Parasitic Diseases Flashcards
1
Q
Epidemiology of parasitic diseases?
A
- majority occur in tropical regions, where there is poverty, poor sanitation and personal hygiene
- often entire communities may be infected with multiple, different organisms which remain untx b/c tx isn’t accessible
2
Q
Epidemiology of parasitic diseases?
A
- majority occur in tropical regions, where there is poverty, poor sanitation and personal hygiene
- often entire communities may be infected with multiple, different organisms which remain untx b/c tx isn’t accessible
3
Q
What does effective prevention and control of parasitic diseases require?
A
- “mass intervention strategies” and intense community education. Examples include:
- general improved sanitation: pit latrines, fresh water wells, piped water
- vector control: insecticide impregnated bed nets, spraying of houses with residual insecticides, drainage, and landfill
- mass screening and drug administration programs which may need to be repeated at regular intervals
4
Q
What are parasites?
A
- organisms that infect and cause disease in other animals: protozoa, helminths, and arthropods
5
Q
How are protozoa transmitted?
A
- can be passed directly from host -> host through sexual contact, by contaminated water, or through arthropod vector.
- Direct or indirect transmission results from ingestion of highly resistant spores that are shed in feces of infected host
- most are mobile by means of flagella, cilia or ameboid motion
6
Q
How are helminths transmitted?
A
- wormlike parasites
- transmission occurs primarily through ingestion of fertilized eggs or the penetration of the infectious larval stages through the skin
- infections can involve many organs: liver, lungs, urinary and intestinal tract, circulatory, and nervous systems, and muscles
3 main groups: - flatworms (platyhelminths)
- thorny-headed worms (acanthocephalins)
- roundworms (nematodes)
7
Q
What are the most common arthropods?
A
flies, fleas, ticks, mosquitoes, and lice
- transmission from arthropod to human occurs either mechanically or biologically
8
Q
Effects of parasitic infections?
A
- typically, a parasitic infection doesn’t directly kill a host
- the stress placed on the host’s resources can affect its growth, ability to reproduce and survival
- This stress can sometimes lead to host’s premature death
9
Q
Pathogenesis of parasitic infection?
A
- organisms attack a host and begin to multiply
- multiplies and increasingly interferes with the normal life functions of the host
- Host begins to feel ill as a sx of parasite’s invasion and activities
- In many cases, the host’s immune system may be able to respond to the parasite and destroy it (immunocompetent person)
10
Q
What is unique about parasites?
A
- complex life cycles
- may spend part of their life cycle in a variety of differential species hosts
- Host species may be animal (all types), insect, or other
- May live only in water, or on veggies (grass, and soil)
11
Q
What does effective prevention and control of parasitic diseases require?
A
- “mass intervention strategies” and intense community education. Examples include:
- general improved sanitation: pit latrines, fresh water wells, piped water
- vector control: insecticide impregnated bed nets, spraying of houses with residual insecticides, drainage, and landfill
- mass screening and drug administration programs which may need to be repeated at regular intervals
12
Q
What are parasites?
A
- organisms that infect and cause disease in other animals: protozoa, helminths, and arthropods
13
Q
How are protozoa transmitted?
A
- can be passed directly from host -> host through sexual contact, by contaminated water, or through arthropod vector.
- Direct or indirect transmission results from ingestion of highly resistant spores that are shed in feces of infected host
- most are mobile by means of flagella, cilia or ameboid motion
14
Q
How are helminths transmitted?
A
- wormlike parasites
- transmission occurs primarily through ingestion of fertilized eggs or the penetration of the infectious larval stages through the skin
- infections can involve many organs: liver, lungs, urinary and intestinal tract, circulatory, and nervous systems, and muscles
3 main groups: - flatworms (platyhelminths)
- thorny-headed worms (acanthocephalins)
- roundworms (nematodes)
15
Q
What are the most common arthropods?
A
flies, fleas, ticks, mosquitoes, and lice
- transmission from arthropod to human occurs either mechanically or biologically
16
Q
Effects of parasitic infections?
A
- typically, a parasitic infection doesn’t directly kill a host
- the stress placed on the host’s resources can affect its growth, ability to reproduce and survival
- This stress can sometimes lead to host’s premature death
17
Q
Pathogenesis of parasitic infection?
A
- organisms attack a host and begin to multiply
- multiplies and increasingly interferes with the normal life functions of the host
- Host begins to feel ill as a sx of parasite’s invasion and activities
- In many cases, the host’s immune system may be able to respond to the parasite and destroy it (immunocompetent person)
18
Q
What is unique about parasites?
A
- complex life cycles
- may spend part of their life cycle in a variety of differential species hosts
- Host species may be animal (all types), insect, or other
- May live only in water, or on veggies (grass, and soil)
19
Q
Protozoa species?
A
- Sarcodina (amebas)
- Sporozoa ( non- motile sporozoans)
- Mastigophora (flagellates)
- Ciliata (ciliates)
20
Q
Metazoa (helminth) species?
A
- flatworms (platyhelminthes): flukes (Trematoda), and tapeworms (Cestoda)
- roundworms (nemathelminthes)
21
Q
What are protozoa and what kind of disease state do they cause?
A
- single cell (unicellular) organisms
- historically been the cause of more disease and death than any other category of disease-causing organisms:
- Malaria
- African sleeping sickness
22
Q
What is a trophozoite?
A
- term for the live adult protozoa
- cysts, spore or “eggs” are non-adult forms
- Most of these diseases are spread by the fecal-oral route
23
Q
What is the cause of Giardiasis?
A
- Giardia lamblia, a flagellate, is a common pathogenic protozoan
- infects duodenum and jejunum of humans
24
Q
Epidemiology of Giardiasis?
A
- occurs worldwide
- humans are infected by ingestion of fecally contaminated water or food containing giardia cysts
- it is also spread by direct person-person contact, which has caused outbreaks in institutions such as day care centers
- Oral-fecal transmission
At high risk: infants, kids
->especially internationally adopted kids
25
Q
How long can Giardia lambda cysts survive in water?
How are humans infected?
A
up to 3 months
- outbreaks among campers in wilderness areas suggest that humans may be infected with guard harbored by rodents, deer, cattle, sheep, horses, or household pets
- life cycle: 2 forms: cysts: infectious form, and trophozoites: mature form
- localize to the small bowel, adhere and once they get back into cyst form -> go into stool
26
Q
What will a biopsy of small bowel show?
A
- parasites attach to the bowel wall and may cause irritation and low-grade inflammation of duodenal or jejunal mucosa so a bx of the small bowel will show:
- crypt hypertrophy
- villous atrophy or flattening
- epithelial cell damage
27
Q
Sx forms of giardiasis?
A
- a large portion of infected pts are asymptomatic but sx forms are:
1. acute diarrhea
2. chronic diarrhea
3. malabsorption syndrome
28
Q
Presenting sxs of Giardiasis?
A
- presenting sxs can be diarrhea, malaise, steatorrhea, abdominal cramps, bloating, flatulence, N/V, and wt loss
- pts with chronic infection often experience major wt loss, malabsorption and depression
- the stools may be watery, semisolid, greasy, bulky, and foul-smelling at various times during the course of the infection
29
Q
Giardiasis encystment?
A
- as the parasites pass into the colon they typically encyst
- cysts are found in the stool
- > often in enormous numbers
30
Q
Work up of Giardiasis?
A
- stool sample-fecal smear: this is to look for ova and parasites, The dx depends upon finding the distinctive cysts in formed stools, or cysts or the protozoa in liquid stools. A series of 3 or more stool exams on alt. days is therefore recommended
- stool enzyme-linked immunosorbent assay (ELISA) has been shown to be both a specific and sensitive rapid dx tool
- Exam of duodenal contents: may be necessary to establish the dx, as cyst production may be sporadic and not found in the stool by an ovum and parasite fecal smear examination
31
Q
Giardiasis tx?
A
metronidazole (Flagyl): 250 mg 2x daily for 5 days will clear over 90% of Giardia lamblia infections (can become lactose intolerant while having giardiasis -> this will go away after 1 week of tx)
- oral tinidazole and nitazoxinide are alternatives
32
Q
Prevention of giardiasis?
A
- avoid contaminated water sources
- hikers or campers should boil water or use iodine or filtration with a large pore sized filter
- adequate disposal of diapers and frequent hand washing for daycare centers
33
Q
What causes cryptosporidiosis?
A
- a coccidian protozoan parasite (Cryptosporidium hominis)
- associated with contaminated water supplies
- unknown as human pathogen prior to 1976
- one of the most common causes of waterborne illness in the US
34
Q
Where do the cryptosporidium localize to?
A
- the intracellular spheres are found in great numbers just under the outer membrane of the cells lining the stomach or intestine
- oocysts, passed into feces in enormous numbers, are the infective agents
- get into digestive tract but also can get into resp. tract
35
Q
Site of cryptosporidium infection?
A
- epithelial cells of GI tract
- Has affected other tissues such as respiratory tract tissues and conjunctiva of the eye
- infectious dose
36
Q
Sxs of Cryptosporidium?
A
- some individuals can be asymptomatic
- incubation period: 7-10 days (range 3-28)
- sxs include:
stomach cramps, pain, watery diarrhea, dehydration, vomiting, and fever
severe sxs: profuse, watery diarrhea, severe malabsorption, electrolyte imbalance and marked wt loss
37
Q
Dx of Cryptosporidium?
A
- usually made by examining stool specimens. 3 stools may be required. Microscopy with an acid fast stained stool smear is usually dx (acid fast stain**)
- enzyme immunoassay for greatest sensitivity and specificity or molecular methods using PCR
38
Q
What is usually dx test for cryptosporidium?
A
- acid fast stain on stool
39
Q
Tx of Cryptosporidium?
A
- Nitazonxanide: can be used for pediatric patients
adults: 500 mg q 12 hours
children (1-3): 100 mg q 12 hours
children (4-11): 200 mg q 12 hours
40
Q
Prevention of cryptosporidium?
A
- water purification and filtration (resistant to chlorine)
- routine testing:
use of 1 micron filter to remove cysts
boil water
the sporocysts are resistant to most chemical disinfectants, but are susceptible to drying and the UV portion of sunlight - drink bottled water when traveling abroad
- wash hands frequently
- this protozoan is susceptible to freezing
- want person to avoid swimming pools after infection has resolved -> can infect pool water
41
Q
What is the common parasite found in large intestine of humans?
A
Entamoeba histolytica is common parasite in large intestine of travelers
- mostly a disease of travelers
42
Q
What are the 3 stages of intestinal amebiasis?
A
- the active amoeba
- the inactive cyst
- the intermediate precyst
43
Q
What are the 2 strains that cause intestinal amebiasis?
A
- Entamoeba histolytica
- Dientamoeba fragilis
44
Q
Pathogenesis of Entamoeba histolytica?
A
- fecal-oral transmission
- cyst is ingested: the trophozoite emerges from the ingested cyst in the stomach and duodenum.
- Each of which divides again to produce 8 small trophozoites per infective cyst
- these pass to the cecum and produce a population of lumen-dwelling trophozoites
- *** disease results when trophozoites of Entamoeba histolytic invade the intestinal epithelium
- mucosal invasion with the aid of the proteolytic enzymes occurs through the bowel wall
- causes discrete ulcers with a pinhead-sized center and raised edges, from which mucus, necrotic cells, and amoebas pass
- Subsequent spread may coalesce colonies of amoebas, undermining large areas of mucosal surface
- trophozoites may penetrate the muscular coats and occasionally the serosa, leading to perforation into the peritoneal cavity
- secondary bacterial invasion, and accumulation of neutrophilic leukocytes can occur.
45
Q
Extraintestinal infection of Entamoeba histolytic amebiasis is what?
A
- metastatic, amoebas spread through the blood
- rarely occurs by direct extension from the bowel
- By far the most common form is amoebic hepatitis, or liver abscess (4% or more common of clinical infections): this is assumed to be due to micro emboli including trophozoites carried through portal circulation.
