Comparative virulence and temperature preferences in Nosema apis and Nosema ceranae

Transcription

1 Comparative virulence and temperature preferences in Nosema apis and Nosema ceranae Ingemar Fries, Eva Forsgren, Department of Ecology Swedish Univdersity of Agricultural Sciences Uppsala, Sweden Apimondia, Buenos Aires, September 2011

2 Please do not forget to turn on your mobile phone after this session!! No olviden encender su telefono mobil después de esta sesión!!

3 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 was found as natural infections in honey bees in Europe (Higes et al, 2005) And from Taiwan (Huan et al., 2005)

4 Nosema ceranae resembles Nosema apis Similar life cycles. Only the epithelial cells of the ventriculus become infected Both belong to the Nosematidae family - no sexual reproduction and disporoblastic development From Fries et al., 2007

5 Although similar, certain features are different Spores are smaller and less uniform in LM Number of filament coils are always lower in N. ceranae compared to N.apis From Fries et al., 2007

6 One characteristic of N. ceranae in A. cerana is the lack of emptied spores in the host epithelium In A. mellifera, however, emptied spores of N. ceranae is found (Higes et al., 2006)

7 In N. apis you always find emptied spores when mature spores are present Gut lumen Merozoites Ventricular epithelium five days p.i.

8 There seems to be a correlation between the incidence of Microsporidia infections in Spain and the detection of N. ceranae in Spanish bees (Highes et al., 2006). In Italy bee losses are also linked to Microsporidia lately (Nanetti, 2008, pers. info) Data from Spain (Higes et al., 2008) suggest a close relationship between colony 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).

9 Pre-2003 Nosema apis Nosema ceranae own data own data literature literature From Klee et al., 2007

10 2003 onwards Nosema apis Nosema ceranae own data own data literature literature From Klee et al., 2007

11 From Paxton et al., 2007

12 There seems to be a tendency for Nosema ceranae replacing Nosema apis Is Nosema apis an endangered species we need to protect!!??

13 KOD LÄN Antal prov AB Stockholm 54 C Uppsala 36 D Södermanland 22 E Östergötland 63 F Jönköping 62 G Kronoberg 14 H Kalmar 41 I Gotland 0 K Blekinge 10 M Skåne 82 N Halland 64 O Västra Götaland 346 S Värmland 54 T Örebro 49 U Västmanland 21 W Dalarna 39 X Gävleborg 10 Y Västernorrland 0 Z Jämtland 0 AC Västerbotten 0 BD Norrbotten samples, 319 positive for Microsporidia Of these, 46 samples were mixed Nosema apis/nosema ceranae and 273 pure Nosema apis

14 Table 1. Number of beekeepers sampled (Beekeepers), number of samples (N) number of samples positive for Nosema spp. infection (+), proportion of samples with mixed infections of N. apis and N. ceranae (Mixed) and proportion of N. ceranae DNA in mixed infections (Prop) for three years (2007, 2009 and 2011) in all samples analysed Beekeepers N Mixed 0,77 0,63 0,56 Prop ceranae DNA 0,29 0,12 pending Forsgren & Fries, 2011, unpublished

15 Available data from Sweden does not support a continous replacement process Nevertheless, N. ceranae has replaced N. apis in large parts of the world What is driving this replacement process? - differences in within host virulence? - differences in infectivity? - different rates of transmission efficacy?

16 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. 170, From Forsgren & Fries, 2010, Veterinary Parasitology170,

17 The proportion infected bees 14 days post infection. Bees fed 10, 10 2, 10 3 and 10 4 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,

18 The course of infection for N. apis and N. ceranae. Bees were individually infected with 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 From Forsgren & Fries, 2010, Veterinary Parasitology, 170,

19 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

20 Could disease impact be different in different climates?

21 Nosema apis Log10 Spore counts C 25 C 30 C 35 C Days post infection 14

22 Nosema ceranae 9 8 Log10 Spore counts C 25 C 30 C 35 C Days post infection 14

23 20 C 6 Log10 Spore counts Nosema apis Nosema ceranae Days post infection 14

24 25 C Log10 Spore counts Nosema apis Nosema ceranae Days post infection 14

25 30 C Log10 Spore counts Nosema apis Nosema ceranae Days post infection 14

26 35 C Log10 Spore counts Nosema apis Nosema ceranae Days post infection 14

27 25 C Extracted from Raquel Martín-Hernández et al., 2009 Log10 Spore counts Nosema apis Nosema ceranae Days post infection 14 Spore dose: Tissue examined: Ventriculus only Whole abdomen

28 There is a tendency for N. ceranae to grow slower 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 temperature effects reported by Martín-Hernández et al., 2009

29 N. ceranae 1 week frozen N. apis 1 week frozen Ten thousand spores One thousand spores N. ceranae 1 week chilled N. apis, 1 week chilled Nosema ceranae Nosema apis 0 0,2 0,4 0,6 0,8 1 Proprtion infected bees (N=25) From Fries, I Nosema ceranae in European honey bees (Apis mellifera). Journal of Invertebrate Pathology, 103,

30 There is a dramatic reduction on N. ceranae spore viability from freezing This could possibly drive different rates of transmission in different climates

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