QX disease of oysters


QX is a seasonally occurring disease of Sydney Rock Oysters (Saccostrea glomerata) known to have caused impacts in a limited number of estuaries in NSW. QX disease is caused by a protozoan parasite (Marteilia sydneyi). This organism has a lifecycle which is thought to involve at least two hosts. The oyster is the host in which the parasite sporulates. Infected oysters show non-specific signs including lack of growth, loss of condition and pale digestive glands on gross inspection.

Diagnosis and tests available


For the best diagnostic outcome please submit affected oysters. Cytology and histopathology are confirmatory tests.

Tests available


Sample(s) required

Days of the week test is conducted

Turnaround time1

Cytology examination (Digestive gland impression smears)

Whole fresh oysters

Monday – Friday

Up to 5 days

Histopathology examination

Fixed tissue

Monday –Friday

Up to 5 days

Necropsy examination

Whole fresh oysters

Monday – Friday

Same day


Fresh tissues removed at necropsy of whole oysters

On demand


1 Turnaround times are provided as a guide only. For specific information about your submission please contact Customer Service.
2 The test is not NATA accredited

Specimen requirements

Fixed tissue

  • Affected tissue
    • Submit fixed in neutral buffered formalin at a 10:1 ratio of formalin:tissue

Fresh oysters

  • Whole oysters
    • Submit live representative affected oysters, collected from amongst the oysters showing the greatest mortality, in an insulated container with ice or a cool brick

Further information