Mosquitoes and Malaria

What is the main transmitter of malaria?

Anopheles mosquito

Biological and Ecological Characteristics of Anopheles Mosquitoes

• Larval Anopheles have a rudimentary breathing tube

  • Must rest parallel to the water surface

• Adults have their proboscis and body in the same straight line

• Eggs are laid individually as floaters

Global Distribution of Malaria

• Anopheles gambiae is the prominent vector for malaria

  • Different parts of the world have different species of Anopheles

• Malaria was endemic to the US until the 1800s

• In some areas, disease is gone but vectors (capable of transmission) are present

  • Happens when humans are the only reservoirs

Elimination of Malaria in the United States

• Targeted breeding sites to break cycle of transmission

• Program commenced operations in 1947

  • Consisted primarily of DDT application

    • Its use is no longer allowed since it is toxic

    • Applied to interior surfaces of rural homes or entire premises in counties where malaria was reported to have been prevalent in recent years

      • Endophilic & endophagic

  • Drainage, removal of mosquito breeding sites and aerial spraying of insecticide

• (1951) The U.S. was declared free of malaria as a significant public health problem

Malaria Pathogens

1. Plasmodium vivax

2. P. falciparum

3. P. malariae

4. P. ovale

5. P. knowlesi

What is the most lethal malaria pathogen species?

• P. falciparum

Plasmodium vivax

• targets all RBCs (regardless of age)

  • most prominent species

• Protozoan: Apicomplexa

• parasite to red blood cells (RBCs)

Main Form of Malaria Transmission

Anopheles spp.

Other Forms of Malaria Transmission

• Blood transfusion

• Congenital

• Contaminated needles and syringes

What is the incubation period for malaria?

The incubation period in most cases varies from 7 to 30 days

Incubation Periods for Malaria pathogens

Short incubation periods are observed most frequently with P. falciparum and the longer ones with P. malariae

Malaria pathogens in relation to the liver

• P. vivax and P. ovale produce dormant liver-stage parasites

• Liver stages may reactivate and cause disease months after the initial infection

Misdiagnosis or delayed diagnosis for malaria

• Potential for misdiagnosis or delayed diagnosis

• Returned travelers/health care providers 12 months

Uncomplicated malaria

• Typically, people develop uncomplicated Malaria

• Classical but rarely observed malaria attacks that lasts 6-10 hours

  • Consists of: cold stage, hot stage, and sweating stage

Uncomplicated Malaria Attacks

• occur every third day with “tertian” parasites

  • P. falciparum, P. vivax, & P. ovale

• occur every fourth day with the “quartan” parasite

  • P. malariae

Symptoms associated with Uncomplicated Malaria

• fever, chills, sweats, headaches, nausea and vomiting, body aches, general malaise

  • NOTE: in non-endemic areas, they may be attributed to influenza, a cold, or common infections

Physical findings of Uncomplicated Malaria

• Elevated temperatures

• Perspiration, Weakness

• Enlarged spleen

• Mild jaundice

• Enlargement of the liver

• Increased respiratory rate

Diagnosis for Uncomplicated Malaria

• malaria parasites in the blood, usually by microscopy

• Additional laboratory findings may include mild anemia, mild decrease in blood platelets (thrombocytopenia),elevation of bilirubin, and elevation of aminotransferases.

Overview of Severe Malaria

• Can lead to organ failure or abnormalities in the patient’s blood or metabolism

• It’s a medical emergency and should be treated urgently and aggressively

Manifestation of Severe Malaria (Pt. 1)

• Cerebral malaria with abnormal behavior, impairment of consciousness, seizures, coma, or other neurologic abnormalities

• Severe anemia due to hemolysis (destruction of the red blood cells)

• Hemoglobinuria (hemoglobin in the urine) due to hemolysis

Manifestation of Severe Malaria (Pt. 2)

• Acute respiratory distress syndrome (ARDS)

• Abnormalities in blood coagulation

• Low blood pressure caused by cardiovascular collapse

Manifestation of Severe Malaria (Pt. 3)

• Acute kidney injury

• Hyperparasitemia, where more than 5% of the red blood cells are infected by malaria parasites

• Metabolic acidosis (excessive acidity in the blood and tissue fluids), often in association with hypoglycemia

What is ARDS?

• an inflammatory reaction in the lungs that inhibits oxygen exchange, which may occur even after the parasite counts have decreased in response to treatment

Other manifestations of Malaria

• neurologic defects include trouble with movements, palsies, speech difficulties, deafness, and blindness

• recurrent infections with P. falciparum may result in severe anemia or nephrotic syndrome (a chronic, severe kidney disease)

• During pregnancy, malaria can cause severe disease in the mother and may lead to premature delivery or delivery of a low-birth-weight baby

• On rare occasions, P. vivax malaria can cause the rupture of the spleen

Malaria Relapses

• In P. vivax and P. ovale infections, patients may suffer several additional attacks (“relapses”) after months or even years without symptoms

Cause of Malaria Relapses

P. vivax and P. ovale have dormant liver-stage parasites (“hypnozoites”) that may reactivate

Malaria Treatment

• Treatment is complicated and depends on end goal

  • Ex: Eliminate symptoms, prevent relapses or prevent spread

• Presumptive treatment should be reserved for extreme circumstances

• Chloroquine, quinine (compound), Atovaquone, clindamycin, etc.

Factors Considered for Malaria Treatment

• Type of disease: uncomplicated v. severe

• Host: child, pregnant woman

• Drug resistance

• Goal of treatment