Infectious Diseases Flashcards
What type of organism causes rabies?
RNA rhabdovirus (specifically lyssavirus)
How does rabies result in death?
Causes encephalitis by virus travelling up nerve axons towards CNS in retrograde fashion
What are 4 clinical features of rabies?
- Prodrome: headache, fever, agitation
- Hydrophobia: water-provoked muscle spasms
- Hypersalivation
- Negri bodies: cytoplasmic inclusion bodies in infected neurons
What should be done in the instance of an animal bite in countries at risk of rabies?
- wash wound
- if individual already immunised: 2 further doses of vaccine
- if not previously immunised: give human rabies immunoglobulin (HRIG) + full vaccination course (dose should be administered locally around wound)
What is first line management of syphilis?
IM benzathine penicillin
What are 4 types of clostridia?
- C. perfringens - gas gangrene (myonecrosis)
- C. botulinum - canned foods/honey - flaccid paralysis
- C. difficile - pseudomembranous colitis
- C. tetani - tetanus, spastic paralysis
What type of bacteria are clostridia?
gram positive, obligate anaerobic bacilli
What is C. perfringens?
- produces α-toxin, a lecithinase, causes gas gangrene (myonecrosis) and haemolysis
- features include tender, oedematous skin with haemorrhagic (black) blebs and bullae.
- Crepitus on palpation
Where is C. botulinum classically found?
canned foods and honey
How does C. botulinum produce its effects?
prevents acetylcholine (ACh) release - leads to flaccid paralysis
How does C. tetani produce its effects?
produces exotoxin (tetanospasmin) that prevents the release of glycine from Renshaw cells in the spinal cord, causing spastic paralysis
Which organism is most commonly the cause of malaria in travellers returning to the UK?
Plasmodium falciparum protozoa
What are 6 examples of drugs which are used as malaria prophylaxis?
- atovaquone + proguanil (Malarone)
- chloroquine
- doxycycline
- mefloquine (Lariam)
- Proguanil (Paludrine)
- Proguanil + chloroquine
Which type of malaria prophylaxis is taken weekly? 2 types
- mefloquine (lariam)
- chloroquine
Which type of malaria prophylaxis is contraindicated in epilepsy (2 types)?
- chloroquine
- mefloquine
Which type of malaria prophylaxis is contraindicated in depression?
mefloquine
What is a key side effect of atovaquone + proguanil (malarone)?
GI upset
What is a key side effect of malaria prophylaxis drug chloroquine?
headache
What are 2 key side effects of doxycycline?
- photosensitivity
- oesophagitis
What are 2 key side effects of mefloquine (malaria prophylaxis)?
- dizziness
- neuropsychiatric disturbance
How long after travel should most types of malaria prophylaxis be stopped?
4 weeks (except Malarone - 7 days)
How long before travel should most types of malaria prophylaxis be started?
1 week (Malarone + doxy 1-2 days; mefloquine 2-3 weeks)
Which 2 types of malaria prophylaxis can be used in pregnancy (if travel cannot be avoided)?
- chloroquine
- proguanil - need folate supplementation alongside
What are 2 types of malaria prophylaxis recommended for use in children?
- diethyltoluamide (DEET) 20-50% - to repel mosquitoes (in children >2 months)
- doxycycline - children >12y
How many doses of tetanus-containing vaccine does the childhood vaccination programme give in total?
5
What are 3 groups into which wounds can be classified when decided about tetanus vaccination?
- clean wound - < 6 hours old, non-penetrating, negligible tissue damage
- tetanus prone - puncture-type injuries in contaminated environemnt e.g. garden, foreign bodies, compound fractures, wounds/burns with sepsis, animal bites and scratches
- high-risk tetanus prone - heavy contamination e.g. soil, manure, wounds or burns with extensive devitalised tissue, wounds/burns requiring surgical intervention
In a patient with a wound, what course of action should be taken regarding tetanus vaccination?
- if full course of vaccines with last dose <10 years ago - no vaccine or Ig
- if full course of vaccines with last dose >10 years ago - if tetanus prone, give booster; high-risk: booster +tetanus immunoglobulin
- if vaccination history incomplete / unknown - booster, if tetanus prone / high risk - tetanus immunoglobulin
What is considered the number of tetanus vaccine doses that confers lifelong protection?
5
What causes infectious mononucleosis?
HHV-4: EBV
less frequently CMB and HHV-6
What is the classic triad of symptoms / signs in infectious mononucleosis?
- sore throat
- lymphadenopathy - anterior / posterior triangles of neck
- pyrexia
In addition to the classic triad what are 7 other features of infectious mononucleosis?
- malaise, anorexia, headache
- palatal petechiae
- splenomegaly
- hepatitis, transient ALT rise
- lymphocytosis
- haemolytic anaemia secondary to cold agglutins (IgM)
- maculopapular, pruritic rash when take amoxicillin
How long does it typically take symptoms of infectious mononucleosis to resolve?
2-4 weeks
How is a diagnosis of infectious mononucleosis made?
Monospot test - during 2nd week of illness
When should monospot test be performed during infectious mononucleosis?
2nd week of illness
What is the management of infectious mononucleosis / what advice must be given?
- supportive, analgesia, fluids, avoid alcohol
- avoid contact sports for 4 weeks afterwards - risk of splenic rupture
What is the link with EBV and socioeconomic groups?
- higher rates of seropositivity in lower economic groups
- higher incidence of infectious mononucleosis in higher socioeconomic groups - acquire EBV in adolescence rather than early childhood
How long should a child with mumps be excluded from school?
5 days from onset of swollen glands
What are 7 conditions where children don’t need to be excluded from school?
- conjunctivitis
- fifth disease (Slapped cheek)
- roseola
- infectious mononucleosis
- head lice
- threadworms
- hand, foot and mouth
What is the school exclusion advice for scarlet fever?
24h after commencing antibiotics
What is the school exclusion advice for whooping cough?
2 days after commencing abx or 21 days from onset of symptoms if no abx
What is the school exclusion advice for measles?
4 days from onset of rash
What is the school exclusion advice for rubella?
5 days from onset of rash
What is the school exclusion advice for chickenpox?
all lesions crusted over
What is the school exclusion advice for impetigo?
until lesions crusted and healed, or 48h after commencing abx
What is the school exclusion advice for scabies?
until treated
What is the school exclusion advice for influenza?
until recovered
Which virus most often causes the common cold?
rhinovirus