Analysis of genetic diversity and population structure of Babesia gibsoni

First Insight into the Phylogenetic Diversity of Bovicola caprae Infesting Goats of Different Agro-climatic Locations in India

Bovicola caprae is an important obligate ectoparasite of goats worldwide including India. The present study aimed at the molecular confirmation, phylogenetics and population structure analyses of B. caprae infesting goats of three different agro-climatic locations in India, by targeting the mitochondrial cytochrome C oxidase subunit 1 (cox1) genetic marker. The phylogenetic tree exhibited the presence of two different lineages of B. caprae. The sequences generated herein clustered in lineage 2 along with the GenBank™ archived sequences from China and Iran. The sequences generated herein also showed the circulation of sub-lineages of B. caprae in India based on the analysis of pairwise genetic distances between sequences and median-joining haplotype network. The population structure analyses revealed low nucleotide (0.00353 ± 0.00291 and 0.02694 ± 0.00363) and high haplotype (0.667 ± 0.314 and 0.618 ± 0.104) diversities for the present study isolates as well as for the complete dataset, respectively, which evinced a recent demographic expansion. High genetic differentiation (FST value = 0.97826) and low gene flow (Nm = 0.00556) were also recorded in the different lineages/populations. In conclusion, the present study addressed the research gap and provided the first insight into the phylogenetics of the goat louse B. caprae and highlighted the circulation of sub-lineages of the ectoparasite in India.

Population structure and haplotype network analyses of Hyalomma anatolicum based on the large subunit ribosomal RNA (16S rRNA) gene

Hyalomma anatolicum, an Anatolian hard tick is a well-recognized vector involved in the transmission of various pathogens to animals and humans. The present study elucidated the population structure and haplotype network of H. anatolicum based on the mitochondrial large subunit ribosomal RNA (16S rRNA) gene sequence. The population structure and haplotype network analysis of 75 sequences archived in the GenBank, including the 15 sequences generated herein, yielded 24 haplotypes. Haplotype 1 (Hap_1) was the predominant haplotype consisting of 45 sequences from India, China, Pakistan, Turkey, Egypt, Iraq, and Tajikistan. The complete haplotype network exhibited a stellate conformation, highlighting a recent population expansion. The overall dataset, together with the sequences corresponding to India, China, and Pakistan, showed a high haplotype (0.638 ± 0.065, 0.671 ± 0.103, 0.753 ± 0.099, and 0.854 ± 0.061, respectively) and low nucleotide (0.00407 ± 0.00090, 0.00525 ± 0.00196, 0.00680 ± 0.00233, and 0.00453 ± 0.00056, respectively) diversity, further emphasized a recent population expansion. The neutrality indices including Tajima's D, Fu and Li's D, and Fu and Li's F for the complete dataset (- 2.661, - 6.008, and - 5.649, respectively) as well as for the sequences from India (- 2.223, - 3.414, and - 3.567, respectively) were negative, suggesting deviation from neutrality and a recent population expansion. The present study provided novel insights into the population structure and haplotype networks of H. anatolicum based on the mitochondrial 16S rRNA gene, and the different tests inferred a low genetic differentiation and suggested a recent population expansion of this economically important tick species.

Analysis of Genetic Diversity of cytb gene from Babesia gibsoni Isolates from Naturally Infected Dogs in Karnataka, India

PURPOSE

The study aimed to investigate genetic diversity in Babesia gibsoni, the causative agent of canine babesiosis, and to assess the presence of atovaquone-resistant isolates in naturally infected dogs.

METHODS

A total of 24 blood samples confirmed for B. gibsoni infection was subjected to PCR amplification and sequencing based on cytb gene. Genetic characterization of B. gibsoni as well as attempts to detect the point mutation rendering atovaquone resistance was carried out based on the analysis of nucleotide sequence of cytb gene using bioinformatics software.

RESULTS

The findings indicated that the B. gibsoni isolates in the investigation exhibited a high nucleotide identity with the Asian genotype, ranging from 98.41 to 98.69%. Notably, none of the isolates carried cytb gene variants associated with atovaquone resistance. Phylogenetic analysis revealed clustering of most isolates with those from Japan and China, except for one isolate forming a distinct subclade. Haplotype network analysis indicated a high diversity with 22 distinct haplotypes among the B. gibsoni isolates, emphasizing the genetic variability within the studied population.

CONCLUSION

In conclusion, the cytb gene exhibited remarkable conservation among the twenty-four B. gibsoni isolates studied and the study represents the first genetic diversity assessment of B. gibsoni using the cytb gene in dogs from India. These findings shed light on the genetic characteristics of B. gibsoni in the region and provide valuable insight for addressing the challenges posed by this life-threatening disease in dogs.

Phylogeography and demographic dynamics of Rhipicephalus microplus from North India

Rhipicephalus microplus, a hematophagous vector prevalent in the tropics and subtropics, is responsible for huge economic losses throughout the globe. However, the taxonomy of the tick species, especially prevalent in north India and south China has been challenged in the recent past. The present study attempted to assess the cryptic status of R. microplus ticks of north India based on two mitochondrial markers; the 16S rRNA and cox1 gene sequences. The phylogenetic tree corresponding to both markers demonstrated the presence of three distinct genetic assemblages/ clades of R. microplus. The present study isolates (n = five and seven for the cox1 and 16S rRNA gene sequences, respectively) from north India along with other isolates from India assorted in the R. microplus clade C sensu. Based on the median joining network analysis corresponding to the 16S rRNA gene sequence, 18 haplotypes were recorded, exhibiting a stellate shape, which was indicative of rapid population expansion. For the cox1 gene, the haplotypes corresponding to clades A, B and C were distantly placed with two exceptions. While performing the population structure analysis, low nucleotide (0.04745 ± 0.00416 and 0.01021 ± 0.00146) and high haplotype diversities (0.913 ± 0.032 and 0.794 ± 0.058) were recorded for the different clades of R. microplus based on the cox1 and 16S rRNA mitochondrial markers, respectively. Eventually, high genetic differentiation and low gene flow were recorded among the different clades. A negative value for the neutrality indices (Tajima's D = -1.44125, Fu's Fs = -4.879, Fu and Li's D = -2.78031 and Fu and Li's F = -2.75229) corresponding to the 16S rRNA gene for the overall dataset evinced an expansion of population size. Based on the detailed studies, it was inferred that the R. microplus tick species circulating in north India belonged to clade C sensu, similar to that of the species prevalent in the other parts of the country as well as in the Indian subcontinent.