Title: Medical Parasitology
1Medical Parasitology
- Karen L. Bennett, PhD.
- M609 Medical Sciences Bldg.
- March 9, 2004
2(No Transcript)
3(No Transcript)
4(No Transcript)
5Introduction to medically relevant
parasites Parasites are eucaryotic organisms,
like us, and contain nuclei, cell organelles and,
for the helminths, tissues like our own. They
are not endogenous to humans. Therefore exposure
and the means of entry are important to the
disease process. Exposure severity of
illness often related to the infective dose, with
additional organisms acquired over time.
Parasitic infections are often chronic. Entry
enter by ingestion or direct penetration of the
skin. Knowing the means of entry for the
organisms discussed is important for disease
prevention.
6Introduction medically relevant
parasites Adherence parasites adhere to
specific host tissues, ie. malaria and red blood
cells or hookworms to the intestinal villi.
Identifying the methods and recognition molecules
are useful subjects of research, in order to
prevent parasite adherence, but will not be
considered today. Replication most protozoans
multiply in the host only a few worms do.
7Introduction basic clinical parasitology Cell
and tissue damage. Parasites dont usually
produce toxins tissue damage can be due to
mechanical blockage and inflammatory host
response. Toxic products are often released when
the parasites die. The host often produces
immunopathologic responses. Parasites have
developed many elaborate means to avoid the
hosts immune response.
8Anti-parasitic agents Why are there so few
effective anti-parasitic drugs? Only 3 new
anti-malarial drugs in past 20 years! (over 1,200
new drugs approved by FDA in that timeframe).
Is there a problem with resistance? Yes! What
are the current best means for prevention? Good
hygiene, simple techniques like bed nets for
mosquitoes. How do the major anti-parasitic
drugs work? Many block critical metabolic
pathways best are parasite specific.
9(No Transcript)
10Laboratory Diagnosis of Parasitic
Diseases Diagnosis often difficult. Traditional
methods are by microscopic exam. Newer means,
including western blots, ELISAs and PCR are
expensive. A few, unusual, low-tech methods will
be mentioned. The medical practitioner must be
aware of the possibility of parasites.
11(No Transcript)
12(No Transcript)
13(No Transcript)
14(No Transcript)
15(No Transcript)
16(No Transcript)
17(No Transcript)
18(No Transcript)
19(No Transcript)
20(No Transcript)
21(No Transcript)
22(No Transcript)
23(No Transcript)
24(No Transcript)
25Drug of choice for Trichomonas (and for Giardia,
another flagellate) is Flagyl.
26CRYPTOSPORIDIUM
27CASE 19
- In Milwaukee, WI water contamination from a
sewage treatment plant killed 100 people and
affected more than 400,000 in 1993. The parasite
that caused the disease was determined to be
cryptosporidium.
28SYMPTOMS
- Immunocompetent
- Mild self-limiting enterocolitis (watery
bloodless diarrhea, abdominal pain, nausea,
vomiting, and fever) - Spontaneous remission is common (usually within
10 days)
- Immunocompromised
- 50 or more stools per day
- Dehydration (fatigue, abdominal cramping, and
nausea) - Lasts months or years
- Common in AIDS patients
29LAB DIAGNOSIS
- Microscopic exam
- Acid fast stain of stool sample
- Endoscopic biopsy of small intestine
30Cryptosporidium oocysts with acid-fast stain
31LAB DIAGNOSIS
- Immunodiagnosis
- Immunofluorescence assay (IFA)
- Enzyme linked immunoabsorbant assay (ELISA)
- Polymerase Chain Reaction (PCR)
- Test of choice
32LAB DIAGNOSIS
33LIFE CYCLE
- Cryptosporidium lives and grows in variety of
animals geese to snakes to cows, sheep and pigs
to humans. - Cryptosproridium completes its cycle in a single
host. - The Species of Crypto known to infect humans is
Cryptosporidium Parvum.
34LIFE CYCLE
- Infectious agents are the OOCYSTS
- In immunocompromised patients ID50 is about 10 to
30 oocysts - Autoinfection takes place in 2 ways-
- gt Merozoites attach to nearby epithelial
cells and spread infection - gt thin walled oocysts excyst and continue
to spread infection within the body -
35A scanning electron micrograph of Cryptosporidium
lining the intestinal tract. (From Gardiner et
al., 1988, An Atlas of Protozoan Parasites in
Animal Tissues, USDA Agriculture Handbook No.
651.)
36A scanning electron micrograph of a broken meront
of Cryptosporidium showing the merozoites
within. (From Gardiner et al., 1988, An Atlas
of Protozon Parasites in Animal Tissues, USDA
Agriculture Handbook No. 651.)
37LIFE CYCLE
38TRANSMISSION AND EPIDEMIOLOGY
- Person to person (fecal-oral)
- Animal to human
- Contamination of water supplies (result of waste
runoff) - WATER-BORNE MOST COMMON
39TREATMENT
- Immunocompetent
- Self-limiting
- Usually symptoms subside within 10 days
- Immunocompromised
- Cocktail therapy -used to treat symptoms but NOT
THE DISEASE - Drugs include letrazuril, azithromycin,
paramycin, and hyperimmune bovine colostral
immunoglobulin
The only immunity is previous exposure and
extent of this immunity is not known.
40PREVENTION
- Wash hands
- Wash fruits and vegetables
- Avoid untreated water
- Treat contaminated water
- MAINTAIN PROPER HYGIENE!!
41WATER PREVENTION
- Ozone
- UV light
- Inexpensive tests to eliminate water borne
pathogens - Resistance to filtration
- Resistance to chlorine
- Kills all spores after one minute rapid boiling
- Chlorine not effective against crypto!!
42INTERESTING FACT
- In Uganda, the human population shares habitat
with free ranging gorillas. These people are
infected with animal-adapted genotype of
Cryptosporidium parvum.
43INTERESTING FACT
- There were 6 outbreaks between 1984 and 1994 in
the US. - In MO there were 26 confirmed cases from motel
pools in 1994.
44INTERESTING FACT
- Cattle alone produce about 4.57 tons of
Cryptosporidium oocysts per year in the US -
- BEWARE !
45FUN FACT
- Crypto-nite
- Cryptosporidium is the main reactive agent
causing Superman Sickness
46Microsporidium Encephalitozooon cuniculi
47Microsporidia spores Gram positive in biopsy
48Nature 2001 Vol 414450
49Nature 2001 Vol. 414401
50(No Transcript)
51(No Transcript)
52(No Transcript)
53(No Transcript)
54(No Transcript)
55(No Transcript)
56Multiple rings of P. falciparum trophozoites can
be found in a single red blood cell
57The of red blood cells showing parasites is
often low, making diagnosis difficult.
This slide shows the advanced ring stage of P.
vivax
58Seen here is a red blood cell filled with
multiple schizonts ready to burst free.
59Nature 2001 Vol. 415670
60(No Transcript)
61(No Transcript)
62(No Transcript)
63(No Transcript)