Nosema%20%20A%20New%20Management%20Problem

1
Nosema A New Management Problem

• Rick Fell
• Department of Entomology
• Virginia Tech

2
Nosema

• Nosema is a microsporidian - Class Microsporidia
  which is now placed in the Fungi
• The microsporidians are a large group of obligate
  intracellular parasites that can cause both
  chronic and acute disease
• The genus Nosema has more than 150 species, the
  majority of which infect invertebrates,
  especially insects

3
Nosema

• A number of Nosema species infect Hymenoptera
  (bees, ants, wasps) - our concern is with those
  infecting honey bees
• Major species of concern has been Nosema apis
  which causes nosema disease in adult bees
• Now a newly discovered second species in U.S. -
  Nosema ceranae

Nosema bombi infects bumblebees
4
Nosema Disease (Nosema apis)
Nosema spores

• Has been a very common disease condition, 50 -
  90 of the colonies have bees with Nosema
• Most prevalent in late winter and early spring,
  aggravated by stress
• Ingested spores germinate in the midgut and
  invade the epithelial cells
• Once in the cell, the organisms grows by
  absorbing nutrients from the cell

Non-infected midgut
5
Life Cycle of Nosema apis
Infectious spore
tubule extended
Sporoplasm injected
Growth and reproduction
Spore formation
Growth and spore production requires 6 - 10 days
6
Nosema Disease (Nosema apis)
Nosema spores

• The microsporidian damages the cells, affects
  digestion, causes malnutrition and premature
  death
• The life spans of worker bees may be reduced up
  to 78
• Young workers infected by nosema are not able to
  produce royal jelly - can affect brood production
  and colony build-up
• Queens with nosema may be superceded

7
Nosema Symptoms and Diagnosis

• No good symptoms of infection, difficult to
  diagnose without the use of laboratory equipment
• Identification by analysis of adult bee abdomens
  - abdomens are homogenized, homogenate is
  strained, and then analyzed microscopically

homogenizing bees
spores
sample preparation on a slide
equipment for nosema diagnosis
8
Nosema Symptoms and Treatment

• May see defecation in the hive, weak, crawling
  bees, retarded build-up in spring
• Defecation in the hive leads to the contamination
  of combs with millions of spores
• Heavy infections may lead to dysentery
• Control
• elimination of stress
• use of antibiotic fumagillin (Fumigilin-B) which
  is fed in the fall as a preventative

9
New Pathogen Nosema ceranae
Nosema spores A N. ceranae, B N. apis

• Discovered in 1996 in Apis cerana and assumed to
  be specific to Eastern honey bee
• In 2005 Chinese researchers reported N. ceranae
  in A. mellifera. In 2006 it was discovered in
  Spain (following increases in Nosema infections
  from 2000 (10) - 2004 (88)
• In 2007 reported to found throughout Europe, in
  Canada and in the U.S.
• Recently, reported that N. ceranae has been
  present for over 10 years in the U.S. (at least
  since 1995) and is widespread

10
New Pathogen Nosema ceranae
Nosema spores A N. ceranae, B N. apis

• Nosema ceranae was the only Nosema species found
  in the U.S. to infect European honey bees from
  samples collected in 12 different states
  representing all of the major geographic regions
  of the country
• These findings indicate that N. ceranae has been
  the predominant infection and that it has
  apparently displaced N. apis in U.S. bee
  populations
• Discovery of N. ceranae has raised conerns
• Studies in Spain indicate that it can be highly
  pathogenic
• N. ceranae has been associated with CCD

11
Worldwide Distribution of Nosema ceranae
N. ceranae N. apis
Modified from Klee et al. 2007. Jour. Invert.
Pathology Chen et al. 2008. Jour. Invert.
Pathology
12
Honey Bee Infection with Nosema ceranae

• Experimental inoculations of bees with N. ceranae
  led to rapid infections in lab studies in Spain
• In the infected groups mortality was not observed
  until day 6, but by day 8 mortality was 100
• The high pathogenicity of N. ceranae has been
  suggested as a possible cause for the
  depopulation syndrome observed in European
  countries in the last few years
• Interesting question - if it has been in the U.S.
  since 1995, why havent we seen the types of
  colony losses observed in Spain?

(Higes et al. 2007)
13
Symptoms of N. ceranae infections

• Common field conditions found with N. apis not
  associated with N. ceranae infections
• does not seem to produce dysentery
• infected bees do not have swollen abdomens, or
  white swollen midgut
• do not find crawlers in front of infected hives
• N. ceranae infections tend to be asymptomatic,
  can only diagnose with a microscopic examination
  for spores in the midgut

14
Dealing with N. ceranae

• Unlike N. apis not seasonally limited to winter
  or spring. Found all year and may peak in
  summer.
• Management practices can help reduce problems
• Reduce colony stress, good hive locations with
  full sun
• Replace older combs which have a high probability
  of having spores
• Be careful of switching combs between colonies,
  N. ceranae spores can be transmitted in pollen

• Good colony nutrition may help reduce problems -
  pollen supplements in late winter and early
  spring can help promote colony health

15
Dealing with N. ceranae

• Can use antibiotic treatment
• Fumagilin-B is the only approved nosema treatment
  (extract from the fungus Aspergillus fumigatus)
• It has been shown to be effective against N.
  ceranae
• Feed as a medicated syrup (one rounded teaspoon
  fumagilin per gallon) in either fall or spring.
• Can feed to packages on installation to reduce
  nosema problems

16
Virginia Nosema Survey

• Initiated a survey to determine the incidence of
  Nosema in Virginia and which species are present
• Bee samples collected from colonies around the
  state - 30-40 bees/sample
• Analyze bee samples for the presence of Nosema,
  positive samples subjected to real-time PCR for
  species identification.
• To date 119 samples collected 48.7 beekeeper
  samples positive, 16.7 VT apiary samples
  positive

Samples from individual hives, collected in EtOH
17
TaqMan Assay
18
Nosema Sample Analysis - Spore Counts and Species
Identification

spores present but negative PCR results
random sample negative for spores
19
N. ceranae
PCR Amplification Curves for Nosema Analysis
N. apis