5 Vaccines On large pig units vaccination plays a vital role in disease control. It is vital that the vaccines are used to the manufacturer’s recommendations, particularly with regard to the age of the pig and the possibility of maternal passive immunity. It is also important that the risk of each disease is assessed and the vaccine is used only if actually required (see Table 5.1 below). With pet pigs and small units assessing the need for vaccination is equally important. In the author’s opinion, in the UK situation the only vaccine required by all pet pigs, and in fact all commercial pigs as well, is against Erysipelothrix rhusiopathiae. There are fundamentally three types of vaccine: • Live attenuated. • Killed and inactivated. • Small components of the pathogen. When a non-infected animal is vaccinated there are three possible outcomes if the animal is then challenged by field infection (Brown, 2012): • The animal’s immune system is so strong it resists the infectious agent and the animal remains clean and healthy. • The weight of infectious challenge is so high that, despite vaccination, the animal still succumbs to clinical disease. • Immunity conferred by the vaccine is strong enough to resist clinical disease, but the pathogen is still able to enter the body and so the animal becomes a symptomless carrier of the pathogen. This is obviously most unsatisfactory as symptomless carriers remain undetected in the herd and can, under stressful situations, become excreters of the pathogen or even break down with clinical disease. At the time of vaccination we cannot always be sure that the animal is not already infected. If a live vaccine is being used in such a circumstance then there is a risk of genetic recombination between the vaccinal strain and the field strain, thereby producing a new genetic variant of the pathogen which may or may not then be susceptible to the current vaccines. Volatile viruses, such as influenza virus, are changing genetically very frequently either as a result of straightforward mutations or as a result of recombination between various field strains. PRRS virus also appears to mutate fairly regularly and the industry in the UK must remain alert to avoid importation of US strains and the so-called highly pathogenic strains. Table 5.1. Vaccines available. The vast majority of vaccines administered to pigs are given by injection and so vaccines tend to be administered at times in the pig flow cycle when animals are handled or moved. At such times the dangers of operator self-injection are always present, particularly when large numbers of animals are being vaccinated. Self-injection of oil-based vaccines requires immediate medical attention. Needles must be changed regularly to avoid sepsis not only at the site of injection in the pig but also if there is self-injection. Pigs from 6 weeks of age should be given two injections, 4 weeks apart, of E. rhusiopathiae vaccine. A single injection of the combined vaccine should be given at least 2 weeks before mating. Then sows should receive a booster of the E. rhusiopathiae vaccine every 6 months, with the combined vaccine of E. rhusiopathiae plus porcine parvovirus (PPV) being given annually. Gilts and young boars over 6 months of age should be given a single dose, 2 weeks before mating. Sows and boars require a booster dose annually. For a primary vaccination course gilts require two injections 3–4 weeks apart, at least 3 weeks before mating. Sows require two injections 3–4 weeks apart. Vaccination of all sows in the herd within a short period is recommended. Revaccination is one injection at 60–70 days of each pregnancy, starting from the first pregnancy following the primary vaccination course. The piglet is born with no bacterial flora in its intestine and potentially damaging organisms will begin to colonize the gut from birth onwards. Vaccines that are given to the sow or the gilt prior to farrowing aim to ensure colostral antibodies are well targeted to combat these organisms. Certain authorities advocate feedback attempts to work in a similar manner. However this is dangerous as other diseases may be spread inadvertently. A primary vaccination schedule is two injections separated by 6 weeks. Revaccination is one dose to be given to the sow ideally 2–6 weeks before farrowing. Protection can be achieved by a single injection from the age of 14 weeks. Revaccination should be carried out on a herd basis every 4 months. Initially two injections with an interval of at least 3 weeks between injections, the second dose to be administered at least 3 weeks before farrowing, are required. Only a single booster dose is required in subsequent pregnancies at approximately 3–4 weeks pre-farrowing. A primary vaccination scheme consists of an initial course of two doses. The first dose should be given at service or, if necessary, at any time up to 6 weeks before farrowing. The second dose should be given 2 weeks before farrowing is expected. For a revaccination scheme a single dose should be given 2 weeks before farrowing is expected. A primary course of vaccination consists of two doses. The first injection should be given 5–7 weeks before farrowing and the second injection, 2 weeks before farrowing. Revaccination consists of a single injection 2 weeks before each subsequent farrowing. Basic vaccination for gilts consists of two injections. The first injection should be followed in 3–4 weeks by the second injection, at least 2 weeks before mating. One further injection must be given, at least 2 weeks before farrowing. With sows the first injection should be followed in 3–4 weeks by a second injection, at least 2 weeks before farrowing. Revaccination consists of a single injection at each gestation, at least 2–4 weeks before farrowing. There is a combined vaccine available but it is not licensed in the UK. Primary vaccination consists of two injections of one dose from the age of 96 days, with an interval of 3 weeks between injections. A booster is possible at each stage of pregnancy and lactation. When vaccination is performed 14 days prior to farrowing with one dose, it provides maternally derived immunity to the piglets, which protects them from clinical signs of influenza at least until day 33 after birth. There is a vaccine available for serotypes 1, 5 and 7. It is not licensed in the UK. An initial dose at 10 weeks of age should be followed by a second injection 2 weeks later. Pigs from 6 weeks of age should be given two injections 4 weeks apart. Vaccination is available for pigs at least 5 weeks of age. Two doses should be given separated by 2 weeks. Immunity will last for 14 weeks. Administration of a single 2 ml dose orally to pigs from 3 weeks of age should be given irrespective of body weight. Vaccination is via the drinking water. A single injection to be given between 3 and 10 weeks of age. Certain vaccines can be given as early as 7 days, but the majority of these require two doses 2–4 weeks apart. Pigs are to be vaccinated from 7 days of age, with a second dose being given 14–21 days later. A single injection from 2 weeks of age will give at least 17 weeks of immunity. Some vaccines claim to give immunity duration of 22 weeks. There is a live vaccine available but it is not licensed in the UK. This bacterin is not licensed in the UK. A primary course of vaccination consists of two injections of one dose: (i) from the age of 96 days, with an interval of 3 weeks between injections, to achieve duration of immunity over 6 months; or (ii) between the ages of 56 and 96 days, with an interval of 3 weeks between injections, to achieve duration of immunity over 4 months. This should only be used in circumstances where there is an extra high risk of tetanus. Animals should be vaccinated when at least 3 months of age and given a second dose in 4–8 weeks. Revaccination should be carried out annually. A 2 ml dose contains a minimum of 300 μg of gonadotrophin-releasing hormone (GnRF) analogue-protein conjugate. It can be used in male pigs from 8 weeks of age to induce antibodies against GnRF to produce a temporary immunological suppression of testicular function (Fig. 5.1). It causes a reduction in entire male pigs after puberty of: • Boar taint. • Aggression. • Mounting behaviour.
Introduction
Vaccines to be given to Sows to Prevent Abortion
Erysipelothrix rhusiopathiae and porcine parvovirus
Porcine parvovirus
Porcine reproductive and respiratory syndrome
Vaccines to be given to Sows to Give Passive Immunity to Neonatal Piglets
Introduction
Atrophic rhinitis
Aujeszky’s disease
Clostridium tetani and Clostridium perfringens type B, C and D
Escherichia coli (K99 strains) and Clostridium perfringens type B, C and D
Escherichia coli (K99 strains)
Porcine circovirus type 2
Rotavirus, transmissible gastroenteritis and colibacillosis
Swine influenza A virus
Vaccines to be given to Growing and Fattening Pigs
Actinobacillus pleuropneumoniae
Aujeszky’s disease
Erysipelothrix rhusiopathiae
Haemophilus parasuis
Lawsonia intracellularis
Mycoplasma hyopneumoniae
M. hyopneumoniae and H. parasuis combined
Porcine circovirus type 2
Salmonella choleraesuis and Salmonella typhimurium
Streptococcus suis serotype 2
Swine influenza A virus
Tetanus
Improvac
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