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LSD symposium - J. Chan - Lumpy skin disease in Hong Kong
Dr. Jason Chan presented on the outbreak of Lumpy Skin Disease (LSD) in feral cattle populations in Hong Kong from 2020-2021. The key points were: 1) The initial outbreak was reported in October 2020 across multiple country parks. Disease investigation found that 72% of cattle in one herd showed skin lesions and 84% were seropositive. 2) By March 2021, no new clinical cases were reported. Surveillance since found 14 juveniles seronegative, suggesting LSD may have disappeared due to lack of susceptible newborn cattle. 3) Continued clinical and serological surveillance is important since Hong Kong has a small teaching farm. No urgency exists currently to declare freedom
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LSD symposium - J. Chan - Lumpy skin disease in Hong Kong
- 1. Lumpy Skin DiseaseSymposium in Rome, Italy (14-16 March 2023) Lumpy Skin Disease in Hong Kong Dr. Jason Chan Veterinary Officer (Stray Cattle Management) Agriculture, Fisheries and Conservation Department The Government of HKSAR, China
- 2. Lumpy Skin DiseaseSymposium in Rome, Italy (14-16 March 2023) Contents 1. Background information 2. Time course of initial outbreak 3. Disease investigation 4. Disease control and surveillance
- 3. Lumpy Skin DiseaseSymposium in Rome, Italy (14-16 March 2023) Background information No Commercial cattle farms in Hong Kong Two types of bovine species in Hong Kong – Brown Cattle (local Chinese breed) and Asian Water Buffaloes (Bubalus bubalis) All feral, living in the wild Staying in the country park areas but do accidentally venture into urban areas Believed to be a signature of many country parks in Hong Kong – they shall be protected and conserved
- 4. Lumpy Skin DiseaseSymposium in Rome, Italy (14-16 March 2023) Background information – number and distribution Source: AFCD cattle/ buffalo population survey Population survey in 2022 - 860 brown cattle and 180 buffaloes Central New Territories (Tai Mo Shan, Shing Mun, Tai Lam) Cattle Buffalo 240 55 Northeast New Territories (Sha Tau Kok, Plover Cove) Cattle 120 Lantau Island Cattle Buffalo 120 125 Sai Kung Cattle 380
- 5. Lumpy Skin DiseaseSymposium in Rome, Italy (14-16 March 2023) Time course of initial outbreak in brown cattle 27km 25km 36km 9/11/2020 ➢ Lam Tsuen Country Park ➢ Seen cattle with skin lesions during operation 20/10/2020 ➢ Government Operation Centre ➢ First cow in the Centre 4/10/2020 ➢ Sai Kung Country Park ➢ First ever report by public – cattle with skin lesions 2/11/2020 ➢ Lantau Island ➢ Reported by public – cattle with skin lesions 30/10/2020 ➢ Two cattle were euthanised ➢ Post-mortem at Government Vet Lab
- 6. Lumpy Skin DiseaseSymposium in Rome, Italy (14-16 March 2023) Disease investigation – pathological findings Enlarged prescapular lymph node Histopathology: Virus inclusion TEM: Poxvirus virions Source: Tse A.C. et al. (2022). Lumpy Skin Disease in a Cow. Brazilian Journal of Veterinary Pathology, 15(2), pp. 114 – 117.
- 7. Lumpy Skin DiseaseSymposium in Rome, Italy (14-16 March 2023) Disease investigation Two different herds were sampled All the cattle in each herd have similar epidemiological risk Always together in a set territory Seldom mix with other herds These two herds were chosen because: Less timid and more docile Can be attracted through giving hay ➢ Mui Wo - 25 cattle ➢ Lantau Island (Southwest border of Hong Kong) ➢ Pak Lap - 31 cattle ➢ Sai Kung Country Park (Eastern border of Hong Kong)
- 8. Lumpy Skin DiseaseSymposium in Rome, Italy (14-16 March 2023) Disease investigation Mui Wo Herd, Lantau Island (Southwest border of Hong Kong) First report received on 2/11/2020 Sampling period: 20/1/2021 – 2/3/2021 25 cattle in total 4/25 were seronegative (16%) (but 2 with skin lesions <50%>) 21/25 were seropositive (84%) 5 out of these 21 seropositive > generalised skin lesions (23.8%) 11 out of these 21 seropositive > mild skin lesions (52.4%) 5 out of these 21 seropositive > no skin lesions (23.8%)
- 9. Lumpy Skin DiseaseSymposium in Rome, Italy (14-16 March 2023) Disease investigation Pak Lap Herd, Sai Kung Country Park (Eastern border of Hong Kong) First report received on 4/10/2020 Sampling period: 1/2/2021 – 26/4/2021 31 cattle in total 13/31 seronegative (42%) (but 7 with skin lesions <54%>) 18/31 seropositive (58%) 5 out of these 18 seropositive > generalised skin lesions (27.8%) 5 out of these 18 seropositive > mild skin lesions (27.8%) 8 out of these 18 seropositive > no skin lesions (44.4%)
- 10. Lumpy Skin DiseaseSymposium in Rome, Italy (14-16 March 2023) Disease investigation In summary: As high as 72% of cattle in a herd showed suspicious skin lesions As high as 84% of cattle in a herd were seropositive Comparing clinical surveillance findings with serological testing results: Up to 72% of cattle in a herd having both testing results in line with each other The consistency dropped over the course of disease outbreak (skin lesions might have healed or become less obvious; antibody level might have dropped) Clinical surveillance assisted by public members Many public members concern about animal welfare in Hong Kong – they wanted those skin lesions to be treated The government only a phone call away Most initial disease outbreak reports in October and November 2020 were lodged by public members
- 11. Lumpy Skin DiseaseSymposium in Rome, Italy (14-16 March 2023) Disease investigation Last report by public members in March 2021 No suspicious cases after March 2021 Water buffaloes in Hong Kong seemed to be unaffected, both clinically and serologically
- 12. Lumpy Skin DiseaseSymposium in Rome, Italy (14-16 March 2023) Disease control and surveillance Was disease control possible in the feral cattle population? Vaccination Movement control and zoning Vector control Stamping-out Fortunately, natural herd immunity seemed to build up No clinical cases since March 2021 Affected animals recovered Unfortunately not Not feasible Not feasible Not feasible Practically feasible, but public perceptions are of major concern
- 13. Lumpy Skin DiseaseSymposium in Rome, Italy (14-16 March 2023) Disease control and surveillance Clinical surveillance During our population control program Animal welfare groups Public members Serological surveillance Purpose: to see if LSD is still present in the feral population Sampling target: all the cattle that were born after March 2021 (just less than 2 years old) but older than 3 months old Sampling period: started after October 2022 Target sample size vs convenient sampling
- 14. Lumpy Skin DiseaseSymposium in Rome, Italy (14-16 March 2023) Disease control and surveillance Serological surveillance: target sample size vs convenient sampling To calculate a target sample size: Estimated population of calves and juveniles: 120 (Population survey in 2022) ELISA sensitivity: 80 – 98.6% (ESFA, 2018; ESFA, 2020; Ibrahim A.I. et al., 2022 ) Design prevalence: 3.5% (ESFA, 2018) Sample size: 64 - 79 (RiBess+) Convenient sampling: so far 14 calves/juveniles sampled (all without any clinical signs and all seronegative) Unable to sample 64 - 79 calves/juveniles within a short period
- 15. Lumpy Skin DiseaseSymposium in Rome, Italy (14-16 March 2023) In summary…… 1. Has LSD disappeared in Hong Kong? Not many newborns? Calves and Juveniles only about 10% of the population > no susceptible animals before the disease dies out > breaks the transmission cycle??? Continue to perform both clinical surveillance and serological surveillance through convenient sampling 2. Fortunately, no urgency to declare “freedom of disease” No commercial cattle farms in Hong Kong No cattle exports Closest commercial cattle farm is about 430 km away 3. Having said that, one farm is being set up in Hong Kong An university teaching farm Vaccination program and movement control are in place
- 16. Lumpy Skin DiseaseSymposium in Rome, Italy (14-16 March 2023) References EFSA (European Food Safety Authority), Calistri P, DeClercq K, De Vleeschauwer A, Gubbins S, Klement E, Stegeman A, Cortinas Abrahantes J, Antoniou S-E, Broglia A and Gogin A, 2018. Scientific report on lumpy skin disease: scientific and technical assistance on control and surveillance activities. EFSA Journal 2018;16(10):5452, 46 pp. https://doi.org/10.2903/j.efsa.2018.5452 EFSA (European Food Safety Authority), Calistri P, De Clercq K, Gubbins S, Klement E, Stegeman A, Cortinas Abrahantes J, Marojevic D, Antoniou SE and Broglia A, 2020. Scientific report on the lumpy skin disease epidemiological report IV: data collection and analysis. EFSA Journal 2020;18(2):6010, 36 pp. https://doi.org/10.2903/j.efsa.2020.6010 Ibrahim A.I. et al. (2022). Serodiagnosis of Lumpy Skin Disease Using Sheep Pox Virus Compared to a Commercial ELISA Kit. Journal of Applied Veterinary Sciences, 7(1), pp. 46- 52.
- 17. Lumpy Skin DiseaseSymposium in Rome, Italy (14-16 March 2023) Any questions?