Arthropod Bites Flashcards
Lyme Disease Pathogen
•Borrelia burgdorferi: Spirochetes, Highly Motile (cork screw), Gram negative (unusual for spirochete)
Lyme Disease Transmission
•Tick Bite:Lxodes sp.
Lyme Disease Lab Identification
•Blood, CSF, joint fluid: Detection of Abs (serology),Molecular ID
Lyme Disease Clinical manifestations
•Erythema chronicum migrans
–Characteristic skin lesion
–Bulls Eye Rash
•Joint Pain, Fatigue, Neurologic Manifestations, Cardiac Manifestations
Tularemia Pathogen
•Francisella tularensis:Gram neg small coccobacilli,Nonmotile, Intracellular, parasitize reticuloendothelial system
Tularemia Transmission
•Vectors:Ticks (dermacenter tick), mite, lice, flies
•Contact with infected animal (usually rabbits) from skinning them
•Ingestion
-Endemic areas: Northern hemisphere: AK & MO, Russia, Scandinavia, Spain
Tularemia Lab Identification
- Flourescents, serology
* NO CULTURE—high risk of infection
Tularemia Clinical Manifestations
- Variable depending on route of transmission
- Ulceroglandular is MC form
- Lymphatic spread
- Painful regional lymph nodes
- Blood invasion
- +/- lungs, GI involvement
- Formation of granulomatous nodules around reticuloendothelial cells
- +/- rash
Tularemia resivor
Rodents
Rocky Mountain Spotted Fever Pathogen
•Rickettsia rickettsii: Small gram-negative,Must live inside of another cell, Requirement for co-enzyme A, NAD, ATP,Non-motile,Obligate intracellular parasite.
Rocky Mountain Spotted Fever Pathogenisis
- Attachment of tick to host—inject in host blood–uses membrane proteins OMPA and OMPB to gain entry
- Survives in cystol and nucleus of host cell (unusual)
- Disseminate through lymph and blood
- Enter vascular endothelial cells—foci of infection
- Spread to distant endothelial and smooth m. cells→ increased vascular perm.–> edema, hypoproteinemia and dec perfusion to organs
Rocky Mountain Spotted Fever Lab identification
- Serology, direct florescence, PCR
- Dont culture, won’t grow.
Rocky Mountain Spotted Fever Clinical Manifestations
- Fever, headache, rash
- Lymphadenopathy
- Anemia, atypical lymphocyte
Rocky Mountain Spotted Fever demographic
•South Atlantic & Midwestern states
Rock Mountain Spotted Fever Transmission
- Dog Tick: Dermacentor variabilis-Eastern US
- Wood tick: D. androsoni-West
- Lone Star tick: Amblyomma americanum-South West
Rickettsia Prowazekii Clinical Manifestations
- Sudden onset of fever, chills, headache, arthralgia/myalgia
- Rash 7 d later on trunk that spreads to extremities
- Complictions: Myocarditis, stupor, delirium, mortality 70%
- Some typhus connection?
Rickettsia Prowazekii Diagnosis and control
Diagnosis: Clinical, serology
Control: Killed typhus vaccine
Human Ehrlichiosis & Anaplasmosis Pathogen
- Infect leukocytes
- E. chaffeensis
- E. ewingii:Vector: Lone Star tick,Reservoir: White tailed deer,SE, Mid‐Atlantic, South Central US
- A. phagocytophilum:Vector: Deer and dog ticks,Reservoir: small mammals,Wisconsin, Minnesota, Connecticut
Human Ehrlichiosis & Anaplasmosis Features
- Tick‐borne: peak infection May‐August obligate intracellular
- Obligate intracellular, Gram negative( but No LPS or PG, weird!)
- Replicate in membrane‐bound compartments inside host cells
- 2 forms: DC (dense‐cored) (infectious form) and RC (reticulte cells)
Human Ehrlichiosis & Anaplasmosis Clinical Manifestations
- Resembles Rocky Mountain Spotted Fever, but rash is rare
- Symptoms 5‐10 days after tick bite:Fever,headache, malaise, confusion,Nausea & vomiting, abdominal cramps, myalgia
- 20% of cases: rash
Human Ehrlichiosis & Anaplasmosis Lab ID
Direct exam of Giemsa‐stained peripheral blood, Serologic testing,
-Culture is possible, but rarely attempted
Dengue Virus Genome and structure
Flaviviridae; enveloped ss(+)RNA virus
Dengue Virus Vector
- Aedes aegypti mosquito
- tropics worldwide, spreading to the US
Dengue Virus resivor
humans and primates
Dengue Virus Clinical features
Incubation period: <1 week
Symptoms: High fever + two or more of the following:
o Severe headache, eye/joint/muscle pain (“break‐bone” fever)
o Non‐pruritic rash, low white cell count
o Mild bleeding (e.g., nose, gum bleed, petechiae, easy bruising)
o Lifelong immunity is generated in the host
Dengue Virus Control
Vector control only; no vaccine is currently available
Dengue Hemorrhagic Fever
-4 Sterotypes (DV1 through 4): Get sick with Dengue fever 2–recover–get sick with DF 4–at risk for hemorrhage
Dengue Hemorrhagic Fever Test
Serology, PCR, blood work
Dengue Hemorrhagic Fever Clinical Manifestations
-1) 2‐7 d fever; 2) Hemorrhages; 3) Thrombocytopenia (low platelet); 4) Increased vascular permeability
-Dengue Shock Syndrome (DSS: rapid pulse, cold, clammy skin, hypotension,
circulatory failure)
Up to a 10% fatality rate
Yellow fever Genome/Structure
-Flaviviridae (Dengue, West Nile), (+)ssRNA enveloped viruses
Yellow fever vector and risk groups
- Aedes aegypti mosquito
- infants and elderly
Yellow fever Prevention
Live, attenuated vaccine
Yellow fever diagnosis
-Clinically: Fever, followed by possible signs
of jaundice within 2 weeks
-Labs: Elevated bilirubin; urinalysis
(proteinuria/albuminuria)
Yellow fever Test
PCR, viral antigen detection
