Co-infections determine patterns of mortality in a population exposed to parasite infection

Woolhouse, M. E. J. et al. (2015) Co-infections determine patterns of mortality in a population exposed to parasite infection. Science Advances, 1(2), e1400026. (doi: 10.1126/sciadv.1400026) (PMID:26601143) (PMCID:PMC4643819)

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Many individual hosts are infected with multiple parasite species, and this may increase or decrease the pathogenicity of the infections. This phenomenon is termed heterologous reactivity and is potentially an important determinant of both patterns of morbidity and mortality and of the impact of disease control measures at the population level. Using infections with Theileria parva (a tick-borne protozoan, related to Plasmodium) in indigenous African cattle [where it causes East Coast fever (ECF)] as a model system, we obtain the first quantitative estimate of the effects of heterologous reactivity for any parasitic disease. In individual calves, concurrent co-infection with less pathogenic species of Theileria resulted in an 89% reduction in mortality associated with T. parva infection. Across our study population, this corresponds to a net reduction in mortality due to ECF of greater than 40%. Using a mathematical model, we demonstrate that this degree of heterologous protection provides a unifying explanation for apparently disparate epidemiological patterns: variable disease-induced mortality rates, age-mortality profiles, weak correlations between the incidence of infection and disease (known as endemic stability), and poor efficacy of interventions that reduce exposure to multiple parasite species. These findings can be generalized to many other infectious diseases, including human malaria, and illustrate how co-infections can play a key role in determining population-level patterns of morbidity and mortality due to parasite infections.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Weir, Professor Willie
Authors: Woolhouse, M. E. J., Thumbi, S. M., Jennings, A., Chase-Topping, M., Callaby, R., Kiara, H., Oosthuizen, M. C., Mbole-Kariuki, M. N., Conradie, I., Handel, I. G., Poole, E. J., Njiiri, E., Collins, N. E., Murray, G., Tapio, M., Auguet, O. T., Weir, W., Morrison, W. I., Kruuk, L. E. B., Bronsvoort, B. M. d. C., Hanotte, O., Coetzer, K., and Toye, P. G.
College/School:College of Medical Veterinary and Life Sciences > Institute of Biodiversity Animal Health and Comparative Medicine
Journal Name:Science Advances
Publisher:American Association for the Advancement of Science
ISSN (Online):2375-2548
Copyright Holders:Copyright © 2015 The Authors
First Published:First published in Science Advances 1(2):e1400026
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
508691Understanding the basis of strain restricted immunity to Theileria parvaBrian ShielsBiotechnology and Biological Sciences Research Council (BBSRC)BB/H009515/1III - PARASITOLOGY