Prevalence of Human Specific Giardia lamblia in Irish Sheltered Canines: An Unknown Risk Factor for Human Infection

Abstract

Giardia lamblia is a prominent cause of parasitic-induced diarrhoea with prolonged infections linked to temporary malabsorption. In 2018, 270 giardiasis cases were notified in Ireland, a six-fold increase since 2013. Although G. lamblia is genetically grouped into 8 host-specific assemblages, with A and B specific to human infection and C and D specific to canine infection, reports of human-specific assemblages in canines are becoming more frequent. With increasing cases in Ireland and reports of zoonotic transmission potential, the aim of this study was to assess the prevalence of G. lamblia in Irish sheltered canines. Faecal samples were collected from two dog shelters in the west of Ireland. Real-time PCR was used to detect G. lamblia. Risk factors for G. lamblia colonisation were statistically analysed. Overall, 51 faecal samples were collected with a 67% prevalence of G. lamblia. There were 38% of dogs positive in Shelter 1 and 87% in Shelter 2. Shelter of origin (p=0.0006) and time spent in shelter (p=0.0013) were significantly associated with increased G. lamblia prevalence, with dogs present in the shelter more than two weeks 10 times more likely to be infected with G. lamblia (Odds Ratio:10.185; Confidence Interval:2.303-45.044). This is the first Irish study to assess presence of G. lamblia in dogs using real-time PCR. The high prevalence among asymptomatic dogs shows their potential to contribute to human illness if correct hand-hygiene is not observed. This quantitative data is important in the implementation of effective measures to tackle giardiasis in Ireland.