epidemiology: Staphylococcus aureus and/or Streptococcus
pyogenes; this bacterial disease is highly contagious in children
pathogenesis: superficial infection leads to formation of
thin-walled abscesses that look like blisters or "weeping" lesions
with scabs; complications - "blood poisoning"
(toxemia or septicemia)
treatment: bacitracin salve or other antimicrobial agents
resistant to bacterial enzymes that destroy penicillins
prevention: personal hygiene; avoid contact with lesions
on other people
Furuncle (boil)
epidemiology: Staphylococcus aureus; normal bacterial
microbiota in up to 30% of normal humans
pathogenesis: infected skin follicle leads to formation of
an abscess;
complications - multiple abscesses (carbuncles);
"blood poisoning" (toxemia) due to systemic distribution of toxin
or bacteria; osteomyelitis
treatment:
"lance" abscess; treat with bacitracin, vancomycin or other antimicrobial
agents that are resistant to bacterial enzymes that destroy penicillins
prevention: personal hygiene; avoid contact with boils on
other people; newly-developed vaccine StaphVAX
epidemiology:
Streptococcus
pyogenes (bacterium); according to CDC, there
were 500-1500 cases in the US in 1996 and 20% were fatal
pathogenesis:
rapidly-spreading infection leads to destruction
of tissues at sites of infection ... aka Flesh-Eating
Disease; complications - formation of
abscesses throughout the body and "blood poisoning"
(toxemia or
septicemia)
treatment:
penicillin, erythromycin, or tetracycline; surgery, when necessary
epidemiology: Candida albicans, this dimorphic fungus is a member of the normal
microbiota; likelihood of developing disease is enhanced by chronic skin moisture, especially
in immunosuppressed individuals (AIDS, diabetes, etc.)
pathogenesis: as Candida grows on the skin, it induces a bright red inflammation,
blister-like superficial lesions or more severe lesions all of which are perhaps related to
hypersensitivity; it sometimes occurs around the mouth (angular chelitis); complications include
systemic infection, which can lead to fulminating disease and death
treatment: clotrimazole, miconazole or nystatin for skin infections; oral ketoconazole
for systemic infections
epidemiology: Sporothrix
schenckii; spores of this fungus in soil are transmitted to humans via splinters, sphagnum
moss, thorns, hay,
etc.; also known as (rose thorn disease or rose-grower's disease or rose-garderer's
disease)
pathogenesis: skin lesions (painless pink, red or purplish "bumps") develop
at site of infection after 3-12 weeks, develop into ulcers that don't heal, then enter
the lymphatics and "move" up arm; complications dissemination to the lungs, joints
or central nervous system and can cause serious illness, especially in people with immunodeficiencies
treatment: potassium iodide, itraconazole, or amphotericin B
prevention: avoid contact with contaminated soil, splinters, thorns, etc.
Warts (verruca
vulgaris)
epidemiology: Human
Papilloma viruses are transmitted via scratches
pathogenesis: skin disfiguration from chronic benign tumors
treatment:
remove (excise) wart
by surgery (incision, cryosurgery or lasersurgery) or by the use of chemicals such as nitric
acid
prevention: avoid contact with warts on other people
pathogenesis:
recurrent chronic lesions (blisters)
on face, fingers, hands ...
becomes latent in local nerves and exhibits recurrence during periods of stress (physical
or psychological); herpes means "to creep"
treatment: acyclovir (zovirax) shortens episode, slows recurrence; valtrex is a second
generation version of zovirax ... works better
prevention: avoid contact with skin sores on other people
epidemiology:
Mycobacterium leprae; transmission unknown (direct
human-to-human contact via minute skin breaks ... or perhaps via respiratory droplets ???); ~6,000
known cases in US (~100 new cases per year ... "imported" by
immigrants and travelers), but ~500,000
cases in the world (down from 5.2 million in 1985)
pathogenesis:
slowly-developing (3-6 years) "lumpy" or discolored lesions
lead to sensory nerve damage and tissue
destruction; complications - no awareness of cuts,
burns, etc. leads to gangrene causing loss of digits or limbs;
skin disfiguration; liver, kidney and spleen damage causes
death
treatment: long-term multi-drug therapy (MDT) using
a combination of dapsone, clofazimine, and rifampin
(=rifampicin)
prevention: avoid contact with skin lesions of
lepers
epidemiology:
Ebola Virus is
transmitted by direct contact with infected blood, organs,
secretions, semen or contaminated needles; most prevalent in
Africa, where it was first identified in 1976; since then there
have been ~1100 cases identified, of which ~800 have died;
Ebola periodically causes a few hundred cases with each
short-lived outbreak ... most
recent outbreak (October 2000)
pathogenesis: infection leads to sudden malaise,
fever, muscle pain, headache and sore throat followed by
vomiting, diarrhea, rash and heavy bleeding in 2-21 days;
complications include massive damage to liver, spleen, kidney
(and moderate damage to pancreas, CNS and heart) and massive
hemorrhage from all body orifices, leading to death in 50-90%
of cases
treatment: TLC, symptomatic relief and support, no
known cure
prevention: avoid contact with infected blood or
body secretions
epidemiology: Clostridium tetani; endospores of
this bacterium enter body via animal bites, scratches, puncture wounds;
fewer than 10 cases per year in US
pathogenesis: toxin (tetanospasmin) causes CNS damage
(4-21 days); complications - respiratory failure causes death (70% of
patients die)
epidemiology: Bacillus
anthracis, an endospore-forming soil bacterium; this zoonotic disease primarily affects
grazing animals such as cattle, sheep and goats, but can be transmitted to humans by contact
with the endospores, either via skin wounds or by inhalation; this disease is considered to
be a good candidate for biological warfare, and has been used in terrorist
activities ... view a set of online CDC
videos on bioterrorism
pathogenesis:
as endospores germinate, the vegetative bacterial cells begin to produce a necrotizing toxin that
causes development of pustular lesions called eschars characterized by necrotic centers
that will eventually be filled with black fluid; complications include fulminating septicemia
that frequently leads to death, especially from the pulmonary form of the disease
Man with eschar on his neck
treatment: penicillin ... cipro (ciprofloxacin) was approved in 2000
prevention: anthrax vaccine
is not very effective, which has spurred ongoing attempts to develop a better one; avoid contact
with endospore-contaminated articles such as unwashed or unsterilized wool, goat hair, cattle
hides, etc.
pathogenesis: infects
and kills macrophages; whole body (liver,
spleen, lymph nodes (buboes),
lungs, meninges, skin) damaged, causing fever and massive blood clotting, which leads to
shock, which may cause death (major complication)
treatment: streptomycin or tetracycline
prevention:
vaccine; control rats and fleas; avoid contact
Borrelia burgdorferi (bacterium) is spread by the nymph stage (poppy-seed
sized) of deer (black-legged) ticks ... it takes ~36 hours for the tick to infect
you with enough bacteria to cause disease
reservoirs are white-tailed deer and white-footed mice
15,000 cases reported in the US each year, mostly in children 2-15 and adults
30-55 years old who live in the Northeast and upper Midwest
Lyme
disease was first discovered near Lyme, CT
most frequently diagnosed tick-borne disease in the US
pathogenesis: - 60-85% of patients develop an expanding, ring-shaped ("Bull's-eye")
red rash (erythema
chronicum migrans or ECM) at the site of a tick-bite ... after 3 days to one
month; accompanied by flu-like symptoms (malaise and fatigue, headache, fever and chills,
nausea, muscle and joint pain, neck stiffness) and patients may develop secondary skin lesions,
facial paralysis, forgetfulness; chronic, untreated systemic infection leads to arthritis,
heart inflammation, neurological abnormalities (weeks to months); nerve demyelination may
lead to multiple sclerosis-like symptoms (years after infection)
treatment: ceftin (cefuroxime axetil), penicillin or tetracycline (after diagnosis
with a newly-approved test kit, "PreVue B"); although there is controversy, it appears that
long-term intravenous antimicrobial agent therapy may be required in chronic cases
prevention: vaccine ("LYMErix")
was approved for
people from age 15 to 70, but not for those most likely to get the disease, those under 15;
this vaccine was subsequently removed from the market amid allegations that it might cause
the very signs and symptoms Lyme disease causes; it is important to avoid
tick-bite (wear
protective clothing, use tick repellent, remove attached ticks)
Rocky
Mountain Spotted Fever
epidemiology:
Rickettsia rickettsii; bacterium transmitted by dog
ticks (Dermacentor varibilis); 600-800 new cases
per year in the US (most cases occur in children 5-9 years old
who live in the southern states and are reported April through
September)
pathogenesis: damage to blood vessels causes
fever (higher than 102F and lasts many days) accompanied by
skin rash (begins on palms
of hands and feet,
then spreads to the arms
and legs
extremeties, the head
and the trunk of body), headache, muscle pains; complications -
damage to blood vessels throughout the body leads to impaired
function of the kidneys, liver, lungs, CNS (meningitis,
encephalitis), and gastrointestinal tract; these can lead to
death (mortality may be as high as 30% if not rapidly treated
with antimicrobial agents ... 4% if treated effectively)
treatment: tetracycline (best) or chloramphenicol
plus symptomatic relief and supportive care for
complications
prevention: vaccine for high-risk persons; avoid
contact with ticks
pathogenesis:
mosquito "injects" virus into bloodstream; virus replicates in the CNS,
causing fever and headache, vomiting, stiff back and neck, drowsiness,
tremors, loss of coordination, convulsions, seizures; complications
- may lead to coma as a result of CNS damage (can lead to retardation,
paralysis) and death occurs in 1-60%, depending upon the virus responsible
treatment: TLC ... management of symptoms and complications;
FDA has recently approved alpha-interferon as a possible treatment for
West Nile Fever
prevention: vaccines (none for West Nile Fever); mosquito repellent use;
mosquito control
epidemiology:
caused by Dengue
Fever Virus, which is transmitted by Aedes
aegypti or Aedes albopictus mosquitoes;
endemic
in Africa, the Caribbean, Central and South America, Southeast
Asia and Australia; ~100 cases per year imported into the US by
travelers
pathogenesis: mosquito "injects" virus into
bloodstream; this rarely fatal disease is characterized by
sudden onset of high fever and rash together with severe
headache, and severe muscle, joint and eye pain (sometimes
called "breakbone" fever); complications include hemorrhagic
fever, with bleeding from gastrointestinal and other
mucosal membrane orifices of the body, which can lead to
shock and death in up to 20% of cases (mortality is ~1%
with appropriate treatment)
treatment: TLC, fluid replacement in hemorrhagic
fever cases
prevention: vaccines (under development); mosquito
repellent use; mosquito control
pathogenesis:
mosquito "injects" virus into
bloodstream where the virus
replicates in the liver (causing jaundice), intestines (causing
bloody stools and, sometimes, vomiting of blood), and gingival
tissues (causing gums to bleed); complications include death in
up to 50% of cases
41%
of the world's people live in regions where malaria is transmitted
with ~500,000 new cases each year, there are now
350-500 million people infected with malaria in the
world, and ~1,200 cases are imported into the US each
year
more than 1 million people die of malaria each
year (especially children under 5)
malaria had even more impact prior to the mosquito
eradication programs of the past 50 years, and was a major
problem during World War II on the Pacific islands and
Sicily
pathogenesis:
infection of liver and erythrocytes causes damage
leading to chronic recurrent chills followed by high fever (104
F causes delirium, convulsions), sweating, headache, nausea,
splenomegaly; complications - red blood cell loss causes
anemia, "black" urine (hence "blackwater fever"); accumulation
of cell fragments in small blood vessels causes cerebral
hemorrhage, kidney failure, heart attack, liver damage
(jaundice) and death
pathogenesis:
tsetse fly bite becomes painful and swollen in several days,
then a lesion like a syphilitic chancre develops at site; then
systemic infection via bloodstream develops, causing
fever, severe headaches, paralysis, wasting, and coma, which
causes death (major complication)
treatment: pentamidine and suramin (with or without tryparsamide) are used in the first
stage of the disease; melarsoprol or eflornithine is used in the second stage of the diseases
schistosomiasis
is endemic in 74 developing countries, with ~600 million
people at risk
currently more than 200 million cases, over 80% of
which are in sub-Saharan Africa
~800,000 deaths per year worldwide
there may be as many as ~400,000 cases in the US
(immigrants who brought the disease with them)
pathogenesis:
cercariae burrow through skin, then infect the bloodstream
(causing fever, chills, sweats; back, groin or leg pain;
urticaria), then infect the liver, where mature flukes develop
and form eggs; the host response to the egg antigens
(granuloma formation) causes damage to lungs,
bladder (S. haematobium), liver
(enlargement, loss of function), and intestines
(ulceration, diarrhea, abdominal pain); complications -
chronic infection which causes ongoing liver damage
treatment: praziquantel or oxiaminiquine
prevention: avoid contact with water containing
human sewage and snails, especially in Asia, the Middle East or
on Caribbean islands (Puerto Rico, etc.)
Man with eschar on his neck
