Modelling the spread of American foulbrood in honeybees

Abstract

We investigate the spread of American foulbrood (AFB), a disease caused by the bacterium Paenibacillus larvae, that affects bees and can be extremely damaging to beehives. Our dataset comes from an inspection period carried out during an AFB epidemic of honeybee colonies on the island of Jersey during the summer of 2010. The data include the number of hives of honeybees, location and owner of honeybee apiaries across the island. We use a spatial SIR model with an underlying owner network to simulate the epidemic and characterize the epidemic using a Markov chain Monte Carlo (MCMC) scheme to determine model parameters and infection times (including undetected ‘occult’ infections). Likely methods of infection spread can be inferred from the analysis, with both distance- and owner-based transmissions being found to contribute to the spread of AFB. The results of the MCMC are corroborated by simulating the epidemic using a stochastic SIR model, resulting in aggregate levels of infection that are comparable to the data. We use this stochastic SIR model to simulate the impact of different control strategies on controlling the epidemic. It is found that earlier inspections result in smaller epidemics and a higher likelihood of AFB extinction.

Prevalence of American foul brood disease of honeybee in north-west Pakistan

“…This result suggests that regional survey is most important before any control scheme. [19,20] From the present study, it appears that district Kohat honeybee farms (Figure 2) have higher level of AFB prevalence which may produce shocking effects on honey productions, because colony health is equally important for the production of honey and other by-products of honeybees. The untreated foul brood disease not only destroys the hive bee population, but also wipes out an apiary because colonies which showed no visible AFB signs may be infected but not yet showing signs of disease.…”

American foulbrood in a honeybee colony: spore-symptom relationship and feedbacks between disease and colony development

“…The lethality and epidemiology of AFB are driven by the resilience of the spores and the fact that the removal of diseased brood, a communal bee hygienic behaviour [23,24], is not sufficient to remove this source of infection [20,25]. The spores are distributed between colonies by swarming, robbing and in particular by beekeepers moving contaminated material between colonies [26,27].…”

“…Estimations have been made that as much as 25% of spore-producing colonies remain undetected [28]. Infections are therefore enzootic, since they remain in the population without external inputs [29], and occult, since they are present but largely visually undetected [27]. Colonies can produce large amounts of infectious P. larvae spores with relatively few cases of symptomatic brood, thus escaping detection during routine beekeeper inspections while continuing to be a source of infection both within a beekeeping operation, between beekeepers (through sale of bees and equipment) and to feral and managed colonies within flight range through drifting and robbing [30].…”

Survival, spread and establishment of the small hive beetle (Aethina tumida)

“…Taking the geographical locations and ownership details of all apiaries in Calabria, two similar mathematical models were constructed allowing transmission between apiaries. For this, an SIR (Susceptible-Infested-Removed) model was used, similar to that used for AFB (Datta et al, 2013).…”

“…Also infestation times were estimated for SHB-positive apiaries in the data, along with possible unknown 'occult' infestations, which are not present in the data but likely to have occurred given the dynamics of SHB dispersal. A Markov chain Monte Carlo (MCMC) likelihood scheme was used to generate samples from the joint posterior density of the parameters (see Datta et al, 2013).…”