Eperythrozoonosis

(365) Eperythrozoonosis is caused by a small ricketsial bacterium called Eperythrozoon suis (Epe) which attaches itself to the red cells in the blood, damaging them and causing them to break apart. This causes an anaemia associated with a reduction in the number of red blood cells and haemoglobin the substance by which oxygen is transported around the body. When large numbers of red cells are damaged, jaundice may result.

The disease is somewhat of an enigma because the organism can be identified both in normal animals and in those severely affected with disease. It is likely that Epe is very widespread and most sources of pigs examined (varying health status) have shown evidence of the bacteria.

In the majority herds where it has been identified there have been no clinical problems and the significance therefore of the organism in relation to infection in these cases must be in doubt. However, in the past two years a positive diagnosis associated with disease has become more common. Epe can cross the placenta and be responsible for poor pale pigs at birth and high pre-weaning mortality.

Clinical signs

Epe affects all classes of pigs from sows and piglets through to weaners and growers. Clinical pictures vary, particularly if there are secondary infections involved. It is useful however, to look at the clinical symptoms in acute and chronic disease. In piglets and weaners the acute disease is manifest by primary anaemia and secondary infections, whilst the more chronic picture appears related to slow growth, variable growth rate and poor-doing pigs. The chronic symptoms in sows are associated with reproductive failure and if there is stress at farrowing, fevers and agalactia may be experienced.

If pale anaemic pigs are evident during sucking or in the immediate post-weaning period and an injection of iron has been given, the possibility of Epe should be considered.

Diagnosis

The presence of the organism does not necessarily confirm disease. The following need to be considered to clarify the relationship between Epe and disease.

• The presence of pale and anaemic pigs.
• The identification of the organism in blood smears stained with Wright's stain. Fifty microscopic fields should be examined before a negative diagnosis is arrived at.
• The clinical picture on the farm should include lowered reproductive performance.
• Jaundice, particularly in young growing pigs from 7 to 21 days of age.
• Serological tests are being developed including an ELISA but at the time of writing they are still unreliable.
• Eliminate other causes of anaemia.
• Blood samples should be examined for packed cell volume (PCV) and haemoglobin levels. In normal pigs the mean PCV would be around 35% and in clinically affected pigs 24%. Haemoglobin levels would normally range from 9 to 14g per 100ml but in anaemic pigs they would be as low as 3 to 7g per 100ml.

Similar diseases

• Actinobacillus pleuropneumonia.
• Chronic respiratory disease complexed with PRRS and influenza.
• Glässer's disease - Haemophilus parasuis.
• Iron / copper anaemia.
• Leptospirosis (L. icterohaemorrhagiae and L. canicola).
• Malabsorption and chronic enteritis.
• Pale piglet syndrome - haemorrhages.
• Porcine enteropathy (PE, NE, PHE and PIA).

Treatment

Consider the following and discuss with your veterinarian:

• The response to treatment is not very good.
• Inject piglets with oxytetracycline at 10mg/kg daily for 4 days or use long-acting preparations, three injections each two days apart.
• In-feed medicate sows at 800gms/tonne of OTC for 4 weeks and repeat again 4 weeks later.
• Arsanilic acid in-feed at 85gms/tonne is reported to have an effect but in many countries there is no licensed product in food producing animals. Where it is available it is probably the medicine of choice.
• The response to other medicines is poor.

Management control and prevention

Epe suis is spread by inoculation (including inoculation by insects). In a problem herd it is important to eliminate possible methods of spread including:-

Sows

• Vaccinating sows with the same needle - Wipe the needle between inoculation with cotton wool well dampened with surgical spirit and change every third sow.
• Tagging gilts - Wash the applicators between animals or hold three pairs in an antiseptic solution and rotate.
• Eliminate lice or mange mites.
• Prevent or control fighting, vulval and tail biting etc.
• Do not feed back placenta or farrowing house material.
• Control biting insects.
• Control internal parasites.
• Wear plastic arm sleeves when attending a farrowing.

Piglets

• Spread occurs during tailing, teething and iron injections.
• Control as for sows.

Weaners and growers

• Prevent fighting at weaning. Reduce mixing.
• Prevent tail biting and vice.
• Reduce mixing and use Stresnil to prevent fighting.
• Prevent spread through vaccination and inoculations between pigs.
• Control biting insects.
• Control respiratory diseases.