Rabies and Tetanus and Ticks

Oh my…

Heather PattersonPGY3

November 7, 2007

Objectives

• Review– basic pathophysiology– clinical presentation – management

• What this will not be:– Didactic!

Describe the rash.

Rocky Mountain Spotted Fever

Etiology?• Rickettsia rickettsee – found in Rocky Mountain wood tick saliva

How many hours does the tick need to feed for innoculation?

• 6 hours

Rocky Mountain Spotted Fever

• R. rickettsii:– Obligate intracellular bacteria– Infect endothelial cells and vascular smooth muscle – Initiates the coagulation cascade– Cellular immune response and complement activation

↓Increased vascular permeability

Rocky Mountain Spotted Fever

• Clinical Presentation– Onset:

• Day 2-14 after bite (mean 7 days)• Most often abrupt onset but can be gradual (33%)

– Symptoms:• Sudden onset fever (>38.3) and rigors – may precede other symptoms by 2-3 days• Myalgias – tenderness in large muscle groups • Headache• Nausea,vomiting, anorexia (80%)• Rash

Rocky Mountain Spotted Fever

• Classic Triad (3%):– Fever– Rash– Tick bite

Rocky Mountain Spotted Fever

How does the rash present on day 2-4 post onset fever?

• 2-6 mm blanchable, pink macules • Wrists, palms, ankles, soles • Spreads cetripetally 6-12 h post onset

Rocky Mountain Spotted Fever

How does the rash present on day 4-6 post onset fever?

• Non-blanchable petechial rash• Local edema surrounding petechie

Rocky Mountain Spotted Fever

– Based on clinical features– Skin bx with assays– dx can be made in 4h– Serology – drawn 2-3 wks post onset

Labs:– Bands– Thrombocytopenia– ↑Na– ↑ Transaminases

How do we make the diagnosis?

Rocky Mountain Spotted Fever

• DDx:– Meningococcus– Rubella– Measles– Disseminated gonoccocal– TSS– Mononucleosis– Enteroviral infections– Other infections: dengue, leptospirosis,

typhus

Rocky Mountain Spotted Fever

• Must think of RMSF with unexplained fever even in absence of rash, headache, tick bite, or travel to endemic area

Rocky Mountain Spotted Fever

• Complications:– Cardiac:

• Myocarditis• 1 degree AV block, non-specific ST-T changes• PAT, Afib• CHF

– Resp:• Interstitial pneumonitis• Pulmonary edema, effusions, infiltrates• ARDS

Rocky Mountain Spotted Fever

• Complications:– Neuro:

• Eosinophilic meningitis• Encephalomyelitis• Vaculitis +/- thrombosis• Mov’t disorders

– Other:• Shock• DIC

Rocky Mountain Spotted Fever

• Doxycycline – 100mg po bid – 2.2 mg/kg for kids

• Tetracycline– 2g/d

• Chloramphenicol– In pregnancy or kids <8y

Treatment? Duration?

• Treat for 2-5 days after afebrile OR min of 7-10 days

Rocky Mountain Spotted Fever

• Steriods:– Unstable, encephalitis, cerebral edema or

“extensive” vasculitis

• Mortality:– Untreated >30%– Treated 3-7%

Case 2

Case 2

Lyme

Etiology?• Borrelia burgdorferi – spirochete

• Vector – deer tick (deer, small rodents)

How many hours does the tick need to feed for innoculation?

• 24-72 hours

Lyme Pathophysiology

• Hematogenous spread of spirochete• Affinity for skin, synovial tissue, nervous

tissue.

Lyme

• Classification by stage of infection:– Early Lyme Disease– Acute Disseminated Infection– Late Lyme Disease

Early Lyme Disease

• Onset:– 1-36 days post innoculation

• Clinical features:– Rash (90%) +/- 2º lesions

• Lymphadenopathy in same region

– Constitutional symptoms “flu-like”• Low grade fever• Malaise, lethary

– Migratory arthralgias and myalgias

CLUE:

Rash is present in 90%

Diagnostic

Early Lyme Disease

– Neuro• h/a • meningeal irritation• photophobia

– GI:• N/V• RUQ pain

CLUE:

Rapidly changing and intermittent symptoms

in many systems

Erythema Migrans

• Characteristics:– Round/oval/triangular/linear– Confluent or targetoid– Sharply demarcated boarders– Flat or raised – Blanch with pressure

• Size:– Spreads ~1-2cm/day– Ave size 8-10cm

• Secondary lesions– Smaller, migrate less, spare palms and soles

Lyme – Acute Disseminated

• Acute Disseminated Infection– Onset

• Avg 4 wks post innoculation• May overlap symptoms of early or late

– Neuro• MC -Fluctuating meningoenceph• Triad

– Cranial neuropathy (Bell’s)– Peripheral neuropathy/radiculopathy– Meningitis

• CSF– N gluc, ↑prot/lymphs

CLUE:

•Multiple neuro features in CNS/PNS

•Bilateral Bell’s = Lyme until proven

otherwise

Lyme

• Acute Disseminated Infection– Joint:

• Intermittent large joint inflam arthritis• Brief with spont remission• Recurrent

– Cardiac:• Dysrhythmias and blocks• Uncommon

CLUE: Cardiac: Fluctuating

blocks, slow spont resolution

Joint: shorter duration, recurrent

Lyme - Late

• Late Lyme Disease– Joint:

• More frequent episodes of arthritis• Becomes chronic

– Neuro:• Chronic encephalopathy• Memory and learning abN• Sensory abN• Psych

Lyme - Diagnosis

• Erythema migrans– endemic area

• ELISA test 89% Sens and 72% Spec• Confirmed on Western Blot/PCR• Isolation from tissues and body fluids takes weeks to

grow• Impractical clinically

Lyme - Treatment

• Prophylaxis?– Risk of infection minimal to nonexistent if attached

<24hrs– If symptoms develop, ABx curative in most cases

• Uncomplicated– PO ABx 14-21 days

– Doxycycline 100mg BID for adults– Amoxicillin 50mg/kg divided TID for Peds

• Late or severe disease – IV ABx x 30d – Ceftriaxone/PenG/chloramphenicol – Neurologic (other than Bell’s) or cardiac manifestations

Case 3

• 18mo F sleeping at the cottage. Parents go in to check on her. There is a bat in the room.

• What do you do?

Rabies

• Bats are a major vector of rabies in North America• Analysis has shown that rabies comes from bats even when

there is absence of a bite.• CDC recommends:

– Postexposure prophylaxis for anyone exposed to a bat who is unable to give a history of contact : ie sleeping, children etc

– Any contact with bat, including saliva– Bat bites

Rabies

• What is the major animal vector in North America?– Raccoon

• What are other common vectors:– Bat– Skunk– Fox– Woodchuck– Other carnivores

Rabies

• What is rabies?– Bullet shaped RNA rhabdovirus– Previously thought to be a single

virus responsible for all rabies– Antigen detection has shown that

several viruses and at least 6 serotypes exist

Rabies

• How is rabies transmitted?– Saliva– Scratches– Aerosolized virus into

respiratory tract– Secretions that contaminate

MM– Corneal transplants

Rabies

• How does rabies affect the body?

(what tissue does it primarily affect?)

• The virus attacks nerve tissue– Spreads along peripheral nerves

and muscle fibers to the CNS– Encephalomyelitis– Spreads from CNS throughout the

PNS especially to highly innervated areas

• Progression to generalized nervous system failure and death

Rabies

• Rabies is a uniformly fatal disease once clinical symptoms manifest

• Presents with 1 of 2 clinical forms1)Encephalitic (furious) rabies

– 80-85%– Hydrophobia, pharyngeal spasm, hyperactivity– Paralysis, coma and death

2)Paralytic form– Far less common

Rabies

5 clinical stages:

1) Incubation- Ranges from 10d to 1yr (avg 20-60 days)

2) Prodrome- Occurs 2-10d post-exposure last <2wks- Nonspecific flu-like illness

3) Acute Neurologic Syndrome- 2-7days after prodrome onset- Dysarthria, dysphagia, salivation, diplopia, vertigo,

nystagmus, agitation, hallucinations, hydrophobia, hyperative DTR, nuchal rigidity

4) Coma- 7-10 days after neuro symptoms- Prolonged apnea and generalized flaccid paralysis

5) Death

Rabies

• Prodrome:– Sounds like all the other viral

prodromes?– If the patient has sustained a bite,

are there any clues to dx?

CLUE:

Tingling at the bite over first few days

Rabies

• Questions• Saliva contact?• Skin breakdown?• Provoked or unprovoked attack?• Wild vs domestic animal?

• All suspicious warrant a call to the MOH on-call 264-5615

• Immediately if scratch or bite to head• Urgently in all other cases

• Follow-up is with MOH or the clinical disease unit during the day

• Preexposure prophylaxis:– Who gets this?

• Travel to area where dog rabies is endemic

• Likelihood of being in contact with virus or vectors

Rabies