Common Pathogens

Pathogens are those microbial agents that cause infections or diseases.Pathogens can be referred to as those microbes which are capable of causing disease in living organisms. They can grow in both intracellular as well as extracellular compartments of the body and reproduce or complete their life cycle. They can also be called infectious agents.They can spread through various means like air borne through respiratory pathways, oral route, contact through skin, body fluids, contaminated food and water, unhygienic living,etc. Most of them cannot be seen with the naked eyes, only can be seen with the help of microscopes. Example-Bacteria, Viruses, Fungi, etc.

Types of Pathogens

1. Bacteria

Bacteria are single-celled and are diverse in shape and feature.They enter into the human body and release certain toxins/ chemicals that are harmful to the human body.The toxins can cause harm to organs and tissues and hence the disease can be caused.

Not all bacteria are harmful to the body, some of them are present in the body and support normal living. They are usually present in the intestine, urethra, vagina,etc.

Antibodies are used to treat bacterial diseases.

1. Virus

Viruses are smaller than bacteria and have a high transmission rate. Viruses are much more contagious than any other pathogens. The nucleic acid of viruses is highly prone to mutations that is why they can mutate at a very faster rate. Viruses enter/invade into the human body and replicate inside the body. Human organ system acts as a host to the virus. The virus can enter via various routes,such as-

• Respiratory route
• Body fluid of an infected person
• Sexual route
• Blood transfusion,etc

1. Fungi

Many species of fungi are responsible for causing diseases in human.Most of them are the skin diseases that fungi cause,example-ringworm. Fungal diseases are contagious and can spread from person-to-person via contact. Fungus usually grow in hot and humid environments.

1. Parasites

Parasites spread through soil,blood transfusion, contaminated food and water,etc. Various types of parasites are responsible for causing diseases like-

• Protozoans- They are highly parasitic in nature and can require more than one host. 
• Roundworms- They usually live inside intestines and lymphoid organs.
• Flatworms- they are also known as tapeworms and usually live in intestines.

Diseases Caused By Pathogens

1. Bacterial Diseases

Some of the bacterial diseases are: 

1. Typhoid- caused by Salmonella Typhi. Mode of transmission is-It enters the small intestine through food & water  and migrates to other organs via blood. Symptoms are sustained high fever (39o-40o C), stomach pain, weakness, headache, constipation and loss of appetite. Intestinal perforation and death may occur. Widal test is used for confirmation of the disease.
2. Tuberculosis – causative agent is Mycobacterium tuberculosis and is contagious disease.
3. Pneumonia- Streptococcus pneumoniae or Haemophilus influenzae are the pathogens. It infects the alveoli of the lungs. The fluid fills the alveoli, causing breathing issues. Inhaling the droplets/aerosols emitted by an infected person is the mode of transmission or by sharing glasses and utensils with someone who has been infected. Symptoms include  fever, coughing and headache. Lips and fingernails turn grey to bluish in extreme cases.

1. Viral Diseases

1. Common cold- caused by Rhinovirus. It infects the nose & respiratory passage but not lungs. Mode of transmission of Rhinovirus is by  Inhaling droplets resulting from cough or sneezes , through contaminated objects. Symptoms are nasal congestion & discharge, sore throat, cough, hoarseness, headache, tiredness etc.The infection usually  lasts for 3-7 days.
2. AIDS (Acquired immunodeficiency Syndrome)- causative agent is HIV(Human immunodeficiency virus). The mode of transmission is mainly through sexual route, through transfusion of body fluids, sharing needles, from mother to child during pregnancy, breastfeeding. The virus weakens the host’s immune system. Symptoms usually start occuring after several years of infection. The diagnostic test for AIDS is ELISA (Enzyme Linked Immunosorbent Assay).

1. Fungal Diseases

1.  Ring worms: Pathogens are Microsporum, Trichophyton & Epidermophyton. They are seen in the groin, between toes etc. Mode of transmission: From soil or by using towels, cloths, comb etc. 

1. Protozoan Diseases

1. Malaria: causative agents are species of Plasmodium (P. vivax, P.malariae & P. falciparum).  Most serious (malignant) malaria is caused by P.falciparum. Mode of transmission is by female Anopheles mosquito. Hemozoin (toxin released by Plasmodium) causes chill and high  fever recurring every 3-4 days.
2. Amoebiasis (Amoebic dysentery): Pathogen is Entamoeba histolytica. Mode of transmission: Houseflies (mechanical carriers)  transmit parasites from faeces to food & water. Symptoms: Constipation, abdominal pain and cramps, stools with excess mucus and blood clots.

1. Helminth Diseases

1. Ascariasis: Pathogen is Ascaris(Intestinalparasite). Mode of transmission: Soil, water, vegetables, fruits etc. contaminated with faeces containing eggs of parasites. Symptoms: Internal bleeding, muscular pain, fever, anaemia and 

 blockage of intestinal passage.

1.  Filariasis (Elephantiasis): Pathogen is Filarial worm or Wuchereria  (W. bancrofti & W.malayi).  Mode of transmission: Bite of female Culex Mosquito. Symptoms: Filarial worms live in lymphatic vessels (usually of lower limbs). It causes chronic inflammation of the organs in which they live for many years. Limbs and genital organs may be deformed.

How to prevent diseases caused by pathogens

For some pathogens, our immune system is capable of fighting. Immune system acts as a defence system to our body. Barriers of the human system, antibodies along with various lymphoid tissue/organs are responsible for providing shields to the body. However, some pathogens may cross these barriers and can cause diseases. By adopting preventive measures, we can reduce their spread and contamination,like 

• eating a healthy and balanced diet.
• Drinking adequate amounts of water.
• maintaining personal hygiene
• Not coming into contact with diseased person
• Not sharing personal items- razor,soap,toothbrushes
• Protection against insect bite
• Vaccination against fatal diseases
• Routine check-ups

Conclusion

A huge diversity of pathogens are present around us like- bacteria, viruses, fungi, protozoans, worms,etc. They have the capability to make us ill, if we are healthy our body can protect us from pathogens. It is necessary to lead a healthy life. Severe diseases can be treated by various treatment procedures. However, for some diseases only symptomatic treatment is possible.