Introduction:
Human fascioliasis is a zoonotic infection caused by the adult stage of the Fasciola species. Fasciola hepatica is a parasite that, following living in its vertebrate host, may reduce the host›s inflammatory immune responses to infectious diseases, including COVID-19. Therefore, because of the completely unproven and limited data on this issue, the study evaluates the prevalence of antibodies against this parasite in patients admitted to hospital due to relatively severe symptoms of COVID-19.

Material and methods:
During the first wave of coronavirus-19, investigations were carried out on the serum samples of 182 patients hospitalized with COVID-19, diagnosed by PCR test, and on 210 healthy subjects in Alborz province, Iran,between March – June 2020. The status of anti-Fasciola antibodies was determined in all serum samples by using the ELISA technique. A self-developed questionnaire was used to measure demographic information.

Results:
The frequency of Fasciola infection was found to be lesser in the COVID-19 patients than in the healthy control (n = 4, 2.2%, n = 9, 4.3%, respectively; p = 0.041). There was no significant difference between COVID-19 patients and the control group in the variables of age, education (p > 0.05).

Conclusions:
The study indicates that a significant association exists between Fasciola hepatica seroprevalence and the studied COVID-19 patients and healthy individuals. The results also suggest that fascioliasis may be able to lead to decreased immune responses, thereby reducing the severity and symptoms of COVID-19 disease.