Babesia microti in Texas: Raccoons Suggest the Parasite Is Spreading
Babesia microti, the parasite responsible for most human babesiosis cases in the United States, may be expanding beyond its traditional northeastern range. A new study detected Babesia microti in raccoons in East Texas, raising questions about emerging human risk in the South.
Is Babesia microti Spreading to Texas?
Previous studies in Florida identified two distinct groups of this tick-borne parasite depending on the host species — cotton rats versus raccoons.
Investigators in the current study looked for the presence of Babesia species in small and medium-sized mammals in East Texas. A total of 480 wild mammals were trapped, sampled, and screened using molecular analysis.
Babesia microti Found in Texas Raccoons
According to Modarelli, “Babesia microti was found only in raccoons within the areas sampled.” Five out of 15 raccoons (33%) tested positive for Babesia microti.
The Babesia microti strains identified in East Texas resembled strains previously found in raccoons in the northeastern United States and in Florida based on DNA sequence analysis.
Although the Centers for Disease Control and Prevention reported three cases of Babesia in Texas between 2011 and 2015, the authors found no confirmed human cases in Florida or Texas at the time of the study.
First Babesia microti Study in Texas
“To our knowledge, this is the first study of its kind in Texas and it can provide baseline data for future research and surveillance studies on this group of parasites,” Modarelli writes.
“Public health agencies should still monitor for the risk of human babesiosis in this area,” the authors warn, “due to the established presence of the competent tick vector Ixodes scapularis (deer ticks).”
Why Babesia microti in Texas Matters for Patients
The presence of Babesia microti in Texas wildlife suggests the parasite’s geographic range may be expanding. Human babesiosis cases remain uncommon in the South, but the detection of infected wildlife indicates the parasite could be establishing itself in new regions.
Surveillance of animal reservoirs such as raccoons can provide an early warning before human cases begin to appear.
Patients and clinicians in the South should remain aware that tick-borne co-infections — including Babesia — are not limited to the northeastern United States.
Babesia Symptoms in Humans
Babesia microti infection can cause a range of symptoms in humans. Common symptoms of babesiosis include fever, chills, fatigue, sweats, headache, and muscle aches.
In some patients — particularly older adults or those with weakened immune systems — infection can lead to more severe illness including anemia, shortness of breath, and complications affecting the liver or kidneys.
Because Babesia microti is transmitted by the same tick species that spreads Lyme disease, patients may develop tick-borne co-infections that complicate diagnosis and treatment.
References
- Modarelli JJ, Westrich BJ, Milholland M, et al. Prevalence of protozoan parasites in small and medium mammals in Texas, USA. Int J Parasitol Parasites Wildl. 2020;11:229-234.
- Babesiosis Surveillance — United States, 2011–2015. Morbidity and Mortality Weekly Report (MMWR). CDC.
Related Reading
- Babesia and Lyme: What Patients Need to Know
- Babesia Risk: Citizen Scientists Uncover Growing Threat
- Don’t Let Your Guard Down on Questing Ticks in the South
Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.
Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention
