Adenovirus Infection in Cats. an Epidemiological Survey in the Czech Republic

Lakatos B. , Z. Knotek, J . Farkas , É. Ádám, O. Dobay, I . Nász: Adenovirus Infection in Cats. An Epidemiological Survey in the Czech Republic. Acta Vet. Brno 1999, 68: 275-280. The widespread presence of adenoviruses in various species makes it probable that a carrier state and infection also exist in cats; this could be proved earlier. On the basis of these considerations investigations were carried out to perform an epidemiological survey in 100 randomly selected feline sera from the Czech Republic. Antibody detection was carried out in a group-specific indirect ELISA employing purified adenovirus hexon antigen. The adenovirus seropositivity was found to be 25% among the samples tested. Domestic short-haired cats (28%) and females (34%) showed increased infection rates. Among the 6 retrovirus-infected cats 3 males with outdoor access were seropositive. Cats showing respiratory and gastrointestinal symptoms gave high prevalence. These results are similar to those found in other species and feline populations and reflect on the natural adenovirus infection of cats in the Czech Republic. Feline, antibody, adenovirus Since the first isolation of adenoviruses (Rowe et al. 1953; Hil leman and Werner 1954) about 130 serotypes have been described from different mammalian and avian species (Boros et al. 1985; Mautner 1989; Russel l et al. 1995). Presence of adenoviruses has been verified by histopathology and electron microscopy (Ishibashi and Yasue 1984) in poikilotherm species, such as amphibians (Clark et al. 1973), reptiles (Jacobson 1986), and even in fish (Jensen and Bloch 1980). Adenoviruses are grouped in two genera on the basis of their origin and genus-specific antigens. The Mastadenovirus genus includes serotypes isolated from humans and mammals, while adenoviruses coming from birds belong to the Aviadenovirus genus (Russel l et al. 1995). Occurrence of mastadenoviruses has been verified by isolation and characterization in 9 mammalian species apart from the humans (Russel l et al. 1995). The actual number of adenoviruses in a given species depends rather on the effort made on isolation than on the frequency of occurrence (Wadel l 1984). Grouping of adenoviruses of animal origin is generally done after the host species, e.g. simian, canine, bovine, ovine, rabbit and so on (Bartha and Áldássy 1964; Belák and Pálf i 1974; Bodon et al. 1979; Belák 1980; Baber and Condy 1981; Ishibashi et al. 1984; Adair et al. 1986). Up till now, adenoviruses have not been isolated from cats or other Felidae, although their presence had been demonstrated. The presence of adenovirus was proved in a cat by light and electron microscopy (Kennedy and Mullaney 1993). Only one case of adenovirus infection in Felidae (black panther) was published. The suspicion of an adenovirus infection arose from the pathological changes and histopathology (Gupta 1978). On the basis of experience with other species, one can presume that subclinical infections also occur in cats. A serosurvey has been performed on samples from different European countries, where the infection rate was found to be 10-20% (Lakatos et al. 1996). Detection of adenovirus hexon gene sequences was successful from a single adenovirus seropositive cat suffering from hepatic failure (Lakatos et al. 1999). Clinical signs of a systemic adenovirus infection may be expected more frequently in cats with acquired or congenital immunodeficiency (Barker and van Dreumel 1985; Dungworth 1985). Since the host spectrum of adenoviruses is rather narrow (Timoney et al. 1988), a genuine adenovirus of cats may be expected. The feline leukaemia virus (FeLV) and the feline immunodeficiency virus (FIV) have been isolated worldwide as the causative agents of acquired immunodeficiency in cats (Matteucci et al. 1993; Beebe et al. 1994), and the occurrence of the latter virus infection has also been diagnosed in Hungary (Lakatos et al. 1992). Adenoviruses play a relevant pathological role frequently in HIV-infected humans (Sabin et al. 1999) and certain human adenovirus serotypes were isolated exclusively from patients suffering from HIV infection (Hierholzer 1992). These facts also suggest the possible existence of a genuine adenovirus in cats. In our experiments, the presence of specific antibodies to adenovirus antigens was demonstrated in cats. The aims of this study were: 1. to detect adenovirus infection in cats originating from the Czech Republic, and 2. to trace groups/populations where infection is accumulated. Materials and Methods To detect antibodies against adenovirus antigens, altogether 100 serum samples were tested. These feline sera collected from cats throughout the Czech Republic (mainly from Prague, Brno and Ostrava regions) originated from the serum bank of the Small Animal Clinic at the University of Veterinary and Pharmaceutical Sciences, Brno, Czech Republic. As history data breed, sex (male or female), age (years) of the cats, access to outdoor (kept outdoor or indoor), clinical status, the reason for clinical examination and qualitative results of the feline immunodeficiency virus (FIV), and feline coronavirus (FCoV) antibody detection and feline leukaemia virus (FeLV) antigen detection (positive or negative) were included in the study. The proportion of castrated animals was low (8%), so they were not grouped separately. FIV, FeLV and FCoV tests were performed with commercially available reagents. As adenovirus group-specific ELISA antigen purified human adenovirus type 1 (HAdV-1) hexon antigen was prepared. HAdV-1 was propagated on HEp-2 cells, and the soluble antigens were purified by repeated anion exchange chromatography on DEAE Sephadex A-50 (Pharmacia, Sweden) (Ádám et al. 1988). In indirect ELISA experiments (Lakatos et al. 1996), wells of 96-well polystyrene plates (Falcon) were coated with purified HAdV-1 hexon antigen at 20 μg/ml final concentration. The antigen, the serial dilution of sera, the biotin conjugate (BiotinantiCat, Sigma), the streptavidin-HRPO conjugate (Extravidin, Sigma), the substrate (OPD), as well as the 2 M H2SO4 used for stopping the reaction were applied in 50 μl quantities. Washing between the subsequent steps was carried out with PBS. The optical density (OD) was measured at 492 nm wavelength in an Anthos 2010 spectrophotometer. When evaluating the results 4 x OD of the negative control serum was taken as cut-off. The history data and the adenovirus serological test results were evaluated using chi-square tests and Fisher’s exact tests.