Objectives

2

The genetic polymorphisms of

Toxocara canis

from different regions were analyzed to study the genetic differences and transmission patterns of the isolates and provide a basis for the traceability and precise prevention and control of disease.

Methods

2

T. canis

isolates from Loudi and Changsha in Hunan Province

and Tongren in Guizhou Province were collected. The sequences of mitochondrial

cox1

gene in

T. canis

were amplified with PCR and sequenced. The polymorphism of the gene sequences was analyzed with software including DNAStar

Dnasp5.0

and MEGA7.0.

Results

2

The sequences of

cox1

gene in 12

T. canis

isolates were 441 bp in length. 8 mutated sites and 6 haplotypes were identif

ied. The diversity of nucleotides and average difference in nucleotides was 0.006 62 and 2.894

respectively. The sequence similarity of nucleotide among the isolates ranged from 99.1% to 100.0%

with the highest similarity (96.7% to 99.6%) to known isolates and below 96% similarity to other ascaridoid nematodes including

Toxascaris leonina

and

Toxocara cati

. The results of phylogenetic tree showed that the 12 isolates were located in the same branch as

T. canis

isolates from different regions

far away from the branch containing

T. leonina

and

T. cati

.

Conclusions

2

The degree of variation in

T. canis

from Hunan province and Guizhou province is relatively low. Although the diversity of haplotype is present

the genetic diversity is low as well.