1. Babesia
Babesiosis

2. is caused by microscopic parasites that infect red blood cells
and are spread by hard ticks.
Transmission
by the bite of infected Ixodes scapularis ticks— nymph stage
People can get infected with Babesia parasites in several ways:
The main way is through the bite of an infected tick—during outdoor activities

3. A less common way is by getting a transfusion from a blood donor who has a Babesia infection but does not have any symptoms.
No tests have been licensed yet for screening blood donors for Babesia.)
Rare cases of congenital transmission
—from an infected mother to her baby (during pregnancy or delivery)—have been reported.

5. The parasite is spread by the young nymph stage of the tick,
which is seeking for a blood meal during warm months in areas with woods, bush, or grass.
Infected people might not recall a tick bite because I. scapularis nymphs are very small

6. Classification Phylum: Apicomplexa Class: Aconoidasida
Order: Piroplasmida
Families: Babesiidae and Theileriidae
Genus: Babesia.

7. Causal Agents: More than 100 Babesia species have been reported
Few have caused documented cases of human infection
These include B. microti, B. divergens, and
B. duncani,
and a currently unnamed agent designated MO1.

9. The Babesia microti life cycle involves two hosts, which include a rodent, primarily the white-footed mouse, Peromyscus leucopus, and a tick in the genus Ixodes.
During a blood meal, a Babesia-infected tick introduces sporozoites into the mouse host . Sporozoites enter erythrocytes and undergo asexual reproduction (budding) .
In the blood, some parasites differentiate into male and female gametes, although these cannot be distinguished by light microscopy .

10. The definitive host is the tick
The definitive host is the tick. Once ingested by an appropriate tick , gametes unite and undergo a sporogonic cycle resulting in sporozoites .
Transovarial transmission (also known as vertical, or hereditary, transmission) has been documented for "large" Babesia species but not for the "small" Babesia, such as B. microti .

11. Humans enter the cycle when bitten by infected ticks.
During a blood meal, a Babesia-infected tick introduces sporozoites into the human host . Sporozoites enter erythrocytes and undergo asexual replication (budding) .
Multiplication of the blood-stage parasites is responsible for the clinical manifestations of the disease. Humans usually are dead-end hosts.
However, human-to-human transmission is well recognized to occur via contaminated blood transfusions .

12. Clinical features
Many people who are infected with Babesia microti feel fine and do not have any symptoms.
Some people develop nonspecific flu-like symptoms, such as fever, chills, sweats, headache, body aches, loss of appetite, nausea, or fatigue.
Because Babesia parasites infect and destroy red blood cells, babesiosis can cause a special type of anemia called hemolytic anemia.
This type of anemia can lead to jaundice (yellowing of the skin) and dark urine.

13. Babesiosis can be a severe, life-threatening disease, particularly in people who:
do not have a spleen;
have a weak immune system for other reasons (such as cancer, lymphoma, or AIDS);
have other serious health conditions (such as liver or kidney disease); or
are elderly.

14. Complications of babesiosis can include:
a low and unstable blood pressure;
severe hemolytic anemia (hemolysis);
a very low platelet count (thrombocytopenia);
disseminated intravascular coagulation (also known as “DIC” or consumptive coagulopathy), which can lead to blood clots and bleeding;
malfunction of vital organs (such as the kidneys, lungs, and liver); or
death.

15. Diagnosis
Stained blood smear.
Trophozoites within an erythrocyte that appear in a tetrad formation are indicative of Babesia.
Treatment
oral atavaquone or azithromycin

17. Prevention and control
The most effective public health measure for Babesia is avoidance of tick exposure.
This can be performed through personal prevention strategies such as avoiding tick-infested areas remaining covered with light clothing,
searching for ticks after being outdoors, and removing discovered ticks from the skin.
Other preventive measures include applying diethyltoluamide (DEET), a common repellent that is effective against ticks and insects.
(For people who react adversely to DEET, alternative insect repellents should be used

18. References
Gelfand, Jeffrey A.; Vannier, Edouard. Harrison's Principles of Internal Medicine McGraw-Hill's Access Medicine. Chapter 204.
Vannier E, Krause PJ (June 2012). "Human babesiosis". N. Engl. J. Med. 366 (25): 2397–407. doi: /NEJMra PMID