Molecular Identification and Phylogenetic Analysis of Ascarids in Wild Animals

The First Report of Sphaerirostris picae Infection in the Oriental Magpie (Pica serica) in Beijing, China

Background: Sphaerirostris picae is a parasitic species known for its ability to infect and transmit between hosts in the gastrointestinal tracts of wild avian species. However, there is limited information on its presence and impact on urban avian populations, particularly in China. Materials and Methods: In this study, morphological observations were conducted to detect the presence of Sphaerirostris sp. within the intestinal tract of the Oriental Magpie (Pica serica) collected in Beijing, China. Further confirmation of the parasite's identity was achieved through phylogenetic analysis using COX1 gene sequencing to compare with previously documented Sphaerirostris picae isolates. Results: The morphological and molecular analyses confirmed the presence of Sphaerirostris picae in the Oriental Magpie. Phylogenetic analysis indicated a close relationship with known Sphaerirostris picae isolates. This represents the first reported case of Sphaerirostris picae infection in magpies from Beijing, China. Conclusion: The findings highlight the potential health hazards posed by Sphaerirostris picae to urban avian populations and public health. The study suggests that additional research and surveillance efforts are necessary to better understand the risks associated with this parasite and to develop effective mitigation strategies.

First report of Hexametra angusticaecoides Chabaud & Brygoo, 1960 (Nematoda: Ascarididae) in a population of captive central bearded dragons, Pogona vitticeps Ahl (Squamata: Agamidae)

Between 2022 and 2023 ascaridoid nematodes of the genus Hexametra were recovered from two captive central bearded dragons (Pogona vitticeps Ahl) in the Extremadura region of Spain. These nematodes were identified by an integrative approach combining morpho-anatomical and molecular data. We used two rRNA regions (D2-D3 expansion segments of the 28S, and ITS fragments), and the partial region of the cytochrome oxidase I gene (COI mtDNA) sequences. Hexametra angusticaecoides Chabaud & Brygoo, 1960 (Ascarididae) was morphologically characterized and illustrated using light and scanning electron microscopy. Bayesian inference (BI) and Maximum Likelihood (ML) phylogenetic trees for these genetic markers established relationships that highlight the importance of using molecular and phylogenetic data for accurate species identification within the genus Hexametra. Phylogenetic trees indicated that the Spanish isolates of H. angusticaecoides were clustered in a well-supported clade together with other isolates from Central Europe of the same species. Molecular phylogenetic findings also reflect that there was a higher intraspecific variation for ITS genetic markers at the intraspecific level. Phylogenetic results based on 28S rRNA suggest that Ascarididea was divided into three monophyletic major clades. To our knowledge, this is the first report of this species parasitizing bearded dragons, extending the host range of this species. These findings represent the first formal record of H. angusticaecoides in Spain.

Characterisation of the mitochondrial genome and phylogenetic analysis of Toxocara apodemi (Nematoda: Ascarididae)

We first sequenced and characterised the complete mitochondrial genome of Toxocara apodeme, then studied the evolutionary relationship of the species within Toxocaridae. The complete mitochondrial genome was amplified using PCR with 14 specific primers. The mitogenome length was 14303 bp in size, including 12 PCGs (encoding 3,423 amino acids), 22 tRNAs, 2 rRNAs, and 2 NCRs, with 68.38% A+T contents. The mt genomes of T. apodemi had relatively compact structures with 11 intergenic spacers and 5 overlaps. Comparative analyses of the nucleotide sequences of complete mt genomes showed that T. apodemi had higher identities with T. canis than other congeners. A sliding window analysis of 12 PCGs among 5 Toxocara species indicated that nad4 had the highest sequence divergence, and cox1 was the least variable gene. Relative synonymous codon usage showed that UUG, ACU, CCU, CGU, and UCU most frequently occurred in the complete genomes of T. apodemi. The Ka/Ks ratio showed that all Toxocara mt genes were subject to purification selection. The largest genetic distance between T. apodemi and the other 4 congeneric species was found in nad2, and the smallest was found in cox2. Phylogenetic analyses based on the concatenated amino acid sequences of 12 PCGs demonstrated that T. apodemi formed a distinct branch and was always a sister taxon to other congeneric species. The present study determined the complete mt genome sequences of T. apodemi, which provide novel genetic markers for further studies of the taxonomy, population genetics, and systematics of the Toxocaridae nematodes.

Complete mitogenomes characterization and phylogenetic analyses of Ceratophyllus anisus and Leptopsylla segnis

Fleas are one of the most common ectoparasites in warm-blooded mammals and an important vector of zoonotic diseases with serious medical implications. We sequenced the complete mitochondrial genomes of Ceratophyllus anisus and Leptopsylla segnis for the first time using high-throughput sequencing and constructed phylogenetic relationships. We obtained double-stranded circular molecules of lengths 15,875 and 15,785 bp, respectively, consisting of 13 protein-coding genes, 22 transfer RNAs, 2 ribosomal RNAs, and two control regions. AT-skew was negative in both C. anisus (-0.022) and L. segnis (-0.231), while GC-skew was positive in both (0.024/0.248), which produced significant differences in codon usage and amino acid composition. Thirteen PCGs encoding 3,617 and 3,711 codons, respectively, isoleucine and phenylalanine were used most frequently. The tRNA genes all form a typical secondary structure. Construction of phylogenetic trees based on Bayesian inference (BI) and maximum likelihood (ML) methods for PCGs. The results of this study provide new information for the mitochondrial genome database of fleas and support further taxonomic studies and population genetics of fleas.