To the Editor: Streptococcus suis is an emerging zoonosis in humans and a common pathogen in Australian pigs.1 However, only two cases of human infection have previously been reported in Australia.2,3 We recently treated two Australian piggery workers, from the same town in New South Wales, for S. suis endocarditis.

The first patient, a previously healthy 46-year-old woman, presented in October 2006 with a 3-month history of fatigue, anorexia, night sweats and weight loss of 20 kg. Her job involved hands-on work at a piggery. She was afebrile, with blood pressure of 145/50 mmHg, bilateral clubbing, splenomegaly, and a long diastolic murmur without evidence of heart failure. Transthoracic echocardiography confirmed severe aortic regurgitation associated with a vegetation. Blood cultures grew S. suis. The patient was treated with benzylpenicillin (1.8 g, 4-hourly for 6 weeks) and gentamicin (60 mg, 8-hourly for 2 weeks). Severity of aortic regurgitation necessitated aortic valve replacement.

The second patient, a 58-year-old man, presented in January 2008 with headache, fever (38.7°C), neck stiffness and confusion. He had been unwell for 1 month with fevers, sweating, fatigue and weight loss of 6 kg. His job involved transporting pigs from local piggeries, including the one at which the first patient worked, to an abattoir, and involved direct contact with pigs. On admission, he was treated with ceftriaxone (2 g) and benzylpenicillin (2.4 g). Cerebrospinal fluid (CSF) examination showed leukocytosis (10 300 × 106/L; reference range, < 5 × 106/L) with 95% polymorphs. Scanty gram-positive cocci were visible, but there was no growth on culture of the CSF. Blood cultures grew S. suis. Transthoracic echocardiography revealed an aortic valve vegetation with trivial regurgitation. The patient was then treated with benzylpenicillin (1.8 g, 4-hourly for 4 weeks) and gentamicin (80 mg, 8-hourly for 2 weeks), and made a full recovery.

Both cases were investigated by the NSW Department of Health, including assessment of workplace practices, staff education and rates of porcine infection at the piggeries and abattoir at which the patients had worked, but no significant factors for infection were identified.

Since the first reported human infection with S. suis in Denmark in 1968,4 more than 400 cases have been reported, including an outbreak in China in 2005 that affected 215 people.5 The most common manifestations are meningitis (affecting 72.5% of patients) and bacteraemia (24.2%); endocarditis is relatively uncommon (1.1%).5 In a series of 16 cases of S. suis endocarditis, the mean period between onset of symptoms and diagnosis was 23 days, and seven patients required valve replacement.6 Similarly, our patients had subacute presentations: severe aortic regurgitation and secondary meningitis. In Australia, it is likely that there have been other S. suis infections in humans that have gone unrecognised because of mild presentations, difficulties with laboratory diagnosis, and empirical treatment of unrecognised infection. While it is unlikely that S. suis is a common zoonosis in Australia, these cases show that it is an occupational hazard in Australian piggeries, with potential public health, animal health and medicolegal implications.