Veterinary Public Health

Pet Health Calendar
Contact Information
Veterinary Public Health Program
313 N Figueroa St. Rm 1127
Los Angeles, CA 90012
Tel (213) 989-7060
Fax (213) 481-2375
Adobe Reader
Get Adobe Reader icon
Note: PDF documents on this site were created using Adobe Acrobat 5.0 or later. If you are using an earlier version of Adobe Acrobat Reader (4.x or less), document functionality may be reduced.
Heartworm Disease - Case Definition

This case definition is used to evaluate and categorize cases of heartworm disease reported in animals to the Los Angeles County Department of Public Health. It was developed by public health veterinarian by reviewing published published literature and reported cases of heartworm in LA County animals. Earlier case reports of this disease were reviewed and a few reclassified to meet this 2015 case definition. 

Learn more about animal disease surveillance in LA County, and about cases of heartworm in animals in LA County

CASE DEFINITION - Heartworm Disease - 2015
  • Two positive antigen tests on two separate blood samples, or

  • Positive antigen AND positive microfilaria test, or

  • Parasites seen on echocardiography

  • Positive antigen test, or

  • Positive microfilaria test

  •  Positive antibody test (feline)
  •  Positive antigen test, followed by a negative antigen test
  • No testing for heartworm performed, or

  • Positive Antigen test followed by two negative antigen tests (i.e. false positive)


1n general, cases are considered to be "Other" or "Unknown" unless the history indicates no travel outside of area.

  • UNKNOWN- Less than 2 years of travel history available.

  • LA COUNTY - Minimum of 2 years of history available, animal did NOT travel outside of LA County.

  • SO CAL - Minimum of 2 years of history available. Animal did NOT travel outside of southern California.

  • OTHER - Animal DID travel outside of southern California.

For the purpose of this case definition Southern California includes the following counties: Los Angeles, Orange, San Luis Obispo, Kern, Santa Barbara, Ventura, San Bernardino, Riverside, San Diego & Imperial.

  RATIONALE FOR SURVEILLANCE IN ANIMALS   Animals cases are sentinels for the risk of mosquito borne disease in general.
Wherever there are more cases, mosquito borne disease risk is higher.

Last updated: September 28, 2017

Public Health has made reasonable efforts to provide accurate translation. However, no computerized translation is perfect and is not intended to replace traditional translation methods. If questions arise concerning the accuracy of the information, please refer to the English edition of the website, which is the official version.
Los Angeles County Seal: Enriching lives through effective and caring services