Tick Born Infections

Question 1

What are the two ticks most responsible for transmitting Borrelia burgdorferi in the USA?

Answer 1

Ixodes scapularis (deer tick)

and

Ixodes pacificus

Question 2

Borellia bergdorferi

Answer 2

causes Lymes disease. Mouse is natural reservoir.

Gram negative

spirochete–spiral shaped with axial fillaments

has flagellae

Question 3

Lymes Disease

Answer 3

Caused by Borrelia burgdorferi, which is transmitted by the tick Ixodes (also vector for Babesia). Natural reservoir is the mouse. Mice are important to tick life cycle. Common in northeastern United States. Treatment: doxycycline, ceftriaxone.

3 stages of Lyme disease:

1. Stage 1-erythema chronicum migrans (expanding “bull’s eye” red rash with central clearing), flu-like symptoms. (60-80%)–NOT ALWAYS RASH
2. Stage 2-neurologic (facial nerve palsy) and cardiac (AV nodal block) manifestations .
3. Stage 3-musculoskeletal (chronic monoarthritis and migratory polyarthritis), neurological (encephalopathy and polyneuropathy), and cutaneous manifestations.

Question 4

What is the mnemonic for Lyme’s Disease?

Answer 4

FAKE a Key Lyme pie:

Facial Nerve palsy (typically bilateral)

Arthritis

Kardiac Block

Erythema migrans

Question 5

Stage 1 of Lyme’s Disease

Answer 5

Erythema migrans (EM) seen in 60-80% of cases of at least 2 inches in size. Bull’s eye not always present.

no itching

no pain

Nonspecific (no change) in CBC and LFT

ESR and CRP may be elevated.

Question 6

Early disseminated Lyme’s burgdorferi

Answer 6

Stage 2 of Lymes disease.

Constitutional–Lymphadenopathy

Musculoskeletal–Arthralgias

Neurologic–Facial nerve palsy (mouth droops)

Cardiac–AV block

Question 7

What should you know about an AV block in regards to Lymes disease?

Answer 7

AV block can occur with Lyme’s burgdorferi.

If you treat with antibiotic (Ceftriaxone [IV]) the AV block ALWAYS goes away. So, no need for perminant pace maker.

Question 8

Late (persistant) Lymes borreliosis

Answer 8

chronic arthritis

acrodermatitis chronicum atrophicans

neurological impairments

(months to years)

Question 9

Laboratory testing for Lymes borreliosis

Answer 9

Screening + Confirmatory + Specific

Screening: Blood smear to rule out Babesia. ELISA and EIA for antibodies (place more emphais on IgM than IgG–can persist)

Confirmatory: Western Blot to determine significance.

for Western: need >or equal to 2 bands for IgM and > or equal to 5 bands for IgG – for positive result

Question 10

Differential diagnosis for Lyme’s borreliosis

Answer 10

Acute:

Anaplasmosis, Babesiosis, RMSF or rickettsiosis, Enterovirus (oder stool for this).

Chronic:

chronic fatigue syndrome, fibromyalgia, depression

Question 11

What if a screening test comes up negative for Lyme borreliosis?

Answer 11

Negative screening test carries a high negative predictive value.

Lyme borreliosis is a CLINICAL diagnosis

Question 12

Rickettsia rickettsii

Answer 12

Rocky Mountain spotted fever (tick) -Rickettsia rickettsii. Broadly distributed in US (in spite of name).

Intracellular Gram negative rod

60% of patients <20 years

Rash typically starts at wrists and ankles and then spreads to trunk, palms, and soles.

Rickettsiae are obligate intracellular organisms that need CoA and NAD+.

Question 13

RMSF: Epidemiology

Answer 13

tick vectors: Dermacentor spp. (Wood tick), Amblyomma americanum (Lone Star tick), Rhipicephalus sanguineus (Brown dog tick)–AZ.

Rodents and dog reservoir

incubates 3-12 days

mortality around 20%

Question 14

RMSF: Clinical illness

Answer 14

abrupt onset of influenza-like symp.

fever, chills, myalgias, headache, nausea, vomiting

rash observed on day 4

splenomegally noted 50% of time

**NO eschar at bite site

**longer time with a rash increases mortality

Question 15

RMSF: Laboratory tests

Answer 15

Reduced platlet count, WBC usually normal

IFA positive = good sensitivity (true positive rate)

Question 16

Differential for RMSF

Answer 16

Meningococcemia

Measles (rubeola)

Other rickettsioses:

Murine typhus (eschar at bite site)

Epidemic typhus (eschar at bite site)

Question 17

Babesiosis

Answer 17

Babesia are hemato-parasites

B. microti dominant pathogen in USA

tick vector: I. scapularis (Deer tick)

reservoir: white footed mouse and white tailed deer

ESR increased.

IFA (IgG) > 1,000 suggests active infection

**A positive blood smear includes ring form, and “Maltese cross” is diagnostic

Treatment: Atovaquone + azithromycine

or Quinine + Clindamycin

Question 18

Tularemia

Answer 18

Franciscella tularensis

Vectors: Ticks, deer flies, mosquitoes. Reservoir hosts: Rabbits > deer > other rodents

Abrupt onset fever and chills

**Bite site ulcerates and forms black eschar with nonhealing ulcer.

Regional lymphadenopathy

Treat with Doxycycline (7-14 days)

Question 19

Ehrlichia and Anaplasma

Answer 19

Tick vector via white footed mouse and white tailed deer

Gram negative bacteria ca. 0.5-2 µm. Obligate intracellular organisms

morula~!

Incubates for 2-14 days then causes (80%) fever (103-104), chills, headache, myalgias.

Leukopenia (low WBC) and Thrombocytopenia (most significant)

If morula detected must treat with Doxycycline!

Remember to compare with time of year… influenza?

Question 20

How would you distinguish Ehrlichia and Anaplasma?

Answer 20

Light microscopy:

Monocytes with morula (berry-like inclusions) in cytoplasm = Ehrilichia

Granulocytes with morula in cytoplasm = Anaplasma