Disease Causative Agents

The diseases caused by microbes are generally transmitted quickly when microbes are transferred from the diseased to the healthy person and hence, they are termed “infectious” diseases, for e.g. common cold, skin infections, etc. 

 A disease transmitted by sexual contact is AIDS.

The immune system works against disease-causing microbes and prevents diseases. The nervous system transmits impulses, the muscular system helps in the movement of the body and the respiratory system helps in the exchange of gases.

SARS is caused by bacteria (i.e. 1 is correct), AIDS is caused by Human Immunodeficiency Virus (HIV) (i.e. 2 is correct) and common cold is caused by different kinds of viruses (i.e. 4 is also correct). (1), (2) and (4) are correctly matched, but (3) is incorrect because malaria is caused by a protozoan, i.e. Plasmodium is transmitted by the vector, i.e. female anopheles mosquitoes.

Animal (dog and cat usually) bite causes rabies due to transmission of rabies virus. Typhoid and tetanus are caused due to bacteria transmitted by food, water, soil, etc while AIDS is caused by virus transmitted by exchange of body fluids between a healthy person and an infected person.

Excessive dehydration, due to loose motions and vomiting are symptoms of diarrhoea which is a disorder of gastrointestinal tract. Thus, (4) is the correct answer. Malaria is caused due to infection of plasmodium in blood and its effect on liver. Tuberculosis is an ailment of lungs and tetanus is a disorder affecting the muscular system.

In elephantiasis, the person’s limbs, i.e. feet, legs, arms and hands are highly swollen due to accumulation of water in the cells. The person looks bulky and his limbs are swollen. It is compared to elephant’s limbs so the disease is termed “elephantiasis”. In ascariasis, the worm named ascaris infects the stomach and intestine, thereby making the person weak because they feed on the food material present in the blood of the person (host). Similarly, tuberculosis is caused due to bacteria and in this disease, lungs and respiratory systems are affected. In this, mucus begins to collect in lungs gradually leading to inefficient gaseous exchange, frequent cough and at later stages, bleeding occurs in the throat. Thus elephantiasis, ascariasis and tuberculosis are caused due to infectious agents and they take a long time inside our body as they are treated slowly. They leave behind long term health effects which make the body weak. Thus, they are chronic. But influenza, i.e. common cold lasts for few days. It affects us severely, but it does not make us weak later on. Hence, it is an acute disease.

Yes, it is correct. Small and curved bacteria are found in the area infected by peptic ulcer.

Yes, it is a direct mode of transmission. The rabies virus is injected into the human body by the bite of a rabid dog.

Yes, it is the correct answer. Chickenpox is caused by a virus called Varicella Zoster. A person with chicken pox is the most contagious during the first 2 to 5 days of being sick.

No, it is not a viral disease. Acne is a bacterial infection.

Yes, it is the indirect mode of transmission, which spreads through intermediate agents. Here food and water act as intermediate agents.

Gonorrhoea, syphilis, genital herpes, chlamydiasis, genital warts, trichomoniasis and hepatitis-B are STDs.