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Author(s): Segalés, Joaquim
Publication Date: January 1, 2006
Country: Canada

Summary:

The objective of the present review is to describe the nowadays situation of PMWS in Europe and to compare it with that of late 90s and beginning of 2000s, when major outbreaks of disease were diagnosed. Speculation on the effect of the implemented control and prevention strategies on PMWS evolution is discussed. Since a centralized database on PMWS occurrence is not available at a European level, some of the information given in this review is based on personal observations, discussions and information given by veterinarian colleagues throughout Europe. Countries in Europe can be divided into five main different categories in regards to PMWS at present (adapted from Segalés, 2006): Countries in which the impact of the disease has been or it is still severe or very severe, countries in which, despite describing cases of PMWS, the disease does not seem to represent a major problem, or it is absent nowadays, countries that have reported PMWS cases but have no data to establish how important the disease is in their respective swine populations, countries that have never reported the disease, although surveillance systems have been implemented and finally, countries with unknown PMWS status. The prevalence and incidence of PMWS in most significant pig producing countries has decreased during the last 3-4 years. Some factors that may explain the lower number of PMWS diagnoses are: Veterinarians have learnt how to clinically diagnose or suspect the disease much better that in the past, so they do not confirm the diagnosis with laboratory analyses, both veterinarians and farmers have learnt to “live together” with higher rates of postweaning mortality, so the same levels of mortality that in the past deserved laboratory analyses do not deserve them today, laboratory diagnostic submissions have been limited to those cases where a reasonable doubt regarding “to be or not to be” PMWS exists or to those where the objective is only to rule out PMWS. In fact, herds affected by PMWS rarely return to postweaning mortality rates existing before the first detection of the disease, in the opinion of a significant proportion of veterinarians. Therefore, it would not be surprising that a more enzootic form of PMWS (not so easy to diagnose as before, from a clinical point of view), with lower levels of mortality and less severe clinical signs, is nowadays present in those countries that first experienced severe outbreaks of disease. Common sense indicates that the best way to control a viral infection would be using vaccines if such products were available. However, only one PCV2 vaccine is currently commercially available and in use under special license in France, Germany and Denmark, indicating that most European countries still demand a vaccine product to control the disease. PMWS is defined as a multi-factorial disease that involves infection of pigs with PCV2 and the influence of infectious and non-infectious factors or triggers for the development of clinical disease (Segalés et al., 2005). The most studied co-factors and triggers in relation to disease progression or protection are: The implementation of the Madec’s 20-point plan (a list of management measures to lower the impact of the disease), control of concurrent viral and bacterial infections in the postweaning area, the induction of clinical disease following immunostimulation in conventional pigs reared under commercial conditions, an increase in the nutrient density of young pig diets and addition of commercial feed additives, also, subcutaneous injection of PCV2 hyperimmune sera from commercial slaughterhouse age pigs in suckling or nursery pigs. Field observations from farmers and veterinarians suggested that certain genetic lines of pigs were more or less susceptible to PMWS, and PCV2 vaccination. Definitively, many different measures have been implemented across European countries and an overall significant improvement has been noted from the point of view of disease evolution. However, it is rather difficult to establish the specific measure(s) that helped to diminish the impact of the disease in Europe. Moreover, normal disease evolution (epizootic to enzootic scenarios) may have played a role independently of those measures.

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