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P D Ready

Publications and source records attributed to P D Ready.

At least 19 recordsLinked to original sources
PubMed2005

First detection of Leishmania major in peridomestic Phlebotomus papatasi from Isfahan province, Iran: comparison of nested PCR of nuclear ITS ribosomal DNA and semi-nested PCR of minicircle kinetoplast DNA.

Two PCR methods were compared for their sensitivity in detecting cultured Leishmania major, before being used to estimate infection rates in female sandflies (Phlebotomus papatasi) collected from peridomestic animal shelters and the nearby burrows of the gerbil reservoir hosts, Rhombomys opimus, in Isfahan province, central Iran. A semi-nested PCR was used to amplify a fragment of minicircle kinetoplast (k) DNA with a length and sequence diagnostic for L. major, and a nested PCR was developed to amplify a fragment containing the internal transcribed spacers of the ribosomal RNA genes (ITS-rDNA) with a sequence diagnostic for L. major. The semi-nested PCR was less sensitive than the nested PCR when using DNA extracted from cultured promastigotes of L. major, but it was more sensitive for detecting L. major in wild-caught sandflies. At the edges of two Isfahan villages, infection rates were significantly higher in P.papatasi collected outside gerbil burrows (14/28) compared with those from peridomestic animal shelters (2/21). This is the first record of L. major detected in P.papatasi from peridomestic sites in Isfahan province.

Animals↗
PubMed2005

Postglacial dispersal of Phlebotomus perniciosus into France.

Phlebotomus perniciosus was identified morphologically in samples from France and northeast Spain, and individuals were then characterized at three polymorphic isoenzyme loci (by isoelectrofocusing) and at the mitochondrial DNA locus (by comparative DNA sequence analysis of a fragment of the Cytochrome b gene). The four polymorphic loci gave conflicting patterns of population relationships, which can be explained by hypothesizing different amounts of gene introgression at each locus when two distinctive lineages met in southern France or northeast Spain after isolation in southern Italy and Spain during the Pleistocene Ice Ages. P. perniciosus is an important vector of leishmania infantum and so these population differentiation studies are relevant for predicting the emergence and spread of leishmaniasis in relation to environmental changes, including climate.

Animals↗
PubMed2004

Regional genetic differentiation of Phlebotomus sergenti in three Moroccan foci of cutaneous leishmaniasis caused by Leishmania tropica.

Phlebotomus sergenti was identified morphologically in samples from three Moroccan foci of leishmaniasis caused by Leishmania tropica in the provinces of Azilal, Essaouira and Taza. Three primary mitochondrial DNA lineages were identified, and they could be markers for regionally distributed cryptic species. Greater mitochondrial diversity in Azilal indicated that this central province could have been the origin of dispersal of P. sergenti or the zone of secondary contact. All except one of the 21 mitochondrial haplotypes showed a marked regional distribution, and this indicates that vector control would not always be followed by rapid, long-distance reinvasion. Only mitochondrial haplotype SER18 was a putative marker for long-distance dispersal, for which there is no evidence of human assistance.

Animals↗
PubMed2004

Sandflies of the Phlebotomus perniciosus complex: mitochondrial introgression and a new sibling species of P. longicuspis in the Moroccan Rif.

The bloodsucking adult females of Phlebotomus perniciosus Newstead and P. longicuspis Nitzulescu (Diptera: Psychodidae) are important vectors of the protozoan Leishmania infantum Nicolle (Kinetoplastida: Trypanosomatidae) in western Mediterranean countries. The species status of the two phlebotomine sandflies was assessed, along with the epidemiological implications. Individual sandflies from three Moroccan Rif populations were characterized morphologically, isoenzymatically (by the isoelectrofocusing of alleles at the polymorphic enzyme loci of HK, GPI and PGM), and by comparative DNA sequence analysis of a fragment of mitochondrial Cytochrome b (mtDNA). By reference to the character profiles of specimens from other locations, including southern Spain and the type-locality countries, the Moroccan flies were placed in three lineages: first, the lineage of P. perniciosus, which contained two mtDNA sublineages, one (pnt) widely distributed and associated with the morphology of the male types from Malta, and the other (pna) associated with a P. longicuspis-like male morphology; second, the lineage of P. longicuspis sensu stricto, including typical forms from Tunisia; and third, a new sibling species of P. longicuspis. The mtDNA sublineage (pnt) of typical P. perniciosus was also found in some P. longicuspis from Morocco, indicating interspecific hybridization. The typical race of P. perniciosus occurs in Italy as well as in Malta, Tunisia and Morocco. It is replaced in southern Spain by the Iberian race (with the pni mtDNA sublineage). The discovery of interspecific gene introgression and a new sibling species mean that previous records of the two morphospecies do not necessarily reflect their true vectorial roles or geographical and ecological distributions.

Alleles↗
PubMed2003

Comparative vectorial efficiency of Lutzomyia evansi and Lu. longipalpis for transmitting Leishmania chagasi.

The infection rates and development of Leishmania chagasi in two sandfly species, Lutzomyia evansi and Lutzomyia longipalpis, were evaluated under natural and experimental conditions. Natural infection rates of Lu. evansi in San Andrés de Sotavento (Colombia) and Montañas de Peraza (Venezuela) (0.05 and 0.2%, respectively) were similar to those previously recorded for this species in Colombia and Venezuela and for Lu. longipalpis in many foci of American Visceral Leishmaniasis (AVL). Both sand fly species were able to support the development of two Colombian strains of L. chagasi experimentally acquired from dogs, hamsters or membrane feeders. However, the experimental infection rates and the sequence of parasite development in the guts of these sand flies revealed that parasite colonisation, differentiation, migration and attachment were more frequent and uniform in Lu. longipalpis than in Lu. evansi. This is consistent with a more recent association between L. chagasi and Lu. evansi, and these results might help to explain the irregularity of AVL outbreaks in foci where Lu. evansi has been reported as the sole vector.

Animals↗
PubMed2003

Population differentiation of Phlebotomus perniciosus in Spain following postglacial dispersal.

Comparative sequencing of mitochondrial cytochrome b (Cyt b) and isoenzyme analyses have not resolved the population structure of the Iberian lineage of the sandfly Phlebotomus perniciosus, the most widespread vector of Leishmania infantum (Protozoa, Trypanosomatidae) to humans and dogs in the western Mediterranean subregion. Allelic variation at trinucleotide microsatellite loci was investigated in 13 Spanish populations of P. perniciosus. Four out of five loci showed significant differentiation between (pairwise F(ST)>0.23), but not within (pairwise F(ST)&<0.05), two regional groups of populations (southern and northeastern). All Cyt b sequences belonged to the Iberian lineage, which differs by six fixed nucleotide differences from the typical lineage found in northwest Africa, Malta and Italy. The northeastern group of Spanish populations had a reduced number of microsatellite alleles (16 out of the 29 present in the southern populations), indicating its derivation as a peripheral isolate following the species' dispersal from a southern Ice Age refuge 8000-12 000 years ago. Pairwise F(ST) values did not increase with geographical distance between populations, over distances of 246-850 km (between regions) and 16-491 km (within regions). This suggests that the two regional groups of populations remain isolated, but that within each region there are no significant permanent barriers to gene flow between contiguous populations. These findings will help to predict the capacity of this sandfly to disperse, and originate new foci of leishmaniasis, in response to climate warming.

Animals↗
PubMed2003

Host-specific Wolbachia strains in widespread populations of Phlebotomus perniciosus and P. papatasi (Diptera: Psychodidae), and prospects for driving genes into these vectors of Leishmania.

A single strain of Wolbachia (alpha-proteobacteria, Rickettsiales) was found in widespread geographical populations of each of two Phlebotomus species, within which there was no indication of 'infectious speciation'. The two strains were identified by sequencing a fragment of wsp (a major surface protein gene), amplified by polymerase chain reaction from DNA extracted from the body parts of individual sandflies. Infection rates were high in the males and females of both sandflies, but they were lower for the B-group wPrn strain of Wolbachia in Phlebotomus perniciosus Newstead (60.3% overall) than for the A-group wPap strain in P. papatasi (Scopoli) (81.7%). Infections were frequent in the thorax, where Leishmania develops infective forms, as well as in the abdomen, where Wolbachia must infect the reproductive tissues to ensure its vertical transmission. These findings were related to knowledge of the population biology of Wolbachia in other insects, leading to the conclusion that this endosymbiont could be useful for driving transgenes through wild populations of both sandflies. This will require characterizing the cytoplasmic incompatibility phenotypes of Wolbachia-sandfly combinations, as well as estimating for them the incidence of paternal transmission and the fidelity of maternal transmission. Paternal transmission is one explanation for finding a single Wolbachia strain associated with all mitochondrial haplotypes and lineages of each sandfly species. However, this distribution pattern could also result from multiple horizontal transmissions or the failure of wsp to provide strain markers.

Animals↗
PubMed2003

Mitochondrial and Wolbachia markers for the sandfly Phlebotomus papatasi: little population differentiation between peridomestic sites and gerbil burrows in Isfahan province, Iran.

In Iran, Phlebotomus papatasi (Scopoli) (Diptera: Psychodidae) is the main vector of Leishmania major Yakimoff & Schokhor (Kinetoplastida: Trypanosomatidae), the causative agent of rural zoonotic cutaneous leishmaniasis. This sandfly is abundant both in villages and in the burrows of the main reservoir host, the gerbil Rhombomys opimus (Licht.) (Rodentia: Gerbillidae). Populations of P. papatasi were sampled from the edges of villages in Isfahan province, using CDC miniature light traps in peridomestic sites and sticky papers placed at the entrances to gerbil burrows. Single peridomestic sites in two northern provinces were also sampled. Individual sandflies were characterized by PCR amplification and sequencing of fragments of their mitochondrial cytochrome b gene and of the wsp gene of endosymbiotic Wolbachia pipientis Hertig (alpha-Proteobacteria: Rickettsiaceae). The distributions of the haplotypes of these two maternally inherited genes were analysed to assess the population differentiation of P. papatasi, knowledge of which will be needed for planning control measures. For the first time these markers were used to characterize P. papatasi from gerbil burrows, and they indicated the absence not only of sympatric cryptic species but also of any long-term differentiation of lineages in different habitats. A single lineage of cytochrome b haplotypes was found, and both sexes in all populations had a high infection rate of the same A-group strain of Wolbachia (wPap). The distributions of cytochrome b haplotypes were consistent with females dispersing more than males, which has been reported for P. papatasi in other countries. The widespread distribution of wPap suggests that Wolbachia could be used to spread transgenes between populations of P. papatasi in different habitats.

Animals↗
PubMed2002

Molecular identification of vectors of Leishmania in Colombia: mitochondrial introgression in the Lutzomyia townsendi series.

The identity of the sandfly vectors of Leishmania braziliensis in Valle del Cauca Department, Colombia, was originally given as Lutzomyia townsendi, but then changed to L. youngi, another member of the L. townsendi series (Verrucarum group) with isomorphic females. To identify members of this series in Valle del Cauca, we analyzed the nuclear gene elongation factor-alpha (EF-alpha) and the mitochondrial gene cytochrome b (Cyt b). DNA sequences from the L. verrucarum series (L. columbiana, L. evansi and L. ovallesi) were used as outgroups. Flies from two locations on the western cordillera of the Andes were identified as L. townsendi s.s., according to male morphology and distinctive gene lineages. In the third location, on the central cordillera of the Andes, most specimens were identified as belonging to a geographical population of L. youngi, according to male morphology, an EF-alpha lineage shared with L. youngi from the Venezuelan-type locality, and a distinctive Cyt b sub-lineage. All other specimens were identified as L. youngi with the introgressed Cyt b sequences of L. townsendi. Such interspecific introgression implies that vectorial traits and ecological associations may no longer be viewed as fixed properties of different morphospecies.

ATP-Binding Cassette Transporters↗
PubMed2001

Old World screwworm fly, Chrysomya bezziana, occurs as two geographical races.

A morphological and molecular analysis was undertaken with the objective of identifying markers for geographical populations of Old World screwworm flies, Chrysomya bezziana Villeneuve (Diptera: Calliphoridae). The morphological analysis involved 192 adult flies from 14 countries, and the molecular analysis involved 45 larvae or adults from 14 populations in 11 countries. Principal components and cluster analysis of 10 morphological characters indicated that flies from Papua New Guinea (PNG) were a distinct group and most similar to flies from nearby Asian islands (Java, Sabah). There was poor resolution of other geographical regions, but some support for clustering of flies from Africa or India. Cladistic analysis of mitochondrial DNA sequences gave strong support for recognizing two races of Old World screwworm, one from sub-Saharan Africa and the other from the Gulf region and Asia. This latter race could be further divided into two lineages, i.e. one from mainland Asia (from Iraq to the Malay Peninsula) and the other from two islands of PNG.

Africa↗
PubMed2000

Phylogenetic relationships of phlebotomine sandflies inferred from small subunit nuclear ribosomal DNA.

Relationships among seventy specimens, fifteen species and three genera of phlebotomines were inferred from the phylogenetic analysis of small subunit nuclear rDNA, obtained by the PCR amplification and cloning of almost full-length genes. Outgroups included fifteen dipterans, and single representatives of four other insect orders. The more distant the taxa compared, the larger were the regions of ambiguous sequence alignment that needed to be deleted in order to avoid circularity in performing parsimony analyses. Phlebotomine sequences formed a monophyletic clade within the suborder Nematocera, with the progressively more basal sister groups of Diptera being Culicomorpha, Tipulomorpha and the suborder Brachycera. Within Phlebotominae, subgeneric relationships were resolved and the genus Phlebotomus was shown to be monophyletic, but markers for intraspecific geographical populations were not found and intergeneric relationships were not resolved.

Animals↗
PubMed2000

Domesticity of Lutzomyia whitmani (Diptera: psychodidae) populations: field experiments indicate behavioural differences.

The sandfly Lutzomyia whitmani (Antunes & Coutinho) is an important vector for cutaneous leishmaniasis throughout much of Brazil, and has recently been shown to consist of more than one mitochondrial lineage. It has frequently been asserted that the degree of adaptation of L. whitmani to human environments varies across its range. As a standardized test of indoor feeding for three geographically distant populations of L. whitmani, catches inside experimental chicken sheds of varying degrees of wall closure (0%, 33%, 67% and 98%) were compared. Each increment in shed closure reduced catches of females (relative to the most open shed) by a similar degree for each population: geometric mean catches dropped by 11-40% with 33% closure, by 41-62% with 67% closure, and by 69-100% with 98% closure. Geometric mean catches of males from the two more northerly populations also decreased with increasing shed closure, by 18% and 22% for 33% closure, 58% and 69% for 67% closure, 91% and 93% for 98% closure. Males from the most southerly population showed significantly different behaviour, with 33% closure causing a 54% increase in geometric mean catch, 67% closure causing a 6% increase, and 98% closure causing a 32% reduction. For this southerly population, sex ratios became more male biased with increasing density in more closed sheds, suggesting aggregation driven by intra-specific communication. Lutzomyia intermedia (Lutz & Neiva) was relatively more likely than L. whitmani to approach baits in the three more closed sheds, rather than the most open shed, offering a behavioural explanation for observed differences in indoor biting rates between the species.

Animals↗
PubMed1999

Relative abundance, isolation and structure of phlebotomine microsatellites.

Popular classes of microsatellites are not always abundant in insects or easily isolated from them. Dotblot hybridizations demonstrated much variation in the relative abundance of four repeat classes in four phlebotomine sandfly species. Only AAT-class repeats were specifically isolated from a phagemid library of Lutzomyia whitmani, even though other microsatellites had similar abundances. An enrichment step would have targeted classes but was omitted because relatively long flanking sequences were sought. All fourteen sandfly loci had a non-coding structure, and a minority of dipteran AAT-class repeats found in DNA databases and the literature were from exons. Therefore, this class should often provide neutral alleles for population studies. Perfect, not imperfect, AAT-class repeats were polymorphic in wild L. whitmani.

Animals↗
PubMed1999

Experimental comparison of anthropophily between geographically dispersed populations of Lutzomyia whitmani (Diptera: Psychodidae).

Lutzomyia whitmani, a major vector of cutaneous leishmaniasis in Brazil, occupies diverse habitats from the Amazon forest canopy to suburban animal pens. Three mitochondrial lineages of Lu. whitmani ('Amazonian', 'North-South' and 'North-east') have parapatric distributions coinciding with different ecological zones. We assessed the host preferences of populations representing the three lineages in standardized field experiments, and found that Lu. whitmani in all sites were significantly more attracted to humans than to dogs or chickens. Females from a southerly population of the North-South lineage showed the greatest degree of anthropophily. Lu. whitmani from Amazonia were also strongly attracted to human baits, contradicting previously published accounts. Intraspecific comparisons in non-Amazonian sites suggest that Lu. whitmani is less anthropophilic than Lu. intermedia but more so than Lu. longipalpis. No significant difference was detected in anthropophily between Lu. whitmani in the Amazon and either Lu. dendrophyla or Lu. gomezi. Anthropophilic behaviour was demonstrated in the same site for Lu. complexa, Lu. flaviscutellata and Lu. brachyphalla, but not for Lu. infraspinosa.

Animals↗
PubMed1998

A 169-base pair tandem repeat DNA marker for subtelomeric heterochromatin and chromosomal rearrangements in aphids of the Myzus persicae group.

Numerous copies of a 169-base pair DNA sequence (Myzus persicae group repeat; MpR) occur at subtelomeric locations on all chromosomes of three members of the Myzus persicae species group (Myzus persicae, M. antirrhinii, M. certus). MpR occurs in large tandem arrays at both ends of all autosomes of the standard 2n = 12 karyotype, and near one end of the X chromosome (the end opposite to the nucleolar organizer) and is estimated to make up about 5% of the genome (a total of about 200000 copies). Locations of MpR were compared in various karyotypes to determine the likely nature of the rearrangements (fusions, dissociations, translocations) that are found in this species group which, like other Hemiptera, has holocentric chromosomes that are devoid of morphological markers. Aphid clones heterozygous for autosome dissociations do not have any detectable MpR at 'new' chromosome ends, indicating that this sequence is not involved in 'capping' of chromosomes. However, a clone with a de novo autosome fusion had an interstitial block of MpR marking the point of fusion, and clones heterozygous for an autosomal 1,3 translocation had MpR from autosome 1 translocated to a new site on autosome 3. The isolation from M. antirrhinii of the telomeric repeat TTAGG, which is found in several insect groups, is also reported.

Animals↗
PubMed1997

Mitochondrial haplotypes and phylogeography of Phlebotomus vectors of Leishmania major.

Haplotypes of eight phlebotomine species were characterized by cycle sequencing a mitochondrial (mt) DNA fragment (cytochrome b to NADH1) amplified from single sandflies by PCR. Phlebotomus (Phlebotomus) papatasi displayed little variation throughout its large geographical range. We conclude that this vector of Leishmania major suffered a population bottleneck late in the Pleistocene and then radiated out from the eastern Mediterranean subregion. There was no support for a recent domestic lineage of P. papatasi. The mtDNA molecular clock in phlebotomines (subgenera Phlebotomus and Larroussius) was calibrated by reference to palaeogeographical events in Africa and the Mediterranean subregion. It fitted a pairwise nucleotide sequence divergence rate of 1.0-2.5% per million years. Co-evolution of L. major, its Phlebotomus vectors and mammalian reservoirs is discussed.

Africa↗
PubMed1996

Evolution of multiple families of non-LTR retrotransposons in phlebotomine sandflies.

In this paper we report on the diversity and distribution of a set of non-LTR retrotransposon (RTP) reverse transcriptase (RT) sequences isolated from phlebotomine sandflies, and their potential for investigating the evolutionary histories of members of this subfamily of flies (Diptera:Psychodidae, Phlebotominae). The phlebotomine RT sequence families derived from one species were as different from each other as they were from RT sequences derived from other species. When each was used to probe Southern blots of sandfly genomic DNA they hybridized only to the species of source and, usually, to others of the same subgenus, but not to DNA from other subgenera-a hybridization pattern consistent with vertical evolution. There was considerable intraspecific variation in hybridization pattern, suggesting the RTs were part of non-LTR RTPs that are (or were recently) subject to flux in genomic position and copy number. Most of the RT families detected in phlebotomines are monophyletic with respect to previously described RTs, and all are monophyletic with RTs of the F/Jockey (Drosophila melanogaster) type of RTP. Orthologous sequences were isolated from the closely related species Phlebotomus perniciosus and P. tobbi (subgenus Larroussius), and different populations of P. perniciosus. The level of sequence divergence among these orthologous RTs, the subgeneric distribution of each RT family, and the intraspecific variation in hybridization pattern of many of them, indicate this class of sequence will provide genetic markers at the sub-generic level.

Amino Acid Sequence↗