30 August 1996


Any combination of over 100 factors can lead to respiratory disease. Jonathan Riley reports

WITH 16 major pathogens causing respiratory disease, preventing and treating these ailments accounts for up to 80% of a specialist pig vets time.

"Herd disease is related to the pressure put on the individual pig from exposure to diseases and environmental factors that reduce its ability to fight them off," says specialist pig vet John Carr of Garth Veterinary Group, Beeford, East Yorks.

"Anything that stresses a pig is increasing its susceptibility to disease," he adds.

Dr Carr advocates a broad and combined approach using vaccination, improved management and effective treatment use to combat respiratory disease. For example, he says that antibiotics and vaccines stored incorrectly and administered through dirty or blunt needles could be ineffective and could introduce further disease.

"Producers must consult vets to formulate a vaccination programme that is effective and economical.

"Vaccinating against enzootic pneumonia, is a major step in breaking the respiratory complex because eradication in EP-positive herds is nearly impossible by any other means. And when the lungs and windpipe are not damaged by EP they are more able to repel other pathogens," says Dr Carr.

He explains that vaccines exist for only some of the respiratory diseases but to use them all would not be cost effective. So the respiratory disease complex must be broken down by thorough appraisal of the pigs environment and appropriate action, and water, feed, stocking rates, air quality and flooring should all be checked.

"Few producers would expect poor flooring or tail biting to contribute to respiratory disease. But, broken skin can allow streptococcal bacteria to reach the lungs, producing abscesses. So a less abrasive flooring helps to minimise this type of infection," says Dr Carr.

He claims that housing often provided no adequate sleeping area and that draughts, dampness or dung in pens prevented pigs from resting which is vital for them to fight off disease.

Better zoning of pens using insulated flooring for lying areas, resiting drinkers and ensuring there are no draughts at ground level would establish a well-defined, comfortable lying area.

Pigs need adequate space because as well as increasing humidity, which facilitates disease spread, overstocking means smaller pigs are pushed into draughts or have restricted access to drinkers or feeders.

"When a pig is short of water, mucus in the lungs thickens and it cannot expel pathogens which then have a greater chance of seeding.

Dr Carr recommends that drinkers are provided at a height suitable for smaller pigs, with adequate flow rates without leaking.

"Incorrect stocking levels also affect the house temperature and even during summer, day and night time temperatures, can range from 5C to over 30C. This creates stress which can impair the immune system.

"Accurate ventilation management is vital to keep humidity between 55% and 70% and expel dust," he says.

Dr Carr advises checking ventilation rates regularly because he has found that the speed of fans, when corroded or caked with dust, can be five times lower than the speed indicated by the control panel.

"As temperatures in the building rise, rates are increased. Fans set inappropriately may create draughts, while slower fans use more electricity to clear heat, humidity and dust.

"The most damaging type of dust is the sort that shows in the beam of a high powered torch.

"All feeders should be covered and consult your nutritionist to see if there are ways of further reducing dust," he says.

The best way of exposing a units shortcomings is to use accurate performance records between buildings. When performance falls assess everything from feed quality to flooring, he adds.n

Causes of respiratory disease

In all there are at least 16 organisms which can cause respiratory disease.

&#8226 Streptococcal bacteria invade wounds and can reach the lungs – via the bloodstream – where they cause abcesses resulting in carcass condemnation or death.

&#8226 Porcine reproductive respiratory syndrome kills the alveolar macrophage – a key defence system – and exposes the pig to other diseases.

&#8226 Glassers disease is caused by Haemophilus parasuis and a number of streptococci which live in the pigs mouth. Disease occurs when pathogens colonise the pigs respiratory tract.

&#8226 Four types of swine flu in the UK can combine with other respiratory problems and lead to high losses.

&#8226 A number of respiratory parasites exist and may increase with the use of straw.

&#8226 Porcine corona virus – similar to transmissable gastroenteritis – causes a mild flu but in combination with other diseases can cause severe losses.

&#8226 Enzootic pneumonia (Mycoplasma hypopneumoniae) is present in over 70% of herds and damages the lungs causing carcass condemnation or death.

&#8226 Acute actinobacillus pleuropneumonia can devastate a grower finisher house.

Ventilation maintenance

Daily: Observe pigs. Are they too hot or too cold? Is the air damp, are there draughts? Repair leaks from drinkers and water tanks. Check temperatures in each house.

Weekly: Check back up ventilation and alarm systems, clean fan blades and shutters. Clean heater cooling fins and filters. Check feed covers and performance records.

Quarterly: Ensure fans operate as required using a strobe. Maintain shutters so that they open and close freely and clean system motors and controls.

Yearly: Clean and repaint shutters to prevent corrosion. Check air inlets for debris, compare fuel bills.

Source: Garth Veterinary Group.

Chilled pigs of all ages are more prone to respiratory disease. Draughts are a major killer and a dry, draught free lying area must be provided.

New fans work well, but after 20 years are they still as efficient?

Dirty and poorly maintained ventilation systems are as much a part of the respiratory disease complex as bacteria and viruses, says Dr John Carr.