LEC 36 & 37 Blood and Tissue Protozoans Flashcards
What is Plasmodium?
Unicellular eukaryotic parasite (protozoan)
More than 150 species that infect many vertebrates
What are the 5 plasmodium species that infect humans?
- P. falciparum
- P. vivax
- P. ovale
- P. malariae
- P. knowlesi
What is the vector for Plasmodium?
transmitted through the bite of a female Anopheles mosquito
A. gambiae most important species
What occurs in the Exoerythrocytic stage of the plasmodium life cycle?
- 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
What occurs during the Erythrocytic cycle of the plasmodium life cycle?
- 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
What stage of the intraerythrocytic cycle are these RBCs in?
Hint: Shape of the cell?
Rings
What stage of the intraerythrocytic cycle are these RBCs in?
Hint: shape of the cell?
Trophozoites
What stage of the intraerythrocytic cycle are these RBCs in?
Hint: the shape of the cell?
Schizonts
What stage of the intraerythrocytic cycle are these RBCs in?
Gametocytes
What happens during the sexual cycle of the Plasmodium life cycle?
- 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
What are the clinical signs and symptoms of uncomplicated malaria (mild)?
- 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
Explain the tertian fever cycle.
- 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
Explain the quartan fever cycle.
- 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
What do you know about P. vivax?
- 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)
What do you know about P. ovale?
- 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)
What do you know about P. malariae?
- 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
What do you know about P. falciparum?
- 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
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
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)
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
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
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
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
