presentation about the communicable diseases (TB,malaria,filaria,leprosyand AIDS) their causative organs,prevention factors causes these diseases are clearly explained in these slides..

2. Tuberculosis
 Tuberculosis is a specific infectious disease caused by
MYCOBACTERIUM TUBERCULOSIS.
 The disease primarily effects lungs and causes
pulmonary tuberculosis. It can also effect intestine,
meninges, bones and joints, lymph glands, skin and
other tissues of the body.
 The disease is usually chronic with varying clinical
manifestations.

3. Problem statement
 Tuberculosis remains a worl wide public health
problem despite the fact that the causative organism
was discovered more than 100 years ago and highly
effective drugs and vaccines are available making
tuberculosis a preventable and curable disease
 DOTS (Directly Absorbed treatment Short cource)
remains central to the public health approach to
tuberculosis control, which is now presented as stop
TB strategy .

4. Natural history of TB
Agent factors:-
I. Agent:- Mycobacterium tuberculosis is a facultative
intra cellular I.e it is readily ingested by phagocytes
and is resistant to intra cellular killing.
II. Source of infection:- there are two sources of
infection- human and bovine
III. Communicability:-Patients are infective as long as
they remain un treated. Effective antimicrobial
treatment reduces infectivity by 90% within 48
hours.

5.  Host factors:-
I. Age:- Tuberculosis effects all ages developing
countries show a sharp raise in infection rates from
childhood to adolescence in the developed the
disease is more common in the elderly
II. Sex:- More prevalent in males than in females
III. Heredity:- TB is not a hereditary disease
IV. Nutrition:- Malnutrition is widely believed to
predispose to TB but the available evidence on this
point is only indirect
V. Immunity:- It is acquired as a result of natural
infection or BCG vaccination

6.  Social factors:-
The social factors include many non medical factors
such as poor quality of life, poor housing and over
crowding , population explosion, under nutrition, lack
of education, large families, early marriages, lack of
awareness of causes of illness, ETC.
All this factors are inter related and contribute to the
occurrence and spread of tuberculosis

7. Mode of transmission
 TB is transmitted mainly by droplet infection and droplet
nuclei generated by sputum positive patients with
pulmonary tuberculosis.
 To transmit infection, the particles must be fresh enough to
carry a viable organism.
 The frequency and vigor of cough and the ventilation of the
environment influence transmission of infection.
 TB is not transmitted by fomites, such as dishes and other
articles used by the patients
 Sterilization of these articles is therefore of little or no
value.

8. Incubation period
 The time from receipt of infection to the development
of positive tuberculin test ranges from 3-6 weeks, and
there after, the development of disease depends upon
the closeness of contact, extent of the disease and
sputum positivity of the source case(dose of infection)
and host parasite relationship.
 Thus the incubation period may be weeks months or
years

9. Control of TB
 TB control means deduction in the prevalence and
incidence of disease in the community.
 WHO defines that tuberculosis “control” is said to be
achieved when the prevalence is natural infection in
the age group 0-14 years of the order of 1%
 Since TB is an infectious disease, the basic principles
of prevention and control are the same as for any other
infectious disease .
 The control measures consist of a curative component-
namely case finding and treatment and a preventive
component – namely BCG vaccination

10. BCG vaccination
 (Bacillus Calmette Guerin)
Aim :- To induce a Benign, artificial primary infection
which will stimulate an acquired resistance to possible
subsequent infection with virulent tubrcle bacilli, and
thus reduce the morbidity and mortality from primary
TB among those most at risk
Vaccine:- BCG is the only widely used live bacterial
vaccine it consists of living bacteria derived from an
attenuated bovine strain of tubercle bacilli
Types of vaccine :- There are 2 types of BCG vaccine-
the liquid (fresh vaccine and the freeze- dried vaccine)

11. Dosage :- For vaccination the usual strength is 0.1mg
in 0.1ml vol.
The dose to new born age below 4 weeks is 0.05
ml.
Age :- In countries where TB is prevalent and the risk
of childhood infection is high (As in India) the
national policy is to administer BCG very early in
infancy either at birth ( for institutional deliveries) are
at 6 weeks of age simultaneously with other
immunizing agents such as DPT and polio

12. Malaria
 Malaria is a protozoal disease caused by infection with
parasites of the genus plasmodium and transmitted to
man by certain species of infected female anopheles
mosquito . The clinical features of malaria vary from
mild to severe, and complicated, according to the
species of parasite present, the patient state of
immunity, the intensity of the infection and also the
presence of concomitant conditions such as
malnutrition or other diseases.

13. Epidemiological Determinants
 Agent factors
1. Agent – Malaria in man is caused by four distinct
species of the malaria parasite – P.vivix, P.falciparum,
P.malariae and P.ovale . Malaria parasite undergoes
two cycles of development – the human cycle
(asexual cycle) and the mosquito cycle (sexual cycle).
Man is the intermediate host and mosquito is the
definitive host.

14.  Host factor
1. Age – Malaria effects all ages, newborn infants have
considerable resistance to infection with
P.falciparum . This has been attributed to the high
concentration of fetal hemoglobin during the first
few months of life, which suppresses the
development of P.falciparum.
2. Sex – Males are more frequently exposed to the risk
of acquiring the malaria than females because og the
outdoor life they lead.
3. Pregnancy – Pregnancy increases the risk of malaria
in women. Malaria during pregnancy may cause
death of fetus. It may also cause pre-mature labour or
abortion.

15. 4. Housing
Housing plays an important role in the epidemiology of
malaria. The less ventilated houses provide ideal indoor
resting places for mosquitoes. Malaria is acquired in
most instances by mosquito bites within the home.
 Immunity
The epidemic of malaria is influenced by the immune
system of population. Immunity to malaria in humans is
acquired only after repeated exposure over several years.

16.  Environmental Factors
India’s geographic position and climatic conditions had
been favorable to the transmission of malaria for a long
time. 1) Season – Malaria is a seasonal disease. In most
parts of India, the maximum prevalence is from July to
November. 2) Temperature – Temperature effects the life
cycle of the malaria parasite. The optimum temperature
for malaria parasite in vector is between 20 – 30 degree
Celsius and the parasite undergoes development in
mosquito if the temperature is below 60 degree Celsius.

17.  Mode of transmission
1. Vector transmission – Malaria is transmitted by the
bite of certain species of infected, female, Anopheles
mosquito. A single infected vector, during her life
time may infect several persons.
2. Direct transmission – Malaria maybe induced
accidentally by hypodermic intramuscular and
intravenous injections of blood.

18.  Incubation Period
The duration of incubation period varies with the
species of the mosquitoes ,i.e. for falciparum malaria 12
(9-14) days, for vivax malaria 14 (8-17) days, for quartan
malaria 28 (18-40) days, for ovale malaria 17 (16-18) days.

19. Lymphatic filariasis
 The term “lymphatic filariasis” covers infection with
three closely related nematode worms- W.bancrofti,
B.malayi and B.timori.
 All three infections are transmitted to man by the bites
of mosquitoes.
 Infection though not fatal, the disease is responsible
for considerable suffering, deformity & disability

20. Problem statement
 Filariasis is a global problem.
 It is a major social and economic scourage affecting
over 83 countries.
 The formal goal of the global lymphatic filariasis
program is to eliminate the disease “as a public health
problem” and 2016 is the informal target date for
interrupting transmission.

21. Epidemiological determinants
 Agent factors :- Fhere are at least 8 species of filarial
parasites that are specific to man. They are Wuchereria
bancrofti, Brugia malayi, Brugia timori, Onchocerca
volvulus, loa loa, T.perstans, T.streptocerca and
Mansonlella ozzardi
 Host factors:- man is a natural host
 Age:- all ages are susceptible to infection. Infection
rates rise with age up to the age of 20-30 years and then
level off.
Sex:- men are mostly affected.

22. Migration :- the movement of people from one place to
another as led to the extension of filariasis into areas
previously non endemic.
Immunity :- men may develop resistance to infection
only after many years of exposure. the immunological
basis of this resistance is not known.
Social factors :- lymphatic filariasis is often associated
with urbanization, industrialization, migration of
people, illiteracy, poverty and poor sanitation

23.  Environmental factors :-
Climate :- climate is an important factor in
epidemiology of filariasis. It influences the breeding of
mosquitoes, their longevity and also determines the
development of the parasite in the insect vector.
Drainage :- lymphatic filariasis is associated with bad
drainage. The vectors breed profusely in polluted
water.

24. Mode of transmission
 Filariasis is transmitted by the bite of infected vector
mosquitoes .
 The parasite is deposited near the site of puncture it
passes through the punctured skin or may penetrate
the skin on its own and finally reach the lymphatic
system.
 Incubation period :- the period of incubation is 8-16
months it can be even longer

25. Leprosy
 Is a chronic infectious disease caused by M.leprae .
 Mainly affects the peripheral nerves, it also affects the
skin, muscles, eyes, bones and internal organs
Problem statement :- in 1991, WHO member states
resolved to decrease the level of leprosy in the world
by over 90%. This has now been accomplished, and the
overall target for the global elimination of leprosy as a
public health problem has been attained.

26. Epidemiological determinants
 Agent factors :-
 Agent :- leprosy is caused by M.leprae .
 Host factors :-
 Age :- leprosy is not particularly a disease of children as was
once believed. Infection can take place at any time
depending upon the opportunities for exposure.
 Sex :- both the incidence and prevalence of leprosy appear
to be higher in males than in females in most regions of the
world.
 Migration :- in india leprosy was considered to be mostly a
rural problem however because of the movement of the
population from rural to urban areas, leprosy is creating a
problem in the urban areas also.

27.  Immunity :- it is a well established fact that only few
persons exposed to infection develop the disease.
 Environmental factors :- the risk of transmission is
predominantly controlled by environmental factors
 The presence of infectious cases in the environment. There
is evidence that humidity favours the survival of M.leprae
in the environment.
 Over crowding and lack of ventilation with in house holds.
 Mode of transmission :-
• Droplet infection
• Contact transmission
• Other routes

28. Incubation period
 Leprosy has a long incubation period, an average of 3-5
years or more for lepromatous cases. Symptoms can
take as long as 20 years to appear.
 Some leprologists prefer the term “latent period” to
incubation period because of the long duration of the
incubation period.

29. AIDS(Acquired Immunodeficiency
Syndrome)
 Aids is a fatal illness caused by a retro virus known as
the Human immunodeficiency Virus (HIV) which
breaks down the body’s immune system.
 Problem statement :- AIDS has rapidly established
itself throughout the world and is likely to endure and
persist well into the 21st century
 AIDS has evolved form a mysterious illness to a global
pandemic which has infected tens of millions in less
than 20 years.

30. Epidemiological features
 Agent factors :-
 Agent :- when the virus was first identified it was called
“lymphadenopathy associated virus” (LAV) by the French
scientist .researchers in USA called it “human T cell L
lymphotropic virus III (HTLV-III). In may 1986, the
international committee on the taxonomy gave it a new
name human immunodeficiency virus (HIV).
 Source of infection :- the virus has been found in greatest
concentration in blood, semen and CSF. To date, only
blood and semen have been conclusively soon to transmit
the virus.

31.  Host factors :-
Age :- most cases have occurred among sexually active
persons aged 20-49 years. This group represents the
most productive members of the society and those
responsible for child baring child rearing.
Sex :- certain sexual practices increase the risk of
infection more than others Ex: multiple sexual
partners, anal intercourse, and male homo sexuality .
Higher rate of HIV infection is found in prostitutes.
High risk groups :- male homosexuals and bisexuals,
hetero sexual partners(including prostitutes),
intravenous drug abusers, transfusion recipients of
blood and blood products, clients of STD

32.  Immunology :-
 The immune system disorders associated with HIV
infection/AIDS are considered to occur primarily from the
gradual depletion in WBC.
 Modes of transmission :-
 Sexual transmission
 Blood contact
 Maternal-fetal transmission
 Incubation period :-
 The natural history of HIV infection is not yet fully known,
current data suggest that the incubation period is
uncertain(from a few months to years or even more) from
HIV infection to the development of AIDS.