When it comes to disease-carrying insects, mosquitoes get all the attention. It is deserved since the malaria they carry caused 198 million cases in 2014 and killed more than 500,000 people. The impact of malaria is widespread and efforts to stop its spread target the mosquitoes that carry it. But there is another pesky insect that causes problems by spreading disease – the tsetse fly.
Found only in the central part of sub-Saharan Africa, the tsetse fly is a carrier of Trypanosomiasis. You might know it better as sleeping sickness. With just 7,216 cases in 2012, sleeping sickness deservedly garners much less attention than malaria. However, the impact of the disease, and specifically the fly that carries it, is significant.
By taking a historical look at progress in Africa, economist Marcella Alsan discovered that there is a significant difference between areas where the tsetse fly were found and areas where they were not. Areas of pre-colonial Africa with greater tsetse fly density saw lower populations and fewer livestock. The impacts continue in the regions until present day.
She developed what she called a tsetse suitability index, or TSI for short, as a measure for the prevalence of the fly in a region. The scores were then matched against indicators like agriculture, institutions and population density. She determined that for each standard deviation the TSI increased there was an associated 23 percent drop in the likelihood of owning large animals, a 9 percent fall in intensive cultivation and 6 percent decline in plow use. It also saw population density decrease by 53 percent.
The more significant affects were that the use of slaves increased in higher TSI areas and political centralization fell. Those are the areas that may be associated with longer term development challenges faced by the affected regions in Africa.
“The findings suggest tsetse-associated disease continues to influence development mainly through its effect on precolonial centralization,” writes Alsan.
Alsan then applied the TSA to current development progress in Africa. She used satellite light density and observed cattle distribution to track. Previous studies have shown that political centralization is an important indicator for development. The effect of the tsetse fly on raising livestock, specifically because of Trypanosomiasis, is believed to have influenced whether people lived in certain parts of Africa and that could have affected the development of institutions.
“The evidence suggests that the relationship between the TSI and satellite lights is driven by the tsetse’s effect on shaping historical institutions, particularly political centralization,” Alsan found.
She is not alone in making the connection between the burden of disease on development progress. The ultimate findings are less about the impact of the tsetse fly than how its prevalence reinforces the importance of precolonial centralization. Aslan is careful in her own conclusions to point out the limitations to her findings. Most notable is the fact that the eventual removal of the fly did not produce a consistent positive result. Though there is still reason to see it as lingering problem.
“Predictions are broadly consistent with the archaeological record which documents that relatively advanced civilizations flourished in areas of Africa inhospitable to the fly,” she concludes. “[The findings] may reflect the continued relevance of tsetse-transmitted Trypanosomiasis on animal husbandry in Africa today.”
HT Ken Opalo