Infectious Diseases - Travel Related Infection Flashcards
What is the causative organism of tuberculosis (TB)?
Mycobacterium tuberculosis
What are the risk factors for TB?
- known contact with active TB
- immigrants from areas of high TB prevalence
- people with relatives or close contacts from countries with a high TB prevalence
- immunosuppression
- IVDU
Outline the disease course of TB.
TB is spread by inhaling saliva droplets from infected people, spreading through the lymphatics and blood to form granulomas around the body.
Active TB is when there is active infection within the body. In most cases the body can mount a significant immune response and clear the infection.
Latent TB occurs when the immune system encapsulates sites of infection, but does not clear the infection.
Secondary TB occurs when latent TB reactivates.
When the immune system cannot control the disease, TB becomes disseminated. This is miliary TB.
What is the most common site for TB granuloma formation?
The lungs - TB have a high oxygen demand, so thrive in the oxygen-rich environment of the lungs.
Give some extrapulmonary TB manifestations.
- lymph nodes
- pleura
- central nervous system
- pericardium (e.g. pericardial effusion / tamponade)
- gastrointestinal system
- genitourinary system
- bones and joints
- cutaneous TB
Presentation of TB.
- lethargy
- fever / night sweats
- weight loss
- cough (?haemoptysis)
- lymphadenopathy
- erythema nodosum
- spinal pain in spinal TB (ie. Pott’s disease)
What is the Mantoux test?
Mantoux test - tuberculin injected into the intradermal space, creating a bleb under the skin. NICE suggest considering an induration of 5mm or more a positive result, suggesting previous vaccination, latent or active TB.
After a positive result, patients should be assessed for active disease.
What is the Interferon-Gamma Release Assay (IGRA) test?
Blood sample is mixed with antigenic material from the TB bacteria. If interferon-gamma is released from the white blood cells, this is considered a positive result and indicates active TB.
What are the x-ray findings of primary TB?
- patchy consolidation
- pleural effusion
- hilar lymphadenopathy
What are the x-ray findings of secondary TB?
- patchy or nodular consolidation
- cavitation
- affecting upper zones
What are the x-ray findings of miliary TB?
Millet seeds uniformly distributed throughout the lung fields.
What are the ways to collect cultures for tuberculosis?
- sputum culture (3x)
- Mycobacterium blood cultures (require a special culture bottle)
- lymph node aspiration or biopsy
Management of acute pulmonary TB.
R - Rifampicin for 6/12
I - Isoniazid for 6/12
P - Pyrazinamide for 2/12
E - Ethambutol for 2/12
A patient with tuberculosis is started on rifampicin, isoniazid, pyrazinamide and ethambutol. What should also be prescribed?
Pyroxidine - co-prescribed prophylactically to reduce the risk of peripheral neuropathy from isoniazid.
What are the side effects of Rifampicin?
- red / orange discolouration of urine
- inducer of CY P450 so reduced drugs metabolised by this system (e.g. COCP)
- hepatotoxic
rifampicin (“red-an-orange-pissin’”)
What are the side effects of isoniazid?
- peripheral neuropathy - pyridoxine is co-prescribed
- hepatotoxic
isoniazide (“I’m-so-numb-azid”)
What are the side effects of pyrazinamide?
- hyperuricaemia resulting in gout
- hepatotoxic
What are the side effects of ethambutol?
- colour blindness
- reduced visual acuity
- hepatotoxic
ethambutol (“eye-thambutol”)
What is the causative organism of malaria?
Plasmodium family of protozoan parasites.
The most severe and common cause of malaria is Plasmodium falciparum.
How is malaria spread?
Bites from the female Anopheles mosquitoes.
What are the types of Plasmodia?
- Plasmodium falciparum (most common and severe)
- Plasmodium vivax
- Plasmodium ovale
- Plasmodium malariae
Presentation of malaria.
- fever, sweats and rigors
- malaise
- myalgia
- headache
- vomiting
Signs of malaria.
- pallor
- hepatosplenomegaly
- jaundice
Signs of haemolytic anaemia.
Investigations for malaria.
- malaria blood film
- FBC (haemolytic anaemia)
- LFTs (hyperbilirubinaemia)
Management of malaria.
All patients with falciparum malaria should be admitted for treatment as they can deteriorate quickly.
IV options for malaria include:
- artesunate
- quinine dihydrochloride
What are the complications of Plasmodium falciparum?
- cerebral malaria
- seizures
- reduced consciousness
- hypoglycaemia
- AKI
- pulmonary oedema
- DIC
- severe haemolytic anaemia
- multi-organ failure
- death
What general travel advice can be given to avoid malaria?
- use mosquito spray
- use mosquito nets
- take antimalarial medication as recommended
Presentation of Typhoid fever.
- sustained fever
- anorexia
- malaise
- vague abdominal discomfort
- constipation / diarrhoea
- dry cough
Treatment of typhoid fever.
IV ceftriaxone
What investigations should be considered in a patient who has recently travelled and now has fever?
- complete blood count
- LFTs
- U&Es
- malaria smears
- blood cultures x2 (biohazard labels)
- urinalysis / urine culture
- stool culture
- CXR
- HIV, Hep B, Hep C and Syphillis serology
What type of virus is HIV?
RNA retrovirus
HIV-1 is the most common type
How does HIV cause immunosuppression?
HIV enters and destroys CD4+ T helper cells.
How is HIV transmitted?
- unprotected anal, vaginal or oral sexual activity
- mother to child at any stage of pregnancy, birth or breastfeeding
- mucous membranes
- blood
- open wound exposure
What are AIDS-defining illnesses?
Illnesses associated with end-stage HIV infection, where CD4+ T Helper cell count has dropped to a level that allows for unusual opportunistic infections and malignancies to appear:
- Kaposi’s sarcoma
- candidiasis (oesophageal or bronchial)
- lymphoma
- tuberculosis
How can we test for HIV?
- antibody blood test
- test for p24 antigen
- PCR testing for HIV RNA levels
How is HIV monitored?
- CD4 count (lower count = higher risk of opportunistic infection)
- viral load (number of copies of HIV RNA per ml of blood)
Treatment of HIV.
Antiretroviral therapy (ART) offered to everyone regardless of viral load or CD4 cell count.
The aim of treatment is to achieve a normal CD4 cell count and undetectable viral load.
What advice should be given to patients following a diagnosis of HIV, upon their reproductive health?
- condom use for vaginal and anal sex
- dental dam for oral sex
- Caesarean section should be used for birth
Mothers can breast feed if viral load is undetectable, but there may still be a small risk of contracting HIV through breastfeeding.
Describe the post-exposure prophylaxis for HIV.
Combination of ART therapy within 72 hours of exposure, continuing for 4 weeks.
