Feline panleukopenia (FPL) is an infectious viral disease caused by the feline panleukopenia virus (FPV). This pathogen is a small, non-enveloped single-stranded DNA virus belonging, together with closely related canine parvovirus type 2 (CPV-2), to the
Feline panleukopenia virus and CPV-2 are defined as one single taxonomic entity (37). The feline virus was discovered at the beginning of the 20th century and recognised as one of the main pathogens responsible for feline viral diarrhoea (14). The canine virus emerged as a dog pathogen in the late 1970s and rapidly spread worldwide (36). It is believed that CPV-2 evolved as a host-range variant of FPV that adapted to certain other hosts among the Carnivora (minks and foxes) through changes in five or six amino acid positions in the capsid protein (34). Unlike FPV, which has exhibited a certain degree of genetic stability (11), CPV-2 has shown a high rate of genomic substitution comparable to that of RNA viruses (40). The original CPV-2 has been completely replaced by three antigenic variants (CPV-2a, 2b and 2c) with changes within the
An estimated 90% of a protoparvovirus virion is made up of viral protein 2 (VP2), which is an integral component of the capsid protein (35). This protein is a critical component of the virion that determines the antigenic properties, host range and receptor binding of FPV and CPV-2. Sequence analysis of the
The original CPV-2 isolates were not able to replicate in cats. However, changes in amino acids not only enhanced the binding of CPV-2-derived variants to canine cellular receptors but also affected the replication ability of the virus in cats (16, 23, 24). Moreover, CPV-2-derived strains can cause disease in cats with clinical signs similar to FPL but a generally milder course than that seen in cats infected with FPV (27, 38, 39).
Carnivore parvoviruses are likely to spread freely and rapidly in environments where only a low number of cats and dogs have been vaccinated against FPV or CPV-2. Initially, the only prophylactic intervention available against FPV or CPV-2 comprised inactivated or live attenuated virus vaccines, which proved to be ineffective long-term (33). Since CPV-2a and -2b strains seem to have advantages over conventional FPV in cats, it is possible that CPV-2a and -2b will replace FPV as the dominant parvoviruses of domestic cats even in developed countries where FPV vaccines are commonly used (18). Monitoring of parvoviruses is important because the continuous prevalence of viral infection might be associated with the emergence of new virulent strains, and the distribution of new variants poses a threat to domestic animals (dogs and cats) (2, 29). Knowledge of the current situation of pathogen occurrence is important particularly for epidemic control and preventive measures (33). This study aimed to determine the presence of CPV-2 in cats with signs of FPL in Slovakia and to investigate the suitability of a CPV antigen test for detection of FPV.
The study was conducted on samples from central Slovakia collected from October 2020 to December 2022. Cats were either from animal shelters or admitted to veterinary clinics for treatment because they presented FPL symptoms.
A total of 59 cats, 17 European shorthairs and 42 crossbreds, of different ages and both sexes were included in this study. Cats were divided into three groups, of which the first group (n = 21) consisted of cats showing symptoms of FPL (such as fever, lethargy, vomiting and diarrhoea), the second group (n = 29) comprised cats in close contact with parvovirus-infected animals but without clinical signs and the third group (n = 9) was a group of clinically healthy cats enrolled as the control group. Detailed clinical information of the animals involved in this study is presented in Table 1.
Detailed clinical information on cats from central Slovakian animal shelters or veterinary clinics with signs of feline panleukopenia
Group | Sample ID | Breed | Sex | Age | FPV vaccination | Anamnesis |
---|---|---|---|---|---|---|
I. clinical signs (n = 21) | 1 | crossbreed | female | 3 months | no | vomiting, diarrhoea |
2 | crossbreed | male | 3 months | no | vomiting, diarrhoea, lethargy | |
3 | crossbreed | female | 2 months | no | vomiting, diarrhoea, fever | |
4 | ESH | female | 6 months | no | lethargy, anorexia, fever | |
5 | ESH | female | 5 months | no | lethargy, anorexia | |
6 | crossbreed | female | 2 months | no | vomiting, diarrhoea | |
7 | crossbreed | male | 3 months | no | vomiting, lethargy | |
8 | crossbreed | female | 3 months | no | lethargy, fever | |
9 | crossbreed | female | 3 months | no | vomiting, diarrhoea, fever | |
10 | ESH | female | 3 years | no | lethargy, fever | |
11 | crossbreed | female | 4 months | yes | vomiting, lethargy, fever | |
12 | ESH | female | 3 years | no | vomiting, lethargy, anorexia | |
13 | crossbreed | male | 7 months | no | vomiting, lethargy, fever | |
14 | crossbreed | male | 6 months | no | diarrhoea, fever, vomiting | |
15 | crossbreed | male | 5 years | yes | diarrhoea | |
16 | ESH | male | 3 months | no | vomiting, lethargy, fever | |
17 | ESH | male | 5 months | no | vomiting, lethargy, fever, diarrhoea | |
18 | crossbreed | male | 5 months | no | vomiting, lethargy, fever | |
19 | ESH | male | 6 months | no | vomiting, lethargy, fever | |
20 | crossbreed | male | 1 year | no | vomiting, diarrhoea | |
21 | crossbreed | male | 3 months | no | diarrhoea, vomiting | |
II. close contact with parvovirus-infected animal (n = 29) | 1 | crossbreed | female | 4 years | yes | healthy |
2 | crossbreed | female | 6 months | no | healthy | |
3 | crossbreed | male | 4 months | no | healthy | |
4 | crossbreed | female | 4 years | yes | healthy | |
5 | crossbreed | female | 5 years | yes | healthy | |
6 | ESH | female | 2 years | no | healthy | |
7 | ESH | female | 1 year | no | healthy | |
8 | ESH | female | 4 years | yes | healthy | |
9 | crossbreed | male | 5 years | yes | healthy | |
10 | ESH | female | 4 months | no | diarrhoea | |
11 | crossbreed | female | 3 months | no | diarrhoea | |
12 | crossbreed | male | 2 months | no | diarrhoea | |
13 | crossbreed | female | 3 months | no | diarrhoea, vomiting | |
14 | crossbreed | male | 3 months | no | healthy | |
15 | ESH | female | 1 year | no | healthy | |
16 | crossbreed | male | 5 months | no | healthy | |
17 | crossbreed | male | 2 years | yes | healthy | |
18 | crossbreed | male | 2 years | yes | intermittent diarrhoea | |
19 | crossbreed | female | 5 months | no | diarrhoea, overcame FPL | |
20 | ESH | female | 5 years | no | healthy | |
21 | crossbreed | male | 2 years | yes | intermittent diarrhoea | |
22 | crossbreed | female | 4 months | no | healthy | |
23 | ESH | female | 2 years | no | healthy | |
24 | crossbreed | female | 1 year | no | healthy, overcame FPL | |
25 | crossbreed | male | 1 year | yes | healthy | |
26 | crossbreed | female | 5 months | no | diarrhoea, overcame FPL | |
27 | crossbreed | male | 4 months | no | vomiting | |
28 | crossbreed | female | 3 years | yes | healthy | |
29 | crossbreed | female | 6 months | no | healthy, overcame FPL | |
III. clinically healthy (n = 9) | 1 | ESH | male | 1 year | yes | healthy |
2 | ESH | female | 2 years | yes | healthy | |
3 | crossbreed | male | 7 months | yes | healthy | |
4 | crossbreed | female | 3 years | yes | healthy | |
5 | crossbreed | male | 3 months | yes | healthy | |
6 | crossbreed | male | 5 months | yes | healthy | |
7 | crossbreed | female | 1 year | yes | healthy | |
8 | crossbreed | female | 2 years | yes | healthy | |
9 | ESH | male | 1 year | yes | healthy |
ESH – European shorthair; FPL – feline panleukopenia
Swabs were collected in duplicate directly from the rectum using cotton swabs. One swab was used immediately for rapid antigen testing and the other was stored at room temperature for further processing.
Cats were initially screened for the presence of parvovirus antigens using a chromatographic immunological antigen (Ag) test for CPV and canine coronavirus (CCV) (Rapid CPV/CCV Ag test; Bionote, Gyeonggi-do, South Korea) according to the manufacturer’s instructions.
All samples were investigated for parvovirus infection by PCR targeting the
A total of 23 rectal samples (38.9%, 23/59) were confirmed to be antigen positive in the antigen test (Table 2). The tests indicated 100% positivity in all cats with clinical signs of parvovirus infection (21/21). Among the group of cats in close contact with parvovirus-infected animals, parvovirus infection was confirmed in two individuals (6.89%, 2/29). No cat from the clinically healthy group was detected to be antigen positive (0/9). A summary is presented in Table 3.
Antigen-based detection of parvovirus infection in rectal swab samples of European shorthair and crossbred cats in central Slovakia grouped by feline panleukopenia status
Group | Sample ID | CPV antigen test |
---|---|---|
I. clinical signs (n = 21) | 1–21 | + |
II. close contact with parvovirus-infected animal (n = 29) | 1–9; 11–26; 28, 29 | - |
10, 27 | + | |
III. clinically healthy (n = 9) | 1–9 | - |
CPV – canine parvovirus; + – positive result; - – negative result
Summary of parvovirus infection findings in rectal swab samples of European shorthair and crossbred cats in central Slovakia grouped by feline panleukopenia status
Groups | CPV antigen test | PCR test | Total positive | ||
---|---|---|---|---|---|
Ag+ | Ag- | PCR+ | PCR- | ||
I. clinical signs (n = 21) | 21 | 0 | 21 | 0 | 21 (100%) |
II. close contact with parvovirus-infected animals (n = 29) | 2 | 27 | 2 | 27 | 2 (6.89%) |
III. clinically healthy (n = 9) | 0 | 9 | 0 | 9 | 0 |
Ag+ – parvovirus infection clinically confirmed by commercial antigen test for canine parvovirus (CPV) and canine coronavirus Ag- – parvovirus infection clinically excluded by commercial antigen test; PCR+ – parvovirus infection confirmed by PCR PCR- – parvovirus infection excluded by PCR
Samples were also examined for parvovirus infection by PCR based on the presence of the
Analysis of the representative FPV sequence (PP209372) in BLASTn revealed 99.78–100% pairwise identity with FPV and excluded CPV-2 infection (Table 4).
Sequences producing significant alignments with the
Scientific name | Pairwise identity (%) | Query coverage (%) | GenBank accession number |
---|---|---|---|
Feline panleukopenia virus | 100.00 | 100 | MK671185.1, MK671183.1, MK671171.1, MK671170.1, MK671156.1, MK425504.1, MK425500.1, MK425499.1, MK425498.1, MK425497.1, KP019621.2, MG764511.1, MG764510.1, MF541133.1, MF541132.1, MF541119.1, KX685354.1, KX900570.1, KT240130.1, KT357491.1, OP796716.1, OP796714.1, KP682520.1, KP019617.1, OM638042.1, MW091486.1, MW091487.1, MZ712026.1, MZ322607.1, MZ357122.1, MZ357120.1, MZ357119.1, MW017627.1, MT270583.1, MW331496.1, MN419003.1, MT274378.1, HQ184201.1, FJ936171.1, DQ474238.1, DQ474237.1, DQ474236.1, EU221281.1, AY606131.1, DQ099430.1, AY955826.1, DQ003301.1, AB054227.1, AB054226.1, AB054225.1 |
Feline parvovirus | 100.00 | 100 | MK266790.1, MK266788.1, MK295775.1, OM885375.1, ON646210.1, MZ442303.1, OR211675.1 |
Feline panleukopenia virus | 99.78 | 100 | OQ863619.1, OQ863618.1, OQ863617.1, OQ863615.1, MZ508524.1 |
Feline parvovirus | 99.78 | 100 | OR198066.1, OQ869254.1, OQ868569.1, OQ868568.1, OQ868566.1, OQ868565.1, OQ868564.1, OQ868562.1, OQ868554.1, OQ868553.1, OQ868552.1, OQ868550.1, OQ868548.1, OQ868547.1, OQ868542.1, OQ868536.1, OQ868535.1, OQ868534.1, OR194134.1, OR194132.1, OR194130.1, OR194129.1, OR194128.1, OR194125.1, OR194122.1, OQ535514.1, OQ535513.1, OQ535511.1, OQ535510.1, OQ535509.1 |
Disease killed 2 of the 23 animals which were antigen and PCR positive for parvovirus infection, which represents an 8.69% mortality rate.
Although cats were not the host for the original CPV-2, the newer CPV-2 antigenic types have acquired the ability to replicate in cats (18). Feline disease caused by CPV-2-derived variants manifests clinical signs similar to those of disease caused by FPV. This implies that more studies are needed to know the true prevalence and significance of CPV-2 in cats worldwide. Many studies demonstrated the prevalence of CPV-2 infection in cat populations over a wide geographical range. In Vietnam and Taiwan, the virus was found in more than 80% of cats presumed to be infected with FPV (17), whereas in Germany, it was only detected in 10% of parvovirus-carrying cats (38). In contrast, other authors have detected CPV-2 strains in the faeces of clinically healthy animals (9, 26, 28). A study by Balboni
The relatively high observed parvovirus prevalence rate (38.9%, 23/59) in a relatively small group of animals could be connected to the lack of vaccination against FPV infection, since 91.3% of the positive-testing cats were unvaccinated (21/23). Neither of two cats in contact with a parvovirus-infected animal was vaccinated. However, two cats with confirmed feline panleukopenia were vaccinated. This can be explained by reports showing that protective immunity is not achieved in a significant proportion of cats (12, 32). A further example of immunisation failing in a notable proportion of kittens is the research by Dawson
According to Jacobson
This study provides baseline epidemiological data for future prevention and control measures against parvovirus infection and highlights the need for cat vaccination programmes against feline panleukopenia. However, further studies performed on a larger number of animals are necessary to confirm the data’s implications.