Fish as a possible reservoir for zoonotic Giardia duodenalis assemblages

Giardiasis is a re-emerging infectious disease of worldwide significance caused by Giardia duodenalis. This study investigated the occurrence of zoonotic G. duodenalis assemblages in fish to explore the possible role of fish in the epidemiology of human giardiasis. For this purpose, 92 fish (Tilapia nilotica and Mugil cephalus) collected from (fish farms and Nile River) at different governorates in Egypt were examined for the presence of G. duodenalis in their feces by using enzyme linked immunosorbent assay, then positive fecal samples were tested by duplex PCR for identification of triose phosphate isomerase (tpi) gene specific for zoonotic assemblages A and B. The overall prevalence of G. duodenalis in the examined fish was 3.3%, while the detection rates among the examined fish species were 2.9% and 4.2% for T. nilotica and M. cephalus, respectively. G. duodenalis was detected in the feces of both farmed and wild fish whereas all isolates were genotyped as assemblage A. In conclusion, the occurrence of zoonotic G. duodenalis assemblage A in the examined fish species at two different aquatic environments underlines the possibility of fish to be an additional reservoir for zoonotic G. duodenalis assemblages that contributes in the contamination of water with this pathogen and thus the role of fish in the epidemiology of human giardiasis cannot be ruled out.