Human beings, animals, insects, soil, water and food can all act as sources or reservoirs of infection. Pathogens can survive and multiply in these reservoirs, allowing transmission to new hosts. Specifically, humans themselves can act as reservoirs by harboring microbes internally and transmitting them to others directly or indirectly. Animals like bats, mice and livestock also act as reservoirs for zoonotic diseases transmissible to humans like rabies, Lyme disease, tuberculosis and brucellosis. Non-living reservoirs include air, soil, water and food, which can harbor infectious particles or pathogens for periods of time, allowing spread via dust, contaminated materials or consumption.

1. SOURCE OF INFECTION
DR. S. DHIVA
ASSISTANT PROFESSOR IN MICROBIOLOGY
SREE NARAYANA COLLEGE, ALATHUR, PALAKKAD

2. Definition
• An object in which the agent of infection lives and
propagates.
• Source can either be a living organisms or an
inanimate object, that provides a pathogen an
adequate condition
• for survival and multiplication and
• an opportunity for transmission
• Such source is called reservoir of infection
• Sources may be - human beings, animals, insects,
soil, water and food

3. • Human body itself Is a reservoir of disease
• Harbors microorganisms and transmits directly or indirectly to
others
• People with signs and symptoms of disease may transmit the
infection to others
• Some may transmit infection to others without exhibiting sign or
symptoms
• They are called carriers, living reservoir of infection
• Some carriers have inapparent infection - where no clinical sign and
symptoms appears
• Some carriers have latent infection, carry disease during symptom
free stages or during incubation period before symptoms appear or
during recovery ( convalescent period)
• Ex. AIDS, Diptheria, typhoid fever, hepatitis, gonorrhea, amoebic
dysentery and streptococcal infections
HUMAN RESERVOIR

4. ANIMAL RESERVOIR
 Both wild and Domestic animals acts as reservoir
 Diseases that occur primarily in animals can be transmitted to humans
are called zoonotic diseases
 Ex. Rabies, found in bats, skunks, foxes, dogs and cats
 Lyme disease found in field mice
 Drinking contaminated cow’s milk leads to tuberculosis and brucellosis
 Transmission of infection from animals to humans takes place either by
direct contact or by contact with their waste such as cleaning of litter
box, cage, etc.,
 By contamination of food and water
 By air from contaminated hides, fur or feathers (inhaling dust
contaminated excreta) leads to Q fever, anthrax, etc.,
 By consuming infected animal products, or by insect vectors

5. Non living Reservoirs
 Air
 Soil
 Water
 Food

6. AIR
 Infectious dust carrying droplets or droplet nuclei acts as
source of infection
 Dust carrying nasal droplets, excreta, or dried infectious
particle remains in the particular environment for a
particular period of time
 Based on the flow of air these infectious particle move to
other areas and cause infection to susceptible individuals

7. SOIL
 Soil harbours pathogens such as fungi , which causes
mycosis including ringworm and systemic infection
 Bacteria such as Cl.botulinum which causes botulism and
Cl. tetani that causes tetanus, both organisms are found
in the intestine of horses, cattles as normal flora
 These pathogens are commonly found in the places where
these faeces are used as fertilizers

8. WATER
 Water that has been contaminated by the faeces of human
and other animal acts as reservoir of several pathogens
 These pathogens are responsible for gastrointestinal
infection or diseases
 Ex. V. cholera, which causes cholera
 Salmonella typhii which causes typhoid

9. FOOD
 Improperly prepared or stored food acts as reservoir for
food borne pathogens which leads to food poisoning
 Ex. Trichimosis, Salmonella, amoebiasis, etc.,
INSECT VECTORS
 Spreads organisms from one host or another
 Ex. Mosquito, ticks, fleas, mites or bitting flies (equine
encephalitis and malaria, lyme disease, Rocky Mountain
spotted fever, plague, scrub typhus and tularemia