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

Mark E. J. Woolhouse*, Samuel M Thumbi, Amy Jennings, Margo Chase-Topping, Rebecca Callaby, Henry Kiara, Marinda C. Oosthuizen, Mary N. Mbole-Kariuki, Ilana Conradie, Ian G. Handel, E Jane Poole, Evalyne Njiiri, Nicola E. Collins, Gemma Murray, Miika Tapio, Olga Tosas Auguet, Willie Weir, W. Ivan Morrison, Loeske E. B. Kruuk, B. Mark de C. BronsvoortOlivier Hanotte, Koos Coetzer, Philip G Toye

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

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.
Original languageEnglish
Article numbere1400026
Number of pages10
JournalScience Advances
Issue number2
Publication statusPublished - 20 Mar 2015

Keywords / Materials (for Non-textual outputs)

  • case fatality
  • cattle
  • East Coast fever
  • endemic stability
  • Epidemiology
  • heterologous protection
  • malaria
  • mathematical model
  • Theileria parva
  • vaccination


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