All creatures great and small

If we want secure food supplies and an ability to tackle emerging disease – we need to turn our attention to animal health. No longer considered the poor cousin to human health labs, animal diagnostic laboratories have changed beyond recognition in the last 20 years. Nigel Lincoln looks at some of the breakthroughs that have driven the change

At a recent meeting in Brussels, President of the European Animal Veterinary Laboratory Diagnosticians (EAVLD), Dr Willie Loeffen, said that laboratory diagnosis used to be 99% labour and 1% technology, but now it is the other way round. That may be a slight exaggeration, but it is a point well made. Technological advances over recent decades have undoubtedly transformed the way animal health laboratories work.

Gone are the days when laboratories were staffed by bacteriologists and virologists whose main skill was isolating and identifying pathogens by incubating samples from sick animals. In many cases it was a difficult and slow process, requiring both practical skill and scientific knowledge, with an ever-present potential for false results due to contamination or bad judgement. In some cases, notably for many viruses and some fastidious bacteria, it was just plain impossible.

These drawbacks meant that veterinarians used the laboratory service mainly to confirm the differential diagnosis of individual animals based on the clinical presentation. Veterinarians and farmers had to wait days or even weeks to make decisions. Not surprisingly, one of the main uses of diagnostics was simply to confirm the cause of death.

In the past 20 years, the advent of new technologies has revolutionised the role of the laboratory. Although some culturing is still used, the vast majority of the work is based around equipment that can process hundreds of samples, quickly and far more accurately than ever before, as Dr Christina Boss, European Animal Health Consultant with Life Technologies explains:

“Veterinary diagnosis used to be very basic and relied a lot on the ability of technicians to interpret results correctly. The use of device-based technologies, such as PCR, has removed that subjectivity and given us tests that are far more sensitive, selective and reliable.

“Not only has that changed the laboratory environment, it has also fundamentally changed the way we apply diagnostics to food production animals. We can now use these tools to monitor herd health and to look for disease trends, so we can pre-empt many issues before they happen.”

According to Dr Boss, whole groups of animals can now be treated as if they were a single unit. They can be tested to see the level of infection within a group and how it compares with other herds in the region and how it changes over time – even if there is no evidence of a disease outbreak. It is like being able to look under the surface at the rest of disease iceberg, she says.

Mycobacterium avium subspecies paratuberculosis (MAP) is a case in point. This bacterium infects dairy cattle, and other mammals, and can cause a range of symptoms including diarrhoea, wasting, and a dramatic drop in milk yield. However, many infected cows remain asymptomatic and pass bacteria onto other cows and their own their calves – thus keeping the infection circulating within the herd. MAP infection (known as Johne’s disease) is one of the most economically damaging diseases in dairy herds worldwide.

In the past, MAP diagnosis relied on growing and identifying the organism from faecal samples taken from sick animals. However, that can take up to 16 weeks, by which time the infected cow may have died anyway or infected many others. Using this system, effective control of the infection was not really a practical option.

The advent of commercial ELISA technology in the 1980s offered a significant advance for diseases like MAP which remain hidden in herds. It meant entire dairy herds could be tested much faster and more accurately using ELISA to identify the level of sero-conversion – although the slow and unpredictable serological response to infection means that MAP ELISA generally has a sensitivity less than 50%.

Many ELISA tests have a sensitivity which is much higher than that, and the technique has become a staple in most animal testing facilities. ELISA has allowed whole groups of animals to be tested for a range of different pathogens, and so has helped make disease surveillance and herd health monitoring a realistic possibility.

However, an equally big advance in what veterinary laboratories could offer veterinarians and their farmers was the development of real-time PCR technology in the late 90s:

“For the first time veterinary laboratories could give veterinarians a confident ‘yes’ or ‘no’ in a matter of hours. And that meant it was possible to screen entire herds and identify the high MAP shedders and cull them to improve the overall herd health,” said Dr Boss.

“The same is true of many other common diseases of production animals: PCR has transformed the work of veterinary laboratories by providing quick, sensitive and reliable results. And not only does it provide quicker and more reliable information to veterinarians, but it also reduces the risks to laboratory technicians associated with growing organisms that can potentially infect humans.”

PCR has the ability to detect small amounts of specific genetic sequences, so it can detect the presence of bacteria and viruses at a very early stage of infection with high specificity and selectivity. Unlike ELISA, it does not rely on development of antibodies by the animal – so there is no time lag between initial infection and the development of a positive test. And PCR can be based on a much wider range and more difficult sample matrices, such as semen, oral fluids etc.

“Both of these technologies are now being used together to improve our management of food producing animals. Particularly in screening programs, laboratories will often use a combination of both techniques to provide a definitive profile of herd health.”

Perhaps the biggest impact that new technology is having on laboratories, is in the way animal health is managed on the farm. Whereas in the past, veterinarians generally used diagnostic laboratories in a very reactive way – to find out what had killed an animal or what caused an outbreak of disease in the herd or flock – now the laboratories are helping veterinarians take a far more pro-active stance.

“They can help the veterinarian decide which vaccination program should be used in a particular herd, for example, and to check how effective it has been. They can provide the basis for disease eradication and for surveillance and biosecurity to maintain disease-free status.”

Perhaps the most significant development in recent years has been the application of next generation sequencing in research. The ability to sequence the whole genome of animal pathogens quickly and accurately promises to deliver even more accurate diagnostics – including tests which can differentiate between sub-types of virus – and thus provide the basis for very specific treatment or vaccination.

“In the past, it took us years to identify a new pathogen,” said Dr Boss. “With the Schmallenberg virus, which appeared in Europe at the end of 2011, it took just four weeks. And within another 4 weeks, the first commercial PCR test was on the market.”

Next generation sequencing has the potential not only to reveal which bacteria or viruses are present in a group of animals, but exactly which subtypes and their likely virulence based on differences in the sequence of nucleotide bases. One day it may even tell us which treatment will work in an individual animal based on its own genetic make-up. With growing concern over the use of antibiotics, this kind of targeting could provide the basis for far more responsible usage in farm animals.

According to Dr Boss, researchers are already well on the way to developing new and better diagnostic tests based on genome libraries generated by whole genome sequencing technologies. Life Technologies is already using this approach to investigate PRRSV (Porcine Reproductive and Respiratory Syndrome Virus) in conjunction with a number of laboratories in the US and Europe, and the initial results look promising.

One of the areas where sequencing has already shown its potential is in the so-called emerging diseases, such as bluetongue, SARS, West Nile disease and Schmallenberg virus. Emerging diseases are those that are caused by apparently new types or strains of pathogen, or by known pathogens that start to appear outside their usual geographic location or suddenly increase in importance. It is a threat that European authorities take very seriously. They recently announced their intention to extend and strengthen the Early Warning and Response System (EWRS) which was originally set up in 1998 to safeguard human health against emerging disease threats.

“The speed of response that we have seen in recent cases was helped by the fact that European animal health laboratories now collaborate to a much larger extend than ever before – partly because we need to pool resources to protect our livestock, and food source, against emerging diseases,” said Dr Boss.

“We need to maintain the health and welfare of production animals in the face of increasing demands on their productivity if we are to safeguard our food supplies in the future.”

Although bacterial culture is still used in some cases, animal health laboratories no longer look like the bacteriology labs of old, with large incubation chambers and racks of Petri dishes. The modern lab is equipped with banks of integrated workflow devices, many of which are linked directly to computers for displaying results. Today’s veterinary diagnostician is more systems analyst than bacterial gardener.

Many production animal health issues are disease complexes, typically caused by infection with two or more different pathogens. One of the areas that Life Technologies and other diagnostic suppliers are investigating is the development of multiplex diagnostics – a single test that can provide a profile of all the different pathogens involved in a particular outbreak.

Another area of development that is often mentioned is the development of instant ‘cow side’ tests which the veterinarian can use to confirm an initial diagnosis on the spot. So does that mean that the days of the veterinary diagnostic laboratory are numbered?

“There will always be a need for laboratory-based diagnosticians,” said Dr Boss. “Cow-side tests may provide a first guess diagnosis in some diseases, but veterinarians will still need to send samples to the laboratory for further information about the identified pathogen. This kind of test is very useful, but in the wrong hands it can cause more harm than good.”

According to Dr Boss, that reveals the critical factors for using diagnostics effectively: knowing the limitations of any particular test or technique, and knowing when and where they can and cannot be applied.

“Unfortunately the veterinary schools lag behind and are not able to keep up with the fast-moving commercial market. So even the newest veterinarians often struggle with the best use of diagnostics: what samples to take and when, and what test to apply.

“Government laboratories tend to communicate with and educate the veterinarians in their region more broadly with regards to region-specific programmes. Independent laboratories tend to have a closer relationship with veterinarians because they develop more individual customer contact. As technology continues to develop at a rapid rate, veterinarians cannot possibly keep up with everything, so the laboratory will become an invaluable source of advice and information on disease management for veterinarians.”

Life Technologies obviously appreciates the potential that molecular technology has for improving diagnostic services and thus helping to improve animal health and productivity in the food producing sector. So how does Dr Boss think the animal health laboratory will change over the next ten years?

“Diagnostic laboratories are an increasingly integral part of animal health management on European farms, and that trend will continue I’m sure. Devices that can run high volumes of ELISA, PCR and, eventually, genome sequencing, will become a standard fixture in all laboratories. In some ways it is impossible to predict what will happen in the next 10 years – that’s why it is so exciting working in the diagnostics field right now.”

Author: Nigel Lincoln graduated with a BSc in human biology in 1981. Having worked as a medical journalist, copywriter and creative director for healthcare PR and advertising agencies, freelance writer, and briefly for a pharmaceutical company, he has spent the last 30 years writing for and about the medical and veterinary industries.