Establishment of a novel tick-Babesia experimental infection model.

Hiroki Maeda,M Abdul Alim,Makoto Matsubayashi,Takeshi Hatta,Daigo Tsubokawa,Takeharu Miyoshi,Rika Umemiya-Shirafuji,Masami Mochizuki,Shin-Ichiro Kawazu,Ikuo Igarashi,Fusako Mikami,Tetsuya Tanaka,Naotoshi Tsuji

doi:10.1038/srep37039

Abstract

Ticks are potent vectors of many deadly human and animal pathogens. Tick-borne babesiosis is a well-recognized malaria-like disease that occurs worldwide and recently has attracted increased attention as an emerging zoonosis. Although the proliferation of Babesia organisms is essential in the vectors, their detailed lifecycle with time information for migration in ticks remains unknown. A novel study model for the elucidation of the migration speed of Babesia parasites in their vector tick, Haemaphysalis longicornis, has been developed using an artificial feeding system with quantitative PCR method. The detectable DNA of Babesia parasites gradually disappeared in the tick midgut at 1 day post engorgement (DPE), and in contrary increased in other organs. The results indicated that the Babesia parasite passed the H. longicornis midgut within 24 hours post engorgement, migrated to the hemolymph, and then proliferated in the organs except the midgut. This time point may be an important curfew for Babesia parasites to migrate in the tick lumen. We also visualized the Babesia parasites in the experimentally infected ticks and in their eggs using IFAT for detecting their cytoskeletal structure, which suggested the successful tick infection and transovarial transmission of the parasite. This model will shed light on the further understanding of tick-Babesia interactions.

Highlights

Ticks are notorious hematophagous ectoparasites of almost terrestrial vertebrates and well known as a unique vector of various deadly diseases, such as Lyme borreliosis, tularemia, anaplasmosis, babesiosis, theileriosis, tick-borne encephalitis, and severe fever with thrombocytopenia syndrome (SFTS)[1,2]
It has been experimentally proved that transmission of B. ovata to cattle takes place by only the larval stage of H. longicornis[13] and it is considered that the larval stage of H. longicornis is the important stage for the transmission of babesiosis caused by B. ovata
We verified the sensitivity of the Quantitative PCR (qPCR) and confirmed the typical amplification curve, melting curve with no primerdimerization, and correlative standard curve using the artificially prepared meta-genomic DNA samples, including the plasmid DNA-carrying B. ovata β-tubulin fragment and tick genomic DNA (Supplementary Fig. 1)

Summary

Introduction

Ticks are notorious hematophagous ectoparasites of almost terrestrial vertebrates and well known as a unique vector of various deadly diseases, such as Lyme borreliosis, tularemia, anaplasmosis, babesiosis, theileriosis, tick-borne encephalitis, and severe fever with thrombocytopenia syndrome (SFTS)[1,2]. Babesiosis is caused by intraerythrocytic apicomplexan parasites which belong to the genus Babesia and is mainly transmitted by tick vectors to a variety of vertebrate hosts, including wild and domestic animals and humans[9,10]. We developed the quantification model for transovarially transmitted Babesia parasite in the vector ticks This system is quite simple and we could obtain synchronous engorged tick experimentally infected with Babesia pathogens within 12-24 hours of artificial feeding period. Through this model it was possible to monitor quantitatively the transovarial transmission of Babesia parasites. This model will give insight toward the development of new control strategies of babesiosis

Methods

Results

Conclusion