Infectious diseases are caused by small microbes invisible to the eye.
They are called infectious because they can easily spread from one person or animal to other.
The microbes causing these include bacteria, protozoans, fungi, yeast and virus. Of them bacteria and protozoans are the most common disease causing agents.
Bacteria cause disease both in plants and animals.
While protozoans cause disease only in animals and humans.
They are widely rampant and very frequent in causing disease among the public.
Some of them infect seasonally especially during rainy season, winters etc.
While others infect regularly due to contamination and spread from one person to another.
Few of them spread as epidemics and are a threat to human population. Plague, cholera, small pox were epidemics which wiped of few cities. The countries population drastically declined due to plague epidemic for centuries in the past.
Diseases caused by bacteria;
Bacteria causes wide set of diseases by deranging the host physiology.
Most of the diseases caused by bacteria are life threatening and also damaging to the affected organ.
Once infected the common symptoms like fever, weakness are observed by the host. If not treated in time, the infection can be fatal.
But the modern medicine has drugs in the form of antibiotics for effective treatment of bacterial diseases
List of diseases caused by bacteria in humans include:
Face– Acne or pimples are caused by Propionibacterium acnes.
Ear: Otitis is an ear infection which caused by pneumococcus, Haemophilus influenzae, and Moraxella catarrhalis.
Eyes: Conjunctivitis is an eye infection leading to soreness of eyes. Caused by Chlamydia trachomatis and Neisseria like bacteria.
Brain: Meningitis is an infection of brain meninges (covering layers). It is caused by Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae etc.
Throat: Diphtheria caused by Corynebacterium diphtheriae.
Lungs: Pneumonia by streptococus pneumoniae, tuberculosis (TB) by mycobacterium tuberculosis.
Heart: Endocarditis- an inflammation of lining of heart caused by Staphylococcus aureus, streptococci and pseudomonas species.
Stomach: Gastric Ulcer. is caused by hyper acid secretion besides helicbacter pyrolli.
Intestine: Dysentery, cholera (loose motions with pain) etc. Cholera is caused by vibrio cholera. Dysentery is caused by Shigella and Enteroinvasive Escherichia coli.
Urinary tract: Nephritis, prostatitis is inflammation of nephrons and prostate gland respectively. Caused by
Sex organs: Syphilis is caused by Treponema pelladium bacteria, gonorrhea by Neisseria gonorrhea. Both are sexually transmitted diseases.
Blood: Typhoid infection is caused by Clostridium typhii, tetanus by streptococcus tetani, plague by Yersinia pestis etc.
Skin: leprosy is caused by mycobacterium leprae & Mycobacterium lepromatosis.
List of diseases caused by bacteria in Plants include:
Blight of paddy, citrus canker, angular leaf spot in cotton, Tumors in plants, rot in vegetables etc.
Diseases caused by protozoa;
Protozoa are microbes which are single celled organisms. They cause wide variety of diseases and their pathogencity is relatively less severe than bacteria.
Mouth: Gingivitis infection of gums caused by entamoeba gingivalis. It spreads by kiss.
Brain: Amoebic Encephalitis. This is rare and spreads from intestine to liver to brain by entamoeba. Other type is caused by Naegleria fowleri which one experiences after exposure natural water bodies.
Intestine: Amoebic Dysentery with loose motions, pain and frequent urge for bowels. By Entamoeba hystolitica.
Blood: Malaria caused by plasmodium species (P.malaria, P. falciparum etc.),
Some other infections include
Giardiasis an intestinal infection caused by Giardia lamblia. Causes weakness, diarrhea.
Trichomoniasis with symptoms like vaginitis, blood in urine etc. It is also a sexually transmitted disease caused by Trichomonas vaginalis.
Toxoplasmosis spreads form cats to humans.. causing encephalitis. It is fatal if untreated. It is caused by Toxoplasma gondii.
Trypanosomiasis which causes sleeping sickness, fever etc. which can infect brain, lymph, heart, spleen etc. It is fatal infection unless well treated. It is caused by Trypanosoma brucei, Trypanosoma cruzi.
Antibiotics are used in the treatment of bacterial diseases. But many of them are difficult to treat due to resistance emerging in the bacteria. So the best way is to prevent infections.
Also we might find that microbes are only harmful to us. But there are many bacteria which are helpful to us.