Low Sensitivity of the Formol-Ethyl Acetate Sedimentation Concentration Technique in Low-Intensity Schistosoma japonicum Infections

Schistosoma japonicum is parasitic fluke (worm) found in China, Indonesia and the Philippines. A lot of effort has been put into combating the parasite, and the result has been a large drop in the number of infected people over the last decades. The average infected person also now has few worms, and hence excretes few eggs in stool. This has made it increasingly difficult to get a correct diagnosis by the diagnostic tests traditionally used. Tests based on detecting eggs in stool can be false-negative and tests detecting antibodies can be false-positive due to persisting antibodies or antibodies from other worm infections. Hence there is a need for new diagnostic strategies. Formol-ethyl acetate sedimentation concentration is a technique for detecting eggs in stool by microscopy, but has not to our knowledge been evaluated for S. japonicum. We compared the technique, using a single stool sample and a commercial preparation kit, with three tests traditionally used in the endemic countries (Kato-Katz thick smear, hatching test and indirect hemagglutination antibody detection). The sedimentation technique detected disappointing few positives and seems not to be an advantage in the diagnosis of low-intensity S. japonicum infection, compared to the traditionally used tests

Interaction between Salmonella and Schistosomiasis: A Review.

The interaction between schistosomiasis and Salmonella is a particularly important issue in Africa, where dual infection by the parasite and the bacterium are likely common. In this review, the ways in which schistosomiasis affects human biology as it relates to Salmonella are described. Those who are infected by both organisms experience reduced immunological functioning, exhibit irreversible organ damage due to prolonged schistosomiasis infection, and become latent carriers of Salmonella enterica serotypes Typhi and Paratyphi and S. Typhimurium. The sequestration of the bacteria in the parasite leads to ineffective antibiotic treatment because the bacteria cannot be completely killed, and lingering infection may then lead to antimicrobial resistance. These manifestations are likely not just for those dually infected but also for those first infected with schistosomes and, later, Salmonella. More data are needed to better understand dual infection, particularly as it may impact treatment and prevention of schistosomiasis and Salmonella in sub-Saharan Africa

Multilocus sequence typing (MLST) for lineage assignment and high resolution diversity studies in Trypanosoma cruzi.

BACKGROUND: Multilocus sequence typing (MLST) is a powerful and highly discriminatory method for analysing pathogen population structure and epidemiology. Trypanosoma cruzi, the protozoan agent of American trypanosomiasis (Chagas disease), has remarkable genetic and ecological diversity. A standardised MLST protocol that is suitable for assignment of T. cruzi isolates to genetic lineage and for higher resolution diversity studies has not been developed. METHODOLOGY/PRINCIPAL FINDINGS: We have sequenced and diplotyped nine single copy housekeeping genes and assessed their value as part of a systematic MLST scheme for T. cruzi. A minimum panel of four MLST targets (Met-III, RB19, TcGPXII, and DHFR-TS) was shown to provide unambiguous assignment of isolates to the six known T. cruzi lineages (Discrete Typing Units, DTUs TcI-TcVI). In addition, we recommend six MLST targets (Met-II, Met-III, RB19, TcMPX, DHFR-TS, and TR) for more in depth diversity studies on the basis that diploid sequence typing (DST) with this expanded panel distinguished 38 out of 39 reference isolates. Phylogenetic analysis implies a subdivision between North and South American TcIV isolates. Single Nucleotide Polymorphism (SNP) data revealed high levels of heterozygosity among DTUs TcI, TcIII, TcIV and, for three targets, putative corresponding homozygous and heterozygous loci within DTUs TcI and TcIII. Furthermore, individual gene trees gave incongruent topologies at inter- and intra-DTU levels, inconsistent with a model of strict clonality. CONCLUSIONS/SIGNIFICANCE: We demonstrate the value of systematic MLST diplotyping for describing inter-DTU relationships and for higher resolution diversity studies of T. cruzi, including presence of recombination events. The high levels of heterozygosity will facilitate future population genetics analysis based on MLST haplotypes