Experimental transmission of Babesia microti by Rhipicephalus haemaphysaloides.
BACKGROUND
Human babesiosis is considered an emerging threat in China. Dozens of human infections with Babesia microti have been reported recently, especially in southern China. However, the transmission vectors of this parasite in these areas are not well understood. Rhipicephalus haemaphysaloides, which is one of the dominant tick species in southern China, is a major vector of bovine babesiosis in China. However, whether this tick has the potential to transmit B. microti has not been tested. The present study experimentally investigated the transmission competence of B. microti through R. haemaphysaloides ticks.


METHODS
Larvae and nymphs of R. haemaphysaloides ticks were fed on laboratory mice infected by B. microti. The infection was detected by PCR at 4 weeks post-molting. BALB/c and NOD/SCID mice were infested by nymphs molting from larvae that ingested the blood of infective mice, and blood samples were then analyzed by PCR.


RESULTS
Experimental transstadial transmission of R. haemaphysaloides for B. microti was proved in both the larvae to nymph and the nymph to adult transstadial routes. The positive rate of B. microti was 43.8% in nymphs developed from larvae consumed infected mice and 96.7% in adults developed from nymphs exposed to positive mice. Among the mice infested by infective nymphs, B. microti was detected in 16.7% (2/12) of the BALB/c mice and in all of the NOD/SCID (6/6). However, the parasite was not observed to persist beyond more than one molt, and transovarial transmission did not occur.


CONCLUSIONS
This is the first study to demonstrate that B. microti can be transmitted artificially by R. haemaphysaloides. This tick species might be a potential vector of human babesiosis in southern China, which represents a public health concern.
Key Laboratory of Parasite & Vector Biology, Ministry of Health, National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, WHO Collaborating Centre for Malaria, Schistosomiasis and Filariasis, Shanghai, 200025, People's Republic of China.|School of Publish Health and Management, Weifang Medical University, Weifang, 261053, PR China.
Lan-Hua
LH
Li
Key Laboratory of Parasite & Vector Biology, Ministry of Health, National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, WHO Collaborating Centre for Malaria, Schistosomiasis and Filariasis, Shanghai, 200025, People's Republic of China.
Dan
D
Zhu
Key Laboratory of Parasite & Vector Biology, Ministry of Health, National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, WHO Collaborating Centre for Malaria, Schistosomiasis and Filariasis, Shanghai, 200025, People's Republic of China.
Chen-Chen
CC
Zhang
Key Laboratory of Parasite & Vector Biology, Ministry of Health, National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, WHO Collaborating Centre for Malaria, Schistosomiasis and Filariasis, Shanghai, 200025, People's Republic of China. zhang1972003@163.com.
Yi
Y
Zhang
Key Laboratory of Parasite & Vector Biology, Ministry of Health, National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, WHO Collaborating Centre for Malaria, Schistosomiasis and Filariasis, Shanghai, 200025, People's Republic of China. ipdzhouxn@sh163.net.
Xiao-Nong
XN
Zhou
D000818:Animals; D001096:Arachnid Vectors / Q000469:parasitology; D041702:BALB 3T3 Cells; D041001:Babesia microti / Q000502:physiology*; D001404:Babesiosis / Q000469:parasitology / Q000635:transmission*; D005260:Female; D007814:Larva; D051379:Mice; D016513:Mice, SCID; D009758:Nymph; D048494:Rhipicephalus / Q000469:parasitology*; D013047:Specific Pathogen-Free Organisms
Babesia microti; Rhipicephalus haemaphysaloides; Transmission; Vector competence