Medical Parasitology Flashcards
What organisms are considered in parasitology?
- Protozoa (unicellular eurkaryots)
- Worms or helminths (Platyhelminthes, Nematodes)
- Arthropods (Ticks, mites)
Tropical diseases affect which population the most?
the impoverished (mainly overlapped in developing countries, but it is in the US as well)
Why do these infections remain in the US?
- Quality of sanitation and quality of the water is not good
- Travel and immigration
Malaria is more present on which coast?
East coast
Sources of parasitic infections
- Insect or Tick Bite
- Blood Transfusions
- Water contamination
- Contaminated food
Factors influencing the geography of parasitic infections
- Local ecology
- local habitats
- vectors (mosquitoes and ticks)
- Reservoirs (animal and human) - Local socioeconomic conditions
- sanitation
- water quality
- how frequently exposed to vectors
- local habits and customs
- untreated carriers
Intestinal parasites
- Amoeba
- Flagellates
- Cryptosporidium
Urogenital parasites
Trichomonads
Tissue parasites
- Toxoplasma
- Leishmania
- Trypanosoma
Blood parasites
- Malaria
- Trypanosomes
- Babesiosis
Eye and Brain parasites
- Amoeba
Entamoeba histolytica
- Causes Amoebiasis - causes diarrhea/dysentery
- Extracellular parasite
- Can lead to intestinal, liver and other amebic abcesses
- Fecal-oral transmission
- If remain in the lumen, not a problem. Invasive into mucosa leads to serious issues
- Found in the US, but mostly industrialized countries
- Can be transmitted by anal intercourse
“Flask shaped ulcers”
Entamoeba hitolyitica
How long is E. histolytica viable?
Moist cool conditions = 12 days
In water = 9-30 days
As cysts
Are trophozoites infectious?
No, only from cysts!
The trophozoites die rapidly.
Diagnostic differentiation of amoebae
- Travel Hx and clinical signs
- Demonstration in fecal samples (trichrome stain)
- immunodiagnosis for stool antigen or serology
- EIA & PCR (not used much)
Lots of amoebae don’t cause pathology - make sure you get the right diagnosis!
If you travel internationally and you have your drink “on the rocks”, what are you more likely to get infected with?
Amoebas
they’re even resistant to chlorination
Giardiasis
- Extracellular parasite of large intestine
- Caused by Giardia intestinalis
- Key differentiators: gas, bloating, foul smelling greasy stools
Pathogenesis of giardiasis?
- Adherence of trophozoites to intestinal epithelium via an adhesive disk
- Atrophy of villi and reduced surface for absorption
- Hypersecretion of chloride ions and water in combo with malabsorption leads to diarrhea
Fecal sample looks like 2 eyes and a funky mustache
Giardia intestinalis - you’re seeing the trophozoites
If you have someone that presents with diarrhea and some bloating that lasts for more than 3 days, what should you consider?
Giardiasis is possible, but after 3 days, think cryptosporidiosis.
Major sources of giardia
- water and food
- feces for fertilizer
- cysts are hardy and can survive several months in cold water
- 10-25 cysts sufficient for infection
- Zoonosis (animals are hosts)
- Seasonal peak during late summer
Prevention of giardia
- No vaccine
- Water filtration
- Chlorination is not effective
- Sanitation
Cryptosporidiosis
- Infection of small intestine that causes diarrhea/dysentery
- Fecal oral transmission
- Intracellular parasite (gets in mucosa of intestine)
- caused by cryptosporidium sp.
What is the average incubation period for Cryptosporidium
7 days (ranges from 2-10)
Clinical presentation of cryptosporidiosis
- Watery diarrhea + dehydration + weight loss
- abdominal pain, fever, n/v
- more chronic and severe in immunocompromised patients
Diagnosis of cryptosporidiosis
- Clinical signs
- Direct fluorescent antibody and enzyme immunoassay
- Fecal analysis
Major sources of cryptosporidiosis
- Water and food, but mostly water
- Oocysts can survive chlorination (water and pools arent safe!)
- Zoonosis (many animal hosts)
- Water treatment filtration breakdown (Caused Milwaukee)
How long can crypto oocysts survive in chlorinated water?
10 days
Trichomoniasis
- Infection of urogenital tract (vagina and urethra in females, urethra, seminal vesicles & prostate in men)
- Extracellular parasite that adheres to epithelia
- Sexual or genital contact transmission
- NO CYSTS, only trophozoites
Incubation period and presentation of trichomoniasis
- Incubation = 5-28 days
- Vaginitis with a purulent discharge + vulvar and cervical lesions, abdominal pain, dysuria and dysparen=unia
- Frequently asymptomatic in males, but can have urethritis, epididymitis, prostatitis
Trich complications in women
- Increased HIV transmission and infectivity
- Tubal infertility, atypical PID
- Risk of cervical cancer
- Association with preterm birth and premature rupture of membrane and low birthweight infants
Trich complications in men
- Increased HIV transmission and infectivity
- Urethritis
- Infertility - motility and viability
Diagnosis of trich
- Discharge, strawberry cervix
- Visualization of motile parasite in vaginal secretion (40-60% sensitivity)
- Culture in special media BUT takes 3-7 days
- Antigen detection
- DNA based tests and PCR
Epidemiology and Prevention of trich
- No vaccine
- High risk groups: prison, African American, Drug users, Sex workers
- Prevalence increases with age
- Condoms
- No cysts, only trophozoites
Opportunistic protozoa
- Acanthamoeba (brain, eye)
- Naegleria fowleri (nose to brain)
Naegleria fowleri
Cause of primary amebic meningoencephalitis (PAM) - “brain eating amoeba” - lethal
Usually someone diving that has the amoeba in the water go up the nose to the brain
Acanthamoeba sp.
- Granulomatous amebic encephalitis, esp in immunosuppresed patients.
- Keratitis, particularly assoc with corneal injuries and wearing contact lenses (especially the 30 day contact lenses)
What does opportunistic mean in this case?
They are in the right place at the right time, infecting the right thing…. you don’t have to be immunocompromised.
