Hanan Helmy

Effect of yearly mass drug administration with diethylcarbamazine and albendazole on bancroftian filariasis in Egypt: a comprehensive assessment

BACKGROUND Egypt was one of the first countries to implement a national programme to eliminate lymphatic filariasis based on WHOs strategy of repeated rounds of mass drug administration (MDA) with diethylcarbamazine and albendazole (target population, 2.5 million in 181 localities). We assessed the effect of five yearly rounds of MDA on filariasis in four sentinel villages in Egypt. METHODS We studied two areas with different infection rates before MDA: the Qalubyia study area had a low infection rate because of previous treatment with diethylcarbamazine; this was typical of most filariasis-endemic villages in Egypt before MDA. The Giza study area had a high baseline infection rate. We undertook repeated surveys in villages for treatment compliance and tests for microfilaraemia and circulating filarial antigenaemia, antibodies to filarial antigen Bm14 in schoolchildren, and infections in indoor-resting mosquitoes (assessed by PCR). FINDINGS MDA compliance rates were excellent (>80%). In Giza after MDA, prevalence rates of microfilaraemia and circulating filarial antigenaemia fell from 11.5% to 1.2%, and from 19.0% to 4.8%, respectively (p<0.0001). Corresponding rates in Qalubyia fell from 3.1% to 0% and 13.6% to 3.1%, respectively (p<0.0001). Rates of antifilarial antibody and circulating filarial antigenaemia in schoolchildren (aged about 7-8 years), fell from 18.3% to 0.2% (p<0.0001) and from 10.0% to 0.4% (p<0.0001) in Giza, respectively, and from 1.7% to 0% and 1.7% to 0% (both p=0.13) in Qalubyia, respectively. Mosquito infection rates fell from 3.07% (95% CI 2.38-3.88) to 0.19% (0.08-0.38) in Giza and from 4.37% (3.07-5.99) to 0% (0-0.05) in Qalubyia. INTERPRETATION MDA greatly affects variables related to infection (microfilaraemia and circulating filarial antigenaemia prevalence rates) and transmission (antifilarial antibodies in young children and mosquito infection rates). Our results suggest that after five rounds of MDA filariasis is likely to have been eliminated in most endemic localities in Egypt.

Development and standardization of a rapid, PCR-based method for the detection of Wuchereria bancrofti in mosquitoes, for xenomonitoring the human prevalence of bancroftian filariasis.

PCR has recently been studied as a promising tool for monitoring the progress of efforts to eliminate lymphatic filariasis. PCR can be used to test concurrently at least 30 pools, with as many as 40 mosquitoes in each pool, for the presence of filarial larvae. The SspI PCR assay for the detection of Wuchereria bancrofti DNA in pools of mosquitoes has been used since 1994 in a variety of laboratories worldwide. During that time, the original assay has been modified in these different laboratories and no standardized assay currently exists. In an effort to standardize and improve the assay, a meeting was held on 15-16 November 2001, at Emory University in Atlanta, with representatives from most of the laboratories currently using the assay. The first round of testing was designed to test the four most promising methods for DNA extraction from pools of mosquitoes. Two of the four methods stood out as clearly the best and these will be now optimised and evaluated in two further rounds of testing.

Transcriptome Changes in Culex quinquefasciatus (Diptera: Culicidae) Salivary Glands During West Nile Virus Infection

ABSTRACT Persistent West Nile virus (WNV) infection in the mosquito Culex quinquefasciatus Say (Diptera: Culicidae) is associated with pathological changes in the salivary glands, including apoptotic cell death and a corresponding reduction in virus transmission over time. The vector host response to WNV infection and the molecular basis of WNV pathogenesis in Cx. quinquefasciatus was investigated using oligonucleotide microarrays designed to detect differences in the salivary gland transcriptome between WNV-infected mosquitoes and uninfected controls. Transcripts with increased abundance in infected salivary glands included those related to immunity, transcription, protein transport and degradation, amino acid and nucleotide metabolism, signal transduction, and cellular detoxification. Microarray-based analysis detected a decrease in transcript levels of a Culex inhibitor of apoptosis gene (IAP-1) and a decrease in abundance of 11 transcripts encoding salivary gland proteins, Transcript levels for an endonuclease, a proline-rich mucin, and several D7 protein family members also decreased. Transcripts with the greatest change in abundance during infection had either no similarity to sequences found in GenBank, VectorBase, and FlyBase, or were similar to sequences with uncharacterized protein products. These transcripts represent exciting targets for future analysis. Results from this study suggest that WNV infection influences transcriptional changes in an invertebrate host target tissue that may confer an advantage to the replicating virus, induce a host defense response, and alter the composition of vector saliva. The ramifications of these changes are discussed in terms of mosquito vector competence and WNV pathogenesis.

Test strip detection of Wuchereria bancrofti amplified DNA in wild‐caught Culex pipiens and estimation of infection rate by a PoolScreen algorithm

Bancroftian filariasis is targeted for elimination in the Nile Delta of Egypt. Improved simple methods are needed for monitoring Wuchereria bancrofti infection in the mosquito vector and thereby the success of elimination programmes. We evaluated the performance of the SspI‐PCR assay combined with a DNA Detection Test StripTM method and used the PoolScreen algorithm method for estimating mosquito infection rates. A total of 769 indoor‐resting Culex pipiens were captured in 79 randomly selected houses from a filaria‐endemic village in the Nile Delta of Egypt (24.4% antigenaemia and 8.6% microfilaraemia). Collected mosquitoes were pooled by house, and assayed by the SspI‐PCR. Amplified parasite DNA was detected by both electrophoresis of agarose gel stained with ethidium bromide (EtBr) and by test strips. PCR based on EtBr and test strip methods identified 43 (54.4%) and 45 (56.9%) houses, respectively, as being filaria positive. The minimum mosquito infection rate, assuming one infected female/pool was 6.85% by the PCR test strips. Mosquito infection rate calculated by the PoolScreen2 algorithm software amounted to 8.1% [95% confidence interval 5.85, 10.47]. Because it is faster and safer, the PCR test strip is a practical tool, especially when combined with the PoolScreen algorithm method, for xenomonitoring the success of elimination programmes.

Detection of Wuchereria bancrofti L3 larvae in mosquitoes: a reverse transcriptase PCR assay evaluating infection and infectivity.

Background Detection of filarial DNA in mosquitoes by PCR cannot differentiate infective mosquitoes from infected mosquitoes. In order to evaluate transmission risk an assay is needed that can specifically detect infective L3 stage parasites. We now report the development of an assay that specifically detects the infective stage of Wuchereria bancrofti in mosquitoes. The assay detects an L3-activated mRNA transcript by reverse-transcriptase PCR (RT-PCR). Methodology/Principal Findings W. bancrofti cuticle-related genes were selected using bioinformatics and screened as potential diagnostic target genes for L3 detection in mosquitoes. Expression profiles were determined using RT-PCR on RNA isolated from mosquitoes collected daily across a two-week period after feeding on infected blood. Conventional multiplex RT-PCR and real-time multiplex RT-PCR assays were developed using an L3-activated cuticlin transcript for L3 detection and a constitutively expressed transcript, tph-1, for ‘any-stage’ detection. Conclusions/Significance This assay can be used to simultaneously detect W. bancrofti infective stage larvae and ‘any-stage’ larvae in pooled vector mosquitoes. This test may be useful as a tool for assessing changes in transmission potential in the context of filariasis elimination programs.

An enzyme‐linked immunosorbent assay for detection of IgG1 antibodies specific to human cystic echinococcosis in Egypt

Summary Human cystic hydatidosis (cystic echinococcosis) is a chronic zoonotic disease that results from infection with the dog tapeworm Echinococcus granulosus. In Egypt, cystic echinococcosis (CE) is recognized in slaughtered livestock by veterinarians, however, there is little information about human CE infection rates. We describe an immunological assay useful for the diagnosis of human cystic hydatidosis. Sera were collected from surgically confirmed hydatid cases (34), nonendemic subjects free from parasitic infection (20) and from subjects (109) infected with other helminths (Hymenolepis nana, Schistosoma mansoni, Fasciola hepatica and Ancylostoma duodenale). Hydatid cyst fluid (HCF) of camel origin was used as antigen in an ELISA format to measure total E. granulosus specific IgG antibodies and IgG subclasses. Sensitivity measurements of total IgG, and IgG1–4 were 100, 100, 79.4, 61.8 and 55.9%, respectively, whereas respective specificity reached 65.1, 97.7, 98.4, 96.1 and 83.7%. The diagnostic value of measuring IgG1 (97.7%), as assessed by a rating index (J) for combined sensitivity and specificity, was superior to total IgG (65.1%) and IgG2–4 (77.8, 57.9 and 39.6%, respectively). These findings set the stage for field evaluation of the IgG1 assay in areas endemic with human cystic hydatidosis.