FeLV-A enters the oropharynx during mutual grooming. It spreads to most tissues of the body, notably the bone marrow (B cells, megakaryocytes macrophages), thymus (T cells), salivary glands, and reproductive tract and replicates for 2 weeks then…………….
Most adult cats remain healthy and develop antibody after clearing the virus.
Kittens and about 30% of adult cats become viraemic for life without antibody. In a survey; 20% of such viraemic cats died of tumours and 30% died of FeLV-associated diseases (see later) within one year. 80% died within 3 years.
Some cats, maybe 30%, intermittently excrete virus from the bone marrow. Such excretion becomes when stressed in a boarding cattery, why?