Muhammad Babar Shahzad Afzal, Muhammad Rizwan, Ansa Banazeer, Ammad Ahmad

Beekeeping & Hill Fruit Pests Research Station, Shamsabad, Rawalpindi Pakistan

Honeybee colonies can be affected by various diseases that can have significant impacts on bee health and overall hive productivity. Some of the important honeybee diseases include:

1. Nosema

Nosema is an intestinal disease of adult honeybees caused by spore-forming microsporidia Nosema apis and Nosema ceranae. N. apis is a parasite of the European honey bee (Apis mellifera), and N. ceranae of the Asian (Apis cerana) and the European honey bees. Nosema levels generally increase when bees are confined, such as in the autumn and winter in colder climates. The disease is transmitted among bees via the ingestion of contaminated comb material and water, and by trophallaxis; honey stores and crushed infected bees may also play a role in disease transmission. The spores expelled in large quantities with the faeces of diseased individuals remain viable for more than a year. Bees infected with Nosema may display symptoms such as dysentery (diarrhea), which can be seen as fecal material on the outside of the hive. Infected bees may have a shorter lifespan and reduced foraging efficiency. Nosema infections can weaken a colony over time, potentially leading to colony collapse, especially when combined with other stressors. Infected bees usually defecate inside the hives, leaving yellow or yellowish excrement stains on top bars of frames, bottom board, combs, as well as the inside and outside of the hive.

Management

Beekeepers can successfully prevent infestations with Nosema in European honeybee colonies by performing a number of good husbandry practices. Regularly feeding the bees with Fumagilin-B in gallons of heavy syrup in the spring and fall is one of the best preventive measures beekeepers can take to avoid Nosema problems. Keeping colonies in sunny winter locations and avoiding conditions of excess moisture inside the hive can also discourage infestations. Maintaining good hive hygiene, providing proper nutrition, and reducing stressors on the colony can also contribute to Nosema control. Disinfecting contaminating combs is necessary in order to prevent further spreading of the parasite within the hive. This can be achieved by fumigation with 60-80 per cent acetic acid vapour. The vapour kills the spores within one week.

2. American Foulbrood (AFB)

American Foulbrood (AFB) is a highly contagious and lethal bacterial disease that affects honeybee larvae. It is caused by the bacterium Paenibacillus larvae. AFB is one of the most serious diseases that honeybee colonies can face, and it can result in the death of entire colonies if not properly managed. The bacteria produce highly resistant spores that can survive for long periods in hive equipment, honey, and on other surfaces. AFB is primarily spread through contaminated hive equipment, contaminated honey, and robbing behavior among honeybee colonies. Larvae become infected when they ingest spores, usually through contaminated food. The larvae change from a pearly white to a brownish color as the disease progresses. Infected larvae typically exhibit a characteristic “ropy” or stringy texture when a toothpick is inserted and withdrawn from their remains. Once infected, larvae die, and their remains become a source of new spores, perpetuating the cycle of infection. AFB can spread quickly within a hive and to neighboring colonies if not identified and controlled. Severe AFB infections can lead to the death of the entire honeybee colony.

Management

Given the severity and contagious nature of AFB, beekeepers must be vigilant in monitoring their colonies and implementing appropriate measures to prevent, detect, and manage the disease. Early intervention is crucial to minimizing the impact of American Foulbrood on honeybee populations. Preventive measures, such as good hive management practices, regular inspections, and proper sanitation, are crucial in minimizing the risk of AFB. Confirmation of AFB often requires laboratory testing, including microscopic examination of larval remains. Traditionally, infected colonies and contaminated equipments are often burned to prevent the spread of the disease. Some antibiotics, such as oxytetracycline and ampicillin, are used to control AFB during its early phase. However, antibiotic resistance is a concern, and their use is subject to regulations. Regulatory measures which include the destruction of infected colonies and restrictions on the movement of bees and equipment to prevent the spread of the disease may also be adopted.

3. European Foulbrood (EFB)

European Foulbrood (EFB) is another bacterial disease that affects honeybee larvae, and it is caused by the bacterium Melissococcus plutonius. While not as severe as American Foulbrood (AFB), EFB can still weaken honeybee colonies and impact overall hive health. EFB is spread horizontally within colonies through contaminated food provided by nurse bees to larvae. Unlike AFB, EFB does not produce long-lived spores, so it is generally not as persistent in hive equipment. Larvae become infected when they ingest the bacteria through their food. Infected larvae often have a twisted (coiled) or irregular shape. Initially, infected larvae may have a yellowish color, but they can turn brown or gray as the disease progresses. Infected larvae may die, and the disease can result in larval death or developmental abnormalities. EFB can weaken a colony, leading to reduced population and productivity. While serious, EFB is usually not as lethal as AFB, and colonies can recover if appropriate measures are taken.

Management

While European Foulbrood is generally less severe than American Foulbrood, it is still important for beekeepers to be vigilant and take appropriate measures to manage and prevent its spread within honeybee colonies. Early detection and intervention are key to minimizing the impact of the disease. Beekeepers should visually inspect brood frames for signs of EFB during routine hive inspections. Maintaining good hive hygiene, such as removing dead larvae promptly, can help control the spread of EFB. Requeening a colony with a new, disease-resistant queen may help improve overall hive health. In some cases, antibiotics such as oxytetracycline and ampicillin, may be used to treat EFB, but their use is subject to regulations. Preventing the introduction of contaminated material and bees can also reduce the risk of disease.

4. Chalkbrood

Chalkbrood is a fungal disease that affects honeybee larvae. It is caused by the fungus Ascosphaera apis. Chalkbrood infects honeybee larvae, transforming them into hard, chalk-like mummies. Chalkbrood is spread through the production of fungal spores. Bees become infected when they come into contact with spores, either through contaminated food or other hive materials. Larvae become infected when they ingest fungal spores. Initially, infected larvae become swollen and white. As the disease progresses, the larvae shrink and harden, resembling chalk. While Chalkbrood is generally not as lethal as some other diseases, it can weaken a colony, especially if it affects a significant number of larvae. Infected larvae are unable to contribute to the colony’s workforce, leading to a reduction in the overall brood population.

Management           

While Chalkbrood is not typically as devastating as some other honeybee diseases, beekeepers should still monitor their colonies regularly and take appropriate measures to manage and prevent its spread. Early detection and proactive management can help mitigate the impact of Chalkbrood on honeybee colonies. Regular hive inspections, maintaining strong and healthy colonies, and practicing good hygiene can help prevent Chalkbrood. Minimizing stressors on the colony, such as ensuring adequate nutrition and a stable environment, can contribute to disease prevention. Beekeepers should visually inspect brood frames for signs of Chalkbrood during routine hive inspections. Confirmation may require laboratory analysis, including microscopic examination of larval samples. Maintaining good hive hygiene, such as removing dead or mummified larvae promptly, can help control the spread of Chalkbrood. Adequate hive ventilation can create an environment less favorable for the growth and spread of the fungus. Some beekeepers may opt to requeen a colony to introduce a new, healthy queen and potentially improve overall colony health.

5. Sacbrood

Sacbrood is a viral disease that affects honeybee larvae. It is caused by the Sacbrood virus (SBV), which is a member of the Iflaviridae family. Sacbrood is generally considered a less severe disease compared to some other honeybee illnesses, and its impact on colonies can vary. The virus is primarily transmitted orally, as larvae consume food containing the virus. Adult bees can become infected by picking up the virus from contaminated hive materials or other infected bees. Infected larvae exhibit characteristic symptoms, including a swollen appearance, a pale, translucent color, and a sac-like or baggy appearance. While Sacbrood is generally not as lethal as some other diseases, it can weaken a colony by reducing the number of healthy adult bees emerging from infected larvae. Infected larvae are unable to contribute to the workforce of the colony, potentially leading to a reduction in the overall worker population.

Management

Sacbrood is generally not as alarming as some other honeybee diseases, but it is essential for beekeepers to monitor their colonies regularly and take appropriate measures to manage and prevent its spread. As with other diseases, early detection and proactive management are key to maintaining the health of honeybee colonies. Beekeepers may detect Sacbrood during routine hive inspections by observing the characteristic symptoms in affected larvae. Maintaining overall hive health, proper nutrition, and reducing stressors can contribute to the prevention of Sacbrood. Preventing the introduction of contaminated hive materials and bees can also minimze the risk of disease. Breeding honeybee colonies for genetic resistance to viruses can be a long-term strategy for disease prevention. Beekeepers may remove and dispose of infected larvae to help control the spread within the colony.

6. Acute Bee Paralysis Virus (ABPV)

The Acute Bee Paralysis Virus (ABPV) is a significant viral pathogen that affects honeybees. It belongs to the family Dicistroviridae and primarily impacts adult bees. ABPV is one of several viruses that can pose threats to honeybee colonies. ABPV can be transmitted through several routes, including direct bee-to-bee contact, contaminated food, and vertical transmission from queens to their offspring. Varroa destructor mites are known vectors for ABPV, transmitting the virus when they feed on honeybee hemolymph (bee blood). Symptoms in infected adult honeybees include shivering or trembling, paralysis, and a characteristic “k-wing” posture where one or both wings are held away from the body at an abnormal angle. Bees infected with ABPV may have a shortened lifespan and unable to fly. Infected queens may exhibit reduced egg-laying behavior. ABPV can contribute to the overall weakening of honeybee colonies. Infected colonies may be more susceptible to other stressors, such as poor nutrition or environmental challenges.

Management

As with many honeybee diseases, a holistic approach to beekeeping that includes regular monitoring, good hive management practices, and measures to control contributing factors like Varroa mites and stressors can help reduce the impact of Acute Bee Paralysis Virus on honeybee colonies. Preventing the introduction of contaminated bees and hive materials can help reduce the risk of ABPV. Selective breeding for bees with resistance to ABPV and other viruses can be a long-term strategy for disease prevention. The detection of ABPV often requires laboratory testing, including methods like RT-PCR (Reverse Transcription Polymerase Chain Reaction) to identify the presence of viral genetic material.                         

CONCLUSION

Beekeepers are advised to use various strategies to manage and control these diseases, including chemical treatments, hygienic hive practices, breeding for resistance, and promoting overall colony health. Regular monitoring and early detection are crucial for effective disease management in honeybee colonies. Additionally, maintaining diverse and pesticide-free foraging areas can contribute to overall bee health and resilience against diseases.

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