This document provides an overview of the epidemiology of malaria. It describes malaria as a disease caused by plasmodium parasites and transmitted via infected anopheles mosquitoes. The life cycle involves an asexual replication phase in humans and a sexual phase in mosquitoes. Key factors that influence the spread of malaria include the plasmodium species, environmental conditions, socioeconomic factors, and human behaviors and immunity.

1. EPIDEMIOLOGY
OF MALARIA
DR. MAHESWARI JAIKUMAR.
maheswarijaikumar2103@gmail.com

7. 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 ANOPHELINE
mosquito.

8. • A typical attack comprises three
distinct stages:
• 1. COLD STAGE.
• 2. HOT STAGE.
• 3. SWEATING STAGE.

9. • The clinical features of malaria
vary from mild to severe, and
complicated according o the
species of parasite present,
immunological status of the
patient, intensity of infection
and presence of concomitant
conditions (malnutrition & other
disease).

10. • The febrile paroxysms occur with
definite intermittent periodicity
repeating every third or fourth
day depending upon the species
of the parasite involved.

11. EPIDEMIOLOGICAL
DETERMINANTS

12. AGENT
VECTOR – FEMALE ANOPHELUS MOSQUITO

13. PLASMODIUM- AGENT

14. • Malaria in man is caused by four
distinct species of the malaria
parasite.
• Plasmodium vivax, Plasmodium
falciparum, Plasmodium
malariae & Plasmodium ovale.

15. • The severity of malaria is related
to the species.

16. LIFE CYCLE
• The malaria parasite undergoes
two cycles of development .
• 1. HUMAN CYCLE (ASEXUAL
CYCLE).
• 2. MOSQUITO CYCLE (SEXUAL
CYCLE).

19. • Man is the intermediate host
and mosquito the definitive
host.

20. ASEXUAL CYCLE
• The asexual cycle begins when
an infected mosquito bites a
person and injects sporozoites.

21. • When the sporozoites enters a
person further pathology takes
place in defined phases.
• The definitive phases are as
follows.

22. PHASES IN ASEXUAL
CYCLE
• 1. HEPATIC PHASE.
• 2. ERYTHROCYTIC PHASE.
• 3. GAMETOGENY.

23. HEPATIC PHASE
• The sporozoites dissappear within
60 minutes from peripheral
circulation.
• Many of them are destroyed by
phagocytes but a few reach the
liver.

24. • After 1-2 weeks the sporozoited
develop into HEPATIC
SCHIZONTS.
• The hepatic schizonts eventually
burst releasing a shower of
meroziotes.

25. • Sometimes the intrahepatic
schizonts (which are not burst –
they remain dormant inside the
liver) grow and become pre-
erythrocytic schizogony thus
liberating merozoites into the
blood stream (causing relapse).

26. • Once the parasites enter the
liver they do not reinvade the
liver.
• This is followed by erythrocytic
phase.

27. ERYTROCYTIC PHASE
• May meroziotes are quickly
destroyed.
• But a significant number of them
attach to a specific receptor sites
in RBC.

28. • The merozoites then penetrate
the RBC and pass through the
stages of trophozoites and
schizont.
• The erythrocytic phase ends with
the liberation of merozoites that
infect fresh RBC.

29. • The cycle is repeated over and
over again until it is slowed
down by the immune response.
• The duration of the erythrocytic
phase is constant for each
species.

30. • P falciaprum, P vivax & P. ovale -
48 hours.
• P malariae – 72 hours.

31. GAMETOGENY
• In all Plasmodium species some
erythrocytic forms do not divide
but become male and female
gametocytes.

32. • These are the sexual forms of the
parasites which are infective to
mosquito. (GAMETOCYTES)

33. SEXUAL CYCLE
• The sexual cycle ( sporogony)
begins when the gametocytes
are ingested by the vector
mosquito when feeding on an
infected person.

34. • The gametocytes continue
further development in the
mosquito.
• The first event to take place
inside the stomach of the
mosquito is the exflagellation of
the male gametocyte.

35. • 4-8 thread like filaments called
“macro-gametes” are developed.
• The female gametocyte
undergoes a process of
maturation and becomes a
female gamete of
“MACROGAMETE”.

36. • By a process called chemotaxis,
microgametes are attracted
towards the female gamete and
one of which (microgamete)
causes fertilization of the female
gamete.

37. • A zygote is formed. The zygote is
at first a motionless body, but
within 18-24 hours, it becomes
motile.

38. • This is known as OOKINETE,
which penetrates the stomach
wall of mosquito and develops
into a oocyst on the outer
surface of the stomach.

39. • The oocyst grows rapidly and
develops within its numerous
sporozoites. Into the body cavity
of the mosquito.
• Many of the sporozoites migrate
to the salivary glands of the
mosquito.

40. • Now the mosquito becomes
infective to man.
• The period of time required for
the development of the parasite
from the gametocyte to sporozoite
stage in the body of the mosquito
is about 10-20 days depending
upon favourable conditions.

43. • The conditions include
atmospheric temperature and
humidity.
• This period is also referred to as
EXTRINSIC INCUBATION PERIOD”

44. RESEVOIR OF
INFECTION

45. • A human reservoir is a person
who harbours the sexual forms (
gametocytes).
• A patient can be a carrier of
several plasmodial species at the
same time.

46. • Children are more likely to be
carriers than adults.
• There are certain conditions to
be fulfilled to be in the state of
reservoir.

47. • The person must harbour both
the sexes of the gametocyte in
the blood.
• The gametocytes must be
mature.

48. • The gametocytes must be viable.
• The gametocytes must be
present in sufficient density to
infect mosquitoes.

49. • There must be at least 12
gametocytes per cubic mm of
blood.

50. PERIOD OF
COMMUNICABILITY
• Malaria is communicable as long
as, mature, viable gametocytes
exist in the circulating blood in
sufficient density to infect vector
mosquitoes.

51. • Gametocytes are the most
numerous during the early
stages of the infection when
their density may exceed 1,000
per cubic mm of blood.
• They also tend to occur in waves
in the peripheral blood.

52. RELAPSES
• Vivax & Ovale malaria tend to
relapse more than 3 years after
the patient’s first attack.
• Recurrence of falciparum usually
disappear within 1-2 years.

53. • P. malariae has a tendency to
cause prolonged low-level,
asymptomatic parasitaemia.

54. HOST FACTORS

55. AGE
• Malaria affects all ages.
• Newborn infants have
considerable resistance to
infection due to a high
concentration of foetal
haemoglobin during the first
months of life.

56. GENDER
• Males are more frequently
exposed more than females due
to their outdoor life.
• Females are better clothed than
males.

57. RACE
• Individuals with AS haemoglobin
(single cell trait)have milder
illness.

58. PREGNANCY
• Pregnancy increases the risk of
malaria in women.
• Malaria during pregnancy may
cause intra uterine death in
foetus.It may cause pre mature
labour or abortion

59. SOCIO-ECONOMIC
DEVELOPMENT
• Malaria demonstrated
relationship between health and
socio-economic development.

60. • It is observed that malaria has
disappeared from most
developed countries due to socio
economic development.

61. HOUSING
• Ill ventilated and ill-lighted
provide ideal indoor resting
places for mosquitoes.

62. POPULATION MOBILITY
• Labourers connected with
engineering, irrigation
agricultural and other projects,
migrating nomads are more
disposed to develop malaria.

63. OCCUPATION
• Malaria is predominantly a rural
disease and has direct
connection with agriculture and
related occupation.

64. HUMAN HABITS
• Human habits such as sleeping
out of doors, nomadism,
absence of personal protection
measures increase the risk of
contracting malaria.

65. IMMUNITY
• Epidemic malaria is influenced
by the immune status of the
population.
• Immunity is acquired only after
repeated exposure over several
years.

66. ENVIRONMENTAL
FACTORS