Modelling the within-herd transmission of Mycoplasma hyopneumoniae in closed pig herds

Abstract

BackgroundA discrete time, stochastic, compartmental model simulating the spread of Mycoplasma hyopneumoniae within a batch of industrially raised pigs was developed to understand infection dynamics and to assess the impact of a range of husbandry practices. A ‘disease severity’ index was calculated based on the ratio between the cumulative numbers of acutely and chronically diseased and infectious pigs per day in each age category, divided by the length of time that pigs spent in this age category. This is equal to the number of pigs per day, either acutely or chronically infectious and diseased, divided by the number of all pigs per all days in the model. The impact of risk and protective factors at batch level was examined by adjusting ‘acclimatisation of gilts’, ‘length of suckling period’, ‘vaccination of suckling pigs against M. hyopneumoniae’, ‘contact between fattening pigs of different age during restocking of compartments’ and ‘co-infections in fattening pigs’.ResultsThe highest ‘disease severity’ was predicted, when gilts do not have contact with live animals during their acclimatisation, suckling period is 28 days, no vaccine is applied, fatteners have contact with pigs of other ages and are suffering from co-infections. Pigs in this scenario become diseased/infectious for 26.1 % of their lifetime. Logistic regression showed that vaccination of suckling pigs was influential for ‘disease severity’ in growers and finishers, but not in suckling and nursery pigs. Lack of contact between gilts and other live pigs during the acclimatisation significantly influenced the ‘disease severity’ in suckling pigs but had less impact in growing and finishing pigs. The length of the suckling period equally affected the severity of the disease in all age groups with the strongest association in nursery pigs. The contact between fatteners of different groups influenced the course of infection among finishers, but not among other pigs. Finally, presence of co-infections was relevant in growers and finishers, but not in younger pigs.ConclusionThe developed model allows comparison of different prevention programmes and strategies for controlling transmission of M. hyopneumoniae.Electronic supplementary materialThe online version of this article (doi:10.1186/s40813-016-0026-1) contains supplementary material, which is available to authorized users.

Influence of pig gut microbiota on Mycoplasma hyopneumoniae susceptibility

“…In endemically infected herds, mature pigs serve as pathogen reservoirs. However, grow-to-finish pigs often develop clinical signs [2] at a high prevalence, which can reach 38–100% in most production systems [3]. Mycoplasma hyopneumoniae infections are mostly characterized by non-productive chronic cough lasting weeks to months, and pave an easy path for the establishment of secondary respiratory infections by decreasing the ciliary motility in the respiratory tract [1, 4].…”

Vaccines in control of infectious diseases of swine

“…Dostępne są szczepionki inaktywowane, z różnymi adiuwantami, zawierające komórki i/lub błony komórkowe Mycoplasma hyopneumoniae (Mhp) Tego typu biopreparaty nie zapobiegają zakażeniu, jednak istotnie zmniejszają kolonizację zarazka w nabłonku górnych dróg oddechowych, a w ślad za tym Szczepionka w stopniu zasadniczym chroni przed zakażeniem Mhp, a w przypadku infekcji istotnie ogranicza zakres oraz częstość ujawniania się objawów klinicznych i zmian patologicznych związanych z zakażeniem świń wspomnianym drobnoustrojem. W przypadku infekcji immunizowanych świń, istotnie ograniczone jest siewstwo Mhp przez zakażone zwierzęta (9). Według dostępnych danych czas powstania odporności po szczepieniu wynosi 3 tygodnie i trwa 23 tygodnie.…”