Sunday, October 14, 2012

Babesia microti Life Cycle


Babesia microti is a blood parasite that infects humans using ticks as insect vectors.  It is important to understand the lifecycle of Babesia microti in order to prevent infection.  The life cycle begins when a tick takes a blood meal from a mouse or other small mammal and introduces sporozoites form in to the host (Leiby, 2011).  The sporozoites then enter the hosts’ erythrocytes, or red blood cells, and reproduce by budding, a type of asexual reproduction.  This process yields both male and female gametes.  The tick then takes another blood meal and ingests the gametes.  Once inside the tick the gametes transform in to sporozoites.  Sporozoites are the infective stage to humans so when a tick containing sporozoites takes a blood meal from a human they will become infected.  Inside the human host Babesia microti is able to cycle between the merozoite form and the trophozoite form inside the blood.  Both the trophozoite and the merozoite forms are diagnostic stages to humans, or when the disease will start showing symptoms.  When Babesia microti multiplies within the human the symptoms of the disease will become more and more apparent (Becker et al, 2009).  Once Babesia microti has infected a human it can no longer infect any other host.  The only way to spread the disease after a human has been infected is through blood transfusions.  
Symptoms of this parasite will usually become apparent between 1 and 9 weeks after transmission has occurred.  Some of the minor symptoms include fever, headache, chills, and muscle pain (Leibly, 2011).  However in some individuals the symptoms can be more serious, causing premature breakdown in blood cells known as hemolytic anemia.  Many people who become infected are able to tolerate the symptoms but the parasite can have serious consequences on elderly, young children, and people who are already immune-compromised (Leibly, 2011).  These individuals risk facing respiratory failure, hemolysis, blood pressure instability, and myocardial infarctions. 
Studying the life cycle and symptoms of Babesia microti are important to preventing its transmission.  One of the main problems this parasite poses is that it can be transmitted through blood transfusions and is more complicated to screen for than other blood illnesses (Liebly, 2011).  Understanding the symptoms and lifecycle of this parasite can help with diagnostic testing and lead to more accurate blood screening.


Leibly, D. A.2011. Transfusion-Transmitted Babesias. Clin. Microbiol. Rev. 24:14-28.

Becker, C. A. M., A. Bouju-Albert, M. Jouglin, A. Chauvin, and L. Malandrin. 2009. Natural transmission of zoonotic Babesia spp. by Ixodes ricinus ticks. Emerg. Infect. Dis. 15:320-322

3 comments:

  1. So it seems that the Babesia microti lifecycle has some similarity to that of malaria and symptoms similar to Kala-Azar, Chagas disease, and malaria. It is amazing how diverse parasite lifecycles and pathology are, but that there is often some similarity amongst the diversity. If humans can only pass on the infection by blood transfusions, then prevalence isn't that high, right?

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  2. Jessica's got a good point. How are Babesia species related to these other parasites. It sounds like they are closely related. Scary stuff, especially since this is pretty common here in Connecticut!

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  3. As if we didn't have enough to worry about when it comes to ticks... Really neat article! This one is nice because just about all of us have been bitten by a tick, though I've never heard of this parasite before. I guess this is one more reason why hospitals have to be cautious when giving blood transfusions.

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