Slow Bee Paralysis Virus

Slow bee paralysis virus (SBPV) is a virus, rarely noticed in the field, that causes paralysis of the front legs in adult bees shortly before death. On its own it is generally silent; in colonies with a high varroa load it can contribute to colony losses. There is no medicine; the way to protect colonies is to keep varroa low.

What is it?

SBPV was first described in England in the 1970s, during laboratory studies. It belongs to the same virus family as deformed wing virus and sacbrood virus. The "slow" in its name comes from the fact that in experimental infection it kills the bee later than acute bee paralysis virus; it does not mean that the disease runs a slow or mild course in the hive.

Although the virus has been detected in many parts of the world, it is rare in most countries. It has been reported most often in studies in England, in connection with varroa. It has also been detected in bumblebees.

How does it spread?

• Via varroa: The most important route. The mite injects the virus directly into the bee's haemolymph and raises the virus load to disease level.
• Within the colony: It circulates at low levels through food sharing and close contact; in this form it usually causes no symptoms.
• Between colonies: It can be carried by robbing, drifting, and moving frames and bees.

How to recognise it

In the field there is no picture specific to SBPV that can be recognised with confidence. According to laboratory observations, sick bees develop paralysis of the first two pairs of legs (front and middle legs) a day or two before death; the bee cannot walk, crawls and dies.

What you may see in the hive overlaps with the other paralysis viruses:

• Bees that cannot fly, cannot use their legs, and crawl
• Increasing numbers of dead bees in front of the hive and on the floor
• A high varroa load and its signs: perforated cappings, a patchy brood pattern, bees with deformed wings
• Unexplained colony weakening

None of these signs is specific to SBPV; the most that can be diagnosed at the hive is "suspected paralysis virus".

How it differs from similar conditions

How to confirm it in the hive

• In a colony where you see signs of paralysis, first do a varroa count: the icing sugar roll or alcohol wash, or a drop board.
• Look for signs of varroa in the brood area; open capped drone brood and examine the pupae.
• The type of virus can only be determined in the laboratory by PCR. In heavy or unexplained losses, send freshly dead and live sick bees in a closed container.

What to do

There is no medicine for SBPV. The measures are the same as for the other varroa-related viruses:

1. Bring varroa down. Use an authorised product (from the oxalic acid, formic acid, thymol or amitraz group) according to its label and in a way that does not clash with the honey harvest; take the product and dose from the package leaflet or from your veterinarian.
2. Support the colony. Make up for shortages of food and pollen.
3. Unite a very weak colony; bring its varroa down first.
4. Limit the spread. Do not move frames or bees from a diseased colony, and prevent robbing.
5. Requeen if necessary.

Prevention

• Measure varroa regularly from spring to autumn; keep it low especially before the winter bees are raised.
• Do not buy colonies or queens from unknown sources.
• Keep equipment clean and replace old combs regularly.
• Keep colonies strong and well fed.