More advanced diagnostic test systems to identify animal diseases become increasingly important within animal husbandry. Rapid and exact diagnosis can aid the quick control of epidemics and animal suffering, as well as serious commercial damage. However, if these test methods are not accurate enough, results may be misinterpreted. AGES veterinarians and their cooperation partners at the University of Leipzig and University of Veterinary Medicine, Vienna were presented with an award for their research on this topic at the largest European congress in the field of Porcine Medicine. Their paper on the “Influence of spray-dried plasma in swine feed on PRRSV antibody diagnostic in oral fluid” received the poster prize.
This paper was about the identification of the sudden and apparently inexplicable appearance of PRRSV antibody-positive results in an up-to-then PRRSV negative rearing herd by the AGES veterinarians from the segment Animal Health, headed by Univ.-Prof. Dr. Friedrich Schmoll. PRRSV stands for Porcine Reproductive and Respiratory Syndrome Virus, which can cause fertility disorders, abortions, the birth of weak piglets and pneumonia in swine. During the reappraisal of the case, it was found that the test results could be corrupted by feedstuff ingredients.
Saliva samples show the health status of a herd
The AGES Institute for Veterinary Examinations in Mödling works on the development and optimization of diagnostic test systems and sampling schemes in cooperation with partners at the University Leipzig and University of Veterinary Medicine, Vienna. Tests on saliva samples to determine the status of animal health in herds is currently claimed to be an attractive, cost-effective and animal-friendly method.
The saliva is acquired from chewing ropes that are hung in the livestock areas. Curiosity and animal play instinct make the pigs chew the ropes, which in turn soak up the saliva. The saliva is then squeezed from the rope and is used for determining pathogens or antibodies.
Both the animals and veterinarians benefit from this method because the taking of blood samples and demanding and stressful holding of the animals can be avoided. Additionally, a smaller number of samples is enough to draw conclusions for an entire group, unlike blood samples for which a much greater number of random samples must be taken and each one must be tested individually. The sampling frequency can be increased when using a chewing rope which means that higher safety can be achieved in the monitoring of herds free of specific pathogens, such as PRRSV. The analysis of saliva samples also saves diagnosis costs.
No one hundred percent safety
A small drawback that should not be neglected is the accuracy (specificity) of the method. The illustration of this disadvantage and resulting consequences were the subject of the award-winning research project.
The sudden and apparently inexplicable appearance of PRRSV antibody-positive test results in an up-to-then PRRSV negative rearing herd gave AGES a reason to clarify the situation. Saliva samples were taken from the herd using chewing ropes and tested positive on PRRSV antibodies in a regional laboratory. Such a test result causes immediate uncertainty, as it may cause problems at the farm in question and the pig facilities supplied by that farm that can even include liability issues.
During the reappraisal of this case, clear evidence was found that test results from saliva samples can be corrupted by feedstuffs: the feed contained spray dried blood plasma, a feed additive that can have positive effects on the health and growth of piglets. This feed also contained antibodies to pathogens.
Feeds and saliva and blood samples from pigs of different ages were examined for these tests: milk replacements, weaning piglet feed and rearing feed contained blood plasma additives – while other feeds did not.
All feeds containing blood plasma tested PRRSV antibody positive, while those without plasma yielded clearly negative results.
Not one blood sample from the pigs examined showed traces of PRRSV antibodies. They were all negative. The saliva samples of the pigs that had received feed without plasma additives did not test positive for PRRSV antibodies, unlike the saliva from the pigs that had been fed plasma-containing feed or milk replacements. Thus, the tests conducted by AGES could clearly show that the antibodies came from the feed and milk replacements containing blood plasma and that there was no infection within the swine herd.
European Pig Veterinarian Congress – Award for AGES Veterinarians
The congress is the largest in the field of porcine health in Europe with about 1,400 participants and is held on an annual basis by the European College of Porcine Health Management and the European Association of Porcine Health Management. This year’s event in Nantes, France, saw 54 presentations and 287 posters on a number of different topics in porcine health. The AGES segment Animal Health was represented through three more posters on the subject of porcine reproductive and respiratory syndrome virus and alternative sampling materials, in addition to the award-winning poster:
Sattler T, Pikalo J, Verhovsek D, Wodak E, Schmoll F (2015): Influence of spray-dried plasma in swine feed on PRRSV antibody diagnostic in oral fluid. 7th European Symposium of Porcine Health Management, 22.-24. Apr. 2015, Nantes, Frankreich, Proceedings Nr. P082
Sattler T, Pikalo J, Wodak E, Entenfellner F, Steinrigl A, Revilla-Fernández S, Schmoll F (2015): Detection of PRRSV antibodies in serum, oral fluid and dry swabs in pigs after intradermal application of highly pathogenic PRRSV type 2. 7th European Symposium of Porcine Health Management, 22.-24. Apr. 2015, Nantes, Frankreich, Proceedings Nr. P081
Steinrigl A, Sattler T, Pikalo J, Revilla-Fernández S, Wodak E, Schmoll F (2015): PRRSV and PCV-2 detection in blood and oral fluid collected with GenoTube swabs. 7th European Symposium of Porcine Health Management, 22.-24. Apr. 2015, Nantes, Frankreich, Proceedings Nr. P068
Steinrigl A, Voglmayr T, Mößlacher G, Schmoll F, Leeb B (2015): A longitudinal field study to assess the applicability and robustness of oral fluid PRRSV RT-qPCR and ELISA. 7th European Symposium of Porcine Health Management, 22.-24. Apr. 2015, Nantes, Frankreich, Proceedings Nr. P154.