Infections & Malaria

Question 1

Why are Malaria, Tuberculosis, and HIV often mentioned together?

Answer 1

• High burden of infection contributes to national and individual poverty, and these diseases share common risk factors
• Third on list of nine main targets of sustainable development goal for health
• In top 10 infections worldwide

Question 2

What is the incubation period? Characteristics?

Answer 2

= period between infection and the first signs of a disease.

• Symptom-less stage
• Microbes multiply inside of our body
• Can spread to others
• Length is highly variable
• Dependent only microorganism + immune system

Question 3

What is the Prodromal period? Characteristics?

Answer 3

= short stage of disease development, person begins to feel they are getting sick

• Progresses into period of illness
• Typical signs and symptoms associated with the disease
• Most easily transmit a communicable disease in this stage

Question 4

What is the Period of decline? Characteristic?

Answer 4

= stage of disease development where the immune system begins to bring microbial replication under control

• Lessening of clinical signs and symptoms associated with the disease

Question 5

What is the Period of convalescence ?

Answer 5

= final stage: microbial replication is fully stopped and the person returns to the pre-illness state.

Question 6

What are the two primary methods of disease transmission? Expain them

Answer 6

horizontal and vertical

Horizontal: the spread of a pathogen, or disease-causing entity, via direct or
indirect contact between individuals, animals (zoonotic disease), or other organisms (insects, vector-
borne)

Vertical: infectious agent was spread from a parent
to child, and that the infection may have occurred before, during, or shortly after birth (e.g. HIV can be spread this way)

Question 7

What is an emerging infectious disease?

Answer 7

Emerging infectious diseases are new to a population

Question 8

What is the infectious period?

Answer 8

time in which person can transmit the disease

Question 9

What is the case fatality ?

Answer 9

Measure of severity: proportion of people that die after infection

Question 10

What is the basic reproductive rate?

Answer 10

Average number of secondary cases that occur as the result of one infected individual

Question 11

What is the secondary attack rate?

Answer 11

proportion of people that gets exposed to the disease and gets ill

Question 12

Malaria is caused by A, spread by B, and most severe by the species C, D

Answer 12

A) plasmodium parasites
B) bites of infected female mosquitos
C) P. falciparum
D) P. vivax

Question 13

When do symptoms of malaria occur?

Answer 13

• Appear 10-15 days after infective mosquito bite

Question 14

What are the first symptoms of Malaria?

Answer 14

First symptoms: fever, headache, chills: mild + difficult to recognize as malaria

Other symptoms:

extreme fatigue, jaundice (yellow/greenish pigmentation), enlarged spleen

Question 15

After what time can P. falciparum malaria progress to severe illness, often leading to death?

Answer 15

24 hrs

Question 16

What are malaria symptoms in children?

Answer 16

• Severe aneamia
• Respiratory distress in relation to metabolic acidosis or cerebral malaria

Question 17

In malaria endemic areas, people may develop partial immunity, allowing X infections to occur.

Answer 17

asymptomatic

Question 18

How many malaria cases were there worldwide in 2019?

Answer 18

229 million cases worldwide

Question 19

Who is most at risk for malaria?

Answer 19

• Mostly sub-saharan Africa
• South-East Asia, Eastern Mediterranean, Western Pacific, and the Americas also at risk
• Children <5
• Pregnant women
• Patients with HIV/AIDS
• Non-immune immigrants
• Mobile populations
• Travellers

Question 20

What is the best available treatment for malaria (especially P. falciparum)?

Answer 20

artemisinin-based combination therapy (ACT)

Question 21

• All cases of suspected malaria are recommended to be confirmed using X (either microscopy or rapid diagnostic test) before administering treatment

Answer 21

parasite-based diagnostic testing

Question 22

• Treatment solely based on symptoms should ONLY be considered when X

Answer 22

parasitological diagnosis is not possible.

Question 23

What is preventative treatment for malaria?

Answer 23

Prevention: Insecticide-treated nets for over your bed, indoor spraying, antimalarial medicines

Question 24

Explain how malaria is transmitted

Answer 24

1. Female mosquito bite -> plasmodium in salivary gland (“sporozoid”) injected
2. reach the liver + asexual reproduction, maturation into “merozoites”.
   –> This period of all of these species is calles the ’exoerythrocytic phase’, it is not in red blood cells and generally asymptomatic.
3. Merozoites from liver -> invade red blood cells -> asexual reproduction -> red blood cell bursts
   –>This phase = erythrocytic phase (inside red blood cell, generally lasts 2-3 days)
4. Gametogony: give rise to gametocytes -> get sucked up by female mosquito -> zygote
   mosquito -> reach gut -> fuse together to form a zygote
   -> This phase = sporogony (sexual reproduction)
5. Zygote becomes an Ookinete -> oocyst -> ruptures, releasing thousands of sporozoites that locate themselves into the salivary gland.

Note: step 2: Other species don’t divide and ‘snooze’ for a period of months to years.

Question 25

How is malaria diagnosed?

Answer 25

Thick blood smear: locates parasites sitting in red blood cells
Thin blood smear: directly identifies the plasmodium species
Other signs: low platelet count, elevated lactate dehydrogenase, anemia (low RBS)

Question 26

How is malaria treated?

Answer 26

> Treatment: suppressive treatment of chemoprophylaxis: kills sporozoites before they infect hepatocytes (liver cells) (usually given to travellers).
therapeutic treatment aimed at eliminating merozoites in the eryhrocytic phase (active infection)
Medication depends on: severity, age, pregnancy, local malaria resistance pattern, plasmodium species
gametocidal treatment: aimed at killing gametocytes, prevents spread of disease & resistant forms
radical treatment: aimed at killing hypnozoites in the liver