BACTERIOLOGIE

Mycoplasma hyopneumoniae
• Influence of age and maternal antibodies on antibody responses of neonatal piglets vaccinated against Mycoplasma hyopneumoniae.
• Evaluation of virulence of Mycoplasma hyopneumoniae field isolates.
• Dynamics of Mycoplasma hyopneumoniae infection in 12 farms with different production systems.
• Experimental dual infection of pigs with an H1N1 swine influenza virus (A/Sw/Hok/2/81) and Mycoplasma hyopneumoniae.

Influence of age and maternal antibodies on antibody responses of neonatal piglets vaccinated against Mycoplasma hyopneumoniae.
HODGINS DC, SHEWEN PE, DEWEY CE
Journal of Swine Health and Production, Vol. 12, N°1, 2004, 10-16
http://www.aasv.org/shap.html
Keywords: swine, Mycoplasma hyopneumoniae, vaccination, maternal antibody, neonate, flexibility.
When dealing with M. hyopneumoniae and vaccination, two aspects come into conflict : should vaccination be delayed so as to avoid the immunosuppressive effect of maternal antibodies or should it be anticipated so as to induce early active immunity in order to protect piglets against early exposure to M. hyopneumoniae? Two commercial swine herds were involved in this study. Sows from herd A were not vaccinated while sows from herd B were vaccinated twice before breeding and then one week before farrowing. In each herd, four groups were respectively vaccinated at 2, 3 or 4 weeks of age or kept as non-vaccinated controls. The results of this particular study show that the maternal antibody level is to be considered the essential criterion for vaccination and that age at vaccination, understood as maturity of immune system, is not important since active antibody responses were achieved in piglets as young as 2 weeks of age.

Evaluation of virulence of Mycoplasma hyopneumoniae field isolates.
VICCA J, STAKENBORG T, MAES D, BUTAYE P, PEETERS J, DE KRUIF A, HAESENBROUCK F
Veterinary Microbiology, 98, 2004, 177-190
http://www.sciencedirect.com
Keywords: pig, Mycoplasma hyopneumoniae, virulence, RAPD.
Six M. hyopneumoniae strains isolated from different Belgian farrow-to-finish herds were compared. Following intratracheal inoculation of each isolate in conventional M. hyopneumoniae-free piglets, the results of respiratory disease scores, lung lesion scores, histiopathology, immunofluorescence, serology and randomly amplified polymorphic DNA analysis (RAPD) were analyzed in order to assess the virulence of each isolate and achieve a better understanding of their genetic variability. The isolates showed significant differences and were classified as low, moderately and highly virulent strains.
Furthermore, a 5000 bp RAPD fragment was detected only in the isolates of moderate and high virulence suggesting that this fragment could be used as a virulence marker, which should be the subject of further studies.

Dynamics of Mycoplasma hyopneumoniae infection in 12 farms with different production systems.
SIBILA M, CALSAMIGLIA M, VIDAL D, BADIELLA L, ALDAZ, A, JENSEN JC
The Canadian Journal of Veterinary Research, 68, 2004, 12-18
Keywords: flexibility
Twelve Spanish farms experiencing respiratory problems were included in this study. These herds differed according to their production system (one to two-site systems or three-site systems) as well as the use of vaccination and medicated feed (either one, both or none of them). In all of the herds the presence of M. hyopneumoniae was demonstrated. However, the percentage of positive pigs varied greatly from farm to farm and M. hyopneumoniae was not necessarily the agent responsible for the respiratory manifestations. The dynamics of infection of three-site systems on one hand and one to two site systems on the other hand are clearly distinct: three-site systems seems to hamper vertical transmission of M. hyopneumoniae (lower nursery colonization) but are subjected to more acute outbreaks in late finishing pigs. The prevalence of M. hyopneumoniae was anyway lower in three-site systems. The type of the farm influences M. hyopneumoniae colonization and seroconversion to a great extent.

Experimental dual infection of pigs with an H1N1 swine influenza virus (A/Sw/Hok/2/81) and Mycoplasma hyopneumoniae.
YAZAWA S, OKADA M, ONO M, FUJII S, OKUDA Y, SHIBATA I, KIDA H
Veterinary Microbiology, 98, 2004, 221-228
http://www.sciencedirect.com
Keywords: swine influenza virus, H1N1, Mycoplasma hyopneumoniae, dual infection.
This study was carried out in caesarian derived colostrum deprived (CDCD) pigs, which were either inoculated only with swine influenza virus (SIV), inoculated only with M. hyopneumoniae or dually inoculated. Dual infection was shown to significantly increase the severity of the lesions caused by M. hyopneumoniae alone.