American Foulbrood (AFB) in South Africa

Mike Allsopp & Teresa Goszczynska ARC-Plant Protection Research Institute Stellenbosch & Pretoria South Africa 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 in South Africa in 1997-1998; all were negative for AFB (Davison et al 1999) • samples from colonies collected by Fries & Raina (2003) from Kenya, Uganda, Tanzania, Senegal, South Africa and Zimbabwe were all negative for AFB Exposure to AFB in Africa

• But Africa MUST have been (and is being) continually exposed to AFB • Because from all the world brought into Africa; and honey from all over the world; only South Africa has irradiation of 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 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 & of African bees; and because of good hygienic behaviour and other behavioural attributes; and because of low intensity ; 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? 2006 – 2008 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 2006 - 2008 we surveyed honeybee colonies and retail honey throughout the country • Colony honey and retail honey examined for AFB using selective media and PCR Retail Samples

135 samples 7 positive Hive Samples

140 samples 4 positive No clinical symptoms 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? 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 Clinical Infected Colonies

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

41 sub-clinical results 32 beekeepers No symptoms All over the country Clinical infections - September 2009

Number of Number of Number of Number of Action taken apiaries infected colonies infected apiaries colonies 9 2 76 6 Sterilise, isolate

35 3 650 21 Irradiate

78 48 852 181 Destroy, irradiate 14 2 96 5 None

32 9 380 65 Shook, sterilise, destroy 13 5 132 47 Shook, sterilise, destroy Clinical Symptoms - January 2011

Number of Number of Number of Number of Action taken apiaries infected colonies infected apiaries colonies 9 0 80 0 None

36 2 699 5 None

81 12 1024 12 Destroy, irradiate 17 0 104 0 None

33 1 412 4 None

13 1 125 2 None 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? 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 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 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 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 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 bullet- proof 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