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Volume 23, Number 12—December 2017
Dispatch

West Nile Virus Lineage 2 in Horses and Other Animals with Neurologic Disease, South Africa, 2008–2015

Marietjie VenterComments to Author , Marthi Pretorius, James A. Fuller, Elizabeth Botha, Mpho Rakgotho, Voula Stivaktas, Camilla Weyer, Marco Romito, and June Williams
Author affiliations: University of Pretoria Centre for Viral Zoonoses, Pretoria, South Africa (M. Venter, M. Pretorius, E. Botha, M. Rakgotho, V. Stivaktas, J. Williams); US Centers for Disease Control and Prevention, Global Disease Detection Centre, Pretoria (M. Venter, J.A. Fuller); National Health Laboratory Service, Tshwane, South Africa (M. Pretorius); University of Pretoria Equine Research Centre, Pretoria (C. Weyer); Onderstepoort Veterinary Research, Onderstepoort, South Africa (M. Romito)

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Table 2

Characteristics of 1,069 horses positive and negative for WNV infection, South Africa, 2008–2015*

Variable No./total (%)
 Crude OR (95% CI)
WNV negative, n = 990 WNV positive, n = 79
Detection method and result
  PCR+ IgM‒ NA 20/79 (25.3)
  PCR‒ IgM+ NA 55/79 (69.6)
  PCR+ IgM+
 NA
 4/79 (5.1)
Age, y†
  <1 64/617 (10.4) 6/61 (9.8) 1.00 (Reference)
  1–4 170/617 (27.6) 25/61 (41.0) 1.57 (0.62–4.00)
  5–9 152/617 (24.6) 15/61 (24.6) 1.05 (0.39–2.84)
  10–14 145/617 (23.5) 12/61 (19.7) 0.88 (0.32–2.46)
  >15
 86/617 (13.9)
 3/61 (4.9)‡
 0.37 (0.09–1.54)
Died or euthanized§ 240/976 (24.6) 27/79 (34.2) 1.59 (0.98–2.59)
Fever¶
 389/981 (39.7)
 28/79 (35.4)
 0.84 (0.52–1.35)
Neurologic signs
  Any neurologic sign# 785/990 (79.3) 74/79 (93.7) 3.86 (1.54–9.68)
  Ataxia¶ 249/981 (25.4) 21/79 (26.6) 1.06 (0.63–1.79)
  Paralysis¶ 67/981 (6.8) 10/79 (12.7) 1.98 (0.97–4.01)
  Paresis** 71/980 (7.2) 13/79 (16.5) 2.52 (1.33–4.79)
  Recumbent¶ 105/981 (10.7) 6/79 (7.6) 0.69 (0.29–1.62)
  Seizure¶ 35/981 (3.6) 4/79 (5.1) 1.44 (0.50–4.16)
  Tongue paralysis¶
 5/981 (0.5)
 2/79 (2.5)
 5.07 (0.97–26.56)
Other signs
  Anorexia¶ 132/981 (13.5) 6/79 (7.6) 0.53 (0.23–1.24)
  Icterus** 63/980 (6.4) 8/79 (10.1) 1.64 (0.76–3.56)
  Rectal prolapse¶ 6/981 (0.6) 2/79 (2.5) 4.22 (0.84–21.27)

*NA, not applicable; OR, odds ratio; WNV, West Nile virus; +, positive; –, negative.
†Data on age were missing for 391 of 1,069 horses. Test for trend p = 0.036.
‡p = 0.035.
§Data on this disease characteristic were missing for 14 of 1,069 horses.
¶Data on this neurologic sign were missing for 9 of 1,069 horses.
#Defined as the presence of any specific neurologic sign or the clinician indicated that it was a neurologic case without indicating specific neurologic signs.
**Data on this neurologic sign were missing for 10 of 1,069 horses.

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Page created: November 16, 2017
Page updated: November 16, 2017
Page reviewed: November 16, 2017
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.
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