Jamie qualified from Liverpool University in 2009 and after a spell in mixed large animal practice in Yorkshire obtained an internship at Rossdales Equine Hospital in Newmarket. He then moved to southern California for a residency at the Davis school. In 2015 he passed the examinations to become a diplomat of the American College of Veterinary Internal Medicine. It’s quite an incredible success story in just seven years from qualifying and since 2015 he has built on this by becoming a member of the team at Liphook Equine Hospital

This veterinary webinar covers the following: 

  • Testing modalities, Vaccination, Treatment
  • Equine Herpes Virus I How to test in an outbreak, How to release an outbreak, How to treat cases, Should we vaccinate?
  • Equine Influenza What are the vaccination rules currently?
  • Borrelia burgdorferi A few comments (as it is one of Jamie’s interests)

He begins by revising the epidemiology of strangles noting that young horses between the ages of 1-5 years are most commonly affected. The disease is spread by aerosol from sick horses up to 10 m., from direct or indirect contact with discharges from sick horses and from the environment (variable survival). The incubation period is 2-10 days.

Three Strep equi equi complications are listed with a brief description of each. These are metastatic strangles, purpura hemorrhagica and dysphagia. A slide lists the HBLB Guidelines to be followed in the event of an outbreak.

The diagnosis is important for three reasons: 

  • In early suspected cases to establish if strangles is the cause of the disease. 3-600 reported cases per year in the UK
  • After apparent recovery. To establish horses are no longer contagious
  • Screening new cases. To identify carrier horses

For early suspected cases nasopharyngeal lavage is the most accurate method. A comparison of the pros and cons of culture and PCR testing is summarised but also noting that many cases are mild, making diagnosis difficult. By reference to historical data and more recent research Jamie concludes that serological testing for carrier status is pointless. Serological testing may be of use in an outbreak with paired serology testing showing a rising titre, but there is no correlation with carrier status. There are two serological tests available and the merits of each is described referencing recent unpublished work.

There is information on a new vaccination product, for which there appears to be some concerns such as frequency of boosters, a range of adverse reactions and a lack of complete resolution of signs. An interesting study details the survival of live strep equi cultures placed on various surfaces comparing winter and summer.

There is no evidence of antibiotic resistance currently, although potentially resistance to penicillin, currently the antibiotic of choice, is considered a risk. One study showed vancomycin resistance. This is a protected antibiotic and should not be used under any circumstances.

The Stereotypical and Neurological signs of Equine Herpes Virus-I are listed for revision, noting that latent infection is thought to be in 80-90% of the population.  Emphasis is placed on Equine Herpes Myeloencephalopathy (EHM). Risk factors for this include older that 20 years, seasonality (autumn, winter and spring), high temperature, new horses in the herd, and with stress and immune status as possible risk factors. Factors affecting the pathogenesis, virulence of a particular strain and the infectious dose, for example, are fully discussed. There is limited information on how far the virus spreads, with one article in 2009 suggesting 14.5 m. Smear spread is the most effective means of spread and also via fomites.

For diagnosis a nasal rather than nasopharyngeal swab +PCR is recommended. Serology is excellent to show seroconversion and therefore exposure, but ‘relatively pointless’ in an individual sample. There is considerable debate and conclusions on testing to remove restrictions described as difficult to decide and depending on context. Information is provided by reference to a French team in an outbreak in Valencia. There is even more debate on vaccination including the results of a round table discussion on the merits or otherwise of this, but the consensus was that vaccination is fundamental to control with biosecurity minimising spread and impact. A slide summarises treatment with NSAIDS, corticosteroids, acyclovir, valocyclovir, low molecular weight heparin and aspirin.

In the section on Equine Influenza a comparison is made between the years 2019, 2020 and 2021showing a huge reduction in cases in 2020 with only 6 distinct foci. In 2021 this increased to 36 confirmed cases and 77% of foci reported a new arrival –often from Europe. The clinical signs are not listed as Jamie assumes that these are familiar to equine colleagues. For diagnosis, noting that the incubation period is only 1-3 days, the following is suggested:

  • Serology-paired titre
  • Isolation of virus by nasopharyngeal swab within 3-5 days of clinical signs
  • Virus isolation

There is a slide showing the subtypes of equine influenza, which leads into a detailed discussion of current vaccination guidelines and new research including the possibility of a zoonotic threat. Vaccination levels in the UK are currently inadequate to offer herd protection.

Borrelia burgdoferi, the cause of Lyme disease is the last condition discussed in this thoughtful and well-researched webinar. In the UK 2.5-5.1% of ticks are known to be infected, with human cases on the increase. The rate of infection in horses is not known. The signs of Lyme disease in this species are:

  • Stiffness/lameness
  • Myalgia/hyperaesthesia
  • Changes in behaviour
  • Neurological signs
  • Uveitis (2 reports)
  • Pseudolymphoma- a case report in 2011
  • Nuchal bursitis reported in 2021
  • Often co-infected with Anaplasma phagocytophila

Serology has a poor specificity with 60% false positives. There is a discussion on how we can improve diagnostics comparing C6 Elisa and Cornell Multiplex. To add to potential confusion, however, ACVIM guidelines recommend that if you are in a prevalent area don’t test serologically.  

For treatment there is a discussion on the use of oxytetracycline, doxycycline and minocycline with dose information for each. Metronidazole gets a mention but with a question mark beside it. Treatment duration has not been adequately defined but possibly one week in acute cases and one month in chronic cases.

These are the conclusions in summary:

  • The diagnosis is more complex than it should be. Vaccination might help but we are not there yet. Understanding the pathogenesis stops the disease
  • EHV Diagnosis can be easy. Releasing from isolation is more difficult

Vaccination may help.

  • Influenza Diagnosis is easy. Vaccination is essential to reduce the disease rate
  • Lyme disease Don’t over diagnose. Care with treatment

Jamie Prutton’s experience and extensive post-graduate training shines throughout this webinar. It will benefit all colleagues, vets, nurses and students with an interest in equine medicine