What are the symptoms of babesiosis?

Symptoms range from mild to severe, and differ depending on whether the infection is recent — known as an acute infection — or long-standing, known as a chronic infection. A person may also carry the parasite without showing any signs, or the first symptoms may not appear until months or even years later [1].

Babesia infects red blood cells and destroys them. This destruction, combined with an excessive inflammatory response, explains most of the symptoms [1]. In chronic forms, small blood vessels can also become blocked by clumps of infected red blood cells, depriving tissues of oxygen [11-12].

I - Acute infection:

Symptoms appear one to six weeks after transmission and are not specific: intermittent fevers, fatigue, malaise, sweats (often at night), headaches, chills and muscle pain. Nausea, vomiting, loss of appetite and depression are also possible [1].

The infection lasts from a few weeks to several months. People with good immune defenses often recover completely. In others, fever can exceed 40.5 °C, with destruction of red blood cells, jaundice, dark urine, a drop in blood pressure and anemia [1].

II - Chronic infection:

Sometimes, some people develop a chronic infection after an asymptomatic or acute phase. Symptoms then become very diverse: nervous system disorders, liver abnormalities, heart and psychiatric disorders [11-12-13-14-15].

Some are specific to babesiosis; others are also found in co-infections such as bartonellosis or Lyme borreliosis [17-18].

Symptoms specific to babesiosis

• Night sweats

• Feeling short of air, shortness of breath

• Heart or chest pain

• Stabbing sensations

• Exhaustion and yawning on exertion

• Jaundice, dark urine

• Anemia

Symptoms shared with other infections

• General signs — fatigue, weakness, sleep disorders, mild fever (37.5-38 °C), chills

• Memory and concentration — cognitive disorders, “brain fog”

• Mood — depression, anxiety

• Pain — headaches, muscle and joint pain

• Heart — heart problems, chest pain

• Vision — visual disturbances

• Digestion and bladder — nausea, constipation, diarrhea, gastritis, irritable bowel syndrome, irritable bladder

Sources: [11-12-13-14-15-16]

It is possible to have only some of the symptoms.

Step I - Symptom assessment

The diagnosis of babesiosis relies primarily on clinical examination: symptoms, medical history and physical examination [19-20]. A thorough medical consultation with a specialist is therefore essential.

The symptoms resemble those of many other diseases. Being non-specific, they often lead to misdiagnoses — depression, anxiety, psychosis, chronic fatigue syndrome [21-22].

Many symptoms are shared with Lyme borreliosis and bartonellosis [17-18]. It is not uncommon for some people to have several infections at once [3-5-7-8].

The questionnaire by Dr. Horowitz, a specialist in borreliosis and co-infections, helps assess the likelihood of an infection.

Step II - Microbiological testing

It is important to know that no blood test is yet fully reliable. Tests serve to support the clinical diagnosis, never to replace it [19-20].

1. The official tests:

In Switzerland, three tests are used:

• The blood smear looks for the parasite under the microscope [1]. Effective in the acute phase, it is very limited in chronic forms [3].

• The PCR test looks for the parasite's DNA [1]. However, Babesia hides inside red blood cells, which makes it difficult to detect [3].

• The IFA test measures antibodies and does not show whether the infection is active [1]. It has low sensitivity, only exists for B. microti, and misses the other species present in Switzerland.

2. Other possible tests:

There are newer, much more sensitive tests that can detect more Babesia species — notably FISH and cePCR [3-23]. They are useful when the smear, PCR or IFA come back negative.

They are not recognized for diagnosis in Switzerland: they are performed in laboratories in Belgium, Germany and the USA.

There are no large-scale studies on these tests yet, but they are widely used by physicians who are members of ILADS.