Characterization of the Blastocystis-specific faecal IgA immune response in pigs.

Blastocystis is an intestinal protist found in many species including humans and pigs. It has a controversial pathogenesis and has been implicated as a potential cause of irritable bowel syndrome. Our previous studies identified pigs as potential animal models for blastocystosis by demonstrating that they were likely natural hosts of Blastocystis and can harbour subtypes (ST) in common with humans. Furthermore, our finding of a lack of intestinal histopathology associated with Blastocystis infection in pigs is also a consistent finding in examined infected humans. In this study, we aimed to identify and characterize the Blastocystis-specific mucosal IgA response in pigs by immunoblotting, using pig faecal antibodies and Blastocystis antigen. Faeces from 233 pigs representing three age groups (sows/boars, growers/weaners and piglets) and including five dexamethasone-immunosuppressed research pigs were tested. The majority (81·5%) of the pigs had faecal IgA reactivity against Blastocystis proteins of molecular weights of 17·5-120 kDa. Reactivity to a >250 kDa protein was found in 18·5% of pigs. Notably, immunosuppressed pigs and piglets were statistically more likely to have reactivity to this protein compared to growers/weaners and sows/boars, respectively. These results corroborate other findings suggesting that compromised immunity may predispose to blastocystosis and support our contention that pigs are potentially good models for pathogenesis studies.

Blastocystis subtypes in symptomatic and asymptomatic family members and pets and response to therapy.

BACKGROUND: Blastocystis is a common, enteric parasite. The pathogenicity of the organism is uncertain, but subtypes (ST) 1 and 3 have been reported more likely to cause irritable bowel-like symptoms. AIMS: We treated symptomatic patients positive for Blastocystis with conventional therapy and analysed 16 small-subunit (SSU) rDNA to assess clearance and carriage rates and ST prevalence of the parasite in the asymptomatic household members. METHODS: In a longitudinal, prospective case study, 11 symptomatic patients positive for Blastocystis underwent outpatient clinical assessment to exclude other diagnoses before 14 days of either metronidazole 400 mg three times daily or trimethoprim/sulfamethoxazole 160/800 mg twice-daily therapy. Faecal specimens were collected from patients at baseline, day 15, 28 and 56 after therapy and from 17 family members and eight pets at day 15. Specimens were analysed using faecal smear, culture and polymerase chain reaction analysis of 16SSU rDNA. RESULTS: No patient cleared the organism following therapy. ST 1 (45%), 3 (36%), 4 (36%) and 6 (9%) were found in the symptomatic Blastocystis patients, and ST identified before and after therapy were identical in each individual. All household contacts were positive for Blastocystis and 16/17 (94%) contacts showed identical Blastocystis ST to the symptomatic family member. All pets were positive for Blastocystis with polymerase chain reaction testing, 7/8 (88%) demonstrating ST concordance with the symptomatic Blastocystis patients. CONCLUSIONS: Conventional therapy is ineffective for symptomatic Blastocystis infection. The high prevalence of Blastocystis infection within households suggested transmission between humans and their pets. Subtyping analysis of SSU rDNA alone in Blastocystis does not appear to predict pathogenicity.

First report of a Trichinella papuae infection in a wild pig (Sus scrofa) from an Australian island in the Torres Strait region.

Multiple Trichinella species are reported from the Australasian region although mainland Australia has never confirmed an indigenous case of Trichinella infection in humans or animals. Wildlife surveys in high-risk regions are essential to truly determine the presence or absence of Trichinella, but in mainland Australia are largely lacking. In this study, a survey was conducted in wild pigs from mainland Australia's Cape York Peninsula and Torres Strait region for the presence of Trichinella, given the proximity of a Trichinella papuae reservoir in nearby PNG. We report the detection of a Trichinella infection in a pig from an Australian island in the Torres Strait, a narrow waterway that separates the islands of New Guinea and continental Australia. The larvae were characterised as T. papuae (Kikori strain) by PCR and sequence analysis. No Trichinella parasites were found in any pigs from the Cape York Peninsula. These results highlight the link the Torres Strait may play in providing a passage for introduction of Trichinella parasites from the Australasian region to the Australian mainland.