Occurrence and molecular epidemiology of Giardia duodenalis infection in dog populations in eastern Spain.

BACKGROUND: Giardia 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. METHODS: In 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. RESULTS: Giardia 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 ß-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. CONCLUSIONS: Data 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.

High Prevalence and Diversity of Zoonotic and Other Intestinal Parasites in Dogs from Eastern Spain.

The diversity and frequency of enteric parasites in dog populations in the Castellón province (Eastern Spain) were assessed using a prospective cross-sectional epidemiological survey. A total of 263 canine fecal samples were collected between July 2014 and July 2016. Detection of intestinal parasites was conducted by routine coprological methods. In addition, identification of Giardia duodenalis and Cryptosporidium spp. was carried out by direct immunofluorescence microscopy, whereas the presence of Strongyloides spp. was assessed by real-time PCR in a selected number of specimens. Based on conventional and/or immunofluorescence microscopy examination, 65.8% (95% confidence interval: 59.7-71.5) of the investigated dogs were found infected by at least one gastrointestinal parasite. G. duodenalis (35.4%) and members of the family Ancylostomatidae (27.0%) were the most prevalent protozoan and helminth parasites found, respectively. Other pathogens potentially infective to humans included Toxocara canis (8.0%), Cryptosporidium spp. (6.8%), and Strongyloides spp. (1.1%). Frequency of occurrence of helminthic, but not protozoan, enteroparasites was geographical origin dependent (p = 0.02), with dogs living in coastal areas presenting higher infection rates than those living in inland regions. Similarly, rural dogs were significantly more infected than urban dogs (p < 0.001). Our results revealed that zoonotic agents were common in dogs from the Castellón province. Animals from rural areas and sheltered dogs were particularly at risk of these infections.