Genetic analysis of praziquantel response in schistosome parasites implicates a transient receptor potential channel

[Figure: see text].

Oxamniquine resistance alleles are widespread in Old World Schistosoma mansoni and predate drug deployment

Do mutations required for adaptation occur de novo, or are they segregating within populations as standing genetic variation? This question is key to understanding adaptive change in nature, and has important practical consequences for the evolution of drug resistance. We provide evidence that alleles conferring resistance to oxamniquine (OXA), an antischistosomal drug, are widespread in natural parasite populations under minimal drug pressure and predate OXA deployment. OXA has been used since the 1970s to treat Schistosoma mansoni infections in the New World where S. mansoni established during the slave trade. Recessive loss-of-function mutations within a parasite sulfotransferase (SmSULT-OR) underlie resistance, and several verified resistance mutations, including a deletion (p.E142del), have been identified in the New World. Here we investigate sequence variation in SmSULT-OR in S. mansoni from the Old World, where OXA has seen minimal usage. We sequenced exomes of 204 S. mansoni parasites from West Africa, East Africa and the Middle East, and scored variants in SmSULT-OR and flanking regions. We identified 39 non-synonymous SNPs, 4 deletions, 1 duplication and 1 premature stop codon in the SmSULT-OR coding sequence, including one confirmed resistance deletion (p.E142del). We expressed recombinant proteins and used an in vitro OXA activation assay to functionally validate the OXA-resistance phenotype for four predicted OXA-resistance mutations. Three aspects of the data are of particular interest: (i) segregating OXA-resistance alleles are widespread in Old World populations (4.29–14.91% frequency), despite minimal OXA usage, (ii) two OXA-resistance mutations (p.W120R, p.N171IfsX28) are particularly common (>5%) in East African and Middle-Eastern populations, (iii) the p.E142del allele has identical flanking SNPs in both West Africa and Puerto Rico, suggesting that parasites bearing this allele colonized the New World during the slave trade and therefore predate OXA deployment. We conclude that standing variation for OXA resistance is widespread in S. mansoni.

It has been argued that drug resistance is unlikely to spread rapidly in helminth parasites infecting humans. This is based, at least in part, on the premise that resistance mutations are rare or absent within populations prior to treatment, and take a long time to reach appreciable frequencies because helminth parasite generation time is long. This argument is critically dependent on the starting frequency of resistance alleles–if high levels of “standing variation” for resistance are present prior to deployment of treatment, resistance may spread rapidly. We examined frequencies of oxamniquine resistance alleles present in Schistosoma mansoni from Africa and the Middle East where oxamniquine has seen minimal use. We found that oxamniquine resistance alleles are widespread in the Old World, ranging from 4.29% in the Middle East to 14.91% in East African parasite populations. Furthermore, we show that resistance alleles from West African and the Caribbean schistosomes share a common origin, suggesting that these alleles travelled to the New World with S. mansoni during the transatlantic slave trade. Together, these results demonstrate extensive standing variation for oxamniquine resistance. Our results have important implications for both drug treatment policies and drug development efforts, and demonstrate the power of molecular surveillance approaches for guiding helminth control.

Host-parasite life-histories of the diurnal vs. nocturnal chronotypes of Schistosoma mansoni: adaptive significance

OBJECTIVES

To optimise host-to-host transmission, digenean trematodes (parasites) synchronise their cercarial emission patterns with the aquatic activities of their vertebrate hosts. Schistosoma mansoni has two different circadian chronotypes: a diurnal shedding pattern with a mean peak occurring at 11:00 h, and a nocturnal shedding pattern with a mean peak occurring at 20:00 h. We analysed the life-history variations between these two chronotypes at the levels of the parasite and its hosts.

METHODS

For each chronotype, we quantified three life-history traits related to the parasite (prepatent period, infection rate and cercarial production) and analysed the morphometry and the morphology of the parasite eggs; we also quantified three life-history traits related to the snail intermediate host (shell diameter, fecundity and survival rate) and one life-history trait related to the experimental definitive host (survival rate). A phylogeny based on the mitochondrial cytochrome-oxidase gene was made on samples of both chronotypes.

RESULTS

Life-history analysis revealed significant variations between the two chronotypes. Life-history traits were optimal for both the parasite and the snail host for the diurnal chronotype compared to the nocturnal one. The new chronotype behaved like an allopatric population towards its snail host. Phylogenetic analysis supports the hypothesis of a lateral transfer of S. mansoni from humans to Rattus rattus. These results were interpreted in terms of an ongoing sympatric speciation.

CONCLUSION

The nocturnal chronotype of S. mansoni showed non-adapted life-history traits in its relation with the snail intermediate host Biomphalaria pfeifferi. The emergence of this new phenotype is probably linked to divergent natural selection.

Increased CD86 but Not CD80 and PD-L1 Expression on Liver CD68+ Cells during Chronic HBV Infection

BACKGROUND

The failure to establish potent anti-HBV T cell responses suggests the absence of an effective innate immune activation. Kupffer cells and liver-infiltrating monocytes/macrophages have an essential role in establishing anti-HBV responses. These cells express the costimulatory molecules CD80 and CD86. CD80 expression on antigen-presenting cells (APCs) induces Th1 cell differentiation, whereas CD86 expression drives the differentiation towards a Th2 profile. The relative expression of CD80, CD86 and PD-L1 on APCs, regulates T cell activation. Few studies investigated CD80 and CD86 expression on KCs and infiltrating monocytes/macrophages in HBV-infected liver and knowledge about the expression of PD-L1 on these cells is controversial. The expression of these molecules together in CD68+ cells has not been explored in HBV-infected livers.

METHODS

Double staining immunohistochemistry was applied to liver biopsies of HBV-infected and control donors to explore CD80, CD86 and PD-L1 expression in the lobular and portal areas.

RESULTS

Chronic HBV infection was associated with increased CD68+CD86+ cell count and percentage in the lobular areas, and no changes in the count and percentage of CD68+CD80+ and CD68+PD-L1+ cells, compared to the control group. While CD68+CD80+ cell count in portal areas correlated with the fibrosis score, CD68+CD80+ cell percentage in lobular areas correlated with the inflammation grade.

CONCLUSION

The upregulation of CD86 but not CD80 and PD-L1 on CD68+ cells in HBV-infected livers, suggests that these cells do not support the induction of potent Th1. Moreover, the expression of CD80 on CD68+ cells correlates with liver inflammation and fibrosis.

Frequency of TLR4 (1063A/G and 1363C/T) polymorphisms in healthy and HIV-infected Omani individuals and their relationship to viral load and T cell count

Toll-like receptors (TLRs) are essential elements of the innate immune response to different infections including the infection with human immunodeficiency virus (HIV). Single nucleotide polymorphisms (SNPs) in TLRs such as TLR4 1063A/G and 1363C/T have been found to be associated with changes in CD4 count, viral load (VL), and disease progression during HIV infection. However, the association of these SNPs with the pathogenesis during HIV infection is controversial. We investigated the frequency of TLR4 1063A/G and 1363C/T SNPs in 168 Omani donors [68 HIV-infected patients (>3% of Omani HIV-infected patients) and 100 healthy controls] and the association of these SNPs with the VL, CD8 and CD4 counts, and the immune recovery after cART as observed by CD4 T cell increase. SNPs were analyzed after the amplification of the regions that contain them by polymerase chain reaction (PCR) and sequencing of the PCR products. The TLR4 1063GG genotype was detected in the HIV-infected group only. No association was found between the studied SNPs and the average VL during 1 year of infection, the average CD4 and CD8 count during 1 year of viremia, the nadir CD4 count, the CD4 count when the patient reached VL < 50 copies/mL due to cART, and the ratio of the CD4 count 3 and 6 months after reaching VL < 50 copies/mL after cART to the last CD4 count before reaching VL < 50 copies/mL. Our study suggests that TLR4 (1063A/G and 1363C/T) SNPs have no association with the VL or the CD4 and CD8 counts during HIV infection.

Plasmodium falciparum population structure in Sudan post artemisinin-based combination therapy

Over the past decade, Sudan has stepped up malaria control backed by WHO, and this has resulted in significant reduction in parasite rate, malaria morbidity and mortality. The present study analyzed Plasmodium falciparum parasites in four geographical separated areas, to examine whether the success in malaria control following the use of artemisinin-based combination therapy (ACT) has disrupted the population structure and evolution of the parasite. We examined 319 P. falciparum isolates collected between October 2009 and October 2012 in four different areas in Sudan (Jazira [central Sudan], Southern Darfur [western Sudan], Upper Nile [southern Sudan] and Kasala [eastern Sudan]). Twelve microsatellites were analyzed for allelic diversity, multi-locus haplotype and inter-population differentiation. Level of diversity was compared to that detected for three of the above microsatellites among P. falciparum parasites in central and eastern Sudan in 1999, prior to introduction of ACT. Diversity at each locus (unbiased heterozygosity [H]) was high in all areas (Jazira, H=0.67), (Southern Darfur, H=0.71), (Upper Nile, H=0.71), and (Kasala, H=0.63). Microsatellites were distributed widely and private alleles, detected in a single population, were rare. The extent of diversity in the above sites was similar to that seen, in 1999, in central (Khartoum, H=0.73) and eastern Sudan (Gedaref, H=0.75). Significant Linkage disequilibrium (LD) was observed between the microsatellites in all populations. Pairwise FST analysis revealed that parasites in the four areas could be considered as one population. However, the parasites in Sudan clustered away from parasites in West Africa and the Arabian Peninsula. Despite marked reduction in malaria risk in Sudan, the extent of diversity and parasite genetic structure are indicative of a large population size. Further considerable reduction in transmission would be needed before fragmented sub-population can be seen. In addition, the large divergence of P. falciparum in Sudan from West Africa and Arabian Peninsula populations may result from differential evolutionary pressures acting at the population level, which shall be considered in eradication plans.

Knowledge, attitudes and intended behaviours towards HIV testing and self-protection: a survey of Omani pregnant women

Routine HIV testing of all pregnant women in Oman has been introduced without prior knowledge of women's attitudes towards testing or their behaviour in the event of a positive test. This study recruited 1000 Omani pregnant women from antenatal clinics to explore their knowledge of HIV/AIDS, attitudes towards HIV testing and intended behaviours in the event of a positive test. Mother-to-child transmission was recognized by 86.6% of the women but only 21.0% knew that it was preventable and a few acknowledged the important role of antiviral drugs. Half of the women (51.9%) reported having been tested for HIV and 75.8% agreed about routine HIV testing for all pregnant women. A higher level of knowledge was significantly associated with a favourable intended behaviour related to voluntary testing, disclosure and seeking professional assistance in the event of a positive HIV test. The results are discussed in relation to opt-in and opt-out approaches to voluntary testing during pregnancy.

Misdiagnosed infected aneurysm presenting as pyrexia of unknown origin (PUO)

Infected aneurysm is a life threatening clinical condition that is associated with significant morbidity and mortality. Early detection is essential for a rapid and efficacious initial treatment for better prognosis. Since the introduction of antibiotic therapy and concomitant decline of endocarditis, true mycotic aneurysms are rarely seen. The usual treatment consists of antibiotics along with aggressive surgical debridement of the infected tissue and vascular reconstruction, if needed. We here describe an infected aneurysm presenting as pyrexia of unknown origin and discuss the clinical features and challenges encountered in the treatment.

Association of single-nucleotide polymorphisms in TLR7 (Gln11Leu) and TLR9 (1635A/G) with a higher CD4T cell count during HIV infection

BACKGROUND

Toll-like receptors (TLRs) are essential elements of the innate immune response to different infections including HIV-1 infection. The single-nucleotide polymorphisms (SNPs) in TLRs have been associated with CD4T cell count and HIV disease progression. The TLR7 (Gln11Leu) SNP was shown to be associated with a rapid decline of CD4T cell count. A relation between TLR9 (1635A/G) SNP and CD4T cells count in HIV-infected patients is suggested, although the outcome associated with this SNP is still controversial.

OBJECTIVES

To determine the relation of the TLR7 (Gln11Leu) and TLR9 (1635A/G) SNPs with the damage to the immune system during HIV infection as reflected by the average CD4T cell count.

METHODS

A total of 63 HIV-infected patients and 100 healthy individuals (controls) were enrolled in this study. The above named SNPs were analyzed after amplification of the regions that potentially contain the SNPs by polymerase chain reaction (PCR) and sequencing of the PCR products. The frequency of these SNPs and their relation with the CD4T cell count were investigated.

RESULTS

The TLR7 (AA) genotype 'Gln' had a trend toward being associated with a CD4T cell count >400cells/μl after controlling viremia via HAART. Additionally, the TLR9 1635 (GG) genotype was associated with a low average CD4T cell count and the TLR9 1635 (AG) genotype was significantly related to a higher average CD4T cell count during the viremic period in HIV-infected patients.

CONCLUSION

The results of this longitudinal study supports the presence of an association between the TLR9 (1635A/G) genotype and the CD4T cell count, which helps clarifying the controversial results regarding this association. It also suggests that the CD4T cell count during the viremic period might be linked to the combination of both TLR7 (Gln11Leu) and TLR9 (1635A/G) genotypes. These results may help predicting the damage to the immune system, and thus impacting the planning for novel anti-HIV strategies.

Genetic diversity of Plasmodium falciparum and distribution of drug resistance haplotypes in Yemen

Background

Despite evident success of malaria control in many sites in the Arabian Peninsula, malaria remains endemic in a few spots, in Yemen and south-west of Saudi Arabia. In addition to local transmission, imported malaria sustains an extra source of parasites that can challenge the strengths of local control strategies. This study examined the genetic diversity of Plasmodium falciparum in Yemen and mutations of drug resistant genes, to elucidate parasite structure and distribution of drug resistance genotypes in the region.

Methods

Five polymorphic loci (MSP-2, Pfg377 and three microsatellites on chromosome 8) not involved in anti-malarial drug resistance, and four drug resistant genes (pfcrt, pfmdr1, dhfr and dhps) were genotyped in 108 P. falciparum isolates collected in three sites in Yemen: Dhamar, Hodeidah and Taiz.

Results

High diversity was seen in non-drug genes, pfg377 (He = 0.66), msp-2 (He = 0.80) and three microsatellites on chr 8, 7.7 kb (He = 0.88), 4.3 kb (He = 0.77) and 0.8 kb (He = 0.71). There was a high level of mixed-genotype infections (57%), with an average 1.8 genotypes per patient. No linkage disequilibrium was seen between drug resistant genes and the non-drug markers (p < 0.05). Genetic differentiation between populations was low (most pair-wise F_ST values <0.03), indicating extensive gene flow between the parasites in the three sites.

There was a high prevalence of mutations in pfmdr1, pfcrt and dhfr; with four mutant pfmdr1 genotypes (NFCDD[57%], NFSND[21%], YFCDD[13%] and YFSND[8% ]), two mutant pfcrt genotypes (CVIET[89%] and SVMNT[4%]) and one mutant dhfr genotype (ICNI[53.7%]). However, no dhps mutations were detected.

Conclusion

The high diversity of P. falciparum in Yemen is indicative of a large parasite reservoir, which represents a challenge to control efforts. The presence of two distinct pfcrt genotype, CVIET and SVMNT, suggests that chloroquine resistance can possibly be related to a migratory path from Africa and Asia. The absence of the triple mutant dhfr genotype (IRN) and dhps mutations supports the use of artesunate + sulphadoxine-pyrimethamine as first-line therapy. However, the prevalent pfmdr1 genotype NFSND [21%] has previously been associated with tolerance/resistance response to artemisinin combination therapy (ACT). Regular surveys are, therefore, important to monitor spread of pfmdr1 and dhfr mutations and response to ACT.

A new chronotype of Schistosoma mansoni: adaptive significance

OBJECTIVES

To optimise host-to-host transmission, digenean trematodes (parasites) synchronize their cercarial emission patterns with the aquatic activities of their vertebrate hosts. Schistosoma mansoni has a strictly diurnal shedding pattern involving two circadian chronotypes: an early shedding pattern with a mean peak occurring at 11:00 h and a late pattern with a mean peak occurring at 16:00 h. We analysed the cercarial emergence pattern of three schistosome populations from Oman where S. mansoni is resurgent.

METHODS

For each schistosome population, the cercarial emergence pattern was assessed hourly over several days. Because we identified a new chronotype hitherto unknown in S. mansoni, we undertook taxonomic characterisation based on egg morphology and mitochondrial DNA sequence (COX1).

RESULTS

Taxonomic characterisation revealed that the three schistosome populations belong to the species S. mansoni. Hence, this is the first report of this species exhibiting a nocturnal chronotype, with the mean peak occurring at 20:00 h. We interpreted the new chronotype as being the result of a lateral transfer of S. mansoni from humans to Rattus rattus.

CONCLUSION

The cercarial emergence pattern of S. mansoni from Oman is circadian, exhibiting either a diurnal or a nocturnal phenotype.

Source of drug resistant Plasmodium falciparum in a potential malaria elimination site in Saudi Arabia

A major challenge to the success of malaria control program in Saudi Arabia is the high influx of expatriates and holy visitors from malaria endemic countries. In the present study we examined whether drug resistant parasite genotypes reported in Jazan region, southwest of Saudi Arabia are imported or developed locally. We examined 178 Plasmodium falciparum isolates for alleles of dihydropteroate synthase (dhps) and dihydrofolate reductase (dhfr), associated with Sulfadoxine-Pyrimethamine (SP) resistance, and three microsatellites flanking each gene. In addition, we examined a neutral polymorphic gene (Pfg377). We compared the dhfr and dhps haplotypes in Jazan, using network analysis, to an existing similar data set of 94 P. falciparum isolates from eastern Sudan. In Jazan, double mutant dhfr allele (51I, 108N) occurred with a prevalence of 33%. The vast majority (99%) of dhps were wild-type alleles. The mean expected heterozygosity (H(e)) of microsatellites around mutant dhfr alleles (H(e)=0.312; n=60) was lower (P ≤ 0.05) than that around the wild-type allele (H(e)=0.834; n=116). Also, the mutant dhfr isolates showed high H(e) for dhps (H(e)=0.80) and the non-drug resistance locus Pfg377 (H(e)=0.63) indicative of selection for mutant dhfr only. The predominant double mutant dhfr haplotype in Jazan (73%), was prevalent among P. falciparum in east Africa. Network analysis suggests the mutant haplotype of dhfr gene was possibly introduced into Jazan from East Africa. The absence of mutations in dhps as well as triple mutant dhfr haplotype associated with SP failure support the current use of SP as a partner with artesunate as a first line therapy in Saudi Arabia. However, the close relationship between the major mutant dhfr haplotype in Sudan and Saudi Arabia, favour the hypothesis of recent migration as a source of the major resistant dhfr lineage. Thus, regular monitoring of the dhfr and dhps haplotypes is of high priority to guard possible importation of high level SP resistant lineages.

Major inorganic elements in tap water samples in Peninsular Malaysia

INTRODUCTION

Quality drinking water should be free from harmful levels of impurities such as heavy metals and other inorganic elements.

METHODS

Samples of tap water collected from 24 locations in Peninsular Malaysia were determined for inorganic element content. Minerals and heavy metals were analysed by spectroscopy methods, while non-metal elements were analysed using test kits.

RESULTS

Minerals and heavy metals determined were sodium, magnesium, potassium, calcium, chromium, manganese, iron, nickel, copper, zinc, arsenic, cadmium and lead while the non-metal elements were fluoride, chloride, nitrate and sulphate. Most of the inorganic elements found in the samples were below the maximum permitted levels recommended by inter-national drinking water standard limits, except for iron and manganese. Iron concentration of tap water from one of the locations was higher than the standard limit.

CONCLUSION

In general, tap water from different parts of Peninsular Malaysia had low concentrations of heavy metals and inorganic elements.

The phylogeography of Indoplanorbis exustus (Gastropoda: Planorbidae) in Asia

BACKGROUND

The freshwater snail Indoplanorbis exustus is found across India, Southeast Asia, central Asia (Afghanistan), Arabia and Africa. Indoplanorbis is of economic importance in that it is responsible for the transmission of several species of the genus Schistosoma which infect cattle and cause reduced livestock productivity. The snail is also of medical importance as a source of cercarial dermatitis among rural workers, particularly in India. In spite of its long history and wide geographical range, it is thought that Indoplanorbis includes only a single species. The aims of the present study were to date the radiation of Indoplanorbis across Asia so that the factors involved in its dispersal in the region could be tested, to reveal potential historical biogeographical events shaping the phylogeny of the snail, and to look for signs that I. exustus might be polyphyletic.

RESULTS

The results indicated a radiation beginning in the late Miocene with a divergence of an ancestral bulinine lineage into Assam and peninsular India clades. A Southeast Asian clade diverged from the peninsular India clade late-Pliocene; this clade then radiated at a much more rapid pace to colonize all of the sampled range of Indoplanorbis in the mid-Pleistocene.

CONCLUSIONS

The phylogenetic depth of divergences between the Indian clades and Southeast Asian clades, together with habitat and parasitological differences suggest that I. exustus may comprise more than one species. The timescale estimated for the radiation suggests that the dispersal to Arabia and to Southeast Asia was facilitated by palaeogeographical events and climate change, and did not require human involvement. Further samples from Afghanistan, Africa and western India are required to refine the phylogeographical hypothesis and to include the African Recent dispersal.

Influence of pattern of exposure, parasite genetic diversity and sex on the degree of protection against reinfection with Schistosoma mansoni

This paper analyzed, experimentally, the influences of pattern of exposure, parasite genetic diversity, and parasite sex on the degree of protection against reinfection with Schistosoma mansoni in the mouse. The results show that, (1) in infections with one male parasite genotype, successive infections induced a significant decrease in the infectivity of the parasite and significant increases in the spleen and liver weights compared to mass infections, (2) successive infections with one male genotype induced a significant decrease in the infectivity of the parasite compared to successive infections with five male genotypes, and (3) genotype infectivities were determined by the order at which they were used in the successive infections. These results are discussed in terms of protective effect and concomitant immunity and provide an ecological explanation of the natural sex-biased dispersal toward the male schistosomes.

Vaginal hirudiniasis from Dhaherah Province, Oman: With a Note on Internal Hirudiniasis

A 75 years old lady from the Dhaherah Province, Oman, presented at Ibri Hospital, complaining from abnormal vaginal bleeding. Histopathological investigations of a cervical biopsy revealed no atypical features. A worm-like organism was removed from the vagina. Histocytological investigations of the organism revealed typical structures of a leech. The case was identified as vaginal hirudiniasis, probably due to Limnatis nilotica that necessitated a note on internal hirudiniasis.

Laboratory Studies on the Prevalence and Cercarial Rhythms of Trematodes from Bulinus truncatus and Biomphalaria Pfeifferi Snails from Khartoum State, Sudan

OBJECTIVES

(a) To determine the natural infection rate of Bulinus truncatus and Biomphalaria pfeifferi snails with trematodes' cercariae. (b) To determine the emergence and rhythmicity of cercariae. (c) To elucidate the high-risk time for man and other animals to acquire infection.

METHODS

Snails were collected from Dawar El Mahadi Agricultural Scheme, Khartoum State, identified in the laboratory, kept at room temperature and fed on lettuce. The snails were screened weekly for six weeks for natural infection and infected snails were kept in the dark. The swimming patterns and resting position of the freshly emerged cercariae were studied using a stereomicroscope. The rhythmicity of the different types of cercariae was studied by screening three sets of 5 naturally infected snails under fluorescent light from 07.00 to 19.00 and similar sets from 19.00 to 07.00.

RESULTS

Out of 1,257 screened Bulinus truncatus, 187 (14.9%) shed four types of cercariae. The highest prevalence of natural infection (9.5%) was by schistosome cercariae followed by amphistome (2.5%), xiphidiocercariae (2.4%) and lastly by avian cercariae (0.5%). However, out of 200 screened B. pfeifferi, 22 (11%) shed only xiphidiocercariae. The rhythmicity studies showed that the emergence of schistosome cercariae increased steadily from 07.00 to reach its peak at 11.00-13.00. The emergence rhythms of avian cercariae are similar to those of the schistosome, but with an early peak at 09.00-11.00. The xiphidiocercariae and amphistome cercariae started with high rate of emergence at 07.00. and decreased gradually to very low levels or complete disappearance, respectively, around sunset.

CONCLUSION

Information on cercarial rhythmicity and chronobiological characteristics are thought to be useful in avoiding water contact during high-risk time of infection and may be helpful in the identification of closely related species and strains of cercariae.

Origin and diversification of the human parasite Schistosoma mansoni

Schistosoma mansoni is the most widespread of the human-infecting schistosomes, present in 54 countries, predominantly in Africa, but also in Madagascar, the Arabian Peninsula, and the Neotropics. Adult-stage parasites that infect humans are also occasionally recovered from baboons, rodents, and other mammals. Larval stages of the parasite are dependent upon certain species of freshwater snails in the genus Biomphalaria, which largely determine the parasite's geographical range. How S. mansoni genetic diversity is distributed geographically and among isolates using different hosts has never been examined with DNA sequence data. Here we describe the global phylogeography of S. mansoni using more than 2500 bp of mitochondrial DNA (mtDNA) from 143 parasites collected in 53 geographically widespread localities. Considerable within-species mtDNA diversity was found, with 85 unique haplotypes grouping into five distinct lineages. Geographical separation, and not host use, appears to be the most important factor in the diversification of the parasite. East African specimens showed a remarkable amount of variation, comprising three clades and basal members of a fourth, strongly suggesting an East African origin for the parasite 0.30-0.43 million years ago, a time frame that follows the arrival of its snail host. Less but still substantial variation was found in the rest of Africa. A recent colonization of the New World is supported by finding only seven closely related New World haplotypes which have West African affinities. All Brazilian isolates have nearly identical mtDNA haplotypes, suggesting a founder effect from the establishment and spread of the parasite in this large country.

Phylogeography of Biomphalaria glabrata and B. pfeifferi, important intermediate hosts of Schistosoma mansoni in the New and Old World tropics

The historical phylogeography of the two most important intermediate host species of the human blood fluke Schistosoma mansoni, B. glabrata in the New World, and B. pfeifferi in the Old World, was investigated using partial 16S and ND1 sequences from the mitochondrial genome. Nuclear sequences of an actin intron and internal transcribed spacer (ITS)-1 were also obtained, but they were uninformative for the relationships among populations. Phylogenetic analyses based on mtDNA revealed six well-differentiated clades within B. glabrata: the Greater Antilles, Venezuela and the Lesser Antilles, and four geographically overlapping Brazilian clades. Application of a Biomphalaria-specific mutation rate gives an estimate of the early Pleistocene for their divergence. The Brazilian clades were inferred to be the result of fragmentation, due possibly to climate oscillations, with subsequent range expansion producing the overlapping ranges. Within the Venezuela and Lesser Antilles clade, lineages from each of these areas were estimated to have separated approximately 740 000 years ago. Compared to B. glabrata, mitochondrial sequences of B. pfeifferi are about 4x lower in diversity, reflecting a much younger age for the species, with the most recent common ancestor of all haplotypes estimated to have existed 880 000 years ago. The oldest B. pfeifferi haplotypes occurred in southern Africa, suggesting it may have been a refugium during dry periods. A recent range expansion was inferred for eastern Africa less than 100 000 years ago. Several putative species and subspecies, B. arabica, B. gaudi, B. rhodesiensis and B. stanleyi, are shown to be undifferentiated from other B. pfeifferi populations.

The parasitic trematode Fasciola hepatica exhibits mammalian-type glycolipids as well as Gal(beta1-6)Gal-terminating glycolipids that account for cestode serological cross-reactivity

Neutral glycosphingolipids from sheep-derived Fasciola hepatica liver flukes were isolated and characterized both structurally and serologically. After HPLC fractionation, glycolipids were analyzed by linkage analysis, enzymatic cleavage, and MALDI-TOF as well as electrospray ionization mass spectrometry. Obtained results revealed the presence of two types of neutral glycolipids. The first group represented mammalian-type species comprising globo- and isoglobotriaosylceramides (Gal(alpha1-4)Gal(beta1-4)Glc(1-1)ceramide and Gal(alpha1-3)Gal(beta1-4)Glc(1-1)ceramide, respectively) as well as Forssman antigen (GalNAc(alpha1-3)GalNAc(beta1-3/4)Gal(alpha1-4/3)Gal(beta1-4)Glc(1-1)ceramide). Applying Helix pomatia agglutinin, recognizing terminal alpha-linked GalNAc, to cryosections of adult flukes, the latter glycolipid could be localized to the F. hepatica gut. As Forssman antigen from the parasite and sheep host led to identical MALDI-TOF MS profiles, this glycolipid might be acquired from the definitive host. As a second group, highly antigenic glycolipids were structurally characterized as Gal(beta1-6)Gal(beta1-4)Glc(1-1)ceramide, Gal(beta1-6)Gal(alpha1-3/4)Gal(beta1-4)Glc(1-1)ceramide and Gal(beta1-6)Gal(beta1-6)Gal(alpha1-3/4)Gal(beta1-4)Glc(1-1)ceramide, the latter two structures of which exhibited both isoglobo- or globo-series core structures. Terminal Gal(beta1-6)Gal1-motifs have previously been shown to represent antigenic epitopes of neogala-series glycosphingolipids from tape worms. Using human Echinococcus granulosus infection sera, Gal(beta1-6)Gal-terminating glycolipids could be allocated to the gut in adult liver fluke cryosections. Corresponding neogala-reactive antibodies in F. hepatica infection serum were detected by their binding to E. granulosus and Taenia crassiceps neogala-glycosphingolipids. These antibodies might contribute to the known serological cross-reactivity between F. hepatica and parasitic cestode infections.

Emergence of infections with Schistosoma mansoni in the Dhofar Governorate, Oman

Infections with Schistosoma mansoni were identified in an area of Dhofar (Oman), where this parasite had been virtually absent during recent years and was reported only very sporadically before 1992. In the present survey, performed late in 2001, between 1 and 13% of children (n=519) were found to excrete eggs (one Kato-Katz-smear) in four schools, from four different villages, but no infections were detected in additional five schools (n=281). Infections were light (<72 eggs/g of faeces) in 19 of the 36 children found infected. Serologic examination of sera (n=511) was done by ELISA (based on soluble worm antigen) and immunofluorescence tests (IFT, based on cryostat sections of adult S. mansoni). The prevalence according to serological tests was between 3 and 43% in the four schools with infected children. Positive test results were taken to reflect active infections, since false positive reactions could largely be excluded. According to ultrasound (US) examinations performed on 96 individuals (children and adults) from the four villages, livers were normal in all except three cases of mild pathology, which could be assigned to schistosomiasis mansoni (pattern C, ages 32-40 years). All data suggest that transmission of S. mansoni has been re-introduced only recently in Dhofar and that this emergence of schistosomiasis is limited to at most a few foci.

Ecological and molecular studies on emerging schistosomiasis mansoni in Dhofar Governorate, Sultanate of Oman

The recent detection of some cases of autochtonous schistosomiasis mansoni in Dhofar, Oman, prompted a search for the transmission sites. The five field surveys we conducted from November 2000 to February 2002 provided ecological data on schistosomiasis in Dhofar. Twenty-eight water bodies situated within 8-160 km from Salalah, the largest city of Dhofar and at altitudes of up to 900 m, were surveyed for freshwater snails. Biomphalaria arabica was found in 15 of them. Three sites (Tibraq, Siginitti and Arazat) had Schistosoma infected snails, the first snails shedding cercariae of this parasite ever collected in Oman. The parasite from Dhofar was analysed by Random Amplified Polymorphic DNA comparisons using 11 primers and 167 polymorphic fragments and had 87-88% similarity with Schistosoma mansoni from Guadeloupe, but only 37-38% similarity with S. rodhaini from Burundi. Thus, it is a strain of S. mansoni. During the November 2000 survey, the prosobranch snail Melanoides tuberculata was associated with B. arabica in 10 of the 13 B. arabica sites. Cercariae from other species of Digenea emerged from five of the B. arabica sites, including the three named above. This paper presents the first finding of S. mansoni in the Dhofar Governorate and represents an initial study of the biology of S. mansoni transmission. This parasite and its cycle need further biological and molecular characterization, and the clarification of its epidemiological status in Dhofar Governorate is an urgent task.

A novel GlcNAcalpha1-HPO3-6Gal(1-1)ceramide antigen and alkylated inositol-phosphoglycerolipids expressed by the liver fluke Fasciola hepatica

The acidic (glyco)lipids of the parasitic liver fluke Fasciola hepatica exhibited two different phosphate-containing species, designated AL-I and AL-II, which were analyzed by MALDI-TOF MS, ESI MS, NMR, methylation analysis, and combined GC-MS in conjunction with HF treatment. AL-I was structurally determined as 1-O-hexadecyl-sn-glycerol-3-phosphoinositol, an ether bond variant of lysophosphatidylinositol. The structure of AL-II was shown to be GlcNAcalpha1-HPO3-6Gal(1-1)ceramide. Ceramide analysis revealed as major components 2-hydroxyoctadecanoic acid [18:0(2-OH)] together with C18- and C20-phytosphingosines. AL-II was apparently highly antigenic and strongly recognized by both animal- and human-F. hepatica infection sera. Furthermore, inhibition ELISAs revealed that the unusual antigenic determinant GlcNAcalpha1-HPO3- phosphate might have a potential in the serodiagnosis of F. hepatica infections.

Effective control of hookworm infection in school children from Dhofar, Sultanate of Oman: a four-year experience with albendazole mass chemotherapy

After 4 years of mass chemotherapy with a single annual dose of albendazole 400 mg, health education and promotion of environmental health, the prevalence of Necator americanus in Wilayat Tagah, Dhofar, Oman was reduced from 40 to 1.3% and from 6 to 0%, respectively, among rural and urban school children. Stool samples with egg load >1000 egg/gm were reduced from 28 to 0% after the first year of intervention and maintained as such in subsequent years.

Usefulness of Kato-Katz and trichrome staining as diagnostic methods for parasitic infections in clinical laboratories

OBJECTIVES

To assess the efficacy of the Kato-Katz technique and to re-evaluate other routine procedures conducted in the Microbiology Clinical Laboratory at Sultan Qaboos University Hospital (SQUH) and to throw light on the prevalence of intestinal parasitic infections among a small group of food handlers in Muscat.

METHOD

Faecal samples collected from food handlers were examined using five parasitological techniques.

RESULTS

Out of 100 faecal samples, 53 were positive for one or more of 11 intestinal parasites. The Kato-Katz and trichrome stain methods were found superior to the other techniques in detecting helminthic and protozoan infections, respectively. The auramine stain was useful only in detecting Cryptosporidium parvum oocysts.

CONCLUSION

A combination of trichrome stain and Kato-Katz techniques for stool examination is sufficient and recommended for busy laboratories; auramine stain should be applied only to samples with suspected cryptosporidal infections.

Schistosomiasis in patients in the Sultanate of Oman

BACKGROUND

Following an intensive public health eradication program, the focus of schistosomiasis mansoni at Salalah in Southern Oman (the only focus of schistosomiasis in Oman), appeared to have been eradicated in 1994. Since the vector snails for Schistosoma mansoni (and also for S. haematobium) were widely endemic in freshwater springs at Salalah, and reintroduction of infection (or introduction in the case of S. haematobium) was possible, we undertook a prospective study in 1995 for schistosomiasis in patients at the Sultan Qaboos University Hospital (SQUH), and to obtain evidence of visits by these patients to Salalah.

PATIENTS AND METHODS

From May 1995 to May 2000, Omani and expatriate patients presenting at SQUH were evaluated for possible schistosomiasis (residence in an endemic region, suggestive clinical features) by a search for ova in stool, urine, or in tissue biopsies, or when ova were absent, by serodiagnosis. A retrospective survey of schistosomiasis patients diagnosed in SQUH from 1990 to April 1995 was also performed. Ministry of Health (MOH) data on reports of schistosomiasis (a notifiable disease) in Oman from 1991 to 2000, were obtained.

RESULTS

Thirty patients with schistosomiasis were identified, 10 retrospectively and 20 in the prospective study. Patients were aged 9 to 60 years, and 25 of them (10 Omanis, 14 Egyptians, 1 Sudanese) contracted the infection in Africa, while 5 Omanis became infected in Salalah (3 in 1999). Twelve patients had schistosomiasis mansoni, 6 had schistosomiasis haematobia, and in the rest, infection by both parasites was confirmed or possible. The most common presentation (23%) was hepatosplenic schistosomiasis with portal hypertension. No patient admitted to contaminating freshwater with excreta in Salalah. MOH data revealed 3 to 14 cases of schistosomiasis were reported annually between 1991 and 2000, and that all schistosomiasis cases reported from 1994 to 1998 originated from Africa.

CONCLUSION

Schistosomiasis remains an important health problem in Oman. Many doctors are unfamiliar with the clinical features and methods of diagnosis, thereby frequently causing delays in diagnosis. Because vector snails are endemic in Salalah, schistosomiasis patients must be detected and treated early. At infested freshwater sites at Salalah, mollusciciding should continue indefinitely, and notices should warn visitors not to contaminate the spring water.

The liver flukes Fasciola gigantica and Fasciola hepatica express the leucocyte cluster of differentiation marker CD77 (globotriaosylceramide) in their tegument

Glycosphingolipids from the parasitic liver flukes Fasciola gigantica and Fasciola hepatica were isolated and their carbohydrate moieties were structurally analysed by methylation analysis, exoglycosidase treatment, on-target exoglycosidase cleavage and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. For both liver fluke species, the ceramide monohexosides Gal1-ceramide and Glc1-ceramide were found in relative amounts of 1.0 to 0.1, respectively. From F. gigantica, the ceramide dihexoside was isolated in sufficient amounts to be structurally determined as lactosylceramide, Gal beta4-Glc1-ceramide, while for both liver fluke species the ceramide trihexoside was shown to be Gal alpha4Gal beta4-Glc1-ceramide, which is designated as either globotriaosylceramide, Pk-blood group antigen or CD77 leucocyte cluster of differentiation antigen. To our knowledge, this is the first report on the expression of globo-series glycosphingolipids in non-mammalian species. Ceramide analysis of ceramide monohexosides yielded as major components octadecanoic and 2-hydroxyoctadecanoic fatty acids together with C18- and C20-phytosphingosines. By the use of an anti-CD77 monoclonal antibody and the Escherichia coli Shiga toxin B1 subunit, globotriaosylceramide could be immunolocalised to the tegument of F. hepatica cryosections. The sharing of CD77 between liver flukes and their mammalian hosts fits in with the concept of molecular mimicry, which is closely parallel to the established imitation of host CD15 (Lewis X) displayed by the blood fluke Schistosoma mansoni.

Antibodies against rickettsia in humans and potential vector ticks from Dhofar, Oman

OBJECTIVE

To determine the extent of rickettsial infections prevalence of potential vector ticks in the rural population of Dhofar, Oman.

METHOD

Human sera (n = 347) were obtained from six rural localities (school children, farmers, outpatients) in Dhofar, Sultanate of Oman. Sera were tested by immunofluorescence for the presence of antibodies reacting with Rickettsia conorii antigen.

RESULTS

More than half the samples (59%) gave positive reactions (titres of at least 1:64). Ticks (n=707) were collected from cattle, camels and goats (n=102) and included Amblyomma variegatum, Hyalomma a. anatolicum, H. dromedarii, H. rufipes and Rhipicephalus spp., all of which can potentially transmit rickettsiae to humans.

CONCLUSION

The results suggest that rickettsial infections are common among the rural population of Dhofar.

The seroprevalence of cystic hydatidosis in Oman

The presence of antibodies against Echinococcus granulosus in sera from 306 humans and 390 camels in Oman was investigated by indirect haemagglutination assays. Only one of the human and five of the camel sera gave positive reactions. The reactivities of the human sera were confirmed by ELISA. These results, together with isolated reports of hydatid cysts, indicate that E. granulosus is endemic in Oman, although with a low prevalence.

Circulating antigens in schistosomiasis: detection of 31/32-kDa proteins in sera from patients infected with Schistosoma japonicum, S. mansoni, S. haematobium, or S. intercalatum

A sandwich enzyme-linked immunosorbent assay (ELISA) was developed to detect 31/32-kDa schistosome proteins as circulating antigens in sera from schistosomiasis patients. A monoclonal antibody was used as a capture antibody and rabbit antiserum raised against purified 31/32-kDa proteins was the detecting antibody. Positive results were obtained with patients infected with Schistosoma japonicum (88%; n = 69), S. mansoni (80%; n = 56), S. haematobium (100%; n = 40), or S. intercalatum (94%; n = 65). Sera from uninfected Chinese and African individuals and from Chinese patients with trichinosis, cysticercosis, or paragonimiasis did not react in the assay. This ELISA appears to be valuable in diagnosing infections by all major human schistosome species.

Schistosomiasis in the southern region of Oman: vector snails and serological identification of patients in several locations

The snail Biomphalaria arabica is apparently ubiquitous in the south of Oman (Dhofar province). Snails bred in the laboratory were susceptible to infection with miracidia of Schistosoma mansoni (Puerto Rican strain). The snail Bulinus wrighti, a potential intermediate host of S. haematobium, was found for the first time in Dhofar. Human sera from five localities had antibodies against adult worm antigens and in particular against Sm31/32. The prevalence of seropositive patients was 28% of 47 farm workers, 12% of 99 out-patients from a clinic and 1% of 389 children from four localities. Autochthonous transmission of schistosomiasis in Dhofar is discussed.

Human brucellosis in Dhofar, Sultanate of Oman

Sera were collected, mostly from school children, in six localities of the southern region of the Sultanate of Oman. Macro and micro-agglutination tests were used to indicate positive Brucella serology. Four of the 525 sera tested had titres of at least 1:200, which were considered positive, and two had borderline values. The frequency of serologically positive sera in the six localities ranged between zero and 2%. No relevant difference was observed between titres using antigen of B. abortus or B. melitensis.

Reactivity of Schistosoma japonicum and S. mansoni antigen preparations in indirect haemagglutination (IHA) with sera of patients with homologous and heterologous schistosomiasis

Sera of patients infected with Schistosoma japonicum, S. mansoni or S. haematobium were tested in an indirect haemagglutination assay (IHA) using soluble S. japonicum egg antigen (SjSEA) and soluble S. mansoni adult antigen prepared either from a Puerto Rican strain (SmAWA) or an Egyptian strain (SmBW; Cellognost-Schistosomiasis Kit). Reactions were best, in terms of titres and sensitivity, in homologous systems. Heterologous systems were less reliable, particularly those using sera from urinary schistosomiasis patients. It is suggested that IHA is a suitable test to detect Schistosoma infections, especially when homologous systems are used.

Diagnostic Mr 31/32000 proteins of Schistosoma mansoni (Sm31/32) and S. haematobium (Sh31/32): stability and reaction conditions for prospective field tests

The existence of adult Schistosoma haematobium worm proteins (Sh31/32) homologous to the diagnostic Sm31/32 of S. mansoni is shown. Sm31/32 and Sh31/32, adsorbed on nitrocellulose and kept dry on the bench before immunoblot analysis, were antigenically stable for at least 4 years including storage for 17 months in tropical climates. The antigens react with patient sera in the absence of defined buffers under rather simple conditions ("humid chamber blot"). The results add to the use of these antigens for serodiagnosis of schistosomiasis in endemic areas.

The regulation of resistance to Schistosoma mansoni by auto-anti-idiotypic immunity

These studies explore auto-anti-idiotypic mechanisms as potential regulators of the protective immune response against Schistosoma mansoni. Anti-idiotypic responses were stimulated by immunization of mice with lymphoblasts, bearing specific idiotypic receptors. These receptors were produced in vitro by stimulation of Ag-reactive T cells by soluble cercarial immunogen, keyhole limpet hemocyanin, or Con A. The animals were then exposed to irradiated cercariae, keyhole limpet hemocyanin, or SRBC. The results indicate that the soluble cercarial immunogen lymphoblast recipient mice demonstrated reduction in a number of parameters of their immune response to schistosome Ag, including resistance to challenge by parasites. These changes were immunologically specific. Anti-idiotypic antibodies and anti-clonotypic T cell reactivity was demonstrated in the lymphoblast immunized mice. The suppression of reactivity in LBM was mediated by Lyt-1-, L3T-4-, and Lyt-2+ lymphocytes. These studies suggest that idiotypically dependent pathways might be important for the regulation of resistance to schistosomiasis.

The regulation of resistance to Schistosoma mansoni by auto-anti-idiotypic immunity

These studies explore auto-anti-idiotypic mechanisms as potential regulators of the protective immune response against Schistosoma mansoni. Anti-idiotypic responses were stimulated by immunization of mice with lymphoblasts, bearing specific idiotypic receptors. These receptors were produced in vitro by stimulation of Ag-reactive T cells by soluble cercarial immunogen, keyhole limpet hemocyanin, or Con A. The animals were then exposed to irradiated cercariae, keyhole limpet hemocyanin, or SRBC. The results indicate that the soluble cercarial immunogen lymphoblast recipient mice demonstrated reduction in a number of parameters of their immune response to schistosome Ag, including resistance to challenge by parasites. These changes were immunologically specific. Anti-idiotypic antibodies and anti-clonotypic T cell reactivity was demonstrated in the lymphoblast immunized mice. The suppression of reactivity in LBM was mediated by Lyt-1-, L3T-4-, and Lyt-2+ lymphocytes. These studies suggest that idiotypically dependent pathways might be important for the regulation of resistance to schistosomiasis.

Diagnostic Mr31/32,000 Schistosoma mansoni proteins (Sm31/32): reaction with sera from Sudanese patients infected with S. mansoni or S. haematobium

Sera of Sudanese patients with active infections of Schistosoma mansoni or S. haematobium were tested in immunoblots for their reactivity with Mr31/32,000 proteins of adult S. mansoni (Sm31/32). All sera from patients with intestinal (n = 123) and all but one from those with urinary schistosomiasis (n = 35) had antibodies against Sm31/32. These and additional data suggest that both specificity and sensitivity of Sm31/32 to detect schistosome infections are close to 100%. Antibodies against these proteins developed also in monkeys after experimental infection with S. haematobium. Sm31/32 antigens reacted in immunoblots as a doublet with most S. haematobium-patient sera and as a broad band with many S. mansoni-sera suggesting that at least two components are present in the molecular weight region of Mr31/32,000. The data demonstrate the potential use of Sm31/32 from adult worms to diagnose patients with intestinal or urinary schistosomiasis in endemic areas.