blindness is transmitted by the bite of the black fly along rivers in West Africa. Leeches are external parasites that live in water and commonly attach to swimmers where they drink blood. Some species are used in modern medicine to remove clotted blood from stitches or wounds where they cause little damage. Insects are mostly external parasites, but a few invade the body (a condition called myiasis) where they feed on bacteria or blood. blow flies, screw worm flies and bot flies can invade the skin or migrate through the body tissues. Farm animals are attacked by stomach flies and nose flies. Lice are blood feeding parasites that live in hair. Mites are arachnids, not insects, but they commonly live in, on and around humans as parasites or commensals. Scabies are similar to lice, but they tunnel in the skin instead of living on hair and cause itchy skin rashes. Diseases that have no organismal causes or may be caused by other agents: Cancer Some viruses, such as the human papiloma virus, may promote or actually cause some forms of cancer. Heart disease Some evidence has been found to link heart disease to several types of bacteria and viruses. Arthritis Several bacterial or viral conditions may cause joint inflammation or pain. Stroke At present stroke has no know infectious cause. Copyright (c) Blaine Hebert, 1998, 2007 Permission is granted to reproduce this work only with proper credit to the source and author. Please report any suggestions or errors to the author.
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