The Toxoplasma gondii prevalence and its impact on tick-borne encephalitis virus infection among humans in Heilongjiang province of China.

Toxoplasmosis and tick-borne encephalitis (TBE) are endemic in Heilongjiang province, China, posing a significant threat to public health. Although some research has indicated that Toxoplasma gondii infection may suppress the host’s immune response and increase susceptibility to other pathogens, no studies have been conducted to explore the association between these two diseases. From 2020 to 2023, a total of 415 serum samples were collected and tested for both T. gondii and tick-borne encephalitis virus (TBEV) infections using enzyme-linked immunosorbent assay (ELISA) by us. The positive rates of T. gondii and tick-borne encephalitis virus were 14.15% (60/415) and 36.14% (150/415), respectively. The positive rate of tick-borne encephalitis virus was 66.67% (40/60) in T. gondii-positive patients, while it was 30.99% (110/355) in the group of T. gondii-negative patients. A statistically significant correlation was observed between T. gondii infection and the tick-borne encephalitis virus (TBEV) positive status (P < 0.05). Age and occupation were significantly associated with seropositivity of T. gondii (P < 0.05). This finding provides the first indication that individuals infected with T. gondii are more susceptible to tick-borne encephalitis virus (TBEV).