sábado, 21 de marzo de 2015

Nairobi Sheep Disease Virus RNA in Ixodid Ticks, China, 2013 - Volume 21, Number 4—April 2015 - Emerging Infectious Disease journal - CDC

Nairobi Sheep Disease Virus RNA in Ixodid Ticks, China, 2013 - Volume 21, Number 4—April 2015 - Emerging Infectious Disease journal - CDC

Volume 21, Number 4—April 2015


Nairobi Sheep Disease Virus RNA in Ixodid Ticks, China, 2013


Technical Appendicies

To the Editor: Nairobi sheep disease virus (NSDV; genus Nairovirus, family Bunyaviridae) causes acute hemorrhagic gastroenteritis in sheep and goats (1,2). First identified in Nairobi, Kenya, in 1910, it is considered endemic in East Africa (1,3). Ganjam virus, a variant of NSDV, is found in India and Sri Lanka (2). NSDV has a limited effect on animals bred in areas to which the virus is endemic but can cause large losses of animals during introduction of new livestock or transport of animals through these areas (4). In humans, NSDV infection can cause febrile illness, headache, nausea, and vomiting (5).
Ticks are the main transmission vectors of NSDV and many other viral pathogens and therefore pose a major threat to public health (6,7). Here, we describe a newly discovered NSDV, named NSDV (China), identified by viral metagenomic analysis of ticks collected from the northeast region of the People’s Republic of China (Liaoning, Jilin, and Heilongjiang provinces) during May–July, 2013, and divided into 9 groups according to tick species and sampling sites. Four tick species were morphologically identified: Haemaphysalis longicornis (84.8%);Dermacentor silvarum (7.2%); D. nuttalli (5.5%); and Ixodes persulcatus (2.5%) (Technical Appendix[PDF - 107 KB - 13 pages] Table 1).
Of the 6,427 ticks collected, 3,410 were divided into 9 groups (average 379 ticks/group, range 163–512); each group was homogenized in SM buffer (50 mmol/L Tris, 10 mmol/L MgSO4, 0.1 mol/L NaCl, pH 7.5). Viral RNA extraction, Solexa sequencing, and analysis are described in the online Technical Appendix. Among the sequences annotated to mammalian viruses, 65 contigs were found to target the small (n = 15), medium (n = 27), and large (n = 23) segments of the NSDV genome (Technical Appendix[PDF - 107 KB - 13 pages] Tables 2–4).
To confirm the Solexa results, a 376-nt fragment of the NSDV small gene segment was amplified by reverse transcription PCR (RT-PCR) by using primers P1 (5′-AGCAAAGAGCACATTGACTGGGC-3′) and P2 (5′-CTGTCACACCTGCCTTCCAA-3′). Ticks in 3 H. longicornis groups were positive for NSDV: group 1 from sheep in Jian, Jilin Province (125°34′E, 40°52′N); group 2 from cattle in Jinxing, Jilin Province (130°38′E, 42°25′N); and group 5 from sheep in Dandong, Liaoning Province (124°23′E, 40°07′N). Ticks in the other groups were negative. The obtained sequences shared 92% identity with NSDV from H. intermedia in India.
Thumbnail of Phylogenetic analysis of Nairobi sheep disease virus (China) and other nairoviruses. The phylogenetic trees were generated in MEGA5.2 software (http://www.megasoftware.net). The complete coding regions for nucleocapsid protein in the small segment (A), glycoprotein precursor in the medium segment (B), and RNA dependent RNA polymerase in the large segment (C) were analyzed by the maximum-likelihood method. An emergent severe fever thrombocytopenia syndrome virus (SFTSV; genus Phlebov
Figure. Phylogenetic analysis of Nairobi sheep disease virus (China) and other nairoviruses. The phylogenetic trees were generated in MEGA5.2 software (http://www.megasoftware.net). The complete coding regions for nucleocapsid protein in the small...
The full-length sequence of NSDV was then obtained from group 2 by RT-PCR by using primers based on the Solexa sequences or the conserved sequences of nairoviruses (Technical Appendix[PDF - 107 KB - 13 pages]Table 5). The complete sequences of the small, medium, and large segments of NSDV (China) (GenBank accession nos. KM464724–KM464726) contained 1,590, 5,077, and 12,081 nt, respectively; that is, they were similar to other NSDVs. Sequence comparisons showed 75.1%–89.6% identity with other NSDVs at the nucleotide level and 81.3%–96.7% at the deduced amino acid level (Technical Appendix[PDF - 107 KB - 13 pages] Table 6). Compared with other member species within the genus Nairovirus (Dugbe, Kupe, Hazara, and Crimean Congo hemorrhagic fever viruses), low identities (37.5%–68.6%) were observed at both nucleotide and amino acid levels (Technical Appendix[PDF - 107 KB - 13 pages] Table 6). Phylogenetic analysis based on the amino acid sequences grouped the virus together with NSDVs from Africa and South Asia (Figure).
The remaining tick samples of the NSDV-positive groups were used to determine the infection frequency by using RT-PCR to analyze primers P1 and P2. We assayed 104 tick pools (average 15 ticks/pool, range 8–40), 13 pools of 416 ticks in Jian Province and 91 pools of 1,095 ticks in Jinxing Province; 12.5% (13/104) tested positive, 38.5% (5/13) in Jian and 8.8% (8/91) in Jinxing. The higher prevalence in Jian Province may result from more ticks in the pools. Attempts to isolate virus from the positive samples in cell lines (Vero and BHK-21) and suckling mice were unsuccessful; thus, its pathogenicity could not be determined.
In Africa, NSDV is primarily transmitted by R. appendiculatus ticks (5). In South Asia (India and Sri Lanka), NSDV has been isolated from ticks (H. intermediaH. wellingtoni, and R. haemaphysaloides), mosquitoes, sheep and humans; H. intermedia ticks are considered the main vector for the virus (5,8,9). NSDV had not previously been reported from East Asia. The isolate we identified, NSDV (China), is genetically divergent from the NSDVs of South Asia and Africa and is therefore a novel strain, with H. longicornis likely the main vector. Nairobi sheep disease has not been reported in China and East Asia, but our results indicate the risk of its occurrence in these regions, where H. longicornis is widely distributed (10). More extensive investigation to clarifty the natural circulation of NSDV among ticks should be conducted and surveillance of sheep improved to prevent outbreaks of Nairobi sheep disease in China and East Asia.
Shangshu Gong1, Biao He1, Zedong Wang1, Limin Shang, Feng Wei, Quan LiuComments to Author , and Changchun Tu
Author affiliations: Military Veterinary Institute, Academy of Military Medical Sciences, Key Laboratory of Jilin Province for Zoonosis Prevention and Control, Changchun, People’s Republic of China (S. Gong, B. He, Z. Wang, L. Shang, Q. Liu, C. Tu)College of Life Science, Jilin Agricultural University, Changchun (F. Wei)Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, People’s Republic of China (C. Tu)


This work was supported by the Science and Technology Basic Work Program from the Ministry of Science and Technology of China (2013FY113600), and the Military Medical Innovation Program of Academy of Military Medical Sciences (2012CXJJ019).


  1. Montgomery EOn a tick-borne gastro-enteritis of sheep and goats occurring in East Africa. J Comp Pathol Ther1917;30:2857DOI
  2. Marczinke BINichol STNairobi sheep disease virus, an important tick-borne pathogen of sheep and goats in Africa, is also present in Asia. Virology.2002;303:14651DOIPubMed
  3. Weinbren MPGourlay RNLumsden WHRWeinbren WMAn epizootic of Nairobi sheep disease in Uganda. J Comp Pathol Ther1958;68:17487.DOIPubMed
  4. Lasecka LBaron MDThe nairovirus Nairobi sheep disease virus/Ganjam virus induces the translocation of protein disulphide isomerase-like oxidoreductases from the endoplasmic reticulum to the cell surface and the extracellular space. PLoS ONE2014;9:e94656DOIPubMed
  5. Yadav PDVincent MJKhristova MKale CNichol STMishra ACGenomic analysis reveals Nairobi sheep disease virus to be highly diverse and present in both Africa, and in India in the form of the Ganjam virus variant. Infect Genet Evol2011;11:111120DOIPubMed
  6. Perera LPPeiris JSMWeilgama DJCalisher CHShope RENairobi sheep disease virus isolated from Haemaphysalis intermedia ticks collected in Sri Lanka. Ann Trop Med Parasitol1996;90:913 .PubMed
  7. Liu QHe BHuang SYWei FZhu XQSevere fever with thrombocytopenia syndrome, an emerging tick-borne zoonosis. Lancet Infect Dis.2014;14:76372DOIPubMed
  8. Rajagopalan PKSreenivasan MAPaul SDIsolation of Ganjam virus from the bird tick Haemaphysalis wellingtoni Nuttall and Warburton 1907.Indian J Med Res1970;58:11956 .PubMed
  9. Joshi MVGeevarghese GJoshi GDGhodke YSMourya DTMishra ACIsolation of Ganjam virus from ticks collected of domestic animals around Pune, Maharashtra, India. J Med Entomol2005;42:2046DOIPubMed
  10. Hoogstraal HRoberts FHKohls GMTipton VJReview of Haemaphysalis (Kaiseriana) longicornis Neumann (resurrected) of Australia, New Zealand, New Caledonia, Fiji, Japan, Korea, and Northeastern China and USSR, and its parthenogenetic and bisexual populations (Ixodoidea, Ixodidae). J Parasitol1968;54:1197213DOIPubMed


Technical Appendix

Suggested citation for this article: Gong S, He B, Wang Z, Shang L, Wei F, Liu Q, et al. Nairobi sheep disease virus RNA in ixodid ticks, China, 2013 [letter]. Emerg Infect Dis. 2015 Apr [date cited]. http://dx.doi.org/10.3201/eid2104.141602
DOI: 10.3201/eid2104.141602

1These authors contributed equally to this article.

No hay comentarios:

Publicar un comentario