Diseases are caused by pathogenic microorganisms and infectious particles. Disease transmission occurs through vectors and carriers. Carrier is an individual which has the disease, but not symptoms; it is capable of transmitting the disease to a new individual. Vector is an organism which is capable of transmitting disease from infected individual to new individual without having the disease. This is the key difference between carrier and vector. Both carrier and vector are responsible for disease occurrence and spreading between organisms.
CONTENTS
1. Overview and Key Difference
2. What is a Carrier
3. What is a Vector
4. Side by Side Comparison – Carrier vs Vector
5. Summary
What is a Carrier?
Carrier is an organism which is capable of disseminating the disease to another susceptible organism. Carrier does not show any signs and symptoms of the disease. But the carrier is a diseased organism or an infected individual possessing the potential disease causative agents inside the body. Hence they are capable of transmitting the disease to the next generation. There are main three types of carriers:
- true carrier,
- incubatory carrier
- convalescent carrier
Diseased individuals can become carriers even after the cure of the disease. For example, typhoid fever can be again spread through feces and urine of cured people who are carriers.
AIDS is a disease caused by HIV (human immunodeficiency virus). There are HIV carriers – individuals do not show AIDS symptoms. However, they are HIV-positive carriers.
Figure 01: Carrier of cystic fibrosis
What is a Vector?
Vector is an organism capable of transmitting a disease from an infected individual to a new individual. The special feature of a vector organism is its capability for passing the disease causative agent from one organism to the second organism without contracting the disease. It acts as a medium for the disease agent to spread and survive in a new organism. Disease transmission via vectors happens in two main ways namely mechanical and biological transmission. During the mechanical transmission, vector acts as a vehicle and transports the disease agent without permitting it to pass important stages of its life cycle such as development or multiplication inside the vector organism. Infectious agents develop and multiply inside the vector during the biological transmission.
There are different types of vectors. Many of the human and animal disease vectors are blood sucking insects. Mosquitoes are best-known vectors involved in disease transmission. Other types of arthropods vectors include ticks, fleas, flies, sandflies, bugs, mites, etc.
Some plants and fungi act as vectors for various diseases. For example, the big-vein disease of lettuce is caused by a viral particle and zoospores of fungi facilitate the transmission of the disease by acting as vectors. Many of the plant viral diseases are transmitted by fungal vectors, especially fungi belonging to Chytridiomycota. Weeds and parasitic twines also behave as vectors in transmission of plant viral diseases.
Figure 02: The vector of dengue fever
What is the difference between Carrier and Vector?
Carrier vs Vector |
|
| Carrier is an infected organism capable of transmitting disease to another organism without showing the clinical signs of the disease. | Vector is an organism which transports the disease causative agent form infected person to healthy person |
| Disease | |
| Carrier has the disease. | Vectors is a disease-free organism |
| Examples | |
| Examples include HIV carriers. | Examples include mosquito, mites, fungi, plants. |
Summary – Carrier vs Vector
Carrier and vector are two types of organisms involved in disease transmission. Carrier transmits the disease without showing the disease symptoms. However carrier contains the disease agents inside. Vector is an organism that transmits the disease but does not become sick. It acts as a vehicle to transport the disease agents from infected to new organism. This is the difference between carrier and vector.
References:
1.Brachman, Philip S. “Epidemiology.” Medical Microbiology. 4th edition. U.S. National Library of Medicine, 01 Jan. 1996. Web. 11 Apr. 2017
2.Leitner, Wolfgang W., Tonu Wali, Randall Kincaid, and Adriana Costero-Saint Denis. “Arthropod Vectors and Disease Transmission: Translational Aspects.”PLoS Neglected Tropical Diseases. Public Library of Science, Nov. 2015. Web. 11 Apr. 2017
3.Connell, W. T. “HUMAN CARRIERS OF DISEASE.” Canadian Medical Association Journal. U.S. National Library of Medicine, Apr. 1911. Web. 11 Apr. 2017.
Image Courtesy:
1. “Autorecessive” By en:User:Cburnett – Own work in Inkscape (CC BY-SA 3.0) via Commons Wikimedia
2. “Aedes aegypti biting human” By Original author: US Department of Agriculture; Picture from the USDA website at (Public Domain) via Commons Wikimedia