BLGY1211 Basic concept of epidemiology of animal diseases
Disease
Any departure from specified criteria of normality
Inability to perform physiological functions at normal levels, provided nutrition and
other environmental requirements are provided at adequate levels
It can be; infectious, non-infectious, contagious, metabolic, simple etiology, multiple
or complex etiology, sporadic, endemic, epidemic, pandemic, clinical, non-clinical
Sporadic: occurring in a scattered and irregular manner (breast cancer)
Endemic: always present in certain population and region (chicken pox, malaria)
Epidemic: sudden severe outbreak within a region
Pandemic: occurs when epidemic becomes widespread and affect whole region,
continent or world
Challenges for today’s animal and veterinary
Large herds/flocks
Regions remaining diseased after lengthy disease control campaigns
Economic aspect of disease control through cost/benefit analysis of disease control
programs costly multi-factorial diseases complexes such as mastitis, lameness in
cattle, TB are common
Old emerging or new diseases with complex aetiology, such as FMD, BSE, TB, Avian
Influenza (Bird flu)
Antimicrobial resistance and superbugs (Clostridium difficile, MRSA)
Public health concerns
Identification (abnormality and causes) quantification (how much, where, when)
intensive examination of multiple, directly or indirectly casual and interacting
disease determinants
Epidemiology provides tools, which can be used to approach these new challenges
Terminology
Infection - Invasion and multiplication of microorganisms in body tissues, especially
that causing local cellular injury due to competitive metabolism, toxins, intracellular
replication, or antigen-antibody response
Incubation period - Development of an infectious disease from the time of the
entrance of pathogen to the appearance of clinical symptoms
Reservoir - An alternate host or passive carrier of pathogenic organism. e.g. Badger
for TB, Rat for leptospira
Morbidity - The term morbidity is used to refer to the extent of disease or disease
frequency within a defined population Morbidity can be expressed as either
prevalence or incidence
Prevalence - number of existing cases of a given disease that exists in a population at
a specified point in time No. of existing case at specific time / The population at
risk at specific time X 1000
Incidence - This is the number of new cases of a disease or disorder that arises in a
defined population over a defined period of time No. of new cases at specific
time / The population at risk at specific time X 100
Disease
Any departure from specified criteria of normality
Inability to perform physiological functions at normal levels, provided nutrition and
other environmental requirements are provided at adequate levels
It can be; infectious, non-infectious, contagious, metabolic, simple etiology, multiple
or complex etiology, sporadic, endemic, epidemic, pandemic, clinical, non-clinical
Sporadic: occurring in a scattered and irregular manner (breast cancer)
Endemic: always present in certain population and region (chicken pox, malaria)
Epidemic: sudden severe outbreak within a region
Pandemic: occurs when epidemic becomes widespread and affect whole region,
continent or world
Challenges for today’s animal and veterinary
Large herds/flocks
Regions remaining diseased after lengthy disease control campaigns
Economic aspect of disease control through cost/benefit analysis of disease control
programs costly multi-factorial diseases complexes such as mastitis, lameness in
cattle, TB are common
Old emerging or new diseases with complex aetiology, such as FMD, BSE, TB, Avian
Influenza (Bird flu)
Antimicrobial resistance and superbugs (Clostridium difficile, MRSA)
Public health concerns
Identification (abnormality and causes) quantification (how much, where, when)
intensive examination of multiple, directly or indirectly casual and interacting
disease determinants
Epidemiology provides tools, which can be used to approach these new challenges
Terminology
Infection - Invasion and multiplication of microorganisms in body tissues, especially
that causing local cellular injury due to competitive metabolism, toxins, intracellular
replication, or antigen-antibody response
Incubation period - Development of an infectious disease from the time of the
entrance of pathogen to the appearance of clinical symptoms
Reservoir - An alternate host or passive carrier of pathogenic organism. e.g. Badger
for TB, Rat for leptospira
Morbidity - The term morbidity is used to refer to the extent of disease or disease
frequency within a defined population Morbidity can be expressed as either
prevalence or incidence
Prevalence - number of existing cases of a given disease that exists in a population at
a specified point in time No. of existing case at specific time / The population at
risk at specific time X 1000
Incidence - This is the number of new cases of a disease or disorder that arises in a
defined population over a defined period of time No. of new cases at specific
time / The population at risk at specific time X 100
