Chapter 23 Communicable Diseases Lesson 1 What causes

Chapter 23 Communicable Diseases

Lesson 1 What causes infectious diseases? n Microscopic organismspathogens n Parasites- organisms that live in or on another organism and derive nourishment from it

Forms of Pathogens- Bacteria n n n Bacteria- single-cell microorganism. Can live almost anywhere Some bacteria produce poisons. If a person is not immune- disease results Bacteria multiply at a rapid rate through cell division- every 20 minutes

Forms of Pathogens- Viruses n n Virus- smallest known type of infectious agent Not living cells Highly specific in the kinds of cells that they invade When a virus invades a cell it attaches itself to a cell- host cell

Viruses prey upon all living organisms, turning them into Virus Xerox machines

Forms of Pathogens. Rickettsias n n Resemble small bacteria Most are found in the intestinal tract of insects -notably fleas as well as in mice, ticks and mites Typhus and Rocky Mountain Spotted fever Passed on to humans by bites or by feces being deposited on the skin.

Forms of Pathogens. Protozoan n Single celled organisms that are larger than bacteria and have more complex cell structure. Most are harmless, but more than 30 types cause disease in humans. Disease-producing protozoan are most common in tropical areas that have poor sanitation.

Forms of Pathogens- Fungi n n n Simple organisms Sarophytes- feed off of dead animals, insects and leaves Prefer dark damp areas

Fungi The most common disease-causing fungi invade mainly deep tissues of the hair, nails, and skin. n Cause infections of the scalp or feet n Examples- athlete's feet and ringworm n

Athlete’s Feet

Ring worm

How infectious diseases are spread- People n n Direct Contact- uninfected person comes into physical contact with an infected person. STDs are spread this way. Human bite is another (dangerous) mode of transmission. A pregnant woman may also infect her unborn child Indirect Contact- Bacteria and viruses can enter the body through the lungs if droplets-exhaled, coughed or sneezed out by an infected personare inhaled. The common cold, influenza, and tuberculosis are spread this way.

n n How infectious diseases are spread. Animals Bite of dog or another animal can spread rabies Bloodsucking mosquitoes can pass on malaria and dengue fever

n n How infectious diseases are spread. Contaminated Objects Eating utensils Glasses/bottles Toothbrushes needles

Did You Know? n Your toothbrush should be discarded after a cold sore or sore throat.

How infectious diseases are spread- The Environment Food n Water n Soil n Air Some forms of infectious diseases are a direct result of human negligencecareless disposal of waste materials, pollution, handling of foods n

How Your Body Defends Against Infections n Immunity- body’s natural defense against infection

The Immune Response n n n Your body is exposed each day to pathogens Your body is constantly fighting pathogens that enter it Most of the time your body fights off an infection without you even knowing it because of your immune system.

Nonspecific Resistance n n Physical barriers- skin, mucous membranes and cilia Chemical barriers- tears, saliva, acid juices Body Cells- White blood cells (phagocytes) Inflammatory Response

Specific Resistance The general response of your nonspecific defenses is not always enough to protect your body from disease. n The adaptive immune system mounts specific attacks against particular types of pathogens. n When this happens another body defense goes to work in the form of cells called lymphocytes n

Lymphocytes n n Type of white blood cell that fight pathogens Travel through body in 2 networks -blood vessels and lymph vessels

2 types of lymphocytes B cells- when B cells encounter pathogens, they are stimulated to enlarge and multiply. They then turn into plasma cells which in turn produce antibodiesproteins that destroy or neutralize pathogens n Antibodies remember the pathogens and become active again when the same pathogens re-enter the body (memory Tcells and B-cells) n

2 types of lymphocytes n T-cells Killer T- cells- are stimulated to multiply by the presence of abnormal cells. They attach themselves to the cells and release toxins to destroy. n Helper T-cells- aid in the activity of B- cells and Killer T-cells n

Immune Response

n Lesson 2 Common Infectious Diseases Respiratory infections n Common cold- viral infection that causes inflammation of the mucous membranes lining the nose and throat. n Symptoms- stuffy runny nose, sneezing and sometimes sore throat and head ach. n Transmission -by breathing in a virus-containing droplets that have been sneezed or coughed out by an infected person- rubbing nose or eyes with fingers that have handled a contaminated object

Did You Know? n Water particles expelled through a sneeze can travel at speeds up to 100 miles an hour

Common Infectious Diseases n Respiratory infections n Influenza- viral infection of the respiratory tract n Symptoms include chills, fever, headache muscle ache and weakness n Transmission- virus infected droplets coughed or sneezed into the air n Treatment- rest, proper nutrition, drinking plenty of fluids

Common Infectious Diseases Respiratory infections n Tuberculosis (TB)- highly contagious bacterial infection that most often infects the lungs. Symptoms, coughing (sometimes with blood), chest pain, shortness of breath, fever, sweating, poor appetite and weight loss n Transmission- Air borne droplets n Treatment-antibiotics n

Common Infectious Diseases Respiratory infections n Strep Throat- bacterial infection of the throat n Symptoms- sore throat, fever, a general feeling of illness, and enlarged lymph nodes n Transmission- air borne droplets n Treatment- antibiotics

Infectious Diseases of the Nervous System n Encephalitisn Inflammation of the brain n Caused by a virus carried in mosquitoes n Starts off with a headache and fever- if left untreated it can progress to hallucinations, confusion, paralysis, and disturbances of speech, memory, behavior and eye movement

Infectious Diseases of the Nervous System n Meningitisinflammation of the meninges- the membranes that cover the brain and spinal cord n n Viral meningitis-mild caused by virus- no treatment Bacterial meningitisbacterial infection that can be life-threateningtreated with antibiotics.

Infectious Diseases of the Nervous System n Polio- disease of the central nervous system caused by a virus -Can lead to extensive paralysis including paralysis of the muscles used in breathing and can result in death

Vaccine n Vaccine- a preparation based on a weakened or dead pathogen that provides immunity by causing the body to produce antibodies to the pathogen.

Measles- highly contagious viral disease characterized by fever and rash that covers the entire body. n Rubella-German Measles n

Mononucleosis n n Mono- viral infection common among teenagers. “Kissing Disease”

Hepatitis n n Hepatitis A- results in eating foods or drinking water that has been contaminated with a virus from an infected person’s feces. Many cases occur among people who have traveled to areas where standards of hygiene are low. Hepatitis B- is found in all body fluids of an infected person especially blood. Spread through blood transfusions and blood products. Contaminated needles and sexual contact with infected person. More serious than hepatitis A. Can lead to chronic infection especially in the liver.

Hepatitis n Hepatitis C- is spread through infected blood. Can cause liver cancer.