Infections & Malaria Flashcards
Why are Malaria, Tuberculosis, and HIV often mentioned together?
- 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
What is the incubation period? Characteristics?
= 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
What is the Prodromal period? Characteristics?
= 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
What is the Period of decline? Characteristic?
= 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
What is the Period of convalescence ?
= final stage: microbial replication is fully stopped and the person returns to the pre-illness state.
What are the two primary methods of disease transmission? Expain them
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)
What is an emerging infectious disease?
Emerging infectious diseases are new to a population
What is the infectious period?
time in which person can transmit the disease
What is the case fatality ?
Measure of severity: proportion of people that die after infection
What is the basic reproductive rate?
Average number of secondary cases that occur as the result of one infected individual
What is the secondary attack rate?
proportion of people that gets exposed to the disease and gets ill
Malaria is caused by A, spread by B, and most severe by the species C, D
A) plasmodium parasites
B) bites of infected female mosquitos
C) P. falciparum
D) P. vivax
When do symptoms of malaria occur?
- Appear 10-15 days after infective mosquito bite
What are the first symptoms of Malaria?
First symptoms: fever, headache, chills: mild + difficult to recognize as malaria
Other symptoms:
extreme fatigue, jaundice (yellow/greenish pigmentation), enlarged spleen
After what time can P. falciparum malaria progress to severe illness, often leading to death?
24 hrs
What are malaria symptoms in children?
- Severe aneamia
- Respiratory distress in relation to metabolic acidosis or cerebral malaria
In malaria endemic areas, people may develop partial immunity, allowing X infections to occur.
asymptomatic
How many malaria cases were there worldwide in 2019?
229 million cases worldwide
Who is most at risk for malaria?
- 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
What is the best available treatment for malaria (especially P. falciparum)?
artemisinin-based combination therapy (ACT)
- All cases of suspected malaria are recommended to be confirmed using X (either microscopy or rapid diagnostic test) before administering treatment
parasite-based diagnostic testing
- Treatment solely based on symptoms should ONLY be considered when X
parasitological diagnosis is not possible.
What is preventative treatment for malaria?
Prevention: Insecticide-treated nets for over your bed, indoor spraying, antimalarial medicines
Explain how malaria is transmitted
- Female mosquito bite -> plasmodium in salivary gland (“sporozoid”) injected
- 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. - 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) - 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) - 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.
How is malaria diagnosed?
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)
How is malaria treated?
> 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
