Estimated reading time: 12 minutes
- This year, the dairy industry was among the hardest hit by foot-and-mouth (FMD) disease outbreaks in most provinces in the country.
- The Dairy Standard Agency (DSA) invited Dr Mark Chimes to present the protocols to follow once FMD has been confirmed.
- Once FMD has been confirmed, the state veterinarian will place the farm under quarantine.
- The quarantine period can last for up to 16 months.
- To lift quarantine, the state veterinarian will perform two inspections once 12 months have passed after day zero.
South Africa’s cattle sector faces tremendous challenges regarding biosecurity and traceability. This year, the dairy industry was among the hardest hit by foot-and-mouth (FMD) disease outbreaks in most provinces in the country, especially the Eastern Cape.
Considering the devastation FMD has caused in dairy herds this year, the Dairy Standard Agency (DSA) invited Dr Mark Chimes, veterinary advisor and manager of Milk SA’s Animal Health and Welfare Programme, to present a webinar on the devastating effect of this debilitating disease but, more importantly, the protocols to follow once FMD has been confirmed.
“FMD is a serious disease with far-reaching consequences,” he said. These include the actual losses suffered in the form of culled animals, veterinary costs and additional precautions to be taken when handling animals, milk production losses, added transport costs, culling of sick animals on the farm, maintaining quarantine for at least 16 months after day zero, and not being allowed to sell animals for at least one year.
Cutting to the chase
Three FMD serotypes are classified as South African Territory, namely SAT1, SAT2 and SAT3. It is important that producers understand a number of things regarding the spread of the disease. Firstly, it can spread over vast distances and currently the main problem in this regard is animals being moved illegally during periods of quarantine by owners who are desperate to sell their animals, as they have to cover the costs of keeping and feeding animals on the farm for longer.
Evidence shows the virus may spread via wind, while water’s role is unclear. In one case, animals sharing a water source with an upstream farm – where livestock were FMD positive – were suspected to be infected through that water.
Producers should also take care when buying manure from other farms or feedlots to spread on their fields. Contaminated manure can lead to animals being infected when they graze those fields.
Carrier animals may show no signs of the disease, yet they will shed the virus which can lead to it spreading to other farms when sub-clinically infected animals are moved.
A study in which the throats of persons who handled infected animals were swabbed, found that the FMD virus could be extracted from their throats for up to 48 hours after exposure. Such a person can spread the virus to other farms and herds. In this case, a five-day isolation rule applies and such a person cannot go onto another farm before that period has passed. In the case of veterinarians, 48 hours of isolation should be adequate provided they wear the required protective clothing, gloves, and masks when working with animals.
Once it gets to your farm
Animals with FMD must be identified early on. Some of the clinical signs include sores on the mouth, udders, teats, hooves, lesions on the tongue, and excessive salivation.
The herd veterinarian must visit the farm to do an assessment of the animal(s). It is compulsory by law for producers to notify their neighbours if they suspect FMD, as state veterinarians are not allowed to share private information of this nature. Both parties must move their animals away from the border fences between their farms and put as much distance as possible between each other’s herds. This is certainly not the time to buy in any new animals.
Once the veterinarian has completed the assessment and the case does prove suspect, the state veterinarian will be asked to take swabs from the throat of the animal(s) so that a polymerase chain reaction (PCR) test can be done. This test is very sensitive and picks up small quantities of DNA or RNA viruses. FMD is an RNA-virus, and even in the early stages the test will indicate whether an active infection is present.
A blood sample will also be taken and sent for serological testing for antibodies. Antibodies can take up to two weeks before reaching a detectable level, which means there could be a delay in the release of the test results. Antibodies can be detected up to several months after it had formed, providing a very good indication of the animal’s history. Animals can also have an infection without exhibiting any signs, which can resolve within a certain time and will show up in an antibody test.
Once FMD has been confirmed, the state veterinarian will place the farm under quarantine and, most likely, the surrounding farms within a 10km radius of the affected farm. This will include farms that have never had the disease in their herds and farms with animals that are vaccinated against FMD. The state veterinarian will visit the neighbouring farms in the area and perform the necessary tests to establish whether the disease has spread.
Quarantine is a long ride
Currently, the quarantine period can last for up to 16 months due to a number of reasons, the first being the time it takes from the disease being suspected to it being confirmed. Another two to three months will pass before reaching day zero, which is when it is determined there is no longer an active infection on the farm. This is followed by a further 12 months after which the state veterinarian will visit the farm twice, at least two weeks apart, and send bloodwork to the laboratory where it can take another three to four weeks before the results are available. Then there is the processing of all the information before quarantine can be lifted.
Unvaccinated farms: The maximum incubation period is 14 days until an animal will show FMD symptoms. That is why a 28-day quarantine period (twice the length of the incubation period) is advised to ensure that newly brought in animals don’t exhibit signs of disease. The state veterinarian will visit the farm two weeks after the last FMD-case was diagnosed to check for any new animals with symptoms, and then again two weeks later to check for any new animals showing symptoms of the disease. If all is well, day zero will be declared on the farm.
Vaccinated farms: On farms with no history of FMD but where the animals were vaccinated, day zero will be determined as the date on which the last animal was vaccinated.
Quarantine restrictions
A number of hurdles have to be overcome once a farm has been placed under quarantine. The first is the fact that quarantined cull animals can only be taken to an FMD-approved abattoir once a state veterinarian has visited the farm and issued a Red Cross permit allowing the moving of the animals. This can cause serious problems where animal numbers are accumulating, requiring extra feed and treatment. This could lead to animals having to be put down by the producer and his/her workers.
Animals may only be moved between farms with the same FMD status. Some dairies have farms where heifers are raised, or dry cows are kept. These animals have to be taken to the milking parlour once they have calved and are producing milk. If a parlour is infected by FMD, the heifers and dry cows will not be allowed to go there, even if they were vaccinated. Should a heifer/dry cow farm be infected, and the parlour not, then the producer must try to arrange taking his animals to another dairy farm where the animals are also infected, but with permission from the state veterinarian.
If both the heifer farm and parlour are infected at the same time, the animals may be moved between the two farms – also only with permission from the state veterinarian.
A major welfare issue is that of bull calves that cannot be sold at this time. This leads to limited space for all the animals, with many producers unable to rear these calves up to slaughter age. When these animals have to be culled on the farm, it can have to severe psychological effects on the producer and his/her staff who have to assist in the process.
High risk access points
FMD can easily be spread through vehicles transporting animals. Trucks and vehicles that leave the farm must first be washed and then properly disinfected. The run-off water must not reach any water sources to which the cows have access. Drivers of feed and milk lorries, technical consultants and such, are generally considered to be a lower risk as they don’t handle the animals. However, there is still a risk of the disease being brought onto the farm and these visitors should therefore only be allowed into designated areas.
People that physically handle the animals, such as veterinarians and farm workers, can also spread the disease. Personnel that handle animals must therefore disinfect their hands and clothes, while equipment such as nose tongs especially, must be disinfected between each animal. Staff must wear gloves when handling the animals and work with the healthy animals first, followed by the sick animals. They must also change their clothes on the farm before they go home, and upon their return put on clean clothing and gumboots that were disinfected overnight.
There are various types of effective disinfectants available. Do note that normal chlorine, bleach, and iodine-based products do not kill FMD. The virus is, however, very sensitive to sunlight and anything with a pH level below 6 and above 9 will kill it.
Practicalities: Movement and slaughter
Earlier this year, many of the few abattoirs in the country that can qualify as FMD-designated abattoirs, did not want the infected animals on their sites as they would lose their meat export licences. South Africa is therefore in need of more FMD-designated abattoirs where large numbers of quarantined animals can be slaughtered at a time.
An FMD-designated abattoir must comply with several requirements, such as having correct fencing in place, being able to incinerate discarded carcass parts, and shower facilities for staff members who enter and exit the premises. The carcasses of FMD animals must hang for at least 24 hours post slaughter to allow the pH to drop below 6. In addition, it must be kept separate from uninfected carcasses. This requires two cooling rooms.
The heads, tongues, hooves, and offal of slaughtered animals must be incinerated. In the early stages post day zero, the carcass must be deboned, the glands removed, and the meat on the carcass may only be used for processed products such as polony. From three months post day zero only the head, tongue, and feet need to be destroyed.
Quarantined animals can only be moved to an FMD-designated abattoir under a Red Cross permit issued by a state veterinarian who will check the animals on the farm before they are loaded onto a truck. The truck must be sealed before it leaves for the abattoir. This applies for the first six months after day zero on the farm. From six months after day zero, with movement permits still in place, animals may be slaughtered at any other abattoir.
Milk precautions
The FMD-virus multiplies in the udder and is excreted in extremely high numbers in milk. This milk may only be given to calves or pigs if boiled or pasteurised to kill the virus. Raw infected milk must not be given to calves because large proportions of them will die of a heart condition. Pigs are not highly susceptible to the virus but are known to be multipliers and therefore a major source of infection on farms.
This leads to the next problem: a large proportion of cows will develop severe mastitis within the first four to six weeks after the outbreak, drastically reducing the quality of their milk and in some instances rendering it unusable. The norm is to split the herd in two with the FMD-infected milk of the cows with mastitis going into one tank, and the good milk into another.
The mastitis cows’ milk must be disposed of. The effect and risks of dumping it in slurry dams and spraying it with water onto fields, is still not known. Some surveys and experiments are underway to determine the risk, but it will take a while before there are clear answers. Currently, the best alternative is to dig a large pit as far away from surface or underground water as possible, dump the infected milk in it, ideally acidify it, and cover the pit properly to prevent other animals from drinking from it. In terms of milk quality, things will slowly return to normal about three months after the first cow presented with FMD symptoms.
The same milk processing rules apply to all farms under quarantine, whether the animals are infected or uninfected, but vaccinated. This means all the milk must be double pasteurised for the local market or processed into UHT long-life milk which can be exported. The problem with both treatments is that it is not fit for cheese-making. Therefore, if a producer only supplies milk to a cheese processor, the milk cannot be used, requiring the producer to find another processor who can double pasteurise or produce UHT milk. This in itself can be problematic and has transport cost implications if these processing plants are far away.
Another practical limitation of double pasteurisation is the need for two tanks: one to pasteurise the milk and one to cool the milk down, after which the process must be repeated. Many milk processors don’t have the facilities to do this, and acquiring new tanks is not always a viable option. The country has a limited number of processors who produce UHT milk and are most likely not close by.
In addition, if a milk processor collects milk from a quarantined farm – in some cases within 10km from another farm under quarantine – they will lose their export licence until they can prove that the infected milk will be kept completely separate from the uninfected milk at their facility. They will first have to pasteurise all the uninfected milk from the farms that are not under quarantine and then process the infected or quarantined milk. Following this, the entire plant must be cleaned and disinfected before uninfected milk may be processed again.
Quarantine lifting measures
To lift quarantine, the state veterinarian will perform two inspections once 12 months have passed after day zero. If no new FMD-cases were detected, the veterinarian will take blood samples from animals that were born at least two months after day zero, weaned, and are at least six months old. The reason is that the cows’ FMD antibodies are excreted in the colostrum and antibodies from the cow are transferred to the calf via the colostrum. Hence, a calf that was drinking from a cow with antibodies in her milk, will have those antibodies. It takes approximately six months for these antibodies to disappear from the calf’s system, which is why calves born two months after day zero must be weaned and at least six months old so that there are no FMD antibodies in their system.
If the tests are negative, the state veterinarian will report the farm as clear so that the quarantine can be lifted. Unfortunately, this takes time as the state veterinarians are inundated with various tasks. After this point, all new animals must be quarantined for at least 28 days. – Carin Venter, Plaas Media
For more information, send an email to Dr Mark Chimes at mark@milksa.co.za or mark@dairystandard.co.za or phone 074 510 7316. For more information on the DSA’s services and webinars, phone 012 665 4250 or send an email to jacqueline@dairystandard.co.za
