Giardia duodenalis multi-locus genotypes in dogs with different levels of synanthropism and clinical signs

Abstract

Background In dogs, infections with Giardia duodenalis are mainly caused by assemblages C and D, but also by the potentially zoonotic assemblages A and B. The aims of this study were to assess differences in assemblages (i) between dogs living mainly in close proximity to humans (synanthropic dogs) versus dogs living mainly among other dogs, (ii) between samples of dogs with or without loose stool, and (iii) related to the amount of cysts shedding. Methods One hundred eighty-nine qPCR Giardia positive fecal samples of dogs originating from four groups (household, sheltered, hunting, and dogs for which a veterinarian sent a fecal sample to a diagnostic laboratory) were used for genotyping. For this, multi-locus genotyping of beta-giardin, triose phosphate isomerase, and glutamate dehydrogenase and genotyping of SSU rDNA gene fragments were performed. Fecal consistency was scored (loose or non-loose stool), and cysts per gram of feces were determined with qPCR. Results Assemblage D was the most prevalent in all groups, followed by the other canid assemblage C. Also, mixed C/D was common. In two (synanthropic) household dogs, the potentially zoonotic assemblage AI was present. Although occurrence of assemblage AI in household dogs was not significantly different from dogs living among other dogs (sheltered and hunting dogs), it was significantly higher compared to dogs for which a sample was sent to a diagnostic laboratory. Dogs with assemblage D shed significantly more cysts than dogs with other assemblages (except for mixed C/D results) or dogs in which no assemblage could be determined. None of the assemblages was significantly associated with loose stool. Conclusion Not only do dogs mainly shed the canid Giardia duodenalis assemblages D and/or C, the numbers of cysts per gram for the canid assemblage D were also higher than for the potential zoonotic assemblage AI. Based on the assemblages shed by dogs, the risk to public health posed by dogs is estimated to be low, even though the dogs that shed AI were synanthropic household dogs. Loose stool in infected dogs was not associated with any particular Giardia assemblage.

Gastrointestinal parasites in young dogs and risk factors associated with infection

“…In accordance with former studies, genotyping results showed that the majority of the Giardia positive samples were allocated to the canine type, consisting of the assemblages C and D (38.4 (43/112) and 35.7% (40/112)), respectively (Johansen et al 2014;Pallant et al 2015;Zhang et al 2017;Sommer et al 2018;Uiterwijk et al 2020). Furthermore, we were able to identify 8% (9/112) of the isolates as the potentially zoonotic assemblage A.…”

“…Dogs are particularly affected by the canine-specific types C and D, which are responsible for most of the infections in dogs. However, in several studies, assemblages A and more rarely B have also been detected (Ballweber et al 2010;Sotiriadou et al 2013;Sommer et al 2018;Uiterwijk et al 2020). In addition to G. duodenalis, also other endoparasites, such as T. canis, are potentially zoonotic and transmitted via the fecal-oral route by direct contact with the agent or through contaminated water or food (Thompson and Monis 2012;Macpherson 2013;Chen et al 2018).…”

Prevalence, Risk Factors and Genotypes of Giardia duodenalis in Sheltered Dogs in Tuscany (Central Italy)

“…These findings may suggest that a number of factors may contribute to the high prevalence of G. duodenalis in this kennel. Overcrowding is considered a favourable factor for the spread of this protozoan parasite [3,8,16]. Effective sanitisation and control measures may also be more difficult to perform in these conditions.…”

“…Assemblages C and D are canine specific. Assemblages A and B are most frequently found in humans, but they can also infect other animals and are considered potentially zoonotic [5][6][7][8]. Assemblages A and B have been further divided into sub-assemblages (A-I to A-III and B-III, B-IV), some of which are more common in humans and others in animals [2,5].…”

“…The prevalence of G. duodenalis infection in dogs varies depending on the population and area under examination, the diagnostic method used and the health status of the animals examined [16,17]. Young dogs, mainly puppies under 6 months of age, and some dog populations, such as stray or community-living animals, and breeding and sheltered dogs, show a higher risk of infection [4,8,16]. Furthermore, in conditions of high animal density and in highly contaminated environments, such as in shelters, repeated infections can be observed due to poor protection conferred by the immune system, continuous exposure to the parasite and continuous introduction of new animals [5,16,18].…”