Research

Consanguineous marriages and endemic malaria: can inbreeding increase population fitness?

Srdjan Denic¹ , Nicolas Nagelkerke^2,4 and Mukesh M Agarwal³

¹Department of Internal Medicine, Faculty of Medicine and Health Sciences, UAE University, PO Box 17666, Al Ain, Abu Dhabi, UAE

²Department of Community Medicine, Faculty of Medicine and Health Sciences, UAE University, PO Box 17666, Al Ain, Abu Dhabi, UAE

³Department of Pathology, Faculty of Medicine and Health Sciences, UAE University, PO Box 17666, Al Ain, Abu Dhabi, UAE

⁴Department of Medical Microbiology and Infectious Diseases, University of Manitoba, 730 William Avenue, MB, R3E 0W3,Winnipeg, Canada

author email corresponding author email

Malaria Journal 2008, 7:150doi:10.1186/1475-2875-7-150

Published:	2 August 2008

Abstract

Background

The practice of consanguineous marriages is widespread in countries with endemic malaria. In these regions, consanguinity increases the prevalence of α⁺-thalassemia, which is protective against malaria. However, it also causes an excessive mortality amongst the offspring due to an increase in homozygosis of recessive lethal alleles. The aim of this study was to explore the overall effects of inbreeding on the fitness of a population infested with malaria.

Methods

In a stochastic computer model of population growth, the sizes of inbred and outbred populations were compared. The model has been previously validated producing results for inbred populations that have agreed with analytical predictions. Survival likelihoods for different α⁺-thalassemia genotypes were obtained from the odds of severe forms of disease from a field study. Survivals were further estimated for different values of mortality from malaria.

Results

Inbreeding increases the frequency of α⁺-thalassemia allele and the loss of life due to homozygosis of recessive lethal alleles; both are proportional to the coefficient of inbreeding and the frequency of alleles in population. Inbreeding-mediated decrease in mortality from malaria (produced via enhanced α⁺-thalassemia frequency) mitigates inbreeding-related increases in fatality (produced via increased homozygosity of recessive lethals). When the death rate due to malaria is high, the net effect of inbreeding is a reduction in the overall mortality of the population.

Conclusion

Consanguineous marriages may increase the overall fitness of populations with endemic malaria.