In 2018, Croatia reported the largest outbreak of West Nile virus (WNV) infections as well as the re-occurrence of human Usutu virus (USUV) infections. For the first time, fatal WNV and USUV infections were detected in wild birds. We analysed epidemiological characteristics and molecular epidemiology of WNV and USUV infections detected during 2018 transmission season. From April to November, 178 patients with neuroinvasive disease and 68 patients with febrile disease were tested for WNV and USUV. Viral RNA was detected in cerebrospinal fluid (CSF) and urine samples using a real-time RT-PCR. Positive samples were tested by nested RT-PCR and nucleotide sequencing. IgM/IgG antibodies were detected in serum/CSF samples using ELISA | 1947 VILIBIC-CAVLEK Et AL.

This study describes the introduction and spread of avian influenza A (H5N1) subtype in Croatia. Seventeen isolates were identified during the period from October 2005 to March 2006, all originating from wild birds. The full-length nucleotide sequence analysis of the hemagglutinin (HA) gene of seven representative isolates revealed that three distinct genetic strains involved in the outbreaks, implicating at least three independent introductions of the virus into Croatia during a relatively short period of time. All three genetic strains belonged to clade 2.2 (Qinghai-like viruses) and each strain displayed significant similarity to concurrent H5N1 viruses from other European countries. The dominant strain of the virus was present in all four affected areas and in all three bird species (mute swan, mallard, and black-headed gull), indicating cross-species transmission of the virus. Two other genetic strains were found, together with the dominant strain, only in a marsh at the Adriatic coast during late February and early March 2006, which could be associated with frozen water surfaces in the continental part of Croatia as well as in Eastern Europe in early 2006 and the movement of birds toward warmer areas. This is also the first isolation of highly pathogenic avian influenza virus of H5N1 subtype from apparently healthy black-headed gulls.

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Microbiological composition of air, as a factor of ambient conditions in animal facilities can significantly influence performance, health and animal welfare in the swine production. The aim of this investigation was to determine, by monitoring primary microclimatic conditions, the possible association of the number of fattening pigs per unit of housing space with species diversity and number of airborne microorganisms. The research was conducted at a fattening and finishing facility of 450 m 2 (equipped with 44 pens designed for 10 animals each) with low-pressure ventilation in three different trials. The first trial was conducted during the autumn-winter period with the capacity of 440 animals (0.7 m 2 of pen area per fattening pig), the second trial was conducted during the winter-spring period with 356 animals (0.8 m 2 of pen area per fattening pig), and the third trial was conducted during the spring-summer period with 312 animals (1.0 m 2 of pen area per fattening pig). The air samples for isolation of fungi and mesophilic, haemolytic, and coliform bacteria were taken and microclimatic conditions were monitored during each trial at the same consecutive weekly periods. According to the data obtained from all trials, the total number of bacteria and fungi did not exceed 10 4 and 10 3 CFU per m 3 , respectively. The most numerous were gram-positive bacteria, followed by gram-negative bacteria and fungi. The total number of airborne microorganisms correlates significantly (at p < 0.05) with porcine housing density. These data may be useful for the assessment of housing density at fattening facilities that will not compromise swine health and welfare regarding the microbiological air quality, and thus may contribute to the implementation of optimal rearing conditions in large-scale animal producing units.

As immune responses to live and inactivated vaccines might differ, temporal responses of broiler chickens to vaccination were examined on the basis of the abundance in the circulating blood of gene transcripts of IFN-α, IFN-γ and IL-2, critical cytokines for immune responses. Blood samples were collected 6, 12 and 24 hours, and 7 and 14 days following vaccination with either live or inactivated Newcastle disease virus, La Sota strain, at 14 days of age, and the abundance of transcripts for each cytokine was assayed by real-time RT-PCR. Physiological saline and vaccine emulsion without viral antigen were administered to control groups for live and inactivated vaccine groups, respectively. The abundance of IFN-γ transcripts was elevated during the early times following vaccination and had reached baseline by the seventh day but the abundance of IFN-α transcripts remained elevated. Transcripts for neither IFN gene were detected in the control birds. The abundance of transcripts for each IFN was not different between the two vaccinated groups at any time. Transcripts for IL-2 were detected only in spleens from chicken embryos that had been inoculated with the live virus. The results show that cells stimulated to produce IFN-α and IFN-γ enter the circulating blood but those stimulated to produce IL-2 do not, or in very low number, and the IFN responses to both vaccines are the same.