Heartworm: Positive/Negative

In order to ShinBi to be cleared for transport from South Korea to Los Angeles, he had to be pest-free. ShinBi was tested for heartworms and the test came back negative. The day after ShinBi arrived, Sue Baldwin took him to the veterinarian. That was on a Friday (21 February 2014).

On Monday, Sue Baldwin learned that ShinBi was heartworm positive. How is that possible? The South Korean vet, Dr. Choi used the American Veterinary Association HW protocol and used the IDEXX HW test. HW tests are not 100 percent accurate.

The IDEXX SNAP HW RT test is 81 to 90 percent accurate according to the the Journal of the American Veterinary Medical Association. Other tests have lower accuracy rates such as the Abaxis CHAT (71-82 percent) and Heska Solo Step (71-82). The HW tests  depend upon the presence of mature female hookworms that, having been fertilized, send out offspring, microfilariae,  into the infected animal’s blood.

According to the American Heartworm Society, “A positive test tells us mature female worms are present. And, while false-negative results are uncommon, they can occur if a pet has a “male-only” infection (since the test detects antigen from females), if only one or two worms are present, or if the female worms are immature.”

ShinBi’s treatment for heartworm was started immediately.