DISEASE CONTROL

ENV 550

Lesson 2 – Classification of Disease

MOHD IZWAN MASNGUTENVIRONMENTAL HEALTH PROGRAM

Basic Principles of Communicable Diseases

Classification Of Diseases

• Grouping of diseases based on certain characteristics.

• Easier to understand and remember• Characterized by having same mode of

transmission .

Classification Into 10 Group1. Water-washed diseases2. Fecal-oral diseases3. Food-Borne diseases4. Diseases of soil contact5. Disease of water contact6. Skins infection7. Respiratory disease and other airborne-transmitted

infection8. Disease transmitted via body fluids9. Insect-borne disease10. Zoonoses

i. Ectoparasites zoonosesii. Domestic and synanthropic zoonoses

1. Water Washed Diseases

Simplest transmission – person to person Relate to poor hygiene – arise from direct contact

of the skin, conjunctiva or mucous membrane Alternatively, organisms from skin or in

conjunctival secretions can be transported by intermediate vehicle.

Two group under this category: Skin disease Eye disease

Skin disease Include infection of scabies , lice and superficial fungal. Tropical ulcer also included here

Eye disease Include trachoma, epidemic hemorrhagic conjunctivitis,

etc.

Main control method for water washed disease is to increase water quality.

This include providing an adeuqate volume of water for washing to encourage personal hygiene.

2. Fecal-oral Disease Transmitted by person-person contact, through water

or food of directly into the mouth. Main reason of occurrence were due to absence of a

proper water supply, with rubbish and dirty surrounding,

Associate with abundance number of flies (typically occurred when disease strive)

Breaking the fecal oral cycle is the basis of control. This are achieve by :

Personal hygiene Increase water quality Food hygiene Provision of sanitation

Many of the disease in this group cause diarrhea

Example of disease under this group: Gastroenteritis Cholera Typhoid Bacillary Dysentry ( Shigellosis) Giardia Paratyhoid Hepatitis A & E Poliomyelitis Enterobius

3. Food Borne Disease Related to disease which only transferred by

food. Can infect food in general – food poisoning or

sometimes be very specific in the particular food – helminth.

Method of control focused on: Food hygiene Proper cooking of food ( right temperature, etc) Sanitary methods to prevent cross contamination

Example of disease ; Food poisoning due to bacteria; Staphylococcus spp,

Bacillus cereus, salmonella spp. Food poisoning due to fish poisoning; Ciguatera,

Scromboid, etc Food poisoning due to plant poison (organic or

inorganic) Campylobacter enteritis Fluke ( intestinal, fish, liver, lung) Tapeworm ( Fish, swine, Bovine) Trichinosis

4. Disease Of Soil Contact Soil can be source of infection. Particularly due to nematodes and bacterial

infection. Transmission can be direct from:

Soil contamination Swallowing nematodes eggs, Larvae penetrate skins in contact with

Developmental stages often take place in the soil – human – soil.

• Control of infection via:– Promotion of personal hygiene – preventing contamination of soil – Vaccination (tetanus)

• In the case of nematode infection (trichuris, Ascaris, hookworm), these always come in together.

• This indicates that if she/he is infected with one, likely to have all three.

• Most common in developing country e.g Africa and South America, Asia

• Example of disease:– Trichuris– Ascaris– Tetanus

5. Disease Of Water Contact Important medium for disease transmission Normally through;

Water polluted by fecal matter Polluted water being used to wash food or food

medium Also serve as medium for fish – carry parasitic

stage that is transmitted when being consume. Minimize contact with water is the best

method of control.

• Example of disease:– Schistosomiasis– Guinea worm– Buruli Ulcer

6. Skins Infection

• Skin is common site for several communicable disease

• Present with rashes of various kind• Infection often transmitted from person-to-

person via skin contact or airborne route• Control done by:– Avoidance of contact with infected individual– Vaccination (if available)

• Example of disease:– Scabies, fleas, lice– Chickenpox/shingles– Measles– Rubella– Mumps– Streptococcal skins infection– Leprosy

7. Respiratory Disease And Other Airborne-transmitted Infection• Our vulnerable respiratory apparatus is easily

invaded by microorganism• This due to our continuously breathing activity• The common site of entry is nasopharynx• Our ciliated lining and mucus secreting cells of

respiratory tract can act as non-specific host defense mechanism, entrapping microorganisms and passing them to exterior.

In attempting to expel this secretions by coughing or spitting, organisms may be transferred to another host.

Respiratory infection are usually transmitted by direct contact between individuals

Very effective if closer to contact. Control is mostly non-specific since human

contact is difficult to be avoid due to daily activity.

*respiratory is enigma, yet only some individuals manifest disease.

This is due to the factor infective dose and host response which determine the infection.

• Environmental factor can:– Increase the infective (overcrowding)– Reduce host resistance (malnutrition)

Examples of disease; Tuberculosis Acute Respiratory Infection (ARI) Influenza Whooping cough Diphteria Meningococcal meningitis Pneumonia Otitis Acute Rheumatic Fever

8. Disease Transmitted Via Body Fluids

Includes infections transmitted from one human to another by physiological fluids of the body – blood, saliva, seminal fluid

Transmission normally direct via sexually or non sexually contact

The main cause: Close personal contact Intimate/sexual intercourse

Considered as social disease, determine by habit and people’s attitude

Example of disease: Human Immunodeficiency Virus Hepatitis B & C Yaws Endemic syphilis Venereal syphilis Gonorrhea Chlamydia Ebola Hemorrhagic Fever Trichomonas Genital herpes Human Papilloma

9. Insect-borne Disease

• Vector transmission is one of the commonest methods of spreading disease.

• Divided into two chapter:– Flight insect– ectoparasites

Mosquito-borne disease: Most important due to its abundant, close proximity

to human and blood meal. Some parasites are specific for certain type of

mosquito e.g malaria & anophelines. Others e.g arboviruses are less selective and utilize

many different species. Parasite development within mosquito are:

Morphological without multiplication Asexual reproduction (arbovirus) Sexual reproduction (malaria)

Arboviruses Grouped into three symptom-complexes:

1. Those producing mainly fever and/or Arthritis – e.g chikungunya, Onyong-nyong, west nile.

2. Those presenting as fever and encephilitis – japanese encephilitis, Murray Valley etc.

3. Hemorrhagic fevers – Yellow fever, dengue, rift valley, etc

• Example of disease– Japanese encephalitis– Dengue– Yellow fever– Malaria– Lymphatic filariasis– African Trypanosomiaosis (Sleeping sickness)

10. Zoonoses

• Infection that is naturally transmitted between vertebrae animals and humans

10.1.1 Ectoparasite Zoonoses

• Disease caused by non-flying vectors e.g fleas, lice

• Responsible for important group of infections that are often associated with animal (reservoir)

• Human are often the accidental victims of these zoonotic infections

• Example of disease:– Plague– Typhus– Louse borne relapsing fever– Tick borne relapsing fever– Lyme disease

10.1.2 Domestic And Synanthropic Zoonoses Zoonoses disease which does not involve vector

(direct from animal to human) Most of infection are due to close association

between human and domestic animals (domestic)

Zoonoses from unwelcome animal e.g rats are called synantrophic.

Link to animals which depend on human for food and companions e.g cat, dogs, cow and other.

Control depends upon an understanding of the contact with the animal

Example of disease Rabies Leptospirosis Hydatid disease Toxocariasis Toxoplasmosis Brucellosis Anthrax Lassa fever

Transmission cycle

1. Direct infection

2. Intermediate host – Human Reservoir

3. Intermediate host – Human reservoir

4. Animal-human reservoir

5. Vector human reservoir

6. Animal reservoir

Human

7. Vector-Human Reservoir

Human

8. Vector-animal reservoir to vector-human reservoir

References

Roger W. Communicable disease epidemiology and control; 3rd edition.2009. Cambridge University Press, Cambridge. United Kingdom

David L. H.,. Control of Communicable Disease Manual. 18th edition.2004. America Public Health Association. United Book Press Inc. Baltimore. USa