SNAP® Feline Triple® Test

The SNAP Feline Triple Test screens cats for feline immunodeficiency virus (FIV) antibody, feline leukemia virus (FeLV) antigen and feline heartworm (FHW) antigen. This three-in-one test for feline infectious diseases introduces an enhanced tool to promote feline health care.

A heartworm antigen positive result indicates adult heartworm infection. However, a negative test does not rule out feline heartworm infection. The recent discoveries associated with Heartworm Associated Respiratory Disease (H.A.R.D.) highlight an unfortunate drawback of antigen testing; antigen tests miss the early stage of feline heartworm disease associated with the immature adults. In cases where adult heartworm or H.A.R.D. are suspected, a negative antigen test should be followed up with an antibody test and may warrant additional tests such as radiographs and echocardiography as well as blood work.

An FIV antibody positive result indicates that a cat has been infected with FIV and may have an active infection.

An FeLV antigen positive result indicates that the cat is infected with FeLV.

Sensitivity and Specificity of the SNAP Feline Triple Test

The SNAP Feline Triple Test can be used on kittens to screen for FIV and FeLV. The feline heartworm spot is not valid for young kittens because it requires five to seven months post infection for antigen loads to be detectable on an antigen test. The heartworm spot on the test should be used on cats older than seven months of age.

If a cat under six months of age is negative for FIV, infection is unlikely. Kittens born to infected queens may test positive for antibody. Kittens tested before six months of age that are positive should be retested at 60-day intervals. If tests performed after six months of age are still confirmed positive, these kittens should be considered infected.¹

The SNAP Feline Triple Test needs to be refrigerated.

The SNAP Feline Triple Test, and any other SNAP® test, must be used within two hours of removing it from the foil package.

The SNAP Feline Triple Test requires four drops of conjugate and three drops of sample.

The read time is 10 minutes.

Serum, plasma or anticoagulated whole blood can be utilized to perform the SNAP Feline Triple Test.

The SNAP Feline Triple Test is available for sale in 5-, 15- and 30-test-kit quantities.

Kits are shipped to customers on ice via a two-day FedEx shipment.

Heartworm disease is a serious condition where worms reside in the heart and major blood vessels of cats, dogs and other species. The life cycle of heartworm begins when a mosquito bites an infected animal, such as a dog, with circulating microfilariae in its blood. As the mosquito feeds on the dog, it ingests the microfilariae. During the next 10 to 14 days, the microfilariae mature to the infective larval stage within the mosquito. When the mosquito bites, it transmits the infective stage, also known as L3 larvae.

Within three to four days the L3 larvae molt to L4 larvae and migrate in the subcutaneous tissues for approximately two months, at which time they molt to immature or juvenile worms (previously known as L5 larvae). The immature adults enter a peripheral vein and are transported via the blood to the distal pulmonary artery, where final maturation and mating occur. Many immature adults die after reaching the lungs, three to four months after infection. At this stage, the worms are about two inches long and the resultant inflammatory response causes significant lung pathology.

A small number of immature adults mature to adult heartworms in the lungs and heart of the cat. Under optimum conditions, completion of the life cycle takes 210 to 240 days. Most cats are amicrofilaremic and for this reason are dead-end hosts. However, microfilariae can be transiently found in about 20 percent of infected cats, seven to nine months after infection. Most heartworm infections in cats consist of one to six adult worms, making single sex infections not uncommon. Typically, heartworms live approximately two to four years in cats and may cause severe disease.

The Feline Heartworm Antigen Diagnostic Algorithm (PDF) details what the American Heartworm Society (AHS) and the Companion Animal Parasitic Council (CAPC) recommend when a patient tests heartworm antigen positive.

Antigen testing is highly specific and results in few false positives. However, the AHS and other industry leaders recommend following up positive tests with:

• Another antigen test
• Radiographs
• Blood work, at the practitioner’s discretion

This allows the practitioner to better understand the stage of infection in the cat.

In cats without clinical signs, case management may be limited to having the clients closely watch their cats for acute signs of illness. Educating pet owners to look for clinical signs of feline heartworm disease will help to prepare the clients in the event of clinical crises that would require cats to come directly to the practice. In addition, some practitioners may consider sending patients home with emergency medication. According to the AHS guidelines, it’s appropriate to retest a cat within 6–12 months for seronegativity for feline heartworm and radiographic evidence of the disease’s progression and/or regression. Refer to the AHS guidelines for complete testing, management and prevention recommendations.

Also, cats testing positive for feline heartworm should be placed on prevention, because these cats are susceptible to additional infections and are obviously at risk for feline heartworm infection.

Treatment recommendations from the AHS:

Adulticide administration (melarsomine) is not recommended for use in cats. Cats therefore will eventually experience the death of the adult worm(s) at which time clinical manifestation is likely. Survival rates associated with feline heartworm infections are as high as 80 percent.¹ Seroconversion of a positive antigen test to a negative status indicates the period of risk has probably passed, although it is possible for an undetectable heartworm to remain.

Both cats with radiographic changes consistent with heartworm, and cats with clinical signs associated with adult or juvenile heartworm infections, can benefit from supportive therapy.

If positive, the antigen spot on the SNAP Feline Triple Test provides a definitive diagnosis for adult heartworm infection. The disadvantage of an antigen test is that it can’t detect heartworm infection prior to the adult phase, which is about five to seven months postinfection. An antigen test will not detect cats with clinical signs associated with the juvenile stages of Heartworm Associated Respiratory Disease (H.A.R.D.).

Antibody tests detect exposure as early as two months post-exposure. However, an antibody test cannot differentiate between cats that are infected and cats that have cleared their infection. To further complicate this picture, cats on prevention may become antibody positive because an antibody response can be mounted before the preventative successfully clears the larvae stage.

Antigen tests offer a definitive answer (and the least confusion) because they are diagnostic for adult heartworm infection, which is why IDEXX chose the antigen option. (Please note that the American Heartworm Society recommends running an antigen and an antibody test together.)

By adding a heartworm antigen spot to the SNAP® FIV/FeLV Combo Test, the SNAP Feline Triple Test will result in thousands of cats being tested for feline heartworm. There are limitations to heartworm testing in the cat. Specifically, antigen testing illuminates only adult worm infections, a small part of the total feline heartworm disease picture.

Veterinarians need help understanding how testing for feline heartworm can improve their ability to 1) manage individual cases, and 2) understand the risk of feline heartworm disease in their region. So key opinion leaders used published studies to develop a concept they call the “Tip of the Iceberg.” This predictive model relates the number of antigen positives found in a practice area to the overall impact of the disease.

Testing with the SNAP Feline Triple Test will “find” heartworm positives, but this is just the “Tip of the Iceberg.” It has been proposed that for every antigen positive, there are 10 times as many cats infected with Heartworm Associated Respiratory Disease (H.A.R.D.) and even more are at risk of exposure to feline heartworm. To review, H.A.R.D. is the inflammatory response associated with juvenile or adult worm death. Only reproductively active adults express enough antigen in quantities that are detectable on the SNAP Feline Triple Test.

Use the “Tip of the Iceberg” model to help determine if prevention of heartworm and H.A.R.D. is appropriate in your practice.

The clinical signs of heartworm infection in cats can be nonspecific and can take the form of respiratory, gastrointestinal or occasionally, neurological manifestations. These respiratory signs may be transient and resolve in a couple of days. Feline heartworm infection may mimic other feline diseases, which makes diagnosis by clinical signs alone difficult. These clinical signs, such as intermittent coughing, asthma-like signs, chronic respiratory disease/respiratory distress or vomiting have all been associated with heartworm infection.

Cats infected with FIV, FeLV and feline heartworm present with multiple signs. However, it is common for infected cats to present with no clinical signs at all. Some of the most common reasons for testing cats are listed below.

The American Heartworm Society (AHS) feline heartworm guidelines support screening healthy cats with a feline heartworm antigen test. However, the preferred method is to screen healthy cats with both antibody and antigen tests.

For cats presenting with clinical signs consistent with Heartworm Associated Respiratory Disease (H.A.R.D.), AHS recommends complementing antigen and antibody tests with thoracic radiography and/or echocardiography.

The AHS recommends testing to monitor the clinical course of cats that have already been diagnosed with feline heartworm infection and to establish a baseline reference point prior to initiation of prevention.

See the AHS guidelines for complete testing, management and prevention recommendations.

SNAP Feline Triple is an antigen test. Antigen usually becomes detectable at approximately five to seven months post infection.

Yes. Several studies have investigated the risk of feline heartworm to indoor cats. In those studies, it has been found that up to one-fourth of cats diagnosed with feline heartworm were classified as indoor-only.^1,2

Following treatment according to the American Heartworm Society (AHS) guidelines, retesting 6–12 months for seronegativity for feline heartworm and radiographic evidence of the disease’s progression and/or regression is appropriate. See the AHS guidelines for complete testing, management and prevention recommendations.

Testing your patients can help identify the prevalence of heartworm disease in your practice population and help you determine whether feline heartworm preventatives are appropriate in your practice.

While there’s no cure for heartworm infection, the reported survival rates are as high as 80%¹; and cats with clinical signs of the disease can be managed. The American Heartworm Society (AHS) guidelines list specific therapies available for heartworm-infected cats with or without acute signs. Therapies range from treating obvious clinical signs with prednisone to stabilizing acutely ill cats with treatments appropriate for shock.

In addition to testing cats suspected of heartworm infection, the AHS recommends testing to monitor the clinical course of those cats that have already been diagnosed with feline heartworm infection and to establish a baseline reference point prior to the initiation of prevention.

Yes, the American Association of Feline Practitioners (AAFP) (PDF) recommends testing all newly adopted cats and kittens for FIV and FeLV.

If a cat under 6 months of age is negative for FIV, infection is unlikely. Kittens born to infected queens may test positive for antibody. Kittens tested before 6 months of age that are positive should be retested at 60-day intervals. If tests performed after 6 months of age are still confirmed positive, these kittens should be considered infected.²

If the client chooses to vaccinate, the AAFP guidelines suggest that the cat be tested prior to vaccination.^1,2

Yes, the FIV vaccination cross-reacts with the FIV test because the test detects FIV antibodies. There is no commercially available, licensed test that can differentiate between the vaccine and natural infection.

SNAP FIV/FeLV Combo Test Sensitivity and Specificity

Sensitivity and Specificity of the SNAP Feline Triple Test