Vet on call: Why you can’t beat foot and mouth disease alone

I have received numerous calls since I penned the article on foot and mouth disease (FMD) oil-based vaccine last week.

Farmers have called seeking to know why the President can launch such a potentially good product that would greatly improve the economy of the nation, reduce the suffering of farmers and their animals and then the wide-scale use of it is sabotaged by the same people who are supposed to help the country achieve enhanced agricultural production.

I have no direct answer to this question but I know that by the time the President launches a product or project of national importance, a lot of groundwork has been carried out to justify the benefit and viability of the intervention.

Another group of enquiries sought to establish whether it is possible for a farmer to keep her farm FMD-free if others are not vaccinating.

My answer is, “Yes it is possible” but it works best when the majority of farmers in one area diligently vaccinate their animals at the same time.

When we started our practice in Nairobi’s Garden Estate in 1992, FMD and other diseases were the order of the day. Some farms even got the disease twice in a year.

We educated farmers on the need of a well-structured vaccination programme and almost all agreed to participate fully.

By 1997, we almost had no FMD outbreaks in the area. The few cases we saw were on farms where the owners had either dropped off the vaccination programme or they had not participated from the start. Other diseases like anthrax and lumpy skin also became non-existent.

Regarding an individual vaccinating farmer in an area where others do not diligently vaccinate, the farm may be protected especially if the viral load is not extremely high in the area.

We have vaccinated diligently twice per year for FMD on a farm in Kandara since 1997. The farm normally has a constant population of 40 to 60 cattle, sheep and goats.

We have never had an FMD outbreak on the farm even when the neighbours get the disease. There is clear evidence that the virus does visit the farm and even attempts to infect the animals but no clinical disease has occurred.

HEAL UNEVENTFULLY

Last year we delayed to carry out the vaccination by two months due to issues beyond our control. I was getting really concerned with the delay because from experience, I know the virus is always in circulation. I noticed the footprints of an FMD incursion when I was finally vaccinating the animals.

Five cattle out of 25 had minute button-like scabs on the gums. They were grey and peeling off. This was a clear demonstration that the animals had FMD but had been able to neutralise the virus and heal uneventfully. None of the workers on the farm had seen any sign of illness.

I returned to my office very apprehensive that some of the animals could come down with clinical FMD within the next two weeks, the estimated period the animals take to produce significant protective immunity. I was really relieved when a month later, no case occurred on the farm.

You see, when cattle are properly vaccinated against FMD, they develop immunity that is protective for four to six months when the water-based vaccine is used and up to 12 months when the oil-based one is used. Currently we use the water-based vaccine.

The immunity starts going down significantly four months after vaccination. Whether an animal gets infected and shows disease after the fourth month depends on the amount of virus it is infected with.

Medically, we call this the viral load challenge. If the infection is very heavy and sudden, it may exhaust the body’s remaining immunity and cause the clinical disease.

When a large number of farmers have vaccinated their cattle in one area, then the virus will have fewer animals that it can infect and multiply to infect those with a declining immune status.

Scientifically, the cattle population in an area is well-protected if approximately 80 per cent of all the cattle has been properly vaccinated.

Therefore, I advise farmers to ensure that vaccination for FMD is a community affair rather than one or a few farmers’ exercise.

The last group of farmers wanted to know why the government cannot eradicate the disease like it did with rinderpest.

CATTLE THAT ARE INCUBATING THE DISEASE

Ngechu from Kiambu lamented that his father had lost 12 out of his 40 valuable pure Friesian cows last month. Some of the survivors still looked weak.

Last week, his mother’s goats and cattle on another farm were infected. He wondered why the government vets only started vaccinating when there was an outbreak.

Vaccination during an outbreak is a double-edged sword. First, the animals in an outbreak area may look healthy but be infected and incubate the disease. Such animals will still go down with the clinical disease even if they get vaccinated.

Further, mass vaccinators in an outbreak area often serve as disease transmitters. They pick the virus from contact with infected materials and animals and transmit to clean animals when they go to vaccinate.

Also, the equipment used for vaccination such as the needles and syringes may directly infect the animals if proper cleaning and disinfection is not followed.

Nonetheless, vaccination in an outbreak is a proven emergency FMD control. Animals are vaccinated in a protocol called ring vaccination.

The veterinary service providers identify the outbreak area and vaccinate only healthy herds within a prescribed distance around and away from the outbreak farm.

All the animals inside of the marked infection circle are left unvaccinated whether they are showing disease or looking healthy.

The idea is to try and avoid vaccinating cattle that are incubating the disease. The outbreak, therefore, affects many of the vulnerable animals inside the circle and then dies out when it reaches the vaccinated animals in the vaccination perimeter.

I can authoritatively confirm to all the farmers that it is possible to make Kenya FMD-free by diligently vaccinating against the disease in cattle, sheep, goats and pigs.

The government, private veterinary service providers and the farmers must, however, design and implement a strictly coordinated national FMD control programme.