EPIDEMIOLOGY OF MALARIA

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