Transmission and Pathogenesis of Feline Panleucopenia

How does feline panleukopenia spread?

Feline panleukopenia virus (FPV) is a non-enveloped virus (non-enveloped virus, non-enveloped virus). Non-enveloped viruses are more resistant to physical factors and chemicals than enveloped viruses. Unenveloped viruses have excellent heat resistance and can easily withstand harsh conditions in the gastrointestinal tract, including the strong acidity of gastric juice and the strong alkalinity of bile. Therefore, intestinal infections are often caused by these viruses. They can also survive certain disinfection processes. Essentially, this means that these viruses remain alive and infectious under these harsh conditions. FPV can survive for several months in an outdoor environment, and even more than a year in a suitable environment. In addition to the survival time, FPV has frost resistance and can survive for half an hour at high temperatures above 56 °C, and alcohol and iodophor have no effect on it.

Sensitive animals

Susceptible animals are mainly kittens, especially kittens that are not vaccinated or fully immunized, and kittens that are not nursing. The former did not obtain adequate FPV protection from the vaccine, while the latter did not obtain maternal antibody (MDA) protection from breast milk.

Source of infection

Cats infected with FPV, especially those with clinical symptoms, can detoxify through feces, urine, saliva, vomit, etc. Infected cats can detoxify the outside world through their feces for up to 6 weeks. Viruses can accumulate rapidly in affected environments. Because FPV is highly contagious, susceptible animals can still be infected even with surfaces that are thoroughly disinfected. Therefore, isolation or entry into such an environment is only recommended for cats that have been successfully vaccinated and provided adequate protection against FPV.

Propagation mode

Susceptible animals are primarily infected with FPV through direct contact with infected animals, or through oral or respiratory contact with contaminated feed, drinking water, utensils, and the surrounding environment. In addition, FPV can also be transmitted vertically through the placenta and mechanically through arthropods.

Pathogenesis of feline panleukopenia virus

Feline panleukopenia virus (FPV) causes systemic infection. The virus is transmitted by the fecal-oral route, replicating initially in oropharyngeal tissue and then spreading to nearly all tissues by acellular viremia. FPV requires replication in rapidly dividing and proliferating S-phase cells, which are typically found in mitotically active tissues. FPV binds to the transferrin receptors (TFRs) of these tissue cells and uses these receptors to enter and infect cells. Tissues with active mitosis include: intestinal crypt epithelium, lymphoid tissue, bone marrow, etc. Depending on the location of the affected cells, the corresponding tissue will undergo pathological changes, resulting in corresponding clinical manifestations.

FPV infects lymphoid tissue, potentially leading to cellular exhaustion and functional immunosuppression. Lymphopenia may be due to lympholysis or indirectly due to lymphocyte migration into tissues. The bone marrow is affected, and viral replication occurs in progenitor cells, with marked effects on nearly all bone marrow cell populations, resulting in a deficiency of all leukocyte populations, termed "panleukopenia."

A hallmark of FPV replication is shortening of intestinal villi. The virus replicates in rapidly dividing cells within intestinal crypts, disrupting the regeneration of intestinal epithelial cells, resulting in shortened intestinal villi. Severity correlates with epithelial cell turnover, and co-infection with other enteroviruses (eg, feline coronavirus) may also increase disease severity. Intrauterine transmission of FPV or perinatal infection may affect central nervous system development. "Feline ataxia syndrome" is a result of a lytic infection of Purkinje cells in kittens, resulting in impaired cerebellar development.