Tick-borne Illnesses Flashcards
3 kinds Tick-borne pathogens
Bacteria (Borrelia), Euk. parasites (Babesia), Viruses (TB encephalitis virus)-Europe
3 kinds ticks carrying disease in US
Ixodes scapularis (in MN, East Coast, southeast) Ixodes pacificus (West Coast) Amblyomma americanum (southeast)
Ixodes scapularis carries 3 diseases
Lyme disease, Anaplasmosis, Babesiosis (all growing in incidence and range), specifically in MN (note, w/ CC, expanding into Canada)
Tick life cycle
Larva - Hatch from eggs, lack pathogen → BLOOD MEAL → Nymph - taken one blood meal, may have acquired pathogen → Adult - multiple blood meals, may have acquired pathogen
nymph and adult (female) transmit disease
Main reservoir host of Ixodes scapularis
White footed mouse
deer only fed on by adult ticks
Onset of illness most frequently when
may through september
What to do if find attached tick?
Try to estimate duration of tick-attachment (bacterial transmission takes >24 hrs, parasites even longer, viruses shorter time? → NOTE: This number is kind of made up, look for new research)
Remove tick with forceps or gloved fingers
Clean area with disinfectant
No value in submitting tick for analysis
Observe bite site for 30 days (for characteristic rash)
Seek medical assistance for febrile illness
Disease Prevention
DEET-repellent on skin, Permethrin on clothing, light colored clothing, socks outside pants, daily inspection of skin and removal of ticks
Where are ticks
@ Interface between woodlands/grassy areas - Ticks in grassy areas, hosts in woods
Cause of Lyme Disease
Borrelia burgdorferi
Acute stage sometimes presents with characteristic rash, Arthritis-like symptoms in chronic stages
Lyme Disease
B. burgdorferi characteristics/virulence factors
Fastidious, micro-aerophilic spirochaete ,Grows best at 32C on BSK medium
Flagella - move in corkscrew manner
Longer than they are wide (20-30 micrometers, 0.3 wide)
Surface proteins are host-dependant
OspA in tick, OspC in human
Can disseminate widely in mammal
Remain in midgut of insect until blood meal, then migrate to salivary glands
Various species of BB
Various species
B. burgdorferi sensu lato (worldwide)
Bb sensu stricto (USA) → LD
B. garinii, B. afzelii, B. miyamotoi
Cause Human Granulocytic Anaplasmosis (HGA) - transmitted by those I. scapularis and pacificus
Anaplasma phagocytophilum
Group of bacteria spread by arthropod vector:
Require living cell for growth – obligate intracellular parasite.
BUT have metabolic enzymes, cell walls, and utilize O2.
extremely small (~0.5 μm in diameter)
Gram negative
Often pleomorphic in shape
Rickettsia (barely bacteria)
2 species of rickettsia
A. phagocytophilum, Ehrlichia chaffeensis
Features of A. phagocytophilum
Replicates in midgut epithelial cells – tick
Some bacteria make it to the salivary glands which are the cells that will be transmitted to initiate mammalian infection
Colonizes neutrophils – mammalian system
In neutrophils, hijacks endocytic pathway to make a vacuole in which to replicate
Morulae = form intracytoplasmic cluster of bacteria
A. phagocytophilum replicated in __________ in ticks
midgut epithelial cells
From which area in tick are cells transmitted to initiated mammalian infection (a. phagocytophilum)
salivary glands
What do A. P. colonize in mammals?
Neutrophils –> make vacuoles in which to replicate
Form intracytoplasmic cluster of bacteria
morulae (i.e. A. phagocytophilum)
BB surface proteins
OspA in tick
OspC in humans
Need to switch before transmission
Responsible for Rocky Mountain Spotted Fever
Rickettsia rickettsii
How are RMSF/RR transmited?
different tick, transovarian (through eggs)
What does RR do when it gets in body? (where go and how to replicate)
Does not require a specialized human cell to infect
Spread through bloodstream, infect vascular epithelial cell
Replicate in cytosol of cell, not in a vacuole
Cause of Babesiosis/type of pathogen
Babesia spp - parasite (i.e. microti)
Babesia = _______ paracite
apicomplexan, unicellular
Humans are ______ hosts, sexually reproduce in _________ (Babesia)
dead-end hosts,
mice erythrocytes
Virus example of tickborne disease
tick-borne encephalitis (TBEV) in Europe, Asia, former USSR
Related Flaviviridae family virus Powassan (POW) in US (rare)
Flaviviruses are (mostly) linear and_______, and are transmitted by the bite ________, primarily mosquitoes and ticks.
Flaviviruses are (mostly) linear and single stranded, and are transmitted by the bite arthropods, primarily mosquitoes and ticks.
Lyme Disease Presentation depending on stage
Early localized (w/in 30d) - Skin
Early disseminated (days to weeks) - Skin, Cardiac, Neurologic
Late disease (months to years) - Cardiac, neurologic, musculoskeletal
Early Signs and Symptoms
Fever, chills, HA, fatigue, muscle/joint aches and swollen lymph nodes
EM rash in 70-80%
Lyme Carditis
(~1%) → 2nd or 3rd degree AV block - may require temporary pacing
Neurologic Lyme
(10-15%) → Bell’s Palsy (CN VII paralysis), Meningitis, Radiculitis
Lyme arthritis
Knees > other Joints, fewer systemic sxs
1 knee most common (monoarthritis)
Oligoarthritis, shoulder/elbow/TMJ/wrist also occurs
Swelling/effusion significant, pain less than other bacterial or crystalline
Swelling may persist for months after successful tx
Little joint destruction or dysfunction for most patients
In untreated Lyme, 60% of pts may have arthritis which occurs in attacks that decrease over time
LD diagnosis
Erythema Migrans rash - sufficient for dx if exposure hx present
Lab studies - not helpful in early lyme (too soon)
Lyme serology
NOT useful in pt with EM, high sensitive/specific in early disseminated and late (arthritis, carditis, neuro manifestations), CSF antibodies useful in CNS
Lyme PCR
PCR - Good predictive value in synovial fluid for dx of arthritis, not in others
2 step testing
EIA (highly sensitive) screening
Positive or negative
then
Western Blot (specific)
IgM (2 bands), IgG (5 bands)
strict interpretation
LD treatment
Doxycycline - tx of choice (10-21 days)
Amoxicillin in children/pregnancy
cephalosporin for late stage
Prophylactic tx of LD
Nymph/adult I. scapularis tick has been attached for >36 hrs or is engorged
Local rate of tick infectivity is >20%
No contraindication to doxycycline
Treatment is started w/in 72 hrs of removal
Dose is doxycycline 200mg x 1 in adults (not amoxicillin)
Should test tick for LD
NO
PTLDS sxs
Joint pain, muscle pain, fatigue, malaise, cognitive problems
PTLDS tx
Direct tx at sxs, not “infection”
Lyme vaccine
Vaccine was on the market 1998-2002 (still available for dogs)
Removed for many reasons
Human Granulocytic Anaplasmosis (HGA) causative agent
Anaplasma phagocytophilum
Human Monocytic Ehrlichiosis (HME) causative agent
Ehrlichia chaffeensis
Anaplasma phagocytophilum and Ehrlichia chaffeensis
Obligate intracellular gram negative rods (Rickettsias)
Tropism for WBC –> morulae
Anaplasma phagocytophilum and Ehrlichia chaffeensis
Reservoir hosts
Deer, white-footed mouse
Anaplasma phagocytophilum and Ehrlichia chaffeensis Tick vectors
Anaplasmosis - I. scapularis (Deer Tick)
Erlichiosis - Amblyomma americanum (Lone star Tick) - southeast
Direct transmission from deer carcass
Anaplasmosis
Erlichiosis - incubation period
2-14 days
Anaplasmosis/Ehrlichiosis sxs
Fever, chills, HA, myalgias
Rash uncommon
Anaplasmosis/Ehrlichiosis labs
Leukopenia, thrombocytopenia, mild increase in AST/ALT – KEY
Anaplasmosis/Ehrlichiosis dx
Clinical scenario, with season, exposure history, and clinical presentation is most important
Anaplasmosis –> Peripheral smear shows morulae (Latin for mulberry ~ blackberry) in neutrophils (60-80% of cases)
Ehrlichiosis –> Peripheral smear insensitive (1-20% of cases)
Blood PCR, Serology
Babesiosis dominant pathogen + characteristics
Babesia microti dominant pathogen in US
Parasite
Most common transfusion-associated infection in US
Same distribution, vector as Lyme
Incubation period babesiosis
1-6 weeks
Clinical syndrome babesiosis
Gradual onset of fever, malaise, myalgia, arthralgia
Labs may show elevated bilirubin
Hemolytic anemia
Babesiosis dx
Peripheral smear
Blood PCR
Serology
Babesiosis tx
Quinine and clindamycin (difficult to tolerate)
Azithromycin and atovaquone (preferable unless severe)
A/E tx
Treatment: Doxycycline (Rifampin)
Rickettsia rickettsii →
Rocky Mountain Spotted Fever
Primary tick that transmits R. rickettsii in these states is the _______
American dog tick
Incubation period RMSF
2-14 days (mostly 5-7)
RMSF sxs
Fever
Rash (occurs 2-5 days after fever) ~ 90% of cases
Small, blanching, pink macules on the ankles, wrists, or forearms that evolve to maculopapules.
Headache, Nausea, Vomiting, Abdominal pain (may mimic appendicitis or other causes of acute abdominal pain), Muscle pain, Lack of appetite, Conjunctival injection
RMSF tx
Doxycycline for everyone (Even kids) - chloramphenicol alternate but toxic
Tularemia pathogen
Francisella tularensis (gram negative coccobacillus)
F. tularensis hosts
Rodents, rabbits classically associated (many mammals)
Exposure to F. tularensis
Most commonly tick, biting flies Direct inoculation (handing dead animal)
Tularemia incubation period
3-5 days
Tularemia presentation
Abrupt fever, chills, headache, myalgia, sore throat
Bite site commonly forms nonhealing ulceration/eschar
Ulcero-glandular most common (60-70%)
Pneumonic (~20%)
Tularemia dx
Labs nonspecific
Cultures often negative (but notify lab of suspicion)
Serology usually confirms (at 2 weeks)
Tularemia Tx
Aminoglycosides
Doxycycline
Fluoroquinolones
Virus causing meningoencephalitis
New England and Great Lakes region
Powassan
Caused by Colorado Tick Fever Virus
Rocky Mountain distribution
Usually mild, self-limited illness
Colorad Tick Fever
Borrelia hermsii or turicatae
Western US
Spirochetes detected in peripheral smears or CSF
Treated with doxycycline, tetracycline, penicillin, or ceftriaxone
Relapsing Tick Fever
Tick to worry about in MN
Ixodes scapularis
Rickettsia are Gram ____
negative
EM rash (Lyme disease)
Begins at site of tick bite after a delay (average 7 days)
Expands gradually over a period of days reaching up to 12 inches or more (30cm)
May feel warm to touch but is rarely itchy or painful
Sometimes clears as enlarges → Bulls-eye
May appear on any area of the body
Multiple rashes = disseminated1t
tx Anaplasmosis/erlichiosis
doxycycline (rifampin)
Lyme, _______ and ______ have same distribution vector
Anaplasma - Babesia microti
ixodes scapularis
