Molecular Detection Of Toxoplasma Gondii In Ticks

Toxoplasma gondii is a protozoan parasite,causing a common zoonosis as toxoplasmosis.According to epidemiological surveys,it is generally believed that only warm-blooded animals are infected with T.gondii.However,epidemiological investigations have suggested that herbivores and birds that are far removed from fecal contamination also have high infection rates.Previous laboratory studies have shown that vector arthropods can be used as a host for the preservation of T.gondii in nature.In order to fully understand the situation of carcasses infection with T.gondii under natural conditions,molecular detection of T.gondii was carried out from different locations,different host sources and different types of carcasses,and the T.gondii gene was typed in positive samples.The conclusions of this investigation are reported below:(1)In this study,1275 samples of ticks’ DNA were detected by real-time PCR.A total of 88 positive samples were found to be positive for T.gondii,with a positive rate of 6.90%.The total number of blood-sucking ticks tested was 848 among which the number of positive samples was 55 and the positive rate was 6.49%;the total number of non-sucking blood ticks tested was 427 while the number of positive samples was 33,and the positive rate was 7.73%.(2)In the blood-sucking ticks,the positive rate of adult ticks infection is 7.69%,the positive rate of nymph infection rate is 1.90%;the positive rate of larvae infection is 0;in the non-sucking ticks,the positive rate of adults infection is 7.96%,the positive rate of nymph infection is 0;the positive rate of larva infection is 14.29%.(3)The difference in the positive rate of different species of fleas is not significantly different.In the blood-sucking ticks,the positive rate of Haemaphysalis Iongicornis was 8.05%;the positive rate of Rhipicephalus sanguineus was 7.50%;the positive rate of Rhipicephalus haemaphysaloides was 12.12%;the positive rate of Boophilus microplus was 0;the positive rate of Dermacentor nuttalli was 10%;the positive rate of Haemaphysalis flava was 3.07%;the positive rate of Haemaphysalis was 20%;the positive rate of Rhipicephalus was 5.22%and the positive rate of unidentified tick species was 0.In the non-sucking blood ticks,the positive rate of Haemaphysalis Iongicornis was 7.67%;the positive rate of Rhipicephalus sanguineus was 8.7%;the positive rate of Rhipicephalus haemaphysaloides was 8.33%;the positive rate of Rhipicephalus was 6.25%.(4)All the positive samples carrying T.gondii were detected by quantitative PCR followed by nested PCR.The target bands were successfully amplified followed by gel electrophoresis and DNA sequencing.Nucleotide sequences from GenBank were aligned and the degree of similarity to the 529-bp repeat fragment of T.gondii was as high as 99%or more.(5)Nested PCR was used to genotype all positive samples.The results showed that all positive samples were T.gondii ME49 strains,belonging to T.gondii type II attenuated strain.(6)A phylogenetic tree was constructed for the positive blood-sucking ticks samples and positive non-sucking ticks samples.In addition,a Chi-square test was performed to analyze the data for significant differences.The difference between blood-sucking ticks and non-sucking ticks was found to be not significant.In summary,in this study we found that natural ticks are more common to carry T.gondii and the overall positive rate of infection is 6.90%.Among the six tested species of hard ticks,all five species ticks are infected,and there is no significant difference in the positive rates among different species of ticks.In the three developmental stages of ticks,the infection rate of adult ticks is higher than those of other development stages,and the difference between blood-sucking ticks and non-blood sucking ticks was not significant.Genotyping results showed that all positive samples were of Toxoplasma type II.According to the results of the study,we conclude that the T.gondii carried in ticks is of great significance in understanding the epidemiology and spreading this pathogen.