Hoda A. Farid

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.

Detection of Wuchereria bancrofti in mosquitoes by the polymerase chain reaction: a potentially useful tool for large-scale control programmes

Focally endemic bancroftian filariasis is targeted for elimination in the Nile delta of Egypt. Improved methods are needed for identifying endemic villages to be included in the control programme and for monitoring its success. We have evaluated the performance of a polymerase chain reaction (PCR) assay in estimating Wuchereria bancrofti infection in pools of Culex pipiens (1-25 females) from 2 adjacent villages with high (El Qolzom, 10.8%) and low (Kafr Shorafa, 2.1%) prevalence rates of human filariasis. This assay detects a repeated sequence in W. bancrofti deoxyribonucleic acid (DNA). Mosquitoes resting within houses were captured by aspiration and pooled by house. Houses were classified as positive or negative for human filarial infection based on night blood examinations of residents. The assay detected parasite DNA in mosquitoes from 60% of 25 infected houses and 24% of 25 uninfected houses. PCR processing of mosquitoes caught within houses of unknown filariasis infection status (44 in El Qolzom, 37 in Kafr Shorafa) identified 31.8% and 8.1% of houses, respectively, as containing infected mosquitoes. These results support the validity of the PCR assay for evaluating filarial prevalence in different villages. C. pipiens collected outdoors in dry ice-baited traps and tested by PCR (266 in Qolzom, 82 in Kafr Shorafa) did not contain parasite DNA. Pools of female mosquitoes (296 in Qolzom, 240 in Kafr Shorafa) captured in oviposition traps were also negative. We concluded that the PCR based assay is a powerful epidemiological tool that can be used for evaluating W. bancrofti infection in villages in the Nile delta and for monitoring the application of control programmes in filariasis endemic areas.

Culex pipiens pipiens: characterization of immune peptides and the influence of immune activation on development of Wuchereria bancrofti

Stimulating or augmenting the innate immune response of insect vectors has been shown to impede or disrupt the development and transmission of eukaryotic pathogens; however, the majority of such studies have utilized model systems and not natural parasite-vector systems. The Culex pipiens complex of mosquitoes functions as a primary urban vector of Wuchereria bancrofti, a causative agent of lymphatic filariasis. To test the effects of immune activation on this vector-parasite interaction, Culex pipiens pipiens from the filariasis-endemic Nile Delta were subjected to bacteria inoculation and subsequently fed a blood meal containing W. bancrofti. No difference was seen between parasite development in these mosquitoes as compared to non-inoculated controls. A set of expressed sequence tags from blood-fed midgut and bacteria-inoculated Cx. p. pipiens reveals transcripts for the immune peptides cecropin, gambicin and defensin--all of which have been reported to have antiparasitic effects. Sequences and transcriptional profiles for these peptides are reported. The discrepancy between these results and those reported for the model parasite, Brugia malayi, in the mosquito Aedes aegypti are discussed.

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.

Innate Cellular Immune Responses in Aedes caspius (Diptera: Culicidae) Mosquitoes

Abstract Mosquitoes transmit a variety of pathogens that have devastating consequences for global public and veterinary health. Despite their capacity to serve as vectors, these insects have a robust capacity to respond to invading organisms with strong cellular and humoral immune responses. In Egypt, Aedes caspius (Pallas, 1771) has been suspected to act as a bridge vector of Rift Valley Fever virus between animals and humans. Microscopic analysis of Ae. caspius hemolymph revealed the presence of phagocytic cells called granulocytes. We further evaluated cellular immune responses produced by Ae. caspius as a result of exposure to a Gram-negative, and Gram-positive bacterium, and to latex beads. After challenge, a rapid and strong phagocytic response against either a natural or synthetic invader was evident. Hemocyte integrity in bacteria-inoculated mosquitoes was not morphologically affected. The number of circulating granulocytes decreased with age, reducing the overall phagocytic capacity of mosquitoes over time. The magnitude and speed of the phagocytic response suggested that granulocytes act as an important force in the battle against foreign invaders, as has been characterized in other important mosquito vector species.

Biochemical key to eight species of adult Egyptian mosquitoes

Abstract. 1 An electrophoretic key is described, based on enzyme relative mobility, to distinguish eight species of Egyptian mosquito adults. 2 Using horizontal starch gel electrophoresis, five different enzyme assays unambiguously separated Culex pipiens L., Cx antennatus (Becker), Cx pusillus Macquart, Aedes caspius (Pallas), Culiseta longiareolata (Macquart), Uranotaenia ungukulata Edwards, Anopheles multicolor Cambouliu and An.pharoensis Theobald. 3 Diagnostic loci between species were: Ak‐2, G6pcL a‐Gpd, Gpi and 6‐Pgd; the probability of correct diagnosis in each case was at least 0.989.