Diseases of bee brood

Sacbrood is an infectious disease that kills bee larvae and young pupae. On the territory of Our Country, this infection is quite widespread and causes economic damage, causing the death of bee colonies. In order to stop diseases of the brood of bees in time, you need to see their signs as early as possible (for example, in the photo), learn the methods of treatment and prevention.

What is sacbrood disease

The name of the disease “Saccular brood” comes from the appearance of the diseased larvae. Affected by infection, they become like sacs filled with liquid. The causative agent of this disease is a neurotropic virus.

It affects the larvae of the printed brood of honey bees, drones, queens of all breeds. The most susceptible to the disease are young larvae, which are 1 to 3 days old. The incubation period of the virus is 5-6 days. Prepupae die at the age of 8-9 days before being sealed.

The disease of bee brood occurs after a virus enters the body, which is very resistant to various kinds of physical and chemical effects:

• drying;
• chloroform;
• 3% caustic alkali solution;
• 1% solution of rivanol and potassium permanganate.

The virus remains viable when:

• on combs – up to 3 months;
• in honey at room temperature – up to 1 month;
• when boiling – up to 10 minutes;
• in direct sunlight – up to 4-7 hours.

Due to the death of the larvae, the bee colony is weakened, the productivity of the honey plant decreases, and in severe cases, the colonies die. Adult bees carry the disease in a latent form and are carriers of the virus in the winter season.

Saccular brood appears in central Our Country, in early June. In the southern regions a little earlier – in May. During the abundant summer honey plant, the disease subsides or completely disappears. You may get the impression that the bees themselves coped with the virus. But in early August or next spring, an untreated disease manifests itself with renewed vigor.

Possible causes of infection

The carriers of the infection are adult bees, in whose body the virus persists all winter. The virus can be transmitted by different insects:

• within the family, the disease is spread by worker bees, which, cleaning the hives and removing the corpses of infected larvae from them, become infected themselves, and when feeding healthy larvae with food, they transmit the disease;
• Varroa mites can also bring the disease – it was from them that the sac brood virus was isolated;
• thief bees and wandering bees can become a source of infection;
• untreated work equipment, honeycombs, drinkers, feeders may also contain infection.

The carriers of the virus between families in the apiary are most often infected worker bees. The spread of infection occurs when raids are made, or it can occur when combs are moved from sick bees to healthy ones.

Symptoms of bee brood disease

The incubation period for the development of the infection lasts 5-6 days, after which you can easily notice signs of saccular brood, as in the photo, after examining the combs:

• lids are open or perforated;
• honeycombs have a colorful appearance due to the alternation of sealed cells with empty ones;
• the larvae look flabby and watery in the form of sacs;
• the corpses of the larvae are located along the cell and they lie on the dorsal side;
• if the larvae have already dried up, they look like a brown crust with an anterior part bent up.

Externally, combs with affected brood resemble foulbrood disease. The difference is that with sac brood there is no rotten smell and viscous mass when removing corpses. Also, with sac brood, the infection spreads more slowly than with foulbrood. In the first summer, from 10 to 20% of families can get sick. If the disease is not treated, then in the second summer up to 50% of the bees in the apiary can be affected.

In a strong colony, the bees throw out the dead brood. A sign of a weakened family – the untouched corpses of the larvae remain to dry in the cells. The degree of damage by sac brood is determined by the number of dead larvae in the combs.

How to Diagnose Sacbrood in Bees

Bees can suffer from several diseases at once, including sacbrood, which has characteristics in common with American and European foulbrood. In this case, it is not easy to detect clear signs of this disease. To dispel all doubts, a sample of honeycombs measuring 10×15 cm is sent to the laboratory for analysis.

Currently, there are many methods for laboratory diagnosis of viral diseases of bees:

• linked immunosorbent assay;
• polymerase chain reaction (PCR);
• chemiluminescence method and others.

All of them have a number of disadvantages for detecting strains of the same virus. The polymerase chain reaction is considered the most accurate.

The results of the analysis are ready in 10 days. If the disease is confirmed, then quarantine is imposed on the apiary. If up to 30% of the bees are sick, the beekeeper separates the sick families from the healthy ones and takes them out to a distance of about 5 km, thus organizing an isolator.

When more than 30% infected with sac brood are found, an isolation room is organized in the apiary, and all families receive the same top dressing.

Saccular brood of bees: treatment

If an infection is detected, the apiary is closed for quarantine. Treatment of sac brood is carried out only for weakly and moderately damaged colonies. Families with a severe degree of damage are destroyed. Before the start of the treatment itself, several measures are taken to improve the sick family:

1. In the infected hives, frames with brood are added at the exit from healthy colonies.
2. They replace diseased queens with healthy ones.
3. The hives are well insulated and provide bees with food.

Also, for reinforcement, two or more sick families are brought together. Treatment should be carried out in disinfected hives, from which frames with a large number of diseased brood are removed.

There is no cure for infection as such. Means used to treat sick bees with sacbrood only weaken the signs of the disease in bees. In the first half of summer, individuals infected with sac brood are fed with sugar syrup with the addition of Levomycetin or Biomycin (50 ml per 1 liter of syrup).

According to beekeepers, the treatment of sac brood can be carried out using the Endoglyukin aerosol. Spraying is carried out 3-5 times every 5-7 days. In this case, the air temperature should be within +15 … +22⁰C.

An effective way to combat the spread of sac brood is considered to be a temporary (for 1 week) cessation of egg laying. To do this, the queen of the hive is removed, and an infertile uterus is planted in her place.

Disinfection of hives and inventory

Sanitary treatment for bagged brood of wooden objects, including beehives, is carried out as follows:

1. Spray with 4% hydrogen peroxide solution (0,5 l per m²).
2. After 3 hours, wash with water.
3. Dry for at least 5 hours.

After that, new bee colonies can be settled in the hives, and the wooden inventory can be used for its intended purpose.

The rest of the accessories used when working in the apiary undergo the same disinfection as in case of foulbrood disease:

• combs from diseased hives are subjected to reheating at t 70⁰C or disinfected with vapors of 1% formalin solution (100 ml per 1 m³), after which they ventilate for 2 days and only then use it;
• honeycombs can be treated with a 3% hydrogen peroxide solution, sprayed until the cells are completely filled, shaken, rinsed with water and dried;
• towels, bathrobes, beehive canvases are disinfected by boiling for half an hour in a 3% solution of soda ash;
• facial meshes are boiled for 2 hours in a 1% hydrogen peroxide solution or for 0,5 hours using the Vetsan-1 preparation;
• metal inventory is treated with 10% hydrogen peroxide and 3% acetic or formic acid 3 times every hour.

One of the simplest and most effective methods of disinfection is considered to be treatment with a blowtorch.

The land plot on which hives with colonies infected with sac brood stood is treated with bleach at the rate of 1 kg of lime per 1 m² by digging to a depth of 5 cm. Then apply abundant watering of the territory with water.

Methods of prevention

It is noted that the greatest distribution of sac brood occurs in cool, damp weather, in weak bee colonies, in poorly insulated hives with insufficient nutrition. Therefore, in order to prevent the emergence and spread of the disease of the brood of bees, certain conditions must be created in the apiary:

• maintenance of only strong families;
• sufficient food supply;
• complete protein and vitamin nutrition;
• timely updating and warming of the hive, good maintenance;
• mandatory check of the hive in the spring, especially in damp cool weather;
• the location of bee houses in dry, well-lit places;
• regular cleaning and disinfection of beekeeping equipment every spring after the wintering of bees.

It is necessary to inspect the hive at least once every 1 weeks. At the first sign of sac brood, all measures must be taken to ensure that other bees remain healthy.

Conclusion

Sacbrood cannot be permanently cured, as the exact method of treatment has not yet been developed. Three times the use of recommended drugs with an interval of 7 days only removes the clinical signs of the disease. The virus remains in the family as long as there is a varroa mite – the main carrier of the virus. Nevertheless, creating favorable conditions for the formation of strong bee colonies reduces the risk of the spread of sac brood.