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Category: Vet Clinical Trials

Genetic Diversity of Dirofilaria immitis (Study Closed)
June 16, 2010 (published)
Mark Rishniw

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Study Start Date: 06/01/2010
Study End Date: 12/30/2015

Dirofilaria immitis has a worldwide distribution, and is endemic in many regions of the United States. Recent studies have suggested that heartworm from certain regions might have a reduced diversity, based on specific genetic analysis. An independent measure of diversity or polymorphism of D. immitis would help confirm initial observations, and provide information about different strains of D. immitis regarding their geographical distribution.

The ITS2 (internal transcribed spacer 2) region of the filarial genome lies between the 28S and 5.8S ribosomal genes. While the ribosomal DNA is highly conserved between species and even between genera of nematodes, the ITS2 region is substantially more variable, allowing for molecular identification of filariae by either sequencing of this region, or simple PCR-based gel electrophoresis (Rishniw M et al., Vet Parasitol 2006). We will sequence the ITS2 region in 1000 D.immitis and examine sequences for polymorphisms. We will associate polymorphisms with a geographical location from which the sample was collected and examine these for similarity in diversity.

Study Design:
Prospective case series

Sample Size:
1000 samples of microfilariae

Inclusion Criteria:

  • Microfilariae from dogs infected with D. immitis.

Exclusion Criteria:

  • Amicrofilaremic dogs with heartworm infection.

Study Controls:


Blood samples from dogs naturally infected with D. immitis. Either EDTA or heparin samples are preferred (whole clotted blood is also acceptable). Samples can be stored at 4°C and sent in batches if preferred. Each sample should be identified with a unique identifier for the patient, and a ZIP code of the patient’s place of residence.

Contact information for the submitting veterinarian should also be included to allow for additional data acquisition. A PDF file of the submission form is provided for downloading to expedite the submission procedure.

Files for Download:
Submission form


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Full Disclosure information:

  • The study is currently unfunded. Once funding is obtained, this will be updated.
  • The investigator does not have a conflict of interest.
  • The study will be published if results are negative
  • The study will be reported on VIN
  • The authors will acknowledge VIN if the study is published

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