DNA technology provides a new avenue to perform neonatal screening tests for single-gene diseases in populations of high frequency. Thalassemia is one of the high-frequency single-gene disorders affecting Singapore and many countries in the malaria belt. The authors explored the feasibility of using PCR-based diagnostic screening on 1,116 unselected sequential cord blood samples for neonatal screening. The cord blood samples were screened for the most common reported alpha- and beta-thalassemia mutations in each ethnic group (Chinese, Malays, and Indians) in a multiracial population. The carrier frequency for alpha-thalassemia mutations was about 6.4% in the Chinese (alpha deletions = 3.9%, alpha deletions = 2.5%), 4.8% in Malays, and 5.2% in Indians. Only alpha deletions were observed in the Chinese. The carrier frequency for beta-thalassemia mutations was 2.7% in the Chinese, 6.3% in Malays, and 0.7% in Indians. Extrapolating to the population distribution of Singapore, the authors found a higher overall expected carrier frequency for alpha- and beta-thalassemia mutations of 9% compared with a previous population study of 6% by phenotype. The highly accurate results make this molecular epidemiologic screening an ideal method to screen for and prevent severe thalassemia in high-risk populations.
Logged and disturbed forests are often viewed as degraded and depauperate environments compared with primary forest. However, they are dynamic ecosystems1 that provide refugia for large amounts of biodiversity2,3, so we cannot afford to underestimate their conservation value4. Here we present empirically defined thresholds for categorizing the conservation value of logged forests, using one of the most comprehensive assessments of taxon responses to habitat degradation in any tropical forest environment. We analysed the impact of logging intensity on the individual occurrence patterns of 1,681 taxa belonging to 86 taxonomic orders and 126 functional groups in Sabah, Malaysia. Our results demonstrate the existence of two conservation-relevant thresholds. First, lightly logged forests (<29% biomass removal) retain high conservation value and a largely intact functional composition, and are therefore likely to recover their pre-logging values if allowed to undergo natural regeneration. Second, the most extreme impacts occur in heavily degraded forests with more than two-thirds (>68%) of their biomass removed, and these are likely to require more expensive measures to recover their biodiversity value. Overall, our data confirm that primary forests are irreplaceable5, but they also reinforce the message that logged forests retain considerable conservation value that should not be overlooked.