New research on co-infections of Babesia odocoilei and Bartonella spp. highlight the challenges in diagnosis and the importance of improved diagnostics in tick-borne diseases.
Co-Infection Discovery
Dr. Ricardo Maggi and colleagues recently reported that infection with Babesia odocoilei was confirmed in seven people suffering chronic non-specific symptoms, of whom six were co-infected with one or more Bartonella species. The authors conclude that infection with B. odocoilei is more frequent than previously documented and can occur in association with co-infecting Bartonella spp. They published these findings in the journal Parasites and Vectors with the title of “Human Babesia odocoilei and Bartonella spp. co-infections in the Americas”.
Babesiosis and Bartonellosis: A Growing Concern
Human babesiosis, caused by a parasite called Babesia, is increasingly recognized worldwide. In North America, the main Babesia species affecting humans include B. microti, B. duncani, and B. divergens-like species. Recently, another species called B. odocoilei, typically found in deer and other animals, has been identified in human cases in the US and Canada.
Apart from Babesia, another bacterium called Bartonella henselae, the causative agent of cat scratch fever, is sometimes diagnosed in patients also suffering from babesiosis. Understanding the interplay between these diseases and how they spread is crucial for quickly and effectively diagnosing and treating patients, especially as new species and potential transmission routes are discovered.
Challenges in Diagnosis and Testing
Accurate clinical diagnosis of babesiosis, bartonellosis, and Lyme disease, the number one tick-borne illness globally, is complicated due to their overlapping and non-specific symptoms. Unfortunately, diagnostic testing used to confirm a clinician’s suspicion can sometimes return false positive results. This happens because antibodies, which are supposed to recognize specific pathogens, sometimes mistakenly recognize others. This can lead to misdiagnosis and delayed treatment.
The authors of the study highlight that molecular testing has made it easier to accurately detect and distinguish between different infections. However, there are still technical questions that the study didn't address. For example, the authors did not show DNA gel results to confirm they found the correct sizes for specific PCR fragments. It also would have been informative if results from both positive and negative controls were included, which would ensure specificity of the PCR fragments. Additionally, they didn't provide important details like the sequences of the PCR reagents and products they used. Other researchers have noted that DNA from Bartonella species can be very similar when amplified, so additional tests with different PCR primers are necessary to verify the findings.
The Importance of Collaboration and Improved Diagnostics
Moreover, the claim that B. duncani is transmitted by Ixodes pacificus ticks is not supported by the efforts of several other groups where attempts to passage the parasite in Ixodes ticks were unsuccessful. In contrast, B. microti can be routinely passaged in and recovered from Ixodes ticks. Such discrepancies are easily resolved through collaboration with other groups in the field by sharing patient’s blood samples, cultures, and sera to allow for independent examination of the blood smears and confirmation of PCR results using primer pairs for other genes.
Finally, it is worth noting that detecting DNA does not provide evidence of active infection. Ticks can acquire blood from various sources, but this does not mean they support the growth of the Babesia parasite. When a tick bites a mammal, it might transmit DNA from multiple pathogens it carries, but this doesn't mean it’s capable of establishing an active infection in a new host.
In Summary
In summary, this is why improved diagnostic tests that rely on biomarkers of active Babesia infection are desperately needed in the field. To fill this need and eliminate this critical resource gap, Global Lyme Alliance has taken a leadership position of funding research and development for improved diagnostics for babesiosis as well as other tick-borne diseases.
References
Human Babesia odocoilei and Bartonella spp. co-infections in the Americas - PubMed (nih.gov)
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