Molecular and pathological studies on Angiostrongylus species in southeast Queensland

Abstract

Despite an apparent increase in cases of angiostrongyliasis in humans and animals in Australia, the epidemiology of infection with the two species of Angiostrongylus that co-exist in this country, namely A. cantonensis and A. mackerrasae, is poorly understood. This knowledge gap is particularly important with respect to Angiostrongylus mackerrasae, a species evidently native to Australia, as its ability to cause disease in humans is unknown.Likewise, there is little information on the roles of native and introduced species of rodents and molluscs as hosts of Angiostrongylus species in Australia. This thesis focuses on the gaps in the knowledge about the epidemiology of two species in southeast Queensland, highlighting the hotspots for transmission of the parasite in urban Brisbane. A comprehensive survey of rats belonging to the species Rattus rattus, Rattus norvegicus and Rattus fuscipes was conducted. The prevalence of infection with Angiostrongylus spp. was 16.5% in Rattus spp. trapped in urban Brisbane and surrounds which is much higher than estimates of earlier studies. This highlights the possible risk of zoonotic infection in children, dogs and wildlife in this region and indicates the necessity for public awareness as well as more detailed epidemiological studies on this parasite in eastern Australia.Of the two Australian species, Angiostrongylus mackerrasae appears to be adapted to life in the native bush rat, Rattus fuscipes. This species evidently has an identical life cycle to that of Angiostrongylus cantonensis. A. mackerrasae may have greater potential to infect non-rodent hosts as it has been found as adult form in the lungs, as has been recorded for an individual flying fox.This raises concerns as to the potential of this native angiostrongylid to infect domestic animals and humans. To date, data on the taxonomy, epidemiology and population genetics of A. mackerrasae are poor or unknown. Here, we describe the mitochondrial (mt) genome of A. mackerrasae with the aim of addressing some of these knowledge gaps.The complete mitochondrial (mt) genome of A. mackerrasae was amplified from a single morphologically identified adult worm, by long-PCR in two overlapping amplicons (8 kb and 10 kb). The amplicons were sequenced using the MiSeq Illumina platform and annotated using an in-house pipeline. Amino acid sequences inferred from individual protein coding genes of the mt genomes were concatenated and then subjected to phylogenetic analysis using Bayesian inference.The mt genome of A. mackerrasae is 13,640 bp in size and contains 12 protein coding genes (cox1-3, nad1-6, nad4L, atp6 and cob), and two ribosomal RNA (rRNA) and 22 transfer RNA (tRNA) genes. The mt genome of A. mackerrasae has similar characteristics to those of other Angiostrongylus species which is explained in detail in chapter 3. Phylogenic comparisons reveal III that A. mackerrasae is closely related to A. cantonensis and the two sibling species may have recently diverged compared with all other species in the genus with a highl...

Hurdles in the evolutionary epidemiology of Angiostrongylus cantonensis: Pseudogenes, incongruence between taxonomy and DNA sequence variants, and cryptic lineages

“…Available in GenBank, there are five mitochondrial genomes identified as either A. cantonensis (NC_013065 = GQ398121, Lv et al, 2012;AP017672, BioProject: PRJEB493;KT186242, Yong, Song, et al, 2015;KT947978, Yong et al, 2016) or A. malaysiensis (KT947979 = NC_030332; Yong et al, 2016). A whole mtDNA genome identified as A. mackerrasae was discussed in Aghazadeh et al (2015), but where the actual sequence was obtained from the appendix of the thesis by Aghazadeh (2015). We refer to these six samples as the mtDNA genome reference samples.…”

“…Recently Song, Yong, and Eamsobhana (2017) compared the whole mtDNA of A. mackerrasae (Aghazadeh, 2015) to KT947978…”

Angiostrongylus mackerrasae and A. cantonensis (Nematoda: Metastrongyloidea) belong to same genetic lineage: evidence from mitochondrial protein-coding genes

“…A recent study indicates that A. mackerrasae and A. cantonensis are almost identical at two genetic loci (the nuclear internal transcribed spacer (ITS)-1 and 18S rRNA genes), indicating that these two taxa are conspecific (Chan et al , 2015). Another study, based on restriction enzymes for the cox3 region, failed to distinguish A. mackerrasae from A. cantonensis (Aghazadeh, 2015). Based on the amino acid sequence of the 12 mitochondrial PCGs, the genetic distance between A. mackerrasae and A. cantonensis is p = 2.4% (Aghazadeh et al , 2015), indicating that these two taxa are genetically very similar.…”

“…The complete mitochondrial genome of A cantonensis (KT947978 from Thailand; NC_013065 from China) and A. malaysiensis (NC_030332 from Malaysia) were downloaded from GenBank (National Center for Biotechnology Information, NCBI). The nucleotide sequences of the 12 protein-coding genes (PCGs) of A. mackerrasae from Australia were from Aghazadeh (2015). Other mitogenomes of Angiostrongylus available in NCBI's GenBank were included for comparison – A. costaricensis Costa Rica (KR827449), A. costaricensis Brazil (NC_013067) and A. vasorum (NC_018602).…”

“…As for A. malaysiensis , A. mackerrasae , when first documented in Australia, was referred to as A. cantonensis (Mackerras & Sandars, 1954, 1955). Recent studies based on molecular markers indicate that it is highly similar to A. cantonensis (Aghazadeh, 2015; Aghazadeh et al , 2015; Chan et al , 2015). These studies did not include A. malaysiensis , another member of the A. cantonensis species complex, for comparison.…”