IMMUNE & HAEM 201 International Health Flashcards
What is the causative organism of TB?
Mycobacterium tuberculosis
How can humans catch TB cattle and what bacteria is it?vb
Drinking unpasteurized milk containing mycobacterium bovis
Why does TB prefer the upper lungs?
Greater oxygenation here TB is an obligate aerobe
How does TB resist destruction?
Strong cell wall with a waxy layer
What happens once TB bacilli settle in the upper alveoli?
They cause parenchymal inflammation
Why do some people not contract a TB infection when exposded?
Low bacterial load and sufficient innate immunity
What type of hypersensitivity reaction is there to TB exposure and what does it result in?
Type 4 - granuloma formation
Describe a Ghon focus in TB
Granuloma - central nectrotic area surrounded by calcification
What is Miliary TB?
When TB is diffusely spread throughout the lung
What systemic diseases can arise from a TB infection?
Miliary TB Brain abscess Meningitis Osteomyelitis of the spine pericarditis with effusion
Why may a TB infection cause lobar collapse?
Infection spreads to mediastinal lymph nodes which can enlarge and compress the bronchi
What are some long term lung complications from TB?
Bronchiectasis or emphysema
Reactivation - bronchopneumonia
What are the clinical features of TB?
primary infection may be asymptomatic/flu like Erythema nodosum or keratoconjunctivitis Night sweats chest pain cough +/- haemoptysis Swollen lymph nodes Weight loss
What investigations can be done to check for TB?
Sputum culture may show acid fast bacilli (highly contagious at this point|)
Bacterial culture
Mantoux test
What can cause a false positive in the Mantoux test?
BCG or nonTB mycobacterium exposure
What test can look for latent TB disease?
Interferon gamma release assay
What is the treatment for non resistant TB?
2 months Rifater (rifampicin, isoniazid and pyrazinamide) + ethambutol
or
4months Rifinah ( rifampicin and isoniazid)
Which parasite causes African Sleeping sickness and what is its vector?
African Typanosomiasis and carried by Tsetse flies
What is the brief replication cycle for African sleeping sickness?
Bacilli taken up by flies, reproduce asexually in gut, attach to salivary glands and transferred to human during a blood feed (can cross the BBB)
What parasite causes Chagas disease and what is its vector?
American Trypanosomiasis carried by triatomine bugs
What is the brief replication cycle for Chagas disease?
Triatomine bugs live in housing, the bacilli taken up by bug which moves through GIT to rectum. Bug bites human who when scratches the bite allows this faeces to enter skin
How do people develop chagas disease? Slow or fast onset?
Fast onset - acutely unwell
How do you treat chagas disease?
nifurotimox and benzimidazole
What parasite is transferred through Water Snails?
Schistosomiasis
Where does schistosomiasis travel to in the body?
Liver via portal bein
How do you treat a schistosomiasis infection?
Praziquantel
Which paraside causes bubonic plague?
Yesinnia Pestis
Which parasite causes elephantiasis?
Lymphatic filiarisis
Which parasite causes river blindness?
Onchocerciasis / round worm
What parasite causes anal itching commonly in children?
Enterobiasis - pinworm/threadworm
What are the general abx for treating nematode infections?
mebendazole, albendazole and ivermectin
How do RBC differentiated from normoblastic nucleated cells to their mature form?
Via action of EPO derived from the kidney which causes them to become anucleate
Where is haemoglobin synthesised?
Mitochondria of developing RBC
What shape are mature RBC’s
Biconcave disks
What is the general structure of Hb?
Haem group + globin chain
4 in total
What is haem made up of?
Iron and a protoporphyrin
How is iron transported in the blood?
Bound to transferrin
What are the different types of haemoglobin?
HbA - two alpha, two beta globin chains (most abundant)
HbA2 - two alpha, two delta
HbF - two alpha, two gamma
What is vitamins are required for complete differentiation and DNA replication in RBC’s?
Vitamin B12 and folic acid
How generally do haemoglobinopathies affect RBC’s?
Change the globin chain production or structure therefore changing the solubility of Hb
This makes the RBC more fragile, therefore decreasing the lifespan
What are the main clinical outcomes of having a haemoglobinopathy?
Anaemia, splenic crises - increased EPO production and haematopoetic tissue expansion
How do patients with a homozygous beta thallasaemia usually present?
Early in life with failure to thrive, severe anaemia and hepatosplenomegaly
How do you treat a homozygous beta thallasaemia?
Regular blood transfusions, folic acid and desferrioxamine
What is desferroxiamine used for?
prevent/treating iron overload
What may a patients blood film show with a heterozygous beta thallasaemia?
Hypochromic, microcytic rbc’s - mild anaemia
What is the cause of sickle cell anaemia?
A single base mutation changing adenine to thymine
What happens to RBC’s in sickle cell?
Some RBC’s have HbS which is insoluble and cant carry oxygen. It polymerises changing the flexibility of the cell - sickle shaped. It can’t move through microcirculation
What may be seen in a patient with homozygous sickle cell anaemia?
Acute pain from tissue infarction
Pulmonary hypertension
Cardiomyopathy
Splenomegaly
What blood disorder would have microcytic cells, low MCV and high iron levels?
Sideroblastic anaemia
What blood disorder would have microcytic cells, low MCV, normal/high iron and abnormal levels of foetal and A2 haemoglobin?
A haemoglobinopathy
What blood disorder would have macrocytic cells, with high mcv, megaloblastic cells?
B12/folate deficiency
What is a megaloblastic cell?
An immature RBC containing a nucleus but larger than a normoblast due to insufficient DNA synthesis
What may cause macrocytic, high MCV and normoblastic RBC’s?
Alcohol/Hypothyroidism
What indicates that there is a haemolytic anaemia/blood loss?
Macrocytic, high MCV, normoblastic cells but with a high reticulocyte count
