Tropical Medicine and Beyond Flashcards
What is a nematode?
Microscopic roundworm
What are the 3 classifications of tissue nematodes?
Lymphatic, subcutaneous, conjunctiva
What is filariasis?
Tissue infection with nematodes belonging to Filaroidea (known as elephantitis)
What is the most prevalent type of filariasis?
Lymphatic
What are the causative agents of filariasis?
Wucheria bancrofti
Brugia malayi
Brugia timori
What is the most common filariasis cause in Malaysia?
Brugia malayi
What is sub-periodic periodicity zoonotic infection
Irregular periodicity infection that is transmitted between animals and humans
Describe the periodicity of W bancrofti and B malayi infection
Nocturnal and sub-periodic
Describe the pathogenesis of lymphatic filariasis
Larvae transmitted by mosquito
Larvae invade lymphatics and lymph nodes where they mature
Mate and release microfilariae into lymphatics and bloodstream
Mosquito takes a meal and invests microfilariae
Describe filarial oedema
Adult worms in lymph vessels die but bacterial colonisation of tissues causes inflammatory process - proliferation of connective tissues leading to fibrosis which obstructs lymph drainage leading to oedema
Describe the clinical manifestations of filariasis
Most are asymptomatic
Lymphoedema occurs years after infection
What is tropical pulmonary eosinophilia in filariasis?
Lung disease presenting with a nocturnal cough, wheezing and fever resulting from immune hyperesponsiveness to microfilariae in pulmonary capillaries
Describe the renal pathology of filariasis
Microfilaria lead to dilation of renal lymphatic system, rupture and lymph fluid passed into renal pelvis. Causes chyluria (lymph in urine) which leads to a milky urine appearance.
Potential haematuria and proteinuria also
What is the difference between acute and chronic filariasis
Acute - lymphoedema of extremities
Chronic - elephantitis due to recurrent bacterial infection
How would you diagnose lymphatic filariasis?
Ultrasound to detect worms in lymphatic vessels
Blood for thin and thick film, collected at night (due to nocturnal periodicity of microfilaria)
Antigen detection (serology)
What drug is used to treat filariasis?
Diethylcarbamazine (DEC) which kills microfilaria and adult worms
What mosquito transmits dengue fever?
Aedes aegypti
How many serotypes of dengue fever are there?
4 (DEN1, DEN2, DEN3, DEN4)
Describe the dengue virus genome and structure
Single strand of positive sense RNA (translated directly to single long polypeptide which is cut into ten proteins)
Describe the pathophysiology of dengue fever
Skin inoculation by insect
Infection of dendritic cells
Infection of lymph node
Viremia
Why is second infection with different dengue fever serotype worse?
Larger inflammatory response leading to worse symptoms including dengue haemorrhagic fever
What are the risk factors for severe dengue?
Pre-existing dengue antibody (previous infection or maternal antibody)
Location with 2 or more serotypes in circulation at high levels
What are the 2 main methods of laboratory diagnosis of dengue fever?
Detection of dengue virus
Detection of anti dengue antibodies
What is the difference in serotype between primary and secondary dengue fever
In secondary, IgG antibodies are present immediately however in primary, only IgM are present until about day 7, when IgG can be found
What is the treatment for dengue?
Rehydration, bed rest, pain relief
Who should be vaccinated against dengue? How often are they vaccinated?
People with a previous dengue infection. Vaccination dose every 6 months
What is the vector for Chikungunya?
Aedes mosquito
What is the main symptomatic difference between dengue and Chikungunya?
Severe joint pain
How would you diagnose Chikungunya?
Clinical - high fever, joint pain
Epidemiology - traveled to endemic area in last 12 days
Laboratory - decreased lymphocytes, serological diagnosis
What is the incubation period for dengue?
12 days
What is the time frame for antigen and antibody detection of Chikungunya?
IgM at day 4-7
IgG at day 15
What is the difference between pharmacokinetic and pharmacodynamic durg interactions?
pharmacokinetic = one drug affects the absorption, distribution, mtabolism, excretion of another drug pharmacodynamic = drugs influence each other's effects directly
Describe drug interactions at the absorption level
Formation of complexes can considerably reduce bioavailability of drugs
Describe drug interactions at the distribution level
A second drug can displace a drug from a plasma protein and increase levels of the unbound active drug available to cause effect
Describe drug interactions at the excretion level
Drug-induced reduction in GFR can lead to reduced clearance and higher plasma conc. of drugs. Competition for tubular transporters
Describe drug interactions at the metabolic level (cytochrome P450)
Inhibition/competition for cytochrome P450 can result in higher drug levels in body
What are the common interactions with St. John’s Wort?
Reduced efficacy of oral pill - unwanted pregnancy
Reduced plasma conc. of antiretroviral and anticancer drugs
What are the interaction problems caused by grapefruit juice?
Inhibits CYP3A4 which leads to increased drug conc.
What are the factors associated with Salmonella food poisoning?
Consumption of inadequately cooked meat/poultry
Cross contamination of food from infected handlers
Presence of flies, cockroaches, rats in food environment
What is the causative agent for typhoid?
Salmonella typhi
What are the risk factors for typhoid?
Poor sanitation, overcrowding
What is the incubation period for typhoid?
2 weeks (may vary between 3-28 days)
What are the symptoms and complications of typhoid?
Fever, headache, constipation, bradycardia.
Can lead to intestinal perforation and becoming a chronic carrier (persistent positive stool culture for salmonella a year after onset)
What organism causes cholera? How does it have its effect?
Vibrio cholera. Multiply in small intestine to produce potent enterotoxin = pouring out of isotonic fluid by gut mucosal cells
What are the signs and syptoms of cholera?
Rice-watery stool, dehydration, vomiting, muscle cramps, hypovolemic shock, scanty urine
How is chloera managed?
Rehydration, monitor, antibiotic (severe cases), vaccination
What is dysentery?
Bloody diarrhoea caused by a variety of organisms including shigella spp
What is shigellosis?
Frequent passage of sacnty amounts of stools mixed with blood and mucus. Fever, abdominal cramp and tenesmus (pain around anus during defacation)
What are the complications associated with E.coli O157
Bloody diarrhoea, colitis, sub-mucosal edema. Hemolytic Uremic Syndrome (HUS) can lead to death
What kind of bacteria is staphylococcus aureus?
Non-spore forming gram positive coccids. Heat stable and pH stable (resistsant to most proteolytic enzymes
What is the incubation period for staphylococcus aureus?
1-6 hours
What are the problems associated with listeria monocytogenes?
Abortion in pregnant women due to trans-placental spread and meningitis in immunocompromised
What kind of bacteria is Clostridium botulinum?
Obligate, gram-positive, spore-forming anaerobe. Heat labile and unstable at alkaline pH (resistant to acidic stomach)
What is the incubation period for Clostridium botulinum?
12-72hrs
What is the incubation period of hepatitis A?
30 days average
What is pharmacogenomics?
The science that allows us to predict a response to drugs based on an individuals genetic makeup