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93 Cards in this Set
- Front
- Back
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highest burden of vector-transmitted disease
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poor, tropical countries
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vector-transmitted disease w/ greatest morbidity/mortality
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malaria
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insecta
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6 legs; lice, fleas, tsetse flies, flies, kissing bugs
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aracnida
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8 legs; ticks and mites
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transmission cycle
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infectious host >> vector >> extrinsic incubation period >> infectious vector >> infected host >> intrinsic incubation period >> infectious host
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grace period
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minimal feeding time to transmit to host
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pathogen in vector
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enter gut >> cross epithelium >> enter nemocoel >> invade salivary gland >> leave vector via duct
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Substances released by tick feeding on host
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anticoag, platelet aggregation inhibitor, vasodilators, anesthetics, anti-inflammatory agents, immunosuppressives, anti-complement
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tick life cycle
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larva >> nymph >> adult. must take in blood meal in order to molt and move to next stage.
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feeding process
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toothed mouthparts cut into dermis, lacerate blood vessels and are held in place by "cement" secreted by tick. must remain on host for several days to fully engorge.
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vertical transmission
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some vectors can transmit pathogen to their offspring
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Lyme Disease pathogen
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Borrelia burgdorferi; spirochete; no genes for cellular biosynthesis, no LPS, lots of membrane proteins.
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Lyme Disease vectors
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deer ticks, rodents
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epidemiology
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most cases in June/July, NE, midwest
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tick life cycle
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lay eggs in spring >> larvae infected in summer >> become dormant in fall >> 2nd spring can infect people
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life cycle within tick
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larvae acquire infection (no vertical transmission), most transmissions are by nymphs.
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tick transmission
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During blood meal, spirochete crosses from gut to nemocoel to salivary glands. Takes 48 hrs.
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pathogenesis
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EC organism; disease sx due to direct attack and immune response. No LPS but lipoproteins activate TLR2. antigenic variation and phase variation allow it to thrive in ticks and mammals
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disease stage 1
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lasts days/weeks. local spread = erythema migrans. bulls eye rash.
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stage 2
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disseminated infection lasts weeks/months. colonization of diverse tissues like heart, CNS, joints
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stage 3
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persistent infection. months/yrs. long-term survival of spirochete can cause arthritis, encepalopathy.
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treatment
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AB can treat at stage 1 or 2. stage 3 less clear.
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diagnosis
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serology. not perfect.
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RMSF
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rickettsia rickettsii
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RMSF vectors
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American dog tick, Rocky mountain wood tick **vertical transmission
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bacteria characteristics
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obligate intracellular, divides in cytoplasm, has a gram-neg like envelope. energy parasites that use host actin to move btw cells.
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life cycle in tick
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lives in tick salivary gland; grace period is 10-24 hours
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RMSF rash
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erythematous, maculopapular, begins in extremities. **not always present!
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pathogenesis
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can cause endothelial cell changes, oxidative damage, platelet loss, intravascular coagulation, decreased oxygen transport to organs.
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treatment
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treat based on clinical findings, not serology. Tetracycline. Culture can be dangerous.
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Ehrlichia and Anaplasma
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gram-neg obligate intracellular. Replicate w/in vacuoles.
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ehrlichia transmission
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Infect monocytes. Lone star ticks. Deer are vertebrate hosts. found in southern US mostly
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anaplasma transmission
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Infect neutrophils. deer ticks. Same population as LD. coinfections can occur.
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disease sx
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fever, malaise, myalgia, headache, rash. range of severity.
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mosquito life cycle
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adult females live 2-5 wks. eat every 3-5 days, and 2-3 days after blood meal lay eggs in water.
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Leishmaniasis
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parasite transmitted by sand fly vector, human reservoir; active most at night, poor flier.
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transmission
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sand fly, transfusion, drug use, vertical
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3 types of disease
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cutaneous, mucosal, visceral
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cutaneous
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localized, ulcerative, usually self-healing, leaves indented scar
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mucosal
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nodular/ulcerative lesions of oro-nasal-pharyngeal mucosa. primary scar usually visible. nasal septum lesion or hoarseness may be first sign
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visceral
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fever, cachexia, hypergammaglobulinemia, splenomegaly. most asx or sublinical.
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opportunistic?
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yes. need cell-mediated immunity to clear. Chronic in ID.
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diagnosis
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parasitic dx. easy, cheap but painful.
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treatment
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glucantime for cutaneous, mucosal; amphoterin for visceral. don't attempt to treat surgically.
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Schistosomiasis
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water-borne parasitic worm that can cause urinary, hepatic disease
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transmission
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direct contact w/ larvae in freshwater; teenage males at highest risk
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life cyle
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larvae penetrate skin >>cause itchy rash >> migrate via vessels to lungs >> portal vein over 4-8 wks >> mature to adults and migrate to bladder or mesenteric vessels >> feed on blood >> produce eggs
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katayama fever
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acute disease, thought to be caused by immune complexes. fever, rash, splenomegaly, bronchospasms in first 4-8 wks of infection
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eggs
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bore way through blood vessels to reach bladder or intestine so they can exit.
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disease due to eggs
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cause mechanical damage, granulomas, inflammation. can rupture blood vessels >> see blood in urine/stool. can live for 5 years and cause lots of damage
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long-term problems
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malnutrition, anemia, kidney failure, bladder problems and cancer, fibrosis/liver cancer
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diagnosis
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look for eggs in urine or stool
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Trypanosomiasis
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2 types: African and American; transmitted by tsetse fly but differ in clinical presentation and prognosis
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African
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brucei species; fatal if not treated
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west african
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human reservoir, transmitted around river; chronic disease that takes yrs to develop
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east african
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wild animal reservoir, transmitted around savannah; acute disease develops in months
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African sleeping sickness - primary stage
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chancre, lymphadenopathy, winterbottom's sign
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secondary stage
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systemic wasting
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advanced disease
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CNS wasting disease
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antigenic variation
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leads to waves of parasitemia during infection
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American
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Chagas disease; transmitted by vector feces in bite. also by transfusion, vertical.
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acute sx
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Romano's sign (periorbital swelling), parasitemia, acute febrile illness
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chronic - indeterminate
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no serology after 12 wks, so heart or GI complications
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chronic - heart disease
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after 10-20 years; heart arrhythmia and failure can occur
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chronic -
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after 20-40 years; loss of neurons in gut >> mega esophagus and mega colon
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Malaria
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obligate intracellular eukaryotic parasite that infects liver cells and RBCs. Sexual/asexual life stages w/ complex life cycle.
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vector
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female anopheles mosquito, feeds only at night
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malaria life cycle
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sporozoites enter blood (w/in 30 min) and go to liver to mature in hepatocutes >> rupture and release merozoites >> infect RBC's and cause them to burst >> male and females can be picked up by mosquito and mate in gut.
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Prepatent period
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patient is asx while they mature in liver
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paroxysm
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shaking, chills, high fever when RBC's burst. can progress to severe anemia, coma, multiorgan failure
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pathogenesis
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adhesion to epithelial wall; host inflammation
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pregnancy
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can be turn on pregnancy-specific genes for placental cytoadherence. 1st time moms are most at risk
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vivax malaria
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relapse due to dormant malaria in liver. can only treat w/ primaquine
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resistance to malaria
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thalassemia, sickle cell trait, G6PDH deficiency,
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Indoor residual spraying
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therapy like DDT selectively kills female mosquitos after blood meal. less bad for environment
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malaria dx
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giamsa stains w/ thick and thin smears
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Artemisinin
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new antimalarial derived from chinese herbal therapy
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Main arboviruses encountered in NC
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West Nile virus, Eastern Equine Encephalitis virus, and LaCrosse Encephalitis virus
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flavivirus
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positive sense RNA virus
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flavivirus proteins
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E = main surface protein, main vaccine target; C = capsid structural protein; M = involved in maturation/release
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flavivirus replication
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viral envelope E protein binds cellular receptor >> internalized via endocytosis >> E protein triggers fusion w/ endosome >> uncoating, synthesis, assembly >> secretion
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West Nile transmission cycle
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bird reservoir, spread by mosquitos, can accidentally infect humans and horses. Btw humans by tranplant, transfusion, vertically
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epidemiology
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most common in late summer/early fall. 80% asx; most deaths among elderly
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west nile uncomplicated disease
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fever, headache, GI sx, fatigue, generalized rash.
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complicated disease
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prolonged fever/headache, mental status changes, coma, meningoencephalitis
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pathogenesis
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skin/langerhans cells >> to lymph nodes >> primary viremia, spreads to spleen/kidneys. clears in 1 wks. CNS invasion in subset
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Dengue
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positive sense RNA virus, 4 distinct but related viruses, increasing prevalence
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dengue vectors
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mosquito Aedes aegypti and the related A. albopictus; human reservoir.
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epidemiology
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urban endemic; needs population in order to maintain
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spectrum of disease
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asx, fever, hemorrhagic fever, shock
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disease status
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depends on age, genetic status, previous infection hx. **secondary infection usually worse than primary
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Antibody-enhanced theory of disease
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AB to previous infection enhance uptake into monocytes/macrophages via FcR, leading to increased replication and cytokine release
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treatment
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no antivirals exist; mosquito control and supportive therapy
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