Enzyme electrophoresis in characterizing the causative organism of Gambian trypanosomiasis

[Molecular typing of Leishmania (Leishmania) amazonensis and species of the subgenus Viannia associated with cutaneous and mucosal leishmaniasis in Colombia: A concordance study]

INTRODUCTION

Multilocus enzyme electrophoresis (MLEE) is the reference standard for the characterization of Leishmania species. The test is restricted to specialized laboratories due to its technical complexity, cost, and time required to obtain results. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) is used to identify Leishmania species.

OBJECTIVE

To establish the concordance between the two tests as identifying methods for circulating species in Colombia.

MATERIALS AND METHODS

A total of 96 isolates from patients with cutaneous or mucosal leishmaniasis were selected and identified by MLEE and PCR-RFLP with miniexon and hsp70 as the molecular targets, which were used sequentially. Restriction enzymes HaeIII and BccI were similarly applied. Cohen's kappa coefficient and the 95% confidence interval (CI) were calculated.

RESULTS

The kappa coefficient and the 95% CI between MLEE and PCR-RFLP displayed "very good" concordance with a coefficient of 0.98 (CI95%: 0.98 to 1.00). The identified species were Leishmania Viannia braziliensis, Leishmania Viannia panamensis, Leishmania Viannia guyanensis and Leishmania Leishmania amazonensis. A total of 80 of the 96 isolates were sequenced and the results obtained by PCR-RFLP were confirmed.

CONCLUSION

Due to the concordance obtained between tests results with the amplification of the genes miniexon and hsp70, PCR-RFLP is proposed as an alternative for identifying circulating Leishmania species in Colombia.

Barcoding in trypanosomes

Trypanosomes (genus Trypanosoma) are parasites of humans, and wild and domestic mammals, in which they cause several economically and socially important diseases, including sleeping sickness in Africa and Chagas disease in the Americas. Despite the development of numerous molecular diagnostics and increasing awareness of the importance of these neglected parasites, there is currently no universal genetic barcoding marker available for trypanosomes. In this review we provide an overview of the methods used for trypanosome detection and identification, discuss the potential application of different barcoding techniques and examine the requirements of the 'ideal' trypanosome genetic barcode. In addition, we explore potential alternative genetic markers for barcoding Trypanosoma species, including an analysis of phylogenetically informative nucleotide changes along the length of the 18S rRNA gene.

Molecular and biological characterization of Trypanosoma cruzi strains isolated from children from Jequitinhonha Valley, State of Minas Gerais, Brazil

INTRODUCTION

The biological diversity of Trypanosoma cruzi strains plays an important role in the clinical and epidemiological features of Chagas disease.

METHODS

Eight T. cruzi strains isolated from children living in a Chagas disease vector-controlled area of Jequitinhonha Valley, State of Minas Gerais, Brazil, were genetically and biologically characterized.

RESULTS

The characterizations demonstrated that all of the strains belonged to T. cruzi II, and showed high infectivity and a variable mean maximum peak of parasitemia. Six strains displayed low parasitemia, and two displayed moderate parasitemia. Later peaks of parasitemia and a predominance of intermediate and large trypomastigotes in all T. cruzi strains were observed. The mean pre-patent period was relatively short (4.2 ± 0.25 to 13.7 ± 3.08 days), whereas the patent period ranged from 3.3 ± 1.08 to 34.5 ± 3.52 days. Mortality was observed only in animals infected with strain 806 (62.5%). Histopathological analysis of the heart showed that strains 501 and 806 caused inflammation, but fibrosis was observed only in animals infected with strain 806.

CONCLUSIONS

The results indicate the presence of an association between the biological behavior in mice and the genetic characteristics of the parasites. The study also confirmed general data from Brazil where T. cruzi II lineage is the most prevalent in the domiciliary cycle and generally has low virulence, with some strains capable of inducing inflammatory processes and fibrosis.

Human and animal Trypanosomes in Côte d'Ivoire form a single breeding population

BACKGROUND

Trypanosoma brucei is the causative agent of African Sleeping Sickness in humans and contributes to the related veterinary disease, Nagana. T. brucei is segregated into three subspecies based on host specificity, geography and pathology. T. b. brucei is limited to animals (excluding some primates) throughout sub-Saharan Africa and is non-infective to humans due to trypanolytic factors found in human serum. T. b. gambiense and T. b. rhodesiense are human infective sub-species. T. b. gambiense is the more prevalent human, causing over 97% of human cases. Study of T. b. gambiense is complicated in that there are two distinct groups delineated by genetics and phenotype. The relationships between the two groups and local T. b. brucei are unclear and may have a bearing on the evolution of the human infectivity traits.

METHODOLOGY/PRINCIPAL FINDINGS

A collection of sympatric T. brucei isolates from Côte d'Ivoire, consisting of T. b. brucei and both groups of T. b. gambiense have previously been categorized by isoenzymes, RFLPs and Blood Incubation Infectivity Tests. These samples were further characterized using the group 1 specific marker, TgSGP, and seven microsatellites. The relationships between the T. b. brucei and T. b. gambiense isolates were determined using principal components analysis, neighbor-joining phylogenetics, STRUCTURE, FST, Hardy-Weinberg equilibrium and linkage disequilibrium.

CONCLUSIONS/SIGNIFICANCE

Group 1 T. b. gambiense form a clonal genetic group, distinct from group 2 and T. b. brucei, whereas group 2 T. b. gambiense are genetically indistinguishable from local T. b. brucei. There is strong evidence for mating within and between group 2 T. b. gambiense and T. b. brucei. We found no evidence to support the hypothesis that group 2 T. b. gambiense are hybrids of group 1 and T. b. brucei, suggesting that human infectivity has evolved independently in groups 1 and 2 T. b. gambiense.

Differences between Trypanosoma brucei gambiense groups 1 and 2 in their resistance to killing by trypanolytic factor 1

BACKGROUND

The three sub-species of Trypanosoma brucei are important pathogens of sub-Saharan Africa. T. b. brucei is unable to infect humans due to sensitivity to trypanosome lytic factors (TLF) 1 and 2 found in human serum. T. b. rhodesiense and T. b. gambiense are able to resist lysis by TLF. There are two distinct sub-groups of T. b. gambiense that differ genetically and by human serum resistance phenotypes. Group 1 T. b. gambiense have an invariant phenotype whereas group 2 show variable resistance. Previous data indicated that group 1 T. b. gambiense are resistant to TLF-1 due in-part to reduced uptake of TLF-1 mediated by reduced expression of the TLF-1 receptor (the haptoglobin-hemoglobin receptor (HpHbR)) gene. Here we investigate if this is also true in group 2 parasites.

METHODOLOGY

Isogenic resistant and sensitive group 2 T. b. gambiense were derived and compared to other T. brucei parasites. Both resistant and sensitive lines express the HpHbR gene at similar levels and internalized fluorescently labeled TLF-1 similar fashion to T. b. brucei. Both resistant and sensitive group 2, as well as group 1 T. b. gambiense, internalize recombinant APOL1, but only sensitive group 2 parasites are lysed.

CONCLUSIONS

Our data indicate that, despite group 1 T. b. gambiense avoiding TLF-1, it is resistant to the main lytic component, APOL1. Similarly group 2 T. b. gambiense is innately resistant to APOL1, which could be based on the same mechanism. However, group 2 T. b. gambiense variably displays this phenotype and expression does not appear to correlate with a change in expression site or expression of HpHbR. Thus there are differences in the mechanism of human serum resistance between T. b. gambiense groups 1 and 2.

Infestation by triatomine bugs in indigenous communities of Valledupar, Colombia

OBJECTIVE

To calculate triatomine infestation indices in indigenous communities in Colombia.

METHODS

A descriptive study was carried out in 19 communities in Valledupar Municipality, Cesar Department, Colombia. During June to December, 2007, triatromine bugs were collected from their resting places in households. Taxonomic identification was made according to the keys by Lent & Wygodzinsky. An infection process in animal model and isozyme analysis of triatomine feces were performed.

RESULTS

Rhodnius prolixus showed a density index of 154.7%, for Triatoma dimidiata was 102.45%, T. maculata 109.25% and Panstrogylus geniculatus 0.3%. The mean infestation index was 40.54%, and mean Trypanosoma infection index was 9.4%. Of five hemocultures positive for T. cruzi, three were enzimatically identified as T. cruzi group I. Biopsies revealed few pathologic characteristics of infective process with these strains isolated from domiciliary triatomine bugs.

CONCLUSIONS

The high triatomine infestation indices in households and the T. cruzi infection index are evidence of active transmission of Chagas disease. The situation merits a vector control program and serological survey of the population at risk. The genetic characterization of T. cruzi strains as group I agrees with other findings on strains in this region of Colombia.

Trypanosoma brucei s.l.: Microsatellite markers revealed high level of multiple genotypes in the mid-guts of wild tsetse flies of the Fontem sleeping sickness focus of Cameroon

To identify Trypanosoma brucei genotypes which are potentially transmitted in a sleeping sickness focus, microsatellite markers were used to characterize T. brucei found in the mid-guts of wild tsetse flies of the Fontem sleeping sickness focus in Cameroon. For this study, two entomological surveys were performed during which 2685 tsetse flies were collected and 1596 (59.2%) were dissected. Microscopic examination revealed 1.19% (19/1596) mid-gut infections with trypanosomes; the PCR method identified 4.7% (75/1596) infections with T. brucei in the mid-guts. Of these 75 trypanosomes identified in the mid-guts, Trypanosoma brucei gambiense represented 0.81% (13/1596) of them, confirming the circulation of human infective parasite in the Fontem focus. Genetic characterization of the 75 T. brucei samples using five microsatellite markers revealed not only multiple T. brucei genotypes (47%), but also single genotypes (53%) in the mid-guts of the wild tsetse flies. These results show that there is a wide range of trypanosome genotypes circulating in the mid-guts of wild tsetse flies from the Fontem sleeping sickness focus. They open new avenues to undertake investigations on the maturation of multiple infections observed in the tsetse fly mid-guts. Such investigations may allow to understand how the multiple infections evolve from the tsetse flies mid-guts to the salivary glands and also to understand the consequence of these evolutions on the dynamic (which genotype is transmitted to mammals) of trypanosomes transmission.

Distribution of Leishmania major zymodemes in relation to populations of Phlebotomus papatasi sand flies

Phlebotomus papatasi (Scopoli) (Diptera: Psychodidae) is the main vector of Leishmania major Yakimoff & Schokhor (Kinetoplastida: Trypanosomatidae), the causative agent of zoonotic cutaneous leishmaniasis in the Old World. Multilocus enzyme electrophoresis (MLEE) was extensively used to type different L. major stocks allover the world. Multilocus microsatellite typing (MLMT) has been recently used to investigate P. papatasi sand flies at population and subpopulation levels. In this article, the association between geographical distribution of L. major zymodemes and the distribution of populations and subpopulations of L. major vector; P. papatasi are discussed.

Conserved sequence of the TgsGP gene in Group 1 Trypanosoma brucei gambiense

The trypanosome responsible for the majority of cases of human trypanosomiasis in Africa is Group 1 Trypanosoma brucei gambiense. Currently the most reliable test for the parasite is based on a single gene, which encodes a 47kDa receptor-like T. b. gambiense-specific glycoprotein, TgsGP, expressed in the flagellar pocket of bloodstream forms. Although TgsGP has been demonstrated in T. b. gambiense throughout its geographic range, similar genes have been demonstrated in other T. brucei sspp. isolates, and there are no data on the extent of sequence variation in TgsGP. Here we have carried out a comparison of TgsGP sequences in a range of Group 1 T. b. gambiense isolates and compared the gene to homologues in other T. brucei sspp. in order to provide information to support the use of this gene as the key identification target for Group 1 T. b. gambiense. We demonstrate that the sequence of TgsGP is well conserved in Group 1 T. b. gambiense across the endemic range of gambian human trypanosomiasis and confirm that this gene is a suitable target for specific detection of this parasite. The TgsGp-like genes in some isolates of T. b. brucei, T. b. rhodesiense and Group 2 T. b. gambiense are closely similar to VSG Tb10.v4.0178, which may be the ancestral gene from which TgsGP was derived.

Host restriction, morphology and isoenzymes among trypanosomes of some British freshwater fishes

Trypanosomes were studied from the blood of 6 species of small British fish caught in the River Lee. Morphologically the trypanosomes from the blood ofNemacheilus barbatulusL.,Phoxinus phoxinusL.,Cottus gobioL.,Gobio gobioL.,Gasterosteus aculeatusandPungitus pungitusL. were indistinguishable. Cross-transmission experiments using syringe passage of culture forms and also the leech vectorHemiclepsis marginatashowed that the trypanosomes were not host specific. The isoenzyme patterns of culture forms fromN. barbatulusandP. phoxinuswere identical for 11 enzymes studied. The trypanosomes from the 6 species of fish previously classified as separate species are, on the basis of these results, regarded as a single species,Trypanosoma cobitis(Mitrophanow, 1883).

Trypanosoma brucei gambiense: study of population genetic structure of Central African stocks using amplified fragment length polymorphism (AFLP)

To understand the maintenance and resurgence of historical Human African Trypanosomiasis (HAT) foci, AFLP was used to genotype 100 Central African Trypanosoma brucei s.l. stocks. This technique confirmed the high genetic stability of T. b. gambiense group 1 stocks and the micro genetic variability within Central African T. b. gambiense stocks. It revealed several T. b. gambiense genotypes and allowed the identification of minor and major genotypes in HAT foci. The coexistence of these genotypes in the same focus suggests that clustering of stocks according to HAT focus does not provide the true genetic picture of trypanosome circulating within the disease focus because the minor genotypes are generally underestimated. The presence of minor and major genotypes in HAT foci may explain the persistence and the resurgence of Central African sleeping sickness foci.

Trypanosoma brucei s.l.: Characterisation of stocks from Central Africa by PCR analysis of mobile genetic elements

To better understand the epidemiology of sleeping sickness in the Central African sub-region, notably the heterogeneity of Human African Trypanosomiasis (HAT) foci, the mobile genetic element PCR (MGE-PCR) technique was used to genotype Trypanosoma brucei s.l. (T. brucei s.l.) isolates from this sub-region. Using a single primer REV B, which detects positional variation of the mobile genetic element RIME, via amplification of flanking regions, MGE-PCR revealed a micro genetic variability between Trypanosoma brucei gambiense (T. b. gambiense) isolates from Central Africa. The technique also revealed the presence of several T. b. gambiense genotypes and allowed the identification of minor and major ubiquitous genotypes in HAT foci. The presence of several T. b. gambiense genotypes in HAT foci may explain the persistence and the resurgence phenomena of the disease and also the epidemic and the endemic status of some Central African sleeping sickness foci. The MGE-PCR technique represents a simple, rapid, and specific method to differentiate Central African T. brucei s.l. isolates.

Will the real Trypanosoma b. gambiense please stand up

Controversy has surrounded the differentiation of Trypanosoma brucei gambiense from T. b. rhodesiense (causative agents of Gambian and Rhodesian sleeping sickness, respectively) almost from the moment they were named. In the light of recent findings from biochemical and immunological characterization studies, Wendy Gibson reviews the status of T. b. gambiense to see if there is now a consensus concerning its identity.

Population genetic structure and cladistic analysis of Trypanosoma brucei isolates

Using a novel multilocus DNA marker analysis method, we studied the population genetic structure of Trypansoma brucei stocks and derived clones isolated from animal and rhodesiense sleeping sickness patients during a national sleeping sickness control program in Mukono district, Uganda. We then performed a cladistic analysis to trace relationships and evolution, using stocks and clones recovered from geographically and temporally matched hosts, including inter-strain comparisons with T. b. gambiense stocks and clones. Our results show that while there was close genetic relatedness among parasite populations from the same geographical region, micro-heterogeneities exist between different stocks. Data are presented that indicate that not every human sleeping sickness focus may be associated with a particular human-infective trypanosome strain responsible for long-term stability of the reference focus. We provide evidence of genetic sub-structuring among type 1 T. b. gambiense stocks, which has potentially important implications for molecular epidemiology of T. brucei.

Species concepts for trypanosomes: from morphological to molecular definitions?

The way species and subspecies names are applied in African trypanosomes of subgenera Trypanozoon and Nannomonas is reviewed in the light of data from molecular taxonomy. In subgenus Trypanozoon the taxonomic importance of pathogenicity, host range and distribution appear to have been inflated relative to actual levels of genetic divergence. The opposite is true for subgenus Nannomonas, where current taxonomic usage badly underrepresents genetic diversity. Data from molecular characterisation studies are revealing a growing number of genotypes, which may represent distinct taxa. Unfortunately few of these genotypes are yet supported by sufficient biological data to be recognized taxonomically. But we may be missing fundamental epidemiological information, because of our inability to distinguish these trypanosomes in host blood morphologically or in tsetse by their developmental cycle. Molecular taxonomy has led the way in identifying these new genotypes and now offers the key to elucidating the biology of these organisms.

Characterization of Trypanosoma brucei s.l. subspecies by isoenzymes in domestic pigs from the Fontem sleeping sickness focus of Cameroon

Though it has been established that domestic animals (especially the pig) are potential reservoir hosts for Trypanosoma brucei gambiense in West Africa, there is little data to this effect concerning Central Africa. Instead, some previous authors report the absence of Trypanozoon type trypanosomes in domestic animals in Cameroon. Thirty-two domestic pigs were sampled by KIVI (kit for in vitro isolation) of trypanosomes in the northern region (Bechati) of the Fontem sleeping sickness focus of Cameroon. Twenty-one of these were found positive, from 15 of which 17 isolates were successfully obtained. Isoenzyme characterization revealed that isolates from 4 of the 15 pigs belonged to zymodemes associated with T. brucei gambiense group 1. The prevalence of this disease in the local human population is, however, very low. It is evident from this study that the domestic pig may be a potential reservoir host for T. brucei gambiense in the Fontem focus. There is, however, need for an extensive study on domestic animals in Cameroon and other neighbouring countries for a better comprehension of the epidemiology of sleeping sickness within the Central African region.

Molecular characterization of field isolates of human pathogenic trypanosomes

The accurate identification of each of the three subspecies of Trypanosoma brucei remains a challenging problem in the epidemiology of sleeping sickness. Advances in molecular characterization have revealed a much greater degree of heterogeneity within the species than previously supposed. Only group 1 T. b. gambiense stands out as a separate entity, defined by several molecular markers. T. b. rhodesiense is generally too similar to sympatric T. b. brucei strains to be distinguished from them by any particular molecular markers. Nevertheless, characterization of trypanosome isolates from humans and other animals has allowed the identification of potential reservoir hosts of T. b. rhodesiense. The recent discovery of a gene for human serum resistance may provide a useful marker for T. b. rhodesiense in the future. There have been few attempts to find associations between genetic markers and other biological characters, except human infectivity. However, virulence or fly transmissibility have been correlated with molecular markers in some instances.

History of sleeping sickness in East Africa

The history of human sleeping sickness in East Africa is characterized by the appearance of disease epidemics interspersed by long periods of endemicity. Despite the presence of the tsetse fly in large areas of East Africa, these epidemics tend to occur multiply in specific regions or foci rather than spreading over vast areas. Many theories have been proposed to explain this phenomenon, but recent molecular approaches and detailed analyses of epidemics have highlighted the stability of human-infective trypanosome strains within these foci. The new molecular data, taken alongside the history and biology of human sleeping sickness, are beginning to highlight the important factors involved in the generation of epidemics. Specific, human-infective trypanosome strains may be associated with each focus, which, in the presence of the right conditions, can be responsible for the generation of an epidemic. Changes in agricultural practice, favoring the presence of tsetse flies, and the important contribution of domestic animals as a reservoir for the parasite are key factors in the maintenance of such epidemics. This review examines the contribution of molecular and genetic data to our understanding of the epidemiology and history of human sleeping sickness in East Africa.

Trypanosoma cruzi genotypes associated with domestic Triatoma sordida in Bolivia

Triatoma sordida is the second species of Triatominae considered of epidemiological significance in Bolivia. Associated with Triatoma infestans in various regions, it is as yet the only triatomine species established in human dwellings in localities of Velasco province, Department of Santa Cruz. This domestication is considered as primary. Flagellate parasites were detected in 16.2% of domiciliary T. sordida and the kDNA-PCR confirmed the presence of Trypanosoma cruzi. Frequencies of T. cruzi clonets 20 and 39, common clonets in Bolivian domestic cycle (T. infestans), were established by their direct detection in feces using PCR and hybridization. These clonets present low frequencies in T. sordida and synanthropic mammals. Forty-six stocks were isolated and analysed by multilocus enzyme electrophoresis (MLEE). The MLEE showed a higher clonal diversity than in T. infestans domestic cycle and the genotypes were clustered in the two principal lineages of T. cruzi. Within each lineage, a broad variability was observed. Mixture of genotypes was mostly observed in mammals. The large diversity of T. cruzi in this cycle should be related to its sylvatic origin. Moreover, the current limited sample of stocks suggests a lineage association with specific hosts.

Wide variation in DNA content among isolates of Trypanosoma brucei ssp

The DNA contents of 18 Trypanosoma brucei ssp. stocks were compared using flow cytometry, karyotype analysis and quantitation of repetitive DNA by Southern blotting and hybridisation. The DNA contents of Type 1 T. b. gambiense stocks were lower than those of non-gambiense stocks, but both groups showed a wide range of variation in DNA content. Amongst T. b. gambiense stocks. Mabia at the lower end of the range had 14% less DNA than Dal 972 at the top of the range. Similarly, amongst non-gambiense stocks. 117R at the lower end of the range had 14% less DNA than LM55 at the top of the range. The T. b. gambiense stock Mabia had 29% less DNA than non-gambiense stock LM55. The DNA content of Type II T. b. gambiense stocks had minichromosomes albeit fewer than non-gambiense stocks. This result was verified by hybridisation with probes for satellite DNA and a telomere-specific repeat. Hybridisation with the probe for the beta-tubulin genes also revealed an apparent reduction of gene copy number T. b. gambiense relative to non-gambiense stocks. In conclusion, there is a wide range of variation in genome size in T. brucei ssp., with T. b. gambiense stocks at the lower end of the range. The reduction in genome size correlates with loss of repeated genes and non-coding sequences in T. b. gambiense stocks, and is not continued to chromosomes of a particular size.

Human cutaneous leishmaniasis caused by Leishmania (Viannia) braziliensis in Santiago del Estero, Argentina: identification of parasites by monoclonal antibodies and isoenzymes

Diagnostic and parasite characterization and identification studies were carried out in human patients with cutaneous leishmaniasis lesions in Santiago del Estero, Northern Province of Argentina. Diagnostic procedures were biopsies of lesions for smears and inoculations in hamster, needle aspirations of material from ulcers for "in vitro" cultures. Immunodiagnostic techniques applied were IFAT-IgG and Montenegro skin test. Primary isolation of eight stocks of leishmanial parasites was achieved from patients with active lesions. All stocks were biologically characterized by their behaviour in hamster, measurements of amastigote and promastigotes and growth "in vitro". Eight stocks were characterized and identified at species level by their reactivity to a cross-panel of sub-genus and species-specific Monoclonal Antibodies through an Indirect Immunofluorescence technique and a Dot-ELISA. We conclude from the serodeme analysis of Argentina stocks that: stocks MHOM/AR/92/SE-1; SE-2; SE-4; SE-8; SE-8-I; SE-30; SE-34 and SE-36 are Leishmania (Viannia) braziliensis. Three Leishmania stocks (SE-1; SE-2 and SE-30) did not react with one highly species-specific Monoclonal Antibody (Clone: B-18, Leishmania-(Viannia) braziliensis marker) disclosing two serodeme group patterns. Five out of eight soluble extracts of leishmanial promastigotes were electrophoresed on thin-layer starch gels and examined for the enzyme MPI, Mannose Phosphate Isomerase; MDH, Malate Dehydrogenase; 6PGD, 6 Phosphogluconate Dehydrogenase; NH, Nucleoside Hydrolase, 2-deoxyinosine as substrate; SOD, Superoxide Dismutase; GPI, Glucose Phosphate Isomerase and ES, Esterase. From the isoenzyme studies we concluded that stocks: MHOM/AR/92/SE-1; SE-2; SE-4; SE-8 and SE-8-I are isoenzymatically Leishmania (Viannia) braziliensis. We need to analyze more enzymes before assigning them to a braziliensis zymodeme.

Characterization of Trypanosoma brucei gambiense isolates using restriction fragment length polymorphisms in 5 variant surface glycoprotein genes

Fifty-eight Type I Trypanosoma brucei gambiense (G) stocks, including 16 from 3 sleeping sickness foci in Cameroon, were compared by Restriction Fragment Length Polymorphism (RFLP) analysis with 14 T.b. brucei and T.b. rhodesiense stocks from various endemic areas of Africa. Loci examined were for 5 variant surface glycoprotein (VSG) genes: the LiTat 1.3, AnTat 11.17 and 2K genes were present as single copy genes, while the VSG 117 and U2 gene probes hybridised with a family of related genes. The RFLP data were subjected to cluster analysis to produce a dendrogram constructed from similarity coefficients. The LiTat 1.3 and AnTat 11.17 genes are considered to be characteristic of G stocks, and neither gene was found in the non-G stocks; however, the LiTat 1.3 gene was absent from 6 of the 58 G stocks, while the AnTat 11.17 gene was absent from 8. Supplementation of the LiTat 1.3 antigen in the Card Agglutination Test for Trypanosomiasis with the AnTat 11.17 antigen might thus improve performance of the test, particularly in Cameroon. The U2 VSG gene probe gave a characteristic RFLP pattern for G stocks, as did the VSG 117 gene; the latter is an isogene of AnTat 1.8 previously used extensively to characterise G stocks by other workers. The 2K gene was absent in some G stocks, while present in some non-G stocks, and was not therefore useful for characterisation of G stocks. In cluster analysis, the T.b. gambiense stocks formed a large homogeneous group, subdivided into 5 subgroups, with the non-gambiense stocks as a heterogeneous outgroup.

Differentiation between human and animal strains of Cryptosporidium parvum using isoenzyme typing

Isoenzyme typing was used to study a number of oocyst isolates of Cryptosporidium parvum from different geographical locations and of human or animal origin. All isolates showed identical enzyme motility when glucose phosphate isomerase (GPI; 23 isolates tested) or lactate dehydrogenases (LDH; 20 isolates tested) was assayed. However, two isoenzyme forms were observed with phosphoglucomutase (PGM; 9 animal isolates showed one form, while 8/9 human isolates showed a second form) and hexokinase (HK; 4 human isolates showed one form and 6 animal isolates showed a second form). Thus, PGM and HK each exhibit 2 isoenzymes corresponding to 2 parasite populations associated with separate hosts. The data from this study, plus supportive evidence obtained by different methods and by independent researchers, lend support to the hypothesis that separate cycles of transmission of C. parvum may exist within human and animal hosts.

Leishmania infantum in the Himalayas

Visceral leishmaniasis (VL) was first reported in Pakistan over 30 years ago from the remote north-eastern Himalayan region. Sporadic cases are now widely reported from the Northern Areas, part of North-West Frontier Province (NWFP) and Punjab Province, together with Azad Jammu and Kashmir (AJK). Two hundred and thirty-nine cases, mostly young children, have been reported in the last decade; 52% were under 2 years old, and 86% were aged less than 5 years; the male:female ratio was 3:1. In a cross sectional study of the population in 14 endemic villages, 1938 individuals of all ages were randomly skin-tested with leishmanin and 27.4% gave a positive result. The leishmanin response rate increased with age. In some areas, almost 70% of the adults over 40 years old were positive. Leishmanin positivity appeared to cluster among households (P = 0.0003), but clinical cases among households did not (P = 0.472). The leishmanin response pattern in the foci of Chilas and AJK reflected an endemic pattern of disease, whereas that seen in the Baltistan foci suggested interrupted transmission. Human sera collected in endemic villages were tested for anti-Leishmania antibodies, 580 by enzyme-linked immunosorbent assay and direct agglutination test (DAT), and another 1403, as blood samples on filter paper, were tested by DAT alone. Isolations of Leishmania were made from 15 patients, 11 from bone marrow, 3 from normal skin and one from spleen. The parasites were typed as Leishmania infantum zymodeme LON-49 (= MON-1).

Biochemical behavior of Trypanosoma cruzi strains isolated from mice submitted to specific chemotherapy

To investigate the influence of chemotherapy on the biochemical behavior of Trypanosoma cruzi strains, three groups of mice were infected with one of three strains of T. cruzi of different biological and isoenzymic patterns (Peruvian, 21SF and Colombian strains). Each group was subdivided into subgroups: 1-treated with nifurtimox; 2-treated with benznidazole and 3-untreated infected controls. At the end of treatment, that lasted for 90 days, xenodiagnosis, subinocculation of blood into new born mice and hemoculture were performed as tests of cure. From the positive tests, 22 samples of T. cruzi were isolated from all subgroups. Electrophoretic analysis of the isoenzymes PGM, GP1, ALAT and ASAT failed to show any difference between parasite strains isolated from treated and untreated mice, which indicates that no detectable clonal selection or parasite genetic markers alterations concerning the isoenzymes analysed have been determined by treatment with drugs of recognized antiparasitic effect, suggesting stability of the phenotypic characteristics of the three biological types of T. cruzi strains.

Molecular variation in trypanosomes

Several species of the genus Trypanosoma cause parasitic diseases of considerable medical and veterinary importance throughout Africa, Asia and the Americas. These parasites exhibit considerable intra-species genetic diversity and variation, which has complicated their taxonomic classification. This diversity and variation can be defined at the level of both the genome and of individual genes. The nuclear genome shows considerable inter- and intra-species plasticity in terms of chromosome number and size (molecular karyotype). The mitochondrial (kDNA) genome also varies considerably between species, especially in terms of minicircle size and organization. There is also considerable intra-specific sequence diversity in minicircles and within the Variable Region of the maxicircle. Restriction enzyme analysis of this diversity has lead to the concept of 'schizodemes'. At the gene level, isoenzyme analysis has proven very useful for strain and isolate identification, with the classification into numerous 'zymodemes'. Considerable antigenic diversity has also been identified in T. cruzi and T. brucei, with the development of 'serodemes' in the latter. In addition to this inter-strain diversity, African trypanosomes (T. brucei, T. congolense, and T. vivax) exhibit the phenomenon of antigenic variation, where individual parasites are able to express any one of hundreds of different copies of the Variant Surface Glycoprotein gene at any particular time. The molecular mechanisms underlying antigenic variation are now understood in considerable detail. The implication of this molecular diversity and variation are discussed in terms of trypanosome taxonomy and disease control.

Population genetics of Trypanosoma brucei in central Africa: taxonomic and epidemiological significance

In order to estimate the value of population genetics for both the taxonomy of trypanosomes belonging to the species Trypanosoma brucei and a better understanding of Human African Trypanosomiasis (HAT), we undertook a cellulose acetate electrophoresis isoenzyme study involving 55 stocks isolated from man and animals in Congo, Zaire and Cameroun. Out of the 24 loci surveyed, 15 exhibited variability, which made it possible to delimit 23 zymodemes, divided into 2 groups. The first group equated to the classical subspecies Trypanosoma brucei gambiense, while the second corresponded to the classical subspecies Trypanosoma brucei brucei. These results broadly agree with the current taxonomy, and are corroborated by RFLP analysis of kDNA. Statistical analysis indicates a basically clonal reproduction system of the trypanosomes in the area studied; the zymodemes are equivalent to natural clones (or a family of closely related clones), stable in space and time. Epidemiological hypotheses are proposed according to the geographic distribution of the clones in this area.

Isoenzyme variation within the genus Cryptosporidium

Soluble extracts of the oocysts of Cryptosporidium parvum had demonstrable, but low, activities of malate dehydrogenase (MDH, EC. 1.1.1.37), carboxylesterase (ES, EC 3.1.1.1) and lactate dehydrogenase (LDH, EC. 1.1.1.27) following thin-layer starch-gel electrophoresis. Much higher activities of glucose phosphate isomerase (GPI, EC. 5.3.1.9) and phosphoglucomutase (PGM, EC. 2.7.5.1) were found, and zymograms of these two enzymes were used to characterise isolates of C. parvum from human, bovine, ovine and cervine sources, C. muris from the brown rat and C. baileyi from young turkeys. PGM and GPI zymograms clearly distinguished between C. parvum, C. muris and C. baileyi. The five isolates of C. parvum showed the same electrophoretic mobility for GPI, whereas the PGM mobility of the single human isolate of C. parvum examined was clearly different from that of the other isolates. This is the first report of the use of isoenzymes to distinguish between species and isolates of Cryptosporidium.

Numerical taxonomy of Trypanozoon based on polymorphisms in a reduced range of enzymes

Numerical analyses of Trypanozoon taxonomy are presented, based on the isoenzyme data of Stevens et al. (1992). The previous study used a reduced range of enzymes compared with earlier work; the analyses indicate the value of this rationalized system. Both recently isolated trypanosome stocks and previously studied populations were included, allowing detailed comparison with earlier studies. Relationships between zymodemes were calculated with an improved similarity coefficient program, using Jaccard's coefficient (1908), and by Nei's method (1972). Dendrograms were constructed from the matrices produced with the group-average method. The groupings produced by both numerical methods were in close agreement, and the clusters of related principal zymodemes largely matched the species, subspecies and strain groups proposed by previous workers. Trypanozoon biochemical taxonomy is reviewed and the groupings reinforced by this study are: the mainly East African strain groups, busoga, zambezi, kakumbi, kiboko and sindo; T.b. gambiense and the bouaflé strain group from West Africa, and T. evansi; an intermediate bouaflé/busoga group was also recognized.

A simplified method for identifying subspecies and strain groups in Trypanozoon by isoenzymes

To characterize trypanosomes from the subgenus Trypanozoon, 272 stocks in 111 zymodemes were analysed by the polymorphisms seen in a rationalized range of nine enzymes, resolved by electrophoresis, mostly on cellulose acetate. Several highly polymorphic or invariant enzymes used previously were omitted, while two new enzymes, NHD and SOD were included; the isoenzymes seen for SOD were interpreted as two separate enzymes, SODA and SODB. Isoenzyme band patterns were analysed by two complementary numerical methods to elucide taxonomic relationships within the subgenus; groups of zymodemes corresponding to subspecies and strain groups were defined, which agreed closely with previous studies. Except for one zymodeme, Trypanosoma evansi could not be clearly distinguished from the bouaflé strain group. This strain group had enzymic features that overlapped to some extent those of the busoga group. Trypanosoma brucei gambiense and the zambezi, kakumbi, kiboko and sindo groups were clearly defined. Eight zymodemes could not be classified. A rapid identification system using a limited number of enzymes is presented.

Studies on the leishmaniases in the Sudan. 2. Clinical and parasitological studies on cutaneous leishmaniasis

In the Omdurman Hospital for Tropical Diseases, Sudan, from 6 October to 1 December 1986, 736 patients with cutaneous leishmaniasis (CL) were studied. The duration of the lesions varied from a few days to 4 months, usually (56%) 1-3 months. Multiple lesions ranging from one to 50 (mean = 4) were present in 80% of cases. Ulcerative lesions were found in 44%, nodulo-ulcerative in 31%, nodular in 31% and others, including infiltrated, fungating and warty lesions, in 5% of patients. The lower limbs were involved in 66%, upper limbs in 50%, face in 6%, back in 4%, chest in 2%, abdomen in 1% and buttocks in 0.1%. Lesions were also found on the ear, scalp, genitalia and mucocutaneous junctions. Lymphatic involvement was present in 11% of the patients, secondary infection in 18%, fever in 17%, pain in 38% and itching in 61%; 3% of the patients were diabetics. Features of diffuse cutaneous leishmaniasis were noted in one patient and three cases presented with an 'id' reaction. A slit-skin smear was positive in 88% of the cases. Using thin-layer starch gel electrophoresis, 23 stocks from man and one from Arvicanthis niloticus were identified by the characterization of 12 enzymes as Leishmania major zymodeme LON-1. Various therapeutic regimens are discussed. Only patients with severe lesions (approximately 15%) were given 3 to 4 weeks' treatment with intravenous Pentostam, to which all except 2 responded satisfactorily with minimal side effects.

Elusive trypanosomes

Professor Kershaw's encouragement of the development of anion-exchange separation of African trypanosomes from blood led to two decades of activity when, for the first time, considerable progress was made in the intrinsic characterization of these parasites. Such characterization depended on establishing high infections in laboratory rodents. However, the collection of samples from the field was restricted by the failure of certain trypanosomes either to infect, or to multiply adequately in, rodents. More recently, in vitro culture has come to play an increasingly important role in producing material. By obtaining procyclic forms directly from wild tsetse flies, or by transforming low numbers of bloodstream forms in field samples to the procyclic phase in experimental tsetse, trypanosomes of poor or nil infectivity to rodents were readily cultured in the large amounts required for biochemical characterization. A number of specimens of a new kind of Nannomonas, of Trypanosoma simiae, of T. grayi, and of an antigenically distinct T. brucei gambiense were found. Evidence is presented that many other kinds of trypanosome may be eluding isolation by their inability to infect rodents.

Recurrent lesions in human Leishmania braziliensis infection--reactivation or reinfection?

Strains of Leishmania braziliensis subspecies isolated from initial and recurrent lesions in 24 patients from the Pacific coast of Colombia were examined for distinguishing polymorphisms by enzyme electrophoresis, restriction endonuclease analysis of kDNA, and molecular karyotyping of nuclear DNA. Recurrent strains from 12 patients (50%) were identical to the initially infecting strain by all methods of characterisation. Phenotypic and genotypic identity, together with clinical data, support endogenous reactivation as the mechanisms of recurrent disease in these 12 patients. 5 of the 24 (22%) recurrent strains differed from the initial strain by all methods. The remaining 7 strain pairs, not separated by enzyme polymorphisms, showed differing schizodeme and/or karyotype profiles. Patients whose recurrent lesions were caused by strains different from those causing the initial lesions had a significantly longer disease-free interval than patients whose lesions were caused by identical strains. Recurrent lesions occurred further from initial lesions in the former than in the latter group. Exogenous reinfection is the most plausible explanation for recurrences due to disparate organisms. These findings have important implications for both treatment evaluation and vaccination strategies for American tegumentary leishmaniasis.

The substitution of procyclic for bloodstream form Trypanosoma brucei gambiense in isoenzyme studies

Examination of 10 enzymes from 8 stocks of Trypanosoma brucei showed that procyclic forms could be substituted for bloodstream forms in isoenzyme studies. T. b. gambiense procyclic forms cultured in vitro offer a better source of material for genetic investigations because this species is usually of low infectivity and virulence to laboratory rodents. Using 6 stocks of T. b. gambiense and 2 stocks of T. b. brucei, enzyme patterns of bloodstream and procyclic forms were identical for isocitrate dehydrogenase, malic enzyme, two nucleoside hydrolases (utilizing inosine and deoxyinosine respectively), phosphoglucomutase and superoxide dismutase. Procyclic forms appeared to have greater threonine dehydrogenase activity than bloodstream forms. Consistent differences between bloodstream and culture forms were observed for alanine aminotransferase, aspartate aminotransferase and malate dehydrogenase. These agreed with known differences in the metabolism of procyclic and bloodstream forms.

Biochemical characterization of Leishmania spp. isolated from man and wild animals in Kenya

Isoelectrofocusing in agarose was used to characterize Leishmania spp. isolated from a kala-azar patient, a lizard, genet cat and elephant shrew. Isoenzyme profiles of 12 enzymes and general protein patterns were examined. Both methods were found to be useful for distinguishing between the isolates. The wild animal Leishmania spp. were shown to be indistinguishable from a reference strain of L. major, but the isolate from man was distinctly different from L. donovani sensu stricto. The unique finding that the lizard isolate was similar to L. major and its significance are discussed in some detail. The use of the isoelectrofocusing technique for separation of enzymes and general proteins for characterization purposes is emphasized.

Leishmania infecting man and wild animals in Saudi Arabia. 5. Diversity of parasites causing visceral leishmaniasis in man and dogs in the south-west

Kala-azar (VL), mainly affecting infants and young children, is being increasingly reported in the south-west of Saudi Arabia, 305 cases being diagnosed in 1988. Most cases arise in scattered locations in the foothills west of the Asir mountains at altitudes between about 500 and 1000 m, although case clusters are apparent in some villages. Some cases also occur between the foothills and the Red Sea coast. The incidence in the south-west was calculated to be of the order of 6 to 8/10,000 population per year, but a random serological survey using the enzyme-linked immunosorbent assay and direct agglutination techniques indicated a seropositivity rate of about 3.7% in 706 apparently healthy children. Most patients are Saudi or Yemeni and cases are being increasingly identified also in the Yemen Arab Republic. In the foothills of both countries the causative organism is Leishmania donovani s.l. zymodeme LON-42, which also occurs on the eastern littoral of Ethiopia. By isoenzyme electrophoresis, it is readily separated from L. infantum, which has been identified in feral dogs, the 2 organisms being sympatric. The infection was found in 6.7% of 89 dogs, but their seropositivity rate was 19.3%. Although L. infantum has not yet been recognized in man in Saudi Arabia, it has been identified in a child in the coastal plain of the Yemen Arab Republic. Further research needed to provide a rational basis for control is discussed.

Characterization of West African Trypanosoma (Trypanozoon) brucei isolates from man and animals using isoenzyme analysis and DNA hybridization

A total of 18 West African Trypanosoma (Trypanozoon) brucei stocks isolated from man and animals were characterized using isoenzyme analysis with isoelectric focusing (IEF) and DNA hybridization. They were compared with four T. (T.) brucei isolates from East and West Africa that had previously been analysed and well defined. All experiments were carried out with cell lysates of procyclic trypanosomes produced in vitro. The different stocks could be separated into two distinct groups according to their isoenzyme and DNA patterns. The homogeneous group of T. b. gambiense was characterized by zymodeme A and highly specific DNA-banding patterns (type G) always associated with stable human serum resistance. The non-gambiense group (consisting of T.b. rhodesiense and T.b. brucei) was determined by a great variation in these markers. Our results clearly indicate the existence, of T.b. rhodesiense-like parasites in West African patients. Due to their lack of human serum resistance, the four characterized animal isolates can be referred to as T. b. brucei.

Trypanosoma congolense: the distribution of enzymic variants in east and west Africa

A total of 114 stocks of Trypanosoma congolense originating from Kenya, Uganda, Tanzania, Zambia and Sudan, but including, for comparison, stocks from The Gambia, Liberia, Ivory Coast, Nigeria and Cameroun, were compared by isoenzyme electrophoresis for 6 enzymes. The zymodemes were grouped, both from a dendrogram and using a cladistic method, after calculating the dissimilarity, or distance, between profiles. Previous observations are broadly confirmed, the zymodemes clustering separately according to geographical origin and ecological zone. Thus, one group was composed almost entirely of East African stocks, and another of stocks from both East and West Africa, although each group was of savanna origin. A third group was composed of stocks from the humid, rain-forest zones of West Africa, and was particularly characterized by isoenzyme variants of superoxide dismutase and glucose-phosphate isomerase. Two stocks from the Kenyan coast formed a markedly separate group, which may be taxonomically distinct.

Cutaneous leishmaniasis in Bolivia. A study of 185 human cases from Alto Beni (La Paz Department). Isolation and isoenzyme characterization of 26 strains of Leishmania braziliensis braziliensis [corrected]

A clinical, serological, parasitological and therapeutic study of cutaneous leishmaniasis was carried out in a low sub-andean area (250-800 metres) of the La Paz Department, Bolivia. A team of seismic prospectors (350 workers) was surveyed for 12 months. Of 200 suspected cases of cutaneous leishmaniasis, 185 were serologically or parasitologically confirmed (incidence 52.8%). Those exposed to the greatest risk of infection were working in a virgin forest environment. Leishmanial organisms were isolated from 26 of the workers, either by in vitro cultivation or inoculation into hamsters. Isoenzyme characterization of the organisms by cellulose acetate electrophoresis showed them to be Leishmania braziliensis braziliensis [corrected]. The results of treatment of 168 patients with a pentavalent antimonial drug are also reported.

Enzyme polymorphism and the identity of Trypanosoma brucei gambiense

Thirty-two isolates from man in known areas of Gambian trypanosomiasis, in the Sudan, Kenya, Zaire, Nigeria, Ivory Coast, Burkina Faso, Liberia and Senegal, were examined by isoenzyme electrophoresis of 11 enzymes. Comparisons were also made with our previously published results on 23 other stocks of similar origins, which had been examined in the same manner. All those stocks of low initial virulence to laboratory rodents, which thus conform to the accepted view of the behaviour of Trypanosoma brucei gambiense can be identified by characteristic combinations of enzyme patterns, especially certain aminotransferase markers. A limited study of superoxide dismutase polymorphism suggested a further marker of value. The isolates of high initial virulence to rodents, which are thus behaviourally akin to T. b. rhodesiense, did not share these characteristics. We conclude that there exists a homogeneous group of trypanosomes of wide dispersion throughout tropical Africa, characterized by certain isoenzyme combinations and low initial virulence to rodents, which corresponds to the classical concept of T. b. gambiense. The features of limited antigenic repertoire, high resistance to normal human serum and restriction fragment length polymorphisms of the genes for certain variant surface glycoproteins also appear to be characteristic of this group.

Isoenzyme changes during the life cycle of Trypanosoma cruzi

The isoenzyme profiles, for 14 enzymes, of amastigotes, trypomastigotes and epimastigotes were compared in various cloned and uncloned T. cruzi stocks belonging to different zymodemes. A culture method with a human diploid cell line was developed and produced either pure amastigotes or trypomastigotes in high yields. Trypomastigotes were also isolated from rat blood and from liquid culture. Epimastigotes were harvested from various acellular media and from the overlay of cell monolayers. The isoenzyme patterns of each life-cycle stage showed consistent differences in the number, position and intensity of the electrophoretic bands for certain enzymes. With the single exception of one peptidase, the variable patterns were stage-specific regardless of whether the organisms were harvested from animals or from various cultures at different temperatures.

Characterization by electrophoretic zymograms of 19 Trypanosoma cruzi clones derived from two chronic chagasic patients

1. Electrophoretic patterns of aspartate aminotransferase, glucose-6-phosphate dehydrogenase, phosphoglucomutase, glucose-phosphate isomerase, malic enzyme and alcohol dehydrogenase have been analyzed in extracts from Trypanosoma cruzi, Tulahuén strain, 19 clones derived from isolates obtained from two chronic chagasic patients from Argentina and from Brazilian stocks Silvio X10/1 (zymodeme 1), Esmeraldo/1 (zymodeme 2), and CAN-III/1 (zymodeme 3). 2. The clones isolated from one of the patients were genetically heterogeneous. 3. Phosphoglucomutase and glucose phosphate isomerase patterns for the clones analyzed clearly differ from those of the Brazilian stocks. 4. Grouping of clones on the basis of isozyme patterns showed some correlation with that based on total DNA per organism. 5. Under the experimental conditions used, the polyacrylamide gel electrophoresis micromethod employed was advantageous over starch gel electrophoresis.

Characterization of Kenyan Leishmania spp. and identification of Mastomys natalensis, Taterillus emini and Aethomys kaiseri as new hosts of Leishmania major

A survey to examine rodents for leishmanias was initiated in the Perkerra Settlement Scheme, Marigat, Baringo District, Kenya, 789 rodents of ten different species were trapped and examined. Leishmanial parasites were isolated from the spleen and liver of 17 animals of five different species: seven from Tatera robusta, five from Arvicanthis niloticus, two from Mastomys natalensis, two from Taterillus emini and one from Aethomys kaiseri. These were identified as L. major by enzyme electrophoresis, using 12 enzymes, and by excreted factor (EF) serotyping. The isolation of L. major from Mastomys natalensis, Taterillus emini and Aethomys kaiseri represent newly recorded hosts of L. major.