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A Comprehensive Review of Bee Diseases

Of all the insects in existence, bees are some of the most organized, territorial, and valuable. They are organized in colonies that are self-sufficient and self-propagating. The bee colony in particular is well-known for its effective defense against disease. Bees have a superior immune system, one that can be compared to that of vertebrate animals. It also does an excellent job of defending the hive against invaders through impenetrable walls built on hive crevices and openings. Bees will also physically removes parasites and other pathogenic agents from the hive. Another defense mechanism employed by the bee colony is the use of propolis to cover huge invaders which have died in the hive. However, despite this self-defense mechanism, bees are still prone to diseases.

Types of Bee Diseases

1. Bacterial Diseases

American Foulbrood

The American Foulbrood (AFB) is the most common bacterial disease affecting honey bees globally; needless to say it is the most destructive. It is prevalent in temperate and sub-tropical regions, that is, regions where there is abundant sunlight and where temperatures are high all rough the year. It is a contagious disease and the pathogenic bacterium remains dormant for up to 50 years.

Some of the symptoms of American Foulbrood include: sealed and unsealed brood cells that are scattered and irregular. A healthy brood cell is compact and well arranged. Dead larvae and pupae is also another sign of the AFB disease.

To control this disease, a wide variety of techniques are employed. One is the inspection and complete removal of infected foulbrood and hive materials. A poisonous gas is normally used to kill the bees, for instance, sulphur powder. Thereafter the entire bee colony and hive materials are collected and dumped on a hole then burned using kerosene. This method is quite costly given the materials required for destruction. As second remedy for AFB is the direct artificial swarm method. Others include the use of chemicals.

European Foulbrood Disease

The name of this disease is quite misleading since it is not confined to Europe alone. In terms of prevalence, this disease is less virulent when compared to AFB. Some of its symptoms include dead larvae. Five to four day old larvae die within the bee colony. Scattered pattern of unsealed and sealed brood is also another sign of the disease.

To control the disease, one has to consider how severe it is. Weak infection requires stimulation of the bee colony. Feed the bees with honey or sugar water and they will be stimulated to improve the hygiene within the hive. A spray of the honey combs with honey solution also works where the infection is weak. In case the infection is extreme, the infested brood combs should be removed so as to reduce the pathogens. Re-queening also helps prevent the spread of the European foulbrood.


2. Fungal Disease

Chalkbrood Disease

This is never considered a serious honey bee disease. It is however a problem is some countries such as Japan. One of the symptoms of the Chalkbrood disease is the swelling of the dead larvae and a whitish mycelia covers the larvae. In severe infestation the sealed broods die and is dried up within the cell. Furthermore, infested combs make a rattling sound.

The main remedy for this disease is the hygienic behavior where the infested brood is removed by the bees. As the beekeeper, you should stimulate the hygienic behavior of the bees by changing the brood rearing conditions. The hive size should also be perfectly fitting to the strength of the bee colony. The hive should also be well ventilated. This disease has no chemical control measures.


3. Viral Diseases

Viral diseases are common in honey bees. They are widespread and differ in nature. They also cause a varying level of damage depending on factors such as: weather conditions, type of virus, the strength of a colony, and the strain of virus in question. The natural chitin body shell and gut coating of bees protects them against any infection. However, parasites that can penetrate the skin increase the bee’s susceptibility to infections.

Sacbrood Disease

This is a well-known viral disease of honey bees. The disease was first discovered in Thailand in 1981. Currently it is spread across most countries globally. Reliable researches have even proven that the major distributors of the disease are the nurse bees. The young larvae get the disease through the worker bees’ brood-food gland secretions.

The Sacbrood disease is easy to notice. Diseased larvae normally fail to pupate after 4 days. Instead, it remains within the cells with its head and thorax changing color. The color changes first off starts with white, then pale yellow, and eventually turn to dark brown. The skin of the larvae also toughens and its contents become watery. After a while the larvae dries out and remains loosely attached to the cell floor.

Sacrood disease has no chemical treatments. The bee colony normally recovers on its own. However, the beekeeper can help prevent or fight it by stimulating behavioral hygiene within the bee colony. The disease is more prevalent during stressful periods such as food shortages, lack off food storage space, unhygienic hive conditions within the hive, other disease infestation and unbearable climatic conditions.


4. Protozoan Disease

Nosemosis or Nosema Disease

This disease destroys adult bees, worker bees, drones, and even queens. It cripples the worker bees and they will be seen crawling and trembling within the entrance to the hive. It shortens the lifespan of the bees and tremendously weakens the strength of a bee colony.

The symptoms of the disease are not easily visible unless the situation is extreme. Notable signs include swelling of the abdomen of infected bees and use of lab tests to identify some of its signs. To prevent the disease, keep the colony healthy and ensure the bees are never stressed. The apiary should also be well ventilated. Honey combs should also be changed after every two years.

A Final Word

Every beekeeper should be on the lookout of the tell-tale signs of bee diseases. If not careful, one may end up losing an entire colony of bees. Always maintain a clean and well ventilated hive and feed the bees well. Behavioral manipulation is one of the best ways of preventing and fighting most bee diseases.

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