Disease Information
15 December 2000
Vol. 13 - No. 49
FOOT AND MOUTH DISEASE IN SOUTH AFRICA
Virus SAT 1 (Follow-up report No. 1)
See also: 15 December 2000, 8 December 2000, 27 October 2000, 13 October 2000, 6 October 2000, 29 September 2000, 22 September 2000, 15 September 2000
Text of an e-mail received on 14 December 2000 from Dr Emily Mmamakgaba Mogajane, Chief Director, Agricultural Production, National Department of Agriculture, Pretoria:
End of previous report period: 30 November 2000 (see Disease Information, 13 [48], 221, dated 8 December 2000).
End of this report period: 11 December 2000.
The foot and mouth disease (FMD) outbreak in a feedlot ("Arendsfontein") in the Middelburg District of Mpumalanga Province, which was reported on 30 November 2000, is still contained on the feedlot where it was detected and has not spread to any other property.
The infected area of the feedlot is 275 hectares (ha) in size, the quarantine area around this is 31,632 ha, with a further surveillance area of 96,911 ha surrounding the feedlot.
Updated data on the number of animals in the outbreak:
species susceptible cases deaths destroyed slaughtered bov 14,308* 740 0 0 0 ovi 2,445* 0 0 0 0 sui 48,720* 0 0 0 0
* Figures given in the emergency report (30 November 2000) were estimates. The figures stated here are the correct ones.
Epidemiology :
A. Source of agent / origin of infection: virus sequencing results show that the virus topotype closely resembles the serotype of SAT 1 virus that occurs in African buffalo in the southern part of the Kruger National Park (KNP), which falls within the FMD infected zone of South Africa. It is suspected that the infection was brought into the feedlot from the Lowveld area. The mode of introduction is still being investigated.
B. Mode of spread: suspected contact with infected animal(s) introduced into the feedlot.
C. Other epidemiological details: follow-up and trace-back actions carried out immediately revealed no spread of the infection from the feedlot. A total of 3.1 million cattle, 2,073 sheep, 730,393 pigs, 302 goats have been inspected on farms outside the infected farm, with 2,326 serum samples and 23 tissue samples submitted for further testing - all with negative results. The total number of farm visits to date is 466, with 398 herds. The follow-up and trace-back also included visits to abattoirs - all with negative results.
Control measures during reporting period:
A. In the affected area:
- Control measures at the affected feedlot include strict movement control of animals within the feedlot, disinfection, showering in and out and separate, dedicated work teams for the different areas within the feedlot.
- The emergency vaccination programme instituted at the feedlot, with the aim of minimising virus excretion by the cattle, has been completed. All cattle in the feedlot were vaccinated with a trivalent FMD serotype SAT 1, 2 and 3 vaccine, on 1, 2 or 3 December.
The sheep in the feedlot were vaccinated on 4 December, and the veld cattle on Arendsfontein on 4 and 5 December. All the veld cattle on Arendsfontein have been moved into the feedlot and will ultimately be slaughtered, as will all the cattle in the feedlot. All the cattle (14,308) will be re-vaccinated 14 days later. All 48,720 pigs at the feedlot were vaccinated with oil-adjuvant FMD serotype SAT 1 vaccine. This vaccination began on 8 December and was completed on 9 December.
B. Around the affected area:
- Strict movement control has been instituted. A number of farms around Arendsfontein farm have been placed under quarantine. Any movement of animals and animal products into, within and out of the control area around this outbreak is under strict veterinary permit control.
- Surveillance of cloven-hoofed animals in the Middelburg District of Mpumalanga is continuing (in the infected, quarantine, surveillance and open areas). So far, all results have been negative for FMD.
C. In the Lowveld (Lowlands):
- A number of farms in the Lowveld, from where cattle were sourced to go to the affected feedlot, were placed under immediate quarantine as a precautionary measure and follow-up investigations were instituted. A total of 25 farms were placed under quarantine; 5,454 cattle were inspected, of which 2,054 were mouthed; 662 serum samples and 15 epithelium samples were also taken from these animals. The results of all probang, serum and epithelium samples taken were negative.
- Continuing surveillance is occurring in this area, which entails the inspection and sampling of farms in the areas of White River, Nelspruit and Barberton Districts. The current seven-day inspections in the redline area (enzootic zone) of Nsikazi are being intensified and samples taken of any suspect animals. Inspections of diptanks in the Nkomazi area will continue.
The State Veterinarian in Skukuza, KNP, will start FMD surveillance in impala in the southern part of the KNP bordering the Crocodile River. This is to find out if any FMD infection of impala can be found.
- No movements of cloven-hoofed animals are allowed in the redline area of Nsikazi and the Onderberg or in the surveillance area of the Nelspruit and Nkomazi SV areas. Only meat originating from registered abattoirs will be allowed into the Onderberg area.
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FOOT AND MOUTH DISEASE IN SOUTH AFRICA
Virus O (Follow-up report No. 5)
See also: 15 December 2000, 8 December 2000, 27 October 2000, 13 October 2000, 6 October 2000, 29 September 2000, 22 September 2000, 15 September 2000
Text of an e-mail received on 10 December 2000 from Dr Emily Mmamakgaba Mogajane, Chief Director, Agricultural Production, National Department of Agriculture, Pretoria:
End of previous report period: 25 October 2000 (see Disease Information, 13 [42], 188, dated 27 October 2000).
End of this report period: 9 December 2000.
On 8 November 2000, 4 positive serological results, without evidence of clinical signs, were obtained using the liquid phase blocking ELISA (LPBE) test for foot and mouth disease (FMD) virus serotype O (log titres equal to or greater than 1.6).
The test was conducted on 24 sera from cattle at a dipping tank at 29º 38' 46.5'' S - 30º 44' 39.5'' E. The dipping tank is outside the 10-km-radius quarantine zone but within the surrounding 20-km surveillance zone. This was the result of intensive surveillance in the FMD surveillance area in KwaZulu-Natal.
The LPBE tests were repeated and the results were confirmed. No clinical signs of the disease were seen. As the LPBE sometimes gives false-positive results, all such tests are repeated using the virus neutralisation test (VNT).
The VNT on the 4 sera concerned proved negative (log titres equal to or less than 1.3). The VNT was repeated and the results were inconclusive.
The sera were then tested using 3ABC ELISA, which detects antigens produced during virus replication. These results were negative.
A further 108 serum samples were collected on 11 November from cattle at this dipping tank.
Immediate actions had to be taken in the light of the initial LPBE results:
- The area under suspicion made the rationale to continue with a stamping-out policy questionable and it was therefore decided to abandon the stamping-out policy and apply limited vaccination within a radius of 15 km.
- The FMD control area was enlarged to a 40-km-radius zone as a precautionary measure, with strict control on the movement of animals and animal products into, out of and within this control area.
Meanwhile, the LPBE tests performed on the 108 sera from the cattle at the dipping tank in question were negative. For confirmation of these results, the sera (108 samples plus the original 23 serum samples that remained from this dipping tank) were sent to the OIE World Reference Laboratory for FMD (Pirbright, United Kingdom) on 16 November. The Pirbright Laboratory found 18 animals positive, 57 animals weakly positive and 53 animals negative on LPBE. For confirmation, they tested the positive cases using the VNT and found all animals to be negative. They also used the 3ABC ELISA to confirm 28 of the sera as negative. The final results from Pirbright were received on 30 November.
Conclusion
The conclusion is therefore that these cattle were not infected with FMD. Further intensive sero-surveillance data and clinical inspection indicate that the disease has not spread outside the 30-km new surveillance zone. In view of these results, and the fact that it is now more than 30 days since the last positive FMD case, the Cabinet has decided to reduce the control area to the original 30-km-radius zone.
Vaccination and intensive surveillance around the original epicentre will continue and will cover a radius of about 10 to 15 km.
Intensive sero-surveillance will continue throughout the 30-km-radius control area.
Surveillance and vaccination data up to 6 December 2000
Total number of animals inspected Number of animals tested serologically No. of animals vaccinated cattle 156,075 7,566 6,003 sheep 2,999 786 720 goats 8,124 902 555 pigs 148,921 1,056 cloven-hoofed game animals 10 45
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