MIKROCYTOSIS( MIKROCYTOS MACKINI )IN THE UNITED STATES OF AMERICA
Information received by OIE on 18 July 2002 from Dr Peter Fernandez, Associate Deputy Administrator, International Services, United States Department of Agriculture (USDA), Washington, DC:
Report date: 18 July 2002.
Nature of diagnosis: laboratory.
Date of initial detection of animal health incident: 8 May 2002.
Estimated date of first infection: 1 May 2002.
Location : New Dungeness Bay, State of Washington
No. of outbreaks: 1
Description of affected population: Pacific oyster( Crassostrea gigas ).
A sample of 50 feral oysters contained 2 that were identified as positive on cytological and histological examination for mikrocytosis. The two oysters were feral in an oyster farming bay and estimated to be at least five years of age. There was no report or sign of mortality or morbidity following examination of the oysters in the bay. The survey examination of the oysters was made as part of a routine surveillance effort. The infections were very light in the two confirmed cases.
A. Laboratories where diagnosis was made:
- The cases were diagnosed on 8 May 2002 by AquaTechnics, Sequim, State of Washington.
- Diagnosis was confirmed by the Pacific Biological Station, Canada.
B. Diagnostic tests used:
- Tissue imprints and histological examination.
- Research application of the PCR (1) method confirmed the tentative diagnosis of the two histologically positive samples and confirmed the other 48 samples as negative.
C. Causal agent: Mikrocytos mackini .
A. Source of agent / origin of infection: this is the first identification of M. mackini in the United States of America. Despite investigations, the source of the introduction of the pathogen into the New Dungeness Bay has not yet been identified.
B. Mode of spread: unknown.
C. Other epidemiological details: oysters from the nearby farm grown on longlines have previously tested negative for M. mackini . These findings are consistent with those in Canada where only older oysters grown on bottom culture appear to become infected with M. mackini .
Control measures: currently, the movement of oysters from New Dungeness Bay to other receiving waters is restricted by the Washington Department of Fish and Wildlife.
(1) PCR: polymerase chain reaction.