Some products are approved for two shot vaccination programs, normally in the first week of life and repeated 2-3 weeks later and some approved for a single injection usually at 3 weeks of age and above. There is one combination vaccine against both Mycoplasma hyopneumoniae and Haemophilus suis.
All of these are made from killed mycoplasma cultures (bacterins) but have different adjuvants in which the cultures are suspended. The adjuvants have different properties, but generally they cause some irritation to stimulate and activate the body's immuno-defence system against the foreign materials (antigens) from the mycoplasma. When the body comes across the infection naturally, it is already primed to fight it quickly. Some adjuvants are considered relatively mild, like ALOH, whereas the oil-based ones, usually in the form of emulsions (oil and water mix) are more reactive and may take a longer time to be taken up, therefore giving a more prolonged release and stimulation. Some such as Impran are more difficult to inject as they are water in oil and have a higher viscosity. All the major single shot products use this technique plus an increase in the antigen quantity or concentration to stimulate a strong, durable immunity.
It is generally accepted that there is a relationship between the size of the lung lesions caused by enzootic pneumonia and an adverse effect on growth rate. Approximately an average herd lung lesion score of 10% will reduce growth by 5% between 25kg and slaughter. Usually enzootic pneumonia affects the fattening pig especially later on when there is overcrowding and therefore the major adverse effect is in that time period. There in the final phase (60-95 kg), the depressant effect on growth may be doubled to nearly 10%. Larger lung lesions are often associated with secondary bacterial infections as well such as Pasteurella multocida, which also depress growth and cause clinical disease.
Vaccination against mycoplasma aims to reduce the level of lesions and thereby improve performance. None of the vaccines prevent enzootic pneumonia 100% but generally they are effective in reducing lung lesions and permitting pigs to grow faster.
A number of two-shot vaccines were compared in an artificial infection study (Thacker and others, 1998). They were given to piglets with no antibodies against mycoplasma, at 2 and 5 weeks of age. They were challenged with M. hyopneumoniae at 12 weeks of age and their lungs examined 4 weeks later.
Figure 1. Comparative protection of two-shot vaccines
(Source: Thacker and others, 1998)
All of the vaccines gave a significant degree of protection in comparison with the unvaccinated controls, with M+PAC (Schering-Plough Animal Health) giving numerically the best protective response, with a 93% reduction in lung lesion score.
In a further study, (Groth & Rapp-Gabrielson, 2001) M+PAC was given to piglets, which were sero-negative to M. hyopneumoniae, at 6 weeks of age at double the dose (1-shot program) and compared with two other major 1-shot products, Stellamune Once (Respisure in the US - Pfizer) and Ingelvac M. hyo 1 (Boehringer Ingelheim). The pigs were artificially challenged with M. hyopneumoniae at 10 weeks of age and the pigs' lungs were examined at 14 weeks of age.
Figure 2. Comparative protection of one-shot vaccines
(Source: Groth and others, 2001)
All of the treatment groups showed significant improvements over the unvaccinated infected controls, with M+PAC one shot giving the greatest protection (93%), which was better numerically than both the other single vaccination products Stellamune Once (88%) and Ingelvac M. hyo.1 (79%).
In both trials the conditions were controlled and ideal, as there were no maternal antibodies in the piglets to interfere with the vaccine response, unlike in the farm situation where responses can be more variable. All of the vaccines demonstrated a very positive effect but with M+PAC usually leading the way.
References:
Groth, D and Rapp-Gabrielson, V. (2001) Evaluation of M+PAC in one and two dose-regimens against competitor one-dose Mycoplasma hyopneumoniae bacterins. Proceedings of the Allan D. Leman Swine Conference, Recent Research Reports, Volume 28 Supplement, University of Minnesota, USA, p41. Thacker, E.L., Thacker, B.J, Boettcher, T.B. and Jayappa, H. (1998) Comparison of antibody production, lymphocyte stimulation, and protection induced by four commercial Mycoplasma hyopneumoniae bacterins, Swine health and Production, 6, 3, 107-112.