The Kakugo virus is a subtype of the Deformed wing virus, typically affecting the worker bee’s brain. It causes aggressive behavior in honey bees, as you’d expect from guard bees.
The infection is classified as a picorna-like virus and is the first to result in symptoms of aggression in bees. Translated from Japanese, Kakugo means ready to attack.
Very little research exists because the Kakugo virus is a relatively new and rare bee disease. Scientists have found the virus’s structure is similar to Deformed wing virus and Sacbrood.
Quick facts about Kakugo virus
- The Kakugo virus is believed to start in the brain and then spread to other parts of the insect’s body.
- It was first discovered in 2004 by scientists in Japan.
- Kakugo’s genetic material (RNA) makes a protein similar to other insect viruses.
- The protein has elements common to other viral proteins.
- It is likely transmitted orally between colony members or through physical injuries.
- Varroa mites (Varroa destructor) may act as a vector for the virus.
- DWV and KV may be regional variants of the same virus.
- The virus has been identified in the brains of aggressive worker honeybees that protect their colonies against threats like giant hornets.
6 more viral diseases that impact honey bees:
- Cloudy wing virus
- Chronic bee paralysis virus
- Kashmir virus
- Israeli acute paralysis virus
- Nosema virus
- Black queen cell virus
Research 1: Distribution of Kakugo Virus and Its Effects on the Gene Expression Profile in the Brain of the Worker Honeybee Apis mellifera L.
The study investigates the Kakugo Virus (KV) in worker honeybees. Using specialized techniques, researchers found that KV infects various parts of the bee’s brain, which may influence their behavior, particularly aggression.
The virus also spreads to other parts of the bee’s body, like fat tissues essential for metabolism and immunity.
The study compares naturally infected bees with experimentally infected ones. In both cases, as the infection progresses, the virus spreads to broader areas of the brain. This could have varying effects on brain functions over time.
Gene expression in the bee’s brain changes due to KV infection, suggesting an impact on the bee’s immune system. Despite this, KV infection isn’t lethal based on observed survival rates. It also doesn’t cause significant behavioral changes in honey bees.
The study aims to explore how KV affects honeybee neural and physiological states, focusing on its distribution in different tissues and its impact on gene expression in honeybee brains.
Tissue distribution: Through in situ hybridization, the researchers found KV in various parts of the brain, hypopharyngeal glands, and fat bodies. Initially, the virus appeared in restricted brain regions in artificially inoculated bees. It later spread to other areas, including the mushroom bodies and optic lobes.
Gene expression: Although the expression of 11 specific genes remained unaffected, a novel gene was identified through cDNA microarray analysis that was upregulated in KV-infected bees. This gene coded for a hypothetical protein featuring a leucine zipper motif. A similar gene was found in the parasitic wasp Nasonia but not in other insects.
Comparison to other viruses: KV is related to the Deformed Wing Virus (DWV). Its relationship with aggressive behavior in worker bees is not yet fully understood. In colonies with severe KV infection, the virus was found in various worker bee populations, complicating this potential relationship.
Broader context: The study points out that some microbe-honeybee interactions lead to behavioral changes, such as precocious foraging. However, the potential effects of microbe infection on honeybee brain function have been relatively understudied.
Novel contributions: This researchers provide the first detailed analysis of the tissue distribution of a honeybee virus and its molecular effects in infected bee brains. It lays the groundwork for understanding the molecular and neural bases of how KV affects honeybees.
Research 2: Kakugo Virus from Brains of Aggressive Worker Honeybees
This paper examines whether KV causes bees to become more aggressive. The scientists looked at different kinds of worker bees in the hive, like nurses, guards, and foragers, to see who had this virus.
Their results showed that only the aggressive “attacker” bees had the virus in their brains. This finding suggests a link between the virus and aggressive behavior.
If you want to learn more about the challenges honey bees face, check out our honey bee threat guide.