Pig

SBC Technology

Introduction
The belief is that the most effective way to control the post-weaning multi-systemic wasting syndrome – PMWS - disease is to vaccinate the pigs with traditional vaccine.
However the circovirus PCV-2 is not readily expressed at sufficient titer in any known medium or cell culture system.

A way to come by the problem is to express the PCV-2 in E.coli. The nature of the PCV-2 however makes it very difficult to express large quantities of PCV-2 proteins in E. coli.
By modifying the genomic structure of the PCV-2 sufficiently it has been possible to express the PCV2 in E-coli and - with high reproduction!

The SBC patented circovirus PCV-2 technology consists of two important elements;
- A genetic alteration technique of the virus to such an extent that it can be accepted by and expressed in E.coli.
- A unique genetic alteration technology; the significant changing of the genome in a simple and economical way.

The SBC circovirus PCV-2 PWMS technology is patented.

Field of invention
“ The invention relates to artificially altered Type II porcine circovirus (PCV-2) nucleic acid sequences which can be over-expressed in a heterologous expression system.

These artificially altered PCV nucleic acid sequences are characterized by their containing of synonymous codons of PCV-2 genes or fragments thereof, which code for peptides that are capable of inducing a protective immune response against PCV-2 in pigs.

This invention also relates to vaccines against PCV-2 and for prevention of postweaning multisystemic wasting syndrome (PMWS) in piglets. The vaccines contain one or more of peptides or fragments thereof isolated and purified from the heterologous expression system after being over-expressed with the artificially altered PCV-2 nucleic acid sequences. The preferred altered nucleic acid sequence encodes PCV-2 ORF2 coat protein or a fragment thereof.”

Summary of invention
“ The invention provides artificially altered nucleic acid sequences of Type II porcine circovirus (PCV-2) or fragments thereof, which can be expressed in a heterologous expression system with large quantity.

The proteins or polypeptides encoded by the artificially altered nucleic acid sequences or fragments thereof are capable of inducing a protective immune response against PCV-2.
The wild-type gene(s) of PCV-2 cannot be produced in a heterologous expression system with good yield.”

 

PMWS - Post-weaning Multi-systemic Wasting Syndrome

SBC has focused competence and experience in the pig sector on the difficult world wide PMWS disease.
The disease is recognized as a major problem and economic burden to the producers as there is no preventive vaccine available in the market.
The PMWS results in high morbidity and mortality.

Background
Porcine circovirus type 1 (PCV1) was first identified in 1974 and was recognized as a non-disease-causing agent that frequently occurred in laboratory tissue cultures.
In 1991, swine veterinarians in western Canada began reporting cases of nursery pigs falling ill with clinical signs that included a progressive loss of body condition, visibly enlarged lymph nodes, difficulty breathing, and less commonly diarrhea, pale skin, and jaundice. The name "post-weaning multi-systemic wasting syndrome" (PMWS) was applied to the disease.
In 1997, a new circovirus (PCV2) was isolated from these outbreaks. Since that time, researchers have been able to successfully reproduce the disease by inoculating pigs with PCV2 in the laboratory.

PMWS has now been reported from most pig-producing countries of the world. Additional PCV2-associated diseases have also been described including reproductive failure, respiratory disease in finishing pigs, and an unusual skin and kidney disease referred to as porcine dermatitis and nephropathy syndrome (PDNS).

Agent and Pathogenesis
Porcine circovirus type 2 (PCV2), is a small, non-enveloped, circular DNA virus that is only known to cause disease in pigs. Like parvovirus, PCV2 is stable in the environment and is resistant to many common disinfectants.
Most affected pigs do not recover. On farms with a history of PMWS, not all groups of pigs will show clinical signs. These numbers can vary substantially between countries.
PCV2 infection has also been suggested as a cause of reproductive failure, enteritis, and CNS disease. These syndromes are less frequently reported than PMWS, PDNS, or PRDC.

Treatment
There is no known vaccine available!
As PCV-2 is a virus, antibiotic therapy is not very helpful in preventing or treating out-breaks.
Production strategies believed to help in controlling PMWS include acclimatization of replacement animals prior to entering the herd, ensuring adequate intake of colostrum by all piglets, minimizing crossfostering activity, reducing group size, and strict adherence to all-in, all-out pig flow.

Pattern:
- Pigs of 8-12 weeks of age, although can be 5-16 weeks.
- Mortality rates vary but farms have been reported with post-weaning mortality in excess of 60% and figures of 15-25% are common.
- Persistent infection - some farms are still affected after 2 or more years and still experience similar levels of mortality.
- A further cost is that the overall growth rates and feed conversion on the farm deteriorate due to the number of debilitated pigs present.

 

Pig Diseases

Dramatic outbreaks of diseases as Swine Fewer and Foot and Mouth Disease have strongly challenged the pig industry in numerous countries time and time again.

Emerging diseases as PWMS is becoming the new and visible economic threat to the industry on a global level.

Pigs are susceptible to different respiratory, enteric and reproductive diseases primarily based on bacterial or viral infections.

Respiratory diseases
Respiratory diseases are usually contagious and can be fatal. Bacterial infections are usually treated with antibiotics, often in conjunction with vaccines. Viral infections treatment is based on vaccines, while antibiotics are used to control secondary bacterial infections.

The major bacterial pathogens are,
- Mycoplasma - causes enzootic pneumonia, seen as chronic infection in herds, affecting animals six weeks of age or older.
- Actinobacillus - causes porcine pleuropneumonia, a highly contagious and often fatal disease in growing pigs.
- Pasteurella – causes pneumonic pasteurellosis, the most common bacteria isolated from pneumonic lungs of slaughtered pigs.
- Bordetella - a common infection in swine herds and the primary lung pathogen in young pigs. The disease is called atrophic rhinitis.

The major viral respiratory diseases are,
- swine influenza
- porcine reproductive and respiratory syndrome (PRRS).
They are common and cause production losses in growing pigs and in breeding herds.

Enteric diseases
Enteric diseases occur in neonatal and suckling piglets as well as in weaned animals. Treatment of enteric diseases is based on antibiotics, which may be combined with vaccines in some cases.
- Escherichia coli – causes neonatal diarrhoea as well as for post-weaning infections, depending on the bacterial strain
- Clostridium - causes diarrhoea in suckling piglets and weaned animals, also strain dependent.
- Porcine proliferative enteropathy, also called ileitis, is caused by Lawsonia. Mild chronic infections in growing pigs, while an acute haemorrhagic form is more common in finishing pigs and young adults.
- Swine dysentery, due to Brachyspira, is an important problem in weaned pigs.
- Clinical outbreaks of colitis, caused by Brachyspira pilosicoli, are observed in weaners and growers.
- Salmonellosis affects pigs of all ages and its role in food safety draws increasing attention from the consumer side.
- Leptospirosis and parvovirus infections gives reproductive disorders that lead to infertility, abortion and stillbirth in sows.

Other important diseases
- Glasser's disease is due to Haemophilus and can be fatal. Symptoms are polyarthritis, polyserositis and meningitis
- Streptococcus causes septicaemia, arthritis, meningitis and bronchopneumonia in piglets, growers and finishers.
- Post-Weaning Multi-systemic Wasting Syndrome (PWMS) associated with Porcine Circovirus Type-2, affects predominantly eight to twelve week old pigs.