WK 2- Viral Pathogenesis Flashcards

Question

How do arthropods cause disease

Answer 1

1. Directly by their feeding → irritation → scratching→ e.g. scabies, head lice 2. Indirectly by transmitting infections→ e.g. Mosquitoes -viruses (e.g. dengue), Protozoa (e.g. malaria), Worms e.g. filariasis, Ticks -bacteria (e.g. plague), Flies –trypanosomes (e.g. Trypanosomiasis)

Answer 2

highly contagious and spread via resp droplets (through coughing and sneezing) or direct contact with secretions from the nose or mouth

Answer 3

measles virus infects via the respiratory tract→ will move into local lymphatics and lymph nodes→ the virus will then replicate and spread to other lymph nodes and the spleen→ the virus will cause temporary and severe immunosuppression making T lymphocytes susceptible to infection and causes apoptosis of encountered macrophages (allowing it to escape destruction and causes lymphopaenia)→ the presence of the virus in the blood allows it to manifest in the epithelia and cause necrosis→ causing a decreased resistance to secondary bacterial infection→ destruction of the epithelia appears as a rash/red eyes - Antigen/antibody complexes in capillary endothelium → vasodilation, plasma leakage

Answer 4

host immune response is responsible for fever, tiredness, cough, runny nose and/or red inflamed eyes – severity ↑s over 3 days →Kopliks spots: small white spots on a red base on the inside of the cheek→ then turns to blotchy, dark red rash appears starting on face, then spreads over entire body (24 to 48 hours) & lasts ~6 days

Answer 5

if the infection is severe enough it will allow for opportunistic bacterial super infections (such as bronchopneumonia and otitis media due to damage of epithelium), primary viral pneumonia (due to decreased T cell immune response), acute encephalitis (result of attack of Ag in CNS) and SSPE (subacute sclerosing panencephalitis→ rare and develops 1-10 years after recovery from an acute infection→ virus remains latent and when activated is universally fatal – death within 1-3 years- not caused by vaccine strain of measles)

Answer 6

effects of malnutrition, poor local mucosal defences, poor medical services, exposure to higher viral load, high exposure to bacteria in the environment, impaired immune defences, longer infective period → major cause of death in resource poor countries

Answer 7

the viruses genome can be spliced and integrated into host genome→ allows it to replicate when host cell replicates, allows it to evade host immune system -allows it to kill host cells and evade immune system

Answer 8

high variable virus that mutates easily (due to not having checking mechanisms)→ causes multiple different strains of HIV (even within a single infected individual)→ mutation rate of 3 x 10-3 per day→ so if going to treat with antiviral drugs must require numerous drugs that attack numerous strains of the virus

Answer 9

1. Acute infection→ pt is typically highly infections due to a enormous viral burden in blood and genital secretions (may be unaware they are infected) 2. Clinical latency→ with or without persistent generalised lymphadenopathy 3. Aids

Answer 10

-HIV penetrates the mucosa epithelium then infects submucosal CD4T cells, DC and MO→ will then spread to the lymph nodes via these cells and then into the plasma→ once it enters the blood there is widespread dissemination to organs such as the brain, spleen and lymph nodes

Answer 11

Primary infection→ large number of susceptible CD4T cells and no HIV specific immune response - Once T cell is infected there is rapid replication and high HIV RNA levels (Peak usually coincides with seroconversion (4-10 weeks after exposure)) - Following this, a specific CD8+ cytotoxic T lymphocyte response develops → causing a decrease in plasma HIV levels→ levels of the virus stabilise within 6 months of infection

Answer 12

asymptomatic except for possible lymphadenopathy (due to lymphoid tissue being a major reservoir for HIV)→ high rates of HIV replication and CD4 T cell destruction occur in this period→ virus is mainly intracellular in this period → there are high concentrations of extracellular HIV on the follicular dendritic cell processes within germinal centres of lymph nodes→These dendritic cells trap free virus and infected CD4T cells→ causes disruption of the lymph node architecture and the release of HIV into the blood stream

Answer 13

caused by infection of schistosomes-->large cause of death (main in rural areas of developing world)→ 4th most prevalent helminthic disease in the world

Answer 14

the early immune response is stimulated by parasites entering through the skin and then migrating through the lungs→ involves macrophages and T cell mediated inflamm immune response (cause fatigue, coughing, fever)→ when the adult worm is in the portal circulation produce eggs there is a shift to TH2 mediated immune response→ the Ag produced by the eggs cause an anti-inflamm response → causes production of cytokines that reduce inflammation and promote the formation of granulomas around the parasite eggs in the lungs, pancreas, liver and lymph nodes

Answer 15

down regulation of TH2 response limits the tissue damage→ most are asymptomatic but can be severe through production of persistent granulomatous inflammation (causing fibrosis) and if the eggs are trapped in the liver sinusoids it will cause periportal fibrosis and occlude portal veins→ leading to portal HTN, ascites and GI bleeding, hepatosplenomegaly

Answer 16

by releasing Ags that trigger the release of cytokines that reduce inflammation and promote the formation of granulomas around the eggs

WK 2- Viral Pathogenesis Flashcards

(40 cards)