Sherif El Said

Bio: Sherif El Said is an academic researcher from Ain Shams University. The author has contributed to research in topics: Culex pipiens & Culex. The author has an hindex of 8, co-authored 9 publications receiving 230 citations.

The Effect of Laboratory Colonization on the Vector-Pathogen Interactions of Egyptian Culex pipiens and Rift Valley Fever Virus

Abstract: : Field and laboratory findings implicated Culex pipiens as a vector of Rift Valley fever (RVF) virus during the 1977-1978 epizoodtics/epidemics in Egypt. This study evaluated changes in infection and transmission rates, and viral titters in F sub 1 through F sub 16 generation Cx. pipiens mosquitoes orally infected with RVF virus. Infection and transmission rates of RVF virus by this species changed significantly during the colonization process. However, the ultimate viral titers of either the transmitting or the infected nontransmitting mosquitoes were not affected by the colonization process. Following ingestion of virus, Cx. pipiens could be separated into three distinct subpopulations, an uninfected group and two types of infected mosquitoes - transmitters and nontransmitters. Transmitters contained significantly more virus (approximately 100-fold) than nontransmitters. These results demonstrated that not every infected female mosquito should be considered a competent vector, even if the species (population) is known to be a primary vector. Transmission was also accomplished by probing mosquitoes which were unsuccessful in obtaining a blood meal. These data document the long-held suspicion that vector competence studies based upon laboratory-colonized specimens may not represent the field situation.

Arboviral causes of non-specific fever and myalgia in a fever hospital patient population in Cairo, Egypt

Abstract: Fever and myalgia are non-specific clinical manifestations of illness which commonly occur in patients with arboviral disease. In Egypt, such illness is often mis-diagnosed as “influenza”. To determine arboviral aetiology in patients admitted with fever and myalgia, acute and convalescent sera samples were obtained from 55 patients admitted with these clinical manifestations to the Imbaba Fever Hospital, Giza, Egypt, during October and November 1984. Based on viral isolation, and a comparison of acute and convalescent sera, 4 patients (7%) had acute arboviral infections. Haemagglutination inhibition and indirect immunofluorescence tests showed that one had West Nile virus (WNV) infection, 2 had sandfly fever virus-Naples (SFN), and 1 had sandfly fever virus-Sicilian (SFS) infection. SFN was isolated from the acute serum sample of 1 of the 2 patients with SFN infection.

Natural infections of Leishmania major in domestic dogs from Alexandria, Egypt.

Abstract: Two leishmanial isolates from dogs from Alexandria, Egypt, were typed serologically and biochemically as Leishmania major. This is the second time that L. major has been shown to occur in dogs. The significance of these findings as a misleading phenomenon in relation to the relatively recent outbreak of infantile kala-azar in the area of Alexandria is discussed.

Sand Flies (Diptera: Psychodidae) Associated with Visceral Leishmaniasis in El Agamy, Alexandria Governorate, Egypt

Abstract: Sand fly populations were examined in the coastal resort city of El Agamy, Alexandria Governorate, Egypt, during the first outbreak of visceral leishmaniasis in that country. Phlebotomus papatasi and P. langeroni were the only species encountered in longitudinal studies over 22 months. Adult seasonal activity for both species ranged from April to December, with highest densities between June and October. In 1,335 house inspections indoors, 5,433 sand flies were collected; female P. papatasi were 60 times more common than P. langeroni . In outdoor sites, 1,812 P. langeroni and 959 P. papatasi were captured in a wide range of habitats using 9,037 sticky traps. Phlebotomus langeroni was most abundant in rodent burrows, drainage areas, poultry sheds, and rubbish. Highest densities of P. papatasi were in poultry sheds, rubbish, and rodent burrows. Sand fly larvae were not detected in 135 soil samples; thus breeding sites were not identified. No Leishmania promastigotes were detected in dissections of 1,441 P. papatasi and 39 P. langeroni . Based on their population ecology, both species showed significant spatial and temporal associations with human leishmaniasis cases.

Sand flies (Diptera: Psychodidae) associated with visceral leishmaniasis in El Agamy, Alexandria Governorate, Egypt. II. Field behavior.

Abstract: Behavioral patterns of Phlebotomus papatasi and langeroni were studied in El Agamy, a focus of visceral leishmaniasis in Alexandria Governorate, Egypt. Both species were nocturnally active in outdoor habitats from sunset to sunrise, with highest activity levels after midnight. Phlebotomus papatasi , a highly endophilic species, began entering houses directly after sunset; ingress was estimated at 17% before 2300 h and 83% from 2300 h to sunrise. Blood-engorgement rates inside houses were 75% for P. papatasi ( n = 2,238) and 52% for P. langeroni ( n = 23). Phlebotomus papatasi was gonotrophically discordant, as 14% of 222 indoor-collected, half-gravid females contained small, fresh blood meals. Phlebotomus papatasi rested inside houses during all stages of gonotrophic development, apparently with frequent ingress and egress. A total of 514 P. papatasi and 158 P. langeroni were tested for fructose by the anthrone technique. Sugar-feeding rates for both species inside houses, in different stages of blood digestion, ranged from 25 to 62%; ca. 60% of the freshly engorged females had fed on sugar. Outdoor rates were 32% for P. papatasi females, 55% for P. papatasi males and P. langeroni females, and 57% for male P. langeroni. Phlebotomus langeroni showed a greater attraction than P. papatasi to light traps and dog-baited traps. Behavioral differences between the 2 species are discussed in relation to potential for Leishmania transmission.

Phlebotomine vectors of the leishmaniases: a review.

Abstract: An account is given of work published during the past 10 years incriminating species of phlebotomine sandflies as vectors of Leishmania species which infect man. An assessment is made of the degrees of certainty of the vectorial roles of eighty-one species and subspecies of sandflies (thirty-seven Old World and forty-four New World) in the transmission of twenty-nine leishmanial parasites of mammals. At least one species of sandfly is considered to be a proven vector of each of ten parasites. Of the eighty-one sandfly taxa, evidence is judged to be sufficient to incriminate nineteen as proven vectors (eleven Phlebotomus species and eight Lutzomyia species or subspecies) and evidence for a further fourteen (nine Phlebotomus species and five Lutzomyia species or subspecies) is considered to be strong. The suggested criteria for incrimination of a vector are anthropophily and common infection with the same leishmanial parasite as that found in man in the same place. More weight should be given to natural infections persisting after the digestion of a bloodmeal than those in the presence of blood. Supporting evidence is a concordance in the distribution of the fly and the disease in man, proof that the fly feeds regularly on the reservoir host, a flourishing development of the parasite in infected flies and the experimental transmission of the parasite by the bite of the fly.

A global index representing the stability of malaria transmission

Abstract: To relate stability of malaria transmission to biologic characteristics of vector mosquitoes throughout the world, we derived an index representing the contribution of regionally dominant vector mosquitoes to the force of transmission. This construct incorporated published estimates describing the proportion of blood meals taken from human hosts, daily survival of the vector, and duration of the transmission season and of extrinsic incubation. The result of the calculation was displayed globally on a 0.5° grid. We found that these biologic characteristics of diverse vector mosquitoes interact with climate to explain much of the regional variation in the intensity of transmission. Due to the superior capacity of many tropical mosquitoes as vectors of malaria, particularly those in sub-Saharan Africa, antimalaria interventions conducted in the tropics face greater challenges than were faced by formerly endemic nations in more temperate climes.

The dominant Anopheles vectors of human malaria in Africa, Europe and the Middle East: occurrence data, distribution maps and bionomic précis

Abstract: This is the second in a series of three articles documenting the geographical distribution of 41 dominant vector species (DVS) of human malaria. The first paper addressed the DVS of the Americas and the third will consider those of the Asian Pacific Region. Here, the DVS of Africa, Europe and the Middle East are discussed. The continent of Africa experiences the bulk of the global malaria burden due in part to the presence of the An. gambiae complex. Anopheles gambiae is one of four DVS within the An. gambiae complex, the others being An. arabiensis and the coastal An. merus and An. melas. There are a further three, highly anthropophilic DVS in Africa, An. funestus, An. moucheti and An. nili. Conversely, across Europe and the Middle East, malaria transmission is low and frequently absent, despite the presence of six DVS. To help control malaria in Africa and the Middle East, or to identify the risk of its re-emergence in Europe, the contemporary distribution and bionomics of the relevant DVS are needed. A contemporary database of occurrence data, compiled from the formal literature and other relevant resources, resulted in the collation of information for seven DVS from 44 countries in Africa containing 4234 geo-referenced, independent sites. In Europe and the Middle East, six DVS were identified from 2784 geo-referenced sites across 49 countries. These occurrence data were combined with expert opinion ranges and a suite of environmental and climatic variables of relevance to anopheline ecology to produce predictive distribution maps using the Boosted Regression Tree (BRT) method. The predicted geographic extent for the following DVS (or species/suspected species complex*) is provided for Africa: Anopheles (Cellia) arabiensis, An. (Cel.) funestus*, An. (Cel.) gambiae, An. (Cel.) melas, An. (Cel.) merus, An. (Cel.) moucheti and An. (Cel.) nili*, and in the European and Middle Eastern Region: An. (Anopheles) atroparvus, An. (Ano.) labranchiae, An. (Ano.) messeae, An. (Ano.) sacharovi, An. (Cel.) sergentii and An. (Cel.) superpictus*. These maps are presented alongside a bionomics summary for each species relevant to its control.

Rift Valley fever virus (Bunyaviridae: Phlebovirus): an update on pathogenesis, molecular epidemiology, vectors, diagnostics and prevention

Abstract: Rift Valley fever (RVF) virus is an arbovirus in the Bunyaviridae family that, from phylogenetic analysis, appears to have first emerged in the mid-19th century and was only identified at the begininning of the 1930s in the Rift Valley region of Kenya. Despite being an arbovirus with a relatively simple but temporally and geographically stable genome, this zoonotic virus has already demonstrated a real capacity for emerging in new territories, as exemplified by the outbreaks in Egypt (1977), Western Africa (1988) and the Arabian Peninsula (2000), or for re-emerging after long periods of silence as observed very recently in Kenya and South Africa. The presence of competent vectors in countries previously free of RVF, the high viral titres in viraemic animals and the global changes in climate, travel and trade all contribute to make this virus a threat that must not be neglected as the consequences of RVF are dramatic, both for human and animal health. In this review, we present the latest advances in RVF virus research. In spite of this renewed interest, aspects of the epidemiology of RVF virus are still not fully understood and safe, effective vaccines are still not freely available for protecting humans and livestock against the dramatic consequences of this virus. Rift Valley fever / molecular epidemiology / vector / pathogenesis / diagnostic