Equine Influenza: A laboratory learning experience in an exotic disease response
Mobile portacabin units at the
Local Disease Control Centre
In the final quarter of 2007, the Investigation and Diagnostic Centre was fortunate enough to have staff members (two technicians, a scientist and a team manager - Katherine Garnett, Ushma Desai, Wlodek Stanislawek and myself, respectively) from the Animal Health Laboratory, Wallaceville assist with the exotic equine influenza (horse flu) response in Australia.
Our mission was to gain first-hand experience of a full-scale response and use this to assist with our own preparedness in New Zealand. We were aware that molecular diagnostic techniques were now suitably reliable and rapid for frontline response screening, but that there were limits, especially in the bulk manual handling steps. It was invaluable, therefore, to gain first-hand experience of these techniques in a response - to observe that appropriate automation could increase output at least tenfold, and that automation helps maintain an effective and healthy workforce over prolonged periods.
The response
An outbreak of equine influenza was confirmed on 24 August 2007 in New South Wales and a full-scale response immediately followed. The coordinated national response plan (AUSVETPLAN) was initiated by Canberra in New South Wales and also in Queensland, where fewer cases have been detected. Immediately following confirmation of the outbreak, there was a national clampdown on all horse movements. The rapidity with which the initial results were reported (within six hours of sample receipt) and the subsequent clampdown restricted the disease to the two states and prevented a national outbreak.
Up until 24 August, Australia had remained free of equine influenza (as New Zealand remains). The intention is to eradicate the disease through movement restriction and isolation, together with a huge screening programme and vaccination.
Equine influenza
The current circulating (RNA) virus is from the H3N8 subtype of the orthomyxovirus family. The influenza virus is able to infect all equid species and thus all horses are susceptible. This virus causes an acute, highly contagious disease that is not usually fatal in adults but can be for foals, aged and infirm horses. The major clinical signs are pyrexia (fever) and a dry hacking cough and overall lack of performance. Fit and healthy adults usually clear the disease within 10 days and there is no recognised carrier state.
There have been no cases reported of transmission to humans under natural conditions. The disease, therefore, has economic consequences rather than posing any risk to human health. In Australia, this means costs of the response are shared between government and industry.
The exact costs incurred from the disease remain uncertain, but one estimate suggests that $A4 million per day is being lost from the economy (www.horsetalk.co.nz/news/2007/11/012.shtml 
) and that the cost of the eradication had reached about $A36 million.
The cause of the initial spread throughout New South Wales remains uncertain.
The experience in New South Wales
The outbreak was first confirmed by the virology laboratory at the Elizabeth MacArthur Agricultural Institute (EMAI), Menangle, New South Wales, under the direction of Dr Peter Kirkland. This was where we were seconded and also where the Local Disease Control Centre (LDCC) was stationed.
Upon arrival we were immediately inducted with the rules and regulations of the site, given security/photo-ID cards and shown around the ever-expanding campus - which resembled a set from MASH with its constant activity and growing collection of mobile portacabins.
The EMAI/LDCC was a real hive of activity: importantly there was a canteen and food supply for all people working on the response, there was the control centre where epidemiologists, logistics staff and mappers worked and twice a day there was a debrief. Heads of section were easily identified with coloured bibs - important with a constantly changing workforce.
All laboratory-generated results were first approved by the Chief Veterinary Officer (CVO) prior to release to the LDCC, for their input into the epidemiological algorithms. Informing the CVO of the results before their release ensured there were no surprises at the highest level. This reinforced the importance of the laboratory results and the part they played in the response. The LDCC used the data to help determine where vets might be deployed around the state and for indicating where disease-free and infected properties were.
It was clear from the word go that the response was a massive undertaking, requiring energy, effort and commitment and that we were lucky to have the chance to experience it.
Laboratory perspective
Our posting to New South Wales was organised through the logistics team at the LDCC and we were to be on site for a minimum of two weeks, working six days in every seven. All 25 virology staff were working in blocks of six days and there was a shift roster. In that time, we were brought up to speed with local procedures for the real-time PCR (polymerase chain reaction) or the ELISA (enzyme-linked immunosorbent assay) tests and also able to assist with specimen reception. These procedures require concentration, accuracy and high levels of technical aptitude but are often subtly different between laboratories. Therefore, being able to demonstrate technical proficiency in a short timeframe meant that our Australian counterparts were able to benefit rapidly from our quality technical and scientific input.
Upon arrival, it was very clear just how busy the laboratory was - often handling more than a thousand samples a day (nasal swabs and sera).
Specimen reception
This is generally regarded as the most important step in the processing of any samples within a laboratory - samples need to be correctly matched to paperwork; paperwork needs to provide the appropriate information from the submitting vets; the samples need to be intact; samples themselves need to be labelled sequentially for effective lab tracking and traceability; data needs to be entered correctly into the laboratory information management system (LIMS).
It was really useful to see that, in order to clear so many samples and have them ready for processing in the same day, all staff could fit in to the specimen reception process at any stage.
At times, the specimen reception bay was occupied by 10 people, with the sole aim of getting the samples ready for the molecular diagnostics testing in the evening.
Although specimen reception was resource hungry, it did allow samples to be set up for testing before any data needed to be entered into the LIMS.
A tight squeeze, but all staff could
fit into the specimen reception area at
any one time
Polymerase chain reaction (PCR)
The PCR method employed in Dr Kirkland's laboratory is a real-time PCR. One of the benefits of this method is that the rate-limiting step of gel electrophoresis is removed and product visualisation is automated through laser technology. This technique was combined with high-performance automation and robotics to provide a reliable, rapid and robust diagnostic tool that was extremely user friendly. Literally hundreds of nasal swab samples were being screened every day by up to two technicians. High-performance automation was utilised in the rate-limiting step of nucleic acid extraction from the swab samples.
Serology
Antibodies raised in immunological response to influenza viral antigens can be detected in sera by the ELISA test. This assay relies on the specific affinity of antibody for its particular antigen (part of a viral protein). ELISA technology has been used since the early 1970s and has become a mainstay in many laboratories that utilise serology. It has become a flexible tool and is useful to screen bulk numbers of serum samples. However, when large numbers (hundreds to thousands) of samples are to be tested, then automation again becomes a useful tool; robotics interfaced with effective software has removed the laborious tasks of plating out sera.
Automation
While the specimen reception process relied heavily on staff resources to prepare samples for testing, the actual diagnostics and testing procedures utilised high-throughput technology and automation.
It was useful to observe the benefits of automation, and how it could be utilised to manage the large numbers of samples consistently and over long periods. Such technology enabled the laboratory to continue with business as usual, maintain staff morale and welfare and reduce the incidence of repetitive strain injuries.
Conclusion
It has been invaluable to experience a full-scale response at first hand and to observe the interfacing of automated technology with modern and traditional diagnostic procedures. From this, we have been able to look at our own state of preparedness with more understanding of what may be achieved, if we are ever called upon to respond to an exotic infectious disease at IDC - Wallaceville.
- Dr Clive Pigott, Immunology Team Manager, Investigation and Diagnostic Centre - Wallaceville, phone 04 894 5638, clive.pigott@maf.govt.nz
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Page last updated: 30 April 2008