Researchers have reported the first laboratory-confirmed case of Trypanosoma evansi infection in a Vietnamese woman with no deficiencies. They linked transmission of the parasite with bovid exposure.
"Over half of Vietnam's population resides in rural areas, and most participate in small-scale animal production, which likely facilitates the transfer of pathogens from animals into humans," the researchers wrote. "T. evansi is associated with acute disease in camels and horses and chronic disease in cattle and buffalo, and can be found in South America, North Africa, the Middle East, South and Southeast Asia."
There have been four probable cases of T. evansi infection reported worldwide that lacked molecular parasite speciation. One previous case was reported in India in 2005 with molecular confirmation, although the patient had a deficiency of Apolipoprotein L1 (APOL1), a serum component with trypanocidal activity.
The present case, a previously healthy Vietnamese woman aged 38 years with no APOL1 deficiency, first presented to a health care facility with 18 days of fever, headache and arthralgia. She had no history of travel to any regions where T. evansi has been observed. Although initially treated for malaria, microscopic examination of blood samples revealed unicellular flagellate protozoa with the morphology of Trypanosoma. The patient received a treatment reported to have trypanocidal activity for 7 days, but returned with symptoms 6 weeks after discharge and subsequently treated with a first-line anti-trypanosomal treatment and eventually recovered with no complications.
PCR amplification and serological testing of the patient's serum confirmed the infecting species as T. evansi, and APOL1 testing found the patient's concentrations to be within a healthy range. As the patient reported potential exposure while butchering locally reared beef, the researchers conducted a census of livestock farms surrounding the patient's relatives' household. Blood samples from some cattle and buffalo were indicative of T. evansi infection, and some farmers reported a mystery illness affecting their livestock.
With these data, the researchers concluded that these bovid were the likely source of the patient's infection. Furthermore, the parasite may have been circulating among Vietnamese livestock for some time while avoiding detection, and if endemic could have further economic and human health consequences for the region.
"Subsequent field investigations demonstrated a high prevalence of bovids in the immediate environs of the patient with clinical and molecular evidence of T. evansi infection," the researchers wrote. "Further research is required to better understand this zoonotic pathogen, including host susceptibility factors, potential vectors and therapeutic options for both human and animal infections." – by Dave Muoio
Disclosure: The researchers report no relevant financial disclosures.