Insecticide-impregnated dog collars reduce infantile clinical visceral leishmaniasis under operational conditions in NW Iran: A community-wide cluster randomised trial

OBJECTIVE

To assess the effectiveness of community-wide deployment of insecticide-impregnated collars for dogs- the reservoir of Leishmania infantum-to reduce infantile clinical visceral leishmaniasis (VL).

METHODS

A pair matched-cluster randomised controlled trial involving 40 collared and 40 uncollared control villages (161 [95% C.L.s: 136, 187] children per cluster), was designed to detect a 55% reduction in 48 month confirmed VL case incidence. The intervention study was designed by the authors, but implemented by the Leishmaniasis Control Program in NW Iran, from 2002 to 2006.

RESULTS

The collars provided 50% (95% C.I. 17·8%-70·0%) protection against infantile VL incidence (0·95/1000/yr compared to 1·75/1000/yr). Reductions in incidence were observed across 76% (22/29) of collared villages compared to pair-matched control villages, with 31 fewer cases by the end of the trial period. In 11 paired villages, no further cases were recorded post-intervention, whereas in 7 collared villages there were 9 new clinical cases relative to controls. Over the trial period, 6,835 collars were fitted at the beginning of the 4 month sand fly season, of which 6.9% (95% C.I. 6.25%, 7.56%) were lost but rapidly replaced. Collar coverage (percent dogs collared) per village varied between 66% and 100%, with a mean annual coverage of 87% (95% C.I. 84·2, 89·0%). The variation in post-intervention clinical VL incidence was not associated with collar coverage, dog population size, implementation logistics, dog owner compliance, or other demographic variables tested. Larger reductions and greater persistence in incident case numbers (indicative of transmission) were observed in villages with higher pre-existing VL case incidence.

CONCLUSION

Community-wide deployment of collars can provide a significant level of protection against infantile clinical VL, achieved in this study by the local VL Control Program, demonstrating attributes desirable of a sustainable public health program. The effectiveness is not dissimilar to the community-level protection provided against human and canine infection with L. infantum.

Entomological surveys of Lutzomyia flaviscutellata and other vectors of cutaneous leishmaniasis in municipalities with records of Leishmania amazonensis within the Bragança region of Pará State, Brazil

In southeast Amazon, Lutzomyia (Nyssomyia) flaviscutellata is the incriminated vector of Leishmania (Leishmania) amazonensis, a causative agent of zoonotic cutaneous leishmaniasis (CL). The optimal methods for surveying Lu. flaviscutellata were investigated in the Bragança region, northeast Pará State, Brazil, selected for the presence of Le. amazonensis. The performances of modified Disney traps and CDC light traps were compared in four ecotopes within and around four village transects during the wet and dry seasons. The physiological age of female sand flies was estimated and natural infection by flagellates was evaluated by dissection. Disney traps were better for detecting the presence of Lu. flaviscutellata, while CDC traps performed well for detecting Lutzomyia (Nyssomyia) antunesi, suspected vector of Leishmania lindenbergi. The former was more abundant during the wet season, when female flies were naturally infected with Le. amazonensis. These findings identified the environments of local transmission. In order to improve surveys of Lu. flaviscutellata as part of integrated epidemiological surveillance of CL, our recommendations include focusing vector surveys with Disney traps on forest fragments where people work, during the seasonal peak of the vector. Further field studies are required to make model-based predictions of seasonal variations in the vectorial capacity of vector populations.

Species-specific ecological niche modelling predicts different range contractions for Lutzomyia intermedia and a related vector of Leishmania braziliensis following climate change in South America

BACKGROUND

Before 1996 the phlebotomine sand fly Lutzomyia neivai was usually treated as a synonym of the morphologically similar Lutzomyia intermedia, which has long been considered a vector of Leishmania braziliensis, the causative agent of much cutaneous leishmaniasis in South America. This report investigates the likely range changes of both sand fly species in response to a stabilisation climate change scenario (RCP4.5) and a high greenhouse gas emissions one (RCP8.5).

METHODS

Ecological niche modelling was used to identify areas of South America with climates currently suitable for each species, and then the future distributions of these climates were predicted based on climate change scenarios. Compared with the previous ecological niche model of L. intermedia (sensu lato) produced using the GARP algorithm in 2003, the current investigation modelled the two species separately, making use of verified presence records and additional records after 2001. Also, the new ensemble approach employed ecological niche modelling algorithms (including Maximum Entropy, Random Forests and Support Vector Machines) that have been widely adopted since 2003 and perform better than GARP, as well as using a more recent climate change model (HadGEM2) considered to have better performance at higher resolution than the earlier one (HadCM2).

RESULTS

Lutzomyia intermedia was shown to be the more tropical of the two species, with its climatic niche defined by higher annual mean temperatures and lower temperature seasonality, in contrast to the more subtropical L. neivai. These different latitudinal ranges explain the two species' predicted responses to climate change by 2050, with L. intermedia mostly contracting its range (except perhaps in northeast Brazil) and L. neivai mostly shifting its range southwards in Brazil and Argentina. This contradicts the findings of the 2003 report, which predicted more range expansion. The different findings can be explained by the improved data sets and modelling methods.

CONCLUSIONS

Our findings indicate that climate change will not always lead to range expansion of disease vectors such as sand flies. Ecological niche models should be species specific, carefully selected and combined in an ensemble approach.

Ecological Niche Modelling Predicts Southward Expansion of Lutzomyia (Nyssomyia) flaviscutellata (Diptera: Psychodidae: Phlebotominae), Vector of Leishmania (Leishmania) amazonensis in South America, under Climate Change

Vector borne diseases are susceptible to climate change because distributions and densities of many vectors are climate driven. The Amazon region is endemic for cutaneous leishmaniasis and is predicted to be severely impacted by climate change. Recent records suggest that the distributions of Lutzomyia (Nyssomyia) flaviscutellata and the parasite it transmits, Leishmania (Leishmania) amazonensis, are expanding southward, possibly due to climate change, and sometimes associated with new human infection cases. We define the vector's climatic niche and explore future projections under climate change scenarios. Vector occurrence records were compiled from the literature, museum collections and Brazilian Health Departments. Six bioclimatic variables were used as predictors in six ecological niche model algorithms (BIOCLIM, DOMAIN, MaxEnt, GARP, logistic regression and Random Forest). Projections for 2050 used 17 general circulation models in two greenhouse gas representative concentration pathways: "stabilization" and "high increase". Ensemble models and consensus maps were produced by overlapping binary predictions. Final model outputs showed good performance and significance. The use of species absence data substantially improved model performance. Currently, L. flaviscutellata is widely distributed in the Amazon region, with records in the Atlantic Forest and savannah regions of Central Brazil. Future projections indicate expansion of the climatically suitable area for the vector in both scenarios, towards higher latitudes and elevations. L. flaviscutellata is likely to find increasingly suitable conditions for its expansion into areas where human population size and density are much larger than they are in its current locations. If environmental conditions change as predicted, the range of the vector is likely to expand to southeastern and central-southern Brazil, eastern Paraguay and further into the Amazonian areas of Bolivia, Peru, Ecuador, Colombia and Venezuela. These areas will only become endemic for L. amazonensis, however, if they have competent reservoir hosts and transmission dynamics matching those in the Amazon region.

Climate, environmental and socio-economic change: weighing up the balance in vector-borne disease transmission

Arguably one of the most important effects of climate change is the potential impact on human health. While this is likely to take many forms, the implications for future transmission of vector-borne diseases (VBDs), given their ongoing contribution to global disease burden, are both extremely important and highly uncertain. In part, this is owing not only to data limitations and methodological challenges when integrating climate-driven VBD models and climate change projections, but also, perhaps most crucially, to the multitude of epidemiological, ecological and socio-economic factors that drive VBD transmission, and this complexity has generated considerable debate over the past 10-15 years. In this review, we seek to elucidate current knowledge around this topic, identify key themes and uncertainties, evaluate ongoing challenges and open research questions and, crucially, offer some solutions for the field. Although many of these challenges are ubiquitous across multiple VBDs, more specific issues also arise in different vector-pathogen systems.

Origins of Wohlfahrtia magnifica in Italy based on the identification of mitochondrial cytochrome b gene haplotypes

To identify the geographical origins of larvae of Wohlfahrtia magnifica (Diptera: Sarcophagidae) causing myiasis of sheep in Italy, comparative DNA sequence analysis of the mitochondrial cytochrome b gene was performed, based on gene fragments amplified by PCR from genomic DNA isolated from individual specimens. DNA extractions of 19 larvae from Lazio, Molise, Puglia, and Sicilia generated 17 readable sequences homologous to 2 haplotypes, either CB_magn01 or CB_magn02; DNA extracts from 4 adult flies from Calabria (reared from larvae) produced 4 readable sequences belonging to the haplotype CB_magn01. The two haplotypes found represent both the East and West phylogenetic lineages of W. magnifica, which is consistent with the species' arrival from central/southeast Europe (East lineage) and/or from southwest Europe/northwest Africa (West lineage). This is the first report of the sympatric occurrence of the two lineages, which could have resulted from natural or human-assisted dispersal. Polymorphic nuclear loci will have to be characterized in order to explain the origins and lack of mitochondrial haplotype diversity of this pest in Italy, where it poses increasing veterinary problems.

Recent advances in phlebotomine sand fly research related to leishmaniasis control

Phlebotomine sand flies are the subject of much research because of the role of their females as the only proven natural vectors of Leishmania species, the parasitic protozoans that are the causative agents of the neglected tropical disease leishmaniasis. Activity in this field was highlighted by the eighth International Symposium on Phlebotomine Sand flies (ISOPS) held in September 2014, which prompted this review focusing on vector control. Topics reviewed include: Taxonomy and phylogenetics, Vector competence, Genetics, genomics and transcriptomics, Eco-epidemiology, and Vector control. Research on sand flies as leishmaniasis vectors has revealed a diverse array of zoonotic and anthroponotic transmission cycles, mostly in subtropical and tropical regions of Africa, Asia and Latin America, but also in Mediterranean Europe. The challenge is to progress beyond descriptive eco-epidemiology, in order to separate vectors of biomedical importance from the sand fly species that are competent vectors but lack the vectorial capacity to cause much human disease. Transmission modelling is required to identify the vectors that are a public health priority, the ones that must be controlled as part of the integrated control of leishmaniasis. Effective modelling of transmission will require the use of entomological indices more precise than those usually reported in the leishmaniasis literature.

Environmental and phylogeographical determinants of the distribution of the Old World screwworm fly in Indonesia

The Old World screwworm (OWS) fly, Chrysomya bezziana, is an obligate parasite of livestock, and the myiasis caused by its larval infestations is economically important in Indonesia. The current spatial distribution of such a pest depends on two main factors: the current environmental conditions in which it can survive; and, its ability to occupy those environments by dispersal, which can be inferred from phylogeography and population genetics. These indicate that all OWS flies in Indonesia have mitochondrial cytochrome b (cyt b) haplotypes of the Asian lineage, and the regional separation of its four sub-lineages is the result of infrequent long-distance dispersal. We report the first investigation to associate regional cyt b sub-lineages of the OWS fly with environmental variables. Principal Components Analysis was used to demonstrate that these sub-lineages are associated with very similar macro-climates throughout Indonesia. Then, a species distribution model for the OWS fly in Indonesia was obtained by using the Maxent program. This indicated that elevation captured information not given by other environmental variables, and cattle density provided the most useful information by itself. The results of our study provide some important leads for future research, which will require better, stratified sampling.

Improved method for screening mitochondrial cytochrome b markers to identify regional populations of the Old World screwworm fly and other myiasis agents

A new protocol was developed to overcome obstacles to the high-throughput sequence analysis of the 716-717 nucleotides at the carboxyl terminal of the mitochondrial gene cytochrome b (cyt b) of the myiasis flies Chrysomya bezziana and Wohlfahrtia magnifica. For both of these obligate parasites, cyt b haplotypes provide diagnostic markers for phylogeographic populations, markers that identify the origins of emerging populations causing economically important myiasis in livestock and, in the case of C. bezziana (Old World screwworm fly), could help select reproductively-compatible populations for use in the Sterile insect technique as part of area wide integrated pest management. High sequence quality is important for unambiguously detecting the few mutations that are diagnostic for regional cyt b haplotypes and their lineages. A key innovation is the design of a new forward primer for the specific PCR amplification and high-quality sequencing of cyt b. The improved protocol will facilitate the use of this established comparative cyt b sequence analysis, not only by teams lacking the resources for whole genome sequencing (WGS) but also by those requiring reference sequences for developing comparative mitogenomics based on WGS.

Phlebotomus (Paraphlebotomus) riouxi: a synonym of Phlebotomus chabaudi without any proven vectorial role in Tunisia and Algeria

Phlebotomus (Paraphlebotomus) riouxi Depaquit, Léger & Killick-Kendrick (Diptera: Psychodidae) was described as a typological species based on a few morphological characters distinguishing it from Phlebotomus (Paraphlebotomus) chabaudi Croset, Abonnenc & Rioux. The naming of P. riouxi coincided with its incrimination as a rural vector of Leishmania tropica Wright (junior synonym: Leishmania killicki Rioux, Lanotte & Pratlong) in Tataouine governorate, an arid region of southern Tunisia. The current report finds insufficient evidence to incriminate either phlebotomine sandfly as a vector of L. tropica in North Africa. Phlebotomus riouxi was found not to have the characteristics of a phylogenetic or biological species, and therefore it is synonymized with P. chabaudi. Both taxa were recorded together for the first time in Tunisia, in Tataouine, where three of 12 males showed intermediate morphology and both sexes of each taxon were not characterized by specific lineages of the nuclear gene elongation factor-1α or the mitochondrial gene cytochrome b, for which a long 3' terminal fragment is recommended for phlebotomine phylogenetics. This case study indicates that the eco-epidemiology of leishmaniasis should focus more on identifying key components of vectorial transmission that are susceptible to interventions for disease control, rather than on defining sibling species of vectors.

Epidemiology of visceral leishmaniasis

Leishmania species are the causative agents of leishmaniasis, a neglected tropical disease. These parasitic protozoans are usually transmitted between vertebrate hosts by the bite of blood sucking female phlebotomine sand flies. This review focuses on the two parasites causing most human visceral leishmaniasis (VL), which leads to substantial health problems or death for up to 400,000 people per year. Except for travel cases, Leishmania donovani infections are restricted to the (sub-)tropics of Asia and Africa, where transmission is mostly anthroponotic, while Leishmania infantum occurs in the drier parts of Latin America as well as in the Mediterranean climate regions of the Old World, with the domestic dog serving as the main reservoir host. The prevalence of VL caused by L. infantum has been declining where living standards have improved. In contrast, infections of L. donovani continue to cause VL epidemics in rural areas on the Indian subcontinent and in East Africa. The current review compares and contrasts these continental differences and suggests priorities for basic and applied research that might improve VL control. Transmission cycles, pathogenesis, diagnosis, treatment and prognosis, prevention (including vector control), surveillance, transmission modeling, and international control efforts are all reviewed. Most case detection is passive, and so routine surveillance does not usually permit accurate assessments of any changes in the incidence of VL. Also, it is not usually possible to estimate the human inoculation rate of parasites by the sand fly vectors because of the limitations of survey methods. Consequently, transmission modeling rarely passes beyond the proof of principle stage, and yet it is required to help develop risk factor analysis for control programs. Anthroponotic VL should be susceptible to elimination by rapid case detection and treatment combined with local vector control, and one of the most important interventions may well be socioeconomic development.

Biology of phlebotomine sand flies as vectors of disease agents

Phlebotomines are the sole or principal vectors of Leishmania, Bartonella bacilliformis, and some arboviruses. The coevolution of sand flies with Leishmania species of mammals and lizards is considered in relation to the landscape epidemiology of leishmaniasis, a neglected tropical disease. Evolutionary hypotheses are unresolved, so a practical phlebotomine classification is proposed to aid biomedical information retrieval. The vectors of Leishmania are tabulated and new criteria for their incrimination are given. Research on fly-parasite-host interactions, fly saliva, and behavioral ecology is reviewed in relation to parasite manipulation of blood feeding, vaccine targets, and pheromones for lures. Much basic research is based on few transmission cycles, so generalizations should be made with caution. Integrated research and control programs have begun, but improved control of leishmaniasis and nuisance-biting requires greater emphasis on population genetics and transmission modeling. Most leishmaniasis transmission is zoonotic, affecting the poor and tourists in rural and natural areas, and therefore control should be compatible with environmental conservation.

No recent adaptive selection on the apyrase of Mediterranean Phlebotomus: implications for using salivary peptides to vaccinate against canine leishmaniasis

Vaccine development is informed by a knowledge of genetic variation among antigen alleles, especially the distribution of positive and balancing selection in populations and species. A combined approach using population genetic and phylogenetic methods to detect selective signatures can therefore be informative for identifying vaccine candidates. Parasitic Leishmania species cause the disease leishmaniasis in humans and mammalian reservoir hosts after inoculation by female phlebotomine sandflies. Like other arthropod vectors of disease agents, sandflies use salivary peptides to counteract host haemostatic and immunomodulatory responses during bloodfeeding, and these peptides are vaccine candidates because they can protect against Leishmania infection. We detected no contemporary adaptive selection on one salivary peptide, apyrase, in 20 populations of Phlebotomus ariasi, a European vector of Leishmania infantum. Maximum likelihood branch models on a gene phylogeny showed apyrase to be a single copy in P. ariasi but an ancient duplication event associated with temporary positive selection was observed in its sister group, which contains most Mediterranean vectors of L. infantum. The absence of contemporary adaptive selection on the apyrase of P. ariasi may result from this sandfly's opportunistic feeding behaviour. Our study illustrates how the molecular population genetics of arthropods can help investigate the potential of salivary peptides for disease control and for understanding geographical variation in vector competence.

Should sand fly taxonomy predict vectorial and ecological traits?

I review species concepts, the taxonomy of phlebotomine sand flies, and some transmission cycles of leishmaniasis in order to illustrate the difficulties of classifying these vectors in a way that will be ideal both for medical parasitologists and sand fly specialists. Choices will have to be made between different classifications, either maintaining a practical one containing few vectorial genera (mostly Phlebotomus for the Old World and Lutzomyia for the Neotropics) or changing the generic names of many vectors so that the classification represents an evolutionary hypothesis. However, sand flies also transmit arboviruses and members of other sand fly genera bite humans, and so vectorial status alone might not provide the criteria for recognizing only a few genera. Vectorial roles are often determined by species-level co-evolution of susceptibility to Leishmania species, with selection being initiated and maintained by ecological contacts. There is only imperfect co-cladogenesis of genus-level groups or subgeneric complexes of sand flies and Leishmania species. Natural hybridization between sand fly species has been recorded in several species complexes, and this highlights the need to focus on gene flow and the distribution of phenotypes of biomedical importance, not on taxa.

Phlebotomus caucasicus and Phlebotomus mongolensis (Diptera: Psychodidae): indistinguishable by the mitochondrial cytochrome b gene in Iran

Diagnostic molecular markers for the females of Phlebotomus (Paraphlebotomus) caucasicus and P. mongolensis were sought by characterizing from individual Iranian specimens a gene fragment, namely mitochondrial cytochrome b, that had previously proven useful for the taxonomy of phlebotomine sandflies. Males of both species were used as reference material because their external genitalia provide the only diagnostic morphological characters. A phylogenetic analysis of the new sequences, and those previously reported for P. grimmi, found no support for recognizing more than one species (P. caucasicus s.l.) in Iran. Most of the genetic variation was geographical. An absence of lineage sorting was demonstrated, and it is proposed that any search for species-specific molecular markers for these three taxonomic species should be continued by applied biologists only if there is better evidence for associating any one of them with phenotypes important for understanding the transmission of Leishmania species in foci of zoonotic cutaneous leishmaniasis.

Leishmaniasis emergence in Europe

Leishmaniasis emergence in Europe is reviewed, based on a search of literature up to and including 2009. Topics covered are the disease, its relevance, transmission and epidemiology, diagnostic methods, treatment, prevention, current geographical distribution, potential factors triggering changes in distribution, and risk prediction. Potential factors triggering distribution changes include vectorial competence, importation or dispersal of vectors and reservoir hosts, travel, and climatic/environmental change. The risk of introducing leishmaniasis into the European Union (EU) and its spread among Member States was assessed for the short (2-3 years) and long term (15-20 years). There is only a low risk of introducing exotic Leishmania species because of the absence of proven vectors and/or reservoir hosts. The main threat comes from the spread of the two parasites endemic in the EU, namely Leishmania infantum, which causes zoonotic visceral and cutaneous leishmaniasis in humans and the domestic dog (the reservoir host), and L. tropica, which causes anthroponotic cutaneous leishmaniasis. The natural vector of L. tropica occurs in southern Europe, but periodic disease outbreaks in Greece (and potentially elsewhere) should be easily contained by surveillance and prompt treatment, unless dogs or other synanthropic mammals prove to be reservoir hosts. The northward spread of L. infantum from the Mediterranean region will depend on whether climate and land cover permit the vectors to establish seasonal biting rates that match those of southern Europe. Increasing dog travel poses a significant risk of introducing L. infantum into northern Europe, and the threat posed by non-vectorial dog-to-dog transmission should be investigated.

Leishmaniasis emergence in Europe

Leishmaniasis emergence in Europe is reviewed, based on a search of literature up to and including 2009. Topics covered are the disease, its relevance, transmission and epidemiology, diagnostic methods, treatment, prevention, current geographical distribution, potential factors triggering changes in distribution, and risk prediction. Potential factors triggering distribution changes include vectorial competence, importation or dispersal of vectors and reservoir hosts, travel, and climatic/environmental change. The risk of introducing leishmaniasis into the European Union (EU) and its spread among Member States was assessed for the short (2-3 years) and long term (15-20 years). There is only a low risk of introducing exotic Leishmania species because of the absence of proven vectors and/or reservoir hosts. The main threat comes from the spread of the two parasites endemic in the EU, namely Leishmania infantum, which causes zoonotic visceral and cutaneous leishmaniasis in humans and the domestic dog (the reservoir host), and L. tropica, which causes anthroponotic cutaneous leishmaniasis. The natural vector of L. tropica occurs in southern Europe, but periodic disease outbreaks in Greece (and potentially elsewhere) should be easily contained by surveillance and prompt treatment, unless dogs or other synanthropic mammals prove to be reservoir hosts. The northward spread of L. infantum from the Mediterranean region will depend on whether climate and land cover permit the vectors to establish seasonal biting rates that match those of southern Europe. Increasing dog travel poses a significant risk of introducing L. infantum into northern Europe, and the threat posed by non-vectorial dog-to-dog transmission should be investigated.

Morphological and mitochondrial DNA characters for identification and phylogenetic analysis of the myiasis-causing flesh fly Wohlfahrtia magnifica and its relatives, with a description of Wohlfahrtia monegrosensis sp. n. Wyatt & Hall

Wohlfahrtia magnifica (Schiner) (Diptera: Sarcophagidae) is a major cause of traumatic myiasis in livestock in Central and Eastern Europe and in countries bordering the Mediterranean. The present study explored the utility of external body characters, genitalia characters and mitochondrial DNA characters for identification of this and related species in the subfamily Paramacronychiinae. Sequence analyses of the 3' terminal 273 bp of the mitochondrial cytochrome b gene revealed two lineages of W. magnifica, one from Spain and France and the other from the rest of Eurasia, differing by only two base pairs. Phylogenetic analysis of cytochrome b showed that W. magnifica and Wohlfahrtia vigil Walker were sister species; this conclusion was not contradicted by a phylogenetic analysis of the morphological characters. Based on cytochrome b, the genetic distance between specimens of W. vigil from Europe and North America was sufficiently large to justify the recognition of more than one species. A new species, Wohlfahrtia monegrosensis, from northern Spain, was described, based on morphology and cytochrome b. A unique combination of external body characters of males or females were diagnostic for W. magnifica, the W. vigil group and Wohlfahrtia bella, but only the genitalia characters were diagnostic for all nine species studied.

Molecular genetic analysis of populations of Wohlfahrt's wound myiasis fly, Wohlfahrtia magnifica, in outbreak populations from Greece and Morocco

Wohlfahrt's wound myiasis fly, Wohlfahrtia magnifica (Schiner) (Diptera: Sarcophagidae), is the most important cause of traumatic myiasis in the southern Palaearctic region. Larval stages are obligate parasites and the wounds caused by infestations are very similar to those caused by Old and New World screwworm flies. During the last decade, W. magnifica appears to have expanded its range to parts of northern and central Morocco, and to Crete, Greece. Specimens of W. magnifica were collected in Morocco and Crete either as larvae (preserved in 80% ethanol) or as adults (dry-pinned). Comparison specimens were collected in Spain, Hungary and mainland Greece. A DNA fragment containing the 3' 715 base pairs of the mitochondrial cytochrome b gene was amplified by polymerase chain reaction from each of 132 larvae or adults of W. magnifica and the amplicons were directly sequenced and analysed phylogeographically. Twelve cytochrome b haplotypes were detected. All haplotypes from Morocco belonged to a lineage that included specimens from the Iberian peninsula, and restricted mixing of central and northern populations in Morocco was demonstrated. Cytochrome b haplotyping combined with an analysis of larval size provided clear evidence of multiple infestations of hosts in all geographical areas, with one quarter of wounds containing larvae from two to at least four females. More than 80% of specimens from Crete contained a haplotype predominating in mainland Greece and Hungary. Our survey indicated that wohlfahrtiosis was more widespread in northern and central Morocco than previously recorded by government veterinarians. However, the prevalence of wohlfahrtiosis was low (< 1%). The high genetic diversity of Moroccan populations is consistent with longterm endemicity, rather than recent introduction. Crete showed a higher prevalence of wohlfahrtiosis (< or = 15%) and less genetic diversity of W. magnifica, which is consistent with a recent introduction. The western and eastern Mediterranean lineages may have been isolated in different Pleistocene ice-age refugia, from which there has been limited post-glacial dispersal.

Phylogeography and recent emergence of the Old World screwworm fly, Chrysomya bezziana, based on mitochondrial and nuclear gene sequences

A previous study had identified an African and an Asian race of the Old World screwworm fly, Chrysomya bezziana Villeneuve (Diptera: Calliphoridae), based on the 3' terminal 279 basepairs (bp) of the mitochondrial cytochrome b gene. The current study improved the phylogeographic resolution of cytochrome b for this species by characterizing more of the gene (the 3' terminal 715 bp) and by sampling more geographical populations, including Oman, Iran, Hong Kong and the Indonesian islands of Sulawesi and East Sumba. Strong support was found for recognizing an African race, but not for a monophyletic Asian race. The cladistic and genealogical relationships among the Asian populations were complex. There was sufficient genetic homogeneity throughout separate regions (mainland Asia and each Indonesian island) to suggest that there are no reproductive barriers within each region that might necessitate the production of more than one strain for control by the sterile insect technique (SIT). Primers were designed for the amplification by polymerase chain reaction of two nuclear loci, the highly conserved elongation factor-1alphagene and the less conserved white gene, and the preliminary results indicated that these genes showed the same pattern of small-scale regional variation as cytochrome b. The cytochrome b haplotypes are useful markers for identifying the geographical origins of any emerging infestations of the species: the absence of Indonesian and African haplotypes in the Middle East demonstrates that the large-scale transport of livestock is not spreading Old World screwworm.

Genetic diversity of populations of Old World screwworm fly, Chrysomya bezziana, causing traumatic myiasis of livestock in the Gulf region and implications for control by sterile insect technique

Fly larvae were collected from 181 cases of traumatic myiasis in livestock in 10 regions of four countries in the Middle East Gulf region: Iran, Iraq, Saudi Arabia and Oman. The predominant fly species responsible for cases was the Old World screwworm (OWS) fly, Chrysomya bezziana Villeneuve (Diptera: Calliphoridae). In cases from Iran and Oman, which included non-OWS fly species, OWS fly was found solely responsible for 67.6% of cases and jointly with other fly species for a further 12.7% of cases. The major hosts were sheep and goats, together comprising 84.6% of the total, which reflects their predominance among the livestock of these Gulf countries. The major site of wounding on sheep and goats was the tail (40.3%), followed by female genitalia (14.0%). The 3' terminal 715 nucleotides of the mitochondrial cytochrome b gene were sequenced for 178 larvae of OWS. Five haplotypes were identified: three had been recorded previously in the region (two were common throughout and one was unique to Oman), and two were newly identified, one from southern Iraq and the other from Saudi Arabia, both in regions sampled for the first time. The haplotypes varied from one another only at one or two nucleotide sites, equivalent to an intraspecific difference of 0.14-0.28% across the entire 715-bp fragment. There was a single statistically significant association between host species and haplotype in Saudi Arabia, a first such record for OWS fly. The small degree of genetic diversity between geographical populations of OWS fly within the Gulf region suggests that a single Gulf colony could be used to implement the sterile insect technique within an integrated control programme.

PCR detection and sequencing of parasite ITS-rDNA gene from reservoirs host of zoonotic cutaneous leishmaniasis in central Iran

Leishmania major is the causative agent of zoonotic cutaneous leishmaniasis (ZCL) in which gerbils are the reservoir host. ZCL is of great public health importance in Iran. In the current investigation, nested polymerase chain reaction (PCR) protocols were used to amplify a region of the ribosomal RNA amplicon of Leishmania (ITS1-5.8S rRNA gene). The PCR assays detected L. major in three rodent species: Rhombomis opimus, Meriones lybicus and, for first time, Meriones persicus. L. major parasite was found in Natanz, Isfahan Province in the center of Iran in a focus of rural zoonotic cutaneous leishmaniasis. Four L. major infections were detected in R. opimus species, three in M. Lybicus, and two in M. persicus. All nine rodent infections of L. major were found to be the same haplotype based on the PCR detection and sequencing of parasite ITS-ribosomal DNA gene. In addition, also for the first time, the nested PCR assays detected Leishmania tropica only in one M. persicus. Allied to studies in country, the new findings mean that past conclusions about the reservoir of L. major in Iran must be treated with caution. Finding two Leishmania species in different rodent species as reservoir in Iran, therefore, careful molecular eco-epidemiological investigations will be an essential part of modeling the roles of different gerbil species in maintaining and spreading ZCL foci.

Leishmaniasis emergence and climate change

Spatio-temporal modelling of the distributions of the leishmaniases and their sandfly vectors is reviewed in relation to climate change. Many leishmaniases are rural zoonoses, and so there is a foundation of descriptive ecology and qualitative risk assessment. Dogs are widespread reservoir hosts of veterinary importance. Recent statistical modelling has not always produced novel general conclusions, exemplifying the difficulty of applying models outside the original geographical region. Case studies are given for transmission cycles involving both cutaneous and visceral leishmaniasis in the Old World and the Americas. An important challenge is to integrate statistical spatial models based mainly on climate with more explanatory biological models. Ecological niche models pose difficulties because of the number of assumptions. A positive association has been reported between the El Niño cycle and the annual incidence of visceral leishmaniasis in Brazil, but more basic research is needed before tackling other climate-change scenarios, including leishmaniasis emergence in northern Europe.

Nested PCRs and sequencing of nuclear ITS-rDNA fragments detect three Leishmania species of gerbils in sandflies from Iranian foci of zoonotic cutaneous leishmaniasis

OBJECTIVE

To identify and understand the natural transmission cycles of Leishmania in Iranian sandflies.

METHOD

Nested PCR protocols were developed to amplify two regions of the ribosomal RNA amplicon of Leishmania (ITS1-5.8S rRNA gene, and a microsatellite DNA region of ITS2), which were species-specific by DNA sequence or fragment size.

RESULTS

The PCR assays detected in Iranian sandflies not only Leishmania major but also for the first time L. turanica and L. gerbilli sensu lato, two other parasites of the great gerbil. All three parasites were found in the northeast and centre of Iran, in two foci of rural Zoonotic Cutaneous Leishmaniasis (ZCL) caused by L. major. Fifty infections were detected in common sandfly species: at least six geographically differentiated haplotypes of L. major in four to five sandfly species; one strain of L. gerbilli s.l. in five to six sandfly species and one strain of L. turanica in one sandfly species.

CONCLUSION

Past conclusions about the transmission cycles of L. major in Iran should be treated with caution. Careful molecular eco-epidemiological investigations are essential for modelling the roles of different sandfly species in maintaining and spreading ZCL foci. Even if non-pathogenic to humans, frequent inoculations of L. turanica by sandflies might alter the efficacy of vaccines against L. major. Phlebotomus papatasi is probably the key vector in many ZCL foci because of its abundance and high infection rates with both L. major and L. turanica.

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.

Mitochondrial 16S rDNA analysis of Tunisian androctonus species (Scorpions, Buthidae): phylogenetic approach

Tunisian Androctonus species, for long time discussed, were recognized on the basis of mitochondrial 16S rDNA sequences. Although the analysed nucleotide sequence is rather short (about 300 bp), the obtained phlogenetic trees revealed that A. amoreuxi and A. aeneas form two well-supported sister clades against A. australis haplotypes. Each specimen of the very rare species A. aeneas showed a specific haplotype, but together formed a well-defined clade. Some A. amoreuxi specimens highlighted unidirectional mitochondrial introgression from neighbouring A. australis population. Within A. australis, previously described, subspecies subdivision (A. a .hector and A. a. garzonii) was not supported.

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.

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.

Distribution of sandfly species in relation to canine leishmaniasis from the Ebro Valley to Valencia, northeastern Spain

In Spain, only two of the 12 recorded species of sandflies, Phlebotomus (Larroussius) ariasi Tonnoir and P. (L.) perniciosus Newstead, are proven vectors of Leishmania infantum Nicolle, the causative agent of endemic leishmaniasis. Studies of the distributions of phlebotomine sandflies are important for evaluating the possible effects of climate warming on any northward or altitudinal range shifts of leishmaniasis or the other diseases they transmit. We describe a recent sandfly survey in Spain, starting in the northern Ebro Valley and continuing southeast into the Levante region of the Mediterranean coast. Sandflies (P. ariasi only) were found for the first time in the northern province of Alava, in the upper Ebro Valley, where cases of canine leishmaniasis have been described during the last decade. Throughout the provinces sampled, P. ariasi predominated over P. perniciosus in cooler bioclimatic zones, and this statistically significant pattern was more marked than that with higher altitudes.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

A mitochondrial DNA phylogeny indicates close relationships between populations of Lutzomyia whitmani (Diptera: Psychodidae, Phlebotominae) from the rain-forest regions of Amazônia and northeast Brazil

Phylogenetic analysis of all 31 described mitochondrial (cytochrome b) haplotypes of Lutzomyia whitmani demonstrated that new material from the State of Rondônia, in southwest Amazônia, forms a clade within a lineage found only in the rain-forest regions of Brazil. This rain-forest lineage also contains two other clades of haplotypes, one from eastern Amazônia and one from the Atlantic forest zone of northeast Brazil (including the type locality of the species in Ilhéus, State of Bahia). These findings do not favour recognizing two allopatric cryptic species of L. whitmani, one associated with the silvatic transmission of Leishmania shawi in southeast Amazônia and the other with the peridomestic transmission of Le. braziliensis in northeast Brazil. Instead, they suggest that there is (or has been in the recent past) a continuum of inter-breeding populations of L. whitmani in the rain-forest regions of Brazil.

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.

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.

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.

A single isoform of the Na+/K(+)-ATPase alpha-subunit in Diptera: evidence from characterization of the first extracellular domain

The first extracellular domain of the alpha-subunit of the Na+/K+-ATPase (sodium/potassium pump) is functionally important, affecting sensitivity of the enzyme to cardiac glycosides (e.g. ouabain) and being implicated in the transport of K+. This domain is also variable among mammalian isoforms of the alpha-subunit. Using PCR, we have isolated from seven insect species with contrasting physiologies a DNA fragment containing this region, in order to help determine whether tissue-specific expression might be associated with isoforms encoded by a gene family, as it is in mammals. A single sequence (with one ORF) characteristic of Na+/K+-ATPase was obtained from genomic DNA of each species. Only the fragment from Manduca sexta contained an intron, but at a location different to that found in mammals. For all Diptera so far characterized, the species phylogeny is the same as the alpha-subunit gene phylogeny (based on the sequences of the first extracellular domain and flanking transmembrane domains). The results strongly indicate a single, ouabain-sensitive isoform of the alpha-subunit of Na+/K+-ATPase is present in Diptera.