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GSU BIOL 1103K - Typhus

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*Epidemic Typhus(most important louse borne disease)Causative agent: Rickettsia prowazekiiSmall, obligate intracellular bacteriumVector: Body louse; Pediculus humanus humanusReservoir: Humans (so a human disease)Symptoms in people:Appear about 10-14 days after infectionHigh fever (~102 degrees F)Extreme pain in muscles, jointsHeadache (worse than migranes!) and cerebral impairmentOn 3rd to 5th day, macuopapular rash on trunk, spreadsto rest of body (see slide below)Eventually often necrosis and gangreneMortality rate 20 to almost 100%Recovery begins after 14-21 days but requires monthsReservoir peopleSome people become asymptomatic carriers (sound familiar!!)When stressed, bacteria can reemerge, produce milder form of disease called Brill-Zzinsserdisease or recrudescent typhusThese people are the main reservoirs for the disease*Cycle of Rickettsia in body lice:1. Lice (A) acquire bacteria while feeding on infected humanreservoir (B)2. Bacteria invade louse gutcells (1), multiply, and burst the gut cells releasing bacteria back into the gut lumen (eventuallycauses death of louse)3. Bacteria transmitted to another person in louse frass (feces) (2), or louse body fluids if lice arecrushed, that end up on their skin.4. Bacteria then enter human through bite site, or are “scratched” into the skin. But not infectedvia bite itself (bacteria never end up in louse saliva)In human host, bacteria destroy epithelial lining of blood vessels (see rash)Treatment: tetracycline antibiotics eg. DoxycyclineEasily cured if diagnosed properly (but doctors in US may not be familiar with the now raredisease)Distribution of typhus. Shaded areas represent possiblezoonotic reservoirs.Present in southern flying squirrels (Glaucomys volans) insoutheast including Georgia. Seroprevalence can be 90% in latewinter and autumn. Vector is Neohaematopinus sciuroptera.Occasional human cases when flying squirrels occupy attics,especially in winter.Historical significance:it wasn’t the Russian winter that defeated Napoleon’s army,but epidemic typhus from liceTyphus determined the outcome of numerous military campaigns.Often killed more soldiers than died of wounds from fighting.Destroyed French army in 1528 as they were about toconquer NaplesDestroyed the army of Emperor Maximillian II in Hungary in1566; 30,000 diedDevastated army of Napoleon on route to Moscow,killed/incapacitated over 50% of his troopsSeveral major epidemics in Russia 1919-1923 13 million cases,5 million deathsToday mainly in Ethiopia (1000-5000 cases/year) but numerousother small outbreaks*Louse-Borne Relapsing FeverPathogen is bacterium Borrelia recurrentisVector is human body louseHumans only known reservoirLice are infected horizontally from infected people, Borreliapenetrate gut and move into hemolymph, nerves, muscle*Borrelia is released when lice are crushed, not present in salivaor fecesScratched into abrasions in skin, or can penetrate intact skinSymptoms include:Sudden onset of fever, headache, anorexia, nausea,dizziness, coughing, vomitingDecrease in platelets can lead to bleeding disordersFever for 2-12 days, followed by 2-8 days without feverFrom 2-5 relapsesLiver and spleen enlarge, can cause difficulty breathingMortality if untreated 5-40%Responds to tetracycline, penicillinLice can infect livestock (specific species for each animal)Haematopinus suis (Hog louse), may transmit swinepoxHaematopinus eurysternus (Cattle louse)Chewing/biting lice on chickens (and other birds); feed on dead skin, feathers, not blood, but canstill stress birdsHemiptera NotesClass InsectaOrder Hemiptera*(common name: true bugs)“Hemi” means half, “ptera” mean wing, so “half wings”Anterior half of forewings is thickened, posterior half of forewingis membranousSecond pair of wings are all membranous (for flight)Wings secondarily absent in the bed bugs (their ancestors hadwings but bed bugs lost them through evolution because theydidn’t need them)More about bugs:Flattened dorsoventrally (top to bottom)Piercing-sucking mouthparts-fused into a beak or rostrumIncomplete metamorphosis (egg-nymph-adult)Most species feed on plants or are predators on other insectsOnly two families of medical significance (Reduviidae, Cimicidae)Fun fact to impress your friends: all bugs are insects, but not all insects are bugs (i.e. Hempitera)!Predatory bugs, such as this wheel bug (rounded-ridge on back),can inflict painful bites. (Don’t grab one!)But these bites heal without long-term


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