This document discusses malaria transmission and the life cycles of the malaria parasite and mosquito vector. It notes that malaria is transmitted between humans and mosquitoes, with the parasite undergoing development stages in both the liver and blood of humans, and in the gut and salivary glands of mosquitoes. The mosquito life cycle and factors influencing transmission patterns are also summarized.

2.  To appreciate the diversity of malaria as a disease
 To comprehend the life cycle of the parasite and the
vector
 To understand the factors that determine
transmission patterns, both vectorial and human

3.  The four human Plasmodium species
 P. falciparum
 P. vivax
 P. ovale
 P.knowlesi-Recently discovered to infect human though
previously infecting animals only
Morphological Characteristics of Malaria Parasites

4.  Introduction
 Morphology of malaria parasites
 Vector life cycle
 Parasite life cycle
 Factors that determine transmission

5. • 207 million cases reported in 2012 (80% from
Africa)
• 627,000 deaths (90% from Africa)
• <5yrs make up 77% of the deaths
• Causative agent = Plasmodium species
• 4 spp that infect humans
• Transmitted by anopheline mosquitoes

6. Anopheline
mosquitoes
(Vector)
Humans:
Infected
Un -infected
Plasmodium spp

7. • Main malaria vectors in Africa: An. gambiae s.s,
An. arabiensis, An. funestus
• They differ in biologically important
characteristics
– Host preference
– Where and when they bite
– Where they rest
– Breeding site
• These influence transmission of malaria and
methods for control

8. • An. gambiae s.s
• Anthropophilic (feeds exclusively on humans)
• Endophilic (rests indoors)
• Humid climate
• Fresh water breeder
• An. arabiensis
• Exophagic and exophilic
• Opportunistic feeder (anthropophilic & zoophilic)
• survival in hot and arid conditions
• Fresh water breeder

9. • An. funestus
 breeds in natural/artificial permanent and semi-
permanent water bodies with floating or emerging
vegetation
 has late-night biting patterns
 Anthropophilic and endophilic

11.  Trophozoites
 Chromatin
 Cytoplasm
 Vacuole
 Pigment
 Host Cell
 Chromatin – This is the nucleus of the parasite and is
usually round in shape and stains purple/red.
 Cytoplasm - Early stages usually ring shaped, but
varies as it matures and also with species. Usually
stains blue but also varies with age and species of the
parasite.
 Pigment - Coarse brown/black precipitates on
parasite cytoplasm which are by-products of parasite
metabolism. Colour may vary depending on species.
Morphological Characteristics of Malaria Parasites MDCoE2009

12.  Schizonts
 Merozoites
 Pigment
 Cytoplasm
 Formed as a result of simple division of the parasite
nucleus (schizogony).
 Number of merozoites vary between age and species
of the parasite.
 Pigment may be scattered or concentrated
depending on age or species.
Morphological Characteristics of Malaria Parasites MDCoE2009

13.  Gametocytes
 Nucleus
 Pigment
 Cytoplasm
 This is the sexual stage where parasites become
male or female.
 May be banana-shaped or round depending on the
species.
 Size of chromatin may help differentiate between
male and female.
Morphological Characteristics of Malaria Parasites MDCoE2009

15.  Complete metamorphosis
 Egg, larvae, pupae and adult

16.  75-150 eggs on average
 Laid individually on water
surface
 Float by means of an air
chamber
 Hatch after 2-3 days
depending on temp (25-30O C)

17.  Characteristic resting
position, lying parallel to
the water surface.
 Larval development
takes 5 to 7 days.
 Shed their skin four times
L1, L2, L3 and L4
 They use siphon tubes to
breath
 Feed on micro-organisms
and organic matter

18.  Development time: 14-48
hours
 Difficult to control Mobile,
little control over direction
 Non-feeding stage
 Pupal skin splits and the
mosquito emerges as an
adult.

19.  Emerged adult rests on
the surface of the water
for a short time to dry
and all its parts to
harden
 Also, the wings have to
spread out and dry
properly before it can fly
 Females: blood
(animal/man) and plant
juices.
 Male: plant juices
• Female mates once in her
lifetime
• Takes a blood meal required
for development of eggs

20.  Plasmodium transmitted form infected humans
to non-infected humans
 Vector – definitve host
 Human – intermediate host
 Has both extracellular and intracellular stages
in both vector and human
 Stages in the human:
 Exo-erythocytic schizogony (Liver stage)
 Erythrocytic stage (Red blood cell stage)

21. • Haploid sporozoites introduced
in the blood stream
• hepatocyte (liver cells) invasion
• asexual replication forming pre-
erythrocytic schizonts
• Each schizont contains 1000-
10,000 merozoites
• 6-15 days

22. • some sporozoites exhibit
delayed replication (ie,
dormant)
• merozoites produced
months after initial
infection
• only P. vivax and P.
ovale
relapse = hypnozoite
recrudescence = subpatent

23.  Pre-erythrocytic schizont ruptures , merozoites
are released into the blood stream, where they
invade erythrocytes
 Merozoite develops into a ring form
 Ring form undergoes mitotic replication and
becomes a mature schizont
 Schizont contains 16-32 merozoites, ruptures
and realeases the merozoites
 Re-invasion of other RBC

24. erythrocytic schizogony
• 48 hr in Pf, Pv, Po
• 72 hr in Pm
gametocytes
A subset of the erythrocytic parasites multiple sexually to form
male or female gametocytes, the precursor forms of the
sporogonic development in the female Anopheles mosquito

25. Associated with synchrony
of merozoite release
Between paroxysms
temperature is normal and
patient feels well
P. falciparum may not
exhibit classic paroxysms
(continuous fever)
tertian malaria
quartan malaria

26.  The female anopheles mosquito picks up the
gametocytes
 Gametogenesis occurs producing gametocytes
 Male gametocyte exflagellates generating eight
haploid motile gametes
 Male and female gametes fuse forming a
zygote (24hrs)
 Zygote develops into motile ookinetes that
burrow into the midgut
 Ookinetes develop into an oocyst

27.  Inside the oocyst ther are sporozoites
 Oocyst ruputures releasing sporozoites
 Sporozoites move up (through the
hemolymph) to and attach to the salivary
glands

29. Invasive Stages
Merozoite
• erythrocytes
Sporozoite
• salivary glands
• hepatocytes
Ookinete
• epithelium

30. Climatic factors –
 affects breeding sites, larval development, parasite
development e.t.c.
Non-climatic factors
 Human activities
 Human host immune factors
 Socio-economic factors

31.  Vector factors
 survival and longevity
 Genetic factors
The three components must exist together in time and
space for successful transmission

32. Thank you for listening