American Foulbrood (AFB) in South Africa

Transcription

1 American Foulbrood (AFB) in South Africa Mike Allsopp & Teresa Goszczynska ARC-Plant Protection Research Institute Stellenbosch & Pretoria South Africa

2 AFB in Africa? Until recently there was only one report of clinical AFB ever in sub-saharan Africa; by Wolfgang Ritter (1985?), a sample from South Africa A number of studies failed to find AFB in colonies in sub-saharan Africa Survey of 57 apiaries in South Africa in ; all were negative for AFB (Davison et al 1999) Honey samples from colonies collected by Fries & Raina (2003) from Kenya, Uganda, Tanzania, Senegal, South Africa and Zimbabwe were all negative for AFB

3 Exposure to AFB in Africa But Africa MUST have been (and is being) continually exposed to AFB Because bees from all the world brought into Africa; and honey from all over the world; only South Africa has irradiation of bee products to try to prevent AFB Confirmed by Fries & Raina (2003) and Hansen et al (2003) imported honey samples on sale in African countries positive for AFB

4 African honeybees tolerant to AFB? Likely that African bees are tolerant to AFB that despite being continually exposed they don t show clinical symptoms don t suffer from the disease Largely the same with the Africanized bees of the America s? Perhaps because of absconding & swarming of African bees; and because of good hygienic behaviour and other behavioural attributes; and because of low intensity beekeeping; and because no large bulk honey imports into Africa (Fries & Raina 2003) Maybe also because of high genetic diversity and absence of beekeeper driven selective breeding in Africa?

5 Survey Because of the irradiation of bee products coming into South Africa, to prevent entry of AFB, we needed to confirm that AFB was not in the country From we surveyed honeybee colonies and retail honey throughout the country Colony honey and retail honey examined for AFB using selective media and PCR

6 Retail Samples 135 samples 7 positive

7 Hive Samples 140 samples 4 positive No clinical symptoms

8 AFB in Africa? The positive retail samples were not a surprise, because we know that honey is imported showed that either irradiation was not fully effective, or that illegal non-irradiated honey was entering the country But the positive hive samples? It could be just that bees were being fed imported honey and we were picking that up; or that sub-clinical AFB was present in SA colonies; or false positives?

9 2009 AFB Outbreak Before could answer the question, a full-scale AFB outbreak in the Cape in early 2009 Extreme clinical symptoms; colonies collapsing due to AFB Presence of AFB confirmed in the laboratory and validated in 4 international laboratories Comprehensive survey of managed beekeeping throughout the country by Department of Agriculture officials Approximately 420 beekeeping operations inspected, and 2400 samples collected and analysed

10 Clinical Infected Colonies 14 beekeepers Full-blown AFB Colonies dying 2 regions

11 Sub-Clinical Infected Colonies 41 sub-clinical results 32 beekeepers No symptoms All over the country

12 Clinical infections - September 2009 Number of apiaries Number of infected apiaries Number of colonies Number of infected colonies Action taken Sterilise, isolate Irradiate Destroy, irradiate None Shook, sterilise, destroy Shook, sterilise, destroy

13 Clinical Symptoms - January 2011 Number of apiaries Number of infected apiaries Number of colonies Number of infected colonies Action taken None None Destroy, irradiate None None None

14 Conclusions Some of the sub-clinical results are probably derived from the recent outbreak But the extent and range of sub-clinical colonies suggest previous exposure to AFB in SA; that AFB was previously present in the population, but without clinical symptoms Maybe not seen previously because of limited sampling? Possibly the same over the rest of Africa?

15 Why the Outbreak? Maybe just a very big inoculum; a large amount of imported honey allowed; honey brought into SA without irradiation; both regions with clinical symptoms have big importers Or maybe a new, more virulent strain of AFB? Or maybe have CCD in our bees which has weakened them, allowing clinical AFB

16 Why the Outbreak? Or maybe Nosema ceranae in South Africa, weakening our bees and allowing clinical AFB but AFB colonies in SA negative for N ceranae Or maybe Israeli Paralysis Virus in South Africa, weakening our bees and allowing clinical AFB but AFB colonies in SA have very few viruses

17 Why the Outbreak? Or maybe the varroa mite that has been in our bees for the past 14 years has weakened our bees So, even though they seem not to be affected by the mite, the colonies are sufficiently weakened to allow clinical AFB on exposure to a large inoculum And if that is true all the other countries in Africa that now have varroa they too might see AFB outbreaks in the future

18 African bees tolerant to AFB? Level of clinical infection in affected apiaries has gone from almost 20% to <1% in only 18 months, largely without treatment Suggests that our bees in South Africa are still essentially resistant to AFB, whatever the reason for the outbreak

19 A warning But it is warning to us if we allow our bees to be exposed to new stresses to new pests and diseases & pesticides then we could start seeing our bees dying from things they were previously tolerant to. We must be careful not to allow our bee populations get to the some state as those in Europe and America We must not believe our bees are completely bulletproof

20 Acknowledgements Thanks to my colleague Teresa Goszczynska To the all the beekeepers and the inspectors that collected the samples And to the Department of Agriculture, Forestry and Fisheries for funding the study and my attendance at this congress