Postweaning multisystemic wasting syndrome
Encyclopedia
Postweaning multisystemic wasting syndrome ("PMWS") is a disease
seen in domestic pig
s. This disease causes illness in piglets, with clinical signs including progressive loss of body condition, visibly enlarged lymph node
s, difficulty in breathing, and sometimes diarrhea
, pale skin, and jaundice
. PMWS has been reported from most pig-producing countries of the world at huge cost to agriculture
. PMWS is caused by porcine circovirus type 2 (PCV2).
type 2 (PCV2). However, the exact relationship between PCV2 infection and PMWS remains unclear. There is not a straightforward relationship between infection and disease. PCV2 has a near universal distribution – present in most pig herds. In contrast, PMWS is more sporadic in its distribution. Experimental induction of PMWS has not been achieved by PCV2 infection alone, using infectious DNA
clones of the virus or a pure form of PCV2 derived from infectious DNA clones. Therefore it is assumed that PMWS is a multifactorial disease. PCV-2 is necessary but not sufficient for the development of PMWS. There is no significant correlation of the disease with virus sequence variation with affected and control pigs.
and nephropathy
syndrome (PDNS) are associated to PCV2. Many pigs affected by the circovirus also seem to develop secondary bacterial infections, like Glässer disease (Haemophilus parasuis), pulmonary pasteurellosis, colibacilosis, salmonellosis and others. Dissected morbid pigs showed lesion
s in multiple organs, especially in lymphoid tissues, giving rise to the term "multisystemic".
Wasting pigs is the most common sign of PMWS infection, increasing the mortality rate significantly.
These measures have recently been expanded upon by Dr. David Barcellos, a professor at the Veterinary College in the Universidade Federal do Rio Grande do Sul, Rio Grande do Sul
, Brazil
. He presented these points at "1st Universidade Federal do Rio Grande do Sul Symposium about swine management, reproduction, and hygiene".
He divided his points by pig growth stage, and they can be loosely summarized as:
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
seen in domestic pig
Domestic pig
The domestic pig is a domesticated animal that traces its ancestry to the wild boar, and is considered a subspecies of the wild boar or a distinct species in its own right. It is likely the wild boar was domesticated as early as 13,000 BC in the Tigris River basin...
s. This disease causes illness in piglets, with clinical signs including progressive loss of body condition, visibly enlarged lymph node
Lymph node
A lymph node is a small ball or an oval-shaped organ of the immune system, distributed widely throughout the body including the armpit and stomach/gut and linked by lymphatic vessels. Lymph nodes are garrisons of B, T, and other immune cells. Lymph nodes are found all through the body, and act as...
s, difficulty in breathing, and sometimes diarrhea
Diarrhea
Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...
, pale skin, and jaundice
Jaundice
Jaundice is a yellowish pigmentation of the skin, the conjunctival membranes over the sclerae , and other mucous membranes caused by hyperbilirubinemia . This hyperbilirubinemia subsequently causes increased levels of bilirubin in the extracellular fluid...
. PMWS has been reported from most pig-producing countries of the world at huge cost to agriculture
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...
. PMWS is caused by porcine circovirus type 2 (PCV2).
PMWS & PCV2
PMWS is associated with infection of pigs by porcine circovirusPorcine circovirus
Porcine circovirus is a single-stranded DNA virus , that is nonenveloped with an unsegmented circular genome. The viral capsid is icosahedral and approximately 17 nm in diameter. PCV is a member of the virus family Circoviridae....
type 2 (PCV2). However, the exact relationship between PCV2 infection and PMWS remains unclear. There is not a straightforward relationship between infection and disease. PCV2 has a near universal distribution – present in most pig herds. In contrast, PMWS is more sporadic in its distribution. Experimental induction of PMWS has not been achieved by PCV2 infection alone, using infectious DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
clones of the virus or a pure form of PCV2 derived from infectious DNA clones. Therefore it is assumed that PMWS is a multifactorial disease. PCV-2 is necessary but not sufficient for the development of PMWS. There is no significant correlation of the disease with virus sequence variation with affected and control pigs.
Clinical Signs
Both PMWS and porcine dermatitisDermatitis
-Etymology:Dermatitis derives from Greek derma "skin" + -itis "inflammation" and genetic disorder.-Terminology:There are several different types of dermatitis. The different kinds usually have in common an allergic reaction to specific allergens. The term may describe eczema, which is also called...
and nephropathy
Nephropathy
Nephropathy refers to damage to or disease of the kidney. An older term for this is nephrosis.-Causes:Causes of nephropathy include administration of analgesics, xanthine oxidase deficiency, and long-term exposure to lead or its salts...
syndrome (PDNS) are associated to PCV2. Many pigs affected by the circovirus also seem to develop secondary bacterial infections, like Glässer disease (Haemophilus parasuis), pulmonary pasteurellosis, colibacilosis, salmonellosis and others. Dissected morbid pigs showed lesion
Lesion
A lesion is any abnormality in the tissue of an organism , usually caused by disease or trauma. Lesion is derived from the Latin word laesio which means injury.- Types :...
s in multiple organs, especially in lymphoid tissues, giving rise to the term "multisystemic".
"The distinguishing lesion caused by PCV2 is an inflammatory infiltration by histocite cells with variable intensity, located in the lymphoid organs, liver, kidney, and lung"
Wasting pigs is the most common sign of PMWS infection, increasing the mortality rate significantly.
Management practices to decrease severity of PMWS
François Madec, a French author, has written many recommendations on how reduce PMWS symptoms. They are mostly measures for disinfection, management, and hygiene, referred to as the "20 Madec Points" [Madec & Waddilove, 2002].These measures have recently been expanded upon by Dr. David Barcellos, a professor at the Veterinary College in the Universidade Federal do Rio Grande do Sul, Rio Grande do Sul
Rio Grande do Sul
Rio Grande do Sul is the southernmost state in Brazil, and the state with the fifth highest Human Development Index in the country. In this state is located the southernmost city in the country, Chuí, on the border with Uruguay. In the region of Bento Gonçalves and Caxias do Sul, the largest wine...
, Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
. He presented these points at "1st Universidade Federal do Rio Grande do Sul Symposium about swine management, reproduction, and hygiene".
He divided his points by pig growth stage, and they can be loosely summarized as:
- keep the gutters clean
- increase feeder space
- use pens or small cages with solid dividers
- avoid mixing pigs from different origins
- improve the quality of air
- decrease maximum capacity, giving each pig more room
- separate sick animals as soon as possible, and treat them in a hospital pen. If they do not respond to antibiotics in three days, they should be culled
- control access of people and other animals
- reduce invironmental stress factors such as gases and air currents
- use immunizations and preventive medications for secondary agents commonly associated with PMWS