Abstract
BackgroundGiardia duodenalis is one of the most common enteric parasites in domestic animals including dogs. Young animals are more prone to the infection, with clinical manifestations ranging from asymptomatic to acute or chronic diarrhoea. Dogs are primarily infected by canine-specific (C-D) assemblages of G. duodenalis. However, zoonotic assemblages A and B have been increasingly documented in canine isolates, raising the question of whether and to which extent dogs can act as natural reservoirs of human giardiosis.MethodsIn this cross-sectional epidemiological survey we assessed the molecular diversity of G. duodenalis in dogs in the province of Castellón, Eastern Spain. A total of 348 individual faecal samples from sheltered (n = 218), breeding (n = 24), hunting (n = 68), shepherd (n = 24), and pet (n = 14) dogs were collected between 2014 and 2016. Detection of G. duodenalis cysts in faecal material was carried out by direct fluorescence microscopy as a screening test, whereas a qPCR targeting the small subunit ribosomal RNA gene of the parasite was subsequently used as a confirmatory method.ResultsGiardia duodenalis was detected in 36.5% (95% CI: 31.6–41.7%) of dogs. No significant differences in prevalence rates could be demonstrated among dogs according to their sex and geographical origin, but breeding (45.8%; 95% CI: 27.9–64.9%) and sheltered (40.4%; 95% CI: 34.1–47.0%) dogs harboured significantly higher proportions of G. duodenalis. Multi-locus sequence-based genotyping of the glutamate dehydrogenase and β-giardin genes of G. duodenalis allowed the characterization of 35 canine isolates that were unambiguously assigned to assemblages A (14.3%), B (22.9%), C (5.7%), and D (37.1%). A number of inter-assemblage mixed infections including A + B (11.4%), A + D (2.9%), and A + B + D (5.7%) were also identified.ConclusionsData presented here are strongly indicative of high infection pressures in kennelled animals. Zoonotic sub-assemblages AII, BIII, and BIV were responsible for a considerable proportion of the G. duodenalis infections detected, but very few of the genotypes identified have been previously documented in Spanish human populations. Although possible, zoonotic transmission between dogs and humans seems an infrequent event in this Spanish region.
Highlights
Giardia duodenalis is one of the most common enteric parasites in domestic animals including dogs
Detection of G. duodenalis in canine faecal samples The overall prevalence of G. duodenalis in the investigated dog population was estimated at 36.5% [95% Confident Interval (CI): 31.6–41.7%]
Out of the 127 dogs that tested positive by direct fluorescent antibody test (DFAT), 81.1% (103/127) were confirmed by Real-time polymerase chain reaction (qPCR), whereas 18.9 (24/127) failed to be detected by the latter method
Summary
Giardia duodenalis is one of the most common enteric parasites in domestic animals including dogs. Zoonotic assemblages A and B have been increasingly documented in canine isolates, raising the question of whether and to which extent dogs can act as natural reservoirs of human giardiosis. The enteric protozoan parasite Giardia duodenalis is one of the most commonly detected pathogens associated with diarrhoea in humans and animals, including domestic dogs [6, 7]. As in other host species, canine infections by G. duodenalis can present with a broad range of clinical manifestations from asymptomatic to acute or chronic disease [8, 9]. Assemblages A and B have the widest host ranges, infecting humans, domestic animals and livestock and a large number of wildlife species, and are considered zoonotic. Assemblages C and D are found mainly in dogs, assemblage E in hoofed animals, assemblage F in cats, assemblage G in rodents, and assemblage H in marine mammals [10, 11]
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