Risk factors for highly pathogenic H7N1 avian influenza virus infection in poultry during the 1999-2000 epidemic in Italy.

In 1999-2000, Italian poultry production was disrupted by an H7N1 virus subtype epidemic of highly pathogenic avian influenza (HPAI). The objectives of the present study were to identify risk factors for infection on poultry farms located in regions that had the highest number of outbreaks (Veneto and Lombardia) and the impact of pre-emptive culling as a complementary measure for eradicating infection. A Cox regression model that included spatial factors, such as the G index, was used. The results confirmed the relationship between risk of infection and poultry species, production type and size of farms. The effectiveness of pre-emptive culling was confirmed. An increased risk of infection was observed for poultry farms located near an infected farm and those at altitudes less than 150m above sea level. The measures for the control and eradication of AI virus infection need to consider species differences in susceptibility, the types of production and the density of poultry farms in the affected areas.

The 1999-2000 avian influenza (H7N1) epidemic in Italy: veterinary and human health implications.

From the end of March to the beginning of December 1999, 199 outbreaks of low pathogenicity avian influenza (LPAI) were diagnosed in the Veneto and Lombardia regions, which are located in the northern part of Italy. The virus responsible for the epidemic was characterized as a type A influenza virus of the H7N1 subtype of low pathogenicity. On the 17th of December, highly pathogenic avian influenza (HPAI) was diagnosed in a meat turkey flock in which 100% mortality was observed in 72 h. The infection spread to the industrial poultry population of northern Italy including chickens, guinea-fowl, quail, pheasants, ducks and ostriches for a total of 413 outbreaks. Over 13 million birds were affected by the epidemic, which caused dramatic economic losses to the Italian poultry industry with severe social and economic implications. The possibility of H7 virus transmission to humans in close contact with the outbreaks was evaluated through a serological survey. Seven hundred and fifty nine sera were collected and tested for the detection of anti-H7 antibodies by means of the micro-neutralization (MN) and single radial haemolysis (SRH) tests. All samples resulted negative. A limited number of clinical samples were also collected for attempted virus isolation with negative results. Current European legislation considers LPAI and HPAI as two completely distinct diseases, not contemplating any compulsory eradication policy for LPAI and requiring eradication for HPAI. Evidence collected during the Italian 1999-2000 epidemic indicates that LPAI due to viruses of the H7 subtype may mutate to HPAI, and, therefore, LPAI caused by viruses of the H5 or H7 subtypes must be controlled to avoid the emergence of HPAI. A reconsideration of the current definition of avian influenza adopted by the EU, could possibly be an aid to avoiding devastating epidemics for the poultry industry in Member States.

Rabies and canine distemper virus epidemics in the red fox population of northern Italy (2006-2010).

Since 2006 the red fox (Vulpes vulpes) population in north-eastern Italy has experienced an epidemic of canine distemper virus (CDV). Additionally, in 2008, after a thirteen-year absence from Italy, fox rabies was re-introduced in the Udine province at the national border with Slovenia. Disease intervention strategies are being developed and implemented to control rabies in this area and minimise risk to human health. Here we present empirical data and the epidemiological picture relating to these epidemics in the period 2006-2010. Of important significance for epidemiological studies of wild animals, basic mathematical models are developed to exploit information collected from the surveillance program on dead and/or living animals in order to assess the incidence of infection. These models are also used to estimate the rate of transmission of both diseases and the rate of vaccination, while correcting for a bias in early collection of CDV samples. We found that the rate of rabies transmission was roughly twice that of CDV, with an estimated effective contact between infected and susceptible fox leading to a new infection occurring once every 3 days for rabies, and once a week for CDV. We also inferred that during the early stage of the CDV epidemic, a bias in the monitoring protocol resulted in a positive sample being almost 10 times more likely to be collected than a negative sample. We estimated the rate of intake of oral vaccine at 0.006 per day, allowing us to estimate that roughly 68% of the foxes would be immunised. This was confirmed by field observations. Finally we discuss the implications for the eco-epidemiological dynamics of both epidemics in relation to control measures.

Vaccination reduced the incidence of outbreaks of low pathogenicity avian influenza in northern Italy.

When outbreaks of avian influenza (AI) occur in poultry populations, the main goal to achieve is the control and eradication of the infection. However, quantitative information on risk factors for AI spread and efficacy of AI control measures such as vaccination in the field is limited. From 2000 to 2005, H5 and H7 low pathogenicity (LP) AI viruses caused four epidemics in poultry in northeastern Italy. Italian veterinary authorities implemented emergency vaccination in the 2000-2001 and 2002-2003 LPAI epidemics and prophylactic vaccination from July 2004. The aim of this study is to quantitatively evaluate the efficacy of AI vaccination in the field, taking into account the different strategies (emergency and prophylactic) implemented. Moreover, risk factors for LPAI spread in domestic poultry were studied. By survival analysis, we observed a two-fold increase in survival probability for vaccinated poultry farms compared to unvaccinated ones. In meat turkeys, vaccination protocols changed in the different epidemics, and a relationship between protection and the number of vaccinations was observed; two or three vaccine administrations protected flocks from LPAI, whilst four administrations did not significantly reduce the risk of infection. In meat turkeys the risk of AI infection increased also with the increase in both farm size and proximity to an infected farm. In general, we observed a lower number of outbreaks and a faster eradication of the infection when LPAI viruses introduced in a preventively vaccinated poultry population. This study provides insights on LPAI vaccination efficacy and on risk factors involved in LPAI infection at farm level. To our knowledge, this is the first study which quantitatively evaluates AI vaccination efficacy and compares different vaccination strategies and protocols using field data.