AFB Elimination and the Tools at Hand

The question of American Foulbrood (AFB) elimination in New Zealand and whether it is possible is one that has long been questioned by beekeepers. Regardless of individual opinions though, the Pest Management Plan has elimination of the disease from managed colonies as a goal. If that’s the destination, what tools and technologies do both beekeepers and the Management Agency National AFB Pest Management Plan have at their disposal to reach it? We take a look into several tools and technologies, both in use and potential.

The Agency are currently undertaking consultation with beekeepers over the structure of the AFB PMP for 10 years from April 1 2023. Within these pages in recent months there has been considerable discussion pertaining to the potential use of AFB sniffer dogs to aid the Agency’s efforts. They are far from the only tool, technique or technology that beekeepers have, or could have, at their disposal though. Before we dive into them, let’s take a look at the current state of the road to elimination.

Destruction of infected hiveware is critical if AFB elimination is to be achieved.

Road to AFB Elimination

The reported incidence of AFB as a percentage of beehives in New Zealand has stabilised since 2017, going from 0.33% of registered colonies infected then, to 0.31% in the most recent reporting year. That equates to 2526 colonies across the country.

The full goal of the Plan is to “eliminate clinical AFB from managed colonies within New Zealand”. This is sometimes confused with eradication of the organism from New Zealand entirely, something that would be much more challenging due to the long-lived nature of AFB spores.

Because many beekeepers have been able to effectively eliminate AFB from their operations, the Agency is confident that this can be replicated on a national scale and the elimination goal achieved.

AFB PMP Agency national compliance manager Clifton King.

Currently, beekeepers can use a variety of methods to control AFB within their operations, but hives must be registered with the Agency and are subject to either annual Certificate of Inspection (COI) by a beekeeper with a Disease Elimination Control Agreement (DECA) with the Agency, or they are inspected according to the procedures agreed in a DECA between owner and the Agency. This agreement usually contains requirement for at least two beekeeper inspections of every hive each year.

Regardless of the method used to identify AFB infected colonies, national compliance manager Clifton King stresses the importance of a key concept on the road to elimination.

"The fundamental principle of our elimination strategy is for AFB beehives to be found and destroyed before they infect another beehive. When I say ‘before they infect another beehive’, what I actually mean is before they infect one or more other hives,” King says.

As it stands, the Agency primarily uses clinical inspections through trained beekeepers known as AP2s (Authorised Person 2) to monitor beekeepers’ AFB elimination performance . Honey sample spore testing is also used, with negative tests providing evidence of which beekeepers are doing a good job of eliminating AFB from their beehives, along with culture, PCR or qPCR testing on individual hives or equipment very occasionally.

"Ropey" brood, a clear sign of AFB during a clinical inspection.

Clinical Inspections

The current strategy is based largely around human inspection of hives, by beekeepers under the COI or DECA system, as well as visits by AP2s. While the national rate of AFB infection is not fast moving towards elimination using this strategy, King stresses the great value in beekeeper inspection and that, should all hive owners adhere to COI and DECA agreements, he believes elimination is possible.

“Management Agency experience, where we have been closely inspecting and monitoring what happens, is you can reduce the level of AFB in a beekeeping operation by 90% in one year, if all you do is thoroughly inspect all of the hives twice a year and burn the AFB hives. Only twice,” King says.

Crucial to the strategy is taking the correct actions once AFB has been diagnosed in a hive to ensure that all materials and appliances associated with a case of AFB is destroyed.

For a beekeeper that is complying with their DECA inspection requirements and destruction of infected gear, then “elimination is the natural outcome” King says. The 90% reduction in AFB infections in year one can effectively become 99% if it is repeated in year two, in the Agency’s experience.

Honey sample testing is increasingly being used in the Agency's surveillance.

Honey Sample Spore Testing

Of course, there are those beekeepers who are not fully complying with their DECA and thus hives are either not receiving adequate inspections and/or the correct remedial action is not being taken once AFB is identified. These offenders are a massive pot hole in the road to elimination and thus the Agency is focusing added attention on them. Honey sample spore testing is playing a crucial role in that strategy.

The AFB test in honey has been used by the Agency for many years, but now they use it with greater purpose King says. Rather than random samples being tested, they are collecting honey samples from those beekeepers who have large hive holdings but low reported levels of AFB. This helps determine whether they are doing an excellent job of eliminating AFB.

“Honey sampling is a fantastically cheap way of effectively inspecting hundreds of beehives with one sample to confirm the absence of AFB . It is far more cost effective than lifting the lids on all of those beehives and inspecting every brood frame for AFB,” King explains.

“We don't need to worry about the beehives owned by those beekeepers getting negative honey sample results, because we've already got good evidence that they're doing a great job and we can prioritise our resources elsewhere.”

Over the past year more funds have been allocated to honey sample testing by the Agency and they are now increasingly using the technique to target elimination efforts.

Diagnostic Tests

Until last year, diagnostic testing of AFB in beehives required sampling of dead bees or suspicious ropy materials from individual hives, making it highly accurate but also highly expensive on a large scale.

“For Culture, PCR and qPCR testing on honey bee samples to become a commercially viable alternative to clinical inspections, the cost of these diagnostic tests needs to reduce significantly and/or there needs to be significant benefits over and above what can be achieved from clinical inspection,” King says.

The Foster Method of sampling beehives for diagnostic testing uses a swab, such as this, and allows for pooling of samples.

Some of those barriers may have been lowered though, with the introduction of a swabbing method of sampling hives for qPCR testing. The Foster method, developed by Gisborne-based lab dnature diagnostic and research also allows effective pooling of many hives into one test which reduces cost-per-hive. A swab can be quickly swiped across the entrance of the beehive to collect the sample.

Up to 12 samples are being pooled in each Foster test at present, but dnature are hoping to move to a greater number going forward, says technical director John Mackay.

“If you find a positive, you can pull individual samples out and retest. Or you can tell a beekeeper those 12 hives are fine, those 12 are fine, but there has been a positive result with that group of 12. Have a close inspection.”

Previous AFB diagnostics tests cost approximately $80 per sample, whereas each pool of Foster method tests – so up to 12 – costs around $140.

One of the earliest uses of the Foster method was in Project CleanHive, carried out by a group of Southland and Otago apiarists which saw more than 800 hives tested between 2018 and 2021. The project concluded that “early intervention when clinical cases are discovered within a business, along with qPCR screening, should potentially allow for eradication of clinical AFB in one season”.

Project CleanHive used testing of hive entrances, but Mackay says the method could be used on equipment in beekeeper’s sheds.

“Potentially, if you have stacked up honey supers you could run a swab back and forward across the top of the frames and test them,” Mackay says.

From the Agency’s perspective, there is potential in the new qPCR method developed by dnature, and the Agency is looking forward to the Gisborne lab’s research being peer reviewed and published. Until that burden of proof is reached, the diagnostic method cannot legally be included in the PMP, King says.

That time could be sooner rather than later, with Mackay saying it has been submitted, reviewer comments have come back, and he is confident it will be accepted for publication and then potentially wider use.

“It’s a tool in a tool box,” Mackay believes.

“I would love it if dogs could be proven in the peer-review process too as I see qPCR testing as quite complementary to the dogs. If they indicated on a stack of boxes, or a pallet, then you could follow with the diagnostic test to confirm infection.”

Massey University vet Scientist Dr Neroli Thomson ran the Foulbrood Detection trial and plans to have the findings published.

Sniffer Dogs

Dogs have been used by beekeepers as a tool to detect AFB in beehives for several years now and research to verify their accuracy in spore detection in a clinical setting has been completed and is being written up, as detailed in Passing the Sniff Test in our February issue.

Like with the new Foster method of qPCR testing, the Agency will not adopt the use of sniffer dogs until the research is fully proven in the field. This could be a challenge for the industry as research costs ramp up.

Advocates for the use of AFB sniffer dogs believe they could be a valuable addition to both beekeepers and Agency though, such as Frank Lindsay detailed in AFB Dogs Dilemma last month.

“Correctly trained dogs have the ability to cover a large amount of hives in a short space of time,” says Manawatu beekeeper Jason Prior, owner of DownUnder Honey.

“For a beekeeper wishing to eliminate AFB from their operation, this can help identify hives which will require closer scrutiny. For the Agency, it could mean AP2 inspections are better targeted to apiaries or hives in which dogs indicate there is greater likelihood of clinical AFB.

“Further to those apiary and hive visits, dogs could play a crucial role in identifying AFB infected equipment stored in sheds. If we are truly serious about elimination, then removing this gear from beekeeping sheds is critical.”

In addition to those uses, sniffer dogs may also be able to assist within any regional elimination plan, by helping identify AFB hives before they are migrated and the disease spread into new areas.

Phage Therapy

While some countries allow antibiotic treatment of AFB infected colonies, this is illegal in New Zealand. However, there is growing hope that a preventative treatment might be possible in the form of “phage therapy” and a New Zealand lab is playing a role in the global research.

Scientists on the ABAtE research programme Danielle Kok, left, and Dr Heather Hendrickson are seeking to develop a hive treatment system which could be a game-changer in the task of AFB elimination.

Bacteriophages are a form of virus that infects bacteria, eventually killing off their host. They are however the most numerous entity on the planet and found everywhere. Finding the right mix of phages to target the AFB-causing bacteria Paenibacillus larvae – a task researchers have described as “finding a needle in a stack of needles” – is required before any preventative can be designed. Such AFB-targeting phages were first found in North America in 2013, but the search continues for the right mix, including in New Zealand where the ABAtE project are searching for phages specific to New Zealand’s strains of AFB.

“We have successfully formulated and tested multiple bacteriophage cocktails in the laboratory setting and found excellent activity against the majority of P. larvae strains from here in NZ,” says Dr Heather Hendrickson who leads the ABAtE research, now based at Canterbury University.

“The work continues though as we perfect these cocktails for practical use, test them in honey bees, and expand our collection of bacteriophages to kill the remaining strains that are resistant to the bacteriophages we have now.”

Therefore, although promising, any potential treatment or preventative using phage therapy is a long way off being accessible to beekeepers or the Management Agency. If it came to fruition though, phage therapy could play a significant role in AFB elimination.

Onwards

From the national compliance manager’s perspective though, human inspection of hives is still the best option available to locate infected colonies. Therefore, other tools or technologies should always be compared against beekeeper inspection to ascertain their value.

“Clinical inspections have stood the test of time,” King says.

“So new technologies need to have proven significant cost savings compared to clinical inspection, or significant performance advantages over clinical inspection. Ideally, if there's new technologies that are both cheaper than clinical inspection and more effective, well, that's your eureka moment that is really going to change things.”

Despite any technologies that prove themselves, New Zealand’s effective management of AFB and any hope of elimination is still 100 percent reliant on beekeepers taking the appropriate remedial action once infected colonies are identified.

“People can get so excited by new technologies that they forget the fundamental principles that you need to apply to those technologies,” King explains, adding “elimination can only be achieved by finding AFB and destroying it before it infects other beehives”.


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