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MBIO 4300 Midterm Study Guide: Infectious Diseases in Latin America, Exams of Biology

Fayetteville State University (FSU)Biology

This comprehensive study guide covers key concepts related to infectious diseases prevalent in latin america, focusing on dengue, zika, yellow fever, and chikungunya viruses. It provides detailed information on their transmission, symptoms, diagnosis, treatment, and prevention strategies. The guide also explores the impact of socioeconomic factors, climate change, and healthcare access on disease spread. It is a valuable resource for students studying infectious diseases, public health, and tropical medicine.

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2024/2025

Available from 04/16/2025

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MBIO 4300 Midterm.
Latest Updated Exam Study Guide
2025/2026.
100% Certified by Expert
Physical factors the affect infectious diseases - ans- Access to affordable food
- Access to proper housing
Societal factors the affect infectious diseases - ans- Clean water
- Contact with vectors (animals)
- Access to health care
- Urbanization (increase in population density)
Cultural and religious factors the affect infectious diseases - ans- Traditional medicine
- Food prep methods
- Cultural practices that promote poor practice
Political factors the affect infectious diseases - ans- Healthcare funding and access for
citizens
- Failure to acknowledge issues with diseases
- Conflict
Why is healthcare overlooked by some governments - ans- Developing nations often
prioritize military development rather than healthcare
How does population size effect disease spread - ans- Small isolated communities are hit
hardest due to lack of immunity
- Density increase leads to easier spread
How are zoonotic infections contracted - ans- Human engagement with animals
How does climate change affect disease spread - ans- Increasing temp allows vectors of
infection to thrive
How does deforestation affect disease spread - ans- Increased opportunity for larvae
- Increase number of vectors
How did air travel contribute to spread of diseases - ans- People of have contracted the
pathogen could be asymptomatic and board planes to places that are not infected
How does poverty affect contraction of diseases - ans- Vaccines are not always affordable
- Clean water is not available
- Poor sanitation/living conditions
How can education help prevent spread - ans- Understanding how a diseases spreads can lead
to precautionary measures
How does a tropical environment affect spread - ans- Allows for survival of vectors
- High amount of precipitation also aids
Why is health care provider retention a problem in Latin America - ans-More and more
professionals leaving which results in lack of trust
How does socioeconomic discrimination affect - ans- Stigma can lead to less testing resulting
in undertesting
- Also results in lack of proper healthcare
Why are some diseases labeled as forgotten diseases - ans- Lack of prioritization of illnesses
that effect the poor
What is Dengue virus - ans- DENV
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Download MBIO 4300 Midterm Study Guide: Infectious Diseases in Latin America and more Exams Biology in PDF only on Docsity!

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Physical factors the affect infectious diseases - ans- Access to affordable food

  • Access to proper housing Societal factors the affect infectious diseases - ans- Clean water
  • Contact with vectors (animals)
  • Access to health care
  • Urbanization (increase in population density) Cultural and religious factors the affect infectious diseases - ans- Traditional medicine
  • Food prep methods
  • Cultural practices that promote poor practice Political factors the affect infectious diseases - ans- Healthcare funding and access for citizens
  • Failure to acknowledge issues with diseases
  • Conflict Why is healthcare overlooked by some governments - ans- Developing nations often prioritize military development rather than healthcare How does population size effect disease spread - ans- Small isolated communities are hit hardest due to lack of immunity
  • Density increase leads to easier spread How are zoonotic infections contracted - ans- Human engagement with animals How does climate change affect disease spread - ans- Increasing temp allows vectors of infection to thrive How does deforestation affect disease spread - ans- Increased opportunity for larvae
  • Increase number of vectors How did air travel contribute to spread of diseases - ans- People of have contracted the pathogen could be asymptomatic and board planes to places that are not infected How does poverty affect contraction of diseases - ans- Vaccines are not always affordable
  • Clean water is not available
  • Poor sanitation/living conditions How can education help prevent spread - ans- Understanding how a diseases spreads can lead to precautionary measures How does a tropical environment affect spread - ans- Allows for survival of vectors
  • High amount of precipitation also aids Why is health care provider retention a problem in Latin America - ans-More and more professionals leaving which results in lack of trust How does socioeconomic discrimination affect - ans- Stigma can lead to less testing resulting in undertesting
  • Also results in lack of proper healthcare Why are some diseases labeled as forgotten diseases - ans- Lack of prioritization of illnesses that effect the poor What is Dengue virus - ans- DENV

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  • +ssRNA arbovirus
  • Immunity of one does not carryover to others How is Dengue spread in Latin America - ans- Aedes spp. mosquitos
  • Prevalent in tropical areas What is the best way to prevent Dengue spread in Latin America - ans- Vector control
  • Chemical treated mosquito nets How do mosquitos inoculate humans with Dengue in Latin America - ans- Immune cells are recruited and macrophages become infected
  • Tissue damage when immune system activates
  • Migration of infected cells in lymphatic fluid leads to viremia
  • Mosquitos take blood from infected allowing them to infect other humans What are some of the symptoms of Dengue in Latin America - ans- Flu-like
  • High fever (40), headache, myalgia, bone and joint pain, swollen glands
  • Some develop rash What are some of the more rare symptoms of Dengue in Latin America - ans- Break bone infection
  • Saddleback fever can occur, high temp to low temp back to high What are the clinical representation of Dengue in Latin America - ans- Neutropenia (neutrophils)
  • Lymphocytosis (lower than normal lymphatic cells)
  • Thrombocytopenia (thrombocytes decrease) What symptoms are common in untreated dengue - ans- Hemorrhagic fever due to low immunity
  • Organ failure due to drop in blood pressure What is dengue vaccine and how is it administered - ans- Tetra valent live attenuated (dengvaxia)
  • 3 doses 6 months apart
  • Given to 9 - 45 yr old's Can the dengvaxia be given to anyone in age range - ans- Only given to people that already have been infected
  • Antibody dependent enrichment What is antibody dependent enrichment (ADE) and why is it a concern for people who have not been infected - ans- Antibodies produced do not neutralize virus but facilitate infection How did humanized mice help with understanding diseases - ans- Able to emulate human immune system to a degree
  • Allowed us to measure cytokine levels
  • Indicated that mosquito saliva alone can induce immune responses as long as 7 dats after bite Characteristics of zika virus in Latin America - ans- Enveloped, +ssRNA
  • Transmitted by mosquitos (aedes spp.)

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How can we prevent trans-placental transmission of Zika - ans- Men returning from Zika countries use condoms for 3 months

  • Woman use precautions for 2 months Characteristics of yellow fever in Latin America - ans- Enveloped, +ssRNA virus of flavivirdae family
  • Spread by Aedes spp What are the 3 cycles of yellow fever - ans- Sylvatic (no human)
  • Savannah (human or not)
  • Urban: from people who return to urban settings after being in jungle (human to human) When and how long are humans infectious for with yellow fever - ans- Shortly prior to fever onset and lasts for 5 days
  • Needle-stick and transfusion is possible What does 3 phases of yellow fever infection in Latin America - ans1. Infection
  1. Remission
  2. Intoxication What is the infection step like in yellow fever - ans- Fever, headache, jaundice, nausea, fatigue and myalgia
  • Jaundice What is the Remission step like in yellow fever - ans- Most patients resolve the infection entirely during this period
  • Small proportion of patients this only lasts 2-24 hours What is the intoxication step like in yellow fever - ans- Severe hemorrhagic diseases
  • Impacts liver (hepatitis) and kidneys fail
  • 50% mortality rate within one week of onset with severe disease Why is early diagnosis of yellow fever difficul - ans- Closely resemble other infections in area
  • Use PCR on blood on urine samples
  • ELISA can detect antibodies but flavy increases false positives Are there any vaccines for yellow fever - ans- Live attenuated vaccine 80% effective
  • Given 10 days ahead of travel
  • 99% within 30 days
  • Provides lifelong immunity How are yellow fever vaccines made - ans- Made by serial passage What causes Chikungunya Virus in Latin America - ans- +ssRNa
  • Arbovirus
  • Togaviridae family
  • Alphavirus Old world VS new world Chikungunya virus - ans- Old: Severe polyarthralgia
  • New: encephalitis How is Chikungunya transmitted in Latin America - ans- Mosquito Aedes genus

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  • Infectious after a few hours for the rest of its life What are some symptoms of Chikungunya - ans- Fever and extreme arthralgia
  • Myalgia, joint swelling, fatigue, rash
  • Sometimes neurological symptoms, eye issues How do you treat Chikungunya virus - ans- No virus specific treatment exists
  • NSAIDS How to diagnosis Chikungunya virus - ans- ELISA
  • PCR How to prevent Chikungunya virus - ans- Vector control What does U=U mean - ansUndetectable = Untransmittable What causes HIV in LAC - ans- Enveloped ssRNA
  • Retroviridae
  • Lentivirus genus How is HIV transmitted - ans- Blood
  • Sexual activates
  • Mother to child across placenta How to treat HIV - ans- Antivirals reduce viral load
  • Which results into U=U What is the acute phase of HIV - ans- Develops few days after infection
  • Asymptomatic What is stage 1 HIV - ans- CD4 cell count at least 500 cells of blood account at least 29% of lymphocytes What is stage 2 HIV - ans- CD4 cell count is between 200 and 499 cells of blood account at least 14-28% of lymphocytes What is stage 3 HIV - ans- AIDS
  • CD4 cell count drops and less 14% of lymphocytes Which groups are at risk of HIV - ans- MSM
  • Sex workers
  • Transgender woman
  • IV drug user
  • Migrants
  • Incarcerated What is Dolutegravir and is it administered - ans- Integrase inhibitor
  • Used for all groups including pregnant women
  • Taken once daily with decreased side effects What PrEP and is it administered - ans- Pre-exposure prophylaxis
  • Truvada pill (nucleoside inhibitors of reverse transcriptase)
  • Taken by individuals who are high risk Downsides of taking PrEP - ans- Requires regular testing and only by HIV negative patients
  • If not taken properly increases chances

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How is leptospirosis transmitted? - ans- Cuts that contact water or soil contaminated with urine

  • Ingestion from contaminated water Common symptoms of leptospirosis - ans- Fever headache
  • Myalgia of LOWER CALF MUSCLE Severe symptoms of Leptospirosis - ans- Weil's syndrome (jaundice, renal failure, liver diseases myocarditis and hemorrhage)
  • Meningitis and encephalitis
  • Pulmonary hemorrhage and respiratory failure What is MAT when diagnosing Leptospirosis - ans- Microscopic agglutination test
  • Mix patient serum with live suspension of Leptospira antigen and look for agglutination What is the treatment for leptospirosis - ans- Prophylactic doxycycline given to people who will be at high risk
  • Early antibiotic therapy with penicillin or cephalosporins will hamper severe disease Is there a vaccination for leptospirosis - ans- Yes but only given to dogs
  • Humans is to complex due to so many serovars Where is Lymphatic Filariasis endemic - ans- Haiti
  • Guyana
  • Dominican Republic
  • Brazil How is lymphatic filariasis transmitted? - ans- Nematodes of Filariodidea family
  • Microfiliareae can be picked up by mosquitos of the Culex, Aedes and Anopheles geneus How does Lymphatic Filariasis effect the body from a clinical stand point - ans- Adult filariodidea nest in lymphatic vessels causing dysregulation of immune system
  • Blocks flow due to tangled structure causing lump
  • Live for 10 yrs Symptoms of acute infection of Lymphatic Filariasis - ans- Episodes with localized inflammation
  • Occur due to immune response to parasite or 2 degree infection due to dysregulated immune function
  • Symptoms of chronic infection of Lymphatic Filariasis - ans- Lymphedema (swelling due to accumulation of lymphatic fluid)
  • Elephantiasis (thickening of skin and soft tissues) in breasts and genital tissues
  • Hydrocele: fluid filled pocket in testicle Treatment for Lymphatic Filariasis - ans- Ivermectin
  • Albendazole
  • Diethylcarbamazine
  • Kills larva but not adult How is treatment for Lymphatic Filariasis administered - ans- MDA (mass drug administration)

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  • 2 pill regime with albendazole and diethylcarbamazine
  • Given to adults once a year and children twice a year What are alternative treatments for Lymphatic Filariasis - ans- Elevation of affected limbs
  • Exercise to circulate fluid
  • Surgery for hydrocoele How to diagnose Lymphatic Filariasis - ansMicroscopic examination of blood samples What causes Leishmaniasis and how is it transmitted? - ans- 20 spp. of Leishmania parasite
  • Spread by bite from phlebotomine sand flies (active in evening and night) What are the types of Leishmaniasis and where are they found - ans- Cutaneous: Brazil and Columbia
  • Visceral (organs): Brazil
  • Mucosal: Brazil, Bolivia and Peru
  • Post-kala-azer dermal How does Leishmaniasis infect the body - ans- Infects macrophages (aids tissues with immunity)
  • Macrophage lysis releasing amastigotes that infect naïve macrophages
  • Sand flies pick up amastigotes that proliferate forming infectious promastigotes Symptoms of cutaneous Leishmaniasis - ans- Skin sores after months
  • Macular (red), papular (puss) or ulcerated (red, puss and ooze)
  • Dermal macrophages
  • Slow healing
  • Severe scars Symptoms of visceral Leishmaniasis - ans- Can occur years after
  • Fever
  • Weight loss
  • Decreased blood cell counts
  • Swelling of liver and spleen
  • Damaging to immune system high risk of secondary infection Symptoms of mucosal Leishmaniasis - ans- Infects mouth/nose
  • Can occur years later How can we diagnose Leishmaniasis - ans- ELISA
  • PCR to detect parasite DNA
  • Microscopic analysis of samples from ulcers or bone marrow How is Leishmaniasis treated - ans- Pentavalent antimonials
  • Amphotericin B or liposomal amphotericin B How is treatment of Leishmaniasis administered - ans- Amphotericin B or liposomal amphotericin B
  • Need to be given daily via parenteral route for min of 3 weeks Side effects of Leishmaniasis treatment - ans- Terrible toxicity associated with poor compliance

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  • Trained healthcare providers
  • private sector used by impoverished
  • Conflict What causes Malaria - ans- Plasmodium falciparum What transmits Malaria - ans- Anopheles gambiae mosquito
  • Blood
  • Mother to child How does Malaria effect the body - ans- Sporozoite enter liver forming schizont
  • Schizont ruptures and parasites enter blood (parasetemic)
  • Infects RBC Symptoms of uncomplicated Malaria - ans- Headache
  • Fever
  • Chills
  • Sweating
  • Flu-like
  • Hepatomegaly (large liver)
  • Jaundice
  • Splenomegaly (large spleen) How often do Malaria attacks occur - ans- Every 2 days till plasmodium has died or left 3 stages of Malaria - anscold, hot, sweating Symptoms of complicated Malaria - ans- Cerebral when infected RBC stick to non infected RBC and to small blood vessels
  • Rosetting, blocks blood flow to the brain leading to hypoxia
  • Organ failure due to liver and kidney damage
  • Rupture of spleen
  • Severe anemia due to rupture of RBCs How is Malaria diagnosed - ans- Microscopy with giemsa stain Treatment for Malaria - ans- Artemisinin-based combination therapy (ACTs)
  • Damages plasmodium proteins killing cells
  • Resistance builds Preventative treatment for Malaria - ans- Prophylactics
  • Chloroquine, doxycycline, primaquine, mefloquine What causes Tuberculosis - ans- Mycobacterium Tuberculosis
  • Mycobacterium africanum How is tuberculosis transmitted? - ans- Small infectious droplets
  • Only few bacterial cells are most effective How does Tuberculosis effect the body - ans- When bacterium reach alveoli it is phagocytosed by macrophages
  • If macrophages does not destroy bacterium it will multiply eventually moving to other tissues via lymphatic system or blood

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  • Immune cells are used at site of infection forming a granuloma
  • Granuloma is where MTB replication occurs while other MTB cells are dormant What is latent TB - ans- Cells are actively replicating are destroyed by the immune response
  • Infected macrophages can undergo apoptosis leading to engulfment by another macrophage
  • It can also become necrotic
  • Non-communicable
  • Asymptomatic and unable to spread bacterium
  • Controlled by IMS What is symptoms active Tuberculosis - ans- Pulmonary TB - > communicable
  • Productive cough lasts for 2 weeks
  • Thick, cloudy mucus
  • Sputum may contain blood How is TB diagnosed? - ans- Mantoux test: injection of tuberculin under skin in forearm, read 48 - 72 hrs later, size of welt develops indicates likelihood of TB, induration must be measured
  • If active acid fast stain on sputum smear and left to grow for 24 hrs
  • Chest X-ray and CT scan to look for calcified lesions form past infections What is extra pulmonary TB? - ans- Involves organ systems outside of the respiratory tract
  • Can occur with pulmonary TB

Treatment for latent Tuberculosis - ans- 1 medication, isoniazid taken for 9 months

  • 2 medications, rifampin and isoniazid for 3 months Treatment for active Tuberculosis - ans- 4 medications taken for 2 months (rifampin, isoniazid, ethambutol and pyrazinamide
  • 2 medications for another 4 months (isoniazid and rifampin) What is multi-drug resistant TB resistant to (MDR-TB) - ans- Resistant to rifampicin and isoniazid
  • Treated with second line drugs What is extensively-drug resistant TB resistant to (XDR-TB) - ans- Resistant to rifampicin, isoniazid and second line drugs
  • Needs much longer therapy What is the BCG vaccine - ans- Bacille Calmette-Guerin vaccine for TB using live attenuated strain of M. bovis
  • Given in single dose
  • Limited effectiveness
  • Given to high risk groups with intent to not prevent infection but prevent severe TB Is there a vaccine for pneumonia - ans- Yes but they are vaccines for other conditions that worl
  • H. influenza
  • Steptococcus - pneumoniae

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Where is African sleeping Sickness common - ans- Sub-Saharan Africa How does African sleeping Sickness enter the body - ans- When tse tse fly take a blood meal

  • Parasite is present in saliva What are some other froms of spread of African sleeping Sickness - ans- Blood transfusion
  • Blood contact
  • Mother to child
  • Sex What is the most common diagnosed form of African sleeping Sickness and which sub- species of is responsible - ans- Slow progressing
  • West and central Africa
  • Gambiense What subspecies causes rapid progressing African sleeping Sickness and where - ans- Rhodesience
  • East and south Africa Is African sleeping Sickness fatal - ans- Only when untreated Unique symptoms of African sleeping Sickness stage 1 - ans- Painful chancre at infection site How does parasite in African sleeping Sickness replicate and how does it spread in body - ans- Binary fission at site of bite
  • Migrates into blood via lymphatic vessels What happens once parasite in African sleeping Sickness migrates to lymphatic vessels - ans- Haemolyphatic stage of infection What symptoms are present during the haemolyphatic stage of African sleeping Sickness - ans- Enlarged lymph nodes
  • Winterbottom's sign (lymphaenopathy along the chain of cervical nodes to the back of the neck)
  • Fever What happens when parasite of African sleeping Sickness crosses the BBB - ans- Meningoencephalitis What symptoms occur during 2nd stage of African sleeping Sickness - ans- Behavioral changes
  • Slurred speech
  • Confusion/poor concentration
  • Coordination disturbance
  • Long sleep during day
  • Inability to sleep at night How is African sleeping Sickness diagnosed - ans- Lymph node samples
  • Lumbar puncture to evaluate cerebrospinal fluid How does the parasite in African sleeping Sickness avoid immune detection - ans- Typanosomes vary glycoprotein expressed on surface
  • Only 1 active at a time

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  • Able to quickly remove and insert another protein variant
  • Avoids antibody detection What is the treatment for first stage of African sleeping Sickness - ans- Pentamidine for gambiense subspecies
  • Suramin used to treat rhodesciencse What is the treatment for stage 2 African sleeping Sickness - ans- Melarsoprol
  • Eflornithine
  • Nifurtimox
  • Much more harder to treat when CNS What is severe diarrheal disease defined as - ans- More than 10 watery stools per day What is moderate diarrheal disease defined as - ans- More than a few less than 10 watery stool a day What is mild diarrheal disease defined as - ans- Few watery stools a day How long does acute watery diarrhea last - ans- Hours to days What is dysentery diarrhea - ans- Bloody diarrhea How long does persistent diarrhea last - ans>14 days What are common bacterial causes of diarrhea - ans- Vibrio cholerae
  • E.coli What is a common viral cause of diarrhea - ans- Rotavirus What are common parasitic causes of diarrhea - ans- Cryptosporidium parvum and Hominis
  • Giardia lamblia and intestinalis What are different ways diarrheal diseases are spread - ans- Person to person
  • Zoonotic to person
  • Contaminated water How does an undernourished body relate to severe diarrheal diseases - ans- Poorly maintained immune system
  • Further undernourishment
  • Results in stunting What is ORS treatment for diarrheal diseases - ans- Oral rehydration salts
  • 90% effective in reducing mortality How does iCCM help with diarrheal diseases - ans- Integrated community case management
  • Trains healthcare providers on treating with ORS and zinc What is fluid curtailment and how does it affect diarrheal diseases - ans- Less fluid given to children with diarrhea
  • Occurs due to misinformation and beliefs
  • Leads to further dehydration What are the 3 local beliefs of diarrhea in South Africa - ans- Occurrence due to natural causes
  • Occurrence due to supernatural causes
  • Occurrence due to infectious agent (best for proper treatment)

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How is HIV-2 different - ans- Less transmissible

  • Lower viral loads, higher CD4 cell counts but progression occurs
  • Lower immune activation What are the main barriers that prevent people receiving AVR for HIV - ans- High transportation cost
  • ARV cost and long term
  • Side effects of ARV decreases compliance What is VERTICLE Transmission? - ans- from mother to child
  • Placenta
  • Breast feeding How does circumcision help with HIV - ans- Reduced infection risk by 60% What are some factors that contribute to infectious diseases in Asia - ans- Population density
  • Lack of surveillance programs
  • Tropical climates
  • Mobility between countries
  • Higher birth rates in lower income countries How do animals in Asia contribute to ID - ans- Animal trade
  • Migration patterns
  • ^ deforestation = ^ in human and animal interactions
  • Livestock farmed at home How does culture in Asia contribute to ID - ans- Delicacies sometimes require raw foods
  • Vietnam tradition to consume raw pig blood and and uterus Why is antibiotic resistance a bigger issue in Asia - ans- Misuse by healthcare workers
  • Over the counter Antibiotics available
  • Poor microbio labs What causes Japanese encephalitis? - ans- Flavivirus
  • Related to YF, WNV and Dengue What is the main vector of Japanese encephalitis - ans- Mosquitos of Culex genes Why is Japanese encephalitis considered a disease of children - ans- Adults protected from memory response Why does Japanese encephalitis transmission increase in rainy season - ans- Lots of standing water making breeding ground for mosquitos What other forms of transmission for Japanese encephalitis exist not including humans - ans- Pig to pig
  • Bird to bird Initial symptoms of Japanese encephalitis - ans- Fever, headache and vomiting Severe symptoms of Japanese encephalitis - ans- Psychiatric changes
  • Seizures
  • Mobility issues
  • All of above is encephalitis

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How does Japanese encephalitis mimic Parkinson's - ans- Facial tremors due to involvement of basal ganglia

  • Sudden onset is different, Parkinson's takes time What happens when motor neurons are damaged during Japanese encephalitis infection - ans- Flaccid paralysis
  • Life long neurological effects What can we use to test for Japanese encephalitis - ans- Antibody testing
  • MRI for neurological changes
  • Evaluate chemistry of CSF What is the issue with antibody testing of Japanese encephalitis - ans- Cross reactivity with other flavivirus
  • False + Why is timing of Ab testing important with Japanese encephalitis - ans- Too early, Ab not present
  • Too late and class switching occurs What is evaluated in MRI for Japanese encephalitis - ans- No radiation
  • Presence of thalamic lesions What is evaluated in CSF for Japanese encephalitis - ans- Glucose normal
  • Elevated proteins due to Ab
  • Elevated leukocytes (indication of infection) What are the 2 types of vaccines for Japanese encephalitis and which is best - ans- Live attenuated (best)
  • Inactivated How is inactivated vaccine for Japanese encephalitis administered - ans- 2 doses given 1 month apart
  • Recommended booster within a year or 2 of receiving vaccine
  • Used in Na, AUS and Eu Where is the live attenuated vaccine for Japanese encephalitis used - ans- China
  • India
  • Sri Lanka
  • Thailand What causes leprosy in Asia - ans- Mycobacterium leprae What is the issue with culturing leprosy in Asia - ans- Long generation times of 13 days
  • 5 year incubation period Why is it hard to diagnose leprosy in Asia - ans- Symptoms can develop anywhere from 6 months to 20 years after infection What temperature does leprosy in Asia like - ans- Colder temps
  • Similar to that on nose and fingers Where does leprosy in Asia infect - ans- Mucosal sites and skin
  • Can involve eyes, testes, bone and muscle

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Why is salmonella enterica Typhi an issue when systemic - ans- Gram - lipopolysaccharide is potent immune activator

  • Increases vasodilation
  • Decreased blood pressure
  • Results in septic shock What causes paratyphoid - ans- Salmonella enterica paratyphi A How is typhoid spread - ans- Fecal/oral route
  • Indirect person to person
  • Can be shed asymptomatically Where is typhoid commonly found - ans- South Asia due to rapid urbanization and poor water and sewage treatment
  • Open defecation is common practice What happens to a small % of recovered patients post-infection - ans- 10% will continue to shed S. Typhi for 3 months
  • Smaller % will become carriers shedding bacterium in stool for prolonged periods of time (>1 yr) What are common sources of typhoid - ans- Non-bottled, non-boiled water
  • Raw shell fish and street vendors
  • Raw fruits that cannot be peeled
  • Unpasteurized dairy Symptoms of typhoid - ans- Diarrhea (constipation)
  • Rash on trunk
  • Swollen stomach
  • Very high fever
  • Vomiting
  • Blood in stool (damage to intestinalis lining) How to diagnose typhoid - ans- Blood culture
  • Poor sensitivity (antibiotic use, low level bacteremia) What is the wWdal test for typhoid - ans- Looks for 4 fold increase in antibody titer/serology between acute and convalescent stage of infection What antibodies are detected for titer of typhoid - ans- H and O for those antigens
  • Suspensions of bacterial serotypes typhi and paratyphi treated for only H and O antigens What is the Widal test followed by for typhoid diagnosis - ans- Culture from blood, urine or stool What is the issue with the Widal test - ans- Cross reactivity with other infectious organisms
  • Over diagnosis of typhoid fever allowing for resistance to be built due to incorrect use of antibiotics How does typhoid become lethal - ans- Blood borne, leading to GI bleeds and perforation of intestines causing peritonitis
  • Can cause encephalitis

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How can antibiotic resistance be avoided for typhoid - ans- Combination therapy What are the 2 older vaccines with questionable efficacy for typhoid - ans1. Oral vaccine Ty21a (taken in capsules once a day for 3 days )

  1. Intramuscular injection single dose vi polysaccharide vaccine
  • Not given to children <2 yrs old
  • Protection short-lived requiring boosters every 3 years What is the new more effective vaccine for typhoid - ans- Novel vaccine made in India 2018
  • Better immunogenicity
  • Conjugated vaccine Typbar-TCV
  • Does not protect against paratyphi
  • Only in Nepal and India What is typhus caused by - ans- Rickettsia prowazekii
  • Obligate intracellular organism
  • Infects endothelial cells lining blood vessels How is typhus spread - ans- Pediculus humanis (lice)
  • Louse collects rickettsia when taking a blood meal
  • Feces or crushed louse can be rubbed into bite wounds Where do typhus vectors like lice prefer to be - ans- Cooler temps in mountainous regions Where does rickettsia multiply - ans- In gut of louse, lysing vector
  • Viable in dead louse for prolonged periods Where does rickettsia replicate in human - ans- Cytoplasm of endothelial cells
  • Prevents phagosome and lysozyme
  • Endothelial cell ruptures releasing rickettisal cells to plasma What happens when lysis of endothelial cells occurs - ans- Damage to vasculature
  • Blood loss
  • Protein loss
  • Shock and multiple organ failure Symptoms during early typhus infection - ans- Sudden high fever for 2 weeks
  • Chills
  • Severe headaches
  • Weakness
  • Exhaustion How do symptoms of typhus change after 1 week - ans- Dark colored macular rash develops on upper trunk, spreads throughout body What makes diagnosis of typhus difficult - ans- Misinterpreted as leptospirosis, typhoid fever, rickettsia, dengue and many others What is Brill-Zinsser disease - ans- Occurs in typhus patients yrs after infection
  • Never cleared initial infection becomes latent
  • Presents as a less severe form of typhus Can Brill-Zinsser disease spread typhus - ans- Yes