Various Routes of Disease Transmission

Very often we get a runny nose (common cold) usually during the cold seasons. Have you ever thought how do you get that? I am pretty sure that your answer is;  I was with my friends/ family members last time and after that etc. In fact, these are due to transmission of pathogen from your carrier friends to your healthy body. A pathogen is an agent that is a causative factor for a particular disease. Here is how one gets any pathogen of a disease various routes and obviously a communicable disease. The followings are some ways of disease transmission:

  1. Direct Transmission
  2. Indirect Contact
  3. Vector Borne Transmission
  4. Vertical Transmission

Direct transmission

Direct transmission takes place when the disease gets transmitted directly form an unhealthy body to a healthy one. The pathogen enters into the host body through open wounds, scratches or injuries mucous membranes, blood, saliva, biting of another animal, etc.  Examples: occupational diseases, coital diseases, bird sanctuaries etc.

Indirect contact

Indirect transmission occurs when the disease gets transmitted by indirect means. Examples are air borne, water borne, soil borne, aerosol route, etc. The most common is faeco-oral route where the pathogen enters the host due to consumption of contaminated food, water and other edible items. In case of animals the contaminated items also include the feed, fodder, mineral blocks or any other items the animal chew or lick. 

Mites are also another indirect means of disease transmission. These are inanimate objects such as clothes, bowls, buckets, brushes, and so on.

Vector Borne Transmission

This kind of transmission occur due to transfer of pathogen by a vector. Vector is an agent which is not the actual target of pathogen but it acts as a carrier of the same pathogen either mechanically or biologically. In biological transmission, the pathogen is present inside the body of host and the host’s body provides environment for replication of pathogen. The examples include, mosquito( acts as a vector for malaria/ dengue), fleas, ticks, mites. On the other hand, mechanical transmission occurs when the pathogen gets mechanically transmitted to the host’s body and there is not any life cycle relation between the pathogen and vector. The cholera pathogen transmitted by flies is an example of such sort.

Vertical transmission

In vertical transmission the pathogen transfer occurs from mother to child before and after birth. In such, transmission might occur across the placenta (trans placental route) before birth or during breast feeding (trans colossal route- colostrum is the mammary secretion frequently after birth for certain period and it has all the necessary nutrients for the new born baby) after birth. Some of the vertically transmitted diseases are AIDS, toxoplasmosis, hepatitis B, etc. Transmission can occur through placenta, milk during breast feeding, blood and other body fluids during birth.

Disease Process

Our environment has numerous disease causing pathogens. When a pathogen enters inside host body, the immune system of host recognizes it as foreign (antigen) and starts producing antibody (or call the killer cells) against the pathogen to destroy it. If the body is successful to destroy the pathogen, then the body escapes disease. There will be the less chance of same infection time and again in future due to generation of memory cells. But disease symptoms can be observed if pathogens escape immunity. In this case the pathogen does it’s work like replication and destroy the cells and tissues of host.

The symptoms like fever and lesions are the results of such activities. Fever is actually programme of host body itself occur due to production of different chemical mediaters. Lesions are detectable abnormal changes or damage to normal cells and tissues of host due to unfavorable activities of pathogen inside host body say for example toxins released by pathogen.

For further information regarding this topic you can also study it here.

You can also read about a communicable disease bacterial pneumonia for further information. Click Here!!

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