How diseases are transmitted?

Spread of diseases

Q. (a) How diseases are transmitted?

(b) Give the difference between these words;

(i) infection and (ii) Disease.

(c)Describe briefly how you can control or prevent infection.

ANSWER;

(a) Diseases are transmitted when pathogens move from one host to another either directly or indirectly.

Directly is when pathogens move from one organism to another whereas indirectly involves passing of pathogens to another organism by an intermediate host.

All these passages are shown by the following ways;

(i) Eating and drinking; food and water contaminated with feces of infected people.

Good examples of diseases transmitted through these means are such as cholera, typhoid fever, amoebic dysentery.

If the disease is transmitted through drinking contaminated water is called water-borne disease. And it is called food-borne disease if it is spread through eating of contaminated food.

(ii) Air; It is possible if a healthy person has breathed in the liquid droplets that are released from the body of an infected person by the way of coughs or sneezes.

Examples of these diseases are such as flu, common cold, pneumonia, tuberculosis, whooping coughs and diphtheria.

The diseases which are transmitted through this way are called air-borne diseases.

(iii) Insect vectors; vectors carry germs within their body and therefore they can transmit diseases during the act of sucking blood or biting.

The diseases which are transmitted through this way are called Vector-borne diseases and they include malaria and yellow fever which are transmitted or spread through mosquito bite. Another disease is bubonic plague which is spread through rat bite and fleas. Also, there is sleeping sickness which is spread through tsetse (fly bite).

(iv) Physical contact; There are two ways in this aspect namely (i) contact with the skin of an infected person (ii) sexual contact.

Apart from these, transmission is also possible by such means as sharing of clothes, towels and combs with infected people.

The diseases which are spread by these ways are called contagious diseases and include skin diseases like ringworm, dermatitis, impetigo etc.

As for sexual contact, the diseases are called *v*enereal diseases or sexually transmitted diseases; examples of such diseases are **gonorrhea, syphilis, genital herpes and HIV/AIDS.

(v) Pets bite; this is possible through bite by an infected domesticated animal like dog, and cat.

Good example of disease which is transmitted through this way is rabies. Infected dog (rabid dog) is the most common transmitter of rabies.

(b) The difference between infection and disease is that *Infection* *is a disease caused by bacteria, fungi, protozoa or virus while Disease ***is an illness or state of unhealthy condition which can be caused by any one of these or combination of them;

(i) Infection,

(ii) Genetic abnormalities,

(iii) Hormonal disturbances,

(iv) Nutritional factors and

(v) Chemical and physical factors.

(c) Prevention or control of infection can be undertaken as follows;

(i) Preservation of food; As most of uncooked food contain bacteria, the technique of food preservation has been developed so as to prevent these bacteria from developing (reproducing and growing). It involves destruction or inhibition of the bacteria growth whose activities would cause the food to decay.

It also serves to kill some disease bacteria e.g. vibrio, typhoid which could be transmitted by food.

Preservation of food includes such processes as;

(a) Refrigeration which prevent multiplication of bacteria ( NB. it only prevent reproduction of bacteria but not kill them).

(b) Cooking with high temperature which kill most bacteria and their spores if cooked for a long time.

(c)Bottling and canning which kill bacteria by the high temperature used and also prevent their access to the food by sealing it in a vacuum.

(ii) Drinking of clean and safety water; This is made possible through such processes as;

(a) Boiling which kills most of microorganisms.

(b) Proper disposal of human sewage in such a way that it cannot contaminate water supplies (i.e. by primary, secondary or tertiary sewage treatment).

(c) Water treatment that removes or destroys any harmful microbe which may be present in water.

(iii) Adequate ventilation; this reduces the chances of getting air-borne diseases such as pneumonia, tuberculosis whooping cough, diphtheria etc. If houses are adequately ventilated, the exchange of air within and that from outside will be fresh thus remove the suspended bacterial droplets and viruses before they reach harmful proportions to affect human.

(iv) Avoid physical contact; people should avoid contact with contagious disease (communicable) suffering people.

They should also not share or touch their clothing, bed sheets, towels and their washing materials as well.

In case of venereal diseases such as syphilis and gonorrhea, people are urged to stop prostitutions and if one is sick, an early treatment from a qualified person should be done.

(v) Control of insect vectors; all flies which may carry disease bacteria on their bodies e.g. in the legs, abdomen or proboscis should strictly be prevented from walking on food for human consumption. More so in food which is to be eaten in raw condition and without further cooking. Houseflies and mosquitoes are therefore must be well controlled as they are commonly found in our homes.

(vi) Personal hygiene; this includes such activities as;

(a) Frequent bathing, washing and change of clothes,

(b) Regular washing of hands after visiting toilets and before handling food so that intestinal bacteria cannot be taken in with the food and

(c) cleaning of plates, cups, cooking utensils and cutlery in order to avoid disease bacteria from contaminating the foods.

(vii) Isolation; people infected with diseases such as contagious and air-borne diseases should be isolated from healthy people.

This helps to prevent transmission of infections from one person to another. Good examples of such diseases are cholera, skin diseases (ringworm, impetigo etc.) tuberculosis, diphtheria, meningitis etc.

(viii) Antiseptics and antibiotics; antiseptic chemicals are present in disinfectants which can be used to kill bacteria and their spores or kill bacteria only or just prevent multiplication of bacteria.

Disinfectants can be used on the floors, walls and equipment in houses and buildings of food processing industries, hospitals where high standards of hygiene are necessary. It can also be applied in wash-basins, drains and lavatories.

Antibiotics can be used to destroy many forms of harmful bacteria. It can be applied internally against infection of the body tissues by killing the bacteria without harming the cells of the body. For example, an antibiotic like chloramphenicol is used to control infection of the intestine.

(ix) Immunization and vaccination; in this case people are deliberately infected with a mild form of disease which later stimulate antibody production in the blood. The production of antibodies will protect a person against future infections.

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