Babesiosis is a disease caused by the parasite Babesia. This illness is most commonly transmitted to humans by getting bitten by Babesia-infected ticks - such ticks being most commonly found in the United States of America, Europe and Asia. Babesiosis typically leads to flu-like symptoms, however in specific populations of people, such as the elderly or those who have a weak immune system, the illness can lead to severe, and even life-threatening, health complications.¹ 

Babesiosis is now considered an emerging infectious disease, which means that the number of cases of this disease has increased in recent years and they are projected to continue to rise. Due to this, it is important to know its symptoms and its complications.¹

This article will therefore aim to raise awareness of babesiosis and its associated health complications, as well as how to diagnose and treat the disease. 

What causes babesiosis?

As mentioned above, babesiosis is caused by the parasite Babesia. This parasite gets into our blood most commonly via the bite of a tick - a small, insect-like animal which attaches itself to the skin of other animals and humans and sucks blood, in turn transmitting the parasite into our blood. The parasite can then travel around our body in our blood, replicating itself and leading to babesiosis symptoms.²

The specific species of ticks associated with babesiosis is the Ixodes scapularis tick, also known as the black-legged or deer tick. Most people become infected from these tick bites during outdoor activities in areas where babesiosis is known to spread. It is most common for people to develop babesiosis during the spring and the summer. Not only are these the seasons where people partake in outdoor activities the most, but also young ticks (known as nymphs) come out in the spring, and these are more likely to infect a human with Babesia compared to adult ticks, as they are smaller and more difficult to spot on the skin. The Ixodes scapularis nymphs must stay attached to a human for roughly 36-48 hours in order to transmit the Babesia parasite.²

Other less common ways in which humans can become infected with Babesia include:

• Blood transfusion - One can get babesiosis if they receive Babesia-infected blood. This occurs when a blood donor is not aware that they are infected with the parasite³ 
• Organ transplantation - In a similar manner to blood transfusions, one can get babesiosis if they receive an infected organ from a donor who was not aware of having such an illness² 
• During pregnancy - Babesiosis is not contagious from person-to-person. However, very rarely, the only time this illness could be passed on between humans is if a pregnant person is infected with Babesia and passes the parasite to their foetus via the placenta⁴ 

Typical symptoms of babesiosis

Most people with babesiosis either do not feel sick, or experience non-specific flu-like symptoms. Such symptoms usually appear in the following weeks (1-4) after becoming infected with the parasite. 

Common symptoms include: 

• Fever;
• Fatigue
• Headaches
• Muscle and joint aches
• Coughing
• Sweating
• Nausea
• Chills
• Loss of appetite 

Unlike other diseases spread by ticks, babesiosis does not usually cause rashes on the skin - this is one way to distinguish this illness from other tick-borne diseases.

Specific populations that are more affected by babesiosis

While anyone can become infected with babesiosis, there are certain populations of people who are more prone to suffering from more serious complications alongside the flu-like symptoms. 

These specific populations include:

• Immunocompromised patients - These are patients who have a weakened immune system (which is our bodily system that helps fight infections and diseases). This can happen from taking certain medications or if a patient suffers from a disease which weakens the immune system (such as HIV, cancer, autoimmune disorders, and chronic illnesses such as heart, renal and liver disease)
• Asplenia patients - These are patients who do not have a spleen, or whose spleen does not work properly
• Elderly patients - People who are older than 60⁵ 

Severe complications of babesiosis

The following are examples of the most common severe complications that occur in babesiosis patients. 

Haemolytic anaemia

Babesiosis can lead to a disorder known as haemolytic anaemia, which is when red blood cells are destroyed quicker than your body can replace them with new cells, resulting in a decrease in healthy red blood cells circulating within the body. The Babesia parasites are responsible for attacking and destroying these red blood cells. Haemolytic anaemia can lead to jaundice (the yellowing of the skin and the eyes) and the darkening of the urine. Severe haemolytic anaemia can result in serious heart conditions, including arrhythmia and cardiomyopathy, as well as heart failure.⁶ 

Thrombocytopenia

Babesiosis can also result in thrombocytopenia, which is the condition where a patient has very low levels of platelets in their blood. Platelets are small fragments of cells which have the important role of forming blood clots, which are gel-like masses that prevent bleeding from occurring. Like with red blood cells, Babesia parasites attack platelets, leading to patients having significantly low levels of platelets in their blood. Severe thrombocytopenia increases the risk of excessive bleeding, bruising, and suffering from a heart attack.⁷

Splenomegaly

The spleen plays an important role in our body - it controls the amount of different types of blood cells within our blood, and it removes old and damaged cells from the blood. As the Babesia parasite destroys both red blood cells and platelets, in severe babesiosis patients, the spleen becomes ‘overworked’ in trying to remove all these damaged cells from our body. Such ‘overworking’ of the organ can result in its enlargement - this is known as splenomegaly. 

An enlarged spleen can lead to a variety of issues:

• The spleen cannot function properly, resulting in the patient becoming more prone to infections within the blood
• Increased, uncontrollable bleeding
• Can be very painful
• The spleen itself could rupture, which can result in life-threatening internal bleeding⁸

Disseminated intravascular coagulation

As babesiosis affects platelets, the illness can also lead to a serious condition called disseminated intravascular coagulation (DIC). In DIC patients, their blood does not clot normally. 

There are 2 stages of DIC:

1. In the first stage, blood clots randomly form around a patient’s body, blocking their blood vessels and cutting off blood supply to important organs. If continuous, this can result in major organ damage
2. In the second stage, due to all the platelets having been used up during the first stage of DIC, instead patients experience excessive bleeding, both internally and externally (such as out of the mouth or the nose), which if left uncontrolled can be life-threatening⁹ 

Acute respiratory distress syndrome

Babesiosis can also lead to acute respiratory distress syndrome (ARDS), which is the condition where fluid ends up in the lungs and leads to their swelling. This fluid in the lungs takes up precious space within the lungs, in turn meaning less air and less oxygen can be breathed in. If severe, this could result in lung damage and failure of other organs, due to them not receiving enough oxygen to continue to work properly.¹⁰

Hepatomegaly

Severe babesiosis can lead to swelling of the liver - also known as hepatomegaly. This enlargement of the organ can lead to jaundice. If persistent, hepatomegaly can also affect the many important functions of the liver, including the removal of waste products from the blood, the storage of energy, and the breakdown of chemicals from food for the body to then use.¹¹ 

Neurological complications

Alongside the common babesiosis symptoms of headaches and muscle and joint aches, severe babesiosis in specific patient populations can result in further neurological complications. This includes the following:

• Delirium
• Impaired consciousness
• Ataxia - This is when a patient has poor control of their muscles, which can lead to clumsy movements
• Impaired vision¹² 

Diagnosis of babesiosis

The first step in diagnosing babesiosis is the patient under going a physical exam of their symptoms as well as a medical history exam. The medical history exam evaluates whether the patient is part of the specific populations that are more susceptible to developing severe babesiosis. This medical history exam also assesses whether a patient has had a blood transfusion or undergone an organ transplantation within the past 6 months. Also, patients will be asked whether within the past month they visited any area where they could have been bitten by a tick. 

If the doctor suspects babesiosis after such initial assessments, then blood smears will be done to diagnose babesiosis, in order to detect the Babesia parasite within the blood sample. Such tests can also indicate whether a patient is suffering from a severe complication from babesiosis, such as hemolytic anaemia, DIC and thrombocytopenia (as the blood tests will show low levels of red blood cells and platelets respectively).¹³ 

Treatments for babesiosis

Babesiosis is typically treated with a combination of medications used to destroy the Babesia parasite in the blood. Common examples of medications used include:

• Atovaquone
• Azithromycin
• Clindamycin
• Quinine¹³

Patients who are suffering from severe consequences of babesiosis can be admitted to hospital and given additional treatment to alleviate their symptoms. For example: 

• Blood transfusions - If patients have a low red blood cell and platelet count within their infected blood (such as in haemolytic anaemia, thrombocytopenia and DIC patients), they can receive blood transfusions from a healthy donor to increase the number of these blood components
• Exchange transfusions - This treatment involves removing a patient’s infected blood and replacing it with healthy donor blood
• Mechanical ventilation - For patients suffering from ARDS, who cannot breathe very well by themselves, a ventilator can be used to help them breathe
• Further medications - Additional medications can be used to treat some of the complications, including vision impairment, hepatomegaly, and ataxia
• Low-dose radiation therapy - Splenomegaly can be treated using low-dose radiation therapy to reduce symptoms of pain
• Surgery - If the swelling of the spleen is too severe, or if an organ is too damaged, organ transplantation can be done in babesiosis patients¹³ 

Prognosis of babesiosis

For those who do not have with severe babesiosis, the illness typically lasts 1-2 weeks. In those with severe babesiosis and associated complications, the disease can last a long time - months or even years, depending on the severity of the complications. However, most patients do recover from babesiosis. 

Patients who belong to the specific populations mentioned above are more prone to babesiosis relapse (the condition coming back shortly after having recovered).¹³ 

Summary

Babesiosis is an illness caused by the parasite Babesia, most commonly spread to humans via the bite of infected black-legged or deer ticks. In most patients, the condition results in flu-like symptoms, which can be easily treated with medication. However, in specific populations, such as those with weakened immune systems, those with asplenia and those who are over the age of 60, babesiosis can lead to significant complications. These include the destruction of red blood cells and platelets, which can lead to severe consequences of organ failure and uncontrollable bleeding. Other babesiosis complications include fluid build-up in the lungs, which hinders breathing. The spleen and the liver can also become enlarged in such patients, and these swellings can have detrimental impacts on the functions of these important organs. Additionally, severe babesiosis can result in neurological complications such as impaired consciousness and vision, as well as clumsy movements and confusion. In such patients, additional treatments can be used to relieve these symptoms - this includes blood transfusions, mechanical ventilation, low-dose radiation therapy and even surgery in very severe cases. These treatments will help these patients recover from babesiosis.