Effect of sow mass vaccination against Mycoplasma hyopneumoniae on the humoral immune response of newborn piglets.

Pneumonia caused by Mycoplasma (M.) hyopneumoniae is one of the major respiratory diseases in swine production. Commercial vaccines for M. hyopneumoniae are widely used in weaned piglets to reduce lung lesions and clinical signs in the downstream flow; however, no information regarding the effect of mass immunization of the breeding herd is available. The aim of this work was to evaluate a mass vaccination protocol for M. hyopneumoniae on the humoral response of sows and their offspring 24 h post-partum (trial registration number 40156). A total of 52 sows from two different farms (13 primiparous and 13 multiparous sows on each farm), one with mass vaccination (MVF) and one without mass vaccination against M. hyopneumoniae (control farm (CF)) were enrolled in this study. Five piglets from each litter were selected, resulting in 260 piglets. Blood was collected from sows and piglets 24 h post-partum for M. hyopneumoniae antibody detection by ELISA. The results showed that primiparous sows from MVF had higher antibody titers compared to multiparous sows of the same farm, and multiparous and primiparous sows from the CF. Similar results were evidenced in their offspring. The findings of this study suggest that mass vaccination results in a more robust serologic response on primiparous sows, which could be the main target of vaccination strategies for the breeding herd.

Effect of parity segregation on Mycoplasma hyopneumoniae infection dynamics and pneumonic lesions in pigs / Efeito da ordem de parto segregada sobre a dinâmica de infecção de Mycoplasma hyopneumoniae e lesões pulmonares ao abate

Gilts represent a group risk for Mycoplasma hyopneumoniae vertical transmission in swine herds. Therefore, parity segregation can be an alternative to control M. hyopneumoniae infections. The study evaluated the effect of parity segregation on M. hyopneumoniae infection dynamics and occurrence and severity of lung lesions at slaughter. For that, three multiple site herds were included in the study. Herd A consisted of the farm where gilts would have their first farrowing (parity order (PO) 1). After the first farrowing PO 1 sows were transferred to herd B (PO2-6). Herd C was a conventional herd with gilt replacement (PO1-6). Piglets born in each herd were raised in separated nursery and finishing units. Sows (n = 33 (A), 37 (B), 34 (C)) in all herds were sampled prior to farrowing and piglets (n = 54 (A), 71 (B), 66 (C)) were sampled longitudinally at 21, 63, 100, 140 days of age and at slaughter for M. hyopneumoniae detection by PCR and lung lesions scoring. M. hyopneumoniae prevalence in sows did not differ among herds. Prevalence of positive piglets was higher at weaning in the PO1 herd (A) (P < 0.05). However, prevalence of positive pigs from 100 days of age to slaughter age was higher in the PO2-6 herd (B) (P < 0.05). Lung lesion occurrence and severity were higher in herd B. The authors suggested that the lack of a proper gilt acclimation might have influenced the results, leading to sows being detected positive at farrowing, regardless of the parity.

As leitoas consistem em um grupo de risco na transmissão vertical de Mycoplasma hyopneumoniae dentro do sistema de produção de suínos. Dessa forma, a segregação de partos poderia ser utilizada como alternativa para controlar as infecções por M. hyopneumoniae. O objetivo deste estudo foi avaliar o efeito da segregação de partos sobre a dinâmica de infecção de M. hyopneumoniae e a ocorrência e severidade das lesões pulmonares ao abate. Para isso três sistemas de produção de suínos com três sítios cada foram incluídos no estudo. A granja A consistia da unidade onde as leitoas tem o primeiro parto, ou seja, alojava somente de fêmeas de ordem de parto 1 (Granja OP1). Após o primeiro parto as fêmeas OP1 foram transferidas para a granja B (Granja OP2-6), ou seja, consistia de fêmeas de ordem de parto 2 a 6, e a granja C consistiu em uma granja convencional com reposição de leitoas (Granja OP1-6), com fêmeas de ordem de parto 1 a 6. Os leitões nascidos de cada granja foram transferidos e criados em creches e terminações segregadas. As matrizes (n = 33 (A), 37 (B), 34 (C)) de todas as granjas do estudo foram amostradas previamente ao parto e os leitões (n = 54 (A), 71 (B), 66 (C)) foram amostrados longitudinalmente aos 21, 63, 100 e 140 dias de idade e ao abate. Em todos os momentos de coleta, as amostras foram avaliadas por PCR para detecção de M. hyopneumoniae. As lesões pulmonares foram avaliadas e escores de lesão foram atribuídos ao abate. A prevalência de matrizes positivas para M. hyopneumoniae não diferiu entre as granjas (P > 0,05). A prevalência ao desmame foi maior na granja A (OP1) (P < 0,05). No entanto, dos 100 dias de idade até o abate a prevalência de leitões positivos para M. hyopneumoniae foi maior na granja B (OP2-6) (P < 0,05). A ocorrência e severidade de lesões pulmonares foram maiores na granja B. Os autores sugerem que a falta de uma aclimatação adequada das leitoas pode ter influenciado nos resultados, levando à detecção de matrizes positivas ao parto, independente da ordem de parto.

A model to investigate the optimal seeder-to-naïve ratio for successful natural Mycoplasma hyopneumoniae gilt exposure prior to entering the breeding herd.

Due to the significance of Mycoplasma hyopneumoniae as a swine respiratory pathogen, acclimation measures are taken into consideration when obtaining replacement gilts from negative sources to be introduced to endemically infected herds. The aim of this study was to evaluate the optimum seeder-to-naïve gilt ratio in a 4-week period for successful natural exposure to M. hyopneumoniae. Sixty gilts were divided in two groups, 21 2-week old seeder gilts were inoculated with M. hyopneumoniae, and 39 aged-matched naïve gilts were exposed to the seeders during a 4-week period. The exposure was set by dividing the gilts into six groups of 10 with different ratios of seeder-to-naïve, from 1:9 until 6 seeders and 4 naïve gilts. Laryngeal swabs, oral fluids and blood samples were collected from all gilts prior to, during and after inoculation and exposure. Infection in seeders was confirmed by development of clinical signs, seroconversion post-inoculation, and detection of M. hyopneumoniae genetic material. Naïve were considered positive after 4 weeks if M. hyopneumoniae was detected on bronchial swab or fixed lung tissue. As result, 33% (3/9) naïve gilts were positive in the 1:9 ratio, 75% (6/8) in 2:8, 28% (2/7) in 3:7, 33% (2/6) in 4:6, 80% (4/5) in 5:5 and 100% (4/4) in the 6:4 ratio. The estimated transmission rate (ß) and expected probability of infection (ψ) were 1.28 per pig/week and 0.6, respectively. In this study, six seeders were required in a group of 10 gilts for successful exposure to M. hyopneumoniae in a 4-week exposure period.