We are keeping our momentum with the topic of honey bee viruses and bringing you a three-for-one post this week! Bee paralysis is associated with multiple honey bee viruses, but distinction is not always made among these viruses in determining the cause of bee paralysis. Understanding the similarities and differences among these paralysis-causing viruses can help us better mitigate and manage viral infections in honey bee colonies and more fully understand the potential impacts of certain honey bee pests, varroa mites in particular.
Bee Paralysis: The Common Ground of 3 Honey Bee Viruses
Each honey bee virus is associated with its own, typically
unique, set of symptoms by which it can be recognized. This type of virus
identification, through observing symptoms, can be useful for some viruses that
have more unique and distinct symptoms, such as deformed wing virus, but not as
useful when these symptoms begin to overlap with multiple viruses. When
multiple viruses have a common major symptom, it can make virus identification more
difficult. This is the case for 3 of the main honey bee viruses:
- Acute Bee Paralysis Virus (ABPV)
- Israeli Acute Paralysis Virus (IAPV)
- Chronic Bee Paralysis Virus (CBPV)
Although paralysis is a recurring theme among these 3
viruses, there are important differences in impact and symptoms, transmission and
vectors, and seasonality of these viruses.
All of which contribute to determining how best to manage honey bee
colonies in the case of an infection.
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| Figure 1: Honey bees with Chronic Bee Paralysis Virus infection. Credit: The Food and Environment Research Agency (FERA), Crown Copyright |
Acute Bee Paralysis Virus
The Acute Bee Paralysis Virus (ABPV) can be contracted by
honey bees in all life stages, but typically in the pupal and adult life
stages. This virus tends to peak in prevalence during the fall and winter
months and have a lower prevalence through the spring and summer. The viral
infection of ABPV can be covert, expressing no obvious signs or symptoms of
disease, or overt, causing rapid death which is sometimes preceded by a state
of paralysis in the infected honey bee. It has been reported that ABPV
infection can inhibit the immune response in honey bees (OMAFRA, 2015).
This virus is known to be vectored through varroa mites and
can also be transmitted by pollen and other food-related interactions between
honey bees. Not only does the varroa mite vector the ABPV virus, it has been
suggested that the digestive enzymes of varroa mites also stimulate the virus
to replicate. Once infected, ABPV particles accumulate in the brain and
hypopharyngeal glands of honey bees and are also easily detected in honey bee
feces.
Israeli Acute Paralysis Virus
The Israeli Acute Paralysis Virus (IAPV) is closely related
to ABPV, but there are key differences that set it apart. IAPV can be contracted
by honey bees of all castes and of all developmental stages. The viral
infection of IAPV can be asymptomatic as a covert infection, or as an overt
infection can cause honey bees to have shivering wings, dark and hairless
bodies, and paralysis that progresses with time and infection. This virus also
compromises the infected honey bee’s immune response.
Similar to ABPV, IAPV is vectored and stimulated to
replicate by varroa mites, however, in the case of IAPV the stimulus for virus
replication occurs through suppressing the honey bee’s immune system defenses.
In addition to transmission via varroa mites, IAPV is also transmitted through
food sources.
Chronic Bee Paralysis Virus
The Chronic Bee Paralysis Virus (CBPV) can be contracted by
honey bees of all castes and of all developmental stages but primarily attacks
adult bees. This virus is not characterized by any particular seasonal trend of
prevalence. Although the name, CBPV, suggests this virus is similar to the
other bee paralysis viruses, there are important distinctions. The viral
infection of CBPV can be covert and go undetected but may increase to an overt
infection characterized by adult honey bees that tremble, are unable to fly, and
often have dark and hairless bodies. Due to the latter symptom, this viral
infection is sometimes called “hairless black syndrome”. An infected honey bee
will typically die within days following the onset of infection.
Transmission of CBPV occurs topically when virus particles
from one bee come into contact with the bare thorax of another bee. The CBPV symptom
of hairlessness, combined with an overcrowded colony, results in the perfect
conditions for CBPV transmission. Although not foodborne, CBPV is also detectable
in bee feces, which may act as a source of infection through topical
application to the thorax. Accumulations of virus particles can be found
throughout the entire body of a CBPV infected bee but are most concentrated in
the head.
It is important to recognize the similarities and
differences of these viruses in order to best manage honey bee colonies in the
case of an infection, and to better classify emerging honey bee viruses. For
example, the emerging Lake Sinai virus strains have been determined to be most
closely related to CBPV (Daughenbaugh, 2015). This relation provides a starting
point from which similarities and differences can be identified between these
related viruses, ultimately contributing to the betterment and increased
understanding of honey bee management strategies and techniques.
Daughenbaugh,
K. et al. 2015. Honey bee infecting Lake Sinai viruses, Viruses., 7(6). Available
ONLINE.
OMAFRA
[Ontario Ministry of Agriculture, Food and Rural Affairs] 2021. Honey bee pests
and pathogens in Ontario apiaries, 2015. Food Safety and Environmental
Division, Animal Health and Welfare Branch. Available ONLINE.
Pernal, S.
F. and Clay, H. (eds.) 2013. Honey bee diseases and pests, 3rd
Edition. Canadian Association of Professional Apiculturists, Beaverlodge, AB,
Canada 68 pp.
Tantillo,G.,
M. Bottaro, A. Di Pinto, V. Martella, P. Di Pinto, V. Terio. 2015. Virus
infections of honeybees Apis Mellifera, Italian journal of food safety., 4.
Available ONLINE.
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