Public Health Approaches to Malaria

Source: National Library of Medicine

Malaria

• Malaria is a vector borne parasitic disease caused by the genus Plasmodium, affecting over 100 countries of the tropical and subtropical regions of the world.

• Four different Plasmodium species infect humans and cause distinct disease patterns: P. falciparum (malaria tropica), P. vivax (malaria tertiana), P. malariae (malaria tertiana) and P. Ovale (malaria quartana)

• P. falciparum and P. vivax account for 95% of malaria infections. Of these two parasites, P. falciparum is the most deadly one, causing cerebral malaria which, if remain untreated, leads to coma and ultimately death of the patient.

• 40% of the world population live in areas with the risk of malaria.

• Around 300-500 million clinical cases of malaria are reported every year, of which more than a million die of severe and complicated cases of malaria.

• Malaria is known to kill one child every 30 sec, 3000 children per day under the age of 5 years.

• Malaria ranks third among the major infectious diseases in causing deaths after pneumococcal acute respiratory infections and tuberculosis, and accounts for approximately 2.6% of the total disease burden of the world.

• Although malaria has been widely eradicated in many parts of the world, the global number of cases continues to rise. The most important reason for this alarming situation is the rapid spread of malaria parasites that are resistant to antimalarial drugs.

Malaria

Malaria

Malaria parasites are transmitted from one person to another by the female anopheline mosquito.

The males do not transmit the disease as they feed only on plant juices.

There are about 380 species of anopheline mosquito, but only 60 or so are able to transmit the parasite.

Malaria Life Cycle

Mosquito infected with the malaria parasite bites human, passing cells called sporozoites into the human’s bloodstream.

Sporozoites travel to the liver. Each sporozoite undergoes asexual reproduction, in which its nucleus splits to form two new cells, called merozoites.

Merozoites enter the bloodstream and infect red blood cells.

In red blood cells, merozoites grow and divide to produce more merozoites, eventually causing the red blood cells to rupture. Some of the newly released merozoites go on to infect other red blood cells.

Some merozoites develop into sex cells known as male and female gametocytes.

Another mosquito bites the infected human, ingesting the gametocytes.

In the mosquito’s stomach, the gametocytes mature. Male and female gametocytes undergo sexual reproduction, uniting to form a zygote.

The zygote multiplies to form sporozoites, which travel to the mosquito’s salivary glands.

If this mosquito bites another human, the cycle begins again

Malaria Life Cycle

Life Cycle of the Malaria Parasite

History of Malaria• Anophelines have been in Africa for

30 million years!

• Symptoms first described in China in writings from 2700 BC

• Cinchona bark uses in the early 17th century to cure malaria (quinine)

• In 1880, Alphonse Laveran discovers plasmodia in the blood of a patient in Algeria.

• In 1897, Ronald Ross demonstrates the mosquito transmits malaria (India) (Nobel Prize)

The bark of the cinchona (from Bolivia)

Alphonse LaveranSource: Centers for Disease Control and Prevention.

Malaria Basics

• Geographic variability: parasite, vector, transmission, behaviors, impact

• Four species of Plasmodium in humans• Many anopheline species transmit• As yet no vaccine• Parasite resistance to drugs• Some vector resistance to insecticides• Roll Back Malaria partnership• P. falciparum Worldwide, P. vivax LAC/Asia

Malaria Burden • Disease Burden

300-500 million clinical cases per year, ~1B infections?• 80% of cases in

Africa~900,000

deaths/year• >75% African

children 5th in ID deaths

Malaria Burden (continued)

• <20% of malaria cases come to attention of the health system,

• 80% are private care in shops/ pharmacies (resistance…)

• Pregnant women at high risk of dying, low birth weight children

• Children suffer cognitive damage and anemia

• Families spend up to 25% of family income on treatment

• 40 million DALYs lost annually

Resurgence of Malaria • Ecological change

• Population growth

• Marginal and fragile health systems

• Breakdown of health systems/control

• Political upheaval

• Population movement

• Relaxing of control capacity and political will after eradication effort successes

• Marginal populations

Malaria Epidemiology

• Malaria is caused by parasites of the genus Plasmodium.

• There are 4 species of malaria parasites that can affect humans under natural conditions: Plasmodium falciparum, P. vivax, P. ovale, and P. malariae.

• The disease is spread by the female Anopheles mosquito

Source: National Institute of Allergy and Infectious Diseases

Burden in Pregnancy

• 45 million pregnancies annually in endemic areas of Africa– 23 million (50%) in high malaria transmission areas

• 3-15% of mothers suffer severe anemia and 10,000 malaria anemia deaths per year

• Infants: 30% of preventable low birth weight and 75-200,000 infant deaths per year

Malaria in PregnancyMalaria in Pregnancy

morbiditymorbidity anemia anemia fever fever cerebral malaria cerebral malaria hypoglycemia hypoglycemia sepsis sepsismortalitymortality severe disease severe disease hemorrhage hemorrhage

abortionsabortionsstillbirthsstillbirthscongenital congenital infectioninfection

LBWLBWprematurityprematurity

IUGRIUGRmalariamalaria

General General illnessillness

mortalitymortality

MalariaMalariaPregnantPregnant WomenWomen

FetusFetus

NewbornNewborn

Children and Malaria• Malaria accounts for 20% of all

childhood deaths in Africa

• Anemia, low birth-weight, failure to thrive, neurological problems from cerebral malaria

• Over 500,000 African children develop cerebral malaria

• Symptoms include fever, vomiting, and headache, convulsions, coma, or death within 24 hours

• Much of the morbidity & mortality can be prevented with tools currently available

Source: Roll Back Malaria. World Health Organization.

The Malaria Challenge

• Malaria is a disease of poverty & a cause of poverty…

GNPper capita

(1995) $0-70$0-70

$1941-2580$1941-2580

00

33

MalariaIndex

Economic Costs - Malaria• Economic Costs

– Care & Control– Productivity, earnings– Loss of time from work – Hampers economic

development

• One healthy year of life is gained for every $1 to $8 spent on effectively treating malaria cases

Economic Impact of Malaria

• >$3.6B in economic loss in 2000

• 1%-5% of GDP for endemic countries in work loss

• 20%040% of outpatient visits and 10%-15% of admissions…

• Deterrent to trade, business development, tourism, foreign investment

Major Issues & Challenges for Malaria

• Infrastructure and health systems

• Accurate Dx and Rx, surveillance

• Applying combination therapies

• Drug adherence, quality

• Private sector delivery and regulation

• Cost and financing

Malaria Prevention and Control…Malaria Prevention and Control…

Attacking Malaria…• Preventing infection (avoiding bites)

• Preventing disease (using antimalarial drugs prophylactically)

• Antimalarial drugs for pregnant women

• Vector control (source reduction including larval control, indoor residual spraying)

• Insecticide treated bed nets (have been shown to reduce all-cause mortality by 20%)

Key Factors for Malaria Interventions• Prompt & Effective Treatment

– Home management, availability, resistance

• Intermittent Preventive Therapy

– High antenatal attendance rates in Africa

– Primagravidae and HIV+ women

• Insecticide Treated Nets

– Availability

– Targeting those most in need