Angiostrongylus cantonensis is a zoonotic parasite that causes eosinophilic meningitis in humans. Earlier work on its mitochondrial genome was based on long polymerase chain reaction method. To date, only the mitogenome of the isolates from China has been studied. We report here the complete mitogenome of the Thailand isolate based on next generation sequencing and compare the genetic diversity with other isolates. The mitogenome of the Thailand isolate (13,519bp) is longer than those of the China isolates (13,497-13,502bp). Five protein-coding genes (atp6, cox1, cox2, cob, nad2) show variations in length among the isolates. The stop codon of the Thailand isolate differs from the China and Taiwan isolates in 4 genes (atp6, cob, nad2, nad6). Additionally, the Thailand isolate has 4 incomplete T stop codon compared to 3 in the China and Taiwan isolates. The control region is longer in the Thailand isolate (258bp) than the China (230-236bp) and Taiwan (237bp) isolates. The intergenic sequence between nad4 and cox1 genes in the Thailand isolate lacks 2bp (indels) at the 5'-end of the sequence as well as differs at 7 other sites compared to the China and Taiwan isolates. In the Thailand isolate, 18 tRNAs lack the entire TΨC-arm, compared to 17 in the China isolate and 16 in the Taiwan isolate. Phylogenetic analyses based on 36 mt-genes, 12 PCGs, 2 rRNA genes, 22 tRNA genes and control region all indicate closer genetic affinity between the China and Taiwan isolates compared to the Thailand isolate. Based on 36 mt-genes, the inter-isolate genetic distance varies from p=3.2% between China and Taiwan isolates to p=11.6% between Thailand and China isolates. The mitogenome will be useful for population, phylogenetics and phylogeography studies.
Angiostrongylus malaysiensis is a nematode parasite of various rat species. When first documented in Malaysia, it was referred to as A. cantonensis. Unlike A. cantonensis, the complete mitochondrial genome of A. malaysiensis has not been documented. We report here its complete mitogenome, its differentiation from A. cantonensis, and the phylogenetic relationships with its congeners and other Metastrongyloid taxa. The whole mitogenome of A. malaysiensis had a total length of 13,516bp, comprising 36 genes (12 PCGs, 2 rRNA and 22 tRNA genes) and a control region. It is longer than that of A. cantonensis (13,509bp). Its control region had a long poly T-stretch of 12bp which was not present in A. cantonensis. A. malaysiensis and A. cantonensis had identical start codon for the 12 PCGs, but four PCGs (atp6, cob, nad2, nad6) had different stop codon. The cloverleaf structure for the 22 tRNAs was similar in A. malaysiensis and A. cantonensis except the TΨC-arm was absent in trnV for A. malaysiensis but present in A. cantonensis. The Angiostrongylus genus was monophyletic, with A. malaysiensis and A. cantonensis forming a distinct lineage from that of A. costaricensis and A. vasorum. The genetic distance between A. malaysiensis and A. cantonensis was p=11.9% based on 12 PCGs, p=9.5% based on 2 rRNA genes, and p=11.6% based on 14 mt-genes. The mitogenome will prove useful for studies on phylogenetics and systematics of Angiostrongylus lungworms and other Metastrongyloid nematodes.
Angiostrongylus cantonensis is a bursate nematode parasite that causes eosinophilic meningitis (or meningoencephalitis) in humans in many parts of the world. The genomic data from A. cantonensis will form a useful resource for comparative genomic and chemogenomic studies to aid the development of diagnostics and therapeutics. We have sequenced, assembled and annotated the genome of A. cantonensis. The genome size is estimated to be ∼260 Mb, with 17,280 genomic scaffolds, 91X coverage, 81.45% for complete and 93.95% for partial score based on CEGMA analysis of genome completeness. The number of predicted genes of ≥300 bp was 17,482. A total of 7737 predicted protein-coding genes of ≥50 amino acids were identified in the assembled genome. Among the proteins of known function, kinases are the most abundant followed by transferases. The draft genome contains 34 excretory-secretory proteins (ES), a minimum of 44 Nematode Astacin (NAS) metalloproteases, 12 Homeobox (HOX) genes, and 30 neurotransmitters. The assembled genome size (260 Mb) is larger than those of Pristionchus pacificus, Caenorhabditis elegans, Necator americanus, Caenorhabditis briggsae, Trichinella spiralis, Brugia malayi and Loa loa, but smaller than Haemonchus contortus and Ascaris suum. The repeat content (25%) is similar to H. contortus. The GC content (41.17%) is lower compared to P. pacificus (42.7%) and H. contortus (43.1%) but higher compared to C. briggsae (37.69%), A. suum (37.9%) and N. americanus (40.2%) while the scaffold N50 is 42,191. This draft genome will facilitate the understanding of many unresolved issues on the parasite and the disorder it causes.
Angiostrongylus cantonensis is an important emerging zoonotic parasite causing human eosinophilic meningitis (or meningoencephalitis) in many parts of the world. To-date there is only a single study using mitochondrial cytochrome b (CYTB) gene to determine its genetic structure in eight geographical localities in Thailand. The present study examined the molecular phylogeography of this rat lungworm and its phylogenetic relationship with congeners using CYTB gene marker. A total of 15 CYTB haplotypes was found in 37 sequences from 14 geographical localities (covering north, west, east, central and south regions) in Thailand. These CYTB haplotypes were distinct from those of A. cantonensis for China and Hawaii. In Thailand, some CYTB haplotypes appeared to be confined to specific geographical localities. The partial CYTB DNA nucleotide sequences separated unequivocally the A. cantonensis isolates of Thailand, China and Hawaii as well as the congeners Angiostrongylus malaysiensis, A. costaricensis and Angiostrongylus vasorum, with A. malaysiensis grouped with A. cantonensis and A. costaricensis grouped with A. vasorum. Likewise the congeners of Metastrongylus and Onchocerca genera could also be clearly differentiated. The present study added two new definitive hosts (Bandicota savilei and Rattus losea) and three new localities (Mae Hong Son in the north, Tak in the west, and Phang Nga in the south) for A. malaysiensis in Thailand, indicating its wide occurrence in the country. Three CYTB haplotypes were found in the Thailand samples of A. malaysiensis. In addition to differentiation of congeners, CYTB gene marker could be used for determining the genetic diversity of a given population/taxon.