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Table 3 Percentage of positive canine tests for heartworm antigens a within physical category and according to clinical signs

From: Updated canine infection rates for Dirofilaria immitis in areas of Brazil previously identified as having a high incidence of heartworm-infected dogs

Category     Coughing Syncope Dyspnea Exercise intolerance Weight loss
No. Pos Total % No. Pos No. Neg No. Pos No. Neg No. Pos No. Neg No. Pos No. Neg No. Pos No. Neg
Age (yr)              

1-2 80 534 15.0* 6 (7.5) 21 (4.6) 1 (1.3) 1 (0.2) 2 (2.5) 7 (1.5) 3 (3.8) 20 (4.4) 5 (6.3) 22 (4.8)

>2-4 103 379 27.2 11 (10.7) 36 (13.0) 0 (0.0) 2 (0.7) 3 (2.9) 7 (2.5) 9 (8.7) 22 (8.0) 8 (7.8) 26 (9.4)

>4-6 80 300 26.7 13 (16.3) 23 (10.6) 0 (0.0) 0 (0.0) 6 (7.5) 7 (3.2) 7 (8.8) 23 (10.6) 8 (10.0) 13 (6.0)

>6 91 318 28.6 20 (22.0) 48 (21.1) 3 (3.3) 9 (4.0) 4 (4.4) 15 (6.6) 17 (18.7) 48 (21.1) 12 (13.2) 40 (17.6)
Weight (kg)              

<5 42 311 13.5* 8 (19.0) 35 (13.0) 0 (0.0) 3 (1.1) 1 (2.4) 9 (3.3) 6 (14.3) 22 (8.2) 9 (21.4) 23 (8.6)

5-15 178 723 24.6 24 (13.5) 70 (12.8) 2 (1.1) 7 (1.3) 7 (3.9) 20 (3.7) 16 (9.0) 55 (10.1) 9 (5.1) 39 (7.2)

>15-25 85 310 27.4 9 (10.6) 17 (7.6) 0 (0.0) 1 (0.4) 2 (2.4) 4 (1.8) 7 (8.2) 22 (9.8) 8 (9.4) 21 (9.3)

>25 49 187 26.2 9 (18.4) 6 (4.3) 2 (4.1) 1 (0.7) 5 (10.2) 3 (2.2) 7 (14.3) 14 (10.1) 7 (14.3) 18 (13.0)
Breed              

Mongrel 245 924 26.5 31 (12.7) 67 (9.9) 3 (1.2) 8 (1.2) 5 (2.0) 18 (2.7) 19 (7.6) 56 (8.3) 18 (7.3) 54 (8.0)

Mixed 45 330 13.6* 11 (24.4) 23 (8.1) 0 (0.0) 0 (0.0) 3 (6.7) 6 (2.1) 5 (11.1) 22 (7.7) 5 (11.1) 20 (7.0)

Purebred 64 277 23.1 8 (12.5) 37 (17.4) 1 (1.6) 4 (1.9) 7 (10.9) 11 (5.2) 12 (18.8) 34 (16.0) 10 (15.6) 27 (12.7)
Sex              

Female 196 838 23.4 21 (10.7) 56 (8.7) 1 (0.5) 4 (0.6) 4 (2.0) 18 (2.8) 18 (9.2) 59 (9.2) 15 (7.7) 46 (7.2)

Male 158 693 22.8 29 (18.4) 72 (13.5) 3 (1.9) 8 (1.5) 11 (7.0) 18 (3.4) 18 (11.4) 54 (10.1) 18 (11.4) 55 (10.3)
Data missing     3 9 2 5 4 11 3 7 1 10
  1. aTested with Witness® HW (heartworm) antigen test kit, Zoetis, USA. Different symbols (* or ) within a column indicate difference among category variables (P < 0.01).