Absence of mating barriers between autogenous and anautogenous culex pipiens L in Egypt

The existence of premating and post-mating barriers between Culex pipiens L. population and the possibility of interbreeding between autogenous and anautogenous mosquitos were examined. Tested mosquito populations were stenogamous with >83% insemination rates in 20 x 20 x 20 cm cages, regardless of autogeny rates ranging from 10 to 91%. Bi-directional crosses between 3 geographical populations resulted in > 80% hatch rates, indicating full cytoplasmic compatibility. Both autogenous and anautogenous Cx. pipiens individuals were encountered in the progenies of autogenous or anautogenous female parents. Moreover, more than 75% of field caught females produced mixed progenies. Thus, this work suggested that there is no limitation for hybridization between Cx. pipiens mosquitos in Egypt due to the lack of premating and post-mating barriers

Exposure variables in bancroftian filariasis in the Nile Delta

To demonstrate focality of filariasis within endemic rural areas and to define exposure variables which may influence this phenomenon, the population of an agrarian endemic village, of 12,500 individuals, in the Nile Delta of Egypt was censused. A sequential sample of individuals residing in every 5th house was tested for microfilaremia 239 households with 8.6 +/- 3.5 individuals per household [HHD]. Three areas of the village were tested simultaneously and a questionnaire was filled out for each sampled HHD with special emphasis given to the entomological and environmental factors that might affect filarial infection

Effect of juvenile hormone and ecdysone on initiating blood meal-dependent vitellogenic ovarian cycles in autogenous and anautogenous culex pipiens [Diptera: culicidae]

The effect of juvenile hormone [JH] and ecdysone on initiating blood meal - stimulated ovarian cycles was studied in autogenous [2[nd] ovarian cycle] and anautogenous [1[st] ovarian cycle] Cx. pipiens. Although vitellogenesis was initiated in both mosquitoes in response to ecdysone, JHI and sequential JHI-ecdysone treatments induced vitellogenesis in anautogenous females only. JHI treatment initiated vitellogenesis in Ca. 30% of anautogenous females and only half of those were able to form mature eggs. Sequential JHI- ecdysone treatment triggered vitellogenesis in 10 out of 25 anautogenous females and mature eggs were formed in three females only. In response to ecdysone, vitellogenesis in 10 out of 18 autogenous females and mature eggs were formed in two individuals. In Ca. 70% of anautogenous siblings vitellogenesis was initiated and in most of those females mature eggs were developed. Our data suggests that differences in hormone - dependent events of vitellogenesis in autogenous and anautogenous Cx. pipiens seem to be related to the regulation of ecdysteroide release

In vitro transmission of Wuchereria bancrofti L3-stage larvae by experimentally infected culex pipiens L [Diptera: culicidae]

Females of Culex pipiens L. experimentally infected with Wuchereria bancrofti were tested for in vitro transmission of infective stage L[3] larvae using a capillary tube technique. Of the females harbouring L[3] larvae, 60.7% [34/56] transmitted a geometric mean of 2.84 L[3] larvae [range 1- 35]. Transmitting Cx. pipiens contained significantly more L[3] larvae than non-transmitters. Both the probability of transmission and the number of L[3] larvae transmitted were related to the total number of L[3] larvae/mosquito. Almost all females with L[3] loads >/= 10 transmitted larvae in vitro. The possibility is discussed that the detection of L[3] larvae in field collected mosquitoes by dissection may overestimate the proportion capable of parasite transmission and the proportion of L[3] larvae deposited on host skin by Ca. 40%

Vector competence of autogenous and anautogenous culex pipiens mosquitoes for wuchereria bancrofti

Vector competence of autogenous and anautogenous Culex pipiens derived from North Sinai Governorate, Egypt, for the human filaria parasite Wuchereria bancrofti was studied. After feeding on the same microfilaremic volunteers both biotypes were readily infected with the parasite [infection rates > 80%] and supported its development to the infective stage within 11 - 12 days. Infective rates of both autogenous and anautogenous mosquitoes were similar [> 95%]. However, autogenous Cx. pipiens developed significantly less number of infective stage larvae [4.7 +/- 1.4 1.3 / female] than did anautogenous siblings [6.7 +/- 3.6 L[3]/ female] [P < 0.05]. Moreover, autogenous females were observed to contain twice the number of L[3] larvae in the thoracic muscles and less larvae in the head region compared to autogenous counterparts. Vector competence characteristics of Cx. pipiens derived from a filariasis endemic area in Qalubiya Governorate were similar to those of anautogenous mosquitoes of North Sinai. These findings indicate that autogenous Cx. pipiens may be less efficient vector of W. bancrofti in endemic areas of Egypt

Estimates of Egyptian culcine longevity in nature altered by fluctuations in biting population density

Estimates of vectorial capacity [VC] depend upon longevity of mosquito field populations, and expected longevity is estimated from the parity rate of the population. Seasonal variation in parity rates confound estimates of longevity which may not reflect actual population survival but are induced by changes in the rate of emergence of female mosquitoes. By comparing parity rates and biting activity in natural population of 2 Culicine mosquitoes, Culex pipiens and Cx. antennatus, we found that parity rate was low in the beginning of the season and high at the end. Parity rate appeared least affected during the weeks with maximal daily biting activity. We conclude that estimates of VC are most accurately determined for the two vector species studied when mosquito biting activity is maximal

Facultative blood-feeding by nulliparous autogenous Egyptian aedes caspius pallas [diptera: culicidae]

Facultative blood-feeding, in which nulliparous autogenous Aedes caspius females imbibed blood from a human host before laying their first egg batch, was compared in various geographic populations under laboratory conditions. It accounted for about 39% in the populations tested [range: 27 - 54%]. Temporal blood-feeding activity studies demonstrated that nulliparous autogenous females were liable to ingest blood from 1 to 6 days postemergence, although most females elected to feed when 2 or 3 days old. Ovarian development, determined at the time of blood-feeding, varied from Christopher's stage II B to stage V indicating that vitellogenesis did not inhibit blood-feeding and that the degree of maturation of the ovaries was not a limiting factor to blood-feeding of autogenous females. However significant population differences regarding ovarian stage at the time of blood ingestion were observed. Most autogenous females were half blood-fed regardless the degree of maturation of their follicles. It seems likely that many nulliparous autogenous Ae. caspius will not delay their initial blood meal until they have laid their autogenous egg batch, this would result in early repeated host seeking attempts by these mosquitoes, thereby increasing their vectorial capacity

Bi-autogenous ovarian cycles in Egyptian aedes caspius pallas [Diptera: culicidae]

Autogenous Aedes [Ochlerotatus] caspins Pallas from Aswan deposits 1 to 2 egg batches without a blood meal. Repeated ovarian developmental cycles were responsible for the bi-ovipositional pattern as indicated by the presence of 2 dilatations in the ovariolar pedicel of bi-autogenous females and by the early stages of development of the ovaries [II and II B] observed 1-3 days following initial oviposition, later stages of maturation occurred progressively. Three levels of autogeny were distinguished within the population: mono-autogenous females that deposited 1 egg batch and were unable to initiate further oogenesis [54.4%], mono-autogenous females in which various degrees of vitellogenesis developed posterior to initial sole oviposition [40%] and bi-autogenous females [5.6%] that deposited 2 autogenous egg batches but were unable to develop any further oogenesis. The fecundity of mono-autogenous females [about 56 eggs] whether they could develop a 2nd autogenous cycle or not, was comparable to that of bi-autogenous mosquitoes in their initial egg batch [53 eggs], suggesting that ability to develop a subsequent autogenous follicular cycle is determined by factors independant of nutrient reserves accumulated during the larval stage. The 2nd egg batch of bi-autogenous females was smaller [21 eggs] than the initial batch. The total reproductive effort of bi-autogenous individuals [about 74 eggs] was superior to that of mono-autogenous females. However, bi-autogenous females laid the totality of their eggs within about 16 days, whereas the average initial gonotrophic cycle of mono-autogenous females was 6 days. It is concluded that bi-autogeny in Ae. caspius would be of little value in the population increase although it may contribute maintaining the species when the host is not available

Transmission of rift valley fever virus by different geographic strains of culex pipiens in Egypt

Previous investigations have delt with colonized Cx. pipiens and RVF virus interactions. This study evaluated the vector competence of parental Cx. pipiens populations for RVF virus and investigated variations in the vector competence among different geographic strains of this mosquito in Egypt. Cx. pipiens females were fed on viremic hamsters circulating 9.4 - 10.5 log[10] SMICLD[50] of virus. Mosquito samples were freezed at different intervals extending between 0-12 days of extrinsic incubation [E1].Transmission experiments started at day 5 of E1 when individual females were allowed to refeed on normal hamsters. The infection rates for the geographic strains tested ranged between 85% and 100% and the transmission rates ranged between 6% and 35%.Transmission of RVF virus to normal hamsters took place at days 9, 12, 15 and 18 of E1 by the different tested Cx. pipiens strains. Transmitter females contained significantly more virus than the non-transmitters except for the strain of Giza. Most of the infected Cx. pipiens individuals were of the non-transmitting type even those with high titers. Barriers at the salivary gland level competing RVF virus transmission are probably present in Egyptian Cx. pipiens. RVF virus infection was observed to adversly affect Cx pipiens. The present investigation revealed no geographic variations in the vector competence of Egyptian Cx. pipiens for RVF virus

Distribution and bionomics of Egyptian culex univittatus [Theobald]

Culex univittatus is widespread throughout Egypt. It is most common in southern Egypt where it is generally found throughout the year. In the Nile Delta its presence is restricted to the warmer months. Breeding sites are generally restricted to cultivated areas, especially in fresh water found in drains, irrigation channels seepage water and flooded rice fields. Cx. univittatus is exophagic and endophagic in Sharqiyia and Qalubiyia Governorates. It bites human as well as animals. It is long lived in the field and exceeds the extrinsic incubation period of arboviruses and human filaria, both of which have been found in field-Caught females. It therefore has a high vectorial capacity, rendering the mosquito important in the ecology of human and animal diseases in Egypt

colonization and biology of Egyptian culex univittatus [theobald]

Culex univittatus has been associated with several diseases in Egypt; however, its colonization procedures have not been described nor has its life cycle been studied in the laboratory. We found that all stages of this mosquito could be transported successfully over long distances in twilly bags stored in cooled water in a thermos. Immature stages survived well in distilled water and adult females fed on immobilized pigeon as well as giunea pigs and people. Fecundity was variable. Two third of eggs hatched when derived from the first gonotrophic cycle but this decreased in later gonotrophic cycles. Adult females were long lived and passed through several gonotrophic cycles. Blood feeding began one day after oviposition. Colonization will enable further study of this potential disease vector

distribution and ecology of the mosquitoes in the Red Sea Governorate, Egypt

A survey of the mosquito fauna was conducued in the Red Sea Governorate [RSG], Egypt. Eight mosquito species were found and their distribution and ecology investigated. Culex pipiens and Aedes caspius were common in urban areas while a malaria vector, Anopheles sergentii was found in a single restricted area. A. detritus was found for the first time in the RSG. No Cx. quinquefasciatus were found, indicating that the overlap between Cx. pipiens and Cx. quinquefasciatna probably occurs south of this area. Larval habitats are described for the various mosquitoes and the potential for these mosquitoes in disease transmission is discussed

Ecology of anopheles [cellia] sergent II theiobald in the Eastern Desert, Red sea Governorate, Egypt

During a mosquito survey of the inland water sources of the Red Sea Governorate, several larvae and pupae of Anopheles sergentii were collected from a breeding place located 8 km west of El-Quseir town in the Eastern Desert. This finding represents the south-eastern most boundary for this species in Africa. A full description of the ecology of the recorded area as well as of the breeding place is given in this study. In addition, preliminary laboratory observations indicated that An. sergentii females were able to oviposit both fertile and infertile eggs in small cages. This may indicate that this species consisted of stenogamous and eurygamous subpopulations

Reproductive history of anopheles coustani var tenebrous [Doniz] in the laboratory

Field caught Anopheles tenebrosus have been observed to contain few relics on their follicles indicating that they obtained few blood meals. To determine whether these mosquitoes obtains few blood meals or are short lived, we determined the number of gonotrophic cycles for this mosquito. Parental females were used to simulate natural population. We found that these mosquitoes could produce up to 8 gonotrophic cycles, indicating that the field observations is due to limited longevity. In addition, fecundity was maximal initially and decreased with subsequent gonotrophic cycles. Some females required two blood meals to develop a batch of eggs this did not appear to be correlated with the size of the blood meal