There are various epidemiological subdisciplines
1. Clinical epidemiology
Clinical epidemiology is the use of epidemiological
principles, methods and findings in the care of
individuals, with particular reference to diagnosis and
2. Computational epidemiology
Application of computer science to epidemiological
studies. Representation of disease by mathematical
models and the use of expert systems. (formulating
disease control strategies. , predicting animals
productivity. Supporting management decisions)
3. Genetic epidemiology
Genetic epidemiology is the study of the cause,
distribution and control of disease in related
individuals, and of inherited defects in populations.
Also explore Interactions between genetic and non-
4. Field epidemiology
Field epidemiology is a timely, judgmental process
based on description, analysis, common sense and
the need to design practical control policies
When outbreaks of foot-and –mouth disease occur,
field epidemiologists promptly trace potential sources
of infection in an attempt to limit spread of the
5. Participatory epidemiology
1980 with development of veterinary services,
animals were economically and socially important, use
of local knowledge to gain information, with the main
goal of improving animal health
Techniques that are employed evolved in the social
science, and consist of simple visual methods and
interviews to generate qualitative data
“Participatory epidemiology” it is a tool for the field
epidemiologist, which is increasingly used in
developing counties. Is concerned with local
knowledge of, and practices relating to, the health of
6. Molecular epidemiology
Study of small genetic and antigenic differences
between viruses and other microorganisms at a
higher level of discrimination
The methods include peptide mapping, nucleic acid
‘fingerprinting’ and hybridization, restriction enzyme
analysis, monoclonal antibodies and the polymerase
Nucleotide sequencing of foot-and–mouth that some
outbreaks of the disease involved vicinal strains,
suggesting that improper inactivation or escape of
virus from vaccine production plants. Unrestricted
animals movement is a major factor in dissemination
of the disease in West Africa.
Subdisciplines of Epidemiology
Environmental Epidemiology: concerned
with the relationship between disease and
environmental factors such as industrial
pollution and occupational hazards
Micro-Epidemiology: study of disease in a
small group of individuals with respect to
factors that influence its occurrence in larger
segments of the population
Macro-Epidemiology : study of national
patterns of disease, and the social, economic
and political factors that influence them
Subdisciplines of Epidemiology
Chronic disease epidemiology
Components of epidemiology
The first stage in any investigation is the
collection of relevant data.
Investigations can be either qualitative
or quantitative or a combination of these
The natural history of disease
The ecology of diseases, including the distribution,
mode of transmission and maintenance of infectious
diseases, is investigated by field observation. Field
observations also may reveal information about
factors that may directly or indirectly cause disease.
Causal hypothesis testing
If filed observations suggest that certain factors may
be causally associated with a disease, than the
association must be assessed by formulation a causal
Quantitative investigations involve
measurement (e.g., the number of cases of
disease), and therefore expression and
analysis of numerical values. Quantitative
investigations include surveys, monitoring
and surveillance, studies, modeling, and
the biological and economic evaluation of
disease control. Walls of the research
organization- ‘armchair epidemiology’.
A surveys is an examination of an aggregate of units.
Surveys can be undertaken on a sample of the
A census, a cross-sectional survey records events
occurring at a particular point in time.
A longitudinal survey records events over a period of
time. Prospectively form the present into the future;
on may be a retrospective record of past events.
In epidemiological surveys, characteristics might
include the presence of particular diseases, or
production parameters such as milk yield.
A particular type of diagnostic survey is screening.
Identification of undiagnosed cases of disease using
rapid tests or examination
Screening tests are not intended to be diagnostic;
individuals with positive test results (i.e., that are
classified as diseased by the screening test) usually
require further investigation for definite diagnosis.
They therefore differ from diagnostic tests.
Screening involves investigation of the total
population (mass screening). Targeted at animals
only in areas where there have been cases of disease
(strategic screening). Prescriptive screening aims
at early identification of diseases that can be
controlled better if they are detected early in their
Monitoring and surveillance
Monitoring is the making of routine observations on
health, productivity and environmental factors and
the recording and transmission of these observations.
Recording of milk yields or routine recording of meat
inspection findings at abattoirs.
Surveillance is a more intensive form of data
recording than monitoring. Used to describe the
tracing and observation of people who were in contact
with cases of infectious disease. Include all types of
disease – infectious and non-infectious
It is normally part of control programmes for specific
There are four main types of
1. experimental studies;
2. cross-sectional studies;
3. case-control studies;
4. cohort studies.
Using mathematical equations ‘Modelling’.
Evaluation of the risk of the occurrence of adverse,
development of formal methods of quantitative and
quantitative risk assessment. e.g Microbiological risk
assessment with food safely risks, and estimation of the
magnitude of microbial exposure at various stages in the
production chain (rearing on the farm; transport and
processing; retail and storage; preparation) to
campylobacter spp and salmonella spp.
The goal of epidemiology is to improve the veterinarian's
knowledge so that diseases can be controlled effectively,
and productivity thereby optimized. This can be fulfilled by
treatment, prevention or eradication