Table 1 Quantification of transmission parameters.

From: Reproducing the Rift Valley fever virus mosquito-lamb-mosquito transmission cycle

Experiment 1, Part 1a

Experiment 1, Part 1b

    

Group 1#:

Viremia day 2 (log10)

Naive mosquitoes

Group 2#:

Infected mosquitoes

Viremia Day 17 (log10)

    

TCID50/ml

RNA copies

Fed/total (%fed)

Survivors/total (%)

fed/total (% fed)

SP/tested (%SP)

ESP/fed (%ESP)

TCID50/ml

RNA copies/ml

    

157

5.1

8.7

70/89 (79)

63/70 (90)

169

51/63 (81)

13/44 (30)

15/51 (30)

6.2

9.8

    

158

6.5

9.2

86/97 (89)

82/86 (95)

170

73/82 (89)

19/60 (32)

23/73 (32)

6.5

9.8

    

159

6.7

9.7

93/98 (95)

86/93 (92)

171

59/86 (69)

23/53 (43)

26/59 (44)

6.2

9.4

    

160

5.3

8.8

80/95 (84)

72/80 (90)

172

67/72 (93)

22/57 (39)

26/67 (39)

6.9

9.3

    

161

6.2

9.6

70/92 (76)

51/70 (73)

173

31/51 (61)

14/28 (50)

16/31 (52)

6.2

9.6

    

162

6.7

9.7

85/94 (90)

75/85 (88)

174

47/75 (63)

13/45 (29)

14/47 (30)

6.0

8.3

    

Average

6.1 ± 0.7

9.2 ± 0.5

85 ± 7%

88 ± 8%

Average

76 ± 14%

37 ± 9%

38 ± 9%

6.3 ± 0.3

9.4 ± 0.6

    

Experiment 2, Part 2a

Experiment 2, Part 2b

Experiment 2, Part 2c

Group 3#:

Infected mosquitoes

Group 3#:

Viremia day 2/3 (log10)

Naive mosquitoes

Group 4#:

Infected mosquitoes

Viremia Day 17 (log10)

Fed/total (%fed)

SP/tested (%SP)

ESP/fed (%ESP)

TCID50/ml

RNA copies

fed/total (% fed)

Survivors/total (%)

fed/total (%fed)

SP/tested (%SP)

ESP/fed (%ESP)

TCID50/ml

RNA copies/ml

151

64/92 (70)

0/0 (0)a

N.A

151

4.4

7.9

85/102 (83)

75/85 (88)

163

64/75 (85)

21/53 (40)

25/64 (39)

6.9

9.7

152

35/96 (36)

1/21 (5)

2/35 (6)

152

5.1

8.6

87/100 (87)

75/87 (86)

164

54/75 (72)

25/48 (52)

28/54 (52)

6.5

9.1

153

81/101(80)

5/54 (9)

8/81 (10)

152b

5.5

9.1

96/100 (96)

73/96 (76)

168

55/73 (75)

6/46 (13)

7/55 (13)

6.2

8.5

154

73/99 (74)

3/54 (6)

4/73 (6)

153

2.5

7.0

86/94 (91)

81/86 (94)

165

66/81 (81)

1/61 (2)

1/66 (2)

 < 1,6

4.2

155

45/102(44)

2/37 (5)

2/45 (4)

154

6.7

9.4

96/102 (94)

88/96 (92)

166

78/88 (89)

16/65 (25)

19/78 (24)

6.7

9.6

156

72/90 (80)

7/41 (17)

12/72(17)

155

5.8

8.4

87/100 (87)

67/87 (77)

167

57/67 (85)

16/49 (33)

19/57 (33)

5.8

8.7

Average

64 ± 19%

8 ± 5%

9 ± 5%

Average

5.0 ± 1.4

8.4 ± 0.9

90 ± 5%

86 ± 8%

Average

81 ± 6%

27 ± 18%

27 ± 18%

6.4 ± 0.4c

8.3 ± 2

  1. In Experiment 1 (Part 1a), lambs from Group 1 (n = 6, blue) were IV-inoculated with RVFV on day 0. When pyrexia was measured on day 2, Ae. aegypti mosquitoes were allowed to take a blood meal. Viremia levels on this day were determined by RT-qPCR and virus isolation using plasma samples. In Experiment 2 (Part 2a), mosquitoes were infected via membrane feeding on a RVFV-spiked blood meal. After 11 days incubation, the mosquitoes were allowed to feed on lambs of Group 3 (day 0), after which the presence of RVFV in mosquito saliva samples was determined. When pyrexia in lambs of Groups 1 and 3 was noted on day 2 or 3, naive mosquitoes were placed on the lambs and viremia levels on this day were determined by RT-qPCR and virus isolation using plasma samples. The total numbers of engorged mosquitoes (fed) and the total numbers of mosquitoes used for feeding (total) are indicated, as well as the percentages fed (%fed). Engorged mosquitoes were maintained in an insect incubator for 12–13 days. After this incubation period, surviving mosquitoes were allowed to feed on naive lambs (Groups 2 and 4). The presence of RVFV in mosquito saliva samples was determined by virus isolation on Vero cells after feeding on the lambs. Arrows indicate the lambs between which RVFV was transmitted. The numbers of saliva-positive mosquitoes are indicated (SP) as well as the numbers of mosquitoes tested (tested) and the percentage of saliva-positive samples (%SP). Because not all mosquitoes survived the incubation period, the expected number of saliva positives (ESP) was extrapolated by multiplying the %SP x fed. Titers of infectious virus and RNA copies in the blood of the lambs from Groups 2 and 4 at peak viremia (experimental day 17) are also indicated. N.A., not applicable.
  2. aThis lamb recovered early from sedation and violently responded to the placement of the cardboard box, resulting in mortality of all blood-fed mosquitoes.
  3. bLamb #156 was not included in Experiment 2, Part b, as this lamb succumbed to the infection before mosquitoes could feed. The corresponding mosquitoes were allowed to feed on lamb #152 on day 3.
  4. cNo infectious virus was detected in plasma of lamb #165. This sample was therefore not included when calculating the average viremia level.
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