Unveiling the presence and genotypic diversity of Giardia duodenalis on large-scale sheep farms: insights from the Henan and Ningxia Regions, China

Background: The parasitic protozoan Giardia duodenalis is an important cause of diarrheal disease in humans and animals that can be spread by fecal-oral transmission through water and the environment, posing a challenge to public health and animal husbandry. Little is known about its impact on large-scale sheep farms in China. In this study we investigated G. duodenalis infection of sheep and contamination of the environment in large-scale sheep farms in two regions of China, Henan and Ningxia.

Methods: A total of 528 fecal samples, 402 environmental samples and 30 water samples were collected from seven large-scale sheep farms, and 88 fecal samples and 13 environmental samples were collected from 12 backyard farms. The presence of G. duodenalis was detected by targeting the β-giardin (bg) gene, and the assemblage and multilocus genotype of G. duodenalis were investigated by analyzing three genes: bg, glutamate dehydrogenase (gdh) and triphosphate isomerase (tpi).

Results: The overall G. duodenalis detection rate was 7.8%, 1.4% and 23.3% in fecal, environmental and water samples, respectively. On the large-scale sheep farms tested, the infection rate of sheep in Henan (13.8%) was found to be significantly higher than that of sheep in Ningxia (4.2%) (P < 0.05). However, the difference between the rates of environmental pollution in Henan (1.9%) and Ningxia (1.0%) was not significant (P > 0.05). Investigations of sheep at different physiological stages revealed that late pregnancy ewes showed the lowest infection rate (1.7%) and that young lambs exhibited the highest (18.8%). Genetic analysis identified G. duodenalis belonging to two assemblages, A and E, with assemblage E being dominant. A total of 27 multilocus genotypes were identified for members of assemblage E.

Conclusions: The results suggest that G. duodenalis is prevalent on large-scale sheep farms in Henan and Ningxia, China, and that there is a risk of environmental contamination. This study is the first comprehensive examination of the presence of G. duodenalis on large-scale sheep farms in China. Challenges posed by G. duodenalis to sheep farms need to be addressed proactively to ensure public health safety.