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PubMed2005

Musca domestica is not a vector of Thelazia callipaeda in experimental or natural conditions.

Thelazia callipaeda Railliet and Henry (Spirurida: Thelaziidae), commonly called oriental eyeworm for its widespread presence in the Far East, has been recently found to affect dogs, cats and foxes in northern and southern Italy. Although the biology of T. callipaeda in the definitive hosts has been recently investigated, many doubts still remain about its biology in insect vectors. It has been suggested that more than one species of Diptera, namely Musca domestica Linnaeus (Diptera: Muscidae) and Amiota okadai Maca (Diptera: Drosophilidae), may be involved in the transmission of T. callipaeda in China. The aim of the work described here was to verify the role of M. domestica as a vector of T. callipaeda both in experimental and natural conditions. A total of 310 m. domestica (Group 1) were put in a cage and allowed to feed for 14 days around the eyes of a dog naturally infected by T. callipaeda. Ten flies were collected daily for 14 days. A total of 149 houseflies (Group 2) were fed with T. callipaeda first stage larvae (L1) and dissected at 1, 2 and 7 days post-infection. From June to August 2003, flies were netted (Group 3) in two different sites every 10 days both from the environment and directly from the periocular region of dogs affected by thelaziosis. Musca flies were examined for eyeworms by dissection and visual inspection of house flies (Groups 1 and 2) and using a molecular approach (Groups 1-3) via a specific amplification of the ribosomal internal transcribed spacer 1 (ITS1) sequence of T. callipaeda. On the whole, 180 pools of M. domestica flies were processed molecularly and all the experimentally infected flies (Groups 1 and 2) were found to be negative both at the visual dissection and at the molecular assay. Similarly, the 234 M. domestica collected from Group 3 were negative for T. callipaeda. The results clearly suggest that M. domestica is unlikely to act as a vector of T. callipaeda in southern Europe, in contrast with a single previous report.

Animals↗
PubMed2002

Dressed for success: the surface coats of insect-borne protozoan parasites.

Three major human diseases, malaria, sleeping sickness and leishmaniasis, are caused by protozoan parasites that are transmitted by blood-sucking insects. These insects are not mere 'flying syringes' that mechanically transfer parasites from one mammal to the next. Instead, they provide a specific environment--albeit not a particularly hospitable one--in which the parasites differentiate, proliferate and migrate to the correct tissues to ensure transmission to the next mammalian host. Recent studies on the role of parasite surface molecules in insect vectors have delivered some surprises and could provide insights on ways to interrupt transmission.

Animals↗
PubMed1991

A comparison of non-radioactive labeling and detection systems with synthetic oligonucleotide probes for the species identification of mosquitoes in the Anopheles gambiae complex.

Different non-radioactive probe labeling and detection systems were used with pAnaI, a species-specific oligonucleotide probe that distinguishes male Anopheles gambiae and An. arabiensis mosquitoes. Comparisons have been made between the performance of each technique with respect to sensitivity and specificity against DNA dot-blots and mosquito squashes. Their relative costs, economy, and ease of use were analyzed in an attempt to develop an appropriate non-radioactive system for use in the field. Enzyme-labeled probes that were detected directly by label activity proved more suitable than probes requiring reporter molecules for detection. Binding of reporter molecules to mosquito squashes caused the appearance of false positives and, in addition, their binding to nylon filters caused high background coloration. Chemiluminescent detection provided an attractive alternative to colorimetric detection. Both systems analyzed were rapid, simple, and economic. However, less severe treatment of filters was required for reprobing with chemiluminescence. The greatest sensitivity achieved was with chemiluminescent detection in which the limit of detection was 0.15 ng of target DNA. This study suggests that a synthetic DNA probe coupled to a chemiluminescent detection system should provide a sufficiently simple, sensitive, and reliable technique for insect vector identification in the field.

Animals↗
PubMed1968

Number of virus particles in insects and plants infected with wound tumor virus.

A new procedure for counting virus particles was employed to measure the concentration of wound tumor virus in purified virus preparations, in plant tumors, and in the insect vector. Partially purified wound tumor virus was used to establish the quantitative features of the method. A 1-g amount of plant tumor tissue contained an average of 5 x 10(10) virus particles and 1 g of insect tissue contained 2 x 10(10) particles.

Centrifugation, Density Gradient↗
PubMed2002

Germ line transformation of the yellow fever mosquito, Aedes aegypti, mediated by transpositional insertion of a piggyBac vector.

Mosquito-vectored diseases such as yellow fever and dengue fever continue to have a substantial impact on human populations world-wide. Novel strategies for control of these mosquito vectored diseases can arise through the development of reliable systems for genetic manipulation of the insect vector. A piggyBac vector marked with the Drosophila melanogaster cinnabar (cn) gene was used to transform the white-eyed khw strain of Aedes aegypti. Microinjection of preblastoderm embryos resulted in four families of cinnabar transformed insects. An overall transformation frequency of 4%, with a range of 0% to as high as 13% for individual experiments, was achieved when using a heat-shock induced transposase providing helper plasmid. Southern hybridizations indicated multiple insertion events in three of four transgenic lines, while the presence of duplicated target TTAA sites at either ends of individual insertions confirmed characteristic piggyBac transposition events in these three transgenic lines. The transgenic phenotype has remained stable for more than twenty generations. The transformations effected using the piggyBac element establish the potential of this element as a germ-line transformation vector for Aedine mosquitoes.

Aedes↗
PubMed1963

Some principles of the epidemiology of human trypanosomiasis in Africa.

Human trypanosomiasis in Africa is treated as a disease complex in which three main elements are involved, the vertebrate host, the parasite and the insect vector, and the epidemiology is discussed in terms of the three pairs of relationships between these elements.Under host-vector relationships the significance of the type of man-fly contact is pointed out and an outline given of how it may be determined, and transmission of the disease influenced, by human activities, climatic factors and other conditions, in both Trypanosoma gambiense and T. rhodesiense sleeping-sickness.Under host-parasite relations consideration is given to the question of reservoir hosts, variations between human-infective strains in virulence, infectivity to animals and response to chemotherapy, and the relationships of these factors to one another and to the epidemiology of the disease.The complexity of factors involved in vector-parasite relations is discussed and the need for fuller information on the relative importance of these factors is stressed.

Africa↗
PubMed1997

Human and canine dirofilariasis in Greece.

Human dirofilariasis is a disease which is considered to be rare in Greece, less than 20 cases having been reported prior to 1990. The clinical manifestations were usually subcutaneous nodules, and in only two cases there was ocular dirofilariasis. Eight new cases were recognized in humans during the last six years in Athens, two of which with ophthalmic involvement. Twelve additional cases have been detected but not published in Thessaloniki. In all human cases, the worms were identified as being Dirofilaria repens (D. conjunctivae). The identification was based on the morphological observations of the whole nematodes and on the histological sections of the subcutaneous nodules in the samples. Four different filarial nematodes (D. immitis, D. repens, Dipetalonema reconditum and D. grassii) were recovered from dogs. Infection of dogs with all types of filariae ranges from 12% to 37%. The high incidence of dirofilariasis in dogs is of great interest compared to the low incidence in humans. The occurrence of common host animals and insect vectors makes dirofilariasis a potential danger for public health.

Animals↗
PubMed2003

The mosquito genome: perspectives and possibilities.

Anopheles gambiae is the mosquito vector responsible for transmitting Plasmodium falciparum, a malaria parasite of humans. With the emergence of genome projects for a variety of prokaryotic and eukaryotic microorganisms, there has been a long-standing interest in sequencing the genomes of the malaria parasite and its insect vector. This tour de force effort has now been completed and reported. The alignment of putative orthologs in An. gambiae with those of Drosophila melanogaster highlights several similarities and differences. These findings could have implications in: (1) identifying new targets for insecticide development; (2) strengthening our understanding of the developmental biology of mosquitoes; and (3) possibly controlling pathogen transmission. A brief overview of these interesting findings and the implications for further studies will be discussed here.

Animals↗
PubMed2005

Dipterous flies species and their densities in fourteen Egyptian Governorates.

The present study focused on dipterous flies, distribution and densities in 14 Egyptian Governorates. The abundance and distribution of flies was carried out in three phases. The first was in 1999 in 5 governorates, Qalyobia, Menoufia, Fayium, Behiera & Assuit included species of the families: Calliphoridae, Chloropidae, Drosophilidae, Milichiidae, Muscidae, Otitidae, Piophilidae, Sarcophagidae, Sepsidae, Sphaeroceridae and Syrphidae. The second was in 2000 in another five Governorates, Kafr-ElSheikh, Giza, Menia, Aswan and Sharkia included sp. of the families: Calliphoridae, Chloropidae, Drosophilidae, Milichiidae, Muscidae, Otitidae, Piophilidae, Sarcophagidae, Sepsidae, Sphaeroceridae and Syrphidae. The third phase was in 2001 in 4 Governorates: Kena, El-Wady El-Gedied, Da-kahlia and South Sinai included species of the families: Calliphoridae, Chloropidae, Drosophilidae, Milichiidae, Muscidae, Otitidae, Phoridae, Piophilidae, Sarcophagidae, Sepsidae, Sphaeroceridae and Syrphidae. Musca domestica was the most abundant sp. found throughout the work. The results are a step in drawing an update map for insect-vectors to help in the national control programs.

Animals↗
PubMed1990

The replication of bluetongue virus in Culicoides vectors.

BTV is maintained in nature by an endless series of alternating cycles of replication in Culicoides midges and various mammalian ruminant species. Experimentation has shown that the ability of the virus to infect Culicoides persistently and be transmitted by them is restricted to a relatively small number of species. In essence, therefore, the world distribution map of BTV is little more than a distribution map of competent insect vectors. Once ingested by a competent vector, BTV attaches to the luminal surface of the mid-gut cells, infects these cells and replicates in them. Progeny virus is then released through the basement lamina into the haemocoel from where the secondary target organs including the salivary glands are infected. Subsequent to virus replication in the salivary glands transmission can taken place. The whole cycle from infection to transmission takes between 10-15 days at 25 degrees C and individual vectors once infected usually remain so for life. Not all female midges within a vector species are susceptible to infection with BTV, or if infected, are competent to transmit the virus. A series of barriers or constraints exists within certain individuals of a vector species which either prevents virus infection or else restricts it in such a way as to stop transmission. Each population of a vector species of Culicoides has a variable proportion of these so-called refractory midges. The refractory and susceptible traits for BTV within a vector species are under genetic control, and by selective breeding, highly susceptible or completely insusceptible populations can be obtained. However, the mechanisms by which these traits are expressed are poorly understood. Further studies are therefore urgently required to determine the precise biochemical nature of these mechanisms and their mode of operation.

Animals↗
PubMed2005

Vertical and venereal transmission of Chandipura virus (Rhabdoviridae) by Aedes aegypti (Diptera: Culicidae).

Experiments in the laboratory documented vertical and venereal transmission of Chandipura virus (CHPV) in Aedes aegypti (L.). The minimum filial infection rate among the progeny of infected females was 1.2%; the rate among male and female progeny was 0.9 and 1.4%, respectively. The venereal infection rate of CHPV among inseminated females was 32.7%. Our study indicates the possible occurrence of vertical and venereal transmission of CHPV in insect vectors.

Aedes↗
PubMed1993

Gene deletion suggests a role for Trypanosoma cruzi surface glycoprotein GP72 in the insect and mammalian stages of the life cycle.

We have explored the biological function of a surface glycoprotein (GP72) of Trypanosoma cruzi by studying a null mutant parasite, generated by targeted gene deletion. GP72 deletion affected parasite morphology in several stages of the life cycle. Insect midgut (epimastigote) forms had a detached flagellum (apomastigote) in the null mutant. The abnormal flagellar phenotype persisted during development of the infective (metacyclic) forms but there was no impairment in the acquisition of complement resistance, sialidase expression or cell infectivity. The GP72 null mutant could efficiently infect and proliferate in mouse macrophages and non-phagocytic L6E9 cells. The mammalian stages of the life cycle also showed major morphological abnormalities. During early subcultures in L6E9 cells, few extracellular fully flagellated forms, expressing markers characteristic of trypomastigotes, were seen. The extracellular population consisted almost exclusively of rounded forms with short flagella (micromastigote), which expressed an amastigote-specific surface marker and no sialidase. The propagation of the parasite was not affected, despite the apparent lack of the trypomastigote forms, which are thought to be primarily responsible for cell invasion. After some subcultures, the extracellular population changed to about equal numbers of micromastigotes and a range of flagellated forms that still did not include true trypomastigotes. Instead, the kinetoplast remained close to the nucleus and the flagellum emerged from the middle of the cell (mesomastigote). Half of the flagellum adhered to the cell body and the remainder was free at the anterior end. In Triatoma infestans, the survival of the mutant was dramatically reduced, suggesting that either GP72 itself, or the altered properties of the flagellum, were critical for establishment in the insect vector.

Animals↗
PubMed1998

Control and surveillance of African trypanosomiasis. Report of a WHO Expert Committee.

Current estimates indicate that 60 million people are at risk of infection with human African trypanosomiasis or sleeping sickness, with about 300,000 new cases each year. However, less than 4 million people are under surveillance and only 10% of new cases are diagnosed and treated. This report of a WHO Expert Committee reviews current epidemiological information on African trypanosomiasis and its vectors, and evaluates recent advances in drug treatment and the development of tools for the control and surveillance of the disease. The report provides examples of treatment schedules, vector control operations, indicators for monitoring control and surveillance activities and sample calculations for analysing the cost-effectiveness of different strategies, as well as details of methods for cryopreservation of trypanosome-infected blood samples and a description of traps and screens for the control of the insect vector, Glossina. Although primarily addressed to health policy-makers in countries endemic for sleeping sickness, this report will also be a useful reference source for health care staff at all levels, including physicians, nurses, auxiliary staff and students, as well as those engaged in research on the disease.

Africa South of the Sahara↗
PubMed2002

Duration of viraemia infectious to Culicoides sonorensis in bluetongue virus-infected cattle and sheep.

The duration of viraemia infectious to Culicoides sonorensis (C. sonorensis) was evaluated in bluetongue virus (BTV)-infected sheep and cattle by feeding laboratory-reared C. sonorensis directly on the skin of ruminants that previously were infected with BTV by insect inoculation. The intervals after infection when infectious BTV and BTV nucleic acids were present in the blood of infected cattle and sheep, respectively, were determined by virus isolation and reverse transcriptase (RT)-nested polymerase chain reaction (PCR) assays. The presence of BTV in vector insects that fed on the BTV-infected cattle and sheep at 7, 21, and 49 days post-infection (p.i.) was also determined by virus isolation and RT-PCR assays. BTV was isolated from the blood of infected cattle for up to 49 days p.i., whereas it was not isolated from the BTV-infected sheep after 11 days p.i. In contrast, BTV nucleic acids were detected in the blood of infected ruminants for 111-222 days p.i. The maximal duration of viraemia that was infectious to C. sonorensis was 21 days p.i. of both cattle and sheep and, with the notable exception of one sheep at 21 days p.i., only ruminants whose blood contained BTV as determined by virus isolation were able to infect C. sonorensis after oral feeding. Data from this and previous studies indicates that viraemia is transient in BTV-infected ruminants, and that the RT-nested PCR assay provides a very sensitive and conservative test for the screening of cattle and sheep for the presence of BTV.

Animals↗
PubMed1995

Morphological studies on Phlebotomus papatasi (Scopoli) in Riyadh City, Saudi Arabia.

In general, leishmaniasis is more or less a problem not only in Saudi Arabia but also in all countries of the Eastern Mediterranean Region. In Saudi Arabia, the most important form is zoonotic cutaneous leishmaniasis (ZCI.). It's main vector, Phlebotomus papatasi has been reported and incriminated by many authors. In this paper, the diagnostic morphology of P. papatasi as compared to other species found in Riyadh as well as the immature stages was given. This is considered as a base line data for studying the ecology and biology of P. papatasi. No doubt the best control strategy is based on complete understanding of the insect vector of ZCL.

Animals↗
PubMed2001

Exchange of three amino acids in the coat protein results in efficient whitefly transmission of a nontransmissible Abutilon mosaic virus isolate.

Geminiviruses are transmitted in a circulative manner by whiteflies, leafhoppers, or treehoppers. The whitefly species Bemisia tabaci (Genn.) is the vector for members of the genus Begomovirus. The closely related bipartite Central American begomoviruses Abutilon mosaic virus (AbMV), Sida golden mosaic virus originating from Costa Rica (SiGMV-CR), and Sida golden mosaic virus originating from Honduras (SiGMV-Hoyv) were used to study transmission by their insect vector. The AbMV isolate is defective in transmission, whereas the two Sida-infecting viruses are readily transmitted by B. tabaci. These three viruses are able to form pseudorecombinant viruses by exchange of genomic components. The pseudorecombinant virus SiGMV-Hoyv A/AbMV B was transmissible, whereas the reciprocal pseudorecombinant virus AbMV A/SiGMV-Hoyv B was not transmitted, indicating that DNA B is not involved in the transmission defect. However, the uptake of the pseudorecombinant virus AbMV A/SiGMV-Hoyv B was much better than AbMV itself, indicating that DNA B or DNA B gene products enhance uptake of viral DNA. Exchange of AbMV coat protein with that of SiGMV-CR resulted in a transmissible chimeric AbMV. Mutagenesis of the AbMV coat protein showed that the exchange of two amino acids, at positions 124 and 149, was sufficient to obtain a whitefly-transmissible AbMV mutant. However, when amino acid 174 was altered in addition to amino acids 124 and 149 AbMV was readily transmitted by B. tabaci. From this we conclude that it is not a concise motif, such as the amino acid triplet, aspartate-alanine-glycine (DAG), involved in aphid transmission of potyviruses, that determines transmissibility of begomoviruses by B. tabaci. Instead it is the composition of the coat protein domain from amino acid 123 to 149, as a minimal transmission domain, with the contribution of amino acids 149 to 174 for efficient transmission.

Amino Acid Sequence↗
PubMed1957

The distribution of Bancroftian filariasis in Africa.

Bancroftian filariasis is widespread in Africa in the region between the Sahara Desert to the north and the Zambesi river to the south, and is also found in Egypt. It occurs in hot damp areas near the coasts, along the great rivers, and around the great lakes.The chief insect vectors seem to be Anopheles gambiae and A. funestus. Culex fatigans has been found to be a poor vector in most parts of Africa.An annex gives certain additional information not available at the time of preparation of the main review.

Africa↗