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Table 2 Number and percentage positive for antigens of Dirofilaria immitis a in canine blood samples according to the relative prevalence in areas sampled

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

  D. immitisantigens
Categories Areas with <20% prevalence Areas with <20% prevalence
  Positive/total % Positive/total %
Hair coat length     

Short 35/430 8.1 217/555 39.1

Medium 9/185 4.9 77/252 30.6*

Long 4/56 7.1 12/53 22.6*
Predominant hair color    

White 19/226 8.4* 35/159 22.0*

Black 13/205 6.3 116/305 38.0

Golden 9/150 6.0 109/260 41.9

Brown 3/75 4.0 37/103 35.9

Gray 4/15 26.7* 9/33 27.3*
Life style     

Outdoors 38/583 6.5 200/509 39.3*

Indoors 10/88 11.4 106/351 30.2
Age (yr)     

1-2 23/330 7.0 57/204 27.9*

>2-4 8/111 7.2 95/268 35.5

>4-6 9/126 7.1 71/174 40.8

>6 8/104 7.7 83/214 38.89
Length of time at locale (yr)b    

1-2 15/205 7.3 78/245 31.8

>2-5 23/266 8.6 135/364 37.1

>5 10/200 5.0 93/250 37.2
Travelb     

No 45/650 6.9 296/813 36.4

Yes 3/20 15.0 10/47 21.3
Weight (kg)     

<5 9/185 4.9 33/126 26.2

5-15 kg 33/266 12.4* 145/457 31.7

>15-25 kg 2/116 1.7 83/194 42.8*

>25 kg 4/104 3.9 45/83 54.2*
Hemoparasitesc     

Never 44/638 6.9 245/704 34.8

Yes (previously) 1/18 5.6 33/70 47.1
Received doxycyclined    

No 47/636 7.4 243/706 34.4

Yes 1/32 3.1 31/79 39.2
  1. aWitness® HW (heartworm) antigen test kit, Zoetis, USA; bData not provided for one animal; cData not provided for 101 animals; dData not provided for 78 animals. Different symbols (* or ) within columns indicate significant difference (P < 0.05).