this lecture has focus on definition,history of malaria,causative agents,life cycle,mode of transmission,epidemeolog,susceptibility,incubation period ,prevention and control

1. Malaria
Prepared by
Ali Awas Third Year Medical Student

2. Definition
-Malaria:
an acute infectious disease of the blood
is a potentially life-threatening disease caused
by infection with Plasmodium protozoa.

3. History Of Malaria
-Malaria has infected humans for over 50,000
years.
-first recorded in 2700 BC in China.
-originates from Medieval Italian:
mala aria — "bad air";
-was formerly called ague or marsh fever due
to its association with swamps and marshland

4. Causative agent
-Malaria in human is caused by one of the five
species of the porotozoal genus
-Plasmodium falciparum(the deadliest) ,
-Plasmodium vivax (the most common 80%),
-Plasmodium. ovale,
- Plasmodium malariae
-Simian(monkey) parasite,Plasmodium
knowles.

5. Life Cycle
The malaria parasite life cycle involves two hosts. During a blood meal, a malaria-
infected female Anopheles mosquito inoculates sporozoites into the human host .
Sporozoites infect liver cells and mature into schizonts , which rupture and
release merozoites . (Of note, in P. vivax and P. ovale a dormant stage
[hypnozoites] can persist in the liver and cause relapses by invading the
bloodstream weeks, or even years later.) After this initial replication in the liver
(exo-erythrocytic schizogony ), the parasites undergo asexual multiplication in the
erythrocytes (erythrocytic schizogony ). Merozoites infect red blood cells . The
ring stage trophozoites mature into schizonts, which rupture releasing merozoites
. Some parasites differentiate into sexual erythrocytic stages (gametocytes) .
Blood stage parasites are responsible for the clinical manifestationsof the
disease
The gametocytes, male (microgametocytes) and female (macrogametocytes), are
ingested by an Anopheles mosquito during a blood meal . The parasites’
multiplication in the mosquito is known as the sporogonic cycle . While in the
mosquito's stomach, the microgametes penetrate the macrogametes generating
zygotes . The zygotes in turn become motile and elongated (ookinetes) which
invade the midgut wall of the mosquito where they develop into oocysts . The
oocysts grow, rupture, and release sporozoites , which make their way to the
mosquito's salivary glands. Inoculation of the sporozoites into a new human host
perpetuates the malaria life cycle.

8. This picture just show two infected RBCs. We can clearly see a lot of parasites in the infected cells. And they looks very different
from the normal cell. there are 1 million infected red cells in every mili-liter blood in p. falciparum infected patients. How can you
imagine that?

9. Occurrence in Yemen
-Malarial infection: is the most prevalent communicable disease in
Yemen, with 81% of the country’s landmass classified as endemic
malaria(WHO, 2010).
- P. falciparum : is the predominant species in Yemen where it is
responsible for more than 90% of the malaria cases, with only
minimal cases caused by P. vivax .
-Malaria persists: as a major health problem in the Hajjah
governorate especially Tehama region.

10. Malaria Epidemiological Situation in Yemen:
• 60% of population is at risk of malaria
• Annual malaria cases is estimated to
be 700,000 with0.9% mortality
• Malaria is classified as Afro-tropical
• Predominant parasite is Pl. falciparum(90–95%)

12. Occurrence in Middle East
Approximately all the countries in the middle
East region are at risk of malaria,
except for Egypt, UAE and Jordan. The disease
often affiliates travelers to most of the
countries of the Middle East.

14. Occurrence In The world
-The WHO estimates that in 2015 there were 214 million new cases of malaria
resulting in 438,000 deaths. The majority of cases (65%) occur in children under 15
years old About 125 million pregnant women are at risk of infection each year; in
Sub-Saharan Africa, maternal malaria is associated with up to 200,000 estimated
infant deaths yearly. There are about 10,000 malaria cases per year in Western
Europe, and 1300–1500 in the United States. About 900 people died from the disease
in Europe between 1993 and 2003 .Both the global incidence of disease and resulting
mortality have declined in recent years. According to the WHO and UNICEF, deaths
attributable to malaria in 2015 were reduced by 60% from a 2000 estimate of
985,000, largely due to the widespread use of insecticide-treated nets and
artemisinin-based combination therapies Two thirds of cases occuring in sub-sahran.
-Malaria is prevalent in tropical and subtropical regions because of rainfall, consistent
high temperatures and high humidity, along with stagnant waters in which mosquito
larvae readily mature, providing them with the environment they need for
continuous breeding. In drier areas, outbreaks of malaria have been predicted with
reasonable accuracy by mapping rainfall. Malaria is more common in rural areas than
in cities.

16. Mode Of Transmission
-It is transmitted mainly by the bite
of female anopheline mosquitoes which
transnmited from the mosquito's saliva into
a person's blood
-There are more than 400 different species
of Anopheles mosquito; around 30 are
malaria vectors of major importance. All of
the important vector species bite between
dusk and dawn. The intensity of
transmission depends on factors related to
the parasite, the vector, the human host,
and the environment
An Anopheles stephensi
mosquito shortly after
obtaining blood from a
human (the droplet of
blood is expelled as a
surplus)

18. Other modes of transmission
1-Induced malaria
A-Blood transfusion (Transfusion malaria):
Is a potentially important mode of transmission, at least in parts of the
world in which screening of bank blood may not be as assiduous as it is in the United States.
B-Needle stick injury
Accidental transmission can occur among drug addicts who share syringes and needles.
2. Mother to the growing fetus (Congenital malaria)
Intrauterine transmission of infection from mother to child is well documented. Placenta
becomes heavily infested with the parasites. Congenital malaria is more common in first
pregnancy, among non – immune populations.
3-cryptic malaria –where route cannot be stablished after through investigation

19. Reservoir for Plasmodium
-Human is the only important reservoir for malaria .
-Animal Reservoirs:
*A certain species of malaria called P. knowlesi has recently been
recognized to be a cause of significant numbers of human
infections.
*P. knowlesi is a species that naturally infects macaques(type of
monkey) living in Southeast Asia.
*Humans living in close proximity to populations of these
macaques may be at risk of infection with this zoonotic parasite.

20. Incubation period
*8-25 days in P. falciparum
*8-25 days in P. vivax and P.ovale.
*15-30 days in P. malariae infections.

21. Period of communicability
-As long as gametocytes remain in the blood, the person
is infective.
-In apparent infections are harbored for long periods depending
upon the species of the parasite and the treatment given.
-Untreated or inadequately treated patients may be a source of
mosquito infection:
for more than 3 years in P. malaria,
1 to 2 years in vivax
to a maximum 1 year in falciparum infections.
-Stored blood remains infective only for 16 days

22. Susceptibility and resistance to malaria
People travelling to malarious areas are at risk:
.
B-The development of resistance to drugs poses one of the greatest threats to malaria control and results in increased
malaria morbidity and mortality. Resistance to currently available antimalarial drugs has been confirmed in only two of the
four human malaria parasite species, Plasmodium falciparum and P. vivax
*Drug-resistant P. falciparum
Chloroquine-resistant P. falciparum first developed independently in three to four areas in Southeast Asia, Oceania, and
South America in the late 1950s and early 1960s. Since then, chloroquine resistance has spread to nearly all areas of the
world where falciparum malaria is transmitted.
P. falciparum has also developed resistance to nearly all of the other currently available antimalarial drugs, such as
sulfadoxine/ pyrimethamine, mefloquine, halofantrine, and quinine. Although resistance to these drugs tends to be much
less widespread geographically, in some areas of the world, the impact of multi-drug resistant malaria can be extensive.
Most recently, a low-grade resistance to artemisinin-based drugs has emerged in parts of Southeast Asia.
*Drug-resistant P. vivax
Chloroquine-resistant P. vivax malaria was first identified in 1989 among Australians living in or traveling to Papua New
Guinea. P. vivax resistance to chloroquine has also now been identified in Southeast Asia, on the Indian subcontinent, and
in South America. Vivax malaria parasites, particularly from Oceania, show greater resistance to primaquine than P. vivax
isolates from other regions of the world.

23. • Susceptibility
– All susceptible
– Travelers and foreigner
– Children, pregnant women
– Short immunity, without cross immunity.

24. Genetic resistance to malaria

26. What are the signs and symptoms of
malaria?
The clinical features of malaria are non-specific
diagnosis must be suspected in anyone and the
returning from an endemic area who has
features of infection.

27. P. falciparum infection
-This is the most dangerous of the malarias and patients are either ‘killed or cured.
-The onset is often insidious, with malaise, headache and vomiting
- Cough and mild diarrhea are also common
-The fever has no particular pattern. Jaundice is common due to hemolysis
and hepatic dysfunction.
- The liver and spleen enlarge and may become tender.
-Anemia develops rapidly, as does thrombocytopenia.
-A patient with falciparum malaria, apparently not seriously ill , may rapidly develop
dangerous complications such as Cerebral malaria is manifested by confusion
, seizures or coma, usually without localizing signs.
-Children die rapidly without any special symptoms other than fever

28. P. vivax and P. ovale infection
-In many cases, the illness starts with several days of
continued fever before the development of classical
bouts of fever on alternate days. Fever starts with a rigor.
The patient feels cold and the temperature rises to about
40°C.
-After half an hour to an hour, the hot or flush phase begins.
-It lasts several hours and gives way to profuse perspiration
and a gradual fall in temperature.
-The cycle is repeated 48 hours later. Gradually, the
spleen and liver enlarge and may become tender.
Anemia develops slowly.

29. P. malariae infection
-This is usually associated with mild symptoms and
bouts of fever every third day
-Parasitemia may persist for many years , with the
occasional recrudescence off ever
or without producing any symptoms
malaria infection causes-Chronic P.
glomerulonephritis and long term nephrotic syndrome
in children.

31. Prevention
-Control the source of transmission
-Cut off the route of transmission
-Protection of susceptible population

32. Prevention Source of
transmission

33. Electronic Mosquito Repellents
-Are not effective

34. Prevention Route of transmission

35. InescticIed-treated bed nets(ITNS)

36. Protection of susceptible population
• Active prophylaxis
– Vaccine
• Under development
• Passive prophylaxis
– Chemoprophylxis
• Chloroquine (sensitive, pregnant women or
children)
• Mefloquine, Doxycycline, Pyrimethamine.

37. The picture shows the link can be explored to be the targets of vaccine.

41. References
-Davidson’s Principles & Practice of Medicine,
22nd edition, 2014
-WHO guideline for treatment of malaria ,3rd
edition,2015
-Mahajan anf Gupta Texstbook of preventive and social
medicine ,Fourth Edition
-Center for Disease control and Prevention
Microbiology (Lippincott Illustrated Reviews Series)3rd Edition