Characterization of Spanish Trichinella isolates by random amplified polymorphic DNA (RAPD)

Present status of trichinellosis - a neglected zoonosis in India

Trichinellosis is a meat-borne helminthic zoonosis, caused by different species of the genus Trichinella. The disease is cosmopolitan in distribution and affects around 10,000 people annually around the globe. Based on genetic, biochemical and biological variability, 9 valid species (T. britovi, T. murrelli, T. nativa, T. nelsoni, T. papuae, T. patagoniensis, T. pseudospiralis, T. spiralis and T. zimbabwensis) and 3 genotypes (Trichinella T6, T8 and T9) of the parasite have been recognized. These species infect around 100 mammalian species including domestic and wild pigs, horses, game animals and wild carnivores. The infection starts with consumption of raw or undercooked meat or meat products containing encysted muscle larvae of the parasite. Most of the infections or outbreaks have been associated with the consumption of meat or meat products of pigs, wild boars, horses, crocodiles, walruses and dogs. Trichinoscopy is used in the veterinary inspection of pork in slaughterhouses and meat-packing facilities in many countries. It is a rapid process, but low in sensitivity and fails to detect mild infection. The muscle digestion method using HCl-pepsin is more sensitive and thus preferred. Recent outbreak of trichinellosis in Uttarakhand state opened up issues related to rapid diagnosis and lack of consumer awareness regarding safe cooking habits of meat of pig origin. This status report is an attempt to compile the information on Trichinella spp. infection in animals and humans in India at one place to draw the attention of medical and veterinary personnels involved in disease investigation and active research on zoonotic diseases.

Molecular identification of three Trichinella isolates from Heilongjiang Province, People's Republic of China

DNAs of Trichinella dog isolate (HC), Trichinella swine isolate (HH) and Trichinella cat isolate (SW), obtained from Heilongjiang Province, were amplified by the fragments of 18S rDNA and ITS2. Two reference strains, Trichinella spiralis (ISS3) and Trichinella nativa (ISS10) were used for sequence comparison. Sequence and dendrogram analysis indicated that HC belonged to T. nativa and HH together with SW belonged to T. spiralis. This method permits rapid species identification of Trichinella isolates, although further evaluation is required before precisely identification.

Deep resequencing of Trichinella spiralis reveals previously un-described single nucleotide polymorphisms and intra-isolate variation within the mitochondrial genome

The phylogeny and historical dispersal of Trichinella spp. have been studied, in part, by sequencing portions of the mitochondrial genome. Such studies rely on two untested beliefs: that variation in a portion is representative of the entire mitochondrial genome, and that each isolate is characterized by only one mitochondrial haplotype. We have used next generation DNA sequencing technology to obtain the complete mitochondrial genome sequence from a second isolate of T. spiralis. By aligning it to the only previously sequenced genome, we sought to establish whether the exceptionally deep sequencing coverage provided by such an approach could detect regions of the genome which had been misassembled, or nucleotide positions which may vary within an isolate. The new data broadly confirm the gene order and sequence assembly for protein-coding regions. However, in the repetitive non-coding region, alignment to the previously published genome sequence proved difficult. Such discrepancies may represent true biological variation, but may rather result from methodological or algorithmic sources. Within the 13,902bp protein-coding region, 7 polymorphisms were identified. Six of these polymorphisms occurred within protein-coding genes and three alter an amino acid sequence, one occurred in a tRNA-Ile sequence, and four were found to vary within our isolate. Thus, comparing only two isolates of T. spiralis has enabled the discovery of previously unrecognized variation within the species. Characterizing diversity within and among the mitochondrial genomes of additional species of Trichinella would undoubtedly yield further insights into the diversification history of the genus. Our study affirms that next generation DNA sequencing technology can reliably characterize a complete mitochondrial genome.

Genetic diversity among isolates of Trichinella spiralis from the Province of Buenos Aires, Argentina

Random Amplified Polymorphic DNAs, (RAPDs) are used to study the occurrence of Trichinella britovi and T5 among domestic animals in the Province of Buenos Aires, Argentina and to assess the genetic diversity among isolates of T. spiralisfrom this area in a number of infected hosts. All the local isolates proved to be T. spiralis. Six of the eight primers used indicate that the Buenos Aires isolates are distinct from each other as they produce a considerable number of polymorphic bands. Our overall estimates are relatively higher than other intraspecific distances previously estimated within species of this genus and among T. spiralis isolates. Such high degrees of variability observed among local isolates and between isolates from Buenos Aires and Spain should be taken into account when defining isolates within this species, and considering differences in the epidemiology of T. spiralis.

Aplicación de la técnica PCR-RFLP en la identificación de nematodos implicados en la anisakiasis humana

BACKGROUND AND OBJECTIVE

We intended to develop a molecular test allowing a species-specific identification of the anisakid human parasite independently of its evolutive stage.

MATERIAL AND METHOD

Anisakid larvae were obtained from fish destined to human consumption. In the PCR-RFLP test, the DNA corresponding to the ITS-1, 5.8S rRNA gene, ITS-2 and approximately 70 of the 28S rRNA gene region was amplified and a positive control was included. Products were digested with the endonuclease Taq I and subsequently sequenced.

RESULTS

Different anisakids (Anisakis simplex/Hysterothylacium aduncum) yield different amplification (960 and 1,010 bp fragments) and restriction patterns, which were in accord with previously described patterns of the same parasites from others geographical regions.

CONCLUSIONS

The high sensitivity of the test and the absence of intraspecies variations confirms the utility of this assay in the identification of human parasites involved in human anisakiasis including larvae from resected biopsies.

Random amplified polymorphic DNA analysis of DNA extracted from Trichuris trichiura (Linnaeus, 1771) eggs and its prospective application to paleoparasitological studies

Random amplified polymorphic DNA analysis was applied to DNAs extracted from Trichuris trichiura eggs recovered from human fecal samples. Four out of 6 primers tested displayed 18 distinct and well defined polymorphic patterns, ranging from 650 to 3200 base pairs. These results, upon retrieval and DNA sequencing of some of these bands from agarose gels, might help in establishing. T. trichiura specific genetic markers, not available yet, and an important step to design primers to be used in molecular diagnosis approaches.

PCR-RFLP patterns of four isolates of Trichinella for rDNA ITS1 region

We have studied the genetic differences among four isolates of Trichinella including a new strain of Trichinella spiralis (ISS 623) recently found from a human case who took a badger in Korea. Because they have a different host origin and came from geographically separated regions, we supposed the genetic pattern of the isolates might be different as had been previously reported. It was analysed by PCR-RFLP analysis of the rDNA repeat that can readily distinguish a species or strain from others. Isolated genomic DNA of each isolate of Trichinella larvae was amplified with ITS1 specific primers and digested with restriction endonucleases. The PCR product of ITS1 was confirmed using Southern blot analysis to be a 910 bp fragment. The restriction fragments of each isolate had variable patterns when it was digested with Rsa 1 only. According to the RFLP patterns, the estimated genetic divergence between each isolate was different. In conclusion, four isolates of Trichinella including a new strain of T. spiralis obtained from a Korean patient may have genetic differences in the ITS1 region and the Shanghai isolate was genetically more similar to the Japanese unknown isolate than others in the ITS1 region.

Molecular and biochemical methods for parasite differentiation within the genus Trichinella

Delineation of the genus Trichinella into a more complex group of parasites has substantially motivated investigators to better identify and characterize the species and genotypes that form the basis of their investigations. Because of the cosmopolitan geographical distribution and broad host range that typify this genus, assigning unique biological, immunological and biochemical characters to each species and genotype has been essential for researchers to further advance this field. Numerous groups have developed simple methods to differentiate the genotypes, and by so doing, have generated diagnostic keys that accurately reflect the distinct differences among parasites of this group. Throughout the years, many methods have been used to accomplish this task, beginning with isoenzyme analyses and the use of repetitive DNA probes, to employing the polymerase chain reaction (PCR) and more state-of-the-art technologies. This review article summarizes the development of these methods with emphasis on molecular techniques and the ultimate goal of providing a simple, rapid and reproducible test to differentiate Trichinella parasites at the highest level of sensitivity, i.e. single parasite.