Tilapia lake virus,
United States of America
Information received on 08/05/2019 from Dr Jack Shere, Deputy Administrator Chief Veterinary Office r, USDA-APHISVeterinary Services, USA United States Department of Agriculture, WASHINGTON, United States of America
Summary
Report type Immediate notification
Date of start of the event 05/11/2018
Date of confirmation of the event 22/03/2019
Report date 06/05/2019
Date submitted to OIE 08/05/2019
Reason for notification Emerging disease
Morbidity 2.5 (scale 0 to 5)
Mortality 2.5 (scale 0 to 5)
Zoonotic impact No
Causal agent Tilapia lake virus
Serotype Other
New outbreaks (3)
Outbreak 1 Caribou County, Caribou, Idaho
Date of start of the outbreak 05/11/2018
Outbreak status Resolved (02/05/2019)
Epidemiological unit Farm
Water type Fresh water
Population type Farmed
Production system Semi-closed
Affected animals
Species Morbidity Mortality Susceptible Cases Deaths Killed and disposed of Slaughtered
Nile Tilapia (Oreochromis niloticus) 2 (scale 0 to 5) 2 (scale 0 to 5) 154000 22000
Affected population Multiple age class commercial farm.
Outbreak 2 Niobrara County, Niobrara, Wyoming
Date of start of the outbreak 07/12/2018
Outbreak status Continuing (or date resolved not provided)
Epidemiological unit Farm
Water type Fresh water
Population type Farmed
Production system Closed
Affected animals
Species Morbidity Mortality Susceptible Cases Deaths Killed and disposed of Slaughtered
Nile Tilapia (Oreochromis niloticus) 3 (scale 0 to 5) 3 (scale 0 to 5) 30000 11500
Affected population Multiple age class commercial farm.
Outbreak 3 Fremont County, Fremont, Colorado
Date of start of the outbreak 22/04/2019
Outbreak status Continuing (or date resolved not provided)
Epidemiological unit Farm
Water type Fresh water
Population type Farmed
Production system Closed
Affected animals
Species Morbidity Mortality Susceptible Cases Deaths Killed and disposed of Slaughtered
Nile Tilapia (Oreochromis niloticus) 1 (scale 0 to 5) 0 (scale 0 to 5) 22000 0
Affected population Multiple age class commercial farm. No clinical signs of disease present at this facility.
Summary of outbreaks Total outbreaks: 3
Total animals affected
Species Susceptible Cases Deaths Killed and disposed of Slaughtered
Nile Tilapia (Oreochromis niloticus) 206000 ** 33500
Outbreak statistics
Species Apparent morbidity rate Apparent mortality rate Apparent case fatality rate Proportion susceptible animals lost*
Nile Tilapia (Oreochromis niloticus) ** ** ** **
*Removed from the susceptible population through death, destruction and/or slaughter
**Not calculated because of missing information
Epidemiology
Source of the outbreak(s) or origin of infection
  • Introduction of new live animals
Epidemiological comments The United States Department of Agriculture (USDA) Animal Plant Health Inspection Services (APHIS) and the State Departments of Agriculture are conducting a comprehensive epidemiological investigation of this event. The epidemiological investigation determined that clinical signs consistent with Tilapia lake virus (TiLV) were first observed on the index premises in November 2018. All clinically ill fish were depopulated. Exposed fish in the same tanks will either be depopulated or sent to terminal market. The affected holdings will be cleaned and disinfected. Surveillance and testing related to this event are ongoing. This is the first detection of TiLV in the United States.
Control measures
Measures applied
  • Surveillance outside infected and/or protection zone
  • Quarantine
  • Selective killing and disposal
  • Disinfection
  • Vaccination permitted (if a vaccine exists)
  • No treatment of affected animals
Measures to be applied
  • No other measures
Diagnostic test results
Laboratory name and type Species Test Test date Result
National Veterinary Services Laboratories (National laboratory) Nile Tilapia (Oreochromis niloticus) gene sequencing 15/03/2019 Positive
National Veterinary Services Laboratories (National laboratory) Nile Tilapia (Oreochromis niloticus) reverse transcription - polymerase chain reaction (RT-PCR) 08/03/2019 Positive
National Veterinary Services Laboratories (National laboratory) Nile Tilapia (Oreochromis niloticus) reverse transcription - polymerase chain reaction (RT-PCR) 29/04/2019 Positive
National Veterinary Services Laboratories (National laboratory) Nile Tilapia (Oreochromis niloticus) virus isolation 22/03/2019 Positive
Private Laboratory (Private Laboratory) Nile Tilapia (Oreochromis niloticus) virus isolation 26/02/2019 Positive
Future Reporting
The event is continuing. Weekly follow-up reports will be submitted.
Map of outbreak locations