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Arthropod borne infectious disease. Arthropods that Transmit Disease. Ticks, mosquitoes, fleas and biting flies Transmission usually by biting or ingestion. Infections. Bacterial Ricketsia ricketsii , Borrelia burgdorferi , Yersinia pestis , Francisella tularensis Viral ( arboviruses )
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Arthropods that Transmit Disease • Ticks, mosquitoes, fleas and biting flies • Transmission usually by biting or ingestion
Infections • Bacterial • Ricketsiaricketsii, Borreliaburgdorferi, Yersinia pestis, Francisellatularensis • Viral (arboviruses) • Dengue, West Nile, Encephalitic viruses • Parasites • Malaria, Dracunculiasis, tape worms
Rocky Mountain Spotted Fever • Caused by obligate intracellular bacterium Rickettsia rickettsii • Tick borne disease
Lyme Disease • Borreliaburgdorferi • Spirochete • Obligate Intracellular pathogen
Borreliaburgdorferi • 1.5Mbp • Strange genomic layout • Linear chromosome (900 kb) • Has over 20 circular AND linear plasmids • Genome decay in obligate intracellular bacteria • Loses many biosynthesis pathways (why make it if you can get it from the host)
Epidemiology • Transmitted by ticks (mainly deer ticks) • Most often by nymphal ticks • Mammalian reservoirs: mice and deer • Prevalent in northeast and midwest but spreading and increasing occurrence
Lyme disease symptoms 1st stage: first few days erythema migrans (outwardly expanding rash) Therefore gets a bullseye appearance. Not always occurs (most of the time though) Flu-like symptoms too (fever, headache, muscle soreness, malaise) Best treatable stage!
Lyme disease symptoms • 2nd stage: Dissemination: days to weeks • spreads to bloodstream and may have bullseye rash appear at other sites of the body • Also pain in muscles joints and tendons, heart palpitations, strong headaches
Lyme disease symptoms • 3rd Stage: Persistent infections (months later) • Brain, nerves, eyes, heart, joints • Cognitive impairment, weakness, pain in joints (especially the knees), fatigue • Can end up with permanent damage
Transmission • Bacteria normally live in gut epithelium of tick • Must migrate to salivary glands to be secreted to host
Vaccine LYMErix • Recombinant Outer surface protien A (OspA) • Your body doesn’t make antibodies to OspA normally • OspA only expressed in unfed ticks, not in fed ticks or host • Temperature is the trigger to stop OspA and start making OspC • other triggers for making virulence proteins are pH and Fe starvation
How the vaccine works • Bacterial migration frommidgut to salivary glands is inhibited when ticks feed on OspA (and also in OspC) immunized mice • So immune serum appears to kill the bugs in the tick or prevent migration
West Nile • +RNA Flavivirus • transmitted by mosquitoes that usually infects birds • Many human infections are avirulent
West Nile Severity of infections: • Avirulent • Mild fever (West Nile Fever) • Serious meningitis or encephalitis
Yersinia pestis • Plague • Bubonic • Pneumonic • Septicemic • Transmitted by fleas
Plague • Symptoms: Mostly general • pain, fever, malaise, headaches • Bubos
Molecular mechanisms • Plasmids and pathogenicity island • Specialized Type 3 Secretion system • Yop (Yersinia outer proteins) for evading immune system This includes preventing phagocytosis, adhesion, and inducing macrophage death
Francisellatularensis • Facultative intracellular pathogen causing tularemia or “rabbit fever” • Often by ticks, also from mosquitoes and biting flies
Tularemia • All feasible routes of infection • Infects >250 species animals • Infects all cell types tested