With the introduction of the qPCR PCV2 test, BioChek now has a wide range of three different diagnostic PCV2 tests. Alex Eggen, veterinary consultant for the pharmaceutical and pork-producing industry, believes the qPCR test is a valuable extension for both pig farmers and veterinarians: “qPCR makes the PCV2 diagnostics of BioChek complete. From now on virtually any question involved in tracking down and monitoring PCV2 can be answered with these three diagnostic tools.”
When Alex Eggen began working at Intervet (known today as MSD Animal Health) in 1985, the name PorcineCirco Virus type 2 (PCV2) was still entirely unfamiliar. The first known instance where PCV2 played a role was reported in 1991 among Canadian piglets. At the end of the 1990s the disease caused by PCV2 was only acknowledged by a few scientists and they also began to attract more attention internationally. At that time, Alex Eggen was involved in the research and product development of the first vaccines against PCV2. The introduction of these vaccines was a phenomenal success. Only then did the pork industry realise that the PCV2 virus was behind the enormous losses being suffered. Today he is one of the pre-eminent experts when it comes to PCV2. “The PorcineCirco Virus type 2 occurs worldwide. The circovirus infections are responsible for acknowledged clinical phenomena such as runts, kidney and skin problems and respiratory complaints. Alongside these clinical images, circo infections are also notorious because of their immune-suppressing effect, for growth retardation, increased antibiotic use, increased mortality and slaughter age pigs which are no longer uniform. And that’s something that no pig farmer hopes to encounter!” says Eggen.
For a healthy operation, Eggen believes it is crucial that pig-farmers keep collecting information on the health status of their animals. “With the right information they can prevent the risk factors in their operations, and the damage caused by PCV2 virus, for instance. Here too the old adage applies: knowledge is power! So monitoring with diagnostic tests is essential. Only then will pig-farmers know the PCV2 status of their operations. To offer an example: in an endemically infected operation with subclinical infection, animals may experience a growth retardation of between 20 and 25 grams a day which the pig-farmer will not see with the naked eye. In consultation with his veterinarian, he may decide to investigate the cause of this growth retardation. Only by testing the animals concerned will they discover that the PCV2 virus is active and is possibly the reason for this. Once they know this, they can consider taking adequate measures to get PCV2 under control.”
With the expansion of qPCR as a diagnostic test for PCV2, BioChek now has three different PCV2 tests in its range. All three tests make their own contribution to the information a pig-farmer and his veterinarian need to monitor whether they have the PCV2 virus under control. Alex Eggen: “The PCV2 ELISA is the best-known test. It’s used to show antibodies in (young) piglets, growing pigs, gilts and sows. The ELISA test has several objectives. For instance, the right vaccination time can be determined, or the reaction to a vaccination can be measured. The test can also be used to show whether the animals have or have had a field infection. So the test can be used for a variety of purposes.”
BacuChek is a relatively new concept, for which Eggen says there is increasing demand. BacuChek can show whether piglets have been properly vaccinated or not. “It’s a relatively easy to administer blood test for piglets between 7 and 10 weeks old. To be sure that the vaccination has been done well, the serum sample is tested for both antibodies and antibodies against the baculovirus. The PCV2 vaccines produces in a baculovirus vector system contain both PCV2 antigen and some baculovirus remnants. After vaccination, this produces antibodies in the pig against the baculovirus, which can then be used as a marker. These antibodies are shown with the BacuChek and the pig-farmers have quick and clear access to the vaccination status: the piglets have or have not been vaccinated. An excellent testing method, because the presence of antibodies against PCV2 is not proof of vaccination. At the end of the day you don’t know whether the titres found are the result of a field infection or the vaccination.”
qPCR: shows virus material
Both the ELISA test and the BacuChek only show antibodies. The qPCR test by contrast, shows the virus material. And that has benefits, says Eggen. He offers an example. “When the ELISA is used at the end of the growing period to screen the animals for PCV2 antibodies, but for that moment this is not actually a definitive diagnosis. Because if the animals become infected with the circovirus a few weeks before they go for slaughter, antibodies have not yet developed. Antibodies only show some 2 to 4 weeks after infection, after all. So an ELISA test could register negative for these animals, even though they are in fact circovirus positive. So you would miss the right information with the ELISA. And that’s not the case with the qPCR. Once the PCV2 virus is above the test’s detection threshold you then know whether there is a PCV2 infection or not.” He explains that with the qPCR test, pig-farmers can reap an economic advantage. “It is not only the presence of the PCV2 virus which is important, but also the degree to which it is present.
The PCV2 qPCR also indicates the quantity of the PCV2 virus. The correct interpretation of the results determine whether there is damage, and also how large or small the damage is. Pigs can experience growth retardation for a couple of weeks, which can no longer be caught up. Then as a pig-farmer, you no longer have uniform slaughter age pigs, and that simply costs money. No pig-farmer wants that.”
The PCV2 ELISA test, the BacuChek and the qPCR test all give the pig-farmer and his veterinarian a huge volume of information. In practice, however, it turns out that pig-farmers don’t always use all three tests. Alex Eggen acknowledges this. “Testing is done for what a pig-farmer or veterinarian wants to know at that moment. And that varies from questions like what the ideal vaccination time is, to whether the animals are sick. And BioChek has different diagnostic tests for all these questions. If I was still working as a veterinarian, I would probably use the qPCR more often. For PCV2 one thing is important: reducing virus quantities. qPCR provides definitive answers as to whether the animals have the circovirus or not, and also whether a decline in the virus volume occurs over time. And here it answers the question: am I at risk of damage or not? That’s what a pig-farmer wants to know, because he can act quickly to limit the risk. Pig-farmers work in a carefully planned industry. Every wrinkle in the system costs money. And with today’s margins nobody can let that happen.”