Table 4 Results from Dirofilaria immitis (Di) antigen (Ag) and microfilariae (MF) tests on dogs for naturally occurring heartworm infection. In each study listed, microfilariae were confirmed as Dirofilaria immitis by acid phosphatase stain or by PCR unless otherwise noted

630 (16.2)^b

42 (6.7)

23 (3.7)

37 (5.9)^b

555 (88.1)

[13]

696 (15.1)

49 (7.0)

16 (2.3)

41 (5.9)

591 (84.9)

[14]

304 (27.3)

56 (18.4)

22 (7.2)

5 (1.6)

221 (72.7)

[15]

24 (62.5)

6 (25.0)

4 (16.7)

5 (20.8)

9 (37.5)

[16]

404 (12.1)

21 (5.2)

25 (6.2)

3 (0.7)

355 (87.9)

[24]

616 (7.6)

24 (3.9)^c

21 (3.4)

2 (0.3)^{b, c}

569 (92.4)

[31]

104 (18.3)

13 (12.5)

5 (4.8)

1 (1.0)

85 (81.7)

[58]