Feline Viral Diseases: FIP, FeLV, and FIV
The three major feline viral diseases are feline infectious peritonitis (FIP), feline leukemia virus (FeLV), and feline immunodeficiency virus (FIV). These viruses are specific to cats and cannot be transmitted to humans or other animals. The occurrence of FeLV and FIV and the rate of transmission of these diseases in house cats and feral cat colonies is very low. Large epidemiologic studies “indicate FeLV and FIV are present in approximately 4% of feral cats, which is not substantially different from the infection rate reported for pet cats” (Levy and Crawford, 2004).
Feline Infectious Peritonitis (FIP)
What is FIP?
Feline infectious peritonitis (FIP) is a viral disease caused by certain strains of the feline coronavirus. Most strains of the feline coronavirus are found in the gastrointestinal tract and cause only short periods of diarrhea and/or mild upper respiratory troubles that resolve on their own. Infected cats usually show no symptoms in the initial stages of coronavirus infection, and the virus only progresses into clinical FIP in a small number of infected cats—5% to 10%— when there is a mutation of the virus or an abnormality in the immune response. When this occurs, the mutated virus is able to spread to other organs in the cat's body (Cornell, “Feline Infectious Peritonitis,” 2014).
Symptoms
For cats who develop FIP, symptoms usually appear suddenly and increase in severity, usually resulting in death (without treatment - see "Treatment" section below). The cats often develop nonspecific symptoms such as weight loss, loss of appetite, depression, roughness of hair, and fever. Tissues around the infected cells, usually in the abdomen, kidney, or brain, also become intensely inflamed (Cornell, “Feline Infectious Peritonitis,” 2014).
Diagnosis
Because the symptoms of FIP are not uniform, often manifesting differently in different cats, and sometimes appearing similar to other diseases, there is no definitive way to diagnose it without a biopsy. Veterinarians often diagnose based on an evaluation of the cat’s history and symptoms in combination with coronavirus test results (Cornell, “Feline Infectious Peritonitis,” 2014).
Types
There are two forms of the virus. In the wet ("effusive") form, cats will have an accumulation of fluid in the abdominal cavity, the chest cavity or both. In addition to the symptoms for both forms, cats with the wet form can show labored breathing and abdominal distension. In the dry (noneffusive") form, cats will have small accumulations of inflammatory cells form in various organs. Symptoms of the dry form depend on which organs are affected by the inflammatory cells. For example, a cat with affected kidneys will show excessive thirst and urination. The wet form usually progresses more rapidly than the dry form, but in both cases the cat's hair will become rough and dull and he will become progressively more lethargic and depressed.
Risk
Any cat that carries any coronavirus is potentially at risk for developing FIP. However, cats with weak immune systems are most likely to develop the disease, including kittens, cats already infected with feline leukemia virus (FeLV), and geriatric cats. Most cats that develop FIP are under two years of age, but cats of any age may develop the disease.
Transmission
FIP is not highly contagious and is transmitted through saliva and feces during acute infection. The virus can survive in the environment for several weeks, and can be spread through the air. The most common transmission of feline coronavirus occurs when infected female cats pass along the virus to their kittens, typically when the kittens are between five and eight weeks of age. FIP most commonly affects cats in multi-cat households and is not as common in outdoor cats. This may be because outdoor cats bury their feces away from other colony members, while indoor cats usually use the same litter boxes.
Treatment
An FIP diagnosis used to be a death sentence, but a new drug has been developed and tested within the past couple of years that can cure FIP. The drug is an anti-viral called GS-441524 (GS) that is administered by injection. The medication must be given every day for a period of at least 12 weeks. The younger the cat, the more effective the treatment and dosage depends on the weight of the cat. The cost of a 5 mL bottle of G2 varies greatly between manufacturers, but it is within the range of $80 - $358. Learn more about GS and how to use it at www.fipwarriors.com and https://sockfip.org/.
Supportive care and high quality nutrition can help alleviate some of the body’s inflammatory response to the disease. Corticosteroids, cytotoxic drugs, and antibiotics are often used to treat FIP, and fluid therapy and blood transfusions may also help as supportive care (Cornell, “Feline Infectious Peritonitis,” 2014).
Vaccine
A vaccine to prevent FIP is available but its use is controversial. The vaccine is not 100% effective and must be given before the cat is exposed to coronavirus. Since FIP is not a common ailment, the vaccine is not always recommended. Cat owners should speak with their vets to see if the vaccine is the right option for their cat.
Disinfection
Foster parents and cat guardians with a cat with FIP and other cats living in the household should efficiently clean their homes to reduce the chance of infection to others. Litter boxes, bowls, and scratching posts should be cleaned with hot soap and water and then rinsed with a 1:32 dilution of bleach with water. The house should be thoroughly vacuumed as well. Objects such as blankets and cat beds should be thrown away.
ACR recommends Pets WebMD for more information.
Feline Leukemia Virus (FeLV)
What is Feline Leukemia?
The feline leukemia virus (FeLV) is a retrovirus belonging to the subfamily Oncovirinae, which means it is a cancer-causing virus. In addition to causing feline leukemia, FeLV suppresses the cat’s immune system, leaving them vulnerable to a variety of other diseases. The signs and symptoms of infection with FeLV are varied and include loss of appetite, poor coat condition, infections of the skin, bladder and respiratory tract, oral disease, seizures, swollen lymph nodes, fatigue, fever, weight loss, recurring bacterial and viral illnesses, anemia, diarrhea, and jaundice (Cornell, “Feline Leukemia Virus,” 2014). Some cats can be carriers of the disease and show no signs of illness for many years.
Transmission
Feline leukemia only affects cats; it cannot be transmitted to people or other animals. Infected cats shed FeLV primarily in their saliva, although the virus may also be present in the blood, tears, feces, or urine. Grooming and fighting appear to be the most common ways for the infection to spread. Other modes of FeLV transmission include sharing food dishes and litter boxes, and in utero transfer from a mother cat to her kittens. A mother cat can also transmit FeLV to her kittens through infected milk. Additionally, the disease is often spread by seemingly healthy cats, so cats that appear healthy may still be infected and able to transmit the virus.
Diagnosis
A simple blood test can be performed in a veterinary office to determine if a cat has contracted FeLV; however, most TNR programs choose not to test feral cats for the disease. Whether a feral cat tests negative for the disease or she is not tested, we strongly recommend all feral cats receive an FeLV vaccine to reduce the risk of transmission.
Risk
Resistance seems to increase with age, so older cats are less likely to contract the infection. Indoor-only cats are also at low risk of contracting FeLV. Cats in multi-cat households are at a higher risk, especially if they share water and food dishes and litter boxes.
Symptoms
Cats infected with the virus may exhibit one or more of the following symptoms: pale gums, yellow color in the mouth and whites of eyes, enlarged lymph nodes, bladder, skin, or upper respiratory infections, weight loss and/or loss of appetite, poor coat condition, weakness and lethargy, fever, diarrhea, difficulty breathing, and stomatitis.
Treatment
There is no cure for FeLV, although veterinarians can treat or alleviate the opportunistic infections associated with the virus. Regular vet check-ups and good preventive health care can help keep infected cats feeling well for some time and help prevent secondary infection. Bi-annual physical exams, lab testing, and parasite control can prevent complications and promptly identify any problems. FeLV infected cats should be kept indoors as well as be fixed. Their environments should be as stress-free as possible. Additionally, nutritional support (herbs, vitamins) and other alternative treatments can help strengthen a cat’s impaired immune system.
Prognosis
Although the majority of cats with aggressive FeLV will die within three years of diagnosis, exposure to the feline leukemia virus doesn’t mean an automatic death sentence. About 70% of cats who encounter the virus are able to resist infection or eliminate the virus on their own.
Prevention
Keeping your cat indoors and away from infected cats will prevent him from contracting FeLV. Vaccines are an option for cats at high risk, such as those who go outside. In order to receive the vaccine, cats must first test negative for FeLV, and even after receiving the vaccine, cats should be tested to determine if there has been a possible exposure to the virus. According to the American Association of Feline Practitioners, any cat who is sick should be tested for FeLV, because there are a number of health issues that can be associated with the virus.
New cats or kittens over eight weeks of age should be tested for the virus before being introduced to a multi-cat household. Most veterinarians discourage introducing new cats into a household with a FeLV-positive cat, as they may be at risk for contracting the infection, even with the vaccine.
Feline Immunodeficiency Virus (FIV)
What is FIV?
Feline immunodeficiency virus (FIV) is a retrovirus that virologists classify as a lentivirus, or “slow-acting virus.” Cats diagnosed with FIV may live long, healthy lives, never showing symptoms of the virus, though some cats may experience “recurrent illness interspersed with periods of relative health” (Cornell, “Feline Immunodeficiency Virus,” 2014). FIV suppresses the cat’s immune system, compromising her ability to fight off infections.
Symptoms
Common signs and symptoms of the disease include poor coat condition, persistent fever, loss of appetite, weight loss, inflammation of the gums and mouth, chronic or recurrent skin, urinary tract, bladder, and upper respiratory infections, and a variety of eye conditions may occur. FIV positive cats are also much more susceptible to various kinds of cancer and blood diseases, and some experience seizures, or behavioral and neurological disorders (Cornell, “Feline Immunodeficiency Virus,” 2014).
Transmission
Fortunately, FIV is not transmitted as easily as FeLV. The most common mode of transmission is through bite wounds. This explains why the cats most likely to become infected are free-roaming, unneutered males who are prone to territorial fighting. FIV does not appear to spread through casual contact among cats, so it is possible to keep an FIV-positive cat in the same household as a healthy cat with little risk of transmission, provided the cats tolerate one another and do not fight. There is no danger of FIV spreading through sexual contact, and only rarely does a mother pass it on to her kittens, either through birth or infected milk (Cornell, “Feline Immunodeficiency Virus,” 2014).
Diagnosis
A simple blood test can be performed in a veterinary office to determine if a cat has contracted FIV. However, most TNR programs choose not to test feral cats for the disease. Kittens testing positive for FIV are not necessarily infected. If a kitten tests positive, the test is probably detecting antibodies passed from the mother to the kitten through colostrum, the first milk that the mother cat produces. Positive kittens should be retested between four and six months of age, when any antibodies obtained from the mother cat will have disappeared.
Vaccine
There is a vaccine to protect against FIV, though it is rarely administered. Any cat who receives the vaccine will then test positive for the disease, because she will be carrying antibodies.
Treatment
There is no cure for FIV; however, like FeLV, veterinarians can treat or at least alleviate the infections associated with the virus. Proper nutrition and good supportive care can help strengthen a cat’s impaired immune system and improve her quality of life.
Prognosis
Providing medical supportive care and keeping FIV-positive cats in a stress-free, indoor environment can allow them to live comfortable lives for months to years.
FIV/FeLV and Euthanasia of Feral Cats
While FIV and FeLV affect only cats, not all cats that are infected will develop the diseases. FIV and FeLV are not a death sentence. Cats that test positive for FIV regularly live long, healthy lives. In fact, most veterinarians don’t test feral cats for FeLV or FIV, as most feral cats have good health and have no higher rates of infection than owned cats. In fact, both owned and feral cats have an incidence rate of FIV and FeLV at an equally low rate, approximately 4%. Furthermore, several large spay/neuter clinics report only 1-2% of FeLV infections when cats are tested.
There are numerous reasons as to why feral cats who test positive for FIV or FeLV should not be euthanized. Aside from the fact that cats who test positive go on to live happy, healthy lives, test results can be unreliable, and can result in false positives. Sterilizing cats helps prohibit the spread of the viruses, as it prevents fighting and breeding.
Cats who test positive are also often asymptomatic. They can remain healthy and exhibit no signs of illness for multiple years, or their entire life. As a result, more cats die just from testing positive and being euthanized than die from FIV-related complications. Furthermore, FIV tests do not differentiate between the FIV infection and the FIV vaccination. Therefore, a positive test can often mean that vaccinated cats who are not infected are euthanized.
Ultimately, there are numerous reasons why it isn’t recommended to test feral cats for FIV/FeLV, as it is cost prohibitive as well as the numbers of positives are similar to those of owned cats. When the feral cats are sterilized, the risk of transmission is incredibly low. Feral cats live happy, healthy lives even when testing positive for FIV/FeLV, and there is no reason to deprive them of that.
Resources
Cornell Feline Health Center. “Feline Infectious Peritonitis.” Ithaca, New York: Cornell University College of Veterinary Medicine, 2014. Web. 29 Sept. 2014.
Cornell Feline Health Center. “Feline Leukemia Virus.” Ithaca, New York: Cornell University College of Veterinary Medicine, 2014. Web. 29 Sept. 2014.
Cornell Feline Health Center. “Feline Immunodeficiency Virus.” Ithaca, New York: Cornell University College of Veterinary Medicine, 2014. Web. 29 Sept. 2014.
Flowers, Amy. “Feline Leukemia Virus (FeLV) Symptoms, Vaccine, Treatment.” WebMD, WebMD, 10 Sept. 2018, https://pets.webmd.com/cats/facts-about-feline-leukemia-virus#1. 5 Dec. 2019
Levy, Julie K., and P. Cynda Crawford. “Humane Strategies for Controlling Feral Cat Populations.” Journal of the American Veterinary Medical Association 225.9 (2004): 1354–60. Avmajournals.avma.org (Atypon). Web. 18 Aug. 2014.
“PetMD, LLC.” PetMD, https://www.petmd.com/cat/conditions/infectious-parasitic/c_ct_feline_infectious_peritonitis. 4 Dec. 2019
Feline Infectious Peritonitis (FIP)
What is FIP?
Feline infectious peritonitis (FIP) is a viral disease caused by certain strains of the feline coronavirus. Most strains of the feline coronavirus are found in the gastrointestinal tract and cause only short periods of diarrhea and/or mild upper respiratory troubles that resolve on their own. Infected cats usually show no symptoms in the initial stages of coronavirus infection, and the virus only progresses into clinical FIP in a small number of infected cats—5% to 10%— when there is a mutation of the virus or an abnormality in the immune response. When this occurs, the mutated virus is able to spread to other organs in the cat's body (Cornell, “Feline Infectious Peritonitis,” 2014).
Symptoms
For cats who develop FIP, symptoms usually appear suddenly and increase in severity, usually resulting in death (without treatment - see "Treatment" section below). The cats often develop nonspecific symptoms such as weight loss, loss of appetite, depression, roughness of hair, and fever. Tissues around the infected cells, usually in the abdomen, kidney, or brain, also become intensely inflamed (Cornell, “Feline Infectious Peritonitis,” 2014).
Diagnosis
Because the symptoms of FIP are not uniform, often manifesting differently in different cats, and sometimes appearing similar to other diseases, there is no definitive way to diagnose it without a biopsy. Veterinarians often diagnose based on an evaluation of the cat’s history and symptoms in combination with coronavirus test results (Cornell, “Feline Infectious Peritonitis,” 2014).
Types
There are two forms of the virus. In the wet ("effusive") form, cats will have an accumulation of fluid in the abdominal cavity, the chest cavity or both. In addition to the symptoms for both forms, cats with the wet form can show labored breathing and abdominal distension. In the dry (noneffusive") form, cats will have small accumulations of inflammatory cells form in various organs. Symptoms of the dry form depend on which organs are affected by the inflammatory cells. For example, a cat with affected kidneys will show excessive thirst and urination. The wet form usually progresses more rapidly than the dry form, but in both cases the cat's hair will become rough and dull and he will become progressively more lethargic and depressed.
Risk
Any cat that carries any coronavirus is potentially at risk for developing FIP. However, cats with weak immune systems are most likely to develop the disease, including kittens, cats already infected with feline leukemia virus (FeLV), and geriatric cats. Most cats that develop FIP are under two years of age, but cats of any age may develop the disease.
Transmission
FIP is not highly contagious and is transmitted through saliva and feces during acute infection. The virus can survive in the environment for several weeks, and can be spread through the air. The most common transmission of feline coronavirus occurs when infected female cats pass along the virus to their kittens, typically when the kittens are between five and eight weeks of age. FIP most commonly affects cats in multi-cat households and is not as common in outdoor cats. This may be because outdoor cats bury their feces away from other colony members, while indoor cats usually use the same litter boxes.
Treatment
An FIP diagnosis used to be a death sentence, but a new drug has been developed and tested within the past couple of years that can cure FIP. The drug is an anti-viral called GS-441524 (GS) that is administered by injection. The medication must be given every day for a period of at least 12 weeks. The younger the cat, the more effective the treatment and dosage depends on the weight of the cat. The cost of a 5 mL bottle of G2 varies greatly between manufacturers, but it is within the range of $80 - $358. Learn more about GS and how to use it at www.fipwarriors.com and https://sockfip.org/.
Supportive care and high quality nutrition can help alleviate some of the body’s inflammatory response to the disease. Corticosteroids, cytotoxic drugs, and antibiotics are often used to treat FIP, and fluid therapy and blood transfusions may also help as supportive care (Cornell, “Feline Infectious Peritonitis,” 2014).
Vaccine
A vaccine to prevent FIP is available but its use is controversial. The vaccine is not 100% effective and must be given before the cat is exposed to coronavirus. Since FIP is not a common ailment, the vaccine is not always recommended. Cat owners should speak with their vets to see if the vaccine is the right option for their cat.
Disinfection
Foster parents and cat guardians with a cat with FIP and other cats living in the household should efficiently clean their homes to reduce the chance of infection to others. Litter boxes, bowls, and scratching posts should be cleaned with hot soap and water and then rinsed with a 1:32 dilution of bleach with water. The house should be thoroughly vacuumed as well. Objects such as blankets and cat beds should be thrown away.
ACR recommends Pets WebMD for more information.
Feline Leukemia Virus (FeLV)
What is Feline Leukemia?
The feline leukemia virus (FeLV) is a retrovirus belonging to the subfamily Oncovirinae, which means it is a cancer-causing virus. In addition to causing feline leukemia, FeLV suppresses the cat’s immune system, leaving them vulnerable to a variety of other diseases. The signs and symptoms of infection with FeLV are varied and include loss of appetite, poor coat condition, infections of the skin, bladder and respiratory tract, oral disease, seizures, swollen lymph nodes, fatigue, fever, weight loss, recurring bacterial and viral illnesses, anemia, diarrhea, and jaundice (Cornell, “Feline Leukemia Virus,” 2014). Some cats can be carriers of the disease and show no signs of illness for many years.
Transmission
Feline leukemia only affects cats; it cannot be transmitted to people or other animals. Infected cats shed FeLV primarily in their saliva, although the virus may also be present in the blood, tears, feces, or urine. Grooming and fighting appear to be the most common ways for the infection to spread. Other modes of FeLV transmission include sharing food dishes and litter boxes, and in utero transfer from a mother cat to her kittens. A mother cat can also transmit FeLV to her kittens through infected milk. Additionally, the disease is often spread by seemingly healthy cats, so cats that appear healthy may still be infected and able to transmit the virus.
Diagnosis
A simple blood test can be performed in a veterinary office to determine if a cat has contracted FeLV; however, most TNR programs choose not to test feral cats for the disease. Whether a feral cat tests negative for the disease or she is not tested, we strongly recommend all feral cats receive an FeLV vaccine to reduce the risk of transmission.
Risk
Resistance seems to increase with age, so older cats are less likely to contract the infection. Indoor-only cats are also at low risk of contracting FeLV. Cats in multi-cat households are at a higher risk, especially if they share water and food dishes and litter boxes.
Symptoms
Cats infected with the virus may exhibit one or more of the following symptoms: pale gums, yellow color in the mouth and whites of eyes, enlarged lymph nodes, bladder, skin, or upper respiratory infections, weight loss and/or loss of appetite, poor coat condition, weakness and lethargy, fever, diarrhea, difficulty breathing, and stomatitis.
Treatment
There is no cure for FeLV, although veterinarians can treat or alleviate the opportunistic infections associated with the virus. Regular vet check-ups and good preventive health care can help keep infected cats feeling well for some time and help prevent secondary infection. Bi-annual physical exams, lab testing, and parasite control can prevent complications and promptly identify any problems. FeLV infected cats should be kept indoors as well as be fixed. Their environments should be as stress-free as possible. Additionally, nutritional support (herbs, vitamins) and other alternative treatments can help strengthen a cat’s impaired immune system.
Prognosis
Although the majority of cats with aggressive FeLV will die within three years of diagnosis, exposure to the feline leukemia virus doesn’t mean an automatic death sentence. About 70% of cats who encounter the virus are able to resist infection or eliminate the virus on their own.
Prevention
Keeping your cat indoors and away from infected cats will prevent him from contracting FeLV. Vaccines are an option for cats at high risk, such as those who go outside. In order to receive the vaccine, cats must first test negative for FeLV, and even after receiving the vaccine, cats should be tested to determine if there has been a possible exposure to the virus. According to the American Association of Feline Practitioners, any cat who is sick should be tested for FeLV, because there are a number of health issues that can be associated with the virus.
New cats or kittens over eight weeks of age should be tested for the virus before being introduced to a multi-cat household. Most veterinarians discourage introducing new cats into a household with a FeLV-positive cat, as they may be at risk for contracting the infection, even with the vaccine.
Feline Immunodeficiency Virus (FIV)
What is FIV?
Feline immunodeficiency virus (FIV) is a retrovirus that virologists classify as a lentivirus, or “slow-acting virus.” Cats diagnosed with FIV may live long, healthy lives, never showing symptoms of the virus, though some cats may experience “recurrent illness interspersed with periods of relative health” (Cornell, “Feline Immunodeficiency Virus,” 2014). FIV suppresses the cat’s immune system, compromising her ability to fight off infections.
Symptoms
Common signs and symptoms of the disease include poor coat condition, persistent fever, loss of appetite, weight loss, inflammation of the gums and mouth, chronic or recurrent skin, urinary tract, bladder, and upper respiratory infections, and a variety of eye conditions may occur. FIV positive cats are also much more susceptible to various kinds of cancer and blood diseases, and some experience seizures, or behavioral and neurological disorders (Cornell, “Feline Immunodeficiency Virus,” 2014).
Transmission
Fortunately, FIV is not transmitted as easily as FeLV. The most common mode of transmission is through bite wounds. This explains why the cats most likely to become infected are free-roaming, unneutered males who are prone to territorial fighting. FIV does not appear to spread through casual contact among cats, so it is possible to keep an FIV-positive cat in the same household as a healthy cat with little risk of transmission, provided the cats tolerate one another and do not fight. There is no danger of FIV spreading through sexual contact, and only rarely does a mother pass it on to her kittens, either through birth or infected milk (Cornell, “Feline Immunodeficiency Virus,” 2014).
Diagnosis
A simple blood test can be performed in a veterinary office to determine if a cat has contracted FIV. However, most TNR programs choose not to test feral cats for the disease. Kittens testing positive for FIV are not necessarily infected. If a kitten tests positive, the test is probably detecting antibodies passed from the mother to the kitten through colostrum, the first milk that the mother cat produces. Positive kittens should be retested between four and six months of age, when any antibodies obtained from the mother cat will have disappeared.
Vaccine
There is a vaccine to protect against FIV, though it is rarely administered. Any cat who receives the vaccine will then test positive for the disease, because she will be carrying antibodies.
Treatment
There is no cure for FIV; however, like FeLV, veterinarians can treat or at least alleviate the infections associated with the virus. Proper nutrition and good supportive care can help strengthen a cat’s impaired immune system and improve her quality of life.
Prognosis
Providing medical supportive care and keeping FIV-positive cats in a stress-free, indoor environment can allow them to live comfortable lives for months to years.
FIV/FeLV and Euthanasia of Feral Cats
While FIV and FeLV affect only cats, not all cats that are infected will develop the diseases. FIV and FeLV are not a death sentence. Cats that test positive for FIV regularly live long, healthy lives. In fact, most veterinarians don’t test feral cats for FeLV or FIV, as most feral cats have good health and have no higher rates of infection than owned cats. In fact, both owned and feral cats have an incidence rate of FIV and FeLV at an equally low rate, approximately 4%. Furthermore, several large spay/neuter clinics report only 1-2% of FeLV infections when cats are tested.
There are numerous reasons as to why feral cats who test positive for FIV or FeLV should not be euthanized. Aside from the fact that cats who test positive go on to live happy, healthy lives, test results can be unreliable, and can result in false positives. Sterilizing cats helps prohibit the spread of the viruses, as it prevents fighting and breeding.
Cats who test positive are also often asymptomatic. They can remain healthy and exhibit no signs of illness for multiple years, or their entire life. As a result, more cats die just from testing positive and being euthanized than die from FIV-related complications. Furthermore, FIV tests do not differentiate between the FIV infection and the FIV vaccination. Therefore, a positive test can often mean that vaccinated cats who are not infected are euthanized.
Ultimately, there are numerous reasons why it isn’t recommended to test feral cats for FIV/FeLV, as it is cost prohibitive as well as the numbers of positives are similar to those of owned cats. When the feral cats are sterilized, the risk of transmission is incredibly low. Feral cats live happy, healthy lives even when testing positive for FIV/FeLV, and there is no reason to deprive them of that.
Resources
Cornell Feline Health Center. “Feline Infectious Peritonitis.” Ithaca, New York: Cornell University College of Veterinary Medicine, 2014. Web. 29 Sept. 2014.
Cornell Feline Health Center. “Feline Leukemia Virus.” Ithaca, New York: Cornell University College of Veterinary Medicine, 2014. Web. 29 Sept. 2014.
Cornell Feline Health Center. “Feline Immunodeficiency Virus.” Ithaca, New York: Cornell University College of Veterinary Medicine, 2014. Web. 29 Sept. 2014.
Flowers, Amy. “Feline Leukemia Virus (FeLV) Symptoms, Vaccine, Treatment.” WebMD, WebMD, 10 Sept. 2018, https://pets.webmd.com/cats/facts-about-feline-leukemia-virus#1. 5 Dec. 2019
Levy, Julie K., and P. Cynda Crawford. “Humane Strategies for Controlling Feral Cat Populations.” Journal of the American Veterinary Medical Association 225.9 (2004): 1354–60. Avmajournals.avma.org (Atypon). Web. 18 Aug. 2014.
“PetMD, LLC.” PetMD, https://www.petmd.com/cat/conditions/infectious-parasitic/c_ct_feline_infectious_peritonitis. 4 Dec. 2019