The Duffy blood groups of Jarawas - the primitive and vanishing tribe of Andaman and Nicobar Islands of India

Andaman and Nicobar Islands, union territory of India were inhabited by 14 aboriginal tribes. Some of these tribal populations have already become extinct, and the numbers of the existing ones are also dwindling. This group of islands being highly endemic for malaria, it was considered worthwhile to study the hunter-gatherer primitive tribe, Jarawas, for their Duffy blood group phenotype. Jarawas, the primitive tribe of Andaman Islands, inhabit the three jungle areas of South and one jungle area of Middle Andaman. Blood samples of 116 Jarawas were collected and tested for Duffy blood group and malarial parasite infectivity. The Duffy blood grouping was performed as per standard serological techniques, and peripheral smears were screened for malarial parasite and if present parasite density count was performed and the species identified. The results showed a total absence of both Fy(a) and Fy(b) antigens in two areas (Kadamtala and R.K. Nallah) and low prevalence of Fy(a) antigen in another two areas (Jirkatang and Tirur). There was absence of malarial parasite Plasmodium vivax infection though Plasmodium falciparum infection was present in 27.59% of cases. A very high frequency of Fy (a-b-) in the Jarawa tribe from all the four jungle areas of Andaman Islands along with total absence of P. vivax infections suggests the selective advantage offered to Fy (a-b-) individuals against P vivax infection.