Mycoplasma hyopneumoniae infections in peri-weaned and post-weaned pigs in Belgium and The Netherlands: Prevalence and associations with climatic conditions.

Mycoplasma hyopneumoniae (M. hyo) is an important pathogen in modern intensive pig farming in Europe. The objectives of the present study were (1) to use the tracheobronchial swab (TBS) technique to obtain data on the distribution of M. hyo infections in recently weaned pigs in Belgium and The Netherlands, and (2) to look for associations between infection prevalence and specific climatic conditions. One hundred and seventy-six pig herds were randomly selected and 30 piglets sampled on each farm: 18 at 3-5 weeks of age and 12 at 6-11 weeks. Mucus collected from the tracheobronchial bifurcation and suspended in saline was subjected to PCR analysis for M. hyo. In 27% of herds (n= 44) at least one piglet tested positive for M. hyo at 3-5 weeks of age, and 29% (n= 47) at 6-11 weeks of age. The individual animal prevalence at the two ages was 7.1% and 10.9%, respectively. The probability of 3-5 week old piglets being M. hyo-positive was negatively associated with the precipitation rate (odds ratio [OR] = 0.971) during the week preceding the sampling. In the older post-weaning group, the odds of being M. hyo-positive at piglet level were significantly affected by season (OR of detection during autumn compared to summer 20.9). Thus, under Belgian and Dutch field conditions, piglets may be infected with M. hyo very early in life, with prevalence increasing further during the post-weaning period.