Epizootic ulcerative syndrome,
Botswana
Information received on 08/08/2020 from Dr Letlhogile Modisa, Director, Veterinary Services, Ministry of Agriculture, Gaborone, Botswana
Summary
Report type Immediate notification
Date of start of the event 31/07/2020
Date of confirmation of the event 31/07/2020
Report date 08/08/2020
Date submitted to OIE 08/08/2020
Reason for notification Recurrence of a listed disease
Date of previous occurrence 31/10/2010
Manifestation of disease Clinical disease
Causal agent Aphanomyces invadans
Nature of diagnosis Clinical
This event pertains to the whole country
Related reports Immediate notification (08/08/2020)
Follow-up report No. 1 (10/09/2020)
New outbreaks (1)
Outbreak 1 Kasane, Chobe, Chobe, Chobe
Date of start of the outbreak 31/07/2020
Outbreak status Continuing (or date resolved not provided)
Epidemiological unit River system
Water type Fresh water
Population type Wild
Production system Open
Affected animals
Species Morbidity Mortality Susceptible Cases Deaths Killed and disposed of Slaughtered
silver catfish (schilbe intermedius) 2 (scale 0 to 5) 1 (scale 0 to 5) 10000 32 6 0 0
Banded tilapia (Tilapia sparmanii) 2 (scale 0 to 5) 1 (scale 0 to 5) 253 4 0 0 0
Dash tail bard (Barbus poechi) 1 (scale 0 to 5) 0 (scale 0 to 5) 10000 5 0 0 0
Squicker (cynodontis species) 4 (scale 0 to 5) 2 (scale 0 to 5) 10000 32 25 0 0
Red breast Tilapia (Tilapia randolii) 1 (scale 0 to 5) 0 (scale 0 to 5) 10000 1 0 0 0
Sharp tooth catfish (Clarius gariepinus) 1 (scale 0 to 5) 1 (scale 0 to 5) 10000 3 0 0 0
Blunt tooth catfish (Clarias ngamensis) 2 (scale 0 to 5) 0 (scale 0 to 5) 10000 3 0 0 0
Affected population Wild Fresh water fish in Chobe /Zambezi river system
Summary of outbreaks Total outbreaks: 1
Total animals affected
Species Susceptible Cases Deaths Killed and disposed of Slaughtered
silver catfish (schilbe intermedius) 10000 32 6 0 0
Banded tilapia (Tilapia sparmanii) 253 4 0 0 0
Dash tail bard (Barbus poechi) 10000 5 0 0 0
Squicker (cynodontis species) 10000 32 25 0 0
Red breast Tilapia (Tilapia randolii) 10000 1 0 0 0
Sharp tooth catfish (Clarius gariepinus) 10000 3 0 0 0
Blunt tooth catfish (Clarias ngamensis) 10000 3 0 0 0
Outbreak statistics
Species Apparent morbidity rate Apparent mortality rate Apparent case fatality rate Proportion susceptible animals lost*
silver catfish (schilbe intermedius) 0.32% 0.06% 18.75% 0.06%
Banded tilapia (Tilapia sparmanii) 1.58% 0.00% 0.00% 0.00%
Dash tail bard (Barbus poechi) 0.05% 0.00% 0.00% 0.00%
Squicker (cynodontis species) 0.32% 0.25% 78.13% 0.25%
Red breast Tilapia (Tilapia randolii) 0.01% 0.00% 0.00% 0.00%
Sharp tooth catfish (Clarius gariepinus) 0.03% 0.00% 0.00% 0.00%
Blunt tooth catfish (Clarias ngamensis) 0.03% 0.00% 0.00% 0.00%
*Removed from the susceptible population through death, destruction and/or slaughter
Epidemiology
Source of the outbreak(s) or origin of infection
  • Unknown or inconclusive
  • Horizontal spread through water
Epidemiological comments Fisherman observed a large number of fish-eating birds crowding along the river banks. On close inspection, they noted that the birds were eating fish. Fisherman reported observing fish swimming sluggishly and crowding to the edges of the water along the bank. This was reported to the Department of Wildlife and National Parks, who upon investigation confirmed the incident. Fresh water fish of different species were observed to swimm slow in the shalow water along the river bank. Inspections of the fish, which were mainly fingerling size and slightly bigger, were observed to have intense inflammatory lesions, red areas on skin, deep ulcerations and deaths. Though number of susceptible animals was estimated at 10,000 in this report, the actual numbers are unknown for each species. Further a large number of dead fish and sick ones were being quickly eaten by birds making the counts for deaths and morbidity very inaccurate but the large numbers of birds indicated a far more serious problem probably high morbidity and mortality than estimated in this report. Laboratory examination and results are pending on the 91 specimen submitted for diagnostics at the National Veterinary Laboratory.
Control measures
Measures applied
  • Surveillance outside infected and/or protection zone
  • Surveillance within infected and/or protection zone
  • Vaccination permitted (if a vaccine exists)
  • No treatment of affected animals
Measures to be applied
  • Movement control inside the country
  • Emergency harvest
Diagnostic test results
Laboratory name and type Species Test Test date Result
Botswana National Veterinary Laboratory (National laboratory) Squicker (cynodontis species) histopathological examination Pending
Future Reporting
The event is continuing. Weekly follow-up reports will be submitted.
Map of outbreak locations