Molecular detection of Giardia duodenalis and the absence of Cryptosporidium spp. in owned dogs from Central Vietnam

Introduction Giardia duodenalis and Cryptosporidium spp. are ubiquitous enteric protozoans of significant public health and veterinary concern. Despite their global importance, molecular epidemiological data concerning companion animals in Vietnam remain limited. Methods This cross-sectional study evaluated the prevalence, investigated the specific Giardia assemblages and Cryptosporidium species, and identified risk factors associated with these parasites in 362 owned dogs in Dak Lak province, Central Vietnam. Genomic DNA extracted from fecal samples was screened using nested PCR targeting the small subunit ribosomal RNA (SSU rRNA) locus, followed by sequencing of positive amplicons. Epidemiological risk factors were assessed using multivariable logistic regression. Results The overall prevalence of G. duodenalis was 8.0% (29/362; 95% confidence interval [CI]: 5.6–11.3%), whereas Cryptosporidium spp. DNA was not detected. Sequencing of 18 Giardia -positive isolates exclusively identified the canine-specific assemblage D. Multivariable analysis revealed that direct contact with other dogs (adjusted odds ratio [aOR] = 7.55; 95% CI: 1.69–33.82; P = 0.008) and unbathed status (aOR = 0.30; 95% CI: 0.11–0.83; P = 0.021) were significant predictors of infection. Host demographics, location, outdoor access, and deworming history had no significant association with Giardia positivity. Discussion The exclusive detection of assemblage D indicates that dogs in this rural setting currently pose a minimal direct zoonotic risk to the local human population. These findings emphasize the importance of improving canine management practices, particularly through proper hygiene and the restriction of uncontrolled interactions between dogs, to mitigate transmission risks.