Molecular survey finds widespread Cryptosporidium and limited Giardia in Victorian pigs

A molecular survey of pigs across 37 farms in Victoria, Australia, found Cryptosporidium in 51.1% of faecal samples and Giardia duodenalis in 1.1%, establishing the first molecular baseline for these enteric protozoa in the state. Cryptosporidium occurred on 28 of the 37 farms surveyed, while G. duodenalis was detected on three. The study also identified two Cryptosporidium subtypes previously recorded in humans, indicating that some parasite genotypes circulating in Victorian pigs have zoonotic potential.

Researchers collected 626 faecal samples representing multiple age groups from farms across Victoria. They used nested polymerase chain reaction assays targeting the small-subunit nuclear ribosomal RNA gene for Cryptosporidium and the tpi locus for G. duodenalis, then amplified the gp60 locus to characterise Cryptosporidium subtypes. Amplified products were analysed by Sanger sequencing. The cross-sectional survey estimated parasite prevalence and examined species composition and genetic diversity within the sampled pig population.

Cryptosporidium detections were dominated by two species. C. scrofarum accounted for 77.5% of Cryptosporidium-positive samples and C. suis for 18.4%. DNA from a third species, C. ubiquitum, was detected in three samples, all from a single farm. Subtyping identified the C. suis subtype XXVa-1 and the C. ubiquitum subtype XIIa; both have previously been identified in humans. This does not demonstrate transmission from pigs to people, but it shows that genotypes of public-health interest are present in the surveyed production environment.

By contrast, G. duodenalis was uncommon: seven of 626 samples were positive, corresponding to a prevalence of 1.1%. The infections occurred on three farms and comprised five samples with assemblage E and two with assemblage A. These findings describe low detected prevalence in this sample rather than establishing the parasite’s distribution throughout Victoria. Cryptosporidium prevalence, however, varied markedly among age groups and production systems, reaching 68.6% among weaners and 78.2% on semi-intensive farms, while it was absent from adult pigs.

The results show that Cryptosporidium is widespread across the Victorian pig farms included in the study, with detection in more than three-quarters of participating properties. The authors describe the work as the first molecular assessment of Cryptosporidium and G. duodenalis in pigs from Victoria and call for continued surveillance and targeted parasite management in Australian pig production. The geographic scope remains important: the estimates are based on 626 samples from 37 farms, and the absence of G. duodenalis outside three sampled farms should not be interpreted as proof that it is absent from other farms. Nevertheless, the baseline identifies frequent Cryptosporidium occurrence, limited detected G. duodenalis infection and zoonotically relevant Cryptosporidium genotypes in the state’s pig population.

Subject of Research: Molecular prevalence and genetic diversity of Cryptosporidium and Giardia duodenalis in pigs from Victoria, Australia

Article Title: First molecular survey of pigs in Victoria, Australia, reveals widespread Cryptosporidium infection, limited Giardia duodenalis occurrence and genotypes with zoonotic potential

Article References: Xu, J., Abbas, G., Gauci, C. G., Gasser, R. B., Jabbar, A., & Koehler, A. V. (2026). First molecular survey of pigs in Victoria, Australia, reveals widespread Cryptosporidium infection, limited Giardia duodenalis occurrence and genotypes with zoonotic potential. Parasites & Vectors. https://doi.org/10.1186/s13071-026-07739-w

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07739-w

Keywords: Cryptosporidium, Giardia duodenalis, pig parasites, molecular epidemiology, zoonotic potential, Victorian agriculture, parasite surveillance, weaner pigs, First, molecular, survey, pigs