Beaver Fever: Whole-Genome Characterization of Waterborne Outbreak and Sporadic Isolates To Study the Zoonotic Transmission of Giardiasis

Abstract

Giardia duodenalis causes large numbers of gastrointestinal illness in humans. Its transmission through the contaminated surface water/wildlife intersect is significant, and the water-dwelling rodents beavers have been implicated as one important reservoir. To trace human infections to their source, we used genome techniques to characterize genetic relationships among 89 Giardia isolates from surface water, humans, and animals. Our study showed the presence of two previously described genetic assemblages, A and B, with mixed infections detected from isolates collected during outbreaks. Study findings also showed that while assemblage A could be divided into A1 and A2, A1 showed little genetic variation among animal and human hosts in isolates collected from across the globe. Assemblage B, the most common type found in the study surface water samples, was shown to be highly variable. Our study demonstrates that the beaver is a possible source of human infections from contaminated surface water, while acknowledging that theirs is only one role in the complex cycle of zoonotic spread. Mixes of parasite groups have been detected in waterborne outbreaks. More information on Giardia diversity and its evolution using genomics will further the understanding of the epidemiology of spread of this disease-causing protozoan.

Occurrence and multilocus genotyping of Giardia duodenalis in captive non-human primates from 12 zoos in China

“…Compared with other countries, the average infection rate in this study was closed to that in Thailand (7.0%, 14/200) [9] and Uganda (11.1%, 9/81) [10], but lower than that in North-West India (31.2%, 53/170) [11]. The differences of infection rates in NHPs may be related to animal health status, detection methods, or geo-ecological conditions [2,8,15,16,[22][23][24][25][26][27][28][29]. Nested PCR protocols based on single-copy genes (bg, tpi and gdh) had considerable lower diagnostic sensitivities than those based on multiple-copy genes (e.g.…”

“…Giardia duodenalis is an intestinal parasite that causes giardiasis in humans and animals. Giardia duodenalis infection may be asymptomatic or elicit several clinical symptoms including diarrhea, vomiting, weight loss, abdominal cramps, and nutrient malabsorption [1,2]. Giardia duodenalis commonly infects non-human primates (NHPs), and causes both veterinary and public health problems [3][4][5][6][7].…”

Hidden Diversity within Common Protozoan Parasites as Revealed by a Novel Genomotyping Scheme

“…Whole-genome sequencing reads from 34 isolates of Giardia duodenalis assemblage B were downloaded from the SRA database at NCBI. These genomes were originally derived from several hosts (human, beavers, and one dog) plus environmental samples and were collected between 1989 and 1995 in British Columbia, Canada, as part of either contemporary waterborne outbreak investigations or monitoring (48,49). Additionally, contigs from three reference assemblies (isolates BAH15c1 from Australia and GS and GSMH7 from Alaska) and respective annotations were downloaded from the Assembly database at NCBI, for a total of 37 genomes in our final data set.…”

Risk factors for sporadic giardiasis: a systematic review and meta-analysis

“…Molecular characterization with more discriminatory tools, as whole-genome sequencing (WGS), may also help to establish patterns of transmission in cases from outbreaks (Tsui et al,2018); and sporadic cases of giardiasis (Tsui et al,2018;Thompson and Ash, 2019) Farm environments and exposure to farm animals are mostly mentioned with no adjusted OR or not adjusted with other known potential risk factors. Therefore, the significance of these factors could result from correlation with other factors such as unsanitary toilets, insufficient/low treatment of drinking water, or unsafe sewage systems.…”