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Where FMD is present, milk must be pasteurised before sale. In fact, in many municipalities selling raw milk is illegal regardless of FMD status.
Foot-and-mouth disease (FMD) is a devastating disease, but just as devastating and distracting are some of the misplaced facts shared on many a media platform. During a recent webinar presented by the Dairy Standard Agency (DSA), veterinarian Dr Mark Chimes, also Milk SA’s programme manager for animal health and welfare and member of the Ministerial Task Team (MTT) on FMD, attempted to set the record straight by sharing the facts regarding certain aspects of the FMD situation.
Pasteurisation and milk handling
Originally, all FMD milk had to be double pasteurised. However, single pasteurisation is currently allowed for milk intended for local consumption. This milk is acceptable for manufacturing dairy products, provided the products are not intended for the export market.
Pasteurisation involves heating milk to at least 72°C and then cooling it. In the case of double pasteurisation, the milk will be cooled to around 4°C before repeating the process. While double pasteurisation is still a requirement for export products, the World Organisation for Animal Health (WOAH) principle of ‘equivalence’ states that the strict application of the rules could be applied more flexibly under specific conditions.
Dr Chimes used condensed milk as an example – a dairy product made from milk that has been pasteurised once already. During processing is it again heated to over 100°C for more than five minutes. “This process is in fact more stringent than the standard double pasteurisation process,” he explained. Hence, while double pasteurisation still applies to exports, the process is interpreted more pragmatically, the emphasis being on two effective heat treatments rather than strict cooling in between.
Vaccine supply and production
During the webinar he confirmed that the Agricultural Research Council’s Onderstepoort Veterinary Research campus (ARC-OVR) was planning to ramp up its vaccine production capabilities to just under a million doses per year. The organisation is planning to build a new facility which could eventually produce up to ten million vaccine doses annually. However, the parastatal was still awaiting funding to build the facility, so this level of production is still several years away.
The country will therefore remain reliant on vaccine imports, needing between 12 and 14 million doses to vaccinate the national herd once, and the same number again six months later for booster doses.
Vaccination rules and trade
Can products from voluntarily vaccinated animals be exported? The short answer: Yes. If animals are healthy and not infected, he said, vaccination does not restrict trade. However, farms near outbreaks or under quarantine may still face additional requirements, such as double pasteurisation.
And may raw milk producers continue operating if the herd is vaccinated? Yes again – provided the animals are not infected with FMD.
He explained that export regulations do not change once animals have been vaccinated, since vaccinated animals are still considered healthy and vaccination does not imply infection. Therefore, the products of vaccinated animals may be exported.
Vaccine function and immunity
One of the most persistent concerns among producers is whether vaccination will leave traces of FMD in animals. Dr Chimes assured producers that all the vaccines currently used in South Africa are manufactured with inactivated (dead) FMD viruses and cannot cause disease. Although animals produce antibodies post vaccination, with DIVA (differentiation of infected from vaccinated animals) vaccines it is possible to distinguish between vaccinated and infected animals.
There are seven different strains of FMD globally with only SAT1, SAT2, and SAT3 present in South Africa. It is important to understand that an animal will only spread the strain with which it is infected. However, it is possible for an animal to become infected with multiple strains simultaneously.
Unfortunately, no cross-immunity exists between the different SAT strains. In other words, if an animal is immune to one SAT strain, whether due to vaccination or natural infection, it is not protected against the others. One of the most critical aspects is herd immunity. While the goal is to vaccinate 100% of animals, only about 80% of the national herd needs immunity for us to effectively control the disease.
It is also important to note that not all vaccines are equal in terms of how long immunity lasts. Water-based vaccines are fast acting, but immunity is short-lived. As a result, these vaccines require boosters within four to six weeks, and then every three to four months. On the other hand, oil-based vaccines act slower but afford longer-lasting immunity. They typically provide immunity for at least six months. Dr Chimes assured producers that all the available vaccines have been evaluated for their efficacy.
Movement and biosecurity
Owners of quarantined livestock are not permitted to move any of their animals, except to abattoirs. In surveillance zones, animal movement is only allowed based on a permit from a state veterinarian. Rapid (cow-side) FMD tests are not allowed in South Africa, as these tests are not 100% dependable and there is a risk of misuse to certify animals as disease-free. False negative test results could lead to producers unknowingly selling infected animals.
Furthermore, producers are required by law to report the FMD status of their farms to the state veterinarian, neighbours, and milk processors. In addition, raw (unpasteurised) milk may also not be sold from infected farms. Where FMD is present, milk must be pasteurised before sale. “In fact, in many municipalities selling raw milk is illegal regardless of FMD status,” Dr Chimes added.
Production and economic impact
Generally, vaccination does not affect milk production, but in rare instances a cow may experience a slight temporary drop in production due to a mild fever post vaccination. FMD causes somatic cell counts (SCCs) to increase significantly, resulting in tonnes of milk being discarded.
A solution could be to temporarily allow a higher SCC at farm level (e.g. up to 700 000) so that processors may accept the milk. This milk can be mixed with the milk from other farms to ensure that the SCC in the final processed milk remains within the regulatory limits. “This could help to prevent unnecessary milk losses during outbreaks,” Dr Chimes said.
There are no restrictions on the slaughter of vaccinated animals. Once an animal has been vaccinated, it can be sent to abattoirs and processed without additional restrictions, he confirmed.
Timeline and outlook
South African dairy farming will return to normal once 80% of the herd has been vaccinated; this will significantly stabilise conditions. However, sporadic outbreaks are likely to continue for several years, and a full recovery of the country’s FMD-free status will take much longer.
Dr Chimes reaffirmed the fact that vaccinations are safe and crucial if the country is to overcome the FMD situation. Most international trade restrictions relate to FMD infections, not vaccination. “The biggest challenge remains the supply, logistics, and coordination of vaccines and vaccination.” – Susan Marais, Plaas Media
For more information, send an email to Dr Mark Chimes at mark@dairystandard.co.za or visit the Dairy Standard Agency’s website at www.dairystandard.co.za for more information regarding milk quality and regulations.
