URINE AND PARASITE TESTING
Microfilaria Testing
Laboratory evaluation for microscopic immature heartworm stages circulating in the blood, used together with other heartworm information.
THE SHORT VERSION
Testing helps answer a clinical question.
Microfilariae are microscopic immature stages produced by some adult heartworms. A concentration test or other veterinary-selected method can help evaluate whether these stages are present in the blood.
What is this test?
Microfilariae are microscopic immature stages produced by some adult heartworms. A concentration test or other veterinary-selected method can help evaluate whether these stages are present in the blood.
What information can it provide?
- A blood sample is examined with a method selected by the veterinary team.
- Concentration techniques improve the ability to detect small circulating stages.
- Species identification or additional testing may be required when another filarial parasite is possible.
When might your veterinarian recommend it?
- Add information to canine heartworm antigen testing.
- Assess an animal with suspected or confirmed heartworm infection.
- Help the veterinarian evaluate transmission risk and plan safe treatment or follow-up.
What can owners do before the visit?
- Bring accurate preventive-product and dosing history.
- Tell the clinic about prior heartworm treatment, relocation or travel.
- Follow veterinary instructions regarding additional testing or activity restriction.
What can this test not tell you by itself?
- Not every infected animal has detectable circulating microfilariae.
- A negative microfilaria result does not rule out heartworm disease.
- Results must be interpreted alongside antigen testing, species, clinical signs and imaging when needed.
Do not change medication, interpret an abnormal number as a diagnosis or delay urgent treatment without direction from your veterinary team.
Useful questions for your appointment
- Why is this test being added to the heartworm antigen test?
- Does a negative result change the need for prevention or further testing?
- What follow-up or treatment discussion is appropriate?