Chapter 7: Feline Leukemia Virus and Feline Immunodeficiency Virus, 2nd Edition 2 CE Hours
Expiration Date : February 4, 2029 Course overview This course is intended for veterinarians in general practice and the animal shelter setting. This course provides a comprehensive overview of feline leukemia virus (FeLV) and Learning objectives After completing this course, the learner will be able to: Summarize the epidemiology and pathophysiology of feline leukemia virus. Summarize the epidemiology and pathophysiology of feline immunodeficiency virus. Interpret diagnostic testing results for feline leukemia virus.
feline immunodeficiency virus (FIV), including recent updates from the American Association of Feline Practitioners’ 2020 FeLV/FIV management guidelines.
Interpret diagnostic testing results for feline immunodeficiency virus. Explain to clients the lifestyle management strategies for cats infected with FeLV and/or FIV. Explain an effective vaccination strategy for cats infected with FeLV and/or FIV. State the strategies for prevention of FeLV/FIV for clients.
INTRODUCTION
between cats, whereas FIV is most frequently spread through bite wounds. The two viruses also differ significantly in key aspects of diagnosis, because there are variations in test methodology and in the feline immune response to the two viruses. Finally, there are significant differences in treatment and prevention strategies for FeLV and FIV viruses. Feline leukemia vaccines are commercially available and recommended for all at-risk cats. In contrast, FIV vaccination has not been available in the United States since 2016; even when vaccines were previously available, there were numerous caveats and limitations associated with vaccination.
Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) are among the most common viral illnesses of cats. These two retroviruses have numerous similarities. First, both viruses have the potential to induce tumor formation in infected cats. Additionally, both FeLV and FIV are known to suppress the immune system. Finally, both viruses are unstable in the environment; they require transmission through bodily fluids, either vertically or horizontally. Although there are significant similarities between FeLV and FIV, there are also key differences between these two viruses. First, the two viruses differ in transmission; feline leukemia virus is often spread through close contact
FELINE LEUKEMIA VIRUS
this RNA virus inserts a DNA copy of its genome into the host cell. This allows for continued viral replication. Other well-known examples of retroviruses in veterinary and human medicine include feline immunodeficiency virus (FIV) and human immunodeficiency virus (HIV).
Feline leukemia virus (FeLV) is a single-stranded RNA retrovirus with worldwide distribution. Feline leukemia virus is both an oncogenic (tumor-producing) virus and an immunosuppressive virus. It is capable of replication in a variety of feline tissues, including bone marrow, salivary glands, and respiratory epithelium. As a gamma retrovirus, Epidemiology of FeLV According to a 2006 study of 18,038 cats in veterinary hospitals and animal shelters, the estimated overall FeLV prevalence in the United States is 2.3% (Levy, 2006). The prevalence of FeLV is higher in sick cats than it is in healthy cats, and variation has also been observed based on geographic location. Feline leukemia can be transmitted both horizontally (between close contacts) and vertically (from mother to offspring). Infected cats shed feline leukemia virus primarily in the saliva, although urine, feces, and milk also contain the virus (Hofmann-Lehmann, 2016). Horizontal transmission of FeLV typically occurs through close contact between two cats. Feline leukemia is often described as a disease of “friendly” cats; in many cases, it is passed through mutual grooming. This virus is unstable in the environment and dies within minutes; therefore, FeLV cannot be readily transmitted via fomites. Sharing food bowls and litterboxes may theoretically allow transmission, if
two cats use these items in rapid succession, but this mode of transmission is typically regarded as uncommon and not a significant contributor to FeLV transmission (Lister, 2015a). Feline leukemia virus can also be spread vertically, from mother to offspring. In many cases, infected pregnant queens suffer reproductive losses and do not carry their kittens to term. If their pregnancy does survive to term, however, the kittens are frequently born viremic for FeLV. This can result in a number of different outcomes. Many viremic kittens fade quickly, experiencing death early in life (American Association of Feline Practioners, 2013). However, up to 20% of kittens born with FeLV may survive to adulthood with persistent infection. In addition to in utero infections, kittens may also be infected after birth, through the queen’s milk while nursing or via the queen’s saliva during grooming (AAFP, 2013). Both transplacental and transmammary transmission play a role in the vertical transmission of FeLV.
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