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.