Comparative virulence and temperature preferences in

Nosema apis and Nosema ceranae

Ingemar Fries, Eva Forsgren, Department of Ecology

Swedish Univdersity of Agricultural Sciences75007 Uppsala, Sweden

Apimondia, Buenos Aires, September 2011

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Background

Two microsporidia infections are described from the European honey bee:

Nosema apis, isolated from bees in Europe (Zander, 1907)

Nosema ceranae isolated from Apis cerana in China (Fries et al., 1996)

In 2005 Nosema ceranae wasfound as natural infections inhoney bees in Europe (Higes et al,2005) And from Taiwan (Huan et al.,2005)

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Nosema ceranae resembles Nosema apis

Similar life cycles. Only the epithelial cells of the ventriculus become infected

From Fries et al., 2007

Both belong to the Nosematidae family- no sexual reproduction and disporoblasticdevelopment

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Although similar, certain features are different

Spores are smaller and less uniform in LM

From

Frie

s et

al.,

200

7

Number of filament coils are always lower in N. ceranae compared to N.apis

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One characteristic of N. ceranae in A. cerana is the lack of emptiedspores in the host epithelium

In A. mellifera, however, emptied spores of N. ceranae is found(Higes et al., 2006)

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Ventricular epithelium five days p.i.

Gut lumen

Merozoites

In N. apis you alwaysfind emptied spores when mature spores are present

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There seems to be a correlation between the incidenceof Microsporidia infections in Spain and the detection ofN. ceranae in Spanish bees (Highes et al., 2006). In Italy beelosses are also linked to Microsporidia lately (Nanetti, 2008, pers. info)

Data from Spain (Higes et al., 2008) suggest a close relationship betweencolony collapse and N. ceranae. However, this is not evident from the US (Cox-Foster et al., 2007), nor from northern Europe (Gisder et al., 2010).

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From Klee et al., 2007

Pre-2003

Nosema apis own dataNosema ceranae own data

literatureliterature

From Klee et al., 2007

2003 onwards

literatureNosema apis own data

Nosema ceranae own dataliterature

From

Pax

ton

et a

l., 2

007

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There seems to be a tendency for Nosema ceranae replacing Nosema apis

Is Nosema apis an endangered species weneed to protect !!??

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KOD LN Antal provAB Stockholm 54C Uppsala 36D Sdermanland 22E stergtland 63F Jnkping 62G Kronoberg 14H Kalmar 41I Gotland 0K Blekinge 10M Skne 82N Halland 64O Vstra Gtaland 346S Vrmland 54T rebro 49U Vstmanland 21W Dalarna 39X Gvleborg 10Y Vsternorrland 0Z Jmtland 0AC Vsterbotten 0BD Norrbotten 0

967 samples, 319 positive for MicrosporidiaOf these, 46 samples were mixed Nosema apis/Nosema ceranaeand 273 pure Nosema apis

2007

Table1.Numberofbeekeeperssampled(Beekeepers),numberofsamples(N)numberofsamplespositiveforNosemaspp.infection(+),proportionofsampleswithmixedinfectionsofN.apisandN.ceranae(Mixed)andproportionofN.ceranaeDNAinmixedinfections(Prop)forthreeyears(2007,2009and2011)inallsamplesanalysed. 2007 2009 2011Beekeepers 29 18 41N 46 110 81+ 30 29 18Mixed 0,77 0,63 0,56PropceranaeDNA 0,29 0,12 pending

Fors

gren

& F

ries,

201

1, u

npub

lishe

d

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What is driving this replacement process ?- differences in within host virulence ?- differences in infectivity ? - different rates of transmission efficacy ?

Available data from Sweden does not supporta continous replacement process

Nevertheless, N. ceranae has replaced N. apisin large parts of the world

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The mean relative amount of N. ceranae DNA 14 days post infection. Group 1 was infected with 10% N. ceranae and 90% N. apis, group 2 was infected with equal amounts of both species and group 3 was infected with 90% N. ceranae and 10% N. apis. The triangles indicate the proportion N. ceranae at the time of infection whereas the squares show the proportion 14 days post infection. Error bars show standard deviation.

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170,

212

-217

.

170, 212-217

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The proportion infected bees 14 days post infection. Bees fed 10, 102, 103 and 104 spores of N. apis and N. ceranae respectively. Results presented as a mean based on three cages with 30 bees (n=90) for each treatment.

From Forsgren & Fries, 2010, Veterinary Parasitology, 170, 212-217 .

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4 6 8 10 12

The course of infection for N. apis and N. ceranae. Bees were individually infected with 10 000 spores of the respective parasite. At day 12 post infection, the infection is fully developed with a similar number of spores produced for both species.

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For

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010,

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, 170

, 212

-217

.

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What is driving this replacement process ?

- No competetive advantage within host- Slightly lower infective dose- Probably no difference in spore production

The dominance of N. ceranae in southern Europe, in the US and in South America remains an enigma

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Could disease impact be different in different climates?

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01

2

3

4

5

6

7

8

9

2 4 86 10 12

Days post infection

14

Log1

0 Sp

ore

coun

ts 20 C

25 C

30 C

35 C

Nosema apis

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2 4 86 10 12

Days post infection

14

Log1

0 Sp

ore

coun

ts 20 C

25 C

30 C

35 C

0

1

2

3

4

5

6

7

8

9

Nosema ceranae

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2 4 86 10 12

Days post infection

14

Log1

0 Sp

ore

coun

ts

20 C

0

1

2

3

4

5

6

Nosema apis

Nosema ceranae

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2 4 86 10 12

Days post infection

14

Log1

0 Sp

ore

coun

ts

25 C

0

1

2

3

4

5

6

7

8

9Nosema apis

Nosema ceranae

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2 4 86 10 12

Days post infection

14

Log1

0 Sp

ore

coun

ts

30 C

0

1

2

3

4

5

6

7

8

9Nosema apis

Nosema ceranae

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2 4 86 10 12

Days post infection

14

Log1

0 Sp

ore

coun

ts

35 C

0

1

2

3

4

5

6

7

8Nosema apis

Nosema ceranae

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2 4 86 10 12

Days post infection

14

Log1

0 Sp

ore

coun

ts

25 C

0

1

2

3

4

5

6

7

8

9Nosema apis

Nosema ceranae

Extracted from Raquel Martn-Hernndez et al., 2009

Spore dose: 10 000 100 000

Tissue examined: Ventriculus only Whole abdomen

There is a tendency for N. ceranae to growslower than N. apis at 20 and perhaps 25 C

There appears to be little difference in growth rate between parasite species at 30 and 35 C

Our data are not congruent with temperatureeffects reported by Martn-Hernndez et al., 2009

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0 0,2 0,4 0,6 0,8 1

Nosema apis

Nosema ceranae

N. apis, 1 week chilled

N. ceranae 1 week chilled

N. apis 1 week frozen

N. ceranae 1 week frozen Ten thousand spores

One thousand spores

Proprtion infected bees (N=25)

From Fries, I. 2010. Nosema ceranae in European honey bees (Apis mellifera). Journal of Invertebrate Pathology, 103, 573-579.

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There is a dramatic reduction on N. ceranaespore viability from freezing

This could possibly drive different rates oftransmission in different climates

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Thank you for your attention!And good luck with your bees!!