LEC 36 & 37 Blood and Tissue Protozoans Flashcards
(43 cards)
1
Q
What is Plasmodium?
A
Unicellular eukaryotic parasite (protozoan)
More than 150 species that infect many vertebrates
1
Q
What are the 5 plasmodium species that infect humans?
A
- P. falciparum
- P. vivax
- P. ovale
- P. malariae
- P. knowlesi
2
Q
What is the vector for Plasmodium?
A
transmitted through the bite of a female Anopheles mosquito
A. gambiae most important species
2
Q
What occurs in the Exoerythrocytic stage of the plasmodium life cycle?
A
- Mosquito bites host and injects anticoagulants along with the sporozoite
- Sporozoite (motile) travels (via blood or lymph) to the liver and invades hepatocytes and then begins asexual replication
- Merozoites are produced and burst open the hepatic cell releasing themselves into the blood
Hypnozoites: P. vivax and P. ovale; they lie dormant for a while then become active
No pathology or disease associated with this stage
3
Q
What occurs during the Erythrocytic cycle of the plasmodium life cycle?
A
- Merozoites just released into blood will infect an RBC
- Asexual replication occurs in the RBCs which form distinct shapes of the RBC (Ring, Trophozoite, Schizont, Merozoite)
- RBC bursts releasing merozoites and starting the cycle anew
Clinical disease associated w/ high rates of replication
3
Q
What stage of the intraerythrocytic cycle are these RBCs in?
Hint: Shape of the cell?
A
Rings
4
Q
What stage of the intraerythrocytic cycle are these RBCs in?
Hint: shape of the cell?
A
Trophozoites
5
Q
What stage of the intraerythrocytic cycle are these RBCs in?
Hint: the shape of the cell?
A
Schizonts
6
Q
What stage of the intraerythrocytic cycle are these RBCs in?
A
Gametocytes
7
Q
What happens during the sexual cycle of the Plasmodium life cycle?
A
- The mosquito sucks the blood of infected person
- The microgamete (male) and the Macrogamete (female) do sex and form a diploid zygote within the mosquito
- Meiosis occurs and forms Ookinete (motile)
- Ookinete lies in between epithelium and basal lamina and forms an Oocyst–> replication
- Sporozoites released in mosquito where they travel to salivary glands to be injected in next person via mosquito bite
8
Q
What are the clinical signs and symptoms of uncomplicated malaria (mild)?
A
- Classic attacks last 6-10 hours and occur every 2 days (Tertian) or 3 days (Quartan) - fever cycle
- pt presents w/ fever, chills, sweats, BAs, HA, N/V, malaise
- physical findings: elevated temp, perspiration, fatigue, hepatosplenomegaly, jaundice, weakness, increased respiration rate
9
Q
Explain the tertian fever cycle.
A
- Replication takes 48 hours
- after initial 48 hours, pt will have fever (day 1)
- Day 2, pt will NOT have fever
- Day 3 (48 hours later) the pt will have fever again
P. vivax and P. ovale replicate with Tertian cycle
10
Q
Explain the quartan fever cycle.
A
- Replication takes 72 hours
- pt will exhibit fever after initial 72 hours (day 1)
- Days 2 & 3, pt will NOT have fever
- Day 4 (72 hours later), pt will have fever again
P. malariae replicates this way
11
Q
What do you know about P. vivax?
A
- Most prevalent species; less common in W. and Central Africa
- Invades reticulocytes
- Tertian fever cycle - benign
- Typically not associated with disease, bc reticulocyte count in circulating blood is low
- Has dormant exoerythrocytic cycle which can last 1-5 years (hypnozoite)
12
Q
What do you know about P. ovale?
A
- Low frequency of infxn in humans
- Similar geographic range as vivax but more common in subsaharan Africa
- Virtually identical to vivax clinically and morphologically - reticulocytes
- Tertian fever cycle
- Hypnozoite (same as vivax)
13
Q
What do you know about P. malariae?
A
- Low frequency of infxn in humans
- Wide global distribution
- Prefers mature RBCs
- Parasitemia <1%
- Quartan fever cycle
- Recrudence up to 30 years - can result in nephrotic syndrome
14
Q
What do you know about P. falciparum?
A
- Common worldwide
- Invades erythrocytes of all ages
- Produces the highest parasitemia in humans - up to 50%
- Poses greatest risk of mortality
- Capable of sequestering in blood vessels
- Adherence to endothelial cells and adjacent RBCs
- Typically, does not display a synchronous erythrocytic cycle
- Tertian fever cycle – malignant
Lots of diseases associated with P. falciparum
15
Q
What are some of the diseases/pathologies that P. falciparum malaria can cause?
A
- Cerebral malaria - confusion, impairment of consciousness, coma, seizures
- Severe anemia - hemolysis
- Hemoglobinuria
- Acute respiratory distress syndrome
- Acute kidney failure
- Shock-like syndrome
- Placental malaria - Premature delivery, low birth weight, loss of fetus
16
Q
What do you know about Bebesia microti?
A
- Intracellular protozoan parasites
- Primary cause of Babesiosis in US
- NE US and Upper Midwest - same range as Lyme disease
- Transmitted by nymph stage of Ixodes scapularis - deer ticks (also same tick that carries Lyme)
- Natural hosts are mice, voles, cattle - humans are accidental host
17
Q
What are the major differences in the life cycle of Babesia compared to Plasmodium?
A
- Vector: uses tick and not mosquito
- Babesia directly infects RBCs and does NOT go to the liver first
- Once inside RBC, Babesia only makes 4 merozoites where Plasmodium makes many and lyses the cell
18
Q
What are the clinical symptoms of Babesiosis?
A
- Often asymptomatic (25-50%)
- Flu-like symptoms
- Can be severe in: Immunocompromised, Splenectomy pts, elderly
- Severe disease: Hemolytic anemia, low and unstable BP, DIC, thrombocytopenia, kidney failure, death
19
Q
How do you diagnose Babesia infxn?
A
- Thick and thin blood smears w/ Giemsa - however parasitemia is often <0.2%
- Rings form (like Plasmodium) and a tetrad shape forms in RBCs
- Send to CDC for confirmation
- Serology tests
- PCR
20
Q
How do you treat Babesia infxn?
A
- Combo of Azithromycin and Atovaquone - mild disease
- Combo of Clindamycin and quinine - severe disease
- Blood transfusion
21
Q
What do you know about Trypanosoma brucei?
A
- Extracellular flagellated protozoa
- 3 sub species: T. brucei - gambiense/rhodesiense/brucei
- Transmitted by Tsetse fly - Trypomastigotes resides in the salivary glands
22
Explain the life cycle of T. brucei.
* Epimastigotes in salivary glands divide and produce trypomastigotes
* Tsetse fly bites host releasing trypomastigotes into host blood
* Trypomastigotes replicate via binary fission in blood, lymph, and CNS
* New fly bites host and takes up newly produced trypomastigotes and their flagellas shorten forming epimastigotes
* Process repeats
23
What do you know about T. b. gambiense?
* Tropics of central and western Africa
* Humans are primary reservoir (anthroponotic)
* Chronic infxn can result in death
* Red sore around bite developes within 1-3 weeks
* Weeks to months before later symptoms develop
* Death can occur after several years of infxn
24
What do you know about T. b. rhodesiense?
* Grasslands of Eastern Africa
* Domestic animals and wild game animals are reservoirs
* Disease progresses rapidly - symptoms in 1-3 weeks; death within 9-12 months
25
What are the clinical symptoms of T. b. gambiense?
* **Hemolymphatic phase:** disseminates through blood and lymph - Recurrent fever, lymphadenopathy, rash, HA, Winterbottom's sign (swelling of post. cervical lymph node)
* **Neurological phase:** parasite crosses blood brain barrier & infects CNS - occurs 1-2 years later, Sleeping Sickness (Lethargy, tremors, inability to move, insomnia, daytime sleeping, confusion, reduced coordination, progresses to comatose state)
26
What are the clinical symptoms of T. b. rhodesiense?
* **Hemolymphatic phase:** disseminates through blood and lymph - Occurs more rapidly, Large sore (chancre) @ bite site, Lymphadenopathy is UNCOMMON, higher #'s of parasite in blood
* **Neurological phase:** parasite crosses blood brain barrier & infects CNS - occurs more rapidly, kidney damage & myocarditis may kill host prior to CNS pathology development
27
How do you diagnose a Trypanosome infxn?
* Thick/thin blood smear stained with Giemsa - T. b. rhodesiense easy to identify on smears d/t high replication
* Exam of lymph node aspirate from post. cervical lymph node for gambiense
* Spinal tap must be performed for all confirmed cases of Trypanosomiasis to determine course of tx
28
How do you treat a Trypanosome infxn?
| for both rhodesiense and gambiense
* Hemolymphatic phase: **suramin** (rhodesiense) or **pentamidine** (gambiense)
* Neurological phase: **melarsoprol** (rhodesiense) or **eflornithine-nifurtimox** (gambiense)
* Examination of CSF for 2 years to ensure no relapse
| only pentamidine widely available; rest must come from CDC
29
What do you know about T. cruzi?
* Found in Mexico, Central and South America - associated with impoverished areas
* Transmitted by "kissing bug" - reduviid bug or triatomine bug - found in AR but not with T. cruzi
* Feeds on humans, mammals, and birds (reservoirs)
* Resides in intestine of reduviid bug
* Transmitted when feces deposited by the biting insect are introduced into the bite by scratching
30
Explain the life cycle of T. cruzi.
* Bug bites host and defecates (contains parasite) - host scratches infecting the bite wound with the trypomastigote
* Trypomastigote travels to smooth muscle (heart) and rounds up and begins replicating
* New trypomastigotes are released into the blood to be taken up by a new vector in a blood meal
* Within the vector, the flagella shorten forming epimastigotes which multiply in the midgut
31
What is the name of the disease caused by American Trypanosomiasis?
**Chagas Disease**
32
What are the clinical symptoms of Chagas disease?
* **Acute phase:** produces local rash & edema at site of infxn; Romana's sign - Site of infxn is often the face, high parasitemia for 2 months, can form ulcer (chancre) at site of bite, often asymptomatic
* **Chronic phase:** parasite resides in multiple tissues especially heart and digestive smooth muscle - low parasitemia, can be asymptomatic for life of individual, Life-threatening heart and GI disease in 20-40% of chronically infected but may take years to manifest
33
How do you diagnose Chagas disease?
* Thick/thin blood smear stained with Giemsa
* Serological tests (chronic)
34
How do you treat Chagas disease?
* **Nifurtimox and Benznidazole**
* Less effective against chronic infxn
* Nifurtimox not FDA approved but is still available from CDC
35
What do you know about Leishmania?
* Flagellated protozoan parasite
* Found primarily in tropical and subtropical regions
* Many different species
36
How is Leishmania transmitted?
* Transmitted by phlebotomine sandflies
* Rodents and dogs are major reservoirs
* Anthroponotic: human-vector-human
* Infxns in US are primarily seen in US troops and gov contractors returning from N. Africa and Middle East
37
What kind of cells does Leishmania infect?
Phagocytic cells
| Prefers macrophages over neutrophils
38
What are the clinical manifestations of Leishmaniasis?
* **Cutaneous:** local skin infxn; ulceration - weeks to months, often heal spontaneously
* **Mucocutaneous:** rare, occuring months after clearance of cutaneous lesion - primarily occurs in Bolivia, Brazil, & Peru
* **Viseral (kala-azar):** weight loss, hepatosplenomegally, anemia, fever - within months to years; 100% fatal in 2 years if untreated
39
How do you diagnose Leishmaniasis?
* Histological exam of biopsy material (skin ulcer, LN aspirates, buffy coat of venous blood, bone marrow aspirate)
* Amastigotes visualized with Giemsa or H&E stains, but are indistinguishable from T. cruzi
* in vitro culturing of parasites from bx material
* Species ID by isoenzyme or DNA analysis
40
How do you treat Leishmaniasis?
* **Sodium stibogluconate** - not FDA approved
* **Amphotericin B** - Viseral; given IV
* **Miltefosine** - select new world spp.; tx of cutaneous, mucosal, and viseral
* **Sitamaquine** - viseral
* **Fluconazole, Ketoconazole, Itraconazole** - oral; not FDA approved
