Get access to all handy features included in the IVIS website
- Get unlimited access to books, proceedings and journals.
- Get access to a global catalogue of meetings, on-site and online courses, webinars and educational videos.
- Bookmark your favorite articles in My Library for future reading.
- Save future meetings and courses in My Calendar and My e-Learning.
- Ask authors questions and read what others have to say.
Equine influenza - Current best protection
Get access to all handy features included in the IVIS website
- Get unlimited access to books, proceedings and journals.
- Get access to a global catalogue of meetings, on-site and online courses, webinars and educational videos.
- Bookmark your favorite articles in My Library for future reading.
- Save future meetings and courses in My Calendar and My e-Learning.
- Ask authors questions and read what others have to say.
Read
Summary
The equine influenza RNA orthomyxovirus (EIV) is highly contagious and has the potential to compromise the health of individual horses, disrupt equestrian events and the equine industry. It is endemic worldwide, with the exception of Iceland and New Zealand. After a large outbreak in 2007 (with around 75,000 horses infected and an estimated cost to the Australian economy of A$1 bn), Australia has also regained EIV-free status.
EIV does not normally circulate asymptomatically or persist in latent form. Outbreaks are usually caused by introduction of affected horses in a population that is insufficiently protected immunologically (either by natural exposure or vaccination) against the introduced strain of EIV. In contrast to other common equine pathogens, like Herpesviruses, S. equi or many parasites prevention of EIV is therefore relatively straightforward:
In endemic areas, sporadic outbreaks are best prevented 1) by appropriate vaccination of all equids in a population (except for horses that are completely isolated from others and foals < 4-6 months of age according to vaccine-specific recommendations) and 2) by only introducing new horses after quarantine of at least two weeks duration.
The office international des epizooties (OIE - World Organisation for Animal Health) regularly publishes important information on circulating strains worldwide and makes recommendations on vaccine strains composition. In accordance with the observations on circulating strains in recent years (see additional infos), these have been to include both clade 1 and clade 2 viruses of the Florida sublineage (H3N8), while it is deemed unnecessary to incorporate an H7N7 virus or an H3N8 virus of the Eurasian lineage.
Recombinant canarypox-based, ISCOM-adjuvanted vaccines and a modified-live cold-adapted equine vaccine, which is administered intranasally, are also reported to provide adequate protection. In contrast, the immunity provided by vaccination with some inactivated influenza vaccines can be short-lived, but all currently marketed EI vaccines should provide protection for at least six months.
Good concepts for optimal protection also include the identification and appropriate management of individuals and situations associated with an increased risk of infection with EIV: Besides low concentrations of HA-specific neutralizing antibody titers appropriate for the infectious strain (defining factors are time since last vaccination and a possible advantage with previous immunisations with different vaccines), age < 6 years and frequent changing contacts between large numbers of horses are risk factors.
In the face of an outbreak in an insufficiently protected population, at risk individuals and situations should be the first to receive attention regarding strategic vaccination plans. As illustrated in a very informative report describing the management of the 2007 EIV outbreak in Australia, the use of different vaccination strategies is well described (see also additional infos). These were very effectively implemented together with other measures, in particular restriction of movement of horses.
In conclusion, besides management measures including surveillance programs, quarantine, control and limitation of movement in the population, vaccination is the most effective tool to prevent, control, and limit the impact of equine influenza. Vaccination is central to achieve best protection against EIV.
Keywords: equine influenza virus, vaccination, protective measures
Evolution of EIV
Albeit at a lower rate of antigenic drift than human influenza pathogens, EIV is a constantly evolving virus. The H3N8 subtype (first observed in 1963: A/equine/2/Miami/63; H7N7 is considered extinct) has evolved into an Eurasian and American linage, of which the latter predominates in three distinct American sub-lineages, a South American lineage, a Kentucky lineage (also known as classic American lineage), and a Florida lineage further subdivided into clades 1 and 2.
Examples of different types of vaccination strategies:
- reactive and prophylactic ring vaccination around infected areas (10 km wide vaccination buffer zones)
- predictive vaccination (targeted horse populations posing strategic or economic risk to contribute to spread of the disease, such as Thoroughbred racehorses, competition horses, police horses, etc.)
- blanket vaccination (to maximise immunity in specific areas).
Vaccine development
While many vaccines still inappropriately contain an outdated strain composition, some vaccines have been updated and should be accordingly recommended. Some manufacturers have made important efforts to meet the OIE recommendations, as reported for the development of a recombinant canarypox-based EI vaccine’s mode of action and production.
Get access to all handy features included in the IVIS website
- Get unlimited access to books, proceedings and journals.
- Get access to a global catalogue of meetings, on-site and online courses, webinars and educational videos.
- Bookmark your favorite articles in My Library for future reading.
- Save future meetings and courses in My Calendar and My e-Learning.
- Ask authors questions and read what others have to say.
[1] AAEP Risk-Based Vaccination Guidelines > Equine Influenza https://aaep.org/guidelines/vaccination-guidelines/risk-based-vaccination-guidelines/equine-influenza
Comments (0)
Ask the author
0 comments