Hemolysis

Question 1

Babesia microti

Answer 1

Hemolysis
• Caused by *apicomplexan protozoans of the genus Babesia
• infect RBCs & cause them to lyse which results in a fever.
• Causes *Babesiosis
• When this sporozoan infects and replicates inside a red blood cell, the shape is said to look like a *Maltese Cross
Disease Manifestations
• *Incubation period: 1 - 4 weeks
• *“Summer flu” with fever, chills, sweats, muscle aches, and fatigue that begins gradually and may last for several weeks
• *Hemolytic anemia
• *Splenomegaly, *hepatomegaly, or *jaundice may occur
Transmission
• Definitive host = *Ixodes tick (deer tick)
• Intermediate host = *white-footed mouse
• Dead end host = humans
Diagnosis & treatment
• *Giemsa-stained blood smears to visualized *ring-shaped *trophozoites; often in tetrads (Maltese Cross)
• *Quinine and *clindamycin (or *atovaquone and *azithromycin)

Question 2

Clostridium perfringens

Answer 2

Hemolysis
• *Endospore-forming Gram-positive bacilli/rods
• *Boxcar or rectangular-shape; in pairs or short chains
• Most strains are *anaerobic
• *Capsule
• *Non-motile
- causes *gas gangrene and *food poisoning
- often found in heavy, meaty gravy
Virulence
• Endospores
• *Alpha toxin α
• Enterotoxin (CPE)
• Theta toxin θ
• Epsilon toxin ε
• Iota toxin ι
• DNase
• Hyaluronidase
• Collagenase
Diagnosis
• Rapid grow under anaerobic conditions
• double zone of hemolysis on *blood agar
• *Egg yolk agar is used to demonstrate the presence of the lecithinase (alpha toxin)
- intravascular hemolysis 
• *Spherocytes 
• *Red blood cell ghosts 
Treatment
• *IV high-dose penicillin + clindamycin or tetracycline and *surgical debridement

Question 3

Plasmodium species

Answer 3

Hemolysis
• *Protozoan
- *Malaria is due to five species of Plasmodium sporozoans:
• P. vivax, most common
• P. falciparum, most deadly
• P. ovale
• P. malariae
• P. knowlesi, zoonotic & little known
Disease manifestations
• *Early disease = abrupt onset of fever & chills with headache, myalgia & arthralgia (lysis of RBCs) about 2 weeks after bite
• Synchronization of parasite replication = malarial paroxysm of “cold, hot, wet” lasting hours & recurring for weeks
Transmission
• Definitive host: *Female Anopheles Mosquito
• Intermediate host and reservoir: *People
Complications
• *Anemia is prominent due to hemolysis
• Splenomegaly (in most patients)
•Hepatomegaly (1/3 of patients)
• *“Cerebral malaria” (P. falciparum)
• *“Blackwater fever” = kidney damage (P. falciparum)
• *Relapse (P. vivax and P. ovale
LABS
- *peripheral blood smear stained by *Giemsa
• *Thick smear: erythrocytes are lysed with water; parasites are concentrated for detection of low-level parasitemia; for screening
• *Thin smear: for parasite species identification
• PCR, ELISA
Premunition
• Partial immunity with low level parasitemia
• able to get infected with a malaria parasite and develop a parasitemia, but they are asymptomatic
• What happens is that with enough exposure to various different strains of malaria parasites, antibodies form that can block merozoites from invading the red cells, but these antibodies aren’t perfect.
• So, the person is protected from a high-level of parasitemia and resulting disease, but still harbors the parasites.
• Protected from high-level parasitemia & disease, but from not infection