Infectious Disease 🦠 Flashcards by Cuba Parris

What is malaria?

Malaria is an infectious disease caused by protozoa of the Plasmodium family

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What are the species of Plasmodium known to cause malaria?

Plasmodium falciparum
Plasmodium vivax
Plasmodium ovale
Plasmodium malariae
Plasmodium knowlesi

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What is the pathophysiology of malaria?

Malaria is spread by mosquitoes - when a mosquito sucks up infected blood, parasites reproduce in the gut, producing sporozites (malaria spores)

The sporozites are injected into a person’s blood, where they travel to the liver.

The malaria parasites mature into merozoites, which enter the blood and infect red blood cells, causing rupture, and haemolytic anaemia

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How often does rupture and release of merozoites occur in malaria?

For P. vivax and P. ovale:
- Rupture and release of merozoites occurs every 48 hours

For P. falciparum:
- More frequent or irregular fever spikes

For P. malariae
- Spikes every 72 hours

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What is tertian malaria?

Malaria where the patient has a fever every other day (every 48 hours), due to rupture and release of merozoites every 48 hours

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What are the preventative measures that can be taken against malaria?

Avoiding outdoor activity after sunset
Insect repellants
Wearing long sleeved clothing and trousers
Insecticide-treated bed nets

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What medications can be used for malaria prophylaxis?

Chloroquine
Atovaquone/Proguanil
Doxycycline
Mefloquine

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What is the presentation of malaria?

Fever (up to 41 degrees)
Sweats and rigors
Myalgia
Headache
Nausea
Vomiting
Abdominal pain
Anorexia
Diarrhoea

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What are the signs of malaria on examination?

Pallor due to anaemia
Hepatosplenomegaly
Jaundice

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What investigation is diagnostic of malaria?

Malaria blood film
- Three negative samples over three consecutive days are needed to exclude malaria as a diagnosis

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What other investigations may be useful in the diagnosis of malaria?

Rapid diagnostic test (RDTs)
FBC - anaemia
Clotting screen - long PTT
U&Es
LFTs - unconjugated bilirubin

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What is the first line management of Plasmodium falciparum?

Oral chloroquine or hydroxychloroquine

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What is the second line management for Plasmodium falciparum?

If it is chloroquine resistant:
- Oral artemether/lumefantrine

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What is the first line management of severe Plasmodium falciparum?

IV artesunate

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What is the second line management of severe plasmodium falciparum?

IV artemether

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What is the management of non-falciparum species of malaria?

First line - oral chloroquine or hydroxychloroquine
Second line - oral primaquine

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What is the most common and severe cause of malaria?

Plasmodium falciparum

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What are the complications of P. falciparum malaria?

Cerebral malaria
Seizures
Reduced consciousness
AKI
Pulmonary oedema
DIC
Severe haemolytic anaemia
Multi-organ failure

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What are the causes of enteric fever?

Salmonella typhi (typhoid fever)
Salmonella paratyphi (paratyphoid fever)

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Where are the highest incidence rates of typhoid?

South Asia
Southeast Asia
Sub-saharan Africa

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What is the presentation of typhoid?

Fever
Abdominal pain
Diarrhoea or constipation
Headaches
Vomiting
Rash with rose-coloured spots
Confusion

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What investigations are primarily used in the diagnosis of typhoid?

Blood culture
Stool culture

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What is the gold standard investigation for diagnosis of typhoid?

Bone marrow aspirate

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What is the management of typhoid?

IV ceftriaxone
PO azithromycin

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What are the complications of typhoid?

Osteomyelitis GI bleeding GI perforation Meningitis

What is the aetiology of dengue fever?

Dengue is an RNA virus - flavivirus, transmitted by mosquitoes

What is the clinical presentation of dengue fever?

Fever Headache - retro-orbital Myalgia Bone pain Pleuritic pain Facial flushing Maculopapular rash Mucosal bleeding

What is dengue shock syndrome?

Triad of tachycardia, hypotension and narrow pulse pressure, seen in severe dengue

What is the incubation time of dengue fever?

1 week post exposure

What blood results would be seen in dengue fever?

Leukopenia Thrombocytopenia Raised aminotransferases

What are the diagnostic investigations for dengue?

Dengue serology NAAT resting for viral RNA NS1 antigen test

What is the management of dengue fever?

Supportive - Fluid resuscitation - Analgesia - Blood transfusion

What is the epidemiology of infectious mononucleosis?

Infectious mononucleosis is mostly seen among young adults in developed countries

What is the cause of infectious mononucleosis?

Epstein-Barr Virus (EBV)

What is the presentation of infectious mononucleosis?

Triad of: - Sore throat - Lymphadenopathy - Pyrexia Malaise Headache Splenomegaly Hepatitis Macular rash

Where does lymphadenopathy occur in infectious mononucleosis?

Anterior and posterior triangles of the neck

What are the differentials of infectious mononucleosis?

Streptococcal pharyngitis Influenza HIV seroconversion Cytomegalovirus

What investigations are useful in the diagnosis of infectious mononucleosis?

Full blood count Monospot test EBV viral serology Abdominal ultrasound - assess for splenomegaly HIV testing (rule out)

When should the monospot test be performed?

Week 2 of illness

What is the management of EBV?

Rest Fluids Avoid alcohol Analgesia

What advice should be given to patients with infectious mononucleosis?

Avoid contact sports for 4 weeks, due to the risk of splenic rupture

What antibiotics should be avoided in patients with EBV?

Ampicillin Amoxicillin

What are the complications of EBV?

Haemophagocytic lymphohistiocytosis Aplastic anaemia Acute liver failure Upper airway obstruction

How long does infectious mononucleosis typically last?

2-4 weeks

What is the cause of diphtheria?

Corynebacterium diphtheriae

What is the presentation of diphtheria?

Sore throat Grey coating on the tonsils Bulky cervical lymphadenopathy Neuritis Heart block

What investigation is diagnostic of diphtheria?

Throat swab and culture

What medium is used to culture diphtheria?

Tellurite agar or Loeffler's media

What is the management of diphtheria?

IM penicillin Diphtheria antitoxin

What are the common causes of viral gastroenteritis?

Rotavirus Norovirus

What bacteria commonly cause gastroenteritis?

E. coli Campylobacter jejuni Shigella Salmonella Bacillus cereus Yersinia enterocolitica Staphyloccocus

What bacteria is most associated with traveller's diarrhoea?

Campylobacter

What bacteria is most associated with raw eggs or polutry?

Salmonella

What pathogen is most associated with the small intestines of animals?

Giardia

What bacteria is most associated with undercooked pork?

Yersinia

What types of gastroenteritis can lead to haemolytic uraemic syndrome?

E coli Shigella - Both organisms produce the shiga toxin

What investigations are used in the diagnosis of gastroenteritis?

Stool culture FBC U&Es CRP LFTs

What is the general management of gastroenteritis?

Fluid replacement - oral or IV Electrolyte replacement - oral or IV Antidiarrhoeal drugs not recommended

When are antibiotics used in the management of gastroenteritis?

Extremes of age Immunocompromised patient Severe systemic illness

What antibiotics are typically used for gastroenteritis?

Ciprofloxacin Azithromycin

What are the complications of gastroenteritis?

Dehydration Electrolyte disturbance AKI Haemolytic uraemic syndrome Reactive arthritis Toxic megacolon Sepsis

How is lyme disease spread?

Via the bite of Ixodes ticks

What is the cause of Lyme disease?

By spriochaete bacteria called Borrelia burgdorferi

What is the presentation of stage 1 lyme disease?

Tick bite Flu-like symptoms Regional lymphadenopathy Erythema chronicum migrans - circular, target shaped lesion

What is the presentation of stage 2 lyme disease?

Continued flu-like symptoms Neuroborreliosis - Facial nerve palsies - Aseptic meningitis - Encephalitis Cardiovascular involvement Early painful arthritis

What is the presentation of stage 3 lyme disease?

Recurrent attacks of arthritis Late neurological disorders - Polyneuropathy - Dementia - Psychosis Discoloration at extensor surfaces (acrodermatitis chronica atrophicans)

What is the diagnostic investigation for Lyme disease?

ELISA testing for Borrelia species

What is the first line management of suspected or confirmed lyme disease?

Oral doxycycline

What is the management of an asymptomatic tick bite?

Removal of tick Monitoring for signs of infection

What reaction may occur in patients taking antibiotics for Lyme disease?

Jarisch-Herxheimer reaction

What is the management of a Jarisch-Herxheimer reaction?

The patient can continue antibiotics as long as there are no features of allergy/anaphylaxis