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Atrophic Rhinitis (AR)

See also chapter 9.

(355) Rhinitis is inflammation of the tissues inside the nose and in its mild form it is very common. Progressive atrophic rhinitis (PAR) however is a serious condition both in sucking and growing pigs. The term atrophy indicates that the tissues inside the nose, which become infected or damaged, shrink and become distorted. There are two forms of the disease: mild and non-progressive where the infection or irritation occurs over a period of 2 to 3 weeks. The inflammation does not progress and structures in the nose called turbinate bones repair and return to normality.

The serious disease is progressive atrophic rhinitis (PAR) where toxin producing strains of the bacterium Pasteurella multocida, cause a continual and progressive inflammation and atrophy of the tissues and nose distortion. All herds will show some degree of non-progressive atrophic rhinitis, the inflammation being of short duration. Organisms such as bordetella, haemophilus, non toxigenic pasteurella, other environmental organisms and dust or gases can produce this type of rhinitis in the nose.

For a herd however, to have PAR toxigenic pasteurella must be present. They are carried in the nose and tonsils of the adult pig and there is always the risk therefore of buying them into the herd. This is the most common method of entry.

Clinical signs

They include sneezing, runny eyes, discharges from the nose sometimes containing blood and early signs of distortion of the face, with shortening or twisting of the upper jaw becoming evident at weaning time. It is important also to appreciate that sneezing is a common occurrence in the sucking pig and need not necessarily be associated with PAR. PAR affects most of the piglets present. However, individual piglets may also develop distortion of the nose from trauma or some other cause but this is not PAR.

Diagnosis

This is carried out by:

  • The clinical signs in the sucking piglets and nasal distortion in growing pigs.
  • Sectioning the snout of pigs at slaughter and examining the degree of turbinate damage in the nose.
  • Isolating the organism from sucking or rhinitic pigs by swabbing the nostrils and submitting to a specialist laboratory for examination.
Similar diseases

The most common would be non progressive rhinitis and sneezing caused by cytomegalo virus, bordetella and haemophilus organisms or environmental irritants. A significant differentiating feature here is that if these organisms are causing sneezing in the sucking pigs then by 4 weeks after weaning sneezing will have disappeared with no facial distortions.

Treatment

  • Once toxigenic pasteurella have been identified the complete breeding herd should be immediately vaccinated six weeks apart using a vaccine made from toxigenic pasteurella. It takes approximately four months for a total herd immunity to develop and it may be nine months or more before the disease is brought completely under control. In the early stages of a herd breakdown the following could be recommended:
  • In-feed medicate sows with trimethoprim/sulpha or sulphadimidine from point of entry into the farrowing house through to weaning. (500g/tonne)
  • Inject all piglets with 0.25 to 0.5ml of long-acting OTC or amoxycillin on days 3, 10 and 15 during sucking.
  • Inject pigs similarly at weaning time with 0.5 to 1ml of long-acting antibiotic. This treatment programme should continue for a period of at least 2 months after all sows have been fully vaccinated.
  • Medicate the creep rations with OTC or CTC 800g/tonne or trimethoprim/sulpha combinations for 4 weeks post-weaning.
  • Sows should be given a booster dose of vaccine 2 to 3 weeks prior to each subsequent farrowing.
Management control and prevention

Management can play an important part in controlling the disease. If there is a problem in the herd consider the following predisposing factors:

  • Disease is more common in young herds particularly those containing large numbers of gilts.
  • Large permanently populated farrowing houses are ideal for the maintenance and spread of disease therefore split the houses into small modules of 6-10 crates only.
  • Operate an all-in all-out system with pressure washing and disinfection between batches.
  • If multi suckling is practised then convert this to single suckling. The more pigs noses that make contact with each other the greater is the spread of disease.
  • Make sure that divisions between farrowing pens are solid and at least 0.6m high to reduce the risk of droplet infection.
  • Outdoor rearing reduces the risk of PAR.
  • Poor ventilation and low humidity together with dusty atmospheres and toxic gases predispose to the disease.
  • Poor colostrum management or udder problems such as agalactia result in piglets with poor immunity.
Eradication

It is possible by vaccination, segregated early weaning or segregated disease control, to eradicate the organisms from a breeding weaning herd. This is carried out by vaccinating the sows and after approximately 12 months of vaccination and no evidence of clinical disease, a segregated disease control programme is carried out as discussed in chapter 3.

Problems however arise in the breeding finishing unit where the organism persists in the continually populated finishing houses and it is necessary to depopulate the weaning, growing and finishing houses. Total herd depopulation and repopulation is also successful.

2012年 5月 30日 星期三

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