PUBLIC HEALTH IMPACT OF INBREEDING AND GENETIC LOAD IN 35 INBREEDING COMMUNITIES OF KERALA

摘要

The public health impact of inbreeding and genetic load are evaluated and estimated from the data of consanguinity-associated mortality effect in 35 communities of Kerala. The impact is evaluated in terms of two measures of association, the relative risk (RR) and attributable risk (AR); the former ranged from 1.423 to 4.701 and the latter from 0.0283 to 0 4776. Eight association types between inbreeding levels and RRs were recognized and the impact was found to be highest in communities of the Low inbreeding-High RR type, and the lowest in the High-High. The impact is much less among the socio-economically underdeveloped communities. The risk of mortality exclusively due to inbreeding (AR) is negligibly low (<5%) in communities with high levels of inbreeding. The strong positive association between inbreeding rates and ARs noticed in great bulk of the communities is suggestive of little role of long-term inbreeding in eliminating deleterious recessive alleles from their gene pool. The genetic loadswere estimated following the MCM model in units of lethal equivalents based on the values of A and B statistics. The As ranged form 0.0023 to 0.2080, the low values predominating in socio-economically more developed communities, which implies that A isan indicator of better public health exposure. The estimates of B ranged from 0.2584 to 9.117. The extent of variation may be due to difference in inbreeding rates coupled with widely different socio-economic levels. A trend of negative association is evident between inbreeding level and B, which is striking in the underdeveloped Scheduled Caste and Tribal groups. The B/A ratio ranged from 5.50 to 720. In communities with higher B/A (>10), the load element could the mutational and in the others segregational. The estimated numbers of lethal equivalents ranged from 0.5-1 to 9-10. Communities displaying very low numbers (0.5-1, 1-2) should be loaded with fewer number of highly lethal recessive genes, and those with higher numbers, with more number of less lethal genes.