Infectious Disease Flashcards
Why can Influenza spread so easily
Surface antigens are able to undergo periodic shift, preventing permanent immunization. Antigenic drift when changes are minor and antigenic shift when major
Pt are contagious 1 day prior to symptoms and 1 week after resolution
Who is at risk for severe influenza or influenza related complications
Age <2 and >65
Pregnancy or 2 weeks post partum
Morbid obesity
Indigenous ethnicity
Chronic care facility residents
Immunosuppression
Chronic conditions (heart, lung, renal, haem, endocrine, neuro)
Mod - severe development delay or intellectual disability
Complications
Bacterial pneumonia (commonly S Aureus)
Sinusitis and OM
Exacerbation of underlying disease
Rapidly progressing pneumonic causing ARDS
Who qualifies for antivirals and what do they do
Neuraminidase inhibitors like Oseltamivir can reduce symptoms by 16.8hrs if commenced within 48hrs of symptoms. May decrease complications and severity but this is controversial UNLESS pt is hospitalized in which case it reduced mortality
To be given to pts hospitalized with severe disease or are high risk for complications
What is Malaria, how is it transmitted and compare the known species
Plasmodium protozoan parasite transmitted by infected female anopheles mosquito in endemic areas (tropics, Sub-Saharan Africa, SE Asia, South America)
There are 5 known types
- Falciparum has highest morbidity and mortality, highest resistances and lacks liver phase and typically develops fevers within 6weeks of travel unless on prophylaxis
- Knowlesi also highly fatal and treated similarly to falciparum
- Vivax and Ovale relapsing malaria due to hypnozoites persisting in liver for many years
- Malariae, as well as vivax and ovale mostly benign prognosis
What is severe malaria
Mortality can approach 100% within a few hours but prompt supportive care can drop to 10-20%
Most commonly due to Falciparum
- deforms RBC membrane which causes adhesions to capillary walls resulting in downstream hypoxia while avoiding splenic sequestration
Can also occur in Knowlesi and rarely vivax
DIAGNOSIS OF SEVERE MALARIA
1 or more of the following
Jaundice
Severe anemia
Resp distress
Hypoglycemia
Acidosis
AKI/oliguria
Impaired consciousness
Parasite count>100 000/uL or >2% red blood cells
Who is at risk for severe malaria and who has immunity
Risk for severe
- Pregnancy
- Asplenia/splenectomy
- Extremes of age
Innate immunity
- Haemoglobinopathies (thalessaemia)
- RBC enzyme deficiny (G6PD)
- RBC surface components (Duffy blood group)
- Sickle cell haemoglobin
Incomplete immunity
- Continually exposed individuals, inoculation rates>10/yr develop partial immunity and reduced risk of severe malaria. Lost if leaves endemic area
What is uncomplicated malaria and how does it present
Symptomatic infection with positive pathological infection without signs of severe malaria
Generally able to tolerate oral therapy
- Cyclic fevers, initially at irregular times throughout the day and then later every other day with vivax, ovale and falciparum and every third day with malaraie
Symptoms
- malaise
- fatigue
- myalgia
- Abdo pain, N/V/D
- Chills and diaphoresis
Exam
Tachycardia/tachypnoea
Splenomegally
Pallor
Mild jaundice
Bloods
Anemia
Thrombocytopenia
Normal or low WCC
Elevated urea and creatinine
Parasitemia
Normal or low WCC
What are the diagnostic tests for malaria
Thick and thin films q12hr for total of 3 sets
- Can be used to both identify species and quantify parasitemia as well as diagnose other infections (babesiosis, trypanosomiasis)
- Diagnostic errors in low density parasitemia 10-100/microL or where majority is sequestered (placenta in pregnancy)
- Labor intensive and requires substantial training and expertise
- Knowlesi (potentially lethal) and Malaraie (generally benign prognosis) are nearly indistinguishable
Rapid Diagnostic Tests for Malaria Parasite antigens
- No laboratory infrastructure or extensive training needed
- Available within 15-20minutes
- Qualitative but not quantitative re parasite density
- Can be falsely negative in falciparum parasites with pfhrp2/3 gene deletions (HRP2 for falciparum, pLDH and Aldolase panspecies)
Molecular testing - PCR
- Highest sensitivity and specificty and gold standard in efficacy studies for antimalarial drugs/vaccines/diagnostic tests
- Recommended if Knowlesi is suspected
- Highest sensitivity in pregnancy
How is uncomplicated malaria managed
Artemether+lumefantrine 20+120mg with fatty food or full fat milk for 6 doses total over 60hrs (4 tables if >34kg at 0,8,24,36,48,60 hrs)
+
Primaquine (Only when G6PD has been excluded, >6 months and no pregnancy), dose and length on species
Falciparum: single dose of 15mg (0.25mg/kg) to prevent human mosquito transmission
Vivax and Ovale used to eliminate dormant liver hypnozoites and prevent relapse
Vivax: 15mg (0.25mgkg) daily for 14 days
Ovale: 30mg (0.5mg/kg) daily for 14 days or total 6mg/kg reached if >70kg
If in the first trimester of pregnancy can use
Atovaquone+proguanil 3 tabs for 3 days (cannot be used if has previously had prophylaxis)
OR
Quinine sulfate 600mg and Clindamycin 450mg TDS for 7 days
Monitor parasite count daily until negative
FBC and malaria microscopy at 7 and 28days for recrudescence
What is the management of severe malaria
Artesunate 2.4mg/kg on admission, 12hrs, 24hrs then daily (can be IM)
OR
Quinine loading 20mg/kg over 4hrs, then 10mg/kg over 4hrs every 8hrs
(May need both if travelling to Greater Mekong Subregion (thialand, Vietnam, Cambodia, Laos, Myanmur) due to rising resistances)
Ceftriaxone 2g daily for 2 days due to high prevalence of bacteremia
Paracetamol 1g QID for 3 days to reduce risk of hemolytic acute kidney injury
As needed add on
Blood and blood products
Glucose
Dialysis
Monitor parasite count twice daily until clinically stable then daily until negative
Switch to oral treatment + primaquine when pt clinically improved and tolerating oral therapy
Risk of delayed hemolysis from artemisinin and recrudescence of malaria parasites, FBC and malaria microscopy at 7, 14, 21 and 28days after oral therapy
What is cerebral malaria, who is at risk and what are its complications
Encephalopathy presents as impaired consciousness, delirium and or seizures.
Focal defits are unusaul
RISKS
- Extremes of age
- Pregnancy
- Splenectomy/asplenia
- Poor nutrional status
- Host genetic susceptibility
DIAGNOSED
- Clinically
- Retinopathy with Retinal hemorrhages, discrete spots of retinal opacification
Complications
- Cerebral edema and elevated intracranial pressure
- Lasting deficits such as hemiplegia, cerebral palsy, cortical blindness, deafness, epilepsy, language deficit and cognitive impairment (more common in children and severe signs like hypoglycemia, severe anemia, acidosis, repeated seizures, coma)
What is the life cycle of malaria
Malaria prophylaxis
Vector avoidance
- Insect repellent and insecticide products (lemon eucalyptus oil only proven natural repellent)
- Light coloured trousers nd long sleeved shirt in the evening
- Sleeping in screened accomodation or using mosquito nets
- Avoiding outside activity between dusk and dawn
- Avoiding perfumes and aftershaves
Chemoprophylaxis - no effect on primary liver stage and need to continue for period of time
Atovaquone+progaunil 1 daily 2 days before entering and 7 days after leaving
OR
Doxycycline 100mg daily 2 days before entering and for 4 weeks after leaving
