What is a Maltese Cross on a Babesia Blood Smear?

If your lab report mentions a “Maltese cross,” it means the laboratory technician or pathologist saw a highly specific shape made by the Babesia parasite inside one of your red blood cells ^[1]. Biologically, this happens when a single Babesia parasite multiplies and forms four separate parasites that arrange themselves in the shape of a cross ^[2].

Because this four-part shape (sometimes called a tetrad) is unique to Babesia, seeing it serves as definitive proof that you have babesiosis ^[3][4].

Why the Maltese Cross is a Helpful, But Rare, Finding

While the Maltese cross confirms a babesiosis infection, it is actually quite rare to find on a standard blood smear ^[2]. Babesia parasites are tiny, and they reproduce inside your red blood cells ^[5]. Because only a small percentage of your red blood cells might be infected at any given time, catching four parasites perfectly aligned in this specific cross shape is uncommon ^[2].

Importantly, because this shape is so rare, many people who are genuinely infected with babesiosis will not have a Maltese cross mentioned on their lab report. An absence of this finding does not mean you do not have the disease ^[2].

When doctors do see this shape, it is incredibly helpful. Symptoms of babesiosis can easily be confused with other infections, and under a microscope, Babesia often looks nearly identical to the parasite that causes malaria ^[4]. The Maltese cross is one of the few visual signs that immediately proves the infection is babesiosis and not malaria ^[3][4].

What This Means for Your Care

Because the Maltese cross confirms your diagnosis, your medical team can confidently move forward with a treatment plan specifically targeted at babesiosis ^[3]. They will not need to wonder if you have a different parasitic infection. Additionally, because babesiosis is transmitted by ticks, your doctor might also order blood work to check for co-infections, such as Lyme disease, before finalizing your medications ^[3].

Your doctor may still order additional blood work, such as a PCR (polymerase chain reaction) test ^[4]. While the blood smear proves you have Babesia, a PCR test detects the parasite’s DNA and can identify exactly which species of Babesia is causing your infection ^[4]. This helps ensure you receive the most effective medication for your specific illness.