During 2003, 278 adult pigeons (Columba livia) and 54 birds of 11 other free-living species were caught in the various locations in the City of Zagreb, Croatia. Sera from 182 pigeons were tested for the presence of antibodies against Chlamydophila (C.) psittaci by ELISA test and 174 of them (95.6%) were found positive. Because of the high positivity rate in sera, cloacal swabs of 278 pigeons as well as 54 other species of free-living birds were tested for the presence of C. psittaci antigen. Fourty-four of the 278 pigeons (15.83%) were antigen positive, whereas all 54 of the wild birds were negative. Antigen-positive pigeons were euthanised and examined pathomorphologically and cytologically. Findings of specific antibodies and antigen of C. psittaci confirmed the high rate of infection among urban pigeons in the City of Zagreb, fortunately not among other free-living birds. Although the pigeon serovars of C. psittaci are considered to be of moderate pathogenicity for humans, the identification of 15.8% antigen-positive birds represents a potential source of infection to humans, especially for elderly people and immunodeficient patients, as well as for poultry in the Zagreb city area.

In the last 3 yr, several outbreaks of avian poxviruses (APVs) have been observed in different parts of Croatia. Four strains of APVs, from chickens, a pigeon, and a turkey, were isolated from cutaneous lesions by inoculation onto the chorioallantoic membranes (CAM) of 12-day-old specific-pathogen-free chicken embryos. The resulting proliferative CAM lesions contained eosinophilic cytoplasmic inclusion bodies. The characteristic viral particles of poxvirus were detected in the infected CAM and also in the infected tissues by transmission electron microscopy. Further identification and differentiation of the four various APVs were carried out by the use of a polymerase chain reaction (PCR) combined with restriction enzyme analysis. Using one primer set, which framed a region within the APV 4b core protein gene, it was possible to detect APV-specific DNA from all four tested isolates. PCR results revealed no recognizable differences in size of amplified fragments between the different APVs from chickens, turkey, and pigeon. Restriction enzyme analysis of PCR products using NlaIII showed the same cleavage pattern for turkey and chicken isolates and a different one for the pigeon isolate. Multiplex PCR for direct detection of APV and reticuloendotheliosis virus (REV) was carried out to determine the possible integration of REV in the genome of isolated APVs. The obtained results revealed that REV was present in chicken and turkey strains of poxviruses, whereas the pigeon isolate was negative. It is not known whether the avipoxvirus vaccine strain used in Croatia is contaminated with REV or if the REV is naturally contaminating Croatian field strains of fowl poxvirus. The latter is indicated by the negative REV finding in the pigeon, which was not vaccinated. The results of the present study indicate the reemergence of fowlpox in Croatia, where infections have not been recorded since 1963 and never confirmed etiologically.

The presented experiments were aimed to cultivate and multiplicate HVT FC-126 in the PLA (Adult pig kidney) and GL-4 (Gerbil kidney) cell lines. Two different HVT FC-126 vaccine strains were used: Marikal SPF (Veterina d.o.o., Croatia) and Lyomarex (Merial, USA). They were adapted to the PLA and GL-4 cell lines. After adaptation, they were titrated on PLA (TCID50 24.23) and GL-4 (TCID50 24.96). On both cell lines they show similar CPE (cytophatic effect). The difference between them was detected using Real Time PCR, which was also positive by agarose gel analysis for the virus contained in Lyomarex, but not in the Marikal SPF. It can be concluded that both cell lines are sensitive to HVT FC-126 and the virus can be multiplied in high titers though much lower than in the calf intestinal epithelial cell line (CIEB) cells (TCID50 27.93)