In-House Combination (Four-way) Heartworm and Tick-Borne Disease Tests: A Comparison

For dogs in some parts of the country, tick exposure (and risk of tick-borne diseases such as Lyme, Erhlichia, and Anaplasma) is a concern. Some infections can cause serious illness or even chronic disease.

Last week, we discussed some of the most commonly used in-house heartworm tests. But it’s important to remember that there are also combination heartworm tests available, which also test for common tick-borne diseases.

Depending on the risks in your area, it may make sense to screen canine patients for tick-borne diseases whenever routine or yearly heartworm testing is performed. These tests might also be good for screening patients who are symptomatic.

Here are two of the most common combination (sometimes referred to as “four-way”) heartworm and tick-borne disease tests used in-house by veterinarians…

IDEXX SNAP 4Dx Plus Test

IDEXX claims their test provides accurate results with reference laboratory quality technology. The test requires 3 drops of sample, and results are ready in 8 minutes. 

The six diseases that the SNAP 4Dx tests for are: 

• Heartworms.

• Lyme (Borrelia burgdorferi) infection.

• Ehrlichia canis and Ehrlichia ewingii.

• Anaplasma phagocytophilum and Anaplasma platys.

There is also a SNAP Pro Analyzer available, a device that saves time by automatically activating a SNAP test, reading and interpreting the test at the correct time, and adding results automatically to the medical record. 

Abaxis/Zoetis VetScan FLEX4 Rapid Test

The advertised benefits of the Abaxis (now a part of Zoetis) test are room temperature storage, a 1-year shelf life, and is very simple to use. The product information also states that the test can distinguish true Lyme disease exposure from Lyme vaccination.

The test requires 2 drops of sample and can be read in 8 minutes.

The FLEX4 tests for seven diseases, which are:

• Heartworms.

• Lyme (Borrelia burgdorferi) infection.

• Ehrlichia canis, Ehrlichia chaffeensis, and Ehrlichia ewingii.

• Anaplasma phagocytophilum and Anaplasma platys.

Similar to IDEXX, this company also offers an automatic reader—the VETSCAN VUE—to save time for veterinary technicians. Zoetis also advertises 24/7 technical support and confirmation testing (always available for heartworm, and on a case-by-case basis for tick-borne diseases).

A Few More Considerations

There is a lot of debate as to whether or not four-way tests should be used to screen healthy patients annually, versus just using a heartworm test by itself. The reason has a lot to do with the possibility of false positives.

Additionally, it’s important to know that the heartworm component tests for antigen, while the other infectious disease components test for antibodies.

This means a positive test for a tick-borne disease could potentially indicate a past exposure rather than current clinical disease. 

Some practitioners find that this can waste time—for the veterinary team and pet owner alike—and potentially make a client worry needlessly when their pet is actually healthy.

On the other hand, some practitioners feel that a positive result (one that indicates previous exposure in a currently healthy dog) opens the door to a conversation about the importance of tick control.

The best answer to these considerations will vary from practice to practice; it may be best decision based on the risk of tick-borne diseases in your area.

For example, the test may be more useful for screening in Lyme-endemic parts of the country. To determine the risk in your area, consider checking resources such as the CAPC’s Parasite Prevalence Maps.

Also, check with other practitioners in your area and see if your state board or state veterinary organization has resources or information available.

Follow-up testing can be a very useful option, especially for any positive or negative results that don’t fit the clinical picture, and to determine the best next steps for an individual patient.

Details and specifics of these tests may evolve over time. So, it’s important to check directly with the company for the most up-to-date information before making a purchase. Also, check for any special deals (or stipulations such as minimum purchase requirements) prior to finalizing a purchase decision.

Written by: Dr. Tammy Powell, DVM

Resources:

CAPC Parasite Prevalence Maps: https://capcvet.org/maps/#/2021/all-year/heartworm-canine/dog/united-states