Diseases caused by microorganisms

What are microbes/microorganisms? What are the diseases caused by microorganisms? How can we prevent diseases caused by microrganisms? What are vaccines? What are the different types of vaccines available for microbial diseases? Read further to know more.

The state of full physical, mental, and social well-being is referred to as being in good health. Being disease-free is only one aspect of being fit.

The term “disease” refers to a state of abnormal bodily functioning brought on by an infection, a poor diet, hereditary factors, environmental factors, or an undernourished brain.

Microrganisms/microbes can be the reason for a variety of diseases in humans. This article will discuss various diseases caused by microorganisms in detail.

Also read: Occupational Diseases

What are microbes/microorganisms?

Microorganisms or microbes are tiny living things that cannot be seen with the unaided eye. Because they can only be seen under a microscope, these are referred to as microbes. These can both be beneficial and detrimental. Pathogens are the dangerous ones.

They fall into one of five groups: bacteria, viruses, fungi, protozoa, and some types of algae. Microorganisms can be multicellular, like many algae and fungi, or single-celled, like bacteria, some algae, and protozoa.

They exist inside the bodies of animals, including humans, and can live in a variety of environments. While some can live independently, others must grow on other organisms to survive.

Diseases Caused By Microorganisms

• Infectious diseases can infiltrate the body and be brought on by a few dangerous microorganisms. They can contaminate food, leather, and textiles. They are to blame for illnesses like the flu, measles, chicken pox, TB, and others. Additionally, there is evidence from scientific studies that suggests microbes may be involved in several chronic, non-infectious diseases, including some types of cancer and coronary heart disease.
• Infections are the result of pathogen infiltration and growth inside a person. The condition is referred to as a disease when the infection negatively affects the person’s bodily processes. Microorganisms need to get into our bodies to create an infection.
• The portal of entry is the location where these penetrate the body. The skin, urogenital system, gastrointestinal tract, and respiratory tract can all serve as entry points.
• When an individual with common cold sneezes or coughs, hundreds of virus-laden droplets are released into the atmosphere. While breathing, these viruses can spread to a fit person’s body and infect them.
• A house fly is an illustration of an animal that acts as a pathogen carrier. Pathogens adhere to the bodies of the flies when they rest on the garbage and animal excrement. Following that, these flies come into touch with exposed food and spread the pathogens there, contaminating the food.
• A person may contract an illness if they consume contaminated food. The female Anopheles mosquito is another illustration of a transmitter. It transmits Plasmodium, the parasite that causes malaria. The dengue virus is also carried by the female Aedes insect.

Let’s examine the diseases brought on by various microorganisms:

Read: Brain-eating amoeba

Diseases caused by bacteria

• Prokaryotes, tiny one-celled organisms that thrive in a variety of habitats, are what bacteria are. They can exist in the bowels of humans, in the water, and inside the soil.
• They can be distinguished from one another based on their structure, the composition of their cell walls, and genetic variations. Binary fission is a mechanism used by bacteria to reproduce.
• Not all microbes are dangerous. Only a small minority of them can spread illness.
• A person becomes infected by bacteria when their body begins to produce poisons. Antibiotics can be used to eliminate these germs.
• The primary causes of bacterial infections are contaminated food and water. Most bacterial illnesses are contagious.

Diseases caused by fungi

• Fungi develop on the bodies in moist and humid areas.
• It is responsible for causing diseases such as ringworm and athlete’s foot.

Diseases caused by viruses

• Only the living cells of other animals can support the virus‘s tiny infectious agent replication. These are different and can only be spread by biological vectors. They can also affect plants, animals, and microorganisms.
• It consists of a capsid, a protein casing, and a DNA or RNA genome. Some viruses are protected by an interior or external membrane. Enzymes needed for the generation of energy are missing.
• They can only be seen under an artificial microscope because they are so tiny.
• If they infiltrate someone, they take over that person’s entire cellular structure. Using medicines won’t be able to kill viruses.
• Viral diseases are contagious and typically propagate through the air and direct contact.

Read: Chandipura virus

Diseases caused by protozoa

• The Protozoa are a diverse group of unicellular eukaryotic creatures that eat other organisms as well as bacteria as food.
• Protozoal diseases can be fatal and extremely risky.
• An illustration of a protozoa genus is an amoeba. It might result in amoebic diarrhoea. Malaria and sleeping sickness are both illnesses that are brought on by protozoa.

Zoonotic Microorganism Diseases

• Rudolf Virchow coined the term “zoonosis” (plural: zoonoses) in 1880 to refer to all diseases that affect both humans and creatures in nature.
• Zoonoses are those illnesses and infections that are naturally spread between vertebrate animals and people, according to a 1959 definition provided by the WHO.
• Zoonotic diseases are illnesses that can spread from wildlife to people. Zoonotic illnesses can be brought on by bacteria, fungi, viruses, and parasites.
• Examples: Chikungunya, Malaria, Yellow Fever, Zika Virus Disease, Dengue Fever, Ebola, Hepatitis E, Rabies, Japanese Encephalitis, Filariasis, Lyme disease, Babesiosis, Ehrlichiosis, Ringworm, Swine flu, also known as H1N1 virus – caused by type A influenza virus and West Nile virus – causes a viral infection that is typically spread by mosquitoes and can cause neurological disease as well as death.

Diseases caused by each of the above microbes are tabulated below for an easy read.

Also read: Fungal Diseases

Details of Diseases Caused By Microorganisms

Disease	Details
Diseases Caused By Microorganisms- Bacteria
Acne vulg anthrax (simply acne or pimples)	A skin disease caused when hair follicles become clogged with dead skin cells and oil from the skin. Causes == Genetics + Excess growth of the bacteria Propionibacterium acnes. Causative Agent: Propionibacterium acnes Mode Of Transmission: Direct contact/close contact Organism Affected: Humans/Adolescents
Anthrax	Causes skin infections and Gastrointestinal (GI) infection that are fatal. French scientist Louis Pasteur developed the first effective vaccine in 1881. Causative Agent: Bacillus anthraces Mode Of Transmission: Contact with infected meat Organism Affected: Most animals including humans
Cholera	Affects small intestine. The classic symptom is large amounts of watery diarrhoea that lasts a few days. Vomiting and muscle cramps may also occur. Diarrhoea can be so severe that it leads to hours of severe dehydration and electrolyte imbalance. Causative Agent: Vibrio cholerae Mode Of Transmission: Contaminated Water/food Organism Affected: Humans
Citrus Canker	The infection causes lesions on the leaves, stems, and fruit of citrus trees. Causative Agent: Xanthomonas axonopodis Mode Of Transmission: Air Organism Affected:  Citrus fruit plants
Diphtheria	Symptoms: sore throat and fever. The neck may swell in part due to large lymph nodes. Complications: myocarditis, inflammation of nerves, kidney problems, and bleeding problems due to low blood platelets. Myocarditis may result in an abnormal heart rate and inflammation of the nerves may result in paralysis. Causative Agent: Corynebacterium diphtheriae Mode Of Transmission: Air/direct contact Organism Affected: Humans
Pneumonia [caused by bacteria or viruses]	Pneumonia is an inflammatory condition of the lung affecting primarily the microscopic air sacs known as alveoli. Causative Agent: Streptococcus pneumoniae and Haemophilus influenzae Mode Of Transmission: Airborne droplets of sneeze Organism Affected:  Humans
Peptic ulcers	Ulcers in the lining of stomach or starting part of small intestine or lower part of esophagus. Causative Agent: Helicobacter pylori Mode Of Transmission: Organism Affected: Humans
Plague	Unhygienic conditions are the main cause. The symptoms of plague depend on the concentrated areas of infection in each person: bubonic plague in lymph nodes, septicemic plague in blood vessels, pneumonic plague in lungs. Causative Agent: Yersinia pestis Mode Of Transmission: Air/ direct contact Organism Affected: Humans
Tuberculosis	Tuberculosis generally affects the lungs, but can also affect other parts of the body. Most infections do not have symptoms, known as latent tuberculosis. About 10% of latent infections eventually progress to active disease which, if left untreated, kills about half of those infected. The classic symptoms of active TB are a chronic cough with blood-tinged sputum, fever, night sweats, and weight loss. Causative Agent: Mycobacterium tuberculosis Mode Of Transmission: Air Organism Affected: Humans
Typhoid	Often there is a gradual onset of a high fever over several days. Weakness, abdominal pain, constipation, and headaches also commonly occur. Causative Agent: Salmonella typhi Mode Of Transmission: Water Organism Affected: Humans
Diseases Caused By Microorganisms- Viruses
AIDS	Severely weakens immunity and makes way for several other pathogens. Causative Agent: Human Immunodeficiency Virus (HIV) Mode Of Transmission: Sexual contact, blood, needles, or from mother to infant Organism Affected: Humans and primates
Chicken Pox	Chickenpox, also known as varicella, is a highly contagious disease. The disease results in a characteristic skin rash that forms small, itchy blisters. Less severe than smallpox. Almost eradicated after the invention of vaccination. Causative Agent: varicella zoster virus (VZV) Mode Of Transmission: Air/Contact Organism Affected: Humans
Small Pox	One of the highly dreaded diseases that are highly contagious. Almost eradicated after the invention of vaccination. Causative Agent: Variola major and Variola minor Mode Of Transmission: Air/contact/water Organism Affected: Humans
Chikungunya	Causes severe joint pains. Animal reservoirs of the virus include monkeys, birds, cattle, and rodents. This is in contrast to dengue, for which primates are the only hosts Causative Agent: Chikungunya virus Mode Of Transmission: Aedes mosquitoes, such as A. aegypti and A. albopictus Organism Affected:  Humans
Cold, influenza (flu) and most coughs	Summer is hostile to the virus. Most common during winter months. Causative Agent: Rhinoviruses Mode Of Transmission: Airborne droplets of sneeze Organism Affected: Humans
Dengue fever	high fever, headache, vomiting, muscle and joint pains, and a characteristic skin rash. In a small proportion of cases, the disease develops into the life-threatening dengue hemorrhagic fever, resulting in bleeding, low levels of blood platelets and blood plasma leakage, dengue shock syndrome where dangerously low blood pressure occurs. Causative Agent: Flavivirus Mode Of Transmission: Female Aedes mosquito Organism Affected:  Humans
Ebola	Ebola infection shows a sudden onset of the disease resulting initially in flu-like symptoms: fever, chills and malaise. As the disease progresses, it results in multi-system involvements indicated by the person experiencing lethargy, nausea, vomiting, diarrhoea and headache. Causative Agent: Ebola virus Mode Of Transmission: Animal to man Organism Affected: Humans and Some Animals
Foot and Mouth Disease	A serious threat to animal farming in India. Causative Agent: Picornavirus [genus Aphthovirus] Mode Of Transmission: Close-contact animal-to-animal spread Organism Affected:  Animals
Hepatitis B	Affects the liver. Acute as well as chronic. Causative Agent: hepatitis B virus (HBV) Mode Of Transmission: Blood Exchange, STD [Sexually transmitted disease] Organism Affected: Humans
Measles	Complications occur in about 30% and may include diarrhoea, blindness, inflammation of the brain, and pneumonia among others. Causative Agent: measles virus Mode Of Transmission: Air Organism Affected: Humans
Polio or Poliomyelitis	Weak muscles lead to deformations. Causative Agent: Poliovirus Mode Of Transmission: Water/faecal-mouth Organism Affected: Humans
Zika	Most people with Zika virus infection do not develop symptoms; those who do typically have symptoms including rash, fever, conjunctivitis, muscle and joint pain, malaise and headache that last for 2–7 days. Zika virus infection during pregnancy can cause infants to be born with microcephaly and other congenital malformations as well as preterm birth and miscarriage. Zika virus infection is associated with Guillain-Barre syndrome, neuropathy and myelitis in adults and children. Causative Agent: Zika virus Mode Of Transmission: Aedes mosquitoes, such as A. aegypti and A. albopictus Organism Affected: Humans
Diseases Caused By Protozoans
Amoebiasis (amoebic dysentery)	Symptoms may include abdominal pain, mild diarrhoea, bloody diarrhoea or severe colitis with tissue death and perforation. This last complication may cause peritonitis. People affected may develop anaemia due to loss of blood. Causative Agent: Entamoeba histolytica Mode Of Transmission: Contaminated Water/food Organism Affected: Humans
Kala-Azar or Visceral leishmaniasis	This disease is the second-largest parasitic killer in the world (after malaria). The parasite migrates to the internal organs such as the liver, spleen (hence “visceral”), and bone marrow, and, if left untreated, will almost always result in the death of the host. Signs and symptoms include fever, weight loss, fatigue, anaemia, and substantial swelling of the liver and spleen. Causative Agent: Leishmania genus Mode Of Transmission: Sandflies Organism Affected: Humans
Malaria	Malaria causes symptoms that typically include fever, fatigue, vomiting, and headaches. In severe cases, it can cause yellow skin, seizures, coma, or death. Causative Agent: Different species of Plasmodium (P. vivax, P. malaria and P. falciparum) Mode Of Transmission: Female Anopheles mosquito Organism Affected: Humans
Sleeping Sickness	Initially, in the first stage of the disease, there are fevers, headaches, itchiness, and joint pains. This begins one to three weeks after the bite. Weeks to months later the second stage begins with confusion, poor coordination, numbness and trouble sleeping. Causative Agent: Trypanosoma Mode Of Transmission: Infected tsetse fly Organism Affected: Humans
Yellow Vein Mosaic of Okra [Ladies finger]	Okra is dwarfed, and malformed. Causative Agent: Bhendi yellow vein mosaic virus Mode Of Transmission: Insect Organism Affected: Okra plant
Diseases Caused By Fungi
Ringworms	The fungi that cause parasitic infection, collectively dermatophytes, feed on keratin, the material found in the outer layer of skin, hair, and nails. Causative Agent: Fungi belonging to the genera Micr Trichophyton and Epidermophyton Mode Of Transmission: Skin-skin contact Organism Affected: Humans
Rust of wheat	Wheat leaf rust is a fungal disease that affects wheat, barley and rye stems, leaves and grains. In temperate zones, it is destructive on winter wheat because of the pathogen. overwinters. Infections can lead to up to 20% yield loss exacerbated by dying leaves which fertilize the fungus. Causative Agent: Puccinia rust fungus Mode Of Transmission: Air/seeds Organism Affected: Wheat and other crops

Prevention Of Diseases Caused By Microorganisms

To address bacterial infections, medications like antibiotics and antibacterials are used. These prevent or slow down bacterial development. However, viral illnesses are not helped by these medications. Therefore, the best defence against illnesses brought on by microbes is prevention. The following measures can be taken to avoid the diseases:

• Isolate the infected patients and their belongings.
• Vaccination should be taken at a suitable time.
• Eat properly cooked food and drink boiled drinking water.
• Maintain personal hygiene and good sanitary habits.
• Keep the surroundings clean.
• Do not let water get collected in the surroundings to control the breeding of mosquitoes.
• Use mosquito nets and repellents.
• Use insecticide sprays.

Also read: Rare Diseases: Policy and Management

Vaccines for Diseases Caused by Microorganisms

• The vaccine is a biological treatment that boosts resistance to a specific illness.
• A vaccine frequently uses weakened or killed versions of the disease-causing microbe or its toxins and typically includes an agent that mimics the microbe that causes the disease.
• The agent prompts the immune system to identify the microorganism as foreign, eliminate it, and “remember” it so that it can more quickly identify and eliminate any subsequent interactions with these microorganisms.
• For various diseases brought on by microorganisms, various kinds of vaccines are accessible. It’s them,

Inactivated vaccines

• When inactivated vaccines are created, a chemical, typically formaldehyde, is used to fully kill the bacteria.
• The vaccine contains dead fragments of pathogen-causing microbes, typically bacteria.
• Since these vaccines contain dead antigens, their potency tends to wane over time, providing less long-lasting protection.
• Therefore, for the greatest protection, multiple doses of inactivated vaccines are typically required.
• The advantage of using inactivated vaccines is that there is no possibility of experiencing any symptoms associated with a disease; allergic reactions are possible but extremely uncommon.
• Examples of inactivated vaccines are hepatitis A, hepatitis B, poliovirus, hemophilic influenza type b, meningococcal, pneumococcal and the injected form of influenza.

Live-attenuated vaccines

• Live-attenuated is simply a synonym for weak but still alive.
• These vaccines are created when the virus is so weak that it can reproduce in the body only 20 times.
• When a vaccine is created, the virus or bacteria are weakened in a lab to the point where they can still reproduce and are living, but they can no longer cause severe disease.
• The mere fact that it exists is sufficient to trigger the immune system to create antibodies to fend off the specific disease in the future.
• They are usually favoured by healthy adults because they elicit longer-lasting immunological responses.
• Examples include the viral diseases yellow fever, measles, rubella, and mumps and the bacterial disease typhoid.

Recombinant Vector vaccine

• Immunity against illnesses with intricate infection processes can be developed by fusing the physiology of one microorganism with the DNA of another.
• There are presently four genetically modified vaccines on the market:
• A segment of the hepatitis B virus genome is inserted into the gene of a yeast cell to create hepatitis B vaccines. When the modified yeast cell multiplies, it releases only the purified hepatitis B surface antigen.
• The genes for a viral capsid protein are inserted into insect cell lines or yeast (like the hepatitis B vaccines) to create human papillomavirus vaccines. Particles that resemble viruses are created, and their production indicates a strong immunological reaction.
• Salmonella typhi bugs used in the live typhoid vaccine (Ty21a) have undergone genetic modification to render them non-pathogenic.
• Live attenuated influenza vaccine (LAIV) has been engineered to replicate effectively in the mucosa of the nasopharynx but not in the lungs.

DNA vaccination

• A novel vaccine known as DNA vaccination has recently been developed from the DNA of an infectious pathogen.
• Since the DNA quality of the infection varies in complex diseases, no vaccine is effective against it.
• DNA vaccines function by inserting and expressing DNA into human or animal cells, which causes the immune system to recognise the virus or bacterial DNA.
• Immune system cells that are aware of the proteins expressed will launch an assault against the cells expressing the proteins and the proteins themselves.

Polysaccharide vaccines

• The exterior capsule of some bacteria is made up of long chains of sugar molecules, and polysaccharide vaccines are a special kind of inactivated subunit vaccine made from these chains.
• There are pure polysaccharide immunisations for pneumococcal, meningococcal, and Salmonella typhi diseases.

Anti-Idiotypic Vaccine

• An antibody’s antigen-binding site (paratope) is a representation of a portion of the antigen’s three-dimensional structure (epitope).
• The idiotype, or particular arrangement of amino acids in the antibody, can be thought of as a reflection of the antigen’s epitope.
• Injecting the antibody into another mammal will cause the antibody to be raised against the idiotype.
  This anti-idiotype antibody imitates a portion of the antigen’s three-dimensional structure.
• This is an immunisation that can be used. Antibodies (anti-anti-idiotype antibodies) that recognise a structure comparable to a part of the virus are created when the anti-idiotype antibody is injected into a vaccine. These antibodies may be able to neutralise the virus.

Conclusion

The pathogenic microorganisms- bacteria, viruses, fungi, and protozoa trigger infectious illnesses. Typhoid, cholera, TB, and anthrax are all caused by bacteria. The common cold, measles, polio, hepatitis A, smallpox, covid-19, etc. are all caused by viruses. The fungi that cause ringworm, athlete’s foot, and malaria are different from the protozoa that cause malaria. To avoid diseases caused by microorganisms, good personal hygiene and a clean environment must be maintained.

The adage “prevention is better than treatment” is often used. Antibiotics and other medications are used to stop or slow the development of microorganisms. However, viral infections are not treatable with these medicines. The quantity and pace of microbial spread determine the depth or severity of an infection.

Read: Infectious Respiratory Particles

Previous year UPSC questions

Which of the following statements is/are correct? (UPSC IAS Preliminary Exam-2013)

1. Viruses lack enzymes necessary for the generation of energy.
2. Viruses can be cultured in any synthetic medium.
3. Viruses are transmitted from one organism to another by biological vectors only.

Select the correct answer using the codes given below.

A) 1 only

B) 2 and 3 only

C) 1 and 3 only

D) 1, 2 and 3

Answer: C