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Update On the Occurrence of Sudden Death Following Injectable Killed Oil Emulsion Vaccines in Manitoba Turkey Breeder Hens

C.V. Mason and J.L. Neufeld

Veterinary Diagnostic Laboratory

For several years between 1990 and 1995 some turkey breeder flocks in Manitoba have experience sudden death following subcutaneous injection of killed oil emulsion vaccine products. Losses in the range of 0.5% - 1.5% of the flock would occur within one half to two hours after time of injection. Birds would either be found dead or gasping for breath and would die shortly after being observed in distress.

Initially, lack of opportunity to obtain fresh specimens precluded definitive diagnosis. Then in October 1993 a vaccination crew became concerned that a lot number of vaccine was to blame and stopped injecting. Some of these birds were examined and laboratory back up work was done. This was repeated in October 1994 with birds from the same farm.

The main findings from this group of birds were as follows:

Approximately 35 birds died within one hour of being injected. Flock size was about 3000 birds.

All birds were hens. They were in good bodily condition, with a well established abdominal fat pad. The birds were 28-29 weeks of age. This was the second oil vaccine injection. The first had been given about four weeks earlier. The vaccines involved were NDV, PMV3 and Fowl Cholera.

The most obvious lesion was in the lungs. Both lungs of all birds examined were very wet. A significant amount of reddish fluid ran out of them when placed on a paper plate. They were also very dark red in color and obviously swollen, and would not collapse when squeezed.

The crop, gizzard, and intestine contained feed.

Oil vaccine and minor hemorrhaging could be seen under the featherless skin at the side of back of the birds’ necks. Some of the injection sites were very high on the neck; some of them even occurring near the back of the head.

Bronchi were relatively clear of fluid and the trachea and mouth had no appreciable foreign material, fluid or blood clots.

1993 histological findings from H. and E. stained tissue sections lead to the suggested diagnosis of a hyper allergic reaction to repeat exposure to oil emulsion vaccine. The tissue reaction was apparently very rapid with noticeable, but very minimal cellular reaction, mostly fluid leakage into airways.

All findings were very much the same as those seen in 1993.

In addition to the above, the following was observed on gross examination:

a. There were in most birds opened a large well defined blood clot filling the air sac immediately caudal to the lungs. This clot was found to originate from the lung itself

b. Detailed examination of 9 fresh birds (examined within ½ to one hour following death) revealed that nine out of nine birds had oil vaccine deposited deeply around the jugular vein. They also had hemorrhaging immediately on the surface of the jugular vein, with one of the birds having a small drop of oil oozing from the center of a circular-shaped hemorrhage. This oil was also on the surface of the jugular vein. All injection sites were again high up on the neck on the featherless skin.

c. Close-up observation of opened jugular veins reveled needle punctures, extending through the wall of the vein, in at least eight out of nine birds examined.

Frozen sections of lung tissue were stained with Oil Red O stains.

The lung tissue had to be refrigerated over a weekend to allow for the preparation of the stain, but as shown in the sections presented, there were obvious globules of red-stained material within the interstitial vessels.

This observation lead to the more specific diagnosis of physical blockage of lung vessels due to oil embolism.

Discussions with turkey breeder companies and further history and retraining of vaccination personnel brought up the following points:

Doing subcutaneous vaccination properly at the lower portion of the back of the neck, or changing sites to the ventral surface of the tail, has greatly reduced the occurrence of this problem (one bird in 4,000 instead of 35 out of 4,200).

According to one turkey breeder company, doing the vaccinations at 22 and 26 weeks of age, instead of 24 and 28 weeks, may help to reduce the severity and number of vaccine reactions not related to technique problems. The authors are not aware of the reason for this recommendation at this time.

It has become apparent that on some occasions poor agitation and insufficient warming of vaccine before use may have contributed to the sudden death of some younger birds (10-12 weeks old). Some birds may have received high dosages of bacterial antigen due to poor mixing of vaccine.

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Last modified: 5/28/2009