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Equine disease surveillance, July to September 2017
Summary of UK disease surveillance for the third quarter of 2017
Problems with the supply of equine viral arteritis vaccine
Update on diseases occurring in the UK since 1 October 2017
Focus on recent experience of disease control and clearance during an outbreak of neurological EHV-1 infection
UK disease surveillance: 1 July to 30 September 2017
The results of virological testing for July to September 2017 are summarised in Table 1 and include data relating to equine viral arteritis (EVA), equine infectious anaemia (EIA) and West Nile virus (WNV) from the APHA, Weybridge. The sample population for the APHA is different from that for the other contributing laboratories, as the APHA’s tests are principally in relation to international trade (EVA, EIA and WNV). The APHA also provides testing for WNV as part of clinical work up of neurological cases, to exclude infection, on specific request and provided the local regional APHA office has been informed.
No equine viral notifiable diseases were confirmed in the UK in the third quarter of 2017.
Equine herpesvirus EHV-4 respiratory disease
On 3 July 2017, a single case of equine herpesvirus type 4 (EHV-4) respiratory disease was confirmed among a group of 15 animals on a premises in Ayrshire. The affected animal was a non-vaccinated five-year-old cob gelding that presented with pyrexia, profuse nasal discharge and lymphadenopathy on 30 June.
On 18 July, a case of EHV-4 respiratory disease was confirmed on different premises in Ayrshire. The affected animal was a non-vaccinated 10-year-old Irish sport horse that presented with profuse serous nasal discharge and lymphadenopathy on 14 July, having been dull and lethargic one week before the onset of signs. This horse was in contact with six other animals that had shown signs of conjunctivitis.
On 25 July, a case of EHV-4 respiratory disease was confirmed on premises in West Yorkshire. The affected animal was a non-vaccinated yearling filly that presented with mucopurulent nasal discharge, inappetence and lymphadenopathy on 21 July. This horse was in contact with three other animals of which two had presented with profuse watery nasal discharge.
On 20 September, five cases of EHV-4 respiratory disease were confirmed on a stud premises in Hertfordshire. Four of these cases had coinfection with Streptococcus zooepidemicus and the affected animals were among a group of six that were not vaccinated and ranged in age between eight months and two years. Presenting clinical signs included coughing, nasal discharge, lymphadenopathy and pyrexia.
For all of the above cases, the positive diagnoses were confirmed by qPCR on nasopharyngeal swabs.
On 18 September 2017, a case of equine influenza (EI) with S zooepidemicus coinfection was confirmed on a premises in Northumberland. The affected animal was a six-year-old non-vaccinated Irish draft horse that had recently been imported and presented with nasal discharge and pyrexia before recovering. There were 20 other vaccinated animals on the premises, none of which showed clinical signs of respiratory disease.
The positive viral and bacterial diagnoses were confirmed by qPCR on a nasopharyngeal swab.
Surveillance for equine influenza
The Horserace Betting Levy Board (HBLB) equine influenza (EI) surveillance scheme has been set up to monitor genetic and antigenic changes in EI viruses circulating in the UK. The HBLB sponsorship enables free advice and diagnostic testing to be provided.
More information regarding EI, including details of the surveillance scheme, are available by e-mail to firstname.lastname@example.org or at www.equiflunet.org.uk
Outbreaks of EI are reported by Tell-Tail, the text alert service for UK equine practitioners sponsored by Merial Animal Health. This free service alerts practitioners to outbreaks of EI in the UK via text message. The service has recently been expanded to include notification of EHV-1 neurological disease and EHV-1 abortion.
Equine vets can sign up for this scheme by registering at www.merial.co.uk
A summary of the diagnostic bacteriology testing undertaken by different contributing laboratories is presented in Table 2. For contagious equine metritis (CEM), all 23 Horserace Betting Levy Board (HBLB)-approved laboratories in the UK contributed data.
Interruption to the supply of equine viral arteritis vaccine
Veterinary vaccine manufacturer Zoetis has warned of supply problems with its equine viral arteritis vaccine Equip Artervac, which will lead to an as yet undetermined interval in supply; the final available batch expired on 26 November 2017. This will result in vaccinated stallions and teasers effectively ‘lapsing’ six months after their last vaccination if Equip Artervac is not available for the next recommended six-monthly booster dose.
Attending veterinary surgeons will need evidence to satisfy them that lapsed vaccinated stallions and teasers were seronegative before first vaccination (recorded in the horse passport) and that post-vaccination seropositivity, when lapsed, is associated with vaccination and not due to possible challenge by equine arteritis virus (EAV) infection. Suspicion of challenge by EAV infection would require notification to Defra/APHA under the terms of the Equine Viral Arteritis Order 1995, with the stallion/teaser being officially investigated to determine whether it is shedding EAV in its semen.
It is recommended that, in addition to routine annual Code of Practice blood sampling, serial blood samples (clotted blood) are collected from vaccinated stallions during the period when Equip Artervac vaccine is not available and that the separated sera from these samples are tested alongside each other once it becomes clear that Equip Artervac will be available again. Results that show evidence of stable/declining virus neutralising antibody levels (VN antibody titres) against the virus during the period without vaccination should be considered consistent with absence of exposure to EAV infection during that period.
For stallions and teasers that were vaccinated in November 2017, the routine January 2018 blood sample should represent the approximate peak post-vaccine VN antibody response from which subsequent antibody levels would follow and be able to be assessed as stable/declining. It is suggested that further samples are taken at approximately six-month intervals thereafter until Equip Artervac is available again. When the vaccine is available again, a final blood sample should be taken at the same time that the stallion resumes vaccination.
In order to assist with careful collation of serum samples, the AHT has agreed that it will receive, process and store serial samples from stallions as part of this scheme. All samples need to be clearly labelled with the name of the stallion, the stud farm and/or owner, the date that the sample was collected and the name of the veterinary surgeon and practice that collected it. Samples should be submitted to the AHT using a dedicated submission form specifically designed for this purpose and which can be printed as required (download from www.aht.org.uk/skins/Default/pdfs/Artervac_Form_v2.pdf). Dates of vaccination must be recorded in horse passports.
Stallions ‘shuttling’ to the 2017/18 and 2018/19 southern hemisphere seasons will have further issues regarding ‘lapsed’ vaccinations and it is recommended that stallion owners and managers discuss with their veterinary surgeons the specific implications on the basis of individual stallions’ circumstances. These issues are more difficult to predict and resolve as government-to-government discussions may be required with individual countries involved and it is currently not possible to confirm if or when this might happen.
No equine bacterial notifiable diseases were confirmed in the UK during the third quarter of 2017.
APHA Salmonella results
Four samples were submitted to the APHA in the third quarter of 2017 and all were positive for Salmonella. From the incidents involving isolates typed by the APHA, the serovars/phagetypes reported were Salmonella Typhimurium (two samples; both DT40), Salmonella Agama (one sample) and Salmonella Newport (one sample – fully sensitive). S Typhimurium DT40 is likely to originate from wild birds and S Newport and S Agama are often associated with badgers.
More information about Salmonella in livestock in Great Britain is available at www.gov.uk/government/publications/salmonella-in-livestock-production-in-great-britain-2015.
Toxicology and parasitology
A summary of diagnostic toxicosis and parasitology testing undertaken by contributing laboratories is presented in Tables 3 and 4, respectively. Results for toxicosis are based on histopathologically confirmed evidence of disease only (where applicable).
Grass sickness surveillance data
The nationwide equine grass sickness (EGS) surveillance scheme (www.equinegrasssickness.co.uk) was established in spring 2008 to facilitate the investigation of changes in geographical distribution and incidence of the disease in Great Britain. Data gathered by this scheme are collated in a strictly confidential database. The surveillance scheme receives data from a wider population than the data presented in Table 3; different diagnostic criteria are also used.
Ten cases of EGS were reported during the third quarter of 2017, of which four occurred during July, five in August and one in September. Eight cases were reported in England and two in Scotland. Of the 10 cases, six premises reported a prior history of EGS.
The cases comprised three geldings/stallions and seven mares/fillies, with a median age of 8.5 years (range 2 to 21 years). Affected breeds were warmbloods (n=2), cob/cob cross (n=3) and crossbreeds (n=4). One horse’s breed was not reported.
Of the 10 cases, three were diagnosed with acute EGS, five were diagnosed with subacute EGS and two were diagnosed with chronic EGS (both surviving to date).
Diagnostic information was provided for all reported cases, of which the majority (nine) were diagnosed based on veterinary assessment of clinical signs alone. Two cases underwent a laparotomy; only one case was reported to be confirmed via histopathological examinations of an ileal biopsy sample.
National disease occurrence since 1 October 2017
EHV-4 respiratory disease
The AHT confirmed two separate cases of EHV-4 respiratory disease, one in Wales and the other in England. The positive diagnoses were confirmed by qPCR on nasopharyngeal swabs.
The AHT confirmed a single case of EI in a horse of unknown vaccination status in south-east England. The positive diagnosis was confirmed by qPCR on a nasopharyngeal swab.
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