Cell density quantification with TurboSPI: R2* mapping with compensation for off-resonance fat modulation

OBJECTIVE

Tracking the migration of superparamagnetic iron oxide (SPIO)-labeled immune cells in vivo is valuable for understanding the immunogenic response to cancer and therapies. Quantitative cell tracking using TurboSPI-based R₂* mapping is a promising development to improve accuracy in longitudinal studies on immune recruitment. However, off-resonance fat signal isochromats lead to modulations in the signal time-course that can be erroneously fit as R₂* signal decay, overestimating the density of labeled cells, while excluding voxels with fat-typical modulations results in underestimation of cell density in voxels with mixed content. Approaches capable of accurate R₂* estimation in the presence of fat are needed.

METHODS

We propose a dual-decay (separate R_2f* and R_2w* for fat and water) Dixon-based signal model that accounts for the presence of fat in a voxel to provide better estimates of SPIO-induced dephasing. This model was tested in silico, in phantoms with varying quantities of fat and SPIO-labeled cells, and in 5 mice injected with SPIO-labeled CD8+ T cells.

RESULTS

In silico single voxel simulations illustrate how the proposed dual-decay model provides stable R_2w* estimates that are invariant to fat content. The proposed model outperforms previous methods when applied to in vitro samples of SPIO-labeled cells and oil prepared with oil content ≥ 15%. Preliminary in vivo results show that, compared to previous methods, the dual-decay model improves the balance of R₂* mapping in fat-dense areas, which will yield more reliable analysis in future cell tracking studies.

DISCUSSION

The proposed model is a promising tool for quantitative TurboSPI R₂* cell tracking, with further refinements offering the possibility of better specificity and sensitivity.

Climate change: effects on animal disease systems and implications for surveillance and control

Climate driven and other changes in landscape structure and texture, plus more general factors, may create favourable ecological niches for emerging diseases. Abiotic factors impact on vectors, reservoirs and pathogen bionomics and their ability to establish in new ecosystems. Changes in climatic patterns and in seasonal conditions may affect disease behaviour in terms of spread pattern, diffusion range, amplification and persistence in novel habitats. Pathogen invasion may result in the emergence of novel disease complexes, presenting major challenges for the sustainability of future animal agriculture at the global level. In this paper, some of the ecological mechanisms underlying the impact of climatic change on disease transmission and disease spread are further described. Potential effects of different climatic variables on pathogens and host population dynamics and distribution are complex to assess, and different approaches are used to describe the underlying epidemiological processes and the availability of ecological niches for pathogens and vectors. The invasion process can disrupt the long-term co-evolution of species. Pathogens adhering to an r-type strategy (e.g. RNA viruses) may be more inclined to encroach on a novel niche resulting from climate change. However, even when linkage between disease dynamics and climate change are relatively strong, there are other factors changing disease behaviour, and these should be accounted for as well. Overall vulnerability of a given ecosystem is a key variable in this regard. The impact of climate-driven changes varies in different parts of the world and in the different agro-climatic zones. Perhaps priority should go to those geographical areas where the integrity of the ecosystem is most severely affected and the adaptability, in terms of robustness and sustainability of response, relatively low.

[Impact of climatic change on the epidemiology of diseases]

Potential climate driven changes in the epidemiology of human and animal disease are widely discussed and complex to assess. Recent spreads of exotic pathogens or vectors feed speculations; although most of these introductions are mainly linked to the increased worldwide traffic, trade of goods and transportation of animal and human, abiotic factors are known to impact on vectors and pathogens bionomics and their ability to establish in new ecosystems; altogether changes in climatic patterns and in seasonal conditions may affect disease behaviour in term of spread pattern, diffusion range, amplification and persistence in novel habitats. Invasion may result in the emergence of novel disease processes, presenting major challenges for the epidemiologists. In this paper, some of the ecological mechanisms underlying the impact of climatic change on disease transmission and disease spread are further described. Potential effects of different climatic variables on pathogens and hosts population dynamics and distributions are complex to assess and different approaches are used to describe the dynamics in ecological range and the availability of ecological niches for pathogens and vectors. However even when linkage between disease dynamics and climate change are relatively strong, there are always other factors also changing disease behaviour and these should be accounted for as well.

Mark-release-recapture of sand flies fed on leishmanial dogs: the natural life-cycle of Leishmania infantum in Phlebotomus ariasi

Wild-caught Phlebotomus ariasi Tonnoir permitted to feed on dogs infected with Leishmania infantum Nicolle were marked with fluorescent powder and released into their natural habitat in an uninhabited area of the Cévennes in southern France. Over a period of 29 days after release, 253 females were recaptured with CDC miniature light traps or by active search at night with portable UV lamps. The ovaries and infections in the alimentary tract were then examined. The females oviposited 6 nights after in infecting blood meal. Second blood meals were never taken during the maturation of eggs. During the first ovarian cycle, midgut infections with promastigotes were only moderately heavy. The intensity of infection increased markedly during the second ovarian cycle and, in the third ovarian cycle, the first pharynx infected with paramastigotes was seen (on day 19). From day 19 to day 29, 76% of the flies had pharyngeal infections. Three out of 19 sand flies with pharyngeal infections recaptured during this period had metacyclic promastigotes in their mouthparts. The long time required for parasites to reach the proboscis in completely natural conditions suggests that their presence in the mouthparts is not a prerequisite for transmission by bite. It is more likely that transmission is most commonly by the regurgitation of metacyclic promastigotes from the thoracic midgut following damage to the stomodaeal valve by chitinase produced by the parasite during its development in the gut of the fly. Nevertheless, it is reasonable to assume that the bite of a fly with metacyclic promastigotes in the proboscis (or salivary glands) would also be infective.

Isoenzymatic identification of Leishmania isolates from repeated clinical human leishmaniasis episodes in Catalonia (Spain)

Forty human strains of Leishmania infantum isolated in 1985-99 from 17 patients with repeated cutaneous, mucosal or visceral leishmaniasis episodes in Catalonia (Spain) were examined by isoenzyme electrophoresis. Six zymodemes were revealed: MON-1, MON-24, MON-28, MON-29, MON-33 and MON-34. In 2 patients 2 different zymodemes were identified in consecutive episodes.

[Phlebotomines of the Isle of Cyprus. III. Species inventory ]

Three surveys on canine leishmaniasis were carried out in Cyprus (1993, 1998 and 1999) emphasise the presence of eleven species of phlebotomine sandflies: Phlebotomus (Phlebotomus) papatasi, P. (Paraphlebotomus) alexandri, P. (Pa.) jacusieli (first mention in Cyprus), P. (Pa.) sergenti, P. (Larroussius) galilaeus, P. (L.) tobbi, P. (Transphlebotomus) economidesi, P. (T.) mascittii, Sergentomyia (Sergentomyia) azizi (its specific statute is validated by the authors), S. (S.) fallax et S. (S.) minuta. P. (Adlerius) kyreniae was not caught during the surveys. The authors propose hypothesis of settlement of the island by phlebotomine sandflies according this species inventory. A first migration period took probably place during the Miocene time and a second one during the Pleistocene time.

Molecular systematics of the phlebotomine sandflies of the subgenus Paraphlebotomus (diptera, psychodidae, phlebotomus) based on ITS2 rDNA sequences. Hypotheses Of dispersion and speciation

Phylogenetic Paraphlebotomus relationships are inferred by a study based on the sequences of ITS2, which has been sequenced in nine Paraphlebotomus species: P. alexandri, P. andrejevi, P. jacusieli, P. kazeruni, P. mireillae, P. mongolensis, P. saevus, P. sergenti and P. similis and in two out-groups species of the subgenus Phlebotomus: P. papatasi and P. duboscqi. Paraphlebotomus alexandri appears as the sister group of all other Paraphlebotomus sandflies. Among the other species, three groupings are clearly highlighted: andrejevi and mongolensis; mireillae and saevus; jacusieli, kazeruni, sergenti and similis. These groupings are related to speculations about the migration of Paraphlebotomus from a centre of dispersion located in the Middle East sometime from the early Eocene to the late Miocene.

[Phlebotomine sandflies (Diptera-Psychodidae) of the isle of Cyprus. II--Isolation and typing of Leishmania (Leishmania infantum Nicolle, 1908 (zymodeme MON 1) from Phlebotomus (Larroussius) tobbi Adler and Theodor, 1930]

During two surveys conducted in Cyprus (August 1998 and September 1999), 2,910 phlebotomine sandflies females were caught by CDC miniature light traps then dissected under binocular and examined on microscope. Eleven species were identified: Phlebotomus papatasi, P. sergenti, P. jacusieli, P. alexandri, P. tobbi, P. galilaeus, P. mascittii, P. economidesi, Sergentomyia fallax, S. minuta et S. azizi. The Larroussius species (P. galilaeus and P. tobbi) are the most abundant (more than 60% of our captures). Promastigotes were isolated from one specimen identified as P. tobbi. A Leishmania stock was successfully cultured and identified by isoenzyme characterisation as belonging to L. infantum zymodeme MON 1. The same zymodeme was isolated and identified from four dogs too. Because of the absence of usual vectors of L. infantum in the eastern part of the Mediterranean basin (P. neglectus and P. syriacus), and according to its distribution in Cyprus, P. tobbi constitute certainly a good local vector. It seems to be not very anthropophilic, that could explain the very few human cases.

Enzymatic polymorphism and phylogenetic relationships in Leishmania Ross, 1903 (Sarcomastigophora: Kinetoplastida): a case study in Colombia

Leishmaniasis is widespread in Colombia and is found in 30 of 32 Departments. More than 200 infection zones have been reported from different regions, which vary from sea-level to an altitude of 2,300 m along the Atlantic Coast, Pacific coast, Amazon basin, Cauca and Magdalena valleys. We report 76 Leishmania stocks isolated from humans, dogs and phlebotomine hosts. Isoenzyme electrophoresis revealed 16 zymodemes, which could be divided into four phylogenetic complexes, i.e., L. braziliensis, L. amazonensis, L. guyanensis/panamensis and L. infantum. Three zymodemes became integrated into the subgenus Leishmania and the other zymodemes into the subgenus Viannia. Cutaneous infections were due to the L. braziliensis (9.2%) and L. guyanensis/panamensis (85.54%) complexes. Mucous secondary involvement was due to the L. braziliensis and L. guyanensis/panamensis complexes. In this work the specific status of L. (V.) guyanensis and L. (V.) panamensis is discussed.

[Canine leishmaniasis from Leishmania infantum: value and production of the latex test. Ecoepidemiologic applications]

The authors relate the realization, evaluation and eco-epidemiological applications of a "field-test": the agglutination of latex particles coated with a soluble antigen of Leishmania infantum in the presence of homologous antibodies. Evaluated on 1,035 canine sera, the sensitivity of the latex agglutination test (LAT) was 93.4% compared to the indirect fluorescent antibody test (IFAT). 90 node cultures were carried out on dogs with positive or negative LAT and/or positive or negative IFAT. The frequency of positive node cultures (70%) as versus positive LAT came between the results obtained for an IFAT > 1/40 (64%) and IFAT > 1/80 (73%). 32/33 (97%) dogs had positive node culture, LAT and IFIAT(> 1/80). 6 dogs had negative LAT but positive node culture: 5 of these had also an IFAT < 1/160. This test was used in the field on several eco-epidemiological surveys in leishmanian enzootic areas. Node cultures were made on the dogs with positive TL. 39 strains were isolated: 18 in Algeria, 15 in Morocco, 2 in Syria and 4 in Yemen. 13/39 strains were obtained from dogs with IFI < 1/160: 2 at 1/20, 8 at 1/40 and 3 at 1/80. In Algeria this test was also used for the diagnosis of human visceral leishmaniasis in a child. This quick, simple, sensitive and specific test could be usefully carried out on "field" surveys for the diagnosis of visceral-leishmaniasis in animals and human beings.

[Description of Aedes (Ochlerotatus) coluzzii n. sp. (Diptera, Culicidae), twin A species of the detritus complex]

Reports of a wide variation in space and time of the frequency of autogeny in Aedes (Ochlerotatus) detritus (Haliday, 1833) of the Camargue (Delta of the Rhône, Bouches-du-Rhône, Gard, France) led us to make an enzymatic analysis of male and female adults from different larval biotopes. The study showed the existence of two genetically distinct, sympatric populations which are morphologically indistinguishable. By diagnostic enzymes monomorph Got-2, Gpd, the grouping of the individual into two subgroups satisfies a Hardy-Weinberg equilibrium for the polymorphic enzymes. It is concluded that Ae. detritus is composed of a complex of two sibling species provisionally designated by the letters A (Got-2RR, GpdCC) and B (Got-2LL, GpdBB). In the present article, we retrace the history of the binomen Ae. detritus since the original description (sub nom. Culex detritus) to the split into the detritus complex. Certain ecophysiological (steno-eurygamy) and chorological (bioclimatic gradients N-S) criteria show that the sibling species B should be assigned to the taxon described in UK (Holywood, County Down, Ireland) by A.H. Haliday. Species A is here named Aedes (Ochlerotatus) Coluzzii n. sp.

Leishmania infantum and L. major in Algeria

Since 1980, the development of leishmaniasis in Algeria has been marked by a considerable increase in the number of cases of both visceral leishmaniasis (1121 cases recorded) and cutaneous leishmaniasis (more than 2000 cases per year). New Leishmania infantum and L. major foci have appeared in the north and south of the country. During this period, 100 strains of Leishmania isolated from humans, other mammals and sandflies have been identified. The presence of L. major MON-25 in Psammomys obesus and Phlebotomus papatasi had identified these species as the main reservoir and vector, respectively, of zoonotic cutaneous leishmaniasis. Similarly, the presence of L. infantum MON-1 in Ph. perniciosus and dogs has implicated them as the vector and reservoir of visceral leishmaniasis. The isolation of the dermotropic zymodeme MON-24 of L. infantum from Ph. perfiliewi suggested that it was one of the main vectors of cutaneous leishmaniasis in the north of the country; the reservoir has not been identified. In addition, other zymodemes of Leishmania have been identified in visceral leishmaniasis patients, frequently associated with human immunodeficiency virus (MON-24, MON-33, MON-34 and MON-78), in patients with cutaneous leishmaniasis (MON-80), and in dogs with leishmaniasis (MON-34 and MON-77).

Visceral leishmaniasis in HIV-infected patients in the south of France

Between 1989 and 1993, investigations by classical parasitological procedures of 139 HIV-infected adults living in visceral leishmaniasis (VL) endemic areas showed that 10 of them (7.2%) were positive for Leishmania (by stained smears and culture). In the same period we identified 15 VL cases in patients not infected with HIV. Thus, 40% (10/25) of our VL cases were associated with HIV infection.

The use of isoelectric focusing on polyacrylamide gel for the enzymatic analysis of 'Old World' Leishmania species

Using isoelectric focusing (IEF), a high resolution electrophoresis technique, we analysed 6 enzymes of 24 cloned strains representing all major taxa of 'Old World' Leishmania. The comparison of enzymatic patterns obtained with IEF and starch gel electrophoresis showed that IEF is a more discriminatory and more informative technique for the enzymatic analysis of Leishmania strains; it can detect very slight differences between 2 electromorphs not revealed with starch gel electrophoresis. Moreover, IEF detected several multi-banded patterns which appeared as single bands with starch gel electrophoresis. These multi-banded patterns could not be the result of strain heterogeneity since all the strains had been cloned. Their significance in the biology of Leishmania is discussed.

[New localities for Phlebotomus mariae Rioux, Croset, Léger et Bailly-Choumara, 1974, in Morocco]

Phlebotomus mariae was first described in the South of Morocco in 1974. More specimens were found again recently in the High Atlas, showing that this species can be considered as a valid one, placed in the sub-genus Larroussius. The female remains to be found.

Resistance monitoring in Culex pipiens (Diptera: Culicidae) from central-eastern France

Insensitive acetylcholinesterase (AceR) and five over-produced esterases (A1, A2 and B2, and A4 and B4) involved in detoxification are responsible for resistance to organophosphorous insecticides (OPs) in Culex pipiens L. from the Rhône-Alpes region, where C. pipiens control is mainly accomplished with the OPs temephos and chlorpyrifos using 0.15 mg/liter doses. The strong linkage disequilibria observed between esterases A1 and Est-20(0.64), esterases A4 and B4, and esterases A2 and B2 indicate that these genes were introduced in the Rhône-Alpes region. AceR and esterase A1, which appeared in the south of France 3 yr before the start of mosquito control in Rhône-Alpes, had the highest frequencies. All resistant genotypes were shown to be killed by 0.15 mg/liter temephos in natural breeding sites, but not by 0.15 mg/liter chlorpyrifos. These results are discussed in relation with mosquito control strategies.

Evidence for a long-term increase in the incidence of Leishmania tropica in Aleppo, Syria

We report the results of a short study of the epidemiology of Leishmania tropica in the Sheikh Maksoud District of Aleppo, Syria. The present and past status of infection in a community of about 100,000 people are assessed from prevalence and incidence data obtained by active and passive case detection, and from a skin test survey. L. tropica has apparently been endemic for at least 2-3 human generations in Aleppo, and incidence has increased over the past decade. The current estimated force of infection is 0.174/year, the incidence is about 5%, and the average age of infection is 14 years. L. tropica has the essential characteristics of a cyclic infectious disease, and the recent rise in incidence could be part of a long period cycle. A survey of leishmanial scars seriously underestimated the fraction of persons immune, as scar surveys usually do. We estimate that a passive case registration scheme, which has been established in response to growing concern about leishmaniasis in Aleppo, succeeds in recording and treating about one in 4 cases.

Ecoepidemiology of leishmaniases in Syria. 3. Leishmania major infection in Psammomys obesus provides clues to life history of the rodent and possible control measures

Collections of Psammomys obesus from near Damascus, Syria in May 1990 and November 1991 contained animals of all ages. Both series had a high prevalence of Leishmania major infection. Lesions were small in November and large in May. Assuming the two collections were representative of typical years, it is inferred that the breeding season is between October and May: there is high winter mortality of animals born early in the breeding season, but high survival of their parents, and there is high mortality in summer of animals aged between 17 and around 20 months. Transmission in summer is, therefore, between old adults shortly before their death and young adults born in late winter or spring. Juvenile animals are not exposed to the infection. If these findings are confirmed it should be relatively easy to break this tenuous cycle.

[Isolation of Leishmania major in Phlebotomus papatasi in Biskra (Algeria). The end of an ecoepidemiological saga]

Out of 1,167 females of sandflies dissected, one specimen of Phlebotomus papatasi captured at a transmission site near Biskra, a well known Algerian focus of zoonotic cutaneous leishmaniasis, was found naturally infected with Leishmania major zymodeme MON-25. This supports classical observations of Sergent and al. P. papatasi as vector in this focus in 1921.

Long-range restriction maps of size-variable homologous chromosomes in Leishmania infantum

In order to clarify the interpretation of molecular karyotype polymorphisms in Leishmania, the three smallest chromosomes from five cloned strains of Leishmania infantum were identified by chromosome-specific anonymous DNA probes. The presence in the same clone of homologous chromosomes of a different size was demonstrated. The chromosome size polymorphism appeared even more dramatic, with size variations affecting up to 20% of the chromosome, and the two smallest bands in one strain being equivalent to six bands in another strain. Long-range restriction maps of five different-sized homologues of chromosome I showed the size-variation to be located to a terminal fragment in 4 out of 5 cases, and to a central fragment in one. The size-variable sequence was present on at least three other chromosomes as determined by hybridisation analysis. This suggests an instability of the subtelomeric regions such as that in Plasmodium falciparum. Lastly, the finding of several pairs of distinct-sized homologous chromosomes, together with other studies, strongly suggest that Leishmania is diploid in at least part of its chromosomal complement.

[Ecoepidemiology of leishmaniases in Syria. 2--Presence, in dogs, of Leishmania infantum Nicolle and Leishmania tropica (Wright) (Kinetoplastida-Trypanonomatidae)]

In an ecoepidemiological study in the Syrian foci of human visceral (VL) and cutaneous (CL) leishmaniasis, domestic dogs infected with Leishmania infantum MON-1 and L. tropica MON-76 were found for the first time. In Syria canine leishmaniasis caused by L. infantum, occurs in the humid and sub-humid western belt from the coastal zone to the nearby mountain ranges. Sporadis cases of human VL occur in this area. Canine CL, caused by L. tropica was found in the semi-arid zone in a village with a high human infection rate. The infection causes small papules or crusted ulcers on the nose or muzzle. These observations are relevant to control. In human VL foci it is recommended not to control the dog population, unless this is linked with other activities, such as rabies control. Control of dogs in the CL areas is not justified because of the small size of the lesions and the rarity of the parasites. Indeed the role of the dog as the "true" reservoir host is questionable. Human CL infection is best controlled by active case detection and specific treatment.

[Leishmania tropica in Morocco. IV--Intrafocal enzyme diversity]

Ecoepidemiological analysis of a Moroccan focus of leishmaniasis caused by Leishmania tropica revealed considerable enzymatic diversity. Seven zymodemes belonging to the complex were identified in 149 strains isolated from humans, dogs, and the vector Phlebotomus sergenti. Three distinct subgroups were identifiable, two of which were in turn, composed of three "small variant" zymodemes. The diversity appears to be related to the age of the focus, which may have allowed colonization by zymodemes of different geographic origins. Diversification into "small variants" is apparently the result of recent mutation, possibly associated with genetic exchange.

[Leishmania tropica in Morocco. III--The vector of Phlebotomus sergenti. Apropos of 89 isolates]

In a Moroccan focus of cutaneous leishmaniasis caused by Leishmania tropica, 7,907 female sandflies captured with CDC traps were dissected from summer to autumn 1989. Among species of the genus Phlebotomus, only P. sergenti harbored promastigotes. Eighty-nine strains belonging to the complex L. tropica were isolated. The frequency of vector infection was zero in June, rose to 1.3% in August, and reached 9.9% in October, which indicates that the period of high risk is at the end of the hot season. Out of 89 strains isolated, 74 were completely typed and corresponded to the following four zymodemes: MON-102 (one strain), MON-107 (56 strains), MON-122 (two strains), and MON-123 (15 strains). Only the first two were observed in humans. The distribution of zymodemes MON-102 and MON-107 was very different in humans, dogs, and the vector. In one of the sites surveyed, which was strongly dominated by MON-107, the absence of human cases involving this zymodeme suggests the existence of a wild reservoir.

Interclonal variations in molecular karyotype in Leishmania infantum imply a 'mosaic' strain structure

The molecular karyotypes of 36 clones derived from 8 strains of Leishmania infantum were examined by pulsed-field gel electrophoresis. Although there appeared to be a high degree of genetic relatedness between the clones and the parent strain, a limited degree of polymorphism was noted in 50% of the clones, expressed mainly as the presence of an additional chromosome or as a chromosome size modification. Repeated subcloning in one strain showed that chromosomal rearrangements could occur during the cloning process. Chromosome homologies were examined by Southern analysis with chromosome-specific DNA probes. The results suggest a disomy for some chromosomes, but cannot exclude aneuploidy. The mechanisms possibly leading to such heterogeneity are discussed: they could involve frequent DNA amplification/deletion, and imply a 'mosaic' structure of the cultured strains or clones, with different individuals possessing differently sized versions of the same chromosomes.

[Ecoepidemiology of leishmaniasis in Syria. 1. Leishmania major Yakimoff and Schokhor (Kinetoplastida-Trypanosomatidae) infestation of Psammomys obesus Cretzschmar (Rodentia-Gerbillidae)]

During an epidemiological survey of zoonotic cutaneous leishmaniasis in South-West Syria, Leishmania major zymodème MON-26 was isolated from a reservoir host, Psammomys obesus terraesanctae (Rodentia-Gerbillidae). The abundance of this rodent, its close contact with infected villages and the high prevalence of the infection (63,1%) indicate that this is the main reservoir host of oriental sore in the semi desert area of this country.

Taxonomy of Leishmania. Use of isoenzymes. Suggestions for a new classification

The authors propose a new classification for the genus Leishmania Ross, 1903 based both on the use of intrinsic and extrinsic characters and on Linnean and Adansonian methods. The type of vertebrate host makes it possible to recognize the genus group: Leishmania designates Kinetoplastida parasites of mammals. Neighbouring forms which parasite reptiles are now grouped in the genus Sauroleishmania Ranque, 1973. Characteristics of the intravectorial cycle (supra- and peri-pyloric) are used to define the subgenus group (Leishmania, Viannia Lainson and Shaw, 1987). The classification uses biochemical, particularly enzymatic, characters. Elementary taxonomic units are made up of all the strains having the same isoenzyme profile, i.e. the zymodeme. The grouping of the zymodemes is usually performed through automatic techniques which lead to bush-like trees (dendrograms) showing either simple affinities between units (phenograms) or their phyletic relationships (cladograms). The branches recognized as being stable are individualized as "zymodeme complexes". They bear the name of either the previously defined species taxa or that of a specially created one. Two examples of taxonomic constructions, phenetic and cladistic, are presented. Finally, a general classification of the genus is proposed.

Chromosome size and number polymorphisms in Leishmania infantum suggest amplification/deletion and possible genetic exchange

We have studied the molecular karyotypes of 21 strains and 14 clones of Leishmania infantum using pulsed field gel electrophoresis (PFGE). We detected a high degree of polymorphism within this species, with 'strain-specific' patterns for most isolates, even within a restricted endemic area. Variations relate to both the size of chromosomes (270-2600 kb) and their number, which can vary from 24 to 31 between closely related isolates. This polymorphism does not correlate with isoenzyme analysis. Small size variations between homologous chromosomes of different strains are suggestive of DNA amplification/deletion events. Strains are also shown to be multiclonal, with slight differences between most clones, but with a predominant clone concealing the others in PFGE analysis. The analysis of these data leads to the hypothesis of occasional genetic exchange by nuclear fusion in Leishmania, as recently shown in the related protozoan Trypanosoma brucei.

[Simultaneous presence in dogs of 2 zymodemes of the Leishmania infantum complex]

The concomitant presence of two zymodemes of the leishmania infantum complex. MON-1 and MON-77, is reported in a dog with diffuse leishmaniasis. The zymodemes were present in both the skin and lymph nodes. Possible explanations for the presence of the two zymodemes are discussed.

[Presence in Morocco of Phlebotomus (Paraphlebotomus) kazeruni Theodor and Mesghali, 1964]

A report is made of Phlebotomus kazeruni on southern Marocco (Tata and Ouarzazate Provinces). This sandflies was previously known only from Afghanistan, Iran and Saudi Arabia.

[Isolation of Leishmania major Yakimoff and Shokhor, 1914 (Kinetoplastida-Trypanosomatidae) in Meriones shawi-shawi (Duvernoy, 1842) (Rodentia-Gerbillidae) in Tunisia]

Leishmania major, agent of zoonotic cutaneous leishmaniasis, has been isolated from the rodent Meriones shawi shawi in central Tunisia. As a result, the North saharan arid mediterranean area can be considered as epidemiologically homogeneous.

The identity of Leishmania tarentolae Wenyon 1921

A double clone of Trypanosoma platydactyli Catouillard, 1909, derived from a single trypomastigote from the blood of the Moorish gecko, Tarentola mauritanica, was grown in vitro. Morphogenesis of the parasites led to a stable population of promastigotes which were identical, in general morphology, ultrastructure and the electrophoretic mobility of 8 enzymes, to those cultures previously considered to be Leishmania tarentolae Wenyon, 1921. These cultures included the strain isolated from the type locality in Algeria by Parrot (1949) and later used as a laboratory model for the genus Leishmania. T. platydactyli and L. tarentolae are synonymized and the present status of saurian Leishmania parasites is discussed.

[Presence of Leishmania major Yakimoff and Schokhor, 1914 in Mali. Enzymatic identification of a strain of human origin]

The first case of oriental sore reported to Leishmania major is identified in Mali. The characterization of the stain isolated from a left arm lesion of a 30 years old european woman is carried out by electrophoretic analysis using enzymes, i.e. PGM, PGI, G-6-PDH, 6-PGDH, IDH, MDH, ME, GOT.

Zoonotic cutaneous leishmaniasis in Saudi Arabia: the incrimination of Phlebotomus papatasi as the vector in the Al-Hassa oasis

Surveys of the phlebotomine fauna in a focus of zoonotic cutaneous leishmaniasis (ZCL) in the Al-Hassa oasis, Eastern Province, Saudi Arabia, revealed only one species of Phlebotomus (P. papatasi) and three of Sergentomyia (S. antennata, S. clydei and S. fallax). 11 specimens of P. papatasi from six sites in the oasis were found with promastigotes in the midgut. An isolate from one of the sandflies was typed by the examination of isoenzymes and identified as Leishmania major, zymodeme LON-4 (= Montpellier zymodeme 26), the principal zymodeme of L. major isolated from patients with ZCL in the oasis. Three isolates from leishmanial lesions at sites of the bites of wild caught specimens of P. papatasi were also identified as the same zymodeme of L. major as the isolate from the sandfly. The findings show that P. papatasi is the vector of ZCL in the Al-Hassa oasis and probably in other ecologically similar foci in the Kingdom.

[Ecology of leishmaniasis in the south of France. 21. Influence of temperature on the development of Leishmania infantum Nicolle, 1908 in Phlebotomus ariasi Tonnoir, 1921. Experimental study]

The influence of temperature on the life-cycle of Leishmania infantum Nicolle, 1908 (isolated from a dog in the Cévennes) in a known vector (Phlebotomus ariasi Tonnoir, 1921) was studied with special reference to the proportion of flies infected and the intensity and localization of parasites in the sandfly. Wild female sandflies were caught at night by active searches and were put with a heavily infected dog in a mosquito net on the night of capture. On the following morning, engorged females were tubed individually and were then maintained at 10, 15, 20, or 25 degrees C (+/- 1.5 degrees). The temperatures were chosen after preliminary experiments which showed that temperatures of 30 degrees C or less than 5 degrees C were lethal to both the sandfly and, usually, the parasite. Midguts of the flies were dissected and examined 6 to 10 days after the infective feed. Although there were no obvious differences in the proportions of infected sandflies at different temperatures, a statistical analysis of the finding (chi 2 test) showed that raising the temperature: significantly increased the overall proportion of infected sandflies; speeded up the multiplication of promastigotes in the midgut; controlled the movement of parasites forwards into the thoracic midgut (from 15 degrees C); encouraged the attachment of the flagellates to the wall of the stomodaeal valve (from 20 degrees C). The use of an exponential model to deduce the size of the parasite population at the different temperatures led to the conclusion that the optimum temperature for L. infantum is in the region of 25 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Zoonotic cutaneous leishmaniasis in Saudi Arabia: lesions healing naturally in man followed by a second infection with the same zymodeme of Leishmania major

A patient with a previous history of an infection with Leishmania b. braziliensis contracted zoonotic cutaneous leishmaniasis (ZCL) in the Al-Hassa oasis, Eastern Province, Saudi Arabia. Five lesions healed spontaneously over a period of 40 weeks without treatment. A year after acquiring ZCL he became infected again in the same focus. Isolates of parasites at both episodes were identified as L. major, zymodeme LON-4. Compared with the first infection of ZCL, parasites were fewer in the lesions on the second occasion, the lesions were smaller and healing was quicker (10 weeks). This work and a previous report of patients with active lesions and leishmanial scars suggest that second infections of L. major are not uncommon in the oasis where no autochthonous infections of other species of Leishmania have yet been recorded in man and only one species of Phlebotomus (P. papatasi) is known.

[A new enzymatic variant of Leishmania infantum Nicolle, 1908, agent of cutaneous leishmaniasis in northern Algeria]

For the first time, the pathogenic agent of cutaneous leishmaniasis in the North of Algeria has been identified as Leishmania infantum s.1. The parasite was found to be a newly discovered enzymatic variant (zymodeme 24) differing by two electromorphs from a variant isolated in France (zymodeme 11) from the same type of lesion. Until now, the dermotropic zymodemes of Algeria and France have not been seen in cases of visceral leishmaniasis of the Mediterranean Basin.