A mathematical model of the effects of chronic carriers on the within-herd spread of contagious bovine pleuropneumonia in an African mixed crop–livestock system

Lesnoff, Matthieu; Laval, Géraud; Bonnet, Pascal; Chalvet‐Monfray, Karine; Lancelot, Renaud; Thiaucourt, François

doi:10.1016/j.prevetmed.2003.11.009

Cited by 24 publications

(20 citation statements)

References 16 publications

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“…In fact, the apparent survival rate of seropositive tortoises approached one and was higher than that of seronegative tortoises. This result was surprising, given our understanding of the dynamics of chronic mycoplasmal respiratory disease in mammals and birds (Simecka et al 1992, Cartner et al 1996, Vicca et al 2002, Faustino et al 2004, Lesnoff et al 2004. One possible explanation for this finding is that seropositive tortoises captured in our study represent individuals within the population that survived the initial infection and then developed chronic disease.…”

Section: Discussionmentioning

confidence: 74%

Upper respiratory tract disease, force of infection, and effects on survival of gopher tortoises

Özgül

Oli

Perez-Heydrich

2009

Ecological Applications

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Abstract. Upper respiratory tract disease (URTD) caused by Mycoplasma agassizii has been hypothesized to contribute to the decline of some wild populations of gopher tortoises (Gopherus polyphemus). However, the force of infection (FOI) and the effect of URTD on survival in free-ranging tortoise populations remain unknown. Using four years (2003)(2004)(2005)(2006) of mark-recapture and epidemiological data collected from 10 populations of gopher tortoises in central Florida, USA, we estimated the FOI (probability per year of a susceptible tortoise becoming infected) and the effect of URTD (i.e., seropositivity to M. agassizii) on apparent survival rates. Sites with high (!25%) seroprevalence had substantially higher FOI (0.22 6 0.03; mean 6 SE) than low (,25%) seroprevalence sites (0.04 6 0.01). Our results provide the first quantitative evidence that the rate of transmission of M. agassizii is directly related to the seroprevalence of the population. Seropositive tortoises had higher apparent survival (0.99 6 0.0001) than seronegatives (0.88 6 0.03), possibly because seropositive tortoises represent individuals that survived the initial infection, developed chronic disease, and experienced lower mortality during the four-year span of our study. However, two lines of evidence suggested possible effects of mycoplasmal URTD on tortoise survival. First, one plausible model suggested that susceptible (seronegative) tortoises in high seroprevalence sites had lower apparent survival rates than did susceptible tortoises in low seroprevalence sites, indicating a possible acute effect of infection. Second, the number of dead tortoise remains detected during annual site surveys increased significantly with increasing site seroprevalence, from ;1 to ;5 shell remains per 100 individuals. If (as our results suggest) URTD in fact reduces adult survival, it could adversely influence the population dynamics and persistence of this latematuring, long-lived species.

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Section: Discussionmentioning

confidence: 74%

Upper respiratory tract disease, force of infection, and effects on survival of gopher tortoises

Özgül

Oli

Perez-Heydrich

2009

Ecological Applications

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“…The model (see for details [15,18]) divided the herd into 4 infection-states ( Although the involvement of CBPP chronic carriers in the long-term persistence of the disease in the cattle population has been suggested by several authors [20,21,28], the carriers' infectiousness (which remains unproven) and their role during the withinherd outbreak are negligible compared to clinical cases [33]. Therefore they were not represented in the model.…”

Section: Within-herd Cbpp-spread Simulationmentioning

confidence: 99%

“…The basic reproduction ratio R 0 corresponding to the within-herd CBPP-spread Markov-chain model was computed as follows (see [18] for demonstration):…”

Section: Appendix 1 the Cbpp-spread Stochastic Markov-chain Modelmentioning

confidence: 99%

A mathematical model of contagious bovine pleuropneumonia (CBPP) within-herd outbreaks for economic evaluation of local control strategies: an illustration from a mixed crop-livestock system in Ethiopian highlands

et al. 2004

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-Contagious bovine pleuropneumonia (CBPP) is a respiratory disease of cattle caused by Mycoplasma mycoides subsp. mycoides small colony. CBPP is a major cause for concern in African countries (because of mortality, animal-production losses and cost of control). We present a simulation framework to compare economic efficiency of local (i.e., at the herd level) CBPP-control strategies (vaccination and antibiotic treatments). This framework was illustrated with data from an Ethiopian highlands cattle-smallholder system (Boji district, West Wellega Zone), where veterinary services recently reported CBPP cases and a research programme was set up to estimate the epidemiological parameters of infection spread. With the data considered (low CBPP virulence), antibiotics were the most efficient strategy. A sensitivity analysis should be carried out taking into account all uncertain parameters regarding economic values of costs and benefits, expected effectiveness of animal health interventions, animal production yields and epidemiological patterns of the disease. Our framework can help for decision making in CBPP management and health policy design at herd level. Moreover, any threshold analyses (e.g., value of vaccine cost for a benefit being nil) could easily be implemented. Mycoplasma mycoides subsp. mycoides small colony.La PPCB est un problème sanitaire majeur dans les pays africains (en raison de la mortalité, des pertes de production et du coût de contrôle). Nous présentons un modèle de simulation permettant de comparer l'efficience économique de stratégies de contrôle (vaccination et traitement antibiotique) au niveau du troupeau. Ce modèle a été illustré avec des données provenant d'un système mixte d'agriculture-élevage dans les hauts plateaux éthiopiens (district de Boji, zone du West Wellega), où des cas de PPCB ont été rapportés par les services vétérinaires et où un programme de recherche a été mis en oeuvre pour estimer les paramètres épidémiologiques de la PPCB. Avec les données considérées (faible virulence de la PPCB), les traitements antibiotiques ont été la stratégie la plus efficiente. Une analyse de sensibilité devra être mise en oeuvre pour prendre en compte l'incertitude des valeurs des paramètres économiques, de production animale et épidémiologiques. Notre modèle de simulation peut aider pour l'aide à la décision dans la gestion de la PPCB et la planification de programmes sanitaires. Le modèle permet aussi d'estimer les limites acceptables du coût des stratégies de contrôle au niveau du troupeau (par exemple le coût du vaccin engendrant un bénéfice nul).péripneumonie contagieuse bovine / stratégies de contrôle / économie / modèle de Markov / Ethiopie

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“…[17] used a discrete-time population matrix model. As a matter of fact, such models are commonly used for simulating the dynamics of age-structured populations [18–20], and represent epidemiological processes [21, 22]. We chose this approach for this study.…”

Section: Introductionmentioning

confidence: 99%

Modelling the Dynamics of Post-Vaccination Immunity Rate in a Population of Sahelian Sheep after a Vaccination Campaign against Peste des Petits Ruminants Virus

2016

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BackgroundPeste des petits ruminants (PPR) is an acute infectious viral disease affecting domestic small ruminants (sheep and goats) and some wild ruminant species in Africa, the Middle East and Asia. A global PPR control strategy based on mass vaccination—in regions where PPR is endemic—was recently designed and launched by international organizations. Sahelian Africa is one of the most challenging endemic regions for PPR control. Indeed, strong seasonal and annual variations in mating, mortality and offtake rates result in a complex population dynamics which might in turn alter the population post-vaccination immunity rate (PIR), and thus be important to consider for the implementation of vaccination campaigns.MethodsIn a context of preventive vaccination in epidemiological units without PPR virus transmission, we developed a predictive, dynamic model based on a seasonal matrix population model to simulate PIR dynamics. This model was mostly calibrated with demographic and epidemiological parameters estimated from a long-term follow-up survey of small ruminant herds. We used it to simulate the PIR dynamics following a single PPR vaccination campaign in a Sahelian sheep population, and to assess the effects of (i) changes in offtake rate related to the Tabaski (a Muslim feast following the lunar calendar), and (ii) the date of implementation of the vaccination campaigns.ResultsThe persistence of PIR was not influenced by the Tabaski date. Decreasing the vaccination coverage from 100 to 80% had limited effects on PIR. However, lower vaccination coverage did not provide sufficient immunity rates (PIR < 70%). As a trade-off between model predictions and other considerations like animal physiological status, and suitability for livestock farmers, we would suggest to implement vaccination campaigns in September-October. This model is a first step towards better decision support for animal health authorities. It might be adapted to other species, livestock farming systems or diseases.

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A mathematical model of the effects of chronic carriers on the within-herd spread of contagious bovine pleuropneumonia in an African mixed crop–livestock system

Cited by 24 publications

References 16 publications

Upper respiratory tract disease, force of infection, and effects on survival of gopher tortoises

Upper respiratory tract disease, force of infection, and effects on survival of gopher tortoises

A mathematical model of contagious bovine pleuropneumonia (CBPP) within-herd outbreaks for economic evaluation of local control strategies: an illustration from a mixed crop-livestock system in Ethiopian highlands

Modelling the Dynamics of Post-Vaccination Immunity Rate in a Population of Sahelian Sheep after a Vaccination Campaign against Peste des Petits Ruminants Virus

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