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3Rs at Pirbright

Applying the 3Rs at Pirbright

Two calvesThe principles of the 3Rs, Reduction (in numbers), Refinement (of procedures) and Replacement (with laboratory procedures) were developed over 50 years ago as a framework for humane animal research.

Improvements in veterinary medicines and diagnostics are the result of years of research and much of the time is spent doing research in laboratories (in-vitro). However, the sheer complexity of viral diseases and the hosts’ immune responses to them means that research with animals (in-vivo) is essential to better understand the disease and to develop new methods of control.

At The Pirbright Institute this usually entails working with the species for whose improved health the research is directed (cattle, poultry, sheep and pigs). We also use small numbers of mice and rabbits in our research.

Whilst the number of animals used at the Institute is tiny compared to the millions of animals that benefit from the Institute’s research, we strive to apply the principles of the 3Rs for the benefit of animals used in research and for the quality of the data that they yield.


African swine fever virus (ASFV) kills virtually 100% of the pigs that it infects. All attempts to date to make a killed vaccine against it have failed. It is therefore still necessary to use primary cells derived directly from pigs to grow the virus. However, the Institute has reduced the number of pigs that are used to obtain the primary cells following the discovery that porcine bone marrow cells produce more virus than the previously used porcine alveolar (lung) macrophage. Institute researchers are investigating host factors that determine the susceptibility of cells to ASFV infection in order to develop laboratory-grown cell lines that support replication, obviating the need for primary cells.
Foot-and mouth disease virus (FMDV) is an extremely variable virus. Successful control involves identifying the right vaccine to use and demonstrating the efficacy of batches of the selected vaccine. This used to involve vaccination of cattle (a group of cattle for each vaccine to be assessed) which would then be challenged (inoculated) with virus. The Institute now uses serologically based methods that have greatly reduced both the number of cattle that are used and those that are challenged.

Together with mathematical modellers at Glasgow University, researchers are working towards a robust and challenge-free computational based model for the assessment of FMD vaccine efficacy.

Colonies of midges and mosquitoes bred at the Institute to study diseases which can be spread by biting insects were traditionally fed using mice. The Institute has developed a method by which the insects can be fed successfully using artificial membrane based feeding units so that mice are no longer required for this purpose.
Ticks transmit a wide range of diseases caused by viruses, bacteria, protozoa and helminth worms to livestock, companion animals and humans. In addition, ticks themselves can cause serious damage and loss of productivity when feeding on livestock such as cattle.

Traditionally, laboratory study of tick-borne pathogens and development of methods to control ticks and the diseases they transmit requires maintenance of ticks by feeding them for up to four weeks on suitable animal hosts (for example rabbits, gerbils, sheep and cattle).

However, continuous tick cell lines derived from the tick vectors of many of these pathogens are increasingly being used as alternatives to whole ticks in experiments to increase fundamental understanding of the relationships between ticks and pathogens, and the mechanisms of pathogen acquisition, survival and transmission by the tick to the vertebrate host. In addition, tick cell lines are now being explored as model systems to understand how acaricides (insecticides specifically targeted at ticks) work, how ticks develop resistance to acaricides, and to find novel targets for new acaricide development. In both cases, most of the preliminary and developmental experiments can be carried out in vitro in tick cell lines, before moving to whole tick feeding on vertebrate hosts in the final stages, thereby greatly reducing experimental animal usage and enabling many more laboratories that lack tick feeding facilities to contribute to this research field.     

The Tick Cell Biobank was created at the University of Edinburgh in 2009, using funding from the Wellcome Trust, to house almost all of the world’s surviving tick cell lines. At that time these numbered around 50; the majority were established from the 1970s onwards by just three scientists: Tim Kurtti and Ulrike Munderloh at the University of Minnesota and Lesley Bell-Sakyi in Edinburgh. The Biobank moved to The Pirbright Institute in September 2012 with Dr Lesley Bell-Sakyi.

The Tick Cell Biobank now holds nearly 60 cell lines derived from most of the vectors of the important tick-borne diseases of domestic animals and humans (anaplasmosis, babesiosis, cowdriosis, theileriosis, borreliosis, ehrlichiosis, rickettsiosis, African swine fever, Nairobi sheep disease, tick-borne encephalitis, Crimean-Congo haemorrhagic fever etc). New cell lines are currently being developed from additional tick species of medical and/or veterinary importance.

Tick cell lines are supplied to recipient laboratories under suitable MTAs and at affordable cost (taking into consideration ability to pay). To increase the uptake and improve the rate of successful transfer to the new laboratory, free training is provided on request to the recipient scientists. Since September 2012, 175 tick cell lines have been distributed to over 40 research laboratories in UK, Europe, Asia, Africa, North and South America and 41 recipient scientists have been trained.

More information can be found on the Tick Cell Biobank pages.

Formal statistical review of animal experiments is part of the ethical review process at The Pirbright Institute to ensure that all studies are designed appropriately and have sufficient statistical power to detect effects that are biologically meaningful.

Pirbright's in-house statistican, Dr Simon Gubbins assists researchers with their grant submissions to optimise animal numbers and experimental design.

Experiments are designed based on the magnitude of effect that needs to be detected for a study to be informative (e.g. difference in levels of viraemia; proportion of animals protected by a vaccine), the expected level of variation amongst animals and the power (typically 80%) and confidence (typically 95%) required. In most cases, the required number of animals can be determined by standard methods. For more complex designs, however, group sizes may need to be determined by simulating the statistical model underlying the experiments in computer packages.

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