Feline leukaemia virus infection: A clinical and epidemiological enigma

September 09, 2020

Feline leukaemia virus (FeLV) is a gammaretrovirus that occurs worldwide in domestic cats, as well as small wild cats. It is associated with various serious, and sometimes fatal, diseases including anaemia, immunosuppression and certain cancers. First described over 55 years ago, FeLV has been the subject of intense research interest, which has led to increasingly robust diagnostic assays and efficacious vaccines. While the prevalence of this infection in domestic cats has reduced in many geographic regions, the disease is still something of an enigma and can spread quickly, particularly within naïve 'multi-cat' populations such as shelters and breeding catteries, as well as within pet homes with multiple cats. An important goal in order to reduce the prevalence further is understanding the FeLV status of every cat at risk of infection.

A state-of-the-art Premier Review published in the Journal of Feline Medicine and Surgery this month aims to contribute diagnostic expertise to veterinarians in practice by reviewing recent insights into infection pathogenesis, gained using molecular techniques.1 Writing for an international audience of veterinary practitioners and feline researchers, Professors Regina Hofmann-Lehmann, of the University of Zurich, Switzerland, and Katrin Hartmann, of LMU Munich, Germany, explain that not only are there several different outcomes of FeLV infection, but that these can vary over time. Newly classified as 'progressive', 'regressive', 'focal' and 'abortive' infection, the authors describe how it can be helpful to think of these outcomes in terms of a set of balance scales, with the cat's immune response on one side and the virus on the other.

From an epidemiological point of view, it is the progressively infected cat that is most significant. In these infections, the virus has the upper hand - these cats shed high numbers of FeLV particles and pose an infection risk to other cats. Regardless of their health status, progressively infected cats need to be kept apart from FeLV-naïve companions. From a clinical point of view, progressively infected cats are a priority too: they are at high risk of succumbing to potentially fatal disease; though, if well cared for, many can continue to live a healthy and happy life, sometimes for years.

Of the other possible outcomes, abortive infection is the most favourable for the cat - these cats have strong anti-FeLV immunity. Regressively infected cats will have developed a partially effective antiviral immune response that can keep the virus in check; however, they probably never clear the infection completely, and can shed virus, and thus pose an infection risk, in the early phase of infection or if reactivation occurs. In focal infection, which is comparatively rare, the cat's immune system keeps viral replication sequestered in certain tissues.

When it comes to FeLV testing, seemingly perplexing or 'discordant' test results are not uncommon, particularly in the early phase of infection, and can pose considerable challenges for the practitioner needing to establish the FeLV status and implement appropriate therapeutic and epidemiological measures. The authors discuss the most frequently used methods for FeLV detection, including free FeLV p27 antigen testing, viral RNA testing and FeLV provirus testing, focusing on when to test and how to interpret a positive or a negative result. The detection of anti-FeLV antibodies, including a point-of-care test for FeLV p15E introduced recently onto the European market, is also discussed. A diagnostic algorithm produced by the European Advisory Board on Cat Diseases (ABCD) that provides guidance on which test to choose in which scenario is incorporated within the review article.

As well as being expert members of the ABCD, both authors were members of an expert panel for recently published consensus guidelines from the American Association of Feline Practitioners (AAFP) on feline retrovirus testing and management,2 and together the guidelines and review article present the current state of knowledge about this potentially deadly virus. Discussing their ambition for their article, Professors Hofmann-Lehmann and Hartmann comment: 'We hope that this review will not only increase awareness of this fatal but preventable disease, but also help veterinarians in clinical practice when diagnosing this remarkable but tricky infection'.
-end-
References

1. Hofmann-Lehmann R and Hartmann K. Feline leukaemia virus infection: a practical approach to diagnosis. J Feline Med Surg 2020; 22: 831-846. Read for free at: https://journals.sagepub.com/doi/abs/10.1177/1098612X20941785

2. Little S, Levy J, Hartmann K, et al. 2020 AAFP feline retrovirus testing and management guidelines. J Feline Med Surg 2020; 22: 5-30. Read for free at: https://journals.sagepub.com/doi/abs/10.1177/1098612X19895940

SAGE

Related Immune Response Articles from Brightsurf:

Boosting chickens' own immune response could curb disease
Broiler chicken producers the world over are all too familiar with coccidiosis, a parasite-borne intestinal disease that stalls growth and winnows flocks.

Cells sacrifice themselves to boost immune response to viruses
Whether flu or coronavirus, it can take several days for the body to ramp up an effective response to a viral infection.

Children's immune response more effective against COVID-19
Children and adults exhibit distinct immune system responses to infection by the virus that causes COVID-19, a finding that helps explain why COVID-19 outcomes tend to be much worse in adults, researchers from Yale and Albert Einstein College of Medicine report Sept.

Which immune response could cause a vaccine against COVID-19?
Immune reactions caused by vaccination can help protect the organism, or sometimes may aggravate the condition.

Obesity may alter immune system response to COVID-19
Obesity may cause a hyperactive immune system response to COVID-19 infection that makes it difficult to fight off the virus, according to a new manuscript published in the Endocrine Society's journal, Endocrinology.

Immune response to Sars-Cov-2 following organ transplantation
Even patients with suppressed immune systems can achieve a strong immune response to Sars-Cov-2.

'Relaxed' T cells critical to immune response
Rice University researchers model the role of relaxation time as T cells bind to invaders or imposters, and how their ability to differentiate between the two triggers the body's immune system.

A novel mechanism that triggers a cellular immune response
Researchers at Baylor College of Medicine present comprehensive evidence that supports a novel trigger for a cell-mediated response and propose a mechanism for its action.

Platelets exacerbate immune response
Platelets not only play a key role in blood clotting, but can also significantly intensify inflammatory processes.

How to boost immune response to vaccines in older people
Identifying interventions that improve vaccine efficacy in older persons is vital to deliver healthy ageing for an ageing population.

Read More: Immune Response News and Immune Response Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.