Piglet wasting disease (PWD)

Present in most pig-producing countries today, piglet wasting disease (PWD) emerged in North America and Europe at the same time in 1996.

PWD affects piglets aged 7 to 15 weeks old with the first signs being a fever and loss of appetite. These signs are accompanied by breathing difficulties and sometimes diarrhoea, leading, in severe cases, to the animal wasting away (weight loss) and in certain cases dying. The triggering of severe forms of the disease varies considerably according to the farm and the animals within the same farm.

In sick animals, lesions are observed on different organs (lungs, liver, kidney, lymph nodes, etc.). Viral research conducted on damaged organ tissue has revealed the presence of a widespread virus within pigs worldwide: porcine circovirus type 2 (PCV2). After more than ten years of research, only swine (pigs and wild boars) and birds have been identified as circovirus hosts to date. These viruses have never been found in humans.

All circoviruses are associated with diseases that affect the immune system by provoking a reduction in the number of lymphocytes (a variety of white blood cells playing a role in the immune response) in their hosts.Numerous animals may be infected without presenting any clinical signs, however.

While this virus is currently considered to be one of the major causes of PWD, its presence in a farm is not enough by itself to trigger the disease. Other environmental factors also contribute to the expression of PWD in farms.

The impact of PWD has considerably reduced in France over recent years thanks to the implementation of measures mainly associated with farming techniques (improved hygiene conditions, fewer stressful situations for animals).

ANSES’s activities relating to piglet wasting disease

The ANSES Ploufragan/Plouzané laboratory conducts research activities on this disease, particularly to understand the role of sow vaccination (against parvovirus/Erysipelothrix rhusiopathiae) on the development of PWD in progeny. It also studies the dynamics of PCV2 circulation in farms.

The laboratory also conducts research on the virus (PCV2) itself:

• development of a method for quantifying the genome of the virus in real time;
• in vitro and in vivo characterisation of PCV2 in an infectious clone;
• establishment of tests to identify the non-infectious cofactors which may promote infections by the circovirus (immunostimulation of piglets infected with PCV2);
• study of the role of PCV2 in PWD by a method using DNA microarrays;
• study of PCV2 virulence factors by introducing a mutation into the virus’s capsid protein gene.