Željko Gottstein

Epidemiological investigation of Chlamydophila psittaci in pigeons and free-living birds in Croatia.

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.

Immunogenicity and Safety of Queensland V4 and Ulster 2C Strains of Newcastle Disease Virus Given to Maternally Immune, Newly Hatched Chickens by Nebulization

Abstract Commercial chickens with a high level of maternal antibodies for Newcastle disease were vaccinated when newly hatched with Queensland V4 or Ulster 2C Newcastle disease virus (NDV) strains by nebulization. The exposure time to a fine aerosol of vaccine produced with an ultrasonic nebulizer was 60 sec. The chickens were challenged oculonasally with virulent NDV strain Texas GB in weekly intervals up to the 49th day of life. Although protected for several weeks by maternal antibody, they were sufficiently protected thereafter by active immune response to the vaccines. Vaccinal reactions were not observed. Queensland V4 produced higher titers than Ulster 2C and provided better protection to challenge.

Progress in Chlamydia psittaci vaccine development in poultry

Chlamydia psittaci, depending on its serovar, can infect humans, birds, and other animals and livestock. Its economic impact on poultry production, especially on turkeys and chickens, and potential zoonotic risk have driven the search for an effective vaccination protocol to prevent and control the infection and shedding of the organism. Currently, no vaccine is approved for use against avian chlamydiosis despite efforts in the past decades. The present genomic era presents an opportunity to establish an effective vaccination scheme, taking advantage of the major outer membrane protein (MOMP) as the major protective antigen of C. psittaci. The plasmid DNA expressing MOMP can be coupled with optimisation of controllable factors during vaccination such as codon optimisation (through formation of polyplexes and lipoplexes), route of administration, vaccination schedule, addition of adjuvants/co-stimulatory factors such as cytokines and CpG motifs, and recombination with other poultry pathogens such as viruses. The development of an effective vaccine against C. psittaci will protect susceptible poultry from infection and production performance losses and reduce the zoonotic risk and minimise the emergence of antibiotic-resistant C. psittaci strains.

Multiplication of HVT FC-126 (Herpesvirus turkey) virus in the kidney cell lines of no avian origin

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 2^4.23) and GL-4 (TCID50 2^4.96). 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 2^7.93).