Article

Economic and epidemiological evaluation of Salmonella control in Dutch dairy herds.

Wageningen UR, Agricultural Economics Research Institute, P.O. Box 35, 6700 AA Wageningen, The Netherlands.
Preventive Veterinary Medicine (Impact Factor: 2.39). 03/2009; 89(1-2):1-7. DOI: 10.1016/j.prevetmed.2008.12.007
Source: PubMed

ABSTRACT This paper presents an analysis of a Salmonella control program for Dutch dairy herds. Salmonella control strategies were evaluated using a computer-based model consisting of an epidemiological module and an economics module. The epidemiological module is a state transition model of the infectivity of a herd, with the unit of analysis being the individual farm. The probability of a herd going from one state in the model to another state was derived from biological characteristics of Salmonella infections in dairy herds, and the presence or absence of risk factors. The economics module was based on partial budgeting. Control measures were modeled as influencing the risk factors. Amongst the measures considered were the prohibition of transporting potentially infectious animals and manure to farms, the culling of chronically infected animals, and herd management measures such as separate housing of groups of animal that differ in age. Alternative strategies, both compulsory and obligatory, were defined and evaluated concerning the reduction of prevalence of infected herds, the cost of a strategy, and cost-effectiveness. Results of the model suggested that a compulsory control strategy which included culling chronically infected animals and prohibiting the transport of potentially infected animals reduces the prevalence of Salmonella positive herds considerably, and was most cost-effective. Adding hygienic measures and a ban on the transport of animal manure further reduces prevalence, but only slightly, and with substantially more costs.

0 Bookmarks
 · 
108 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Salmonella Dublin infections reduce gross margins and compromise animal health and welfare in dairy cattle herds. Despite on-going control efforts in several countries the duration and risk factors of a persistent infection have been difficult to study due to a lack of suitable data. This study utilised the unique opportunity to extract systematically collected repeated bulk-tank milk antibody measurements from all the Danish dairy herds during a 10-year period to perform a time-to-event analysis of the factors that affect the duration of test-positivity and the hazards of recovery from S. Dublin at herd level. Recovery was defined as a shift from test-positive to test-negative between two year-quarters followed by at least three more test-negative year-quarters. The average duration of infection was approximately 2 years. Predictors of recovery were tested in a multivariable Cox proportional hazard model allowing herds to recover from infection multiple times over the 10-year surveillance period. The model results were based on 36,429 observations with data on all the predictors, representing 3563 herds with a total of 3246 recoveries. Sixty-seven herds (2.4%) remained test-positive throughout the study period. The rest of the 317 herds that did not have any recoveries were censored, mainly due to a cessation of milk production. Prior recovery from test-positivity turned out not to be a significant predictor of recovery in the model. The effect of the duration of infection on the conditional probability of recovery (i.e. the hazard) was time-dependent: early in the study period, long durations of infection were predictive of a low hazard of recovery. Later in the control programme the effect of duration of infection was reduced indicating a desired effect of an intensified control programme. There was an increasing tendency towards longer durations and lower hazard of recovery with: (i) increasing herd sizes, (ii) increasing bulk-tank milk somatic cell counts, (iii) increasing local prevalence within a 5km radius, (iv) organic farming and (v) recent purchase of cattle from test-positive herds. Participation in a voluntary paratuberculosis control programme reduced the duration of infection, and there were indications that recovery from S. Dublin infection was stimulated by a centrally organised and targeted control campaign. This is the first large-scale study that investigated duration of infection and predictors of recovery from S. Dublin in cattle herds over an extended period of time. The results provide useful knowledge for the design of control programmes for S. Dublin.
    Preventive Veterinary Medicine 03/2013; · 2.39 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Salmonella Dublin affects production and animal health in cattle herds. The objective of this study was to quantify the gross margin (GM) losses following introduction and spread of S. Dublin within dairy herds. The GM losses were estimated using an age-structured stochastic, mechanistic and dynamic simulation model. The model incorporated six age groups (neonatal, pre-weaned calves, weaned calves, growing heifers, breeding heifers and cows) and five infection stages (susceptible, acutely infected, carrier, super shedder and resistant). The effects of introducing one S. Dublin infectious heifer were estimated through 1000 simulation iterations for 12 scenarios. These 12 scenarios were combinations of three herd sizes (85, 200 and 400 cows) and four management levels (very good, good, poor and very poor). Input parameters for effects of S. Dublin on production and animal health were based on literature and calibrations to mimic real life observations. Mean annual GMs per cow stall were compared between herds experiencing within-herd spread of S. Dublin and non-infected reference herds over a 10-year period. The estimated GM losses were largest in the first year after infection, and increased with poorer management and herd size, e.g. average annual GM losses were estimated to 49 euros per stall for the first year after infection, and to 8 euros per stall annually averaged over the 10 years after herd infection for a 200 cow stall herd with very good management. In contrast, a 200 cow stall herd with very poor management lost on average 326 euros per stall during the first year, and 188 euros per stall annually averaged over the 10-year period following introduction of infection. The GM losses arose from both direct losses such as reduced milk yield, dead animals, treatment costs and abortions as well as indirect losses such as reduced income from sold heifers and calves, and lower milk yield of replacement animals. Through sensitivity analyses it was found that the assumptions about milk yield losses for cows in the resistant or carrier stages had the greatest influence on the estimated GM losses. This was more influential in the poorer management scenarios due to increased number of infected cows. The results can be used to inform dairy farmers of the benefits of preventing introduction and controlling spread of S. Dublin. Furthermore, they can be used in cost-benefit analyses of control actions for S. Dublin both at herd and sector level.
    Preventive Veterinary Medicine 04/2013; · 2.39 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Salmonellosis is an important infection both in animals and in human beings. About the spreading of Salmonellosis in Italian cattle herds, the available data are poor and sporadic if we compared them with ones obtained in other countries. If we consider that there aren’t any structured national prevalence studies in Italy, a valid contribution for estimating the presence of the infection in bovine was offered by the activityof the Istituti Zooprofilattici Sperimentali network. In this context, it was interesting to describe clinical symptoms, gross lesions and further laboratory results observed in reported outbreaks from 2002 and 2009 in Piedmont Region, in order to show how Salmonella infection is an emerging disease in bovine and to remark that a correct diagnostic approach in abortions, neonatal diarrhoea and sudden death in adult animals must include the detection of this pathogen. Thanks to the simultaneous application of general and specific cultural test for Salmonella spp., infection was observed in 12 herds, totally 16 strains, respectively belonging to four different serovars (typhimurium, veneziana, dublin, derby). Salmonella detection in 11 calves and 3 fetus confirms the correct diagnostic approach in order to control the presence and the diffusion of Salmonellosis in cattle farms.
    Large Animal Review 01/2009; 15:243-247. · 0.12 Impact Factor

Full-text

Download
36 Downloads
Available from
May 21, 2014