18. Protozoa (Cryptosporidium) Flashcards
why study Cryptosporidium? (3)
- Its importance as a water pollutant.
- A remarkable opportunist, taking advantages of the defective immune system of its host.
- Emerging or Re-emerging disease?
what are the types of emerging diseases?
- Not occurred in humans before -This type is difficult to establish and probably rare.
- Occurred previously but affected only small numbers of people in isolated places.
- Occurred throughout human history but have only recently been recognized as distinct diseases.
what are re-emerging diseases?
Diseases that once were major health problems globally or in a particular country, and then declined dramatically, but are again becoming health problems for a significant proportion of the population
what is an example of an emerging disease that was not seen in humans before? (#1)
Ebola - hemorrhagic fever
what are 2 examples of emerging diseases that occurred previously but only affected small numbers before (#2)
Lyme borreliosis
AIDS
what is an example of a disease that has occurred in human history but had only been recognized as a distinct disease? (#3)
Cholera
Pandemic influenza
what group of emerging diseases does Zika fall into?
2 - emerging diseases that occurred previously but only affected small numbers before
what is the association with Zika that caused the CDC to issue a travel alert to several countries in South America including Mexico?
Microcephaly in neonates infected trans-placentally
how is Zika transmitted?
through the bite of the Aedes mosquito
what is the phylum of Cryptosporidium?
Apicomplexa
what are Coccidia?
a group known as the apicomplexa (phylum)
what are the 3 different niches of coccidia?
- The species of coccidia developing in the gastrointestinal tract of vertebrates
- Those developing extra intestinal
- Vector-borne
what is the hallmark of the apicomplexa?
lack of axonemal locomotive structure
what is the hallmark of Myzozoa?
they feed through myzocytosis (sucking)
what is the hallmark of alveolata?
having a cavity - it means organisms with cavities
how many predominantly distinct genotypes are there of C. parvum, seen in humans?
2
what is the infective stage of C. parvum?
oocysts
where is the infective stage of C. parvum found?
in the environment
what is the vegetative stage of C. parvum?
sporozoites
what does the vegetative stage of C. parvum cause?
the pathology
what is the asexual life cycle of C. parvum?
a) Oocysts excyst in the small intestine
b) The 8 sporozoites attach to the villi
c) Trophozoites reproduce asexually (schizogony)
d) Develop into type 1 meronts
e) Containing 8 merozoites (Some can cause autoinfection)
what is the sexual life cycle of C. parvum?
f) Other meronts become type II meronts containing 4 type II merozoites developing into
g) Microgamonts ♂
h) Macrogamonts ♀
i) Zygotes develop into oocysts
j) Some have thick walls and are excreted in the environment
k) Some have thin walls and reinfect the host
what is the machinery for penetrating the host cell?
the apical complex
what does the oocyst have at the end on the wall?
a suture
what is the use of the suture on the wall of the oocyst?
The suture dissolves during excystation, opening the wall to 4 sporocysts each containing 2 sporozoites
by what route is C. parvum transmitted?
the fecal oral route
is Crypto a zoonosis?
yes
is C. parvum host-specific?
non
what can increase transmission of C. parvum?
Person-to-person contacts
Person-to-animal contacts
Using water for drinking or recreational purposes
what contributes to the pathology of C. parvum?
- Metabolites secreted by Cryptosporidium.
- Inhibition of glucose-stimulation affecting Na absorption.
- Increase production of mucosal prostaglandin which can inhibit NaCl absorption leading to secretory diarrhea.
- Leukocytes can produce high levels of prostaglandins.
- Alterations in intestinal permeability due to the immune response to the parasite. i.e.: Increased secretions of cytokines like IFN-gamma and transforming growth factor (TGF).
which groups are at risk for C. parvum infection?
- workers:
- verinarians
- farmers
- medical professionals
- day-care centers - immunodeficient people
what are social factors that increase risk for C. parvum?
Social Factors: Family Sexual activities Children (day care) Pet’s owner Travelers Drinking non-filtered water
what are the necessary steps of water analysis for C. parvum?
- At least 50 liters of water must be filtered (1 micron porosity)
- Wash the filter with water
- Centrifugation
- Staining
- Microscope
- Efficacy about 6.3%
what are the new detection methods for C. parvum?
- Antibody-based (ELISA)
2. DNA-based (PCR)
what are the issues with the “new” methods
- Both tests suffer from non-specificity (other species and other agents).
- Both are expensive.
- Neither necessarily distinguishes viable from non-viable oocysts.
where does Crypto reside in the intestine?
at the apical surface of the intestinal epithelial cells and doesnt invade the deeper layers
which branch of the immne system is stimulated by moderate to severe infections?
both, innate and aquired branches
what is observed in mucosal infection?
the presence of macrophages and neutrophils at the site of infection
why is Crypto such a threat to surface water and the environment?
because it can be passed between all groups, man/animals/env/imported livestock/domestic animals which increases its abundance in nature
what is the supreme art of controlling infectious diseases?
prevention
- Faubert
what are the species of apicomplexa inhabiting the intestinal niche?
Eimera
Isospora
Cyclospora
Cryptosporidium
which are the species of coccidia inhabiting the extra-intestinal niche?
Neosporia
Sarcocystis
Toxoplasma
which are the species of coccidia which are vector borne?
Plasmodium
Babesia
Theileria
(mosquito and tick vectors)
