title: A cohort study on Actinobacillus pleuropneumoniae colonisation in suckling piglets.
abstract: Actinobacillus pleuropneumoniae causes respiratory disease in pigs and despite the use of preventive measures such as vaccination and antimicrobials clinical outbreaks still occur. At weaning often many piglets are not colonised. If differences in prevalence between litters are large and if factors were known that could explain these differences, this may provide an opportunity to raise groups of A. pleuropneumoniae free piglets. To this end, a cohort study was performed on two endemically infected farrow-to-finish farms. Seventy-six of 133 sows were selected using stratified random selection by parity. Farmers complied with a strict hygiene and animal management protocol to prevent transmission between litters. Tonsil brush and serum samples taken three weeks before parturition were tested for antigen with an apxIVA qPCR and antibodies with Apx and Omp ELISAs, respectively. Three days before weaning tonsil brush samples from all piglets (n=871) were collected and tested for antigen. Whereas all sows tested positive both in serology tests as well as qPCR, 0.41 of the litters tested fully negative and 0.73 of all piglets tested negative. The proportion of positively tested piglets in positive litters ranged from 0.08-1.0 (median=0.36). A grouped logistic regression model with a beta binomial distribution of the probability for piglets to become infected was fitted to the data and associations with explanatory variables were explored. To test the possibility that alternatively the clustering was caused by onwards transmission among the piglets, a transmission model was fitted to the data incorporating sow-piglet and piglet-piglet transmission, but this model did not fit better. The results of this study showed that the number of colonised suckling piglets was highly clustered and mainly attributable to the variability of infectiousness of the dam, but no dam related risk factor for colonisation status of litter or piglets within litters could be identified.
authors.affiliation: Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 7, 3584 CL Utrecht, The Netherlands. Electronic address: T.J.Tobias@uu.nl.
authors.forename: T J
authors.initials: TJ
authors.lastname: Tobias
authors.affiliation: Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 7, 3584 CL Utrecht, The Netherlands.
authors.forename: D
authors.initials: D
authors.lastname: Klinkenberg
authors.affiliation: Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 7, 3584 CL Utrecht, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Bouma
authors.affiliation: Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 7, 3584 CL Utrecht, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: van den Broek
authors.affiliation: Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 7, 3584 CL Utrecht, The Netherlands.
authors.forename: A J J M
authors.initials: AJ
authors.lastname: Daemen
authors.affiliation: Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 1, 3584 CL Utrecht, The Netherlands; Central Veterinary Institute of Wageningen UR, PO Box 65, 8200 AB Lelystad, The Netherlands.
authors.forename: J A
authors.initials: JA
authors.lastname: Wagenaar
authors.affiliation: Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 7, 3584 CL Utrecht, The Netherlands.
authors.forename: J A
authors.initials: JA
authors.lastname: Stegeman
mesh_terms: D000189:Actinobacillus Infections / Q000382:microbiology / Q000662:veterinary*; D016977:Actinobacillus pleuropneumoniae / Q000302:isolation & purification*; D000818:Animals; D000833:Animals, Suckling; D000907:Antibodies, Bacterial; D002353:Carrier State; D015331:Cohort Studies; D005260:Female; D010298:Parity; D011247:Pregnancy; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology*; D013997:Time Factors
chemical_list: D000907:Antibodies, Bacterial
keywords: Actinobacillus pleuropneumoniae; Colonisation; Pig-microbiological disease; Pigs; Pneumonia; Respiratory disease