Multilocus Genotyping of Human Giardia Isolates Suggests Limited Zoonotic Transmission and Association between Assemblage B and Flatulence in Children

Abstract

Background Giardia intestinalis is one of the most common diarrhea-related parasites in humans, where infection ranges from asymptomatic to acute or chronic disease. G. intestinalis consists of eight genetically distinct genotypes or assemblages, designated A–H, and assemblages A and B can infect humans. Giardiasis has been classified as a possible zoonotic disease but the role of animals in human disease transmission still needs to be proven. We tried to link different assemblages and sub-assemblages of G. intestinalis isolates from Swedish human patients to clinical symptoms and zoonotic transmission.Methodology/Principal FindingsMultilocus sequence-based genotyping of 207 human Giardia isolates using three gene loci: ß-giardin, glutamate dehydrogenase (gdh), and triose phosphate isomerase (tpi) was combined with assemblage-specific tpi PCRs. This analysis identified 73 patients infected with assemblage A, 128 with assemblage B, and six with mixed assemblages A+B. Multilocus genotypes (MLGs) were easily determined for the assemblage A isolates, and most patients with this genotype had apparently been infected through anthroponotic transmission. However, we also found evidence of limited zoonotic transmission of Giardia in Sweden, since a few domestic human infections involved the same assemblage A MLGs previously reported in Swedish cats and ruminants. Assemblage B was detected more frequently than assemblage A and it was also more common in patients with suspected treatment failure. However, a large genetic variability made determination of assemblage B MLGs problematic. Correlation between symptoms and assemblages was found only for flatulence, which was significantly more common in children less than six years of age infected with assemblage B.Conclusions/SignificanceThis study shows that certain assemblage A subtypes are potentially zoonotic and that flatulence is connected to assemblage B infections in young children. Determination of MLGs from assemblages A and B can be a valuable tool in outbreak situations and to help identify possible zoonotic transmission.

Is Predominant Clonal Evolution a Common Evolutionary Adaptation to Parasitism in Pathogenic Parasitic Protozoa, Fungi, Bacteria, and Viruses?

“…Evidence for strong LD between different kinds of markers is abundant in this species Monis et al, 2009), with 'assemblages', that are perfectly equatable to near-clades (Tibayrenc and Ayala, 2014b). Giardia assemblages (labelled A to G) exhibit a neat, but not strict, host specificity and some phenotypic differences, and are corroborated by MLEE and gene sequences (Cacci o and Ryan, 2008;Lasek-Nesselquist et al, 2009;Lebbad et al, 2011;Monis et al, 2009;Ortega-Pierres et al, 2009;Plutzer et al, 2010;Takumi et al, 2012;Xu et al, 2012). Additional subdivisions ('subassemblages') can be identified within the assemblages.…”

Enteric Protozoa in the Developed World: a Public Health Perspective

“…However, this is unsupported, since many long-term infections are suspected to represent either persisting abdominal symptoms elicited post-Giardia infection or reinfections (176,196,484). The fecal-oral route still remains the most important mode of infection (33), and various studies have found evidence of zoonotic transmission (89,118,237). The symptoms of giardiasis can be variable, but it presents mainly as acute or chronic diarrhea associated with abdominal pain, nausea, malabsorption, and weight loss.…”

Genotipos de Giardia duodenalis en niños de las guarderías del Instituto Colombiano de Bienestar Familiar y de caninos en Ibagué, Tolima, Colombia

“…En algunos estudios recientes se ha sugerido que esta especie debería considerarse como un complejo de especies cuyos miembros, aunque morfológicamente idénticos, presentan variaciones genéticas que han permitido dividirla en, al menos, ocho genotipos (del A al H) (4).…”