Medical Microbiology: Pathogenesis of Parasitic Infections Flashcards
1
Q
What is Leishmaniasis?
A
- A parasitic disease caused by Leishmania parasites
2
Q
What are the different types of Leishmaniasis?
A
-
Visceral leishmaniasis
- Asia: Leishmania donovani
- Middle East/Africa/Asia: L. infantum variants
- Latin America: L. chagasi
-
Cutaneous Leishmaniasis
- Old world disease: Mediterranean/Middle East - L. Infantum/L. major/L. tropica
- New world disease: Central and South America - L. braziliensis/amazonensis/mexicana
3
Q
Describe the life cycle of Leishmania
A
- Sand fly bites you and transfers promastigote into the body
- Promastigotes invades macrophages
- Inside macrophage promastigotes form nests of amastigotes
- This causes macrophage to burst resulting in release of amastigotes which go on to infect other cells
4
Q
What is the vector for leishmaniasis?
A
- Lutzomyia/Phlebotomus
5
Q
What causes diffuse cutaneous leishmaniasis?
A
- Occurs as a result of someone not being able to produce an adequate immune response to the parasite
6
Q
Describe the pathogenesis of cutaneous leishmaniasis
A
-
Acute lesions
- Due to tissue damage caused by inflammatory response to presence of parasites in macrophages
- Parasite killed by Th1 pro-inflammatory responses and macrophages
-
Latency
- Regulatory immune response which causes parasites to remain dormant long-term
- Characterized by balance of Th1 and anti-inflammatory responses
-
Relapse (rare)
- Alteration in immune response e.g. change in Th1 vs immune regulation due to HIV infection
- Mucocutaneous disease associated with strong but inadequate inflammatory response to parasites that have metastasized to mucosa
- Diffuse cutaneous leishmaniasis associated with uncontrolled parasite replication
7
Q
What are the 3 main species of Helminths that can cause Schistosomiasis?
A
- Schistosoma mansoni
- Schistosoma haematobium
- Schistosoma japonicum
8
Q
Decribe the life cycle of Schistosoma
A
- People exposed to infective stage in contaminated water
- Get infected with cercariae which migrate through the body
- Cercariae fbecome adults in mesenteric system
- Female and male mate and female releases eggs into mucosal epithelium
- Eggs get excreted either through faeces or urine
9
Q
What is cercarial dermatitis?
A
- Allergic type reaction caused by exposure to cercariae from animal or bird schistosomes
- Requires pre-sensitization
10
Q
What is a key feature of the immune response to Schistosomiasis?
A
- Granuloma formation - Eggs from female become organized in granulomas
- Repeated insults and tissue repair leads to fibrosis and organ damage
11
Q
What is Hepato-intestinal schistosomiasis?
A
- Schistosomiasis infection caused by S.mansoni and S. japonicum
- Pathology caused by immune response to eggs - eggs are pushed through intestinal wall and mucosa and are then excreted
- This causes hepatosplenomegaly
12
Q
What diseases/conditions can urinary schistosomiasis cause?
A
- Haematuria - blood in the urine
- Can also lead to bladder cancer due to inflammation of bladder wall caused by eggs
13
Q
What is onchocerciasis?
A
- Major blinding disease caused by filarial parasite (Onchocerca volvulus)
- Transmitted by blackflies
14
Q
Describe the life cycle of Onchocerca volvulus
A
- Blackfly bites you and transmits infectious larvae
- Larvae migrates under the skin and develops into adults
- Male and female adult mate and female releases 1000s of larvae called microfilariae
- Microfilariae get taken up by blackfly and develop in blackfly until they can be trasnmitted themselves
15
Q
What is the vector of Onchocerca volvulus?
A
- Simulium
18
Q
What is punctate keratitis?
A
- Condition caused by death of small groups of cells in the cornea as a result of Microfilariae being killed by immune response
19
Q
What is sclerosing keratitis?
A
- Condition caused by repeated inflammation of the cornea
- This results in opacification of the cornea causing blindness
20
Q
Describe the immune response that occurs due to onchocerciasis
A
- Rapid allergic reactions that kill microfilariae in skin
- Activation of mast cells which recruit other immune system cells e.g. eosinophils
-
Acute stage
- Strong TH2 response which produces IL-4 and IL-5
- IL-4 leads to IgE production and IL-5 leads to recruitment and activation of eosinophils
-
Chronic stage
- Host immune response starts to be regulated and shut down
- Modified TH2 response - production of IL-10, TReg cells and IgG4 antibodies
22
Q
What are some of the diseases transmitted by hard ticks?
A
- Tick typhus
- Viral encephalitis
- Viral fevers
- Viral haemorrhagic fevers
- Tick paralysis
23
Q
What are some of the diseases transmitted by soft ticks?
A
- Q fever
- Relapsing fever
26
Q
What are some characteristics of pubic lice?
A
28
Q
What is Myiasis?
A
- Parasitic infestation of the body of a live animal by Botfly larvae (maggots) which grow inside the host while feeding on its tissue
29
Q
What drugs can be used to treat infections caused by different types of parasites?
A
- Tinidazole has shorter dose regimens compared to other drugs used to treat protozoa infections - 1g once a day for 3 days
- Metronidazole has more adverse reaction and has longer dose course - 1 or 2 week course
- Benznidazole used to treat chagas disease but causes very bad adverse reactions so people can’t complete course
- Heavy metals used to treat Leishmaniasis
