Pfizer Equivac S

Equivac S horse vaccine is a cell free extract of the Streptococcus equi organism used in the control of strangles.

Equivac S is of value only in the control of infection due to Streptococcus equi. By maintaining a regular vaccination program animals will retain a high level of circulating antibodies which will reduce the likeihood of a strangles outreak occurring.

Equivac S comes in a prefilled syringe. Vaccination against strangles should be included as a part of every horse’s vaccination program.

Indications for Use:
Strangles is a highly infectious disease of horses.  Typically, outbreaks occur when numbers of susceptible horses are brought together.  The disease is caused by Streptococcus equi and is characterised by purulent nasal discharge and by abscess formation in lymph nodes.  The sub-mandibular lymph nodes are most commonly affected but the infection may extend throughout the body.

Streptococcus equi may occasionally cause nasal discharge without swelling of the lymph nodes and sub-clinical infections may also occur.  Nasal discharge may also be caused by other organisms, notably Streptococcus zooepidemicus.  Other diseases may therefore be confused with strangles.  It must be emphasised that Equivac S is of value only in the control of infection caused by Streptococcus equi.

Directions for Use:
Occasional reports of local reactions to vaccination have been received.  On rare occasions, systemic signs have been observed.  This appears to occur when horses have been sensitised to Streptococcus equi by exposure to infection, or when they are incubating the disease.  Horses which show an abnormally severe reaction following vaccination should not receive further doses of the vaccine for 12 months.  Local reactions are more evident if the vaccine is injected subcutaneously.  Provided the injection has been carried out aseptically, any swelling which occurs at the site of innoculation should disappear in a few days.

The vaccine is injected intramuscularly.  The most convenient site for injection is the centre of the side of the neck.  Before the vaccine is injected, the proposed site of innoculation on the animal’s skin may be cleaned by swabbing with cotton-wool soaked in a suitable antiseptic solution such as methylated spirits.

When horses and foals are vaccinated against strangles for the first time, a course of 3 doses each of 1mL of Equivac S should be given with an interval of not less than 2 weeks between each dose. 

As artificial immunity has been shown to wane significantly towards the end of the year of vaccination, all horses should receive annual booster doses of 1mL.

Increased protection should be obtainable by administering booster doses more frequently, and six-monthly revaccination should be considered where the risk of infection is high.

Control of the disease:
It is strongly recommended that all horses should be included in a regular program of vaccination.  Foals should receive a primary course of vaccination (3 doses) commencing as soon as possible after the age of 3 months, and the resultant antibody response should be maintained by regular booster doses.

It is particularly important that booster doses should be given prior to periods of greatest risk of infection, such as the breeding season.  Pregnant mares may be vaccinated up to 2 weeks before foaling.

The objective in carrying out a regular programme of vaccination is to maintain a high level of antibodies to strangles in the blood of all horses in the herd or group, with a view to preventing the onset of an outbreak of strangles.  Field experience has confirmed that control of the disease can be achieved using these means.  Nevertheless, breakdowns do occur, usually under conditions where vaccinated animals are exposed to an outbreak of the disease and the challenge to immunity is great.  It is not claimed that Equivac S is an absolute preventative.

The presence of other infectious diseases, parasitic infections, nutritional disorders, immunological deficiencies and poor management practices may reduce the effectiveness of any vaccination programme.

In the event of an outbreak of strangles, horses should be segregated into 3 groups.  Those affected by the disease should be treated, but not vaccinated. Horses with no known contact with the disease should be vaccinated immediately.  Horses known to have been in contact should be observed for 7 to 10 days and vaccinated only if they have a normal temperature and show no clinical signs of the disease.

Thus, the control of strangles requires not only correct diagnosis and proper use of Equivac S, but also consideration of local factors.  To ensure best results, the work should be carried out by or directly supervised by a veterinarian.

Treatment of Strangles:
Equivac S is for control only and is of no value in the treatment of strangles.  Treatment is likely to vary from case to case and should be carried out by a veterinarian, or be under their supervision.

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