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
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?
ReplyDeleteJessica'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!
ReplyDeleteAs 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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