Disease control EBL Eradication Scheme

Transcription

1 Disease control EBL Eradication Scheme 6. Disease control A. New Zealand dairy herd Enzootic Bovine Leucosis (EBL) control scheme The New Zealand dairy industry enzootic bovine leucosis (EBL) control scheme continues to be funded by Dairy InSight via product levies. Livestock Improvement administers the scheme and testing is carried out at its ISO accredited Animal Health Laboratory. As a condition of supply to the dairy companies, herd owners are required to have their herds EBL tested and to cull any EBL positive reactors. NZ dairy herd EBL status 70% of all New Zealand dairy herds (about 8500) were tested for EBL in the course of the season In the course of 2004/05, four new EBL positive herds were identified by routine testing and subsequent investigation Five new EBL infected cows confirmed on testing in the four incident herds One EBL positive herd remained at the end of 2004/5 season At the beginning of the EBL scheme, point prevalence peaked at 6.3% (928 herds) in For the last three seasons the annual prevalence of confirmed blood test positive herds has dropped below 1% of the national herd with the point prevalence in May 2005 falling to below 0.01% or one herd. The EBL test positive animal in this herd has been culled and the herd is awaiting retest after a 60-day post-cull isolation phase. 42 Incident herds 1 Routine EBL testing during the 2004/05 season suggested that seven herds, previously EBL test negative, were harbouring EBL infection. However, additional confirmatory tests and investigation of the herd/cow history suggest that in three herds the reactor cow was a false positive case. Only four incident herds appear to have been true EBL cases. One herd had two EBL cows, while a single infected cow was found in each of the remaining three herds. Every incident herd is also subjected to an epidemiological investigation to trace and prevent the possible spread of infection. Two of the confirmed incident herds are high-risk herds with recent history of EBL infection. These herds had just reached provisionally negative status in 2003/04 after culling all known EBL infected animals. One other herd has previously harboured EBL; the index cow in this case was identified as an EBL infected calf in 2002, but had not been slaughtered at the time and reintroduced into the herd. The remaining herd had no history of EBL and was previously EBL free. However the index cow was purchased from the same source (and belonged to the same age cohort) as 10 of 13 EBL reactors in a 2003/04 incident herd with an EBL outbreak. While the original source herd had been EBL free with good test history until it closed in 2003, the link strongly suggests a common source. Fine-tuning At the start of the 2004/05 season, screening test cut-offs were generally adjusted downward to maximise test sensitivity, while an additional confirmatory test has been introduced to guard against false positive cases. 50% of all EBL free herds continue to be screened annually using pooled or vat milk samples. Both annual EBL herd prevalence and incidence are now well below 0.2 %. EBL freedom according to international animal health standard requires that 99.8% of herds be free of EBL for two or more years. The New Zealand dairy herd, therefore, is set to reach this target in the 2005/06 season. To achieve country freedom, EBL in the beef industry will now need to be assessed and controlled if present. 1 Herds previously classified EBL negative with newly identified EBL infected animal.

2 Disease control Tb Control B. Tuberculosis (Tb) control Control of Tb (M. bovis) over the agricultural industry is managed by the Animal Health Board whose primary objective is to manage Tb to reduce the number of infected herds and to prevent Tb vector free areas becoming vector risk areas. The status of a vector area is determined by the prevalence of wild animals that are considered a source of infection (e.g., possums and ferrets). Table 6.1: Tuberculosis (Tb) testing and results in 2004/05 Region Vector Status Number of Number of Number of infected dairy herds dairy cattle Tuberculous a June 2005 primary tested dairy cattle Northland Free 0 91,972 0 Auckland Free 0 45,035 0 Risk 0 1,304 0 Waikato Free 2 1,000, Risk 3 228, Bay of Plenty Free 0 77,047 0 Risk 0 13,516 0 Gisborne Free Hawkes Bay Free 0 15,797 0 Risk 1 21,058 3 Taranaki Free 0 143,698 0 Manawatu / Wanganui Free 2 133,784 1 Risk 2 66,297 4 Wellington Risk 6 103, North Island Free 4 1,507, Risk , North Island Total 16 1,941, Nelson / Marlborough Free 2 73,331 2 Risk 1 16,817 2 West Coast Free 0 10,469 2 Risk , Canterbury Free 2 264,244 2 Risk 1 106,275 7 Otago Free 0 92,917 2 Risk 1 125,203 1 Southland Free 2 150,335 2 Risk 2 115,015 3 South Island Free 6 591, Risk , South Island Total 44 1,145, New Zealand Free 10 2,098, Risk , New Zealand Total 60 3,087, Sourced from Animal Health Board Annual Report for the year ending 30 June 2005 a Tuberculous Animals include lesioned reactor cattle and lesioned cull cattle

3 Appendix 1 Appendix 1 Farming regions and districts The following map shows the six Livestock Improvement Corporation Limited regions and the farming regions used in all analyses presented in this report. The list of districts, which follow local authority boundaries, within each region is also given Northland Far North Whangarei Kaipara 2 Central Auckland Rodney North Shore Waitakere Auckland Manukau Papakura Franklin 3 South Auckland Thames/Coromandel Hauraki Waikato Matamata/Piako Hamilton Waipa Otorohanga South Waikato 4 Bay of Plenty Western Bay of Plenty Tauranga Whakatane Kawerau Opotiki 5 Central Plateau Rotorua Taupo 6 Western Uplands Waitomo Ruapehu 7 East Coast Gisborne Wairoa 8 Hawkes Bay Hastings Napier Central Hawkes Bay 9 Taranaki New Plymouth Stratford South Taranaki 10 Wellington Wanganui Rangitikei Manawatu Palmerston North Horowhenua Kapiti Porirua Upper Hutt Lower Hutt Wellington 11 Wairarapa Tararua Masterton Carterton South Wairarapa 12 Nelson/Marlborough Tasman Nelson Marlborough Kaikoura 13 West Coast Buller Grey Westland 14 North Canterbury Hurunui Waimakariri Christchurch Banks Peninsula Selwyn Ashburton South Canterbury Timaru MacKenzie Waimate 16 Otago Waitaki Central Otago Queenstown/Lakes Dunedin Clutha 17 Southland Southland Gore Invercargill Northland Auckland Bay of Plenty / East Coast Taranaki Wellington / Hawkes Bay South Island

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