Characterization of an unusual Salmonella phage type DT7a and report of a foodborne outbreak of salmonellosis.

Salmonella enterica subsp. enterica serovar 4,[5],12,i:- is a monophasic variant of Salmonella Typhimurium and its occurrence has markedly increased in several European countries in the last ten years. In June 2011, an outbreak of Salmonella 4,[5],12,i:- was reported among attendees of a wedding reception in the North-East of Italy. The source of this outbreak was identified as a cooked pork product served during the wedding reception. All Salmonella isolates from humans and the contaminated pork products were identified as Salmonella 4,[5],12,i:- and phage typed as DT7a. Afterwards, the farm where the pigs were raised was identified and sampled, and Salmonella Typhimurium was isolated from swine fecal samples. Despite the difference in serovar, these Salmonella Typhimurium isolates were also phage typed as DT7a. In the present study, Salmonella isolates from animals, humans and pork products during the outbreak investigation were subtyped by pulsed-field gel electrophoresis (PFGE), Multiple-Locus Variable number tandem repeats Analysis (MLVA), and resistance patterns, aiming to identify the most suitable subtyping methods to characterize isolates associated with this outbreak. In addition, a collection of epidemiologically unrelated strains of Salmonella 4,[5],12,i:- and Salmonella Typhimurium sharing the same phage type (DT7a) was similarly characterized in order to investigate their genetic relationship. This study provides a first snapshot of a rare Salmonella phage type, DT7a, associated with both Salmonella 4,[5],12,i:- and Salmonella Typhimurium. Moreover, the study demonstrated that in this specific context MLVA could be a reliable tool to support outbreak investigations as well as to assess the genetic relatedness among Salmonella isolates.

Field evidence of the efficacy of vaccination to control low pathogenicity avian influenza in meat turkeys.

This paper analyzes the efficacy of vaccination to control low pathogenicity avian influenza outbreaks using information collected during four epidemics occurring in Italy between 2000 and 2005. Different vaccination strategies and protocols for meat-turkey immunization are also considered.

Low pathogenicity avian influenza in Italy during 2007 and 2008: epidemiology and control.

Since 1999, the Italian poultry production system has experienced several outbreaks of avian influenza (AI), mainly located in northeastern Italy. This paper describes the low pathogenicity (LP) AI outbreaks detected during the surveillance activities implemented in 2007-08. From May to October 2007, ten rural and hobby poultry farms were infected by an LPAI virus of the H7N3 subtype. In August-October 2007, the H7N3 LPAI virus was introduced into the industrial poultry sector with the involvement of six meat turkey farms. Phylogenetic analysis of the hemagglutinin gene indicated that all but one of the H7N3 virus strains had a high level of homology (98.7%-99.8%). Furthermore, in August 2007, an LPAI H5N2 virus was identified in a free-range geese and duck breeder flock. The hemagglutinin and neuraminidase genes showed a high level of homology (99.8% and 99.9%, respectively) with H5N2 LPAI viruses isolated from mallards in July 2007 in the same area, suggesting a possible introduction from the wild reservoir. All the birds (in total 129,386) on the infected poultry farms were culled. The prompt implementation of AI control measures, including the enforcement of a targeted emergency vaccination plan, allowed the rapid eradication of infection. In 2008, three LPAI viruses (two H7N1 and one H5N1) were identified in dealer/rural farms. The surveillance activity implemented in this area allowed the prompt detection of LPAI viruses of the H5 and H7 subtypes in the rural sector, which, as observed in the 2007 epidemic, might be the source of infection for industrial poultry.

Emergency response following suspicion of an avian influenza outbreak.

The management of a suspected index case of highly pathogenic avian influenza (AI) is crucial to the subsequent actions aimed at limiting the spread of infection and ultimately in prompt eradication of the virus. In this study, the legislative basis, basic concepts and actions behind a successful disease management programme are reviewed. These include actions at local veterinary headquarters and at farm level which must be coordinated centrally to ensure the flow of information essential to decision making. The success of any emergency intervention strategy is dependent upon the level of preparedness, including action plans to source manpower, equipment and on the degree of communication between relevant parties. Availability of information on the successes and failures in field outbreak management, will inevitably result in improved AI control worldwide.

Avian influenza in Italy 1997-2001.

From 1997 to 2001, Italy has been affected by two epidemics of high-pathogenicity avian influenza. The first epidemic was caused by a virus of the H5N2 subtype and was limited to eight premises in backyard and semi-intensive flocks. The prompt identification of the disease was followed by the implementation of European Union (EU) directive 92/40/EEC and resulted in the eradication of infection without serious consequences to the poultry industry. The 1999-00 epidemic was caused by a virus of the H7N1 subtype that originated from the mutation of a low pathogenic virus and resulted instead in a devastating epidemic that affected industrially reared poultry, culminating in the infection of 413 flocks. The description of the epidemics and the result of the control policies are reported.

Low-pathogenicity avian influenza (LPAI) in Italy (2000-01): epidemiology and control.

In 1999-2000, Italy was affected by the most severe avian influenza (AI) epidemic that has ever occurred in Europe. The epidemic was caused by a type A influenza virus of the H7N1 subtype, which originated from the mutation of a low-pathogenicity (LP) AI virus of the same subtype. From August to November 2000, 4 months after the eradication of the highly pathogenic (HP) AI virus, the LPAI strain re-emerged and infected 55 poultry farms mainly located in the southern area of Verona province (Veneto region). To supplement disease control measures already in force, an emergency vaccination program against the disease was implemented in the area. Vaccination was carried out using an inactivated heterologous vaccine (A/chicken/Pakistan/1995-H7N3). In order to establish whether LPAI infection was circulating in the area, regular serological testing of sentinel birds in vaccinated flocks and a discriminatory test able to distinguish the different types of antineuraminidase antibodies (anti-N1 and anti-N3) were performed. Shortly after the beginning of the vaccination campaign (December 2000 to March 2001), the H7N1 LPAI virus emerged again, infecting 23 farms. Among these, only one vaccinated flock was affected, and infection did not spread further to other vaccinated farms. The data reported in the present paper indicate that the combination of biosecurity measures, official control, and vaccination can be considered successful for the control of LPAI infections in densely populated poultry areas.

A study of the progress of the Aujeszky's disease control programme in Italy using survival analysis.

A 3-year study (1997-2000) was performed on 294 swine herds from Italy, where a National Programme of Control of Aujeszky's Disease (AD) based on compulsory vaccination has been operative since 1997. Aim of the study was to evaluate the progress of this control programme using a survival approach applied to gE-seropositive herds at the beginning of the programme. The cumulative proportion of herds still gE-seropositive at the end of the study was 0.57. No significant difference in the probability of becoming gE-seronegative during the study period was found between herds of different type (breeding versus farrow-to-finish) whereas significant differences were seen between herds from different areas. The Cox's proportional hazards regression, performed on data from 79 herds, showed that the only risk factor significantly associated with a higher probability of becoming gE-seronegative is again the geographical location. Other risk factors considered in the analysis were: type of enterprise, type of replacement of animals, herd size, pig and pig herds densities around the farm, distance from the nearest pig herd and year of beginning of the vaccination with a gE-deleted vaccine.

Newcastle disease outbreaks in Italy during 2000.

Among the consequences of the epidemic of highly pathogenic avian influenza which affected Italy between 1999 and 2000 was an epidemic of Newcastle disease in northern and central Italy. It affected industrially reared poultry, dealer flocks and backyard flocks, with a total of 254 outbreaks notified up to December 31, 2000. Virological investigations yielded virulent isolates of Newcastle disease virus, which produced intracerebral pathogenicity indices ranging from 1.6 to 2.0 and which, on the basis of their monoclonal antibody binding patterns, could be classified as belonging to group C1. The clinical, gross and microscopical findings were typical of Newcastle disease, and different avian species were susceptible to different degrees. Chickens and guinea fowl appeared to be the most susceptible, followed by pheasants, turkeys and ostriches. The epidemiological inquiry highlighted the crucial role of a broiler hatchery in initiating the epidemic, and of dealers in perpetuating it. The control measures imposed by Directive 92/66/EEC are discussed with reference to the outbreaks in backyard flocks.

Bovine herpesvirus 1 (BHV1) seroprevalence in the breeding cattle population of the Veneto region: prospects for the implementation of a control programme.

The results of a serological survey for bovine herpes virus (BHV1) antibodies in the breeding cattle population of the Veneto region are presented. The data do not support the hypothesis of an high prevalence of BHV1; on farms where vaccination was not carried out most animals were seronegative, and seropositive animals were generally older. Therefore, when drawing up the guidelines for a control programme, systematic immunization (with glycoprotein E-deleted vaccines) should be restricted only to farms with a high prevalence of BHV1 antibodies and/or with a high risk of BHV1 occurrence; in most unvaccinated farms a 'test and removal' policy appears to be more appropriate in order to rapidly eradicate BHV1 from the entire stock.

A case-control study on bovine tuberculosis in the Veneto Region (Italy).

A case-control study was undertaken to provide information about the role of some husbandry practices and farm characteristics in the epidemiology of bovine tuberculosis in the Veneto Region. Twenty-seven breeding herds where a positive result to the single intradermal cervical tuberculin test was confirmed by post-mortem examination were compared with seventy-four herds which had been free of the disease for at least three years. Epidemiological information was collected on farms. The factors taken into account in the study were chosen on the basis of their epidemiological plausibility and of the local livestock characteristics. Multiple logistic regression was applied to analyse the data. Factors identified as possibly involved in increasing the risk of bovine tuberculosis in the Veneto Region were the presence of mixed (dairy and beef) enterprises (OR = 4.9, P = 0.001) and of cattle purchase (OR = 5.8; P = 0.003). Other factors (such as herd size, housing system, summer mountain pasture, possible contact with wild animals, and indirect contacts with other herds) did not appear to significantly contribute to tuberculosis presence in this area. The results of this case-control study support the hypothesis that in the Veneto Region bovine tuberculosis infection is still associated with classical risk factors both (directly or indirectly) related to cattle movements.