PhD Thesis Demeter Zoltan

The incubation period before the onset of clinical signs is usually 4-5 days, and
the clinical course can rapidly progress to death. Due to virus properties and needs, the
primary pathologic site for viral replication is within the intestinal crypts, resulting in
enteritis and diarrhea due to malabsorption and increased permeability (Lamm &
Rezabek, 2008). The virus affects cells located deep in the intestinal crypts, while
differentiated absorptive cells on the surface of the villi are non-dividing and are not
affected. Thymic atrophy and extensive damage to all white blood cell populations and
precursors, resulting in severe leukopenia are also common consequences of FPV
infections (Greene & Addie, 2006).
Co-infections with other pathogens, such as Clostridium piliforme (Tyzzer’s
disease) and salmonellae have also been reported (Greene & Addie, 2006). Secondary
infections caused by other bacteria are also considered to be common findings (Lamm
& Rezabek, 2008).
3.2.3 Clinical signs
The number of animals that develop clinical signs is significantly lower than the number
of infected animals. This fact is supported by the high prevalence of FPV antibodies in
the cat population. Severe clinical illness is the rule in young, unvaccinated kittens, and
the highest morbidity and mortality occurs between 3 to 5 months of age (Greene &
Addie, 2006). FPV has also been demonstrated in young purebred kittens that died
suddenly, without clinical signs suggestive of FP (Addie et al., 1998). In these peracute
cases cats may die within 12 hours, as if poisoned. They may be found in terminal
stages of septic shock, being profoundly dehydrated, hypothermic and comatose
(Greene & Addie, 2006). In the more frequent acute form of the disease the clinical
signs are represented by fever, depression, anorexia, vomiting, extreme dehydration,
and sometimes in the later stages, diarrhea and hypothermia. Clinical signs suggestive
of DIC, such as petechial and ecchymotic hemorrhages, are also common. Animals that
survive infection for longer than 5 days without developing fatal complications usually
recover, although recovery frequently takes several weeks (Greene & Addie, 2006).
FP causes infertility and abortion if the infection occurs during pregnancy. These
females however never show clinical signs suggestive of FP. Kittens infected in utero
may develop ataxia, incoordination, tremors, and normal mental status typical of
cerebellar disease. Retinal degeneration is also a relatively common finding in affected
kittens (Greene & Addie, 2006).
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