Over the past couple of centuries humans have been forced to evolve to endure with malaria and lactase persistence, being able to drink milk. These are two key factors that have shaped our genomes. Having a predisposed protection against malaria is extremely important, 1.5 million people died from malaria in 2009 alone. Having a resistance against malaria would be beneficial in certain parts of Africa such as in the holoendemic regions of tropical Africa.
Also, having lactase persistence has been beneficial in all cultures that have been able to maintain cattle to obtain milk. Being lactase non-persistence is a genetically normal trait, but genetic mutations have allowed adult humans to tolerate milk lactase. Multiple single polymers have been associated with lactase persistence in the enhancer region.
In the Western Africa these two environmental factors have come together in the traditionally nomadic Fulani people; they are trading people who raise goats and herd cattle. Being lactose tolerant is rare among people of African descent, but the Fulani are an exception. The Fulani have been known to be more resistant to malaria then other surrounding tribes in Western Africa.
Their hypothesis is that they suspect that the dietary habits of the Fulani have an impact on their partial malaria resistance. The Fulani consume vast quantities of milk and are known to drink more milk than other surviving tribes, such as the Dogon. The Dogon also use milk, but not in the quantities of the Fulani. To test this hypothesis the experimenters tested a 400 bp area with the known lactase persistence variants and the relation between malaria and lactase persistence genotypes between the 162 Fulani and 79 Dogon.
The study was carried in rural villages in the Sahelian area in Mali. This area is normally mesoendemic, an area with some transmission, for malaria and is caused by a protozoan that is transmitted to people by the bite of a female mosquito. They have seasonal cases due to the dry and wet seasons. Most of the cases are reported from June until December.
Blood smears of the participants, 162 Fulani and 79 Dogon, were collected and stained with 3% Giemsa and they were compared to the control. The participants had several factors recorded including age, body temperature, and spleen enlargement. Also, the hemoglobin levels and presence of Plasmodium genetic material was tested from blood samples by polymerase chain reaction also there genotypes were assesed. Once this was done the test groups were then compared for chronic malaria infections.
Each of the malaria variables were then grouped into two different categories so chi squared could be used to check for the actual probability of the events happening.
The results, in the correlation between malaria and lactase persistence, CC corresponds to lactase non-persistence, and both CT and TT to lactase persistence. Among the Fulani with the CC genotype 24 % of them had Malaria. This is compared to the 18% with the TT/CT genotype. When tested for P. falciparum, malaria causing bacteria, was positive in 60% of subjects with lactase non-persistence (CC) and in 51% of lactase persistence (CT/TT). The results show that P. falciparum, is more common in individuals that were lactose intolerant, but when chi squared is used the results that were obtained aren’t statistically relevant.
I think this was a good study to conduct because malaria is an extremely prevalent disease in the world. If this disease could be defeated by something as simple as drinking more milk being lactose-tolerant it is always worth a shot.