- Information
- AI Chat
Communicable Disease Module-1 (1) 240828 121314 240828 123811
Human Anatomy and Physiology (CSPE106)
University of Zimbabwe
Preview text
COMMUNICABLE DIESEASES
NATIONAL CERTIFICATE
IN
ENVIRONMENTAL HEALTH
YEAR 2017
DISEASE
Dysentery
Amoebiasis
Cholera
Typhoid
Polio Viral hepatitis
COMMUNICABLE DISEASES
Definition of terms
Communicable diseases – these are diseases that can be directly or indirectly transmitted from one source to another examples Anthrax, Dysentery, Malaria, STIs, Cholera, TB.
Zoonotic diseases – These are disease of animal origin and can be transmitted from animal to men or vice-versa examples Anthrax, Rabies, TB
Epidemic diseases – Excessive occurrence of a disease in a community or region over a period of time
Epidemicity – Refer to the usual frequency of the disease in the same area among the specified population at the same season of the year.
Pandemic – Refers to the outbreak of disease on a large scale covering a large area or worldwide.
Endemic – These are diseases which are habitually or usually present in a particular geographical region or population group at relatively high prevalence and incidence rate in comparison with other areas or population. If the condition changes in either host, agent and environment an endemic disease may become epidemic.
Sporadic – refers to cases of disease which occur from time to time without a regular pattern example Plague.
Antigen – A substance or bacteria which stimulate the production of antibodies.
USES OF EPIDEMIOLOGY
There are 5 uses of epidemiology:
Planning and evaluation of health care systems.
Identification of disease determinants so as to enable us to prevent them.
Evaluation of methods used in the control of diseases.
Observation of the natural history of the disease.
Classification of diseases.
Planning and evaluation of health care systems.
In order to achieve any meaningful health planning it is mandatory to have careful assessments of the existing health status of the community one is dealing with. This is necessary when there is given limited resources to deliver a sound allocation of resources, equitable distribution of health units and personal knowledge of a particular disease problem affecting communities they are intended for is needed. A complete description of a health status of the community is needed and this include the magnitude, distribution and the frequency of the diseases, incidents, duration of morbidity or disability of the population concerned, age group, sex, occupation and location. As Environmental Health Technicians at local level you are expected to provide the community with necessary information for the purpose of planning, implementing and evaluating health care activities. In this instance, epidemiology provides the tools for you and the community to make national decision concerning your annual and monthly plans.
Identification of disease determinants so as to enable us to prevent them
The major purpose of epidemiological studies of disease causation is to identify disease factors whose manipulation could lead to prevention and control rather than those which cannot be manipulated example Malaria. Malaria is an acute protozoan disease caused by protozoa of the genus called Plasmodium. In terms of prevention we know that such factors as houses built without proper screening increase the attack rate and the presence of water receptacles around the houses and poor drainage facilities promote the breeding of mosquito. Such factors as occupation of these people, poverty, and malnutrition can also be implemented.
As a result of these multiple factors in the causation of malaria it has been recommended to adopt a multi-prolonged or diversified approach to our malaria control program. These include indoor residual spraying (IRS), larviciding, personal protection etc.
Evaluation of methods used in the control of diseases
Evaluation of control methods such as a malaria control programs requires more than demonstration of effective in killing the target mosquitoes. It is also necessary measure a necessary measure the cost of the control method in terms of transport, chemical, manpower and other logistics. The cost effectiveness of the control strategy is compared with cost of other strategies like treatment and the use of insecticide treated nets. The task of monitoring and evaluating the program with both the EHT and the community with the support from the donor. This calls for proper documentation and budgetary monitoring and control.
Observation of the natural history of the disease
Each and every disease has its own natural history starting from inception to prognosis. The disease natural history is required for proper diagnosis treatment of the patient. It also gives the health personnel an idea of the likely outcome of the patient’s illness especially where the natural history of chronic disease is used as a basis for deciding about the therapy. Studio of the natural history of chronic disease requires repeated observations made over many years in communities in which the disease occurs and provide valuable information for preventing and controlling the disease.
Classification of disease
Epidemiological characteristics of diseases are now an integral part of its basic description by means of which it can be defined and recognized. Epidemiology provides general knowledge of disease classification. In general the philosophy of the system is to divide causes of death into broad groups. This deals with diseases caused by effective agents, categories of cancer, allergic disorders, nutritional disorders and those due to accidents.
Manpower analysis.
Family planning purposes.
for budgeting purposes.
DEMOGRAPHY AND EPIDEMIOLOGY
Epidemiologist and demographers study disease patterns, that is, prevalence and incidence.
Prevalence is the total number of new and old cases which occur at a given population and at a given location or demographic place.
Incidence is the number of new cases which occur at a given population, given location and at a given time.
KEY COMPONENTS OF DEMOGRAPHY
Birth rate
Birth rate is the number of newly born babies at a given time in a given population. Birth rate is the most important source of population growth.
Crude
It is the number of total population, that is, men, women who are able to bear children.
Crude birth rate = Total birth x k (1000)
Total population
Example:
In 2006 there were 3000 newly born babies in a population of 7 500 000. Calculate the crude birth rate using K = 1000
Example 2
In 2006 there were 74 000 death in a total population of 7 500 000. Calculate the death rate using K = 1000
Growth rate
Is the percentage increase in a given population?
Growth rate = Crude birth rate – crude death rate
In a normal population increase crude birth rate is usually larger than crude death rate.
Population density
Refers to the concentration of people in a certain area or region.
Population Density = Number of people in a given land
Area of land km 2
Migration
Migration refers to the movement of people from one area to another. It means the area can gain or lose population.
Net migration
It is the difference between the number of people who have moved into an area and the number of people who moved out of an area over the total population.
Net migration = No of immigrants – No of emigrants x 100
Total population in an area
SOURCES OF DEMOGRAPHIC DATA
WAYS IN WHICH DISEASES ARE SPREAD
Diseases can be spread either by direct or indirect contact by disease causing agents through the following mechanism;
(i) Direct contact – Through sexual intercourse example STIs
(ii) Indirect – in these diseases the parasites either has the stage in which it lives outside the body of a man or transmitted to man by an animal. The parasites with a free living stage on the earth examples Roundworm, Hookworm. Diseases transmitted by insect’s examples Malaria, Yellow fever. Diseases which must pass their stages in another animal example are Anthrax, Rabies, foot and Mouth.
(a) Droplets transmission – for example Influenza, TB, Whooping cough,.
(b) Congenital – Mother to child transmission through the placenta.
(c) Blood transfusion – In unscreened infected blood
(d) Fecal Oral route
ROUTES OF TRANSMISSION
(a) Fecal Oral Route
(b) Sexual Transmission
(c) Oral transmission
(d) Droplet transmission
Fecal Oral Route
Fingers
Faeces Flies Food Mouth
Fields/Soil
Fluids/water
The host
Refers to a person or animal who is infected by the agent. It has 2 main defense mechanisms which are nonspecific and specific. Factors affecting the host in determining the occurrence of diseases are;
Immunity Behavior Age Genetic material Occupation Nutrition
Agent
Anything which can spread disease (causative organism of a disease)
Properties of agents
(a) Biological – examples are bacteria, fungi, viruses, rickettsia, protozoa, arthropods
(b) Chemical – examples are pesticides (DDT), drugs, herbicides
(c) Physical – examples are accidents, extreme temperatures, guns, automobile emissions (carbon monoxide, carbon dioxide, sulphur dioxide which is carcinogenic and can cause Bronchitis and Lung cancer).
Characteristics of infectious disease agent
(i) Infectivity – refers to organisms capacity to multiply in or on the tissue of the host
(ii) Pathogenicity – Implies with organisms capacity to cause disease in an infected host.
(iii) Virulence – Is the pathogenicity of an organism in a specified host. The amount/dose of pathogens which is needed to cause disease in a susceptible host.
(iv) Toxigenicity – refers to the ability of a micro-organism to produce biochemical, known as toxins that disrupt the normal functions of cells that are generally destructive to human cells.
(v) Immunogenicity – Is the capacity of an organism to induce specific or lasting immunity in the host.
Environment
Refers to the domain in which the disease causing organism/agent may exist, survive, originate.
Characteristics of environment
(i) External environment – Maybe physical eg population density, temperature, rainfall and humidity.
(ii) Biological environment – The presence of dense vegetation and animals.
(iii) Socio – economic environment – urbanization, war, nutrition status.
The degree in which people, can alter their personal behavior often less to the environment in which they live. People can change their environment if they are determined.
IMMUNITY
(attenuated pathogens). Artificial active immunity is permanent, the individual is protected from the disease all of his life.
PASSIVE IMMUNITY
This is the result of antibodies being passed into an individual in some way rather than being produced by the body itself. It can be natural acquired or artificial acquired immunity. Passive immunity can be acquired in 2 ways;
(i) By injection of antibodies from an animal or person who has acquired active immunity.
(ii) Temporary immunity acquired by child from antibiotics transferred from mother, either whilst the child is in the womb or when the child is being breastfed.
(a) Natural passive
This immunity is acquired by the fetus on new born either from the mother via the placenta during pregnancy or during breastfeeding. This type of immunity is short lived, it lasts for 6 months.
(b) Artificial passive immunity
Acquired by means of injecting serum or a pale straw colored liquid consisting of 80% water, 10% variety of substances in solution and suspension plasma from which clotting protein fibrogen has been removed containing antibodies to which an individual who may have been infected with a particular pathogen or disease. Since this type of immunity is temporal it requires repeated administration of serum containing the antibodies. This type of immunity is not commonly practiced because of the risk of kidney failure from such repeated administration of complex proteins. Passive immunity is short lived compared to active immunity.
HERD IMMUNITY
In immunological herd immunity refers to the situation in which a high percentage of the population is immunized to a disease, essentially stopping a disease in its track because it cannot find a new host. It is also called community immunity. The threshold for herd immunity varies depending on the disease with more virulent agent requiring vaccination of a higher percentage of the population to create the desired herd immunity. Besides being used in disease prevention, community or herd immunity is utilized to fight ongoing outbreaks. It is measured by exposing the proportion of non susceptible as a percentage of the total population.
PRINCIPLES OF CONTROLLING COMMUNICABLE DISEASES IN
RELATION EPIDEMIOLOGICAL TRIAD
The aim of control is to tip the balance against the agent and this may be done by:
(a) Attacking the source of infection
(b) Interrupting the route of transmission
(c) Protecting the host
Attacking the source
Treatment of cases – Use of effective drugs to treat cases. Treatment of subclinical cases and carriers must be treated and efforts to trace and find them, as they may not usually present with any apparent illness. Mass treatment/mass immunization Isolation of cases Reservoir control – chemoprophylaxis drugs (use of suppressive drugs)
Interrupting the route of transmission
Environmental sanitation example Malaria – cutting grasses, filling water wagging areas.
TB – avoid the use of overcrowded rooms.
Cholera – proper disposal of human excreta.
The purpose of primary prevention is to limit the incidence of disease by controlling the causes of the risk factors. These include:
Reducing the levels of pollution to below recommended guidelines standards. Mass immunization - Expanded Immunization Program (EPI) Vaccination Health education Provision of proper and adequate nutrition vi) Environmental – ensure safe water supplies, food hygiene, excretal and refuse disposal, disinfection and sterilization, vector and reservoir control, good living and good working conditions
Secondary prevention
It involves treatment of cases to reduce the serious consequences of the diseases. This is achieved through:
early diagnosis and early treatment of diseases contact tracing disease surveillance (close observation) screening of patients Health Education Isolation
It comprises the measures available to individual and population for early detection and prompt interventions.
Tertiary prevention
It aims at reducing the progression of a disease into complications. It consists of measures intended to reduce impairments and disabilities:
Rehabilitation Provision of food with proper nutrition Provision of drugs Health Education
DUTIES OF ENVIRONMENTAL HEALTH PRACTITIONERS (ROLES)
Disease prevention and control (local and external).
Health and hygiene Education –
awareness campaign dramas posters Dissemination of health information to the population so as to implement control measures.
Premises inspection – EHO or EHTs inspect public premises so as to ascertain that they meet required standards.
Waste management – EHO and EHTs monitors to see that every household has a refuse bin.
Citing of toilets and supervising the construction of toilets Educate the community on proper waste disposal.
Food quality monitoring – involves taking samples for investigation
Water quality monitoring – involves taking of water samples to check if water is safe. It ensures that the general public has potable and wholesome water for use through water testing eg bacteriological and chemical testing.
Monitors the constitute of air.
AGENTS OF INFECTION
BACTERIOLOGY/MICROBIOLOGY
It is the study of all microforms that cannot be seen with the naked eye. Some micro-organisms are beneficiary to life but causes disease and these are called pathogenic. Micro-organisms need food and suitable temperature for them to live and multiply. Micro-organisms are found everywhere, in air, food, water, skin, and soil or in animals carried by insects and others can leave in dry state for a long time. Some need oxygen and these are called aerobic. Some do not require oxygen
Communicable Disease Module-1 (1) 240828 121314 240828 123811
Course: Human Anatomy and Physiology (CSPE106)
University: University of Zimbabwe
- Discover more from:
