Evaluation of PCR-ELISA as a tool for monitoring transmission of Wuchereria bancrofti in District of Gampaha, Sri Lanka

<p><b>OBJECTIVE</b>To compare Wuchereria bancrofti (W. bancrofti) infection rates of Culex quinquefasciatus, using dissection and PCR-ELISA in two consecutive time periods (from 2007 to 2008 and from 2008 to 2009).</p><p><b>METHODS</b>Mosquitoes were collected in 30 sentinel and 15 non-sentinel sites in 15 Medical Officer of Health areas of Gampaha District known for the presence of W. bancrofti transmission in two consecutive time period of 2007 to 2008 and 2008 to 2009. Captured mosquitoes were dissected to determine the W. bancrofti larvae (L1, L2, L3). PCR was carried out using DNA extracted from mosquito pools (15 body parts/pool) utilizing the primers specific for Wb-SspI repeat. PCR products were analyzed by hybridization ELISA using fluorescein-labeled wild type specific probes. The prevalence of infected/infective mosquitoes in PCR pools (3 pools/site) was estimated using the PoolScreen™ algorithm and a novel probability-based method.</p><p><b>RESULTS</b>Of 45 batches of mosquitoes dissected, W. bancrofti infected mosquitoes were found in 19 and 13 batches, with an infection rate of 13.29% and 3.10% with mean larval density of 8.7 and 1.0 larvae per mosquito for two study periods in the Gampaha District. Total of 405 pools of head, thorax and abdomen were processed by PCR-ELISA for each year. Of these, 51 and 31 pools were positive for W. bancrofti in the two study periods respectively. The association of dissection based prevalence rates with PCR based rates as determined by the Pearson correlation coefficient were 0.176 and 0.890 respectively for the two periods.</p><p><b>CONCLUSIONS</b>Data indicate that PCR-ELISA is more sensitive than the traditional dissection techniques for monitoring transmission intensity.</p>

Impact of helminth infection on childhood allergic diseases in an area in transition from high to low infection burden

BACKGROUND: The effect of helminth infections on allergic diseases is still inconclusive. Furthermore, the effect of helminth infections on childhood allergic diseases in a tropical area where prevalence of helminth infections has undergone dramatic changes is not well documented. OBJECTIVE: To investigate the relationship between allergic diseases and helminth infection in a cohort of schoolchildren in an area that has undergone dramatic changes in intensity of helminth infections. METHODS: Children attending grade 5 were recruited from 17 schools in Western Province of Sri Lanka. They were assessed for allergic diseases using the International Study of Asthma and Allergies in Childhood questionnaire. Their serum total IgE (tIgE) and allergen-specific IgE (sIgE) for five common aeroallergens were measured by ImmunoCAP® method and stools were examined for the presence of helminth infections. RESULTS: A total of 640 children (mean age 10 years) were recruited to the study. Of them, 33.7% had evidence of allergic disease and 15.5% had helminth infections. Majority of infections (68.9%) were of low intensity. A significant relationship between allergic disease and helminth infections was not observed, however, a trend toward protective role of helminth infections against allergic diseases was noted. Multivariate analysis showed helminth infections to be an independent predictor of high tIgE levels whereas allergic disease was not. Allergic sensitization (atopy) was a significant risk factor for allergic disease only among non-infected children (odds ratio 3.025, p = 0.022) but not in infected children. The ratio of sIgE to tIgE was higher in non-infected children. CONCLUSION: Though not significant, a reduced risk of allergy in helminth-infected children was observed in this population. A Decrease in intensity of helminth infections may have contributed to the reduced capacity of immune-modulation by helminths in this paediatric population.