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Micro OneLiners: Vector-Borne Infections and Multisystem Zoonoses

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Boy goes to summer camp in North Carolina; activities include hiking
in the mountains; develops fever, headache, myalgia, and malaise;
petechial rash on the cheeks, trunk, upper extremities, and palms,
consider
Rocky Mountain spotted
fever (RMSF)
Causative agent for Rocky Mountain spotted fever
Rickettsia rickettsii
Important growth characteristic of Rickettsia sp
Obligate intracellular
parasite
Characteristic of rash associated with Rocky Mountain spotted fever
Centripetal spread - A macular/petechial rash
develops in 90% of patients
after 3-5 days, initially on the
wrists, arms, and ankles,
and then spreads to the
trunk
Rash is observed frequently in Rocky Mountain spotted fever and the
differential diagnosis should include
Febrile exanthema (viral and
bacterial, including
meningococcemia)
In diagnosis and treatment approach to Rocky Mountain spotted fever,
the helpful tests are: a CBC, metabolic panel, and
CBC - thrombocytopenia,
elevated WBC count;
Metabolic panel -
hyponatremia, elevated
AST/ALT;
Peripheral blood smear
examination - bacteria in
monocytes
When a clinician suspects Rocky Mountain spotted fever, HME, or
HGA (in children or adults), based on clinical, laboratory, or
epidemiologic findings, antibiotic, to be initiated immediately is
Doxycycline (a bacteriostatic
drug against rickettsia)
Paroxysmal flu-like symptoms, fevers & chills, history of travel to
tropics, consider
Malaria
Flu-like symptoms (fever > 103oF), seizure, pulmonary edema, or
renal failure, or severe anemia in a man who recently traveled to the
tropics; blood smear has ring structures & gametocytes in RBC
(>2.5% of RBC); consider
Plasmodium falciparum
Patient w/ travel hx (back from the tropics) has flu-like symptoms;
splenomegaly; lab: CBC: anemia, thrombocytopenia, hypoglycemia
(blood smear: enlarged RBCs and Schuffner dots); consider
Plasmodium vivax
For treatment of uncomplicated falciparum malaria, consider
Artemether-lumefantrine >
Quinine and doxycycline (or
clindamycin)
For treatment of complicated falciparum malaria, consider
Quinidine plus clindamycin
(intravenous)
For treatment of vivax malaria, consider
Mefloquine and primaquine
Indication for use of primaquine in P. vivax infection
Targets chronic, latent liver
forms (hypnozoites)
Primaquine is contraindicated in pregnant women or in people who
are deficient in
Glucose-6-phosphate
dehydrogenase (G6PD)
Malaria-like illness in an immunosuppressed patient w/o travel hx
(blood smear has cross-over rings in the RBCs); consider
Babesia spp
Protracted fever, headache, fatigue, and a characteristic skin rash
erythema migrans; consider
Lyme disease
Causative agent for Lyme disease
Borrelia burgdorferi
Lyme disease is transmitted by the bite of infective
Ixodes ticks (blacklegged,
hard ticks)
Three major endemic areas in the United States are
Wisconsin/Minnesota, California/Oregon, and most importantly
Mid-Atlantic/Northeast
Typical if left untreated, infection can spread to joints, the heart, and
the nervous system. B. burgdorferi is rarely recovered from clinical
specimens, called a
Paucibacillary disease
Lyme disease diagnostics:
ELISA plus immunoblot;
PCR;
Patients may be
seronegative
Drugs of choice for treatment of Lyme disease
Doxycycline or amoxicillin
Patients with certain neurological or cardiac forms of Lyme disease
may require intravenous treatment with
Ceftriaxone or penicillin
High fever, chills, headache, myalgia and nausea along with
conjunctival suffusion, petechia, hepatosplenomegaly; symptoms
recur every week or 10 days for several months in patients in the
mountainous areas; consider
Relapsing fever (RF; aka:
borreliosis)
Relapsing fever is caused by
Borrelia recurrentis (a
spirochete similar to Lyme
disease agent)
Endemic (in the the Cascades, Sierra Nevada, Rockies and caverns of
Texas) forms of Relapsing fever are transmitted by
Soft ticks (genus
Ornithodorus), found in animal
reservoirs (e.g., squirrels and
other rodents)
Epidemic typhus is transmitted by the
Human body louse Pediculus
humanis
Causative agent for epidemic typhus
Rickettsia prowazekii
Clinical presentation of epidemic typhus
Abrupt onset; fever,
headache, chills, myalgias,
arthralgia; centrigugal
macular rash - start at trunk
and spread outward
Patient with clinical presentation similar to Rocky Mountain spotted
fever; not history outdoor activity; exposure to urine, feces, placenta,
or amniotic fluid from cattle, sheep, goats, cats, or dogs; consider
Q fever
Causative agent for Q fever
Coxiella burnetti
During the treatment of Lyme disease, a sudden high fever, flushing,
tachycardia, vasomotor instability may occur; consider
Jarisch-Herxheimer reaction
The pathogenesis of Jarisch-Herxheimer reaction is due to cytokine
cascade following the liberation of
Spirochetal constituents in
the blood stream
Symptoms of Jarisch-Herxheimer reaction may diminish after passive
administration of
Anti-TNF-alpha
Flu-like illness, diarrhea, rash, calf and low back pain in patients
(swimmers, triathletes, kayaking, flood victims, military) in Hawaii or
Latin America or Asia (rural rice fields); ddx of malaria, dengue, RF,
and RMSF has been ruled out; consider
Leptospirosis
Leptospirosis caused by Leptospira interrogans is a zoonosis and is
transmitted by exposure to
Rodent urine (in fresh water)
Clinical diagnosis of leptospirosis (after Hx and PE) may follow labs
(CBC: wnls; thrombocytopenia, UA: proteinuria/hematuria; LFT, CPK;
consider GFR and
CSF examination
Diagnosis of leptospirosis is based on ruling out of ddx (of dengue,
malaria, relapsing fever, RMSF) and blood cultures (BCx) first 7-10
days, thereafter only from
Urine (warn lab for special
culture media: Fletcher's or
EMJH media)
Specific therapy for leptospirosis:
Oral doxycycline;
In severe cases injected
Penicillin (be aware of
adverse reaction of JarischHerxheimer
reaction, common
for treatment of all spirochete
diseases)
An abrupt onset of high fever, frontal headache, myalgia, and a faint
macular rash (containing islands of pallor) that becomes evident on
the second to fourth day of illness; suspicion of arthropod-transmitted
disease; consider
Dengue
A petechial rash with development of subcutaneous hemorrhage may be found in
Dengue hemorrhagic fever
Dengue is transmitted by a primarily day-biting Aedes mosquito often
found in
Urban areas
For the diagnosis of dengue, an appropriate clinical scenario would be
supported by the detection of
IgM
Dengue-like vector-borne illness is
Chikungunya fever (clinically
including the rash, although
hemorrhage, shock, and death
are not typical of chikungunya)
In chikungunya, a major distinguishing feature is
Arthritis or arthralgia
(whereas in dengue, myalgia
is the major clinical feature)
Similar to dengue, diagnosis of chikungunya is based on
Serologic tests
A patient from S. America has a week-long fever, anorexia,
lymphadenopathy, mild hepatosplenomegaly, and myocarditis; a
nodular lesion on the arm; blood smear should reveal
Trypanosoma cruzi
Chronic-stage of systemic disease w/ cardiomyopathy,
megaesophagus, megacolon, and weight loss in a pt from S. America;
consider
Trypanosoma cruzi (Chaga's
disease)
Wound infections after dog and cat bites are caused by a variety of
microorganisms, but from dog and cat bite infections, a major
pathogen remains
Pasteurella multocida
Management of dog and cat bites includes consideration of rabies
post-exposure prophylaxis, tetanus immunization, and
Antibiotic prophylaxis
Primary closure of puncture wounds and dog bites to the hand is
Not indicated
For prophylaxis of P. multocida infection after cat bites, consider
Amoxicillin-clavulanate or a
fluoroquinolone)
Exposure (time & place to environment), painless papule progressing
to vesicles/bullae, then black eschar and edema, often intensely
pruritic, evolving over 3-5 days black eschar on exposed area;
consider
Cutaneous anthrax
Unique features of cutaneous anthrax include edema, lack of pain and
bullous fluid that lacks
PMNs
Cutaneous anthrax can be treated in 7-10 days with
Ciprofloxacin
Fever, chills, sweats, GI symptoms, cough, malaise, chest pain; CXR:
wide mediastinum and bloody pleural effusion, in a patient with
occupational exposure or in multiple patients in space and time
(suspicion of bioterrorism); consider
Inhalation anthrax
CT scan in inhalation anthrax may show hyper-dense mediastinal
nodes and
Pulmonary edema
Cultures of blood and respiratory specimens from in inhalation anthrax
should yield bioterrorism agent
Bacillus anthracis
DOC of Inhalation anthrax is
Ciprofloxacin or levofloxacin
> doxycycline (same for
cutaneous anthrax)
Sixty days course is recommended for any presentation to avoid
Breakthrough of incubation
of spores (or relapse)
Post-exposure prophylaxis to prevent inhalation anthrax requires
Ciprofloxacin for 60 days
Infection control of all types of anthrax (based on non-communicability
of the pathogen) warrants only
Standard precautions
Afebrile, systemic toxic diseases in infants (honey), and in adults
foodborne (meat, canned vegetables), wound (injected), iatrogenic
(cosmetic); consider
Botulism
Many patients with acute febrile flaccid paralysis in the same
geography without common food source; consider
Bioterrorism-associated
botulism
Differential diagnosis of botulism-like symptom/signs should include
Myasthenia gravis, Stroke,
Chemical Intoxications,
Lambert-Eaton disease,
Guillian-Barré
Species of Clostridium that causes botulism is
C. botulinum
CSF examination in botulism is
Normal profile (no
pleocytosis)
Post lab confirmation of food botulism, while waiting for antitoxin;
consider giving
Activated charcoal
Infection control of all types of botulism (based on noncommunicability
of the pathogen or toxins) warrants only
Standard precautions
No person-to-person transmission precautions are observed (other
than standard precautions) for the bioterrorism agents
Anthrax, botulism (noncommunicable
among
patients)
A localized infection with ulceration following inoculation in the skin;
lymphadenopathy; exposure to horses, mules, or donkeys; consider
Acute glanders (caused by
Burkholderia mallei)
Acute bloodstream infections due to Burkholderia mallei (aerobic
slender gram-negative rod, which causes glanders in horses),
consider
Sepsis (can be rapidly fatal)
Burkholderia mallei is isolated from lung infections in a cluster of
patients (in space and time), suspect
Bioterrorism
Patients with glanders should be isolated, respiratory precautions
because Burkholderia mallei spread by
Aerosol
The sudden onset of fever, chills, headache, malaise, abdominal pain,
nausea, and vomiting, after exposure to rodents, rabbits or fleas, in rare patients in the South West USA; consider
Plague
Plague is caused by an aerobic, Gram-negative bipolar rod (appears
as a "safety pin" on special stain) species
Yersinia pestis
Plague (in the South Western USA) from the bite of an infected flea
and developing painful lymphadenitis; consider
Bubonic plague
Plague after flea bite or from direct contact with infectious fluids
(infection spreading directly through the bloodstream with no localizing
signs); consider
Septicemic plague
Rare plague with lung infection, transmitted -from person-person,
resulting from aerosol exposure to infective droplets or (in cluster of
patients in space and time (bioterrorism)); consider
Primary pneumonic plague
Plague cases, resulting from the spread of Y. pestis to the lungs in
patients with untreated bubonic or septicemic infection; consider
Secondary pneumonic
plague
Drug of choice for prompt treatment of plague is
Aminoglycosides >
fluoroquinolones > doxycycline
In the DDx of bioterrorism-related pneumonia with pleuritis and hilar
adenopathy, include anthrax, plague and also
Tularemia
Small, pleomorphic, aerobic Gram-negative rod causes 1)
bite/abrasion (acquired from tick exposure or contact with rabbits)-
associated nodule/ulcer to sepsis, or 2) inhalation (bioterrorism)-
associated acute fever, dry cough (CXR: infiltrates and hilar
adenopathy); consider
Francisella turlarensis
DOC of tularemia is
Streptomycin
Acute fever, myalgias, remorrhagic rash, conjunctivitis, pharyngitis,
headache, diarrhea, and thrombocytopenia in patients in Africa or
traveler (or caregiver) in Africa (back in the USA); consider
Viral hemorrhagic fever (e.g.,
Ebola, Marburg, Lassa)
For Ebola, person-to-person transmission based infection control
(respiratory) precautions must include
Strict patient isolation
Sudden fever of more 102oF, homogeneous vesiculo-pustular rash are
noted in multiple patients (in time and place); consider
Small pox (due to variolla
major virus)
The main diagnostic differential of small pox is
Varicella or zoster
(heterogeneous vesiculopustular
rash is noted)
For small pox associated bioterrorism, person-to-person transmission
based infection control warrants
Isolation and respiratory
precautions