Improvac

Improvac is an immunological medicine used in male pigs to reduce ‘boar taint’ in the meat obtained from them after slaughter. Boar taint is the offensive odour or taste which may be present in pork or pork products from non-castrated mature male pigs. Boar taint is caused by the production and build-up of the natural compounds androstenone and skatole in the fat of these animals. Improvac is used as an alternative to physical castration (removal of the testes) to reduce the presence of these compounds. Improvac also reduces aggressive and sexual (mounting) behaviour in pigs.

Improvac can also be used in female pigs from 14 weeks of age intended for market to temporarily suppress ovarian function (suppression of oestrus) in order to reduce the number of unwanted pregnancies in gilts intended for slaughter, and to reduce the associated sexual behaviour (standing oestrus).

Improvac contains the active substance gonadotropin releasing factor (GnRF) analogue-protein conjugate.

Improvac is available as a solution for injection and can only be obtained with a prescription. Improvac is given to male and female pigs as two injections with at least a 4 week interval. The injection is given under the skin in the neck just behind the ear. In male pigs the first injection is from 8 weeks of age and the second 4 to 6 weeks before slaughter. Improvac’s effects start gradually within 1 week after the second injection. Androstenone and skatole levels are reduced from 4 to 6 weeks after the second injection and reduction of aggression and sexual behaviour is seen from 1 to 2 weeks after the second injection.

In female pigs the first injection is from 14 weeks of age. Improvac starts to be effective 1 week after the second injection. The reduction of sexual behaviour (standing oestrus) can be expected from 1 to 2 weeks after the second injection and the duration of immunological suppression of ovarian function has been demonstrated for 9 weeks after the second injection.

For more information about using Improvac, see the package leaflet or contact your veterinarian or pharmacist.

The active substance in Improvac is an analogue of (similar to) gonatadotropin releasing factor (GnRF). Improvac works by stimulating the pig’s immune system to produce antibodies against its gonadotropin-releasing hormone (GnRH), part of the system that controls sexual development. In male pigs this temporarily inhibits the function of the testicles and release of steroids, including androstenone, one of the two causes of boar taint. Skatole, the other major cause of boar taint, is produced in the intestines and levels are reduced since a reduced level of sex hormones allows the liver to metabolise (break it down) more efficiently. In female pigs the production of antibodies against GnRF causes a temporary suppression of ovarian function and the oestrus, and therefore reduces the incidence of unwanted pregnancies in female pigs intended for slaughter when they are comingled with entire male pigs, and the sexual behaviour.

Improvac also contains a compound derived from the sugar dextran as an adjuvant (ingredient that strengthens the immune response).

In a number of field studies pigs treated with Improvac were comparable to surgically castrated pigs in terms of levels of androstenone and skatole at slaughter. In addition, Improvac treated pigs had reduced blood levels of testosterone. The first injection had a limited effect, but the second injection is followed by production of antibodies against GnRF. The levels of antibodies decline over time but are still high enough to be reliably effective 4 to 6 weeks after the second injection.

Three field studies investigated the effectiveness of Improvac in reducing aggression and sexual behaviour in male pigs. Two studies showed reduction of aggression and mounting from 1 to 2 weeks after the second injection of Improvac, while the third studied the long term effect on aggression and mounting after 4 weeks only.

A total of fourteen laboratory and field studies were conducted in female pigs to study the efficacy of Improvac in suppressing oestrus in gilts. Some studies showed that Improvac prevented sexual maturation in gilts in the field until the time of slaughter at approximately 27 weeks of age when administered according to a 2 doses-schedule and up to 60 weeks of age when administered according to a 4-doses-schedule. Additional studies showed that Improvac led to notable reductions in ovary development, oestradiol and progesterone concentrations and oestrus behaviour after a second dose.

The studies also showed a reduction in the rate of unwanted pregnancies when female pigs are raised past the age when puberty typically develops and housed with non-castrated male pigs. Additionally, the suppression of ovarian function led to a reduction in sexual aggressive behaviour during oestrus. In female pigs, the duration of suppression of ovarian function has been demonstrated for 9 weeks after the second injection.

The most common side effects with Improvac (which may affect more than 1 in 10 pigs) are injection site swelling, which gradually resolves but in 20 to 30% of animals may last for more than 6 weeks, and a short-lived increase in body temperature ranging from 0.5 ˚C to 1.3 ˚C within 24 hours of vaccination.

For the full list of restrictions and all side effects reported with Improvac, see the package leaflet.

Improvac must not be given to either breeding female pigs or male breeding pigs. Improvac cannot be used during pregnancy.

Safety information has been included in the summary of product characteristics and the package leaflet for Improvac, including the appropriate precautions to be followed by healthcare professionals and animal owners or keepers.

Accidental self-injection of Improvac may produce similar effects in people to those seen in pigs. These may include a temporary reduction in sex hormone levels and reduced ability to reproduce in men and in women, including problems with pregnancy. The risk of these effects occurring is greater after a second or subsequent accidental injection than after a first injection. Special care should be taken to avoid accidental self-injection. Improvac must only be used with a safety injection device including a needle guard and a mechanism to prevent accidental operation of the trigger. In case of accidental self-injection, medical advice should be sought immediately and the package leaflet or label shown to the doctor.

Improvac must not be given to pigs by women who are or who may be pregnant at that time. In case of skin or eye contact the affected area should be rinsed immediately with water.

The withdrawal period is the time required after administration of a medicine before an animal can be slaughtered and the meat used for human consumption.

The withdrawal period for meat from pigs vaccinated with Improvac is ‘zero’ days, which means there is no mandatory waiting time.

The Agency’s Committee for Medicinal Products for Veterinary Use (CVMP) concluded that Improvac’s benefits are greater than its risks and recommended that it be approved for use in the EU.

Improvac received a marketing authorisation valid throughout the EU for on 11 May 2009.