Translating theory into practice: Targeted tuberculosis control in meerkats of the Kalahari
Royal Veterinary College (RVC) PhD student Stuart Patterson will shortly be commencing research which aims to improve our understanding of TB control in wild animals. His work will build upon previous work which established the epidemiology of this disease in meerkats of the Kalahari by Dr Julian Drewe. Stuart will be co-supervised by Julian and Prof. Dirk Pfeiffer (both RVC) and Prof. Tim Clutton-Brock at the University of Cambridge. Here, Stuart explains his research plans.
Traditional disease control in animals has focused on attempting to reduce transmission by means of preventive actions (such as vaccination or treatment) applied to all members of the society. Such strategies are based on the assumption that all individuals are as likely as each other to become infected and to transmit to others. However, recent research has suggested that this is not the case: there is a skew in the number of infections caused by an individual, with some members of a group playing little or no part in disease transmission, whilst others will infect many. These latter individuals have become known as the ‘superspreaders’ (Lloyd-Smith et al. 2005).
Previous research has provided evidence of such variation in disease risk in the spread of tuberculosis (TB) in meerkats. Meerkats are susceptible to TB and the disease is a problem in the Kalahari’s resident population. Grooming and aggression behaviours have been shown to be factors in the spread of the disease, and those individuals that engage more in these activities therefore are likely to have an unbalanced involvement in disease spread (Drewe et al. 2011). Although it is hypothesised that targeting control at individuals based upon their roles in disease transmission, this has not been tested empirically.
Study aims and objectives
The aim of this research is to investigate whether an understanding of the network of disease transmission in meerkats can be used to selectively target individuals for interventions, and thus enhance disease control.
The objectives of this research are to:
1. Develop and trial methods to improve the accuracy of TB diagnosis in meerkats in a field setting in order to improve the reliability of the research results.
2. Establish the effectiveness of BCG (bacille Calmette-Guerin) vaccination against TB in meerkats
3. Test the effect of vaccination strategies based on meerkat contact networks against on their ability to reduce disease incidence in a free-living population.
In order to achieve these goals, an initial cross-sectional study of the Kalahari meerkat population will be conducted in 2013-14 in order to gain a greater understanding of the baseline disease situation, and to provide parameters to inform a social network model of disease spread. Alongside this survey, laboratory work will be undertaken to optimise the diagnosis of TB in meerkats.
Based upon these initial results, decisions will be made on vaccination strategies to be trialled, and which individuals should be targeted for interventions. This will form the basis of an ongoing cohort study into the effects of vaccination (2014-16), not only on those individuals, but also upon the incidence of disease in their social groups. Finally, mathematical modelling will be used to produce long-term estimates of the effects of TB in the population, taking into account individual and group level risk factors, and the effects of any vaccination protocol that may be put in place.
Ethical and research permission from the relevant South African and British authorities will be obtained before the study commences.
Results from this work are expected to be not only of benefit to the population of meerkats under study (by helping us to understand and potentially reduce TB levels), but also to provide empirical evidence on the impact of targeted TB control in a wild mammal population. This is likely to be of use to people working with TB in other wildlife species, such as badgers in the UK, as well as further our understanding of infectious disease control more generally.
This project is funded by the RVC, Friends of the Kalahari Meerkat Project, and the University of Cambridge.
Drewe, J.A., Eames, K.T.D., Madden, J.R. and Pearce, G.P. (2011) Integrating contact network structure into tuberculosis epidemiology in meerkats in South Africa: implications for control. Preventive Veterinary Medicine 101: 113-120.
Lloyd-Smith, J.O., Schreiber, S.J., Kopp, P.E. and Getz, W.M. (2005) Superspreading and the effect of individual variation on disease emergence. Nature 438: 355-359.