Lalani Yatawara

The complete mitochondrial genome of Setaria digitata (Nematoda: Filarioidea): Mitochondrial gene content, arrangement and composition compared with other nematodes

In the present study, we determined the complete mitochondrial (mt) genome sequence (13,839bp) of parasitic nematode Setaria digitata and its structure and organization compared with Onchocerca volvulus, Dirofilaria immitis and Brugia malayi. The mt genome of S. digitata is slightly larger than the mt genomes of other filarial nematodes. S. digitata mt genome contains 36 genes (12 protein-coding genes, 22 transfer RNAs and 2 ribosomal RNAs) that are typically found in metazoans. This genome contains a high A+T (75.1%) content and low G+C content (24.9%). The mt gene order for S. digitata is the same as those for O. volvulus, D. immitis and B. malayi but it is distinctly different from other nematodes compared. The start codons inferred in the mt genome of S. digitata are TTT, ATT, TTG, ATG, GTT and ATA. Interestingly, the initiation codon TTT is unique to S. digitata mt genome and four protein-coding genes use this codon as a translation initiation codon. Five protein-coding genes use TAG as a stop codon whereas three genes use TAA and four genes use T as a termination codon. Out of 64 possible codons, only 57 are used for mitochondrial protein-coding genes of S. digitata. T-rich codons such as TTT (18.9%), GTT (7.9%), TTG (7.8%), TAT (7%), ATT (5.7%), TCT (4.8%) and TTA (4.1%) are used more frequently. This pattern of codon usage reflects the strong bias for T in the mt genome of S. digitata. In conclusion, the present investigation provides new molecular data for future studies of the comparative mitochondrial genomics and systematic of parasitic nematodes of socio-economic importance.

Morphological and molecular characterization of Paragonimus westermani in northeastern India

Evidence for the presence of lung flukes of the Paragonimus westermani in India remains scant. In particular, evidence based on morphology of adult worms is lacking. Metacercariae of the genus Paragonimus, recovered from crabs in two regions of northeastern India, were raised to adulthood in laboratory rats. Morphologically, these worms appear to be P. westermani. DNA sequences from the second internal transcribed spacer (ITS2) and a portion of the ribosomal large subunit gene (28S) of the nuclear ribosomal RNA gene repeat, as well as fragments of the mitochondrial cytochrome c oxidase subunit 1 (cox1) and NADH dehydrogenase subunit 1 (nad1) genes, all supported this identification. Molecular phylogenetic methods were used for studying the relatedness of these Indian flukes with counterparts from southeast and far-east Asia. Molecular data showed that Indian representatives of the P. westermani complex represent a distinct lineage. It is unclear whether the Indian form can cause disease in humans as some members of the complex do elsewhere.

Toxocara vitulorum (Ascaridida: Nematoda): mitochondrial gene content, arrangement and composition compared with other Toxocara species.

Partial mitochondrial (mt) genome sequence (10,486bp) from the parasitic nematode Toxocara vitulorum was determined and its organization and structure compared with those of T. cati, T. canis and T. malaysiensis. The obtained mt genome sequence of T. vitulorum contains 10 protein-coding genes (cytochrome c oxidase subunits 1-3, Nicotinamide adenine dinucleotide dehydrogenase subunits 1-5, ATP synthase subunit 6 and cytochrome b), 14 transfer RNA genes and the large ribosomal RNA gene (rrnL), non-coding regions. ORF encoding for ATPase subunit 8 is not found in this partial mtDNA sequence. Five translation initiation codons were inferred, ATT, ATG, GTG, GTT and TTG. Most of the genes used TAG or TAA as a stop codon and two genes ended with a T. The gene arrangement and composition of the T. vitulorum mt genome is very similar to that of other Toxocara species mitochondrial genomes sequenced thus far. All genes are transcribed in the same direction, as other Toxocara species. This genome has a high A+T content (67.5%) and low G+C content (32.5%). Phylogenetic reconstruction based on aligned nucleotide sequences of seven taxa provided strong support that Toxocara vitulorum is more closely related to T. malaysiensis than to T. canis and T. cati.

Maxicircle (mitochondrial) genome sequence (partial) of Leishmania major: Gene content, arrangement and composition compared with Leishmania tarentolae

We report 8420 bp of DNA sequence data from the maxicircle (mitochondrial) genome of Leishmania major (MHOM/SU/73/5ASKH), a much larger portion of this genome than has been reported previously from any Leishmania species infecting humans. This region contains 10 partial and complete genes: 5 protein-encoding genes (COII, COIII, ND1, ND7 and Cyt b); two ribosomal RNA subunits (12S and 9S) and three unidentified open reading frames (MURF1, MURF4 (ATPase6) and MURF5), as in the lizard-infecting species L. tarentolae. The genes from L. major exhibit 85-87% identity with those of L. tarentolae at the nucleotide level and 71-94% identity at the amino acid level. Most differences between sequences from the two species are transversions. The gene order and arrangement within the maxicircle of L. major are similar to those in L. tarentolae, but base composition and codon usage differ between the species. Codons assigned for initiation for protein-coding genes available for comparison are similar in five genes in the two species. Pre-editing was identified in some of the protein-coding genes. Short intergenic non-coding regions are also present in L. major as they are in L. tarentolae. Intergenic regions between 9S rRNA and MURF5, MURF1 and ND1 genes are G+C rich and considered to be extensive RNA editing regions. The RNA editing process is likely to be conserved in similar pattern in L. major as in L. tarentolae.

Immunolocalization of arginine kinase (AK) in Toxocara canis, Toxocara vitulorum, and Ascaris lumbricoides

Arginine kinase (AK) is a member of the phosphagen kinase family. AK plays a major role in cellular energy metabolism in invertebrates including nematodes. In the present study, we performed the direct immunofluorescence test to determine the immunolocalization of AK in different stages of the life cycle (eggs, larvae, and adult worms) of Toxocara canis, Toxocara vitulorum, and Ascaris lumbricoides. Our results indicated variable levels of expression of AK in different stages. Moreover, strong fluorescence was observed in cleaving eggs than in dormant eggs. The highest activity of the enzyme was observed in the fully developed eggs. This may be due to high expression of AK in embryonic development, which is associated with increased energy demand due to cleavage and cellular differentiation. Surprisingly, expression of AK is significantly higher in the middle part and posterior end compared to anterior end of the larvae. In addition, AK is highly concentrated in cellular and metabolically active parts of the body such as hypodermis, muscle, intestine, ovaries, oviducts, and uterus, while it is absent in noncellular areas like cuticle. The present study revealed the presence of AK in T. canis, A. lumbricoides, and T. vitulorum and that it plays a major role in energy metabolism of these nematodes. Interestingly, antiserum was prepared against the recombinant T. canis AK and reacts with the native AKs of T. canis, A. lumbricoides, and T. vitulorum. AK levels could vary in relation to maximum potential rates of ATP turnover, oxidative capacity, and energy output. Further studies on subcellular localization of AK in these important helminths provide new information for researchers to develop effective anthelmintics against the parasites of veterinary and of public health importance.

Clinico-Epidemiological Patterns of Cutaneous Leishmaniasis Patients Attending the Anuradhapura Teaching Hospital, Sri Lanka

Cutaneous leishmaniasis (CL) caused by Leishmania donovani is an endemic vector-borne disease in Sri Lanka. Over 2,500 cases have been reported since 2000 and the number of CL cases has dramatically increased annually. Total 57 clinically suspected CL patients attending the dermatology clinic in Anuradhapura Teaching Hospital were recruited from January to June 2015. Slit skin smears and skin biopsies were taken from each of the subjects. Clinical and epidemiological data were obtained using interviewer administered questionnaire. Forty-three (75.4%) patients among 57 were confirmed positive for L. donovani. The majority of infected patients was males (P=0.005), and the most affected age group was 21–40 years. Soldiers in security forces, farmers, and housewives were identified as high risk groups. The presence of scrub jungles around the residence or places of occupation (P=0.003), the presence of sandflies (P=0.021), and working outsides more than 6 hr per day (P=0.001) were significantly associated with CL. The number of lesions ranged from 1–3, and the majority (76%) of the patients had a single lesion. Upper and lower extremities were the prominent places of lesions, while the wet type of lesions were more prevalent in females (P=0.022). A nodular-ulcerative type lesion was common in both sexes. The presence of sandflies, scrub jungles, and outdoor activities contributed to spread of Leishmania parasites in an endemic pattern. Implementation of vector control programs together with health education with regard to transmission and prevention of CL are necessary to control the spread of this infection.

The Sri Lankan twin registry: 2012 update

The Sri Lankan Twin Registry (SLTR), established in 1997, is a unique resource for twin and genetic research in a low- and middle-income country (LMIC). It comprises of a volunteer cohort of 14,120 twins (7,060 pairs) and 119 sets of triplets, and a population-based cohort of 19,040 (9,520 pairs) twins and 89 sets of triplets. Several studies have been conducted using this registry, including the Colombo Twin and Singleton Study (CoTaSS 1; 4,387 twins, 2,311 singletons), which have explored the prevalence and heritability of a range of psychiatric disorders as well as gene-environmental interplay. Currently, a follow-up study (CoTaSS 2) of the same cohort is underway, looking at the prevalence and interrelationship of key cardiovascular and metabolic risk markers (e.g., metabolic syndrome). A significant feature of CoTaSS 2 is the establishment of a biobank. Current SLTR work is extending beyond mental health and the interface between mental and physical health to new horizons, extending collaborations with the wider global twin research community. Ethics and governance have been given special emphasis in the initiative. Capacity building and public engagement are two crucial components. Establishment of a state-of-the-art genetic laboratory was a major accomplishment. SLTR is a classic showcase of successful North-South partnership in building a progressive research infrastructure in a LMIC.

The first intermediate host of Paragonimus westermani in Sri Lanka

Freshwater snails (family Paludomidae, genus Paludomus) were collected from streams in Hedeniya and Peradeniya (the campus of Peradeniya University), Kandy district, Central Province, Sri Lanka, and found to harbor rediae and cercariae of a Paragonimus sp. These larvae were identified as Paragonimus westermani by using ITS2 DNA sequences. The infection rates of P. westermani in Paludomus sp. in Hedeniya and Peradeniya were 0.1% (one of 1014) and 0.2% (two of 1006), respectively. The snail has not been identified to species in the present study. This is the first report of the snail host of Paragonimus in Sri Lanka.