Babesiosis is caused by Babesia, a malaria-like protozoan that parasitizes and reproduces within a mammal's red blood cells. Prior to 1906, it was primarily a cattle disease.
Clinically, babesiosis appears to have a wide spectrum of disease severity. Most patients experience a viral-like illness that can last weeks to months but which usually resolves fully. A significant minority of patients are entirely asymptomatic. In patients with a complicating condition, however – such as underlying immunosuppression – the disease course can be severe. Some species of Babesia, such as B. divergens, appear to be more virulent than others.
Symptoms of babesiosis usually begin 1-6 weeks after exposure and are non-specific. Typical early manifestations include intermittent fevers, accompanied by fatigue and malaise, headache, chills, and myalgias. Nausea, vomiting, reduced appetite and depression can also occur. Some patients will develop enlarged livers or spleens. The usual disease course lasts weeks to several months, but some patients take even longer to fully recover.
Like all of the Lyme Coinfections, diagnosis is pretty straightforward. If babesiosis is suspected, microscopic examination of blood smears are used. In early illness, the infection rate of red blood cells can be less than 1%, so multiple smears over a period of days may be needed to confirm the diagnosis. Babesial DNA can also be detected by polymerase chain reaction (PCR) in cases where smears are negative but the diagnosis is still suspected.
Immunofluorescence (IFA) of IgM and IgG antibodies is sometimes used to confirm a babesiosis diagnosis. However, antibodies to Babesia organisms can remain in the blood for months or years after the illness, so the test does not tell whether the infection is active. This does not stop "LLDs" from treating babesiosis anyway. One should always be suspicious of co-infections diagnosed from banding. There is very little specificity, meaning the banding can't tell us much. Treating non-active infections does no good.