• Zoo- animal, -noses: diseases (Greek)
• Zoonotic diseases are also known as Zoonosis and
Zoonoses are the diseases that are naturally
transmissible to a human from other vertebrates
• The pathogens may be bacteria, viruses, fungi or
• They amount to more than about 150 diseases
thought to be originated from animals, such as
measles, smallpox, diphtheria, AIDS (from
•Reverse zoonoses are
diseases that humans
give to animals. These
diseases are the
diseases humans think
they can get from
animals don’t such as
feline leukemia, feline
AIDS, pinworms etc.
• A/C TO LIFE CYCLE OF THE PATHOGEN –
a) Orthozoonoses- are the diseases maintained in
nature in a single vertebrate host. E.g.- Rabies,
maintained in Canids.
b) Cyclozoonoses- require more than one vertebrate
host to maintain their life cycle. E.g. Echinococcosis
c) Metazoonoses- require both, a vertebrate and an
invertebrate host, for development. E.g.-
Trypanosomes in Humans and flies.
d) Saprozoonoses- are the diseases that require
a vertebrate host and another type of
environmental reservoirs(food or soil). E.g.
Listeriosis and Histoplasmosis.
a) Anthropozoonoses- are the diseases primarily
transmitted from lower vertebrates to human beings.
E.g. Rabies(Lyssa virus), Anthrax(Bacillus anthracis),
Brucellosis(Brucella abortus)- Malta fever, Undulant fever
or Mediterranean fever.
b) Zooanthroponoses- are the diseases transmitted from
human beings to lower vertebrates.
E.g. Amoebiasis (Entamoeba histolytica), Diphtheria
c) Amphixenoses- are the diseases that may be transmitted
in either direction.
E.g. Staphylococcal, Streptococcal infection
• Humans are often accidental and dead-end
hosts for Zoonotic diseases
• The animals are the definitive hosts
• Sometimes the animal may get ill from the
pathogen and sometimes don’t.
• When the animal host doesn’t become ill but
is still capable of transmitting the disease to
people, it is said to be carrier or a reservoir
1. Ecological changes in man's environment- E.g.
Leptospirosis, Tuleraemia, Helminthic infections etc.
2. Handling animal by-products and wastes (occupational
hazards) - e.g. anthrax in carpet weavers, Leptospirosis
in rice field workers, trypanosomiasis in hunters,, Q-fever
in abattoir and rendering plant workers, jungle yellow
fever and tick borne diseases in wood cutters, bovine
tuberculosis in farmers etc.
3. Increased movements of man Amoebiasis, Giardiasis,
Salmonellosis, Shigellosis, etc
4. Increased trade in animal products - e.g. Salmonellosis,
Foot and mouth disease, Anthrax, Newcastle disease etc.
I. Increased density of animal population
– e.g. Dermatophytosis, Tuberculosis,
I. Transportation of infected animals e.g.
Yellow fever Chikungunya fever, Dengue
II. Cultural anthropological norms –In
Kenya, people allow the dogs and hyenas
to eat human dead bodies infected with
• Most Notable instances of
outbreaks have been seen to
have started from or transmitted
1. Plague- most recent outbreak
was recorded in 1994, of
bubonic and pneumonic plague.
The plague is responsible for
estimated 475 million of deaths in
Europe in the 16-17th century
and known as “BLACK DEATH”.
o The causative agent is
o Reservoirs- Rodents,
o Now vaccines are
available along with
• Spread of the Bacillus
anthracis to man happens.
• Reservoirs- Sheep, Cows,
• Common in west and central
Africa than in India.
• Transmission- inhalation of
mea of infected animals.
• Treatment- by antibiotics
: from Mycobacterium bovis
• Reservoir : Cattle
• Transmission: i)Food borne: unpasteurized milk and
ii)M avium- Reservoir : Birds
• Risk for immunocompromised persons: Elderly, HIV or
: Spirochete leptospira
icterohemorrhagica infection (Reservoir-rats)
• Transmission - Urine-> Soil, Water and Tissues
Contaminated with Leptospires.
• C/C- Fever, Malaise, Weil’s diseases(acute severe
• RNA virus from the family
• However, the death toll
was of 500+ in India.
• Reservoirs- Pigs, humans
• Pandemics- 1918-1933:
‘Spanish Flu’(recorded 40
million deaths globally)
‘Asian Flu’(2 million
• Rabies is one of the most important oldest recognized
diseases in India.
• It has been recognized in India since the Vedic period
(1500–500 BC) .
• Is a highly fatal Zoonotic viral encephalitis.
• Genus-Lyssavirus Family-Rhabdoviridae,
• Reservoirs- carnivores (dogs, cats, foxes, jackal etc),
human beings, Bats
• Rabies is transmitted by bites of rabid animals(dogs 95%),
corneal transplant, sexual contact, tissues of an infected
animal or fresh wound that come into contact with saliva or
tissues of an infected animal.
Nipah Virus infection (NiV) is an
emerging infectious disease of in the
South-East Asia Region.
Genus Henipavirus in the subfamily
Reservoir: Fruit bats (Genus Pteropusa) .
There were focal outbreaks of NiV in
Bangladesh and India during winter in
2001. A second outbreak was recorded in
2018 in Kerala
An illness of mysterious fever with high
case fatality is reported as the
• DENGUE FEVER
• Also known as break bone fever
• Transmission- Bite of Aedes aegyptii during early morning & in
• C/f- Saddle back fever, headache, retrobulbar pain, morbiliform
rash appears on trunk & spreads centripetally to face, trunk &
limbs. Fever lasts for 5- 7 days
• Reservoirs- Mosquitoes and humans
• JAPANESE ENCEPHALITIS
• Caused by Japanese encephalitis virus . JE was first recorded in
Vellore and Pondicherry in mid 1950s.
• Transmitted through Zoonotic
• Vector- Bite of Culex tritaenniorhynchus
• C/f- Fever, rigors, headache & vomiting
• Reservoirs- Pigs, Mosquitoes, Water birds
• As of 6 April 2020, a cumulative total of 12,00,000+ COVID-19
cases were reported in globally, with 4287 in India.
• COVID-19 is a Zoonotic virus. Bats appear to be the reservoir
of COVID-19 virus, but the intermediate host(s) has not yet
been identified. However, further research is sill going on
about the disease.
• The median age is 51 years (range 2 days-100 years old) with
the majority of cases (77.8%) lying between 30–69 years.
• COVID-19 is transmitted via droplets and fomites during close
unprotected contact between an infector and infectee.
Airborne spread has not been reported
• Fecal shedding has been demonstrated from some patients
LABRATORY DIAGNOSIS OF DISEASES
DISEASE SAMPLE MICROSCOPY CULTURE SEROLOGY
LEPTOSPIROSIS BLOOD, URINE DARK GROUND
TB(M bovis) SPUTUM ACID FAST BACILLI L J MEDIA -----------------------
TYPHUS BLOOD ----------------------- YOLK SAC OF
TISSUE CULTURE ---------------------
STOOL EGG ----------------------- ELISA, INDIRECT
LEISHMANIA BLOOD AMASTIGOTE
FUNGAL SKIN,NAIL,HAIR KOH PREPARATIONSDA ------------------------