CASE NOTES
Testicular seminoma diagnosed and Brucella suis excluded in a feral boar in south-east NSW
Alexandra Stephens, District Veterinarian, Yass
Posted Flock and Herd November 2024
Introduction
Brucellosis in pigs is caused by the bacterium Brucella suis which causes orchitis and reproductive failure and poses a zoonotic risk. It is known to be present in feral pig populations in northern NSW but despite continual monitoring, we are yet to detect the disease in southern NSW. Passive surveillance techniques are used to monitor for incursion of the disease, which rely on prompt notification of anything unusual by producers, prompt follow up by the biosecurity team, adequate funding of testing of notifiable diseases and a skilled pathology team at the government veterinary diagnostic laboratory.
History
On the 29th May 2023 the senior Local Land Services Biosecurity Officer at Goulburn was called by a local producer who had shot a feral boar the evening before and was very concerned that the boar had noticeably swollen testicles. Brucella suis is not known to occur in the South East region but all producers and pig hunters in the area have been advised to be constantly vigilant for anything unusual, in particular swollen testicles. The relationship between landholders and biosecurity staff in the area and their knowledge of feral pigs diseases was enhanced by the operation of the 2023 feral pig state program.
Image 1. Photograph provided by the producer to the Biosecurity Officer
The producer left the deceased pig in situ and sent a pin drop of its exact location to the biosecurity team. The Biosecurity Officers organised an available District Veterinarian from a nearby district to attend to support them in conducting a post-mortem in appropriate PPE. The EMAI sample collection information sheets and a call to the laboratory were used as guides for the most appropriate samples to take to exclude Japanese Encephalitis and Brucella suis. The concern was to collect samples while appropriately protected from the zoonotic potential of either Japanese Encephalitis or Brucella suis. Hands were inspected for cuts with band-aids applied, a P2 mask, overalls and double gloves were worn by all attending to avoid any possibility of blood or reproductive products coming in contact with wounds or being inhaled.
Necropsy findings
The post-mortem was conducted that morning by the biosecurity staff under the supervision of the veterinarian. The boar was mature, as judged by his tusk and general size, in moderate body condition score but with a huge swelling, 35cm by 25cm in the testicular region. A full post-mortem was conducted. Noticeable lesions were an abscess of the pharyngeal lymph node and a large mass in the area of the lower abdomen/prostate and a very enlarged left testicle. The testicular tissue was extremely unusual with hard caseous abscessed areas and fluid pockets. Fresh and fixed samples were collected from the pharyngeal lymph-nodes, lungs, spleen, liver, kidneys, testicular tissue and lower abdominal mass. A swab was taken from the abscess, and thoracic and testicular fluid collected. At the completion of the post-mortem the Biosecurity Officer then advised the producer to bury the pig to avoid any potential zoonotic risk and potential for disease spread via scavenging.
Image 2. Full lateral recumbent post-mortem display
Image 3 and 4: Cut surface of abnormal testicular mass
Laboratory findings
The samples were labelled as potentially zoonotic and sent by overnight courier to EMAI. The veterinary pathologist for the case at EMAI was Pedro Pinczowski (M23-09556). Japanese Encephalitis Virus qRT-PCR test was performed on the liver, kidney, spleen and tonsil with negative results on all. A Brucella suis PCR was performed on the testicular abscess fluid, with a 'not detected' result. A culture for Brucella spp. was performed on the testes, testicular abscess fluid, and tonsil abscess with negative results on all. A general culture was performed on the tonsil abscess swab, with a predominant growth of Schaalia hyovaginalis and also of Trueperella pyogenes. The testes, testicular fluid and thoracic fluid had no significant growth.
The definitive diagnosis was obtained through histopathology with the morphological diagnosis being a testicular seminoma, with marked coagulative necrosis. There was complete loss of testicular structure with marked coagulative necrosis of normal parenchyma and replacement by a highly cellular, encapsulated, well demarcated neoplasm and abundant mineral deposits. Seminomas are a form of testicular neoplasia, derived from germ cells. They are most prevalent in the dog, and rarely reported in boars. The infiltration of the tumour cells into the surrounding vessels and tissues demonstrated the possibility of it being a malignant form.
Conclusion
This case demonstrates the NSW surveillance system working at its best. The extension work done in the area raising awareness of Brucella suis and the good relationship between producers and the biosecurity staff led to this case being promptly notified to the LLS. The confidence of the biosecurity staff to respond immediately with a farm visit and to wear appropriate PPE and conduct a post-mortem shows the benefit of the 2023 NSW field training workshops. Appropriate fact sheets and good prompt communication from the laboratory facilitated correct sample collection. A highly skilled pathology and laboratory team at EMAI not only excluded notifiable diseases through multiple appropriate testing but were also able to supply a quality definitive diagnosis within one week of samples arriving at the laboratory.