M12: Medical Parasitology Flashcards
Parasitism is a type of symbiotic relationship where _.
Parasitology is the study of this relationship and includes the study of parasitic (3).
An important response of humans to the presence of most parasites is _.
However, many other aspects of a vigorous immune response do not occur in response to a parasitic infection. Parasites use _, in which a pathogen produces molecular structures that resemble molecular structures within the human host.
one organism depends on another organism for survival at some expense to the host organism
protozoa, helminths, and arthropods
eosinophilia
molecular mimicry
How can parasites be distinguished from bacteria?
Parasites are (eukaryotic / prokaryotic) organisms belonging to the kingdoms of _, _(both previously classified under Protista) and _.
In contrast to bacteria, they
- Possess a _ (bacteria do not)
- Possess _ ribosomes (bacteria have _)
- May possess _ (bacteria do not)
- Do not possess a _ (bacteria have a _)
- Reproduce _ (bacteria do not)
eukaryotic
Protozoa, Chromista, and Animalia
nucleus
80S (70S)
mitochondria
cell wall (peptidoglycan cell wall)
sexually
What types of parasites exist?
_ are protozoa
_ include helminths and ectoparasites (insects and arachnids).
Protista
Animalia
What types of parasites exist?
Endoparasites are parasites that live _.
They can be _ or _.
inside the body of the host
protozoa or helminths
What types of parasites exist?
Protozoa are (simple / complex) organisms that are generally (unicellular / multicellular) and free living.
They are divided into four distinct groups on the basis of their methods of locomotion.
These means of locomotion include:
- _ (Giardia lamblia)
- _
- _ (Entamoeba histolytica)
- _ (Plasmodium falciparum)
Many protozoa have specific _ distributions – this is a key to considering the possibility of infection clinically.
simple
unicellular
- flagella
- cilia
- pseudopods
- apical microtubule complex
geographic
What types of parasites exist?
Helminths are _.
The helminths can be divided into _ (_) and _.
The flatworms can further be divided into _ () and _ ().
As with the protozoa, many helminths have specific _ distributions.
Helminths cause disease by a variety of mechanisms such as _ (intestinal obstruction), competition for _, or _ of host tissues.
worms
roundworms (nematodes) and flatworms
tapeworms (cestodes) and flukes (trematodes)
geographic
mechanical effects
nutrients
invasion
What types of parasites exist?
All medically important ectoparasites belong to the Phylum _ which include members of class _ (eg: lice and fleas) and class _ (eg: ticks, spiders).
They fulfill a life cycle requirement through interaction with the _ or _ of the host.
Examples include (3)
In some cases the manifestations of disease are purely the result of the ectoparasite _ (allergic reaction to the deposited feces of scabies causes severe itching).
In other cases, ectoparasites are vectors of _, _, or _ infection.
Arthropoda
Insecta
Arachnida
skin or hair
lice, scabies and ticks
being on the skin or hair
bacterial, viral, or protozoal
What is a parasite’s life-cycle and what are the common modes of transmission?
The life-cycles are the different _ that parasites take, as they _ and _ in different hosts and different environments.
Many parasites require (#) host species to complete their life cycle.
The definitive host is where the parasite reaches _ whereas the intermediate host harbors the _ or _ stage of the parasite.
The number or type of hosts may be characteristic of a _ of parasites.
For example, _ (eg: Schistosoma) would always have mollusks as their first intermediate host.
forms
develop
reproduce
two or more
sexual maturity
asexual or larval
group
trematodes or flukes
What is a parasite’s life-cycle and what are the common modes of transmission?
The _ is a common mode of transmission of parasites.
Raw or improperly cooked food may harbor the infective ova or larvae of parasites (_).
Other parasites such as hookworms and Schistosoma infect their hosts by _.
Parasites may also be transmitted through _ such as in the case of malaria and filariasis. Prevention of these infections may be done through _.
Other modes of transmission include _ (such as in Toxoplasma), inhalation of _ (Enterobius), and _ (Trichomonas).
fecal-oral route
cystercercosis
skin penetration
insect vectors
vector-control
vertical transmission
eggs
sexual intercourse
What are some of the medically important protozoa?
Entamoeba histolytica:
_ is the most important amoeba to infect humans.
The amoebae, like other protozoa, are _ and (unicellular / multicellular).
They possess a _ and an _, within which the _ and _ exist.
Entamoeba histolytica
microscopic
unicellular
cytoplasmic membrane
endoplasm
nuclei and mitochondria
What are some of the medically important protozoa?
Entamoeba histolytica:
Life cycle:
A _ that is excreted into the environment by another person is ingested by a person through _.
The cyst undergoes _ in the gut, becoming a _.
This attaches to the colonic mucosa, and can sometimes penetrate allowing it to reach the portal circulation causing an _.
Various triggers can initiate formation of new _ in the gut, which can then be shed into the environment, thereby completing the life cycle.
Geographic distribution:
(Commonly / Rarely) acquired in the United States (occasionally in institutions for the cognitively impaired and in gay men). Many cases arise in _.
Clinical manifestations (2)
Most common treatment:
_ and subsequent _ or _ to eradicate intraluminal cysts.
cyst
fecally contaminated food or water
excystation
trophozoite
amebic liver abscess
cysts
Rarely
Mexico
Bloody diarrhea (amebic dysentery) liver abscess
Metronidazole
paromomycin or diloxanide
What are some of the medically important protozoa?
Acanthamoeba:
_ can get infection of the _ with this amoeba, particularly if they use “homemade saline” for lens disinfection or if they wear their lens while swimming in surface water.
Contact lens wearers
cornea
What are some of the medically important protozoa?
Naegleria fowleri:
This organism also nicknamed “brain-eating ameba” is commonly found in _ and _.
It infects people by entering through the nose when _ or _.
Once the ameba reaches the brain through the cribriform plate it causes a usually fatal _.
Recent cases occurred in the _ USA. There is no effective treatment.
warm freshwater (lakes, hot springs) and soil
swimming or diving
meningo-encephalitis
Southern
What are some of the medically important protozoa?
Giardia lamblia:
Clinical manifestations: _.
Most common treatment: _.
Diarrhea
Metronidazole
What are some of the medically important protozoa?
Cryptosporidium spp.:
Clinical manifestations: _.
Diarrhea
What are some of the medically important protozoa?
Microsporidia:
Microsporidia is a designation encompassing more than 100 genera and 1000 species of organisms.
Microsporidiosis is an infection which, like cryptosporidiosis, mainly causes _ and is predominantly a problem in _ people with human immunodeficiency virus (HIV) infection.
_ may be useful as therapy, but even more important is the restoration of immune function by use of _ medications.
diarrhea
immunosuppressed
Albendazole
anti-HIV
What are some of the medically important protozoa?
Trichomonas vaginalis:
Trichomoniasis is among the most common sexually transmitted infections (STI) in women. Its incidence is highest in _ and in _. Rates among newly incarcerated women approach 50%.
Most men who carry T. vaginalis are _.
Life cycle:
T. vaginalis is highly _. No _ is needed for transmission. Infected vaginal discharge contains 10-100,000 protozoa per mL. The organism is mechanically passed from _ to _ and then to another _. Although the organisms can survive on damp towels and clothes for hours, there has been no documented transmission through this means.
Geographic distribution: _
Clinical manifestations:
Infected women note _ and _ or _. Physical examination reveals a copious discharge, often with bubbles, giving it a frothy appearance. There is a characteristic _ odor.
Diagnosis:
A _ specimen, examined microscopically, will reveal _-shaped, _ organisms with a characteristic _ motility.
Most common treatment: _ (treat sexual partner as well!)
women with multiple sexual partners and in groups at risk for other sexually transmitted diseases
asymptomatic
site-specific
vector
female to male
female
Worldwide
vaginal discharge
vulvovaginal soreness
irritation
fish-like
wet mount
pear
flagellated
twitching
Metronidazole
What are some of the medically important protozoa?
Babesia:
_ is an infection caused by the protozoa Babesia which, like Plasmodium spp, infects _ but is very different from malaria. The classic microscopic diagnosis is made when an _ is visualized.
Risk factor for severe disease and relapses is functional _.
Life cycle:
Part of the life-cycle occurs in _ (deer and white-footed mice), while _ (not mosquitoes) are the vectors of infection.
Geographic distribution:
_ United States (especially in Nantucket Island, Martha’s Vineyard and Cape Cod but also seen in Pennsylvania),
Most common treatment:
_ and _ or _ and _
Babesiosis
erythrocytes
intra-erythrocytric “Maltezer cross”
asplenia
non-human vertebrates
ticks
Northeastern
clindamycin and quinine
atovaquone and azithromycin
What are some of the medically important protozoa?
Leishmania spp.:
The Leishmania spp. that infect humans are found as intracellular _ in macrophages in humans and extracellular _ in the gut of sandflies. There are numerous species, none of which are endemic in the United States.
Geographic distribution:
Leishmaniasis is common in _ and _ America and in the _ and _.
Clinical manifestations:
Dependent on the host’s cell-mediated immune responses. _ is most often seen in American troops who were infected in Iraq or Afghanistan. _ (kala azar) will manifest as _ and _.
amastigotes
promastigotes
Central and South
Middle East and Africa
Cutaneous leishmaniasis
Visceral leishmaniasis
fevers
hepatosplenomegaly (enlarged liver and spleen)
What are some of the medically important protozoa?
Trypanosoma spp.:
There are two distinct forms of trypanosomiasis (2)
American trypanosomiasis is found throughout _ and _ America. It is transmitted by “_” and causes _ disease with esophageal and colon _ as well as _. Due to immigration there are carriers in the USA who can propagate the infection through blood transfusions and through mother to child transmission. 1:5000 blood donations in south California and south Florida are positive by serology.
African trypanosomiasis is transmitted by the _ and causes _, an often fatal _.
American and African
Central and South kissing bugs Chagas' dysmotility cardiomyopathy
tsetse fly
sleeping sickness
meningo-encephalitis
What are some of the medically important protozoa?
Toxoplasma gondii:
Clinical manifestations:
_ through perinatal transmission and reactivation _ in T-cell immunocompromized patients.
Eye infections (retinitis) encephalitis
Helminths: Intestinal Roundworms: - Ascaris lumbricoides - Hookworm (Necator americanus, Ancylostoma duodenale) - Pinworm (Enterobius vermicularis) - Strongyloides stercoralis - Whipworm (Trichuris trichiura)
Typical life-cycle:
Female worms in the _ of a human produce eggs. The eggs embryonate and infect humans by _ (Ascaris, Enterobius, whipworm) or by _ by larval forms (hookworm and Strongyloides).
The infections are most prevalent in _ areas where children play on contaminated soil around homes or where farmers use human excrement (“night soil”) for fertilizing crops. The one exception is _ which occurs commonly in the United States and is not associated with any specific socioeconomic level. It is common in siblings within the same family.
Clinical manifestations:
Ranges from _ (pinworm) to _ (strongyloidiasis). Soil-transmitted helminth infection (such as with Ascaris or Trichuris) usually present with non-specific _ and/or _.
Treatment:
_ or _
_ may also be used for E. vermicularis. In high prevalence countries periodic mass-treatment is provided since _ is so common.
gut
ingestion of infective eggs
penetration of the skin
impoverished rural
pinworm
perianal itch
disseminated infection
abdominal discomfort and/or microcytic anemia
Albendazole/mebendazole or ivermectin
pyrantel
re-infection
Helminths: Intestinal Roundworms (5)
Ascaris lumbricoides
Hookworm (Necator americanus, Ancylostoma duodenale)
Pinworm (Enterobius vermicularis)
Strongyloides stercoralis
Whipworm (Trichuris trichiura)
Helminths: Tissue Nematodes (filaria) (4)
Onchocerca
Wuchereria
Brugia
Trichinella
