Leishmaniasis and malaria: new tools for epidemiologic analysis

Parasites and priorities: the early evolution of 'neglected disease' initiatives and the history of a global health agenda

This article explores the development and evolution of 'neglected tropical diseases' (NTDs) as an operative and imaginative category in global public health, focusing on the early intellectual and institutional development of the category in the 1970s. It examines early work around 'neglected' diseases in the Rockefeller Foundation's Health Sciences Division, specifically the Foundation's 'Great Neglected Diseases of Mankind' initiative that ran between 1978 and 1988, as well as intersections with the WHO's parallel Special Programme for Research and Training in Tropical Diseases and efforts by the US-based Edna McConnell Clark and MacArthur Foundations. A key concern of advocates who influenced initial programmes focused around 'neglect' was a lack of sophistication in medical parasitological research globally. Central to the NTDs' capacity to animate diverse energies were claims about parasitic diseases and their place in new biotechnological approaches to medicine. This article explores how the emphasis on 'neglected', 'tropical' or even 'endemic' diseases encoded specific concerns and desires of parasitologists in the early 1970s. Despite the desire to prioritise the needs of 'endemic' countries and the recognition of a widening cohort of experts from both high-income and low-income nations, NTD advocates often recapitulated historic power dynamics privileging research institutions in the USA and Europe. Historicising and contextualising 'neglect' illuminates the contingent and changing politics of global health in a formative period in the late twentieth century.

Cutaneous and Mucocutaneous Leishmaniasis

Leishmaniasis is a chronic disease caused by flagellate protozoa of the genus Leishmania. It is a global disease, but most cases are seen in South America, the Mediterranean, and some areas of Asia and Africa. The 3 main types of leishmaniasis are cutaneous (the most common), mucocutaneous, and visceral (the most severe). Visceral leishmaniasis is also known as kala-azar. Leishmaniasis is diagnosed by demonstrating the presence of Leishmania amastigotes in clinical specimens using direct microscopic examination or molecular analysis. Various treatments exist, although the evidence supporting the options available for cutaneous leishmaniasis is weak. Both the classical presentation of leishmaniasis and our management of the disease have changed in recent decades because of acquired immune deficiency caused by conditions such as human immunodeficiency infection or the use of tumor necrosis factor inhibitors.

Cutaneous and Mucocutaneous Leishmaniasis

Leishmaniasis is a chronic disease caused by flagellate protozoa of the genus Leishmania. It is a global disease, but most cases are seen in South America, the Mediterranean, and some areas of Asia and Africa. The 3 main types of leishmaniasis are cutaneous (the most common), mucocutaneous, and visceral (the most severe). Visceral leishmaniasis is also known as kala-azar. Leishmaniasis is diagnosed by demonstrating the presence of Leishmania amastigotes in clinical specimens using direct microscopic examination or molecular analysis. Various treatments exist, although the evidence supporting the options available for cutaneous leishmaniasis is weak. Both the classical presentation of leishmaniasis and our management of the disease have changed in recent decades because of acquired immune deficiency caused by conditions such as HIV infection or the use of TNF inhibitors.

Utility of the microculture method for Leishmania detection in non-invasive samples obtained from a blood bank

In recent years, the role of donor blood has taken an important place in epidemiology of Leishmaniasis. According to the WHO, the numbers of patients considered as symptomatic are only 5-20% of individuals with asymptomatic leishmaniasis. In this study for detection of Leishmania infection in donor blood samples, 343 samples from the Capa Red Crescent Blood Center were obtained and primarily analyzed by microscopic and serological methods. Subsequently, the traditional culture (NNN), Immuno-chromatographic test (ICT) and Polymerase Chain Reaction (PCR) methods were applied to 21 samples which of them were found positive with at least one method. Buffy coat (BC) samples from 343 blood donors were analyzed: 15 (4.3%) were positive by a microculture method (MCM); and 4 (1.1%) by smear. The sera of these 343 samples included 9 (2.6%) determined positive by ELISA and 7 (2%) positive by IFAT. Thus, 21 of (6.1%) the 343 subjects studied by smear, MCM, IFAT and ELISA techniques were identified as positive for leishmaniasis at least one of the techniques and the sensitivity assessed. According to our data, the sensitivity of the methods are identified as MCM (71%), smear (19%), IFAT (33%), ELISA (42%), NNN (4%), PCR (14%) and ICT (4%). Thus, with this study for the first time, the sensitivity of a MCM was examined in blood donors by comparing MCM with the methods used in the diagnosis of leishmaniasis. As a result, MCM was found the most sensitive method for detection of Leishmania parasites in samples obtained from a blood bank. In addition, the presence of Leishmania parasites was detected in donor bloods in Istanbul, a non-endemic region of Turkey, and these results is a vital importance for the health of blood recipients.

Skin infections in developing countries

PURPOSE OF REVIEW

In developing countries, where the majority of people have a low income and live in resource-poor settings, skin infections are prevalent. Data from recent studies provide insight into the most common skin infections and their management.

RECENT FINDINGS

Several studies confirm that skin infections account for the majority of pediatric mortality and morbidity in developing countries. They are prevalent in resource-poor settings and rural areas in certain parts of the world. Also, hot, humid climates and overcrowding predispose to skin infections. Most of the skin infections are curable with effective medication.

SUMMARY

Skin infections are of particular importance in developing countries. This review focuses on the most common skin infections and summarizes the most recent knowledge on the epidemiology, morbidity, and treatment in resource-poor settings.

Tropical dermatology: Tropical diseases caused by protozoa

Protozoan infections are very common among tropical countries and have an important impact on public health. Leishmaniasis is the most widely disseminated protozoan infection in the world, while the trypanosomiases are widespread in both Africa and South America. Amebiasis, a less common protozoal infection, is a cause of significant morbidity in some regions. Toxoplasmosis and pneumocystosis (formerly thought to be caused by a protozoan) are worldwide parasitic infections with a very high incidence in immunocompromised patients but are not restricted to them. In the past, most protozoan infections were restricted to specific geographic areas and natural reservoirs. There are cases in which people from other regions may have come in contact with these pathogens. A common situation involves an accidental contamination of a traveler, tourist, soldier, or worker that has contact with a reservoir that contains the infection. Protozoan infections can be transmitted by arthropods, such as sandflies in the case of leishmaniasis or bugs in the case of trypanosomiases. Vertebrates also serve as vectors as in the case of toxoplasmosis and its transmission by domestic cats. The recognition of the clinical symptoms and the dermatologic findings of these diseases, and a knowledge of the geographic distribution of the pathogen, can be critical in making the diagnosis of a protozoan infection.

LEARNING OBJECTIVES

After completing this learning activity, participants should be able to recognize the significance of protozoan infections worldwide, identify the dermatologic manifestations of protozoan infections, and select the best treatment for the patient with a protozoan infection.

Detection of new endemic areas of cutaneous leishmaniasis in Pakistan: a 6-year study

BACKGROUND

Cutaneous leishmaniasis (CL) is endemic in Pakistan and is widely spreading. Recently, an outbreak of the disease was observed in the region. We report some new endemic areas of CL in the country.

METHODS

A total of 1210 cases of CL who visited our department from 1996 to 2001 are reported. Among them, 760 were residents of the Jacobabad, Larkana, and Dadu districts of Sindh province and had never previously traveled to endemic areas. These districts have never been reported/recognized as endemic for CL. Others were residents of endemic areas of Balochistan province. Diagnosis was made on clinical presentation; a giemsa-stained smear test and histopathological results. All the cases were treated with the meglumine antimoniate 600 mg/day (adults) and 15 mg/kg/day (children) intramuscularly for 20 consecutive days.

RESULTS

All the patients were aged between 2.5 months and 65 years. Three hundred and ninety-two patients were females and 368 were males. Duration of the disease ranged from 2 to 18 months. Most of the patients had a single lesion on the face and/or extremities. Clinically, the disease was classified as: dry papular type, 407 cases; dry ulcerative type, 335 cases; and wet ulcerative type, 18 cases. No cases of muco-cutaneous or visceral leishmaniasis were found during this period. Smear testing was positive in 845 cases, while 365 cases were histopathologically positive. An ultrastructural study was performed using specimens of a few of the cases. Leishmania parasites were detected in the dermal tissues as well as in the macrophages.

CONCLUSIONS

We propose that the Jacobabad, Larkana and Dadu districts could be considered endemic for CL. Wet- and dry-type lesions indicate the presence of both Leishmania tropica and L. major in this tropical region.

Current status of artemisinin and its derivatives as antimalarial drugs

Artemisinin is a promising and a potent antimalarial drug, which meets the dual challenge posed by drug-resistant parasites and rapid progression of malarial illness. This review article focuses on the progress achieved during the last years in the production of artemisinin from Artemisia annua. The structure, biosynthesis and analysis of artemisinin and its mode of action are described. The review also focuses on clinical studies, toxicity studies, pharmacokinetics and activity of artemisinin related compounds. The production strategies including organic synthesis, extraction from plants, in vitro cultures and alternative strategies for enhancing the yields are also discussed.

A nosocomial outbreak of malaria associated with contaminated catheters and contrast medium of a computed tomographic scanner

OBJECTIVE

To identify the risk factors associated with an unexpected outbreak of malaria that occurred among seven patients in a general teaching hospital in Taipei in October 1995.

DESIGN

A three-stage case-control study was conducted to identify risk factors.

PATIENTS

We identified all 7 patients who were diagnosed as malaria cases and 69 controls from those undergoing computed tomography (CT) examination.

METHODS

Malaria was diagnosed by demonstrating the presence of Plasmodium falciparum on either thick or thin blood smears. Clinical characteristics and exposure information were collected from medical records and patient interviews.

RESULTS

The index case was infected by malaria when he visited Nigeria in early September and was diagnosed when he was hospitalized in hospital A in October. Among 10 patients examined with the Imatron scanner after the index case, all 6 who were injected with contrast medium were infected, but none of 4 examined without contrast medium were infected (P=.005).

CONCLUSIONS

This nosocomial outbreak of malaria was most likely due to transmission via a contaminated catheter and contrast medium used for CT scanning. Use of disposable catheters may avoid such nosocomial outbreaks in the future.

Molecular genetic approaches to parasite identification: their value in diagnostic parasitology and systematics

A wide range of approaches is available to parasitologists to aid in specific parasite identification and to formulate phylogenetic relationships. This review emphasises the usefulness of molecular genetic techniques, especially DNA-based procedures, in addressing problems of identification, characterisation and phylogeny of parasites. It should be stressed that an understanding of the various DNA approaches, techniques and target genes most likely to be effective in addressing key issues in diagnostic parasitology and systematics is still developing. Nevertheless, DNA methods clearly have great potential with regard to specificity and sensitivity, and applications will increase further with technological advance. Indeed, because of the minimal requirements for material, PCR-based methods especially should prove of immense value in future studies with parasites.

An oligonucleotide probe derived from kDNA minirepeats is specific for Leishmania (Viannia)

Sequence analysis of Leishmania (Viannia) kDNA minicircles and analysis of multiple sequence alignments of the conserved region (minirepeats) of five distinct minicircles from L. (V.) braziliensis species with corresponding sequences derived from other dermotropic leishmanias indicated the presence of a sub-genus specific sequence. An oligonucleotide bearing this sequence was designed and used as a molecular probe, being able to recognize solely the sub-genus Viannia species in hybridization experiments. A dendrogram reflecting the homologies among the minirepeat sequences was constructed. Sequence clustering was obtained corresponding to the traditional classification based on similarity of biochemical, biological and parasitological characteristics of these Leishmania species, distinguishing the Old World dermotropic leishmanias, the New World dermotropic leishmanias of the sub-genus Leishmania and of the sub-genus Viannia.

Genetic and aging epidemiology. The merging of two disciplines

For future research in aging epidemiology to be meaningful, it will have to integrate knowledge and skills from multiple areas, including the application of genetic and molecular epidemiologic techniques to the study of the elderly. This article begins with an overview of genetic and molecular epidemiology, followed by a discussion of several unique methodologic issues that need to be considered in the interpretation of genetic and molecular findings of epidemiologic studies of the elderly.

Leishmaniases of the New World: current concepts and implications for future research

Recent epidemiologic studies indicate that leishmaniasis in the Americas is far more abundant and of greater public health importance than was previously recognized. The disease in the New World is caused by a number of different parasite species that are capable of producing a wide variety of clinical manifestations. The outcome of leishmanial infection in humans is largely dependent on the immune responsiveness of the host and the virulence of the infecting parasite strain. This article reviews current concepts of the clinical forms, immunology, pathology, laboratory diagnosis, and treatment of the disease as well as aspects of its epidemiology and control. Recommendations for future research on the disease and its control are made.

Diagnosis of New World leishmaniasis: Specific detection of species of the Leishmania braziliensis complex by amplification of kinetoplast DNA

We have sequenced single kinetoplast DNA minicircles from three species and part of a minicircle from the fourth major species within the Leishmania braziliensis complex. Alignment of these sequences with each other and with those of other kinetoplastids allowed the selection of a pair of oligonucleotides suitable as primers in a polymerase chain reaction which is highly specific for the Leishmania braziliensis complex. The reaction is capable of detecting less than one femtogramme of kinetoplast DNA. It has been tested with crude specimens from South American leishmaniasis patients, potential wild animal reservoirs and sandfly vectors. The tests indicate that these primers are suitable for diagnosis of leishmaniasis and potentially useful in epidemiological surveys.

Serodiagnosis of parasitic diseases

In this review on serodiagnosis of parasitic diseases, antibody detection, antigen detection, use of monoclonal antibodies in parasitic serodiagnosis, molecular biological technology, and skin tests are discussed. The focus at the Centers for Disease Control on developing improved antigens, a truly quantitative FAST-enzyme-linked immunosorbent assay, and the very specific immunoblot assays for antibody detection is highlighted. The last two assays are suitable for field studies. Identification of patient response in terms of immunoglobulin class or immunoglobulin G subclass isotypes or both is discussed. Immunoglobulin isotypes may asist in defining the stage of some diseases. In other instances, use of a particular anti-isotype conjugate may increase the specificity of the assay. Monoclonal antibodies have played important roles in antigen purification and identification, in competitive antibody assays with increased sensitivity and specificity, and in assays for antigen detection in serum, body fluids, or excreta. Molecular biological technology has allowed significant advances in the production of defined parasitic serodiagnostic antigens.

Leishmaniasis in a domestic goat in Kenya

The pathological and electron-microscopic features of the first case of autochthonous leishmaniasis affecting a domestic goat in Kenya are described. They are similar to what have been described in man and other animals. Using a short amino-acid sequence common to all the species of leishmania as primers for kDNA synthesis, the intervening sequence of 120 bases was amplified in the goat's tissues by polymerase chain reaction (PCR). The leishmania kinetoplast DNA sequence was detected in all the different infected tissues of the goat examined. The sensitivity and specificity of this assay are discussed. The result of the assay used was consistent with the parasite being either L. major or L. aethiopica as the infecting agent. The isoenzyme studies were consistent with L. aethiopica as the strain responsible for this goat's infection. The control of leishmaniasis and its vector must take into account the potential role of animal reservoirs in the environment. Even though Kenya and other East African countries are endemic for kala-azar, the presence of kala-azar in goats is of considerable veterinary public health importance in Africa. Efforts must not be spared to identify and detect other possible animal reservoirs in the subregion. Using DNA amplification techniques, which are sensitive and specific, such as the one described in this paper, sera and other biological fluids and tissues from different animal species should be utilized for detecting additional reservoirs for leishmania parasites particularly in known endemic areas of the world.

The molecular epidemiology of parasites

The explosion of new techniques, made available by the rapid advance in molecular biology, has provided a battery of novel approaches and technology which can be applied to more practical issues such as the epidemiology of parasites. In this review, we discuss the ways in which this new field of molecular epidemiology has contributed to and corroborated our existing knowledge of parasite epidemiology. Similar epidemiological questions can be asked about many different types of parasites and, using detailed examples such as the African trypanosomes and the Leishmania parasites, we discuss the techniques and the methodologies that have been or could be employed to solve many of these epidemiological problems.

DNA probe detection of periodontal pathogens in HIV-associated periodontal lesions

Recent studies have shown that an atypical gingivitis and a rapidly progressive periodontal disease may be early-occurring opportunistic infections associated with human immunodeficiency virus (HIV) infection. This study examined the prevalence of selected periodontal pathogens associated with these HIV-related periodontal lesions. Subgingival plaque samples were obtained from both HIV-seronegative and HIV-seropositive homosexual men and from presumably uninfected heterosexual men. DNA probes were used to detect Actinobacillus actinomycetemcomitans, Bacteroides intermedius, Bacteroides gingivalis, Eikenella corrodens and Wolinella recta in the plaque. The healthy sites in both the seronegative and seropositive homosexual groups showed a greater prevalence of all test bacteria, except for E. corrodens, than did the heterosexual group. HIV-associated periodontitis sites showed a microbial profile qualitatively similar to that of conventional periodontitis, except that B. gingivalis was more prevalent in conventional periodontitis. In contrast, HIV-associated gingivitis sites exhibited a greater prevalence of all bacteria tested than conventional gingivitis sites. In fact, HIV gingivitis generally showed a bacterial profile similar to that of the HIV periodontitis lesions, except that W. recta was significantly more prevalent in HIV periodontitis. These data suggest that the HIV gingivitis lesion is a precursor to HIV periodontitis. Thus, early identification and prophylactic treatment of high-risk individuals may prevent the destruction of periodontal tissues.

Generation of species-specific DNA probes for Leishmania aethiopica

We report here the cloning of kinetoplast DNA (kDNA) sequences from Leishmania aethiopica in order to develop a specific and sensitive method for the identification of the parasite. Analysis of the cloned kDNA sequences showed different taxonomic specificities demonstrating sequence diversity within the kinetoplast DNA. Cloned whole minicircle hybridized with all Old World Leishmania species tested. Some cloned fragments of minicircle kDNA hybridized with Leishmania species causing cutaneous leishmaniasis in the Old World, but not with the viscerotropic species. Two L. aethiopica-specific clones were found. These clones hybridized with all L. aethiopica isolates tested, but did not react with other Leishmania species. The nucleotide sequence of the L. aethiopica-specific R3 clone is presented. Clones hybridizing with only some of the L. aethiopica isolates were also identified, although none of them showed specificity only for isolates causing localized (LCL) or diffuse (DCL) form of cutaneous leishmaniasis in Ethiopia.

Nucleic acid techniques and the detection of parasitic diseases

The detection of infectious disease-causing organisms is important for the initiation of effective treatment, in monitoring response to therapy and in epidemiological studies of disease of human or animal hosts. In this article Stuart Wilson primarily considers parasitic diseases, but much can be applied to infectious diseases in general.

Nucleic acid probes as potential tools in oral microbial epidemiology

The present review deals with genetic tools in the microbial diagnostic laboratory, types of nucleic acid probes, their construction and cloning, hybridization reactions, their sensitivity and specificity, and their advantages and limitations. The nucleic acid probes seem to possess a number of advantages over traditional diagnostic methods. DNA, RNA, and oligonucleotide probes are expected to have increased impact on our understanding of the pathogenesis and the treatment of infectious inflammatory periodontal diseases. In addition, these probes have potential application in epidemiological studies of oral microorganisms. However, the limitations of the probes must be kept in mind, and newly developed probes must be controlled with respect to the critical issues of sensitivity and specificity.

Plasmodium falciparum: DNA probe diagnosis of malaria in Kenya

We previously reported isolation of DNA probe which specifically recognizes Plasmodium falciparum and developed a simple method for its use. The sensitivity and specificity of this DNA probe method have now been extensively field tested in comparison with those of conventional microscopic examination of blood films in two separate studies in Malindi, Kenya, involving a total of 1179 patients. In the second study, which used improved techniques, sensitivity of the DNA probe was 89% when compared to microscopy. We conclude that the DNA probe method compares favorably with conventional microscopy in detecting parasite densities as low as 25 parasites per microliter of blood. A significant advantage of the DNA probe method is that it utilizes a standardized procedure which can simultaneously and reproducibly analyze a large number of samples without opportunity for significant reader bias.

Genomic DNA differences between pathogenic and nonpathogenic Entamoeba histolytica

cDNA libraries were constructed from pathogenic (HM-1:IMSS) and nonpathogenic (SAW 1734) isolates of Entamoeba histolytica. A cDNA clone (cEH-P1) specific for pathogenic amoebae was identified by screening with a pool of sera from patients with invasive amoebiasis that had been absorbed with nonpathogenic amoebae. This clone was used for the identification of a homologous clone (cEH-NP1) in the cDNA from nonpathogenic amoebae. Sequence analysis and comparison of the predicted amino acid sequences for both clones disclosed 12% evolutionary divergence in structure. Hybridization of both cDNA probes to genomic DNA from four pathogenic and five nonpathogenic E. histolytica isolates revealed two distinct Southern blot patterns, one characteristic for pathogenic amoebae and the other for nonpathogenic amoebae. Further, the complex pattern of restriction fragments hybridizing to an actin cDNA probe was also different between pathogenic and nonpathogenic isolates but was conserved within each group of amoebae. The results indicate that pathogenic isolates of E. histolytica are genetically distinct from nonpathogenic isolates.

DNA probes specific for Entamoeba histolytica possessing pathogenic and nonpathogenic zymodemes

A number of DNA probes which hybridize to highly abundant DNA sequences of Entamoeba histolytica were developed. Variations in the hybridization patterns of different E. histolytica strains were detected with selected probes. Four types of restriction fragment length patterns were obtained. Of these, the first class belonged to E. invadens and E. histolytica-like var. Laredo. The next two classes consisted of various strains of E. histolytica which were originally isolated from symptomatic patients and possessed pathogenic patterns of isoenzymes (zymodemes), whereas the fourth group contained E. histolytica strains with nonpathogenic zymodemes obtained from asymptomatic carriers. DNA probes, based on DNA sequences specific to E. histolytica isolates with pathogenic and nonpathogenic zymodemes were isolated, and their nucleotide sequences were determined. These probes (P145 and B133) hybridized selectively to DNA of isolates possessing either pathogenic or nonpathogenic isoenzyme patterns. The newly developed probes could be useful for diagnostic purposes and could serve as tools to investigate the molecular basis of pathogenicity and the genetic mechanisms which regulate the variable aggressive behavior of the parasite.

Detection and quantitation of Anaplasma marginale in carrier cattle by using a nucleic acid probe

Cattle which have recovered from acute infection with Anaplasma marginale, a rickettsial hemoparasite of cattle, frequently remain persistently infected with a low-level parasitemia and serve as reservoirs for disease transmission. To fully understand the role of these carriers in disease prevalence and transmission, it is essential that low levels of parasitemia can be accurately detected and quantitated. We have developed a nucleic acid probe, derived from a portion of a gene encoding a 105,000-molecular-weight surface protein, that can detect A. marginale-infected erythrocytes. The probe is specific for A. marginale and can detect 0.01 ng of genomic DNA and 500 to 1,000 infected erythrocytes in 0.5 ml of blood, which is equivalent to a parasitemia of 0.000025%. This makes the probe at least 4,000 times more sensitive than light microscopy. Hybridization of the probe with treated blood from animals proven to be carriers of anaplasmosis showed that parasitemia levels were highly variable among carriers, ranging from greater than 0.0025 to less than 0.000025%. Parasitemia levels of individual animals on different dates were also variable. These results imply that, at any given time, individuals within a group of cattle may differ significantly in their abilities to transmit disease.

Molecular approaches to DNA diagnosis

The DNA of a parasite is the ultimate blueprint of that parasite, the one characteristic which normally remains unchanged during every stage of the life-cycle. All the DNA sequence in the egg of a species of parasite are also in the larvae and adults of the same species. The same DNA is present in the parasite whether it is in a free-living stage, in an invertebrate vector or in a vertebrate host such as man. The molecular basis for DNA diagnosis is to allow labelled single-stranded species or strain-specific DNA sequences, selected from well-characterized reference species, to find and hybridize with homologous DNA from, or in, the unknown isolates of parasites. DNA probes are now available for most vector borne parasitic diseases. Parasitological identification problems are mostly concerned with distinguishing closely related strains or subspecies, for example detecting Taenia solium eggs as opposed to T. saginata eggs, or finding which of the 15 man-infecting subspecies of Leishmania is present in a single cutaneous lesion, the commonest clinical sign of the disease, or in a sandfly. For efficient hybridization by the present methods there has to be enough of a particular sequence present in a parasite's genome to make a feasible target. Therefore, DNA probes for parasites have been selected from repetitive, reiterated or multicopy DNA with intrinsic extensive sequence variation. DNA, which is free of coding restraint, can evolve rapidly to give differences between species, so that introns, ribosome gene spacers, variant genes, pseudo-genes and non-conserved DNA have all been used for DNA diagnosis. The major problems of sequence selection have been greatly aided by the use of recombinant DNA methods, which have the added advantage of economical production of DNA probes. The unique characteristics of kinetoplast mini-circle DNA in Leishmania has allowed the selection of a complex species, subspecies, strain and even isolate-specific DNA probes. These have been used successfully for Southern filter endonuclease fragment DNA identification, for dot-blot recognition of less than 200 parasites and non-radioactive detection of DNA sequence homology by 'in situ' hybridization and light microscopy in a single Leishmania cell.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of cultural methods and DNA probe analyses for the detection of Actinobacillus actinomycetemcomitans, Bacteroides gingivalis, and Bacteroides intermedius in subgingival plaque samples

The purpose of this study was to compare DNA probe analyses to cultural methods for detecting three periodontal pathogens, Actinobacillus actinomycetemcomitans, Bacteroides gingivalis, and Bacteroides intermedius, in human subgingival plaque. Subgingival sites from patients diagnosed as either healthy or showing evidence of gingivitis or juvenile or adult periodontitis were sampled using two paper points. The number of these pathogens from one paper point was determined using microbiologic media and speciated by biochemical tests. Results were then compared to bacterial numbers obtained from the other paper point using species-specific DNA probes. In 60 samples from the disease group, DNA probe analysis demonstrated 100% effectiveness in detecting A. actinomycetemcomitans and B. intermedius and 91% effectiveness in detecting B. gingivalis at culture positive levels (greater than or equal to 10(3) cells). In addition, probe assays frequently identified these pathogens in samples that were culture negative. Probe analysis revealed a better correlation between presence of a pathogen and clinical evidence of disease on an individual patient basis. In contrast, most samples taken from sites of healthy individuals showed undetectable levels of all three pathogens as determined by both techniques. These results suggest that DNA probe technology is at least equivalent and often superior to cultural methods for detecting A. actinomycetemcomitans, B. gingivalis, and B. intermedius in human subgingival plaque samples.

Rectal leishmaniasis in a patient with acquired immunodeficiency syndrome

A severe rectal lesion due to Leishmania infection is described in an American-born homosexual man with the acquired immunodeficiency syndrome. The infection, which may have been venereally transmitted, responded to treatment with amphotericin B. There was no evidence of visceral leishmaniasis. The contribution of the patient's immunodeficiency to the development of the atypical cutaneous leishmanial lesion is unclear. The case may foretell increasing problems with protozoan infections in AIDS as the epidemic spreads to areas with endemic protozoan diseases.

Rapid detection of Leishmania amastigotes in fluid aspirates and biopsies of human tissues

When using a genus-specific monoclonal antibody (83-J3D2) as the primary reagent in an indirect immunofluorescent antibody assay (IFA), intracellular amastigotes of Leishmania were easily identified in 9 of 9 biopsies and in 11 of 12 needle aspirates taken from human lesions. In contrast, only 5 of the biopsies and 4 of the aspirates yielded promastigotes upon culture in vitro. Similarly, all but 2 of the aspirates and one-half of the biopsies were reported as negative for parasites when stained with Wright's and hematoxylin-eosin, respectively. Serum antibody titers, ranging from 1:8 to 1:128, corroborated the results of the amastigote detection assays when histopathology and isolation were negative. These findings support the practicality of using the genus-specific monoclonal IFA in those field situations where it becomes necessary to differentiate leishmaniasis from other skin infections.

Disease diagnosis by recombinant DNA methods

Recombinant DNA procedures have now been applied to the problem of the identification of molecular defects in man that account for heritable diseases, somatic mutations associated with neoplasia, and acquired infectious disease. Thus recombinant DNA technology has rapidly expanded our ability to diagnose disease. Substantial advances in the simplification of procedures for diagnostic purposes have been made, and the informed physician has gained in diagnostic accuracy as a consequence of these developments. The wide application of recombinant DNA diagnostics will depend on simplicity, speed of results, and cost containment.

Kinetoplast DNA minicircles: regions of extensive sequence divergence

Previous work has shown that the kinetoplast minicircle DNA of Leishmania species exhibits species-specific sequence divergence and this observation has led to the development of a DNA probe-based diagnostic test for leishmaniasis. In the work reported here, we demonstrate that the minicircle is composed of three types of DNA sequences with differing specificities reflecting different rates of DNA sequence change. A library of cloned fragments of kinetoplast DNA (kDNA) from Leishmania mexicana amazonensis was prepared and the cloned subfragments were found to contain DNA sequences with different taxonomic specificities based on hybridization analysis with various species of Leishmania. Four groups of subfragments were found, those that hybridized with a large number of Leishmania sp. as well as sequences unique to the species, subspecies, or isolate. Analysis of nested deletions of a single, full-length minicircle demonstrates that these different taxonomic specificities are contained within a single minicircle. This implies that different regions of a single minicircle have DNA sequences that diverge at different rates. These sequences represent potentially valuable tools in diagnostic, epidemiologic, and ecological studies of leishmaniasis and provide the basis for a model of kDNA sequence evolution.