Infectious diseases

Question 1

How is Lyme disease transmitted?

Answer 1

Vector transmission

Question 2

What type of pathogen causes Lyme disease?

Answer 2

Bacteria - Borrelia Burgdorferi (a spirochete - spiral shaped bacterium)

Question 3

What is the vector that transmits Lyme disease?

Answer 3

Ixodes tick (hard ticks) in wooded areas

Question 4

Which organisms are reservoirs of Lyme disease?

Answer 4

Birds and deer

Question 5

How many clinical stages of Lyme disease are there?

Answer 5

3

Question 6

What are the 3 clinical stages of Lyme disease?

Answer 6

1) Localised disease
2) Early disseminated diseases
3) Late disseminated disease

Question 7

What are the clinical features of localised Lyme disease (stage 1)?

Answer 7

1) Tick bite
2) Flu-like symptoms
3) Regional lymphadenopathy
4) Erythema chronicum migrans (bull’s eye rash)
5) Borrelia lymphocytoma = blue patch on earlobe, nipple, scrotum

Question 8

What are the clinical features of early disseminated Lyme disease (stage 2)?

Answer 8

1) Flu-like symptoms
2) Neuroborreliosis - facial or cranial nerve palsies, peripheral mononeuritis, encephalitis
3) Cardiovascular - myocarditis, pericarditis, arrhythmias
4) Painful arthritis

Question 9

What are the clinical features of late disseminated Lyme disease (stage 3)?

Answer 9

1) Arthritis
2) Late neurological disorders - polyneuropathy, dementia, psychosis, chronic encephalomyelitis
3) Acrodermatitis chronic atrophicans (blue-red discolouration and swelling at extensor surfaces)

Question 10

How do you diagnose Lyme disease?

Answer 10

1) If early disease with classical erythema chronicum migrans, diagnosis can be made clinically
2) Serology - if early or late disseminated disease
3) Typically perform enzyme immunoassay and Western blot for early and late disease, but they can be negative
4) If negative initially but symptoms persist, retest 3–4 weeks later
5) If the patient has arthritis, a synovial fluid sample can be obtained for PCR Borrelia DNA testing

Question 11

How do you manage Lyme disease?

Answer 11

1) Fully remove tick
2) Doxycycline PO 2-3 weeks (second line = PO amoxicillin, cefuroxime, IV ceftriaxone)
3) Complicated infection or CNS/CV manifestations - IV ceftriaxone

Question 12

What type of disease is malaria?

Answer 12

Zoonosis (transmitted from animals to humans) + notifiable disease

Question 13

What are the 4 types of malaria parasite?

Answer 13

1) Plasmodium falciparum
2) P. vivax
3) P. ovale
4) P. malariae

Question 14

How does malaria present?

Answer 14

History of TRAVEL
1) Intermittent fever
2) Sweats/chills
3) Hepato/splenomegaly
4) General malaise/lethargy/fatigue
5) Anorexia
6) GI disturbance
7) Myalgia
8) Arthralgia
9) Sore throat
10) Cough
11) Lower respiratory tract symptoms
12) Confusion
13) Headache

Question 15

What are the potential complications of malaria?

Answer 15

1) Cerebral malaria
2) Renal impairment
3) Acidosis
4) Hypoglycaemia
5) ARDS
6) Severe anaemia
7) Shock
8) Sepsis
9) Haemoglobinuria
10) Parasitaemia
11) Spontaneous bleeding/DIC

Question 16

How do you diagnose malaria?

Answer 16

1) Thick & thin blood films (gold standard)
2) Antigen detection test

Question 17

How do you manage malaria?

Answer 17

1) Hospital admission - medical emergency
2) Antimalarials - artesunate, quinine, chloroquine, doxycycline

Question 18

What is the causative organism in mono?

Answer 18

Epstein-Barr virus

Question 19

What condition is caused by Epstein-Barr Virus (EBV)?

Answer 19

Infectious mononucleosis/glandular fever/kissing disease

Question 20

In which patients is EBV common?

Answer 20

Young adults in developed settings

Question 21

How does EBV present?

Answer 21

1) Fever
2) Malaise
3) Transient macular rash
4) Cervical lymphadenopathy
5) Mild hepatosplenomegaly

Question 22

What is a potential complication of EBV?

Answer 22

Chronic fatigue syndrome/myalgic encephalomyelitis

Question 23

What investigations do you do for EBV?

Answer 23

1) FBC
2) Monospot test
3) EBV serology
4) Abdominal ultrasound

Question 24

What would you see on FBC in EBV?

Answer 24

Raised lymphocytes

Question 25

How is the monospot test carried out?

Answer 25

1) Used to diagnose EBV
2) Heterophile antibody
3) Performed during 2nd week of illness
4) Negative test = repeat testing in 5-7 days

Question 26

When is EBV serology testing used?

Answer 26

1) Patient < 12 years
2) Immunocompromised
3) Monospot is persistently negative but there is high clinical suspicion

Question 27

What might you see on abdo US in EBV?

Answer 27

Hepatosplenomegaly

Question 28

How do you manage EBV?

Answer 28

1) Conservative - self-limiting, resolution within 2-4 weeks
2) Analgesia
3) Avoid alcohol
4) Avoid ampicillin/amoxicillin - can cause itchy maculopapular rash
5) Avoid contact sports for at least 3 weeks - high risk of splenic trauma/rupture

Question 29

Which medication do you want to avoid in EBV and why?

Answer 29

Ampicillin and amoxicillin - can cause itchy maculopapular rash (also avoid alcohol)

Question 30

What activity do you need to avoid in EBV and why?

Answer 30

Contact sports - high risk of splenic trauma/rupture

Question 31

What is the causative agent of typhoid/typhoid fever)

Answer 31

Salmonella typhi (bacteria)

Question 32

How long do symptoms begin after exposure to Salmonella typhi?

Answer 32

6-30 days

Question 33

How is typhoid spread?

Answer 33

By eating or drinking food or water contaminated with the faeces of a person infected with Salmonella typhi

Question 34

What are the risk factors for typhoid?

Answer 34

1) Poor sanitation and hygiene
2) Travelling in developing countries

Question 35

How does typhoid fever present?

Answer 35

1) Gradual onset of a high fever over several days
2) Skin rash with rose coloured spots
3) Weakness
4) Abdominal pain
5) Constipation
6) Headaches
7) Vomiting (not usually severe) ± diarrhoea
8) Confusion - if severe
9) Epistaxis

Question 36

What is the key dermatological sign of typhoid?

Answer 36

Rash with rose coloured spots

Question 37

How long do symptoms of typhoid last without treatment?

Answer 37

Weeks or months

Question 38

How do you diagnose typhoid?

Answer 38

Isolation of S. typhi highest in first week
1) Bone marrow culture - most sensitive source
2) Blood culture - 80% positivity if two culture taken
3) Stool cultures
4) Widal test (for Abs against Salmonella antigens) - not v good

Question 39

What is first line antibiotic management for typhoid?

Answer 39

Ciprofloxacin (empirical)