Table 1.
Infection rates of ticks (Amblyomma ovale, Amblyomma tigrinum, and Amblyomma tonelliae) by WNV or SLEV after acquisition feeding experiments on viremic chicks, and vector competence of the post-molted stages of ticks
| Tick species | Virus acquisition* | Transstadial perpetuation† | Vector competence‡ | |||||
|---|---|---|---|---|---|---|---|---|
| Engorged larvae | Engorged nymphs | Unfed nymphs | Unfed adults-L | Unfed adults-N | Nymphs | Adults-L | Adults-N | |
| WNV | ||||||||
| A. ovale | 9/50 (18.0) | 0/5 (0) | 2/18 (11.1) | ND | 0/6 (0) | 0/3 (0) | ND | ND |
| A. tigrinum | 3/96 (3.1) | 0/11 (0) | 0/57 (0) | 1/27 (3.7) | 1/31 (3.2) | 0/3 (0) | 0/1 (0) | 0/1 (0) |
| A. tonelliae | 21/21 (100.0) | 0/4 (0) | 29/86 (33.7) | 0/18 (0) | 3/26 (11.5) | 0/3 (0) | 0/1 (0) | 0/1 (0) |
| SLEV | ||||||||
| A. ovale | 3/28 (10.7) | 0/5 (0) | 3/22 (13.6) | ND | 0/5 (0) | 0/3 (0) | ND | ND |
| A. tigrinum | 0/22 (0) | 0/20 (0) | 12/77 (15.6) | 0/28 (0) | 0/10 (0) | 0/3 (0) | 0/1 (0) | 0/1 (0) |
| A. tonelliae | 5/14 (35.7) | 0/16 (0) | 5/21 (23.8) | 0/20 (0) | 0/21 (0) | 0/3 (0) | 0/1 (0) | 0/1 (0) |
adults-L = adult ticks previously exposed to virus during larval feeding on viremic chicks; adults-N = adult ticks previously exposed to virus during nymphal feeding on viremic chicks; SLEV = St. Louis encephalitis virus; WNV = West Nile virus; ND = no data.
Engorged larvae and nymphs were allowed to feed on viremic chicks and tested by viral infection by plaque assay at 15 days post-host detachment, before molting. Values presented as number of infected ticks/number of tested ticks (% infection).
Unfed nymphs and adults were tested after molting from engorged larvae and adults, respectively, which had fed on viremic chicks. Values presented as number of infected ticks/number of tested ticks (% infection).
Unfed nymphs and adults, previously exposed to acquisition feeding as larvae and nymphs, respectively, on viremic chicks, were allowed to feed on naive hosts (chicks for nymphs and guinea pigs for adults) to evaluate their viral vector competence. Values presented as number of hosts that became viremic or/and seroconverted after infestation/number of infested hosts (each chick or guinea pig was infested with 20 nymphs or eight adult ticks).