Ento 210 1st EditionExam # 2 Study Guide Lectures: 10-16Lecture 10-reasons for optimism about diseases in 1900s: -vaccines were more common-cloroquine was more readily acceptable-DDT was still usedWhat’s the difference between emerging and reemerging diseases?-emerging disease – rapidly increasing and spreading-reemerging disease – diseases that have occurred before but come back with a slight variation in some way (location, strain, etc)Dengue virus – flavivirus (like West Nile and Yellow Fever)-has 4 serotypes (strains with that produce varying antibodies)-infection with a serotype results in life-long immunity from that serotype-Dengue is known for “immune enhancement”  if infected with a 2nd serotype, the resulting disease can be much worse (greater chance for Dengue Hemorrhagicfever-5 possibilities upon infection:-no symptoms (about 50% experience this)-basic fever (most common!!)-Dengue fever (“break bone fever” – joint pain, nausea, headache, rash)-Dengue hemorrhagic fever-vomiting blood, dizziness, low platelet count-Dengue shock syndrome – weak pulse, low blood pressure, restlessnessnot really effective drugs, mostly treat symptoms with fluids-first discovered in 1600s, today mostly in the Americas and Asia-most deaths are childrenDengue transmission cycle-has a sylvatic (forest) cycle origin – from monkeys-mosquito bites infected monkey, then bites human, transmitting virus to the human-main vector: Aedes aegypti (feeds during day)-occasionally Dengue can pass from female to eggs*temperature and incubation have an inverse relationship*Factors for reemergence of dengue-tropical areas are quickly becoming cities (it’s hard to keep up with the growth – waste management, etc.)-these cities and others are quickly becoming bigger, people are more densely packed-there’s very little vector control in these citiesLecture 11Yellow fever – also transferred by Aedes aegypti (now Aedes albopictus in the US)-brought to US from Africa by slave trade-viral hemorrhagic Flavivirus-monkeys are a huge factor in transmission-kept the Europeans out of Africa for a long time (like malaria)-“yellow jack” – ships were required to raise yellow flag when coming into port to signify that there was fever on board, immediately put into quarantine**there is no yellow fever in Asia, though no one knows for sure whyYellow fever symptoms-some cases are asymptomatic (50% of children)-fever-Toxic Phase 1: high fever, nausea-Toxic phase 2: jaundice, “coffee ground” vomitYellow Fever Transmission-African monkeys not susceptible to disease, South American monkeys die-monkeys maintain the virus in jungles (sylvatic cycle)-people around the jungle get it from mosquitos that have bitten the monkeys (rural cycle/intermediate cycle)-other mosquitos (Aedes aegypti) bite the infected and pass it to people in cities (urban cycle)**yellow fever can’t be controlled since maintained in animal populationsWays to control Aedes aegypti-fogging-indoor residual spraying-treatment of breeding sites -top down approach – government mandates, people do-bottom up – public health officials start campaign, so voluntary sign up-a vaccine does exist, but takes a long time to produce -vaccination is more common in sub-Saharan countriesIn the US-brought with the slave trade-winters were too harsh for it to become endemic-did have large economic impact, people left cities when yellow fever appeared-why did it disappear?-better facilities-better control-window screensYellow fever video-12 days determined between bite and infection$100 in gold offered to soldiers to participate in study, $100 more if became ill-test set up to confirm results-2 cabins:-cabin 1 was screened and filled with stuff from sick patients-no one got sick-cabin 2 had 2 chambers with a screen in between. Infected mosquitos were in onehalf with a few men, and just men in the other half. -those that were in contact with the infected mosquitos got sickLecture 12 Zoonosis – a disease that can go from human to animalReservoir host – maintains the disease, usually don’t experience symptoms (enzootic)Amplifying host – the disease multiplies to high concentrations, host usually gets ill (epizootic)*most arboviruses (arthropod-born viruses) are zoonotic, transmitting between humans and animalsexcept dengue and yellow fever!*humans are usually dead end hosts! They can’t spread the virus to vectors. -arboviruses have greatly increased in recent years, not totally sure whyWest Nile Virus-1st ID’d in Uganda – symptoms in this area were muscle aches, fever, chillsusually permanent immunity after first infection-more recently, epidemics have been seen in horses and birds in addition to humans-it’s a flavivirussymptoms:-80% of cases are asymptomatic-20% develop west Nile fever-severe disease can include: West Nile encephalitis, west Nile meningitis, west Nilemeningoencephalitis-10% fatalBridge vector – transmits disease from animals to humans-Culex pipiens (northern house mosquito) and Culex quinquefasciatus (southern house mosquito) are the main vectors of West Nile-Eastern equine encephalitis virus – a togavirus-has been recorded in humans-transmission cycle goes from swamps to rural agricultural areas-symptoms: most cases are asymptomatic-can get fever, and acute necrotizing encephalitis-human fatality 33%, equine fatality 80-90%-life-long immunity-no specific treatment available, vaccines exist for horses-Western Equine Encephalitis Virus - togavirus-huge epidemic-human fatality 3-15%, mostly children-rural West US is most at risk-symptoms:-usually asymptomatic-sometimes headache and fever occur-13% severe encephalitis-only supportive treatment available, vaccine exists for horses20-50% fatal in horsesSt. Louis Encephalitis Virus – flavivirus-major epidemic in 1933 in St. Louis3 transmission cycles-birds are the reservoir hosts-symptoms:-mostly asymptomatic-some people get fever and a headache-severe cases have a fatality rate of 5-30%-there’s no treatment available-Lacrosse Encephalitis Virus – bunyavirus-transmitted by Aedes triseriatus-reservoir hosts include chipmunks and squirrels-symptoms: -most are asymptomatic-fever occasionally-severe encephalitis -less than 1% fatal-Japanese Encephalitis Virus – Southeast Asia-transmission cyclea lot of Culex species-Culex tritaeniohynchus-many animals transmit-mild cases experience fever and headache-severe cases experience seizures,