A barcode of multilocus nuclear DNA identifies genetic relatedness in pre- and post-Artemether/Lumefantrine treated Plasmodium falciparum in Nigeria

BACKGROUND

The decline in the efficacy of artemisinin-based combination treatment (ACT) in some endemic regions threatens the progress towards global elimination of malaria. Molecular surveillance of drug resistance in malaria-endemic regions is vital to detect the emergence and spread of mutant strains.

METHODS

We observed 89 malaria patients for the efficacy of artemether-lumefantrine for the treatment of uncomplicated Plasmodium falciparum infections in Lagos, Nigeria and determined the prevalence of drug resistant strains in the population. Parasite clearance rates were determined by microscopy and the highly sensitive var gene acidic terminal sequence (varATS) polymerase chain reaction for 65 patients with samples on days 0, 1, 3, 7, 14, 21 and 28 after commencement of treatment. The genomic finger print of parasite DNA from pre- and post-treatment samples were determined using 24 nuclear single nucleotide polymorphisms (SNP) barcode for P. falciparum. Drug resistance associated alleles in chloroquine resistance transporter gene (crt-76), multidrug resistance genes (mdr1-86 and mdr1-184), dihydropteroate synthase (dhps-540), dihydrofolate reductase (dhfr-108) and kelch domain (K-13580) were genotyped by high resolution melt analysis of polymerase chain reaction (PCR) fragments.

RESULTS

By varATS qPCR, 12 (18.5%) of the participants had detectable parasite DNA in their blood three days after treatment, while eight (12.3%) individuals presented with genotypable day 28 parasitaemia. Complexity of infection (CoI) was 1.30 on day 0 and 1.34 on day 28, the mean expected heterozygosity (HE) values across all barcodes were 0.50 ± 0.05 and 0.56 ± 0.05 on days 0 and 28 respectively. Barcode (π) pairwise comparisons showed high genetic relatedness of day 0 and day 28 parasite isolates in three (37.5%) of the eight individuals who presented with re-appearing infections. Crt-76 mutant allele was present in 38 (58.5%) isolates. The mdr1-86 mutant allele was found in 56 (86.2%) isolates. No mutation in the K-13580 was observed.

CONCLUSIONS

Persistence of DNA-detectable parasitaemia in more than 18% of cases after treatment and indications of genetic relatedness between pre- and post-treatment infections warrants further investigation of a larger population for signs of reduced ACT efficacy in Nigeria.

Detection of Mixed Infections with Plasmodium spp. by PCR, India, 2014

In 8 malaria-endemic states in India, mixed Plasmodium spp. infections were detected by PCR in 17.4% (265/1,521) of blood samples that microscopy had shown to contain only P. falciparum. The quality of microscopy must be improved because use of PCR for detection of malaria parasites is limited in rural areas.

Survey of Wild and Domestic Mammals for Infection with Leishmania infantum following an Outbreak of Desert Zoonotic Visceral Leishmaniasis in Jiashi, People's Republic of China

In 2008 and 2009, an outbreak of desert-subtype zoonotic visceral leishmaniasis occurred in Jiashi county, Xinjiang, China. So far, no animal reservoir has been identified for this type of visceral leishmaniasis. Therefore, we surveyed the most common mammals (wild and domestic) for Leishmania infections during the outbreak in 2008 and 2009 in order to identify the source of the visceral leishmaniasis in this region. Spleen, liver, bone marrow and blood samples collected from 86 wood mice (Apodemus sylvaticus), 61midday jirds (Meriones meridianus) and 27 Yarkand hares (Lepus yarkandensis) were tested for the presence of Leishmania by microscopy, culture and PCR. All of the animals were found to be negative for Leishmania infections; On the other hand, Leishmania DNA was detected in blood samples collected from livestock reared in the outbreak area: 30.36% (17/56) of sheep, 21.57% (11/51) of goats, 17.78% (8/45) of cattle, and 21.62 (8/37) of donkeys were positive for Leishmania DNA by PCR. The amplified kDNA sequences from the livestock samples matched Leishmania DNA sequences isolated from patients with visceral leishmaniasis in the study area. We suggest that these domestic mammals are a possible reservoir host for Leishmania infantum in the outbreak area.

Subtyping Cryptosporidium ubiquitum,a zoonotic pathogen emerging in humans

Cryptosporidium ubiquitum is an emerging zoonotic pathogen. In the past, it was not possible to identify an association between cases of human and animal infection. We conducted a genomic survey of the species, developed a subtyping tool targeting the 60-kDa glycoprotein (gp60) gene, and identified 6 subtype families (XIIa–XIIf) of C. ubiquitum. Host adaptation was apparent at the gp60 locus; subtype XIIa was found in ruminants worldwide, subtype families XIIb–XIId were found in rodents in the United States, and XIIe and XIIf were found in rodents in the Slovak Republic. Humans in the United States were infected with isolates of subtypes XIIb–XIId, whereas those in other areas were infected primarily with subtype XIIa isolates. In addition, subtype families XIIb and XIId were detected in drinking source water in the United States. Contact with C. ubiquitum–infected sheep and drinking water contaminated by infected wildlife could be sources of human infections.

RPS8--a new informative DNA marker for phylogeny of Babesia and Theileria parasites in China

Piroplasmosis is a serious debilitating and sometimes fatal disease. Phylogenetic relationships within piroplasmida are complex and remain unclear. We compared the intron–exon structure and DNA sequences of the RPS8 gene from Babesia and Theileria spp. isolates in China. Similar to 18S rDNA, the 40S ribosomal protein S8 gene, RPS8, including both coding and non-coding regions is a useful and novel genetic marker for defining species boundaries and for inferring phylogenies because it tends to have little intra-specific variation but considerable inter-specific difference. However, more samples are needed to verify the usefulness of the RPS8 (coding and non-coding regions) gene as a marker for the phylogenetic position and detection of most Babesia and Theileria species, particularly for some closely related species.

Host-parasite incongruences in rodent Eimeria suggest significant role of adaptation rather than cophylogeny in maintenance of host specificity

The degree of host specificity, its phylogenetic conservativeness and origin are virtually unknown in Eimeria. This situation is largely due to the inadequate sample of eimerian molecular data available for reliable phylogenetic analyses. In this study, we extend the data set by adding 71 new sequences of coccidia infecting 16 small-mammal genera, mostly rodents. According to the respective feasibility of PCR gene amplification, the new samples are represented by one or more of the following genes: nuclear 18S rRNA, plastid ORF 470, and mitochondrial COI. Phylogenetic analyses of these sequences confirm the previous hypothesis that Eimeria, in its current morphology-based delimitation, is not a monophyletic group. Several samples of coccidia corresponding morphologically to other genera are scattered among the Eimeria lineages. More importantly, the distribution of eimerians from different hosts indicates that the clustering of eimerian species is influenced by their host specificity, but does not arise from a cophylogenetic/cospeciation process; while several clusters are specific to a particular host group, inner topologies within these clusters do not reflect host phylogeny. This observation suggests that the host specificity of Eimeria is caused by adaptive rather than cophylogenetic processes.

Genetic diversity and lack of artemisinin selection signature on the Plasmodium falciparum ATP6 in the Greater Mekong Subregion

The recent detection of clinical Artemisinin (ART) resistance manifested as delayed parasite clearance in the Cambodia-Thailand border area raises a serious concern. The mechanism of ART resistance is not clear; but the P. falciparum sarco/endoplasmic reticulum Ca²⁺-ATPase (PfSERCA or PfATP6) has been speculated to be the target of ARTs and thus a potential marker for ART resistance. Here we amplified and sequenced pfatp6 gene (∼3.6 Kb) in 213 samples collected after 2005 from the Greater Mekong Subregion, where ART drugs have been used extensively in the past. A total of 24 single nucleotide polymorphisms (SNPs), including 8 newly found in this study and 13 nonsynonymous, were identified. However, these mutations were either uncommon or also present in other geographical regions with limited ART use. None of the mutations were suggestive of directional selection by ARTs. We further analyzed pfatp6 from a worldwide collection of 862 P. falciparum isolates in 19 populations from Asia, Africa, South America and Oceania, which include samples from regions prior to and after deployments ART drugs. A total of 71 SNPs were identified, resulting in 106 nucleotide haplotypes. Similarly, many of the mutations were continent-specific and present at frequencies below 5%. The most predominant and perhaps the ancestral haplotype occurred in 441 samples and was present in 16 populations from Asia, Africa, and Oceania. The 3D7 haplotype found in 54 samples was the second most common haplotype and present in nine populations from all four continents. Assessment of the selection strength on pfatp6 in the 19 parasite populations found that pfatp6 in most of these populations was under purifying selection with an average d_N/d_S ratio of 0.333. Molecular evolution analyses did not detect significant departures from neutrality in pfatp6 for most populations, challenging the suitability of this gene as a marker for monitoring ART resistance.

Anopheles moucheti and Anopheles vinckei are candidate vectors of ape Plasmodium parasites, including Plasmodium praefalciparum in Gabon

During the last four years, knowledge about the diversity of Plasmodium species in African great apes has considerably increased. Several new species were described in chimpanzees and gorillas, and some species that were previously considered as strictly of human interest were found to be infecting African apes. The description in gorillas of P. praefalciparum, the closest relative of P. falciparum which is the main malignant agent of human malaria, definitively changed the way we understand the evolution and origin of P. falciparum. This parasite is now considered to have appeared recently, following a cross-species transfer from gorillas to humans. However, the Plasmodium vector mosquito species that have served as bridge between these two host species remain unknown. In order to identify the vectors that ensure ape Plasmodium transmission and evaluate the risk of transfer of these parasites to humans, we carried out a field study in Gabon to capture Anopheles in areas where wild and semi-wild ape populations live. We collected 1070 Anopheles females belonging to 15 species, among which An. carnevalei, An. moucheti and An. marshallii were the most common species. Using mtDNA-based PCR tools, we discovered that An. moucheti, a major human malaria vector in Central Africa, could also ensure the natural transmission of P. praefalciparum among great apes. We also showed that, together with An. vinckei, An. moucheti was infected with P. vivax-like parasites. An. moucheti constitutes, therefore, a major candidate for the transfer of Plasmodium parasites from apes to humans.

Genotypes and mouse virulence of Toxoplasma gondii isolates from animals and humans in China

BACKGROUND

Recent population structure studies of T. gondii revealed that a few major clonal lineages predominated in different geographical regions. T. gondii in South America is genetically and biologically divergent, whereas this parasite is remarkably clonal in North America and Europe with a few major lineages including Types I, II and III. Information on genotypes and mouse virulence of T. gondii isolates from China is scarce and insufficient to investigate its population structure, evolution, and transmission.

METHODOLOGY/PRINCIPAL FINDINGS

Genotyping of 23 T. gondii isolates from different hosts using 10 markers for PCR-restriction fragment length polymorphism analyses (SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and Apico) revealed five genotypes; among them three genotypes were atypical and two were archetypal. Fifteen strains belong to the Chinese 1 lineage, which has been previously reported as a widespread lineage from swine, cats, and humans in China. Two human isolates fall into the type I and II lineages and the remaining isolates belong to two new atypical genotypes (ToxoDB#204 and #205) which has never been reported in China. Our results show that these genotypes of T. gondii isolates are intermediately or highly virulent in mice except for the strain TgCtwh6, which maintained parasitemia in mice for 35 days post infection although it possesses the uniform genotype of Chinese 1. Additionally, phylogenetic network analyses of all isolates of genotype Chinese 1 are identical, and there is no variation based on the sequence data generated for four introns (EF1, HP2, UPRT1 and UPRT7) and two dense granule proteins (GRA6 and GRA7).

CONCLUSION/SIGNIFICANCE

A limited genetic diversity was found and genotype Chinese 1 (ToxoDB#9) is dominantly circulating in mainland China. The results will provide a useful profile for deep insight to the population structure, epidemiology and biological characteristics of T. gondii in China.

Molecular diagnosis and species identification of imported malaria in returning travellers in Italy

A new seminested polymerase chain reaction (sn-PCR)-based protocol was developed and used to detect and identify Plasmodium species in 1226 whole-blood samples from patients (872 Italians and 354 foreigners) with at least 1 symptom compatible with clinical malaria. The results were compared with those obtained by microscopy: 187 samples were positive by microscopy for malaria parasites and 196 were positive by sn-PCR. When compared to microscopy, the sn-PCR detected different malaria parasite species in 11 cases. In 4 of 11 cases, the sn-PCR identified 1 additional malaria parasite species not observed microscopically, suggesting increased sensitivity. In 4 samples with levels of parasitemia too low for accurate identification of species by microscopy, the sn-PCR detected 2 P. falciparum, 1 P. ovale, and 1 P. falciparum plus P. ovale. Moreover, 9 negative samples by microscopy were positive by sn-PCR. Follow-up analysis demonstrated a parasite clearance of P. falciparum DNA up to 3 days after the disappearance of parasitemia at microscopy. In conclusion, sn-PCR-based diagnosis of malaria appears to be a useful tool when the results of conventional techniques are negative in the presence of a syndrome consistent with malaria, yielding accurate species identification and consequential correct treatment.

Detection of Plasmodium knowlesi by real-time polymerase chain reaction

We previously developed a real-time polymerase chain reaction (PCR) assay for detection of the four Plasmodium species that infect humans. Recent studies have shown that natural transmission of the simian parasite Plasmodium knowlesi to humans occurs frequently in Southeast Asia. We have expanded our PCR assay to include detection of P. knowlesi.

Phylogeny of Flabellulidae (Amoebozoa: Leptomyxida) inferred from SSU rDNA sequences of the type strain of Flabellula citata Schaeffer, 1926 and newly isolated strains of marine amoebae

New strains of non-vannellid flattened amoebae isolated from fish, an invertebrate and the marine environment were studied together with Flabellula citata Schaeffer, 1926 selected by morphology as a reference strain. The study revealed a paucity of features distinguishing individual strains at the generic level, but clearly evidenced mutual phylogenetic relationships within the assemblage of strains as well as their affiliation to the Leptomyxida. In this study, the SSU rDNA dataset of leptomyxids was expanded and a new branching pattern was presented within this lineage of Amoebozoa. Sequences of three newly introduced strains clustered in close relationship with the type strain of F. citata, the type species of the genus. Three strains, including one resembling Flamella sp., were positioned within a sister-group containing Paraflabellula spp. Results of phylogenetic analysis confirmed doubts of previous authors regarding generic assignment of several Rhizanmoeba and Ripidomnyxa strains.

Invasive amebiasis: an update on diagnosis and management

In its invasive form, the trophozoite is responsible for clinical syndromes, ranging from classical dysentery to extraintestinal disease with emphasis on hepatic amebiasis. Abdominal pain, tenderness and diarrhea of watery stool, sometimes with blood, are the predominant symptoms of amebic colitis. Besides the microscopic identification of Entamoeba histolytica, diagnosis should be based on the detection of specific antigens in the stool or PCR associated with the occult blood in the stool. Amebic dysentery is treated with metronidazole, followed by a luminal amebicide. The trophozoite reaches the liver causing hepatic amebiasis. Right upper quadrant pain, fever and hepatomegaly are the predominant symptoms. The diagnosis is made by the finding of E. histolytica in the hepatic fluid, or in the necrotic material at the edge of the lesion in a minority of patients, and by detection of antigens or DNA. Ultrasonography is the initial imaging procedure indicated. The local perforation of hepatic lesion leads to important and serious complications.

Malaria parasite developmental analyses by the nested polymerase chain reaction method: an implication for the evaluation of mosquito infection rates in epidemiological studies

A malaria mosquito vector, Anopheles saperoi, and a non-vector, Aedes albopictus, were allowed to feed on mice infected with murine malaria, Plasmodium yoelii nigeriensis, and were subsequently monitored for the development of parasites by the nested polymerase chain reaction (PCR) method, using Plasmodium genus-specific primer pairs. The mosquitos were divided into two parts, head/thorax and abdomen, for DNA analyses. The parasite DNA and murine DNA for each mosquito were examined in parallel. In both groups of mosquitos, murine DNA was detected up to 4 days post-blood meal in both the head/thorax and abdomen. After 4 days, the murine DNA fell below detectable limits. Murine DNA and parasite DNA remained undigested for the first 4 days post-blood meal. Parasite DNA was detected in the abdomen of 25% (3/12) of Ae. albopictus on day five and 10% (1/10) on day six, after murine DNA had fallen below detectable limits. Parasite DNA was not detected in the head/thorax of Ae. albopictus on those days or afterwards in either the head/thorax or abdomen, demonstrating that the parasite detected on days 5 and 6 in the abdomen degenerated and did not develop into mature oocysts or sporozoites. In the vector An. saperoi, parasite DNA was detected continuously in the head/thorax and abdomen for many days after the murine DNA had fallen below detectable limits. The detection rate of parasite DNA in the head/thorax of An. saperoi increased gradually from day 8 post blood meal until it reached a maximum level of 71.4% (15/21 12 days post-infection. Parasite DNA in abdomen reached its maximum level of 81% (17/21) 10 days post-blood meal. The implications of these results for the design and interpretation of epidemiological surveys is discussed.

A new method for detection of pfmdr1 mutations in Plasmodium falciparum DNA using real-time PCR

BACKGROUND

Surveillance for drug-resistant Plasmodium falciparum should be a component of malaria control programmes. Real-time PCR methods for the detection of parasite single-nucleotide polymorphisms (SNPs) and gene amplification could be useful survellance tools.

METHODS

A real-time PCR assay has been developed that identifies single nucleotide polymorphisms (SNPs) at amino acids 86, 184, 1034 and 1042 in the P. falciparum multi-drug resistant (pfmdr 1) gene that may be associated with anti-malarial drug resistance.

RESULTS

This assay has a sensitivity and specificity of 94% and 100% when compared to traditional PCR methods for genotyping. Only 54 of 68 (79%) paired pre- and post-culture DNA samples were concordant at all four loci.

CONCLUSION

Real-time PCR is a sensitive and specific method to detect SNP's in pfmdr 1. Genotypes of parasites after in vitro culture may not reflect that seen in vivo.

Presence of human Giardia in domestic, farm and wild animals, and environmental samples suggests a zoonotic potential for giardiasis

Giardia lamblia which parasitize humans belong to either of two genotypes, A or B, based on specific signature sequences in the 5' end of the small subunit (16S) ribosomal RNA (rRNA) gene. These two genotypes also were found in cysts from fecal samples of animal origin such as dogs, cats, some farm animals and wild animals. In addition, trophozoites recovered from cysts obtained from environmental samples belonged to these two genotypes as well, suggesting that the G. lamblia genotypes A and B are widespread and possibly zoonotic. Trophozoites were recovered from rats and these isolates might belong to another genotype of G. lamblia. Deer mice and one dog appeared to be parasitized by genotypes of Giardia with close affinity to G. microti. This species, therefore, also consists of a genotype complex.

Two main clusters within Trypanosoma cruzi zymodeme 3 are defined by distinct regions of the ribosomal RNA cistron

Trypanosoma cruzi is currently classified into 2 major phylogenetic lineages, T. cruzi I and II, that correlate with the formerly described zymodeme 1 and 2, respectively. Another isoenzymic group (zymodeme 3-Z3) was also described. In this study, we analysed the genetic diversity among Z3 isolates of the Brazilian Amazon by restriction fragment length polymorphism of the intergenic transcribed spacers (ITSs) of the ribosomal RNA cistron and the size of the divergent domain D7 of the 24Salpha rRNA gene. DNAs from 12 T. cruzi Z3 isolates obtained from humans (2), Panstrongylus geniculatus (1), and Rhodnius brethesi (9) were submitted to PCR amplification of the ITSs plus the 5.8S rDNA. The PCR products were digested with 4 distinct endonucleases and the profiles analysed by a numerical methodology. The phenetic dendrogram revealed a clear dichotomy in the Z3 group, defining 2 groups that were named Z3-A and Z3-B. Dimorphism was also found in the band sizes of the amplified D7 divergent domain of the 24Salpha rDNA, which showed a perfect correlation with the ITSs clustering. The organization of the ribosomal cistron was investigated by Southern blotting and shown to be conserved in the genome of the 2 Z3 groups. This study shows that the rDNA cistron allows the definition of 2 distinct subclusters in Z3 isolates.

Microsatellite analysis of Toxoplasma gondii shows considerable polymorphism structured into two main clonal groups

Previous studies on Toxoplasma gondii population structure, based essentially on multilocus restriction fragment length polymorphism analysis or on multilocus enzyme electrophoresis, indicated that T. gondii comprises three clonal lineages. These studies showed a weak polymorphism of the markers (2-4 alleles by locus). In this study, we used eight microsatellite markers to type 84 independent isolates from humans and animals. Two microsatellite markers were present in the introns of two genes, one coding for beta-tubulin and the other for myosin A, and six were found in expressed sequence tags. With 3-16 alleles detected, these markers can be considered as the most discriminating multilocus single-copy markers available for typing T. gondii isolates. This high discriminatory power of microsatellites made it possible to detect mixed infections and epidemiologically related isolates. Evolutionary genetic analyses of diversity show that the T. gondii population structure consists of only two clonal lineages that can be equated to discrete typing units, but there is some evidence of occasional genetic exchange that could explain why one of these discrete typing units is less clearly individualised than the other.

Structural basis of karyotype heterogeneity in Giardia lamblia

The molecular karyotype of a series of Giardia lamblia isolates representing the two major genotypes (Groups 1 and 3) was generated by assigning 13 genetic markers to chromosomes separated by pulsed-field gel electrophoresis. The co-localization identified five linked groups of genetic markers in Group 1 isolates. For each of the five linkage groups, there were up to four size variants that hybridized with the same genetic markers. Long range physical maps of the regions flanking the low copy number genetic markers indicated that these size variants were homologous chromosomes. The linkage groups were similar in Group 1 and 3 isolates. The core of each chromosome was stable while the subtelomeres were variable. The location of the ribosomal DNA repeats was variable among the different isolates and they were found in the subtelomeric regions of any of the five linkage groups. The data suggest a functional ploidy of at least four. Hypervariable subtelomeric regions of homologous chromosomes provide the structural basis of the chromosome size heterogeneity that is characteristic of G. lamblia.

Sequence analysis of the major piroplasm surface protein gene of benign bovine Theileria parasites in east Asia

Relatively benign Theileria parasites are widespread among cattle in East Asia. Although the parasites are presumed to be of the Theileria sergenti/Theileria buffeli/Theileria orientalis group, their taxonomic status and epidemiology have not been well defined. In the present study, theilerial DNA samples were collected from various East Asian countries, including Japan, Korea, Taiwan, and China. DNA sequences encoding a major piroplasm surface protein were amplified by polymerase chain reaction, followed by cloning into a plasmid vector. More than 20 DNA clones derived from parasite DNA of a single infected animal were examined for their restriction-fragment-length polymorphism, showing that they were classified into four major types. Sequence analysis revealed six types of DNA sequences encoding major piroplasm surface protein with homologies of between 75 and 91%. Of the six sequences, four were identical to those previously reported, while the other two appeared to be new sequences. Among the DNA clones derived from a single infected animal, two to three distinct sequences were often found. Phylogenetic analysis of the six major piroplasm surface protein sequences indicates that five of the six are closely related to each other, and that all are distantly related to the homologous genes of Theileria annulata and Theileria parva. The results suggest that, in addition to those described as T. sergenti/T. buffeli/T. orientalis, there may be some undefined Theileria species distributed in East Asia, and that many cattle are infected with mixed populations of geographically variable Theileria parasites.

Differentiation of Entamoeba histolytica and E. dispar DNA from cysts present in stool specimens by polymerase chain reaction: its field application in the Philippines

It has been established that two distinct species exist within what was originally known as Entamoeba histolytica. These are E. dispar and E. histolytica, for the nonpathogenic and pathogenic forms, respectively. Differentiation of these two organisms is of great clinical importance since they are morphologically indistinguishable and both forms can infect the human intestinal cavity to different degrees. A simple and rapid DNA-extraction method that can be used directly on formalin-fixed stool specimens has been developed. The extracted DNA was used for the identification of the species existing in the stools by polymerase chain reaction (PCR). A total of 72 randomly collected stool samples from the Philippines were analyzed. In all, 19 samples reacted with E. dispar primers, resulting in the expected 101-bp PCR products; however, none reacted with E. histolytica primers. Furthermore, sensitivity assay suggests that genomic DNA from as few as five cysts can be used as a template for PCR. These observations imply that the use of genomic DNA directly extracted from formalin-fixed stool specimens for PCR amplification is a useful tool for obtaining a sensitive and accurate diagnosis that can be applied even in epidemiology studies.

Mini- and micro-satellites in the genome of rodent malaria parasites

Higher eukaryotes contain within their DNA numerous arrays of repetitive DNA, many of which are known as satellite DNAs and display extensive variability. The presence of these repeats has been demonstrated for various species and they have been used for genetic identification and classification. Here, it is demonstrated that Southern hybridisation of DNA from rodent malaria parasites allows detection of micro- and minisatellite sequences in the genome of Plasmodium species. Closely related lines of malaria parasites exhibit a monomorphic hybridisation pattern, which is in contrast to the allelic variation observed in higher eukaryotes. Among different species, however, restriction-fragment length polymorphism was observed. Pulsed-field gel electrophoretic chromosome separation showed that the probes used in this study [33.15, 33.6, (CAC)n and (GT)n] detect several loci spread over different chromosomes.