Babesiosis - A Parasitic Infection That Accompanies Lyme Disease
An Overview Of The Disease Babesiosis
This is another not so common disease transmitted by Ixodid ticks. Babesiosis is primarily a zoonosis infecting wild and domestic animals worldwide.
Humans are infected incidentally and initially develop a non-specific illness associated with fever.
Babesia organisms infect red blood cells and resemble malarial parasite, thus posing a diagnostic problem.
Microscopic Appearance of Babesia Bacteria
Characteristics Of The Organism - Babesia
The two most common species of this protozoal parasite that infect humans include -
- Babesia divergens (common in Europe).
- Babesia microti (common in North America)
Ixodid (or hard-bodied) ticks, in particular Ixodes dammini (Ixodes scapularis) and Ixodes ricinus, are the carriers of this parasite.
Ticks ingest babesia organisms while feeding, and the parasite lodges and multiplies in the wall of their digestive tract, from where the organisms spread to their salivary glands; when the tick feeds on a vertebrate host, it inoculates babesia organisms into the host blood thus completing the cycle of transmission.
Within the host red blood cells, babesiae undergo binary fission (asexual reproduction) producing two and then four daughter parasites, causing red cell rupture, followed by infection of other cells.
Geographical Distribution Of Babesiosis
Almost all Babesia microti infections in the U.S. occur along the north eastern coast, including Nantucket Island and Martha's Vineyard in Massachusetts, Long Island and Shelter Island in New York, and the nearby mainland, including Connecticut, as well as Wisconsin.
A new Babesia species (WA.1) that is genetically and antigenically different from Babesia microti, has been isolated from individuals in California (3-20% in rural areas), Washington and Georgia.
Vector Transmitting Babesiosis
Other Lesser Known Facts About Babesiosis
Transfusions are another source for transmitting this infection. In these cases, no parasite can be detected in the blood of donors, but serological testing of their blood for Babesia gives positive results.
Infection with Babesia divergens is more common in persons with their spleen removed due to various reasons. This disease is otherwise a zoonosis common in cattle, but the asplenic state predisposes humans to this infection that is commonly transmitted by Ixodes ricinus.
Hard ticks feed on rodents during their larval and nymphal stages, and on deer in adult stage; thus the mouse and deer are the major natural reservoirs of this infection. The nymphs are abundant in spring and summer and readily feed on humans, thus spreading the infection.
With extension of the deer's habitat, the range of human infection is also increasing.
Things to Remember about Babesiosis
- Babesiosis is a protozoal parasitic infection common in wild and domestic animals world wide.
- Humans accidentally acquire the infection due to tick bits or blood transfusions from infected individuals.
- The disease manifests as fever, chills, sweating, fatigue, and mild anemia. It is usually self-limited with complete recovery even without treatment.
- People with their spleen removed are at risk of a more severe illness associated with complications.
- Preventive measures include avoidance of tick bites by wearing fully covered clothes when on a trip into the woods, application of repellents, and minimizing contact with overgrown grass.
Signs and Symptoms of Babesiosis
Most of the sufferers will not even recall a tick bite. After an incubation period of 1 to 4 weeks (when the infection is present in blood and is gradually gaining strength), there is a gradual onset of fever, chills, sweating, muscle pain, and fatigue. Liver and spleen are enlarged, and there is associated mild anemia.
Although the parasite may remain in blood for months with or without causing symptoms, the disease is self-limited, and after several weeks or months, most people recover without sequelae.
This disease runs a more aggressive course in immuno suppressed individuals, those with their spleens removed and, the elderly.
Babesia divergens causes a more severe illness, with rapid onset of chills, fever, nausea, vomiting and hemolytic anemia, progressing to jaundice and kidney failure.
Table Summarizing Manifestations, Diagnosis, and Prevention of Babesiosis
Signs and symptoms
Fever with chills
Geimsa stained peripheral blood film
Light colored covered clothing
Indirect Immunoflorescencce antibody test
Walking on clear trails
Polymerase Chain Reaction
Use of repellents
Diagnosis of Babesiosis
Whether or not there is a history of exposure to ticks, all persons with fever and living in endemic areas should have a Geimsa stained Peripheral Blood Film (both thick and thin) examined for these microscopic parasites that reside in our red cells.
Babesia microti appears as small ring forms in red blood cells, resembling the malarial parasite Plasmodium falciparum (the difference being, Babesia does not cause pigment formation in the parasites, nor are schizonts and gametocytes formed, that are characteristic of the malarial parasite).
The parasite divides in the host RBCs, and each Babesia organism gives rise to four parasites attached by strands of cytoplasm (called "tetrads"). These "tetrad" forms, though rarely seen, are a distinguishing feature of this infection.
Indirect Immunoflorescence Antibody Test is another diagnostic test for this infection. The serum antibody titre rises 2 to 4 weeks after the onset of the illness and then wanes over 6 to 12 months.
About half of the patients infected with Babesia microti have antibodies to Borrelia burgdorferi, the agent causing Lyme disease, as mixed infections are common, both organisms being transmitted by Ixodes dammini.
Intraperitoneal inoculation of the patient's blood into gerbels and hamsters can also help in isolating this parasite.
Polymerase Chain Reaction (PCR) method, where available, is more sensitive for low parasitemia.
Treatment of Babesiosis
Infections are self limited in individuals with an intact spleen. The normal conventional treatment consists of -
- For adults, Quinine sulphate (in a dose of 650 mg orally thrice a day) along with antibiotic Clindamycin (in a dose of 600 mg orally thrice a day; or 1.2 gm parenterally, that is a direct injection into the vein, twice a day) for 7-10 days is effective, but does not eliminate the parasite completely from the blood.
- For children the doses are, 20 to 40 mg/kg/day of Quinine sulphate and 25 mg/kg/day of Clindamycin, given thrice a day by mouth for 7-10 days.
If this conventional regime fails, then Atovaquine suspension (750 mg twice daily) with antibiotic Azithromycin (500-1000 mg/day) may be given.
For asplenic individuals with a more severe infection, exchange transfusions are necessary along with the medicines.
How to Prevent Babesiosis ?
Since no vaccine is available against the infection, you need to to take precautions during outdoor activities in tick habitats to keep the vectors off your skin. The preventive measures include the following :
- Walk on clear trails, and stay in the center of the trail to minimize contact with leaf litter and overgrown grass where ticks are most likely to feed.
- Wear socks, long pants, and a long sleeved shirt. Tuck the pant legs into your socks when going into the woods, so that the ticks cannot get within your clothes. Wear light colored clothes to make it easier to see and remove the ticks before they attach to the skin.
- Apply repellents to your skin and clothes. Permethrin products can be applied to clothes or boots (not on the skin).
- After outdoor activities conduct a full body exam and promptly remove the ticks that are found. For this you can use a hand held or a full body mirror to view all parts of the body. Be sure to check behind the knees, between the toes, under the arms, and waist, back of the neck and, behind and in the ears.
- Remove Ixodes vectors from your clothes and pets before going indoors.
Babesiosis- a zoonosis that incidentally infects us
Since we cannot totally avoid animal exposure, be that as domestic pets, dairy animals or wildlife, or for that matter visiting a zoo or an animal sanctuary, we are always at risk of contracting certain infections that are otherwise common in animals.
Babesiosis is one such parasitic infection that is transmitted by hard ticks, with deer being its natural host. It causes a mild, self limiting illness in otherwise normal individuals, but can lead to jaundice and kidney failure in people with their spleen removed.
Both Lyme disease and Babesiosis being transmitted by hard ticks, can cause mixed infections in the same individual, in which case multiple infections exhaust our body immunity and can lead to permanent damage.
The infection can usually be contained by antiparasitic medications and antibiotics used in various combinations.