الفهرس 
Methods of detection of bancroftian filariasisOnly 14 pages are availabe for public view
 |  | from | 32 |  |  |
| | | from | 32 | | |
Abstract
The distribution of filariasis in the Nile Delta is described as
prominently focal with spatial clusters of high endemicity villages. Differences in
prevalence between contiguous apparently similar villages where the vector mosquito, Culex pipiens,
is extremely common remains unexplained. The use of vector-based strategies for defining focal
areas and evaluating levels of endemicity is an urgent demand, prior to detailed epidemiological
surveys. Mosquito infection with Wuchereria bancrofii is assessed either by microscopic
examination of filaria or by PCR. In the present study, a DNA-based assay was used to test
whether it detects circulating W bancrofii DNA fragments within Culex pipiens that have ingested
a filaria infected blood meal, but are free of worms upon dissection, at various
intervals post-feeding, and microscopic examination. The W bancrofii specific Ssp
1- PCR-based assay proved positive only when dissected individual mosquitoes contained at least
one living intact filarial worm, indicating that no circulating W bancrofii DNA
fragments within filaria free mosquitoes is detected by this particular assay. The
assay also was used to evaluate relative infection levels between villages by processing
wild-caught mosquitoes from two villages in Qaliubiya Governorate with high (El-Qolzom,
10.8 %) and low (Kafr Shorafa, 2.1%) prevalence of human filariasis. Dry ice-baited CDC light
traps and oviposition traps were used to collect outdoor host seeking and ovipositing Cx.
pipiens, respectively. Mosquitoes resting within houses were collected by aspiration.
Outdoor host-seeking and ovipositing Cx. pipiens were equally abundant in Qol and KSH over a 3-
month period. Density of indoor-resting Cx. pipiens in KSH exceeded by
1.4 fold that in Qol. Overall mosquito abundance did not appear to
contribute to the observed difference in filaria prevalence between Qol and KSH. None of the
outdoor host-seeking, or ovipositing Cx. pipiens, in both Qol and KSH was infected with W
bancrojii, as assessed by both dissection and PCR. Indoor-resting mosquitoes collected from
houses with unknown status of human filariasis (44 in Qol and 37 in KSH) and branded positive by
dissection were far behind (2.3 % and 0.0 respectively) estimations made by Sspl-PCR processing of mosquitoes (31.8% and 8.1%, respectively).
PCR processing of mosquitoes collected from houses with and without microfilaremic residents in
Qol revealed that houses with microfilaremic residents contained more often (60 %) infected
mosquitoes, than houses with no microfilaremic individuals (24
%), confirming the validity of the PCR assay for evaluation of relative filarial prevalence. It is
concluded that PCR screening of pools of mosquitoes represents a useful primary surveillance
method for
·identifying filaria endemic areas, evaluating relative infection rates in
endemic villages, and obtaining an estimate of endemicity and transmission dy1,1amics in villages
of the Nile Delta.