Country Vet - Enzootic pneumonia

Enzootic Pneumonia is a descriptive term covering diseases resulting in consolidation (collapse) of the apical and cardiac regions of the lung. Classically, this is due to Mycoplasma hyopneumoniae, together with various streptococci and pasturella. Today any condition that damages the lung can lead to Mycoplasmal pneumonia, with the change from a subclinical to clinical condition being dependent upon the severity of damage.

Enzootic Pneumonia is commonly seen in growing and finishing pigs. It can cause clinical disease in growers, especially where an underlying problem is present. It is also common in a gilt herd, where pigs are naïve terms of immunity, to the pathogen.

There are a number of bacteria and mycoplasma which can infect the lung, particularly after Enzootic Pneumonia has commenced. These include pasturella, streptococci and Actinobacillus pleuropneumoniae. Haemophilus parasuis (Glasser's Disease) can also play a contributing role in post-weaning respiratory disease.

There are a number of viruses that can initially cause damage to the lung. Infection by viruses is usually facilitated by damage to the lung through dust and inadequate ventilation.

There are a number of factors that contribute to Enzootic Pneumonia, which come under the domain of the manager and stockpersons.

Air - excessive temperature fluctuations, draughts and inadequate ventilation
Floor - overstocking (reduced air space per pig) and rough floors
Water - poor water flow, and insufficient drinkers
Feed - dry, dusty feed and poor feed availability

When pigs have had sufficient exposure to the pathogen and have gained some immunity, Enzootic Pneumonia usually remains as a subclinical disease. In this case, its major effects on production are in terms of growth rate and feed conversion efficiency. When there is low immunity or an initiating factor, clinical disease develops. Clinical sings include:

The disease can move via the air up to a distance of 5kms, but this is usually in cold environments. In Australia, the distance may be reduced. On infected farms, the disease is transferred from a sow/gilt to her offspring and more importantly, by droplet spread from coughing pigs (up to 4 metres).

Depending on the extent, Enzootic Pneumonia can reduce daily liveweight gain by 17%, and increase feed conversion by 14%. In other cases, it can also cause death.

Mycoplasmas graze on cilia (hairs) on the trachea and bronchi (windpipe). The cilia protect the lung from dust and bacteria. When cilia are destroyed, infection of the lung occurs, leading progressively to collapse of the lung and the pig becomes short of air. As well as other diseases occurring concurrently, strain is placed on the heart (as it needs to pump more oxygenated air around the body), and the pig dies of cardiac failure.

Mycoplasmal pneumonia control and treatment is complicated. In Enzootic Pneumonia negative herds, maintenance of an Enzootic Pneumonia herd requires much planning due to the relatively easy spread of the disease.

In Enzootic Pneumonia positive herds, eradication is difficult both practically and economically, as herds can be re-infected quickly.

When introducing new stock it is important to ensure that they gain some immunity to the disease, but do not develop clinical signs. Should they develop the clinical condition, they will actually act as a focus of infection for the rest of the herd.

1. Management and environmental improvements which can greatly assist in the reduction of stress factors, such as stocking density and ventilation.

2. Gilt management, ensuring that naïve stock are appropriately introduced into a situation where high antigenicity is present (as previously mentioned).

To achieve reasonable control of Enzootic Pneumonia, a total commitment is required, utilising herd management and appropriate medication.