Species composition and pyrethroid susceptibility status of Anopheles mosquitoes from two different locations in Malaysia

A 14-months survey was carried out to identify the species composition of Anopheles mosquitoes from Kampung Bongor, Grik, Perak. Adding to that, a preliminary one month mosquito population screening was done at Kampung Tepin, Serian, Sarawak. Consequently, the insecticide susceptibility status of a pyrethroid was tested against two selected species of Anopheles collected from these two locations in Malaysia. A total of 4,497 Anopheles from 11 species were identified from collections in Kampung Bongor, whereas 2,654 An. letifer were collected from Kampung Tepin. The An. maculatus of Kampung Bongor and An. letifer of Kampung Tepin were then selected and tested using WHO standard diagnostic test kits and impregnated papers with 0.75% permethrin. The response values of KT50 and KT95 for An. maculatus were recorded at 28.09 minutes and 62.98 minutes respectively. Anopheles letifer recorded much slower response values of KT50 and KT95, which was at 35.09 minutes and 73.03 minutes respectively. Both An. maculatus and An. letifer showed 100% mortality after 24 hours holding period. The results indicate that both species were still susceptible to the tested pyrethroid. For effective vector control and resistance management, accurate and periodic insecticide resistance monitoring should be undertaken especially in rural areas with agricultural usage of insecticides.

Mass newborn screening for glucose-6-phosphate dehydrogenase deficiency in Singapore.

Recognition of kernicterus as a significant contributor to newborn mortality and morbidity in G6PD deficient babies and the ease with which G6PD deficiency could be detected and kernicterus prevented by avoidance of triggers, led to the establishment of mass newborn screening for G6PD deficiency in 1965. G6PD deficient newborns are identified within a day of birth by measuring the enzyme activity in cord blood. They are then physically protected from triggers by keeping them in the hospital for the first 2 weeks of life after their parents are counseled. Enzyme activity is measured using Wong's in-house modification of the Bernstein's technique or the BM G6PD Deficiency Screening test based on the Beutler assay. Close to 1.6 million newborns, representing practically 100% of all births have been screened. Analysis of data from 22,830 newborns at the National University Hospital reveals an incidence of 1.62% in all newborns. 3.15% in males and and 0.11% in females. A distinct racial variation in the incidence of deficiency was observed in males: Chinese 3.94%, Malays 2.95% and Indians 0.66%. Intermediate deficiency was most frequently identified (1.83%) in Chinese females. With the preventive measures. the incidence of kernicterus has dropped dramatically and there has been, over the last 20 years, no reported cases of kernicterus in newborns with G6PD deficiency. We are now looking at issues like comparing different assay techniques and determining a shorter period of stay in hospital. We believe that all Asians, especially Chinese babies, should be screened for G6PD deficiency, irrespective of which country the child is born.

Newborn screening in Singapore.

Neonatal screening in Singapore for G6PD deficiency started in 1965. Screening for congenital hypothyroidism started in 1981 as a pilot research program and by 1990, it became nationwide. Screening for congenital hypothyroidism is by the measurement of TSH in the cord serum with recall of those exceeding the 99th percentile, by about 3-4 days of life. Treatment is usually started within a week of life. Over 400,000 newborns have been screened and the screening rate has been about 99.95%. The incidence rate is about 1 in 3,000. G6PD activity in the cord blood is measured using semi-quantitative rapid screening tests. Those identified are physically protected from environmental triggers by keeping them in hospital for a variable period of time. Parents are counseled. Data obtained from 22,830 newborns from the National University Hospital revealed incidence rates of 1.62% in all newborns, 3.15% in males and 0.11% in females. The Chinese and Malay males had a higher (3.94% and 2.95%) incidence respectively when compared to the Indian males with (0.66% incidence). The application of the preventive measures has resulted in no report of kernicterus in the last 20 years. Our efforts are now focused on minimizing the recall rate in the case of hypothyroidism screening, reducing the period of stay in hospital in those with G6PD deficiency and considering the introduction of a PKU screening program in Singapore.