Transmission of <i>Actinobacillus pleuropneumoniae</i> in pigs is characterized by variation in infectivity

Velthuis, A.G.J.; Jong, M.C.M. de; Stockhofe, N.; Vermeulen, Thomas; Kamp, E. M.

doi:10.1017/s0950268802007252

Cited by 36 publications

(49 citation statements)

References 20 publications

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“…Experimentally, it has been shown that transmission of A. pleuropneumoniae from subclinically infected pigs by direct contact occurs with a rate ˇ of about 0.1 day −1 , meaning that every infectious pigs can infect on average 0.1 susceptible piglets per day (Velthuis et al, 2002(Velthuis et al, , 2003. Transmission by indirect contact, e.g.…”

Section: Introductionmentioning

confidence: 99%

Transmission of Actinobacillus pleuropneumoniae among weaned piglets on endemically infected farms

Tobias

Bouma

Broek

et al. 2014

Preventive Veterinary Medicine

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Clinical outbreaks due to Actinobacillus pleuropneumoniae occur recurrently, despite the wide-scale use of antimicrobials or vaccination. Therefore, new approaches for the prevention and control of these outbreaks are necessary. For the development of alternative measures, more insight into the transmission of the bacterium on farms is necessary. The aim of this cohort study was to quantify transmission of A. pleuropneumoniae amongst weaned piglets on farms. We investigated three possible transmission routes: (i) indirect transmission by infected piglets within the same compartment, (ii) transmission by infected pigs in adjacent pens and (iii) transmission by direct contact within pens. Additionally, we evaluated the effect of independent litter characteristics on the probability of infection. Two farms participated in our study. Serum and tonsil brush samples were collected from sows pre-farrowing. Serum was analysed for antibodies against Apx toxins and Omp. Subsequently, tonsil brush samples were collected from all piglets from these dams (N=542) in three cohorts, 3 days before weaning and 6 weeks later. Tonsil samples were analysed by qPCR for the presence of the apxIVA gene of A. pleuropneumoniae. Before weaning, 25% of the piglets tested positive; 6 weeks later 47% tested positive. Regression and stochastic transmission models were used to assess the contribution of each of the three transmission routes and to estimate transmission rates. Transmission between piglets in adjacent pens did not differ significantly from that between non-adjacent pens. The transmission rate across pens was estimated to be 0.0058 day(-1) (95% CI: 0.0030-0.010), whereas the transmission rate within pens was ten times higher 0.059 day(-1) (95% CI: 0.048-0.072). Subsequently, the effects of parity and serological response of the dam and litter age at weaning on the probability of infection of pigs were evaluated by including these into the regression model. A higher dam ApxII antibody level was associated with a lower probability of infection of the pig after weaning; age at weaning was associated with a higher probability of infection of the pig after weaning. Finally, transmission rate estimates were used in a scenario study in which the litters within a compartment were mixed across pens at weaning instead of raising litter mates together in a pen. The results showed that the proportion of infected piglets increased to 69% if litters were mixed at weaning, indicating that farm management measures may affect spread of A. pleuropneumoniae.

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Section: Introductionmentioning

confidence: 99%

Transmission of Actinobacillus pleuropneumoniae among weaned piglets on endemically infected farms

Tobias

Bouma

Broek

et al. 2014

Preventive Veterinary Medicine

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“…In particular, the mean time to absorption and its variance are expressed in terms of R ! by equations (7) and (8). Second, the results show that the FS algorithm underestimates R !…”

Section: Discussionmentioning

confidence: 81%

“…For instance, Velthuis et al [8] studied the transmission of Actinobacillus pleuropneumoniae among pigs by means of a transmission experiment. The excretion pattern of the bacterium in tonsillar swabs and nasal swabs was highly variable.…”

Section: Discussionmentioning

confidence: 99%

“…Consider, for instance, the bacterial pathogen A. pleuropneumoniae in pigs where under experimental conditions the excretion pattern varies widely between individuals [8]. It may occur that individuals cease to excrete the bacteria but that excretion is resumed after a few days.…”

Section: Practical Considerationsmentioning

confidence: 99%

“…Consider, for instance, the bacterial pathogen Actinobacillus pleuropneumoniae in pigs. The length of the infectious period induced by this pathogen is unknown, and its excretion pattern varies widely between individual pigs [8], making it difficult to determine whether the epidemic process has ended when the transmission trial is stopped. For those pathogens it would be better to use an estimation method that does not rely on a final size situation.…”

Section: Introductionmentioning

confidence: 99%

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Quantification of transmission in one-to-one experiments

Velthuis

Jong

Bree³

et al. 2002

Epidemiol. Infect.

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SUMMARYWe study the statistical inference from data on transmission obtained from one-to-one experiments, and compare two algorithms by which the reproduction ratio can be quantified. The first algorithm, the transient state (TS) algorithm, takes the time course of the epidemic into account. The second algorithm, the final size (FS) algorithm, does not take time into account but is based on the assumption that the epidemic process has ended before the experiment is stopped. The FS algorithm is a limiting case of the TS algorithm for the situation where time tends to infinity. So far quantification of transmission has relied almost exclusively on the FS algorithm, even if the TS algorithm would have been more appropriate. Its practical use, however, is limited to experiments with only a few animals. Here, we quantify the error made when the FS algorithm is applied to data of one-to-one experiments not having reached the final size. We conclude that given the chosen tests, the FS algorithm underestimates the reproduction ratio R ! , is liberal when testing H0 : R !

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Review: Livestock disease resilience: from individual to herd level

Doeschl‐Wilson

Knap

Opriessnig

et al. 2021

Animal

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Infectious diseases are a major threat to the sustainable production of high-producing animals. Control efforts, such as vaccination or breeding approaches often target improvements to individual resilience to infections, i.e., they strengthen an animal’s ability to cope with infection, rather than preventing infection per se . There is increasing evidence for the contribution of non-clinical carriers (animals that become infected and are infectious but do not develop clinical signs) to the overall health and production of livestock populations for a wide range of infectious diseases. Therefore, we strongly advocate a shift of focus from increasing the disease resilience of individual animals to herd disease resilience as the appropriate target for sustainable disease control in livestock. Herd disease resilience not only captures the direct effects of vaccination or host genetics on the health and production performance of individuals but also the indirect effects on the environmental pathogen load that herd members are exposed to. For diseases primarily caused by infectious pathogens shed by herd members, these indirect effects on herd resilience are mediated both by individual susceptibility to infection and by characteristics (magnitude of infectiousness, duration of infectious period) that influence pathogen shedding from infected individuals. We review what is currently known about how vaccination and selective breeding affect herd disease resilience and its underlying components, and outline the changes required for improvement. To this purpose, we also seek to clarify and harmonise the terminology used in the different animal science disciplines to facilitate future collaborative approaches to infectious disease control in livestock.

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Transmission of Actinobacillus pleuropneumoniae in pigs is characterized by variation in infectivity

Cited by 36 publications

References 20 publications

Transmission of Actinobacillus pleuropneumoniae among weaned piglets on endemically infected farms

Transmission of Actinobacillus pleuropneumoniae among weaned piglets on endemically infected farms

Quantification of transmission in one-to-one experiments

Review: Livestock disease resilience: from individual to herd level

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