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 (more
epidemiology)
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: a vaccine ("LYMErix")
was approved, but has been removed from the market, so it is important
to avoid
tick-bite (wear protective clothing, use tick repellent, remove
attached ticks) and protect
your pets, too
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
epidemiology: Hepatitis A or Hepatitis
E virus;
~3500 cases per year in US; transmitted via raw shellfish, produce,
other fecally-contaminated foods, especially in institutions
pathogenesis: intestinal infection with Hepatitis A or E virus
leads to anorexia, nausea, vomiting, low-grade fever; systemic distribution
leads to liver damage, which causes jaundice; some people are asymptomatic,
however; complications - chronic disease, relapses are
common; ~100 deaths per year in US
Hepatitis
B Virus - hepatitis
B is transmitted by sexual (especially in men who have
sex with men) contact (55% of infections) and IV drug injection,
transfusion, tatoos, and can be transmitted from mother to
infant during the process of birth; ~5,000 cases reported each
year in US, but CDC estimates actual infections may be as high
as 20,000 per year with as many as 1.25 million chronic cases
in the US and 200-300 million cases worldwide
Hepatitis
C virus - hepatitis
C is transmitted in the same ways as hepatitis B (injection
of illegal drugs, transfusion, tatoos or engaging in unprotected
sex); ~800 new reported cases of hepatitis
C per year in US, but CDC estimates actual infections may
be as high as 20,000 per year with ~3.2 million chronic cases
in US and ~100 million cases worldwide
Hepatitis virus D - defective virus (may be a viroid)
that only infects hepatitis B victims; hepatitis
D is primarily transmitted via infected blood; CDC estimates
there may be ~70,000 carriers in US
pathogenesis:
hepatitis
B - 50% asymptomatic, but in the other 50%, liver infection
leads to fatigue, anorexia, taste changes, vomiting and jaundice
(indicating liver damage); complications include damage to intestines
(clay-colored stools), and kidney (dark urine); chronic disease,
carriers (6-10%); cirrhosis; hepatitis D virus co-infection;
death (~5,000 per year in US)
hepatitis
C - 70% asymptomatic, 30% have mild symptoms; complications
include chronic liver infection, carrier state (~40%); cirrhosis;
risk factor for hepatocarcinoma; death (~10,000 per year)
hepatitis
D - only infects those who are already infected with
hepatitis B virus, but makes these cases more severe because
it causes progressive liver damage; death (20-30%, ~1000 per
year)
treatment: α-interferon
for hepatitis B and C; TLC (prolonged bed rest); liver transplant
prevention: avoid
high-risk behavior; use condoms;
get hepatitis B vaccine; hepatitis B immune globulin for those who have
been exposed, but have not yet exhibited signs or symptoms of disease
