Introduction to Environmental Health

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Chronic & Communicable Diseases

Objectives




 



Discuss & give examples of chronic diseases. Define communicable diseases & explain their significance. Discuss disease transmission. Explain how communicable disease is transmitted by: a. intestinal discharges. b. nose & throat discharges. c. zoonoses (animals) Discuss the disease spread by vectors and their control measures.

Environmental Impacts Paradigm: Exposure-Response
(EIA : EHIA)



Exposure - def: any condition which provides an opportunity for an external environmental agent to enter the body.

Vectors of exposure



Agent
- def: any chemical, biological, or physical material capable of eliciting a biological response. - different than the vector carrier (air, soil, water, food).



Dose - Def: the amount of agent actually deposited within
the body. - Typically, the distinction between exposure & dose is blurred, although in reality, significantly difference doses can result from the same exposure.



Response
- Def: The biological response to an agent.

Environmental Impacts Paradigm: Exposure-Response
(EIA : EHIA)

Chronic Diseases



 



Are those that linger. Degenerative – cause progressive destruction of human tissue. Usually have a poorly defined beginning. Their causes are unclear, often developed over a long time period. Reduce the body’s function for a long time & their treatment is costly because those afflicted require long-term care.

Communicable diseases
  






Are those that are contagious. Transmitted by the causative agent/vector. Eg: cold virus Caused much suffering & millions of deaths. The leading causes of death in most under-developed countries in the world. We can avoid the transmission of many communicable diseases by: a. understanding their modes of transmission b. controlling the causative agents in the environment.

Conditions for communicable diseases

(eg: human being) Infectious disease

(eg: bacteria,viruses)

(eg: air, water, food, crowded conditions)

Comparison of Chronic & Communicable Diseases
(3 dimension)
Chronic Diseases Communicable Diseases

Causes
Timeline Outcome

Often lifestyles or environmentally related Slow; insidous onset; long-lasting

Exposure to a biological agent Usually acute; sudden onset

Often no recovery, gradual deterioration or degeneration

Relatively rapid recovery in most cases

Methods of Disease Transmission
1. Air (air-borne diseases)

- common cold through cough
2. Water (water-borne diseases) - waste products 3. Food (food-borne disease) - provide excellent growth media for biological causative agents

4. Fomites - inanimate objects provide a “resting place” for agents - paper, pen/pencils, doorknobs etc.

5. Animals
- rodents, pets

6. Insects
- flies, mosquitoes

Routes/Discharges of Communicable Transmission
1. Intestinal discharges 3. Zooneses

2. Nose & throat discharges

Routes/Discharges of Communicable Transmission
1. Intestinal discharges
a. Typhoid Fever b. Paratyphoid Fever c. Cholera d. Shigellosis (Bacillary dysentery) e. Amoebic Dysentery f. Poliomyelitis g. Infectious Hepatitis h. Giardiasis i. Ebola-Marburg Diseases

a. Typhoid Fever








Causative agent: Salmonella typhi (about 106 types) Methods of spreading: direct & indirect contact with patient/carrier. contaminated water or food. raw fruit & vegetables. shellfish, especially oysters Effects on the body: systemic bacterial characterized by insidious onset of fever, headache, nonproductive cough. Incubation period: 1 to 3 weeks (2 average)





Chain of infection: Susceptible animal causative agent water, food, flies, roaches. Control measures: sanitary disposal of human excrement control of flies chlorination of water supplies education of public concerning personal cleanliness prevention of overcrowded living conditions proper handling of food, water...
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