Babeisiosis, or infection with the protozoan Babesia, has been around for hundreds of years in wild and domestic animals such as cattle, horses, and sheep. But it wasn’t identified in humans until the 1960’s.
Babesia lives in many of the same animals as the Lyme disease bacteria, Borrelia. The same tick species that transmit Lyme can also pass Babesia to humans through a bite. Because of this similarity in hosts and transmission, babesiosis tends to occur in the same geographic areas as Lyme disease. Reservoir animals include deer, cattle, horses, dogs, cats, and mice. Of the over 100 Babesia species, only a few cause disease in humans, namely, Babesia microti, Babesia divergens, and to a lesser extent, Babesia bovis. B. microti is common in the United States. B. divergens occurs more often in Europe.
White-tailed deer and field mice are most responsible for supporting Babesia infections in humans. The deer host the Ixodes ticks in all its stages: larva, nymph, and adult. White-footed mice carry the protozoa. In other words, Ixodes ticks grow on deer and Babesia thrive in mice. When the two species intermingle, humans can be infected. Typically, an Ixodes tick nymph feeds on a field mouse infected with the protozoa. The infected nymph then bites a human. The longer an infected nymph feeds on a human, the more likely the protozoa are passed from the tick into the human bloodstream. Less common, blood transfusions can also transmit the protozoa.
Babesia has a particular fondness for red blood cells. Once inside a red blood cell, the protozoa split in half to form two new protozoa. This splitting continues until there are too many protozoa inside the cell. The cell then bursts and releases the micro-organisms into the blood. These free protozoa seek out new red blood cells to continue reproducing.
Having an infection that destroys red blood cells does a few particularly damaging things to the body:
- Babesia leaves the blood with too few red blood cells and therefore decreased oxygen., which red blood cells carry.
- A burst red blood cell also releases hemoglobin into the blood plasma. Too much hemoglobin floating around causes jaundice, or yellowing of the skin.
- Broken blood cell fragments can accumulate in the bloodstream faster than the spleen can eliminate them. When cell fragments travel through small blood vessels like capillaries, they can get stuck and block blood flow.
Symptoms of Babesiosis
An incubation period of one week to eight weeks elapses between the tick bite and the onset of Babesia symptoms. Almost everyone who contracts this disease gets flu-like symptoms of fever and chills.
Nonspecific symptoms include:
- generalized weakness
- intermittent fever
- fatigue, often with inability to sleep
- gastrointestinal (GI) symptoms like nausea, vomiting, diarrhea, and belly pain
- muscle pain
- joint pain
- unusual weight gain
- decreased appetite
- sensitivity to light, touch, sound, or smells
Specific symptoms of babesiosis (as consequences of ruptured red blood cells) include:
- shortness of breath – air hunger
- night sweats and hot flashes
- arm and leg pain
- swollen spleen
- dark urine (rare but can happen)
Anemia due to a low red blood cell (RBC) count is common in babesiosis. This can be easily detected with a routine blood test called a complete blood count or CBC. However, diagnosis cannot be made on this finding alone since many illnesses can cause anemia. Doctors must first suspect the diagnosis of babesiosis based on history and physical examination. A peripheral blood smear microscopic exam can reveal the microorganisms inside the red blood cell. If the blood smear does not show Babesia, but the physician strongly suspects babesiosis, more specific blood tests can be done. These tests search for proteins or DNA specific to the protozoa.
Note: Babesia’s substantial similarity to the malarial parasite Plasmodium falciparum results in misdiagnosis of many patients suffering from Babesiosis.
Since Babesia is a protozoan and not a true bacterium, it can’t be treated with run-of-the-mill antibiotics alone. Usually it’s treated with at least two drugs. The most commonly prescribed drugs are Mepron or Malarone (a combination of Atovaguone and Proguanil). That’s usually combined with some form of the herb artemesia (artemisiae or artemesinin) and/or the Ghanian root cryptolepis sanguinolenta. Another combination, oral Atovaquone (anti-protozoan drug) and oral Azithromycin (an antibiotic) have also been used successfully. A third combination, oral quinine (anti-malarial drug) and oral and intravenous Clindamycin (an antibiotic) have been used but aren’t well tolerated by some patients.
In extremely severe cases, an exchange blood transfusion may be required. In this treatment, the diseased blood is removed and replaced with healthy blood. Exchange transfusion is generally reserved for patients who have a large number of broken red blood cells, have lost the use of their spleen due to trauma or illness, and/or have parasites in greater than ten percent of their red blood cells.
Severe babesiosis is rare. However, a number of possible complications may arise from severe, untreated, or undertreated disease. While infrequent, the most common complications of babesiosis are:
- Acute respiratory distress syndrome – a severe lung disease with few effective treatments
- Severe anemia – Very low numbers of healthy red blood cells, requiring blood transfusion
- Congestive heart failure – Blood backs up in the lungs and veins when the heart can’t pump effectively
- Disseminated intravascular coagulation – The blood forms harmful clots some places in the circulatory system and does not clot in others
- Hypotension/shock – Severely low blood pressure
- Myocardial infarction – A heart attack
- Renal failure – Kidneys no longer filter the blood properly
Babesia tends to stick around for months. If patients have mild, nonspecific symptoms and don’t receive any Babesia treatment, the protozoa can be detected in the blood for about three months. Those treated with typical drug combinations will still carry Babesia for two to three weeks after treatment ends. Furthermore, evidence of the protozoa can persist in the blood for years, even though the person has no more symptoms.
For recommended articles and books on Babesia, see Babesia Resources.
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