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Vet on call: Truth about mad cow disease

Saturday April 6 2019

Franklin Mutembei attends to one of the dairy cattle that he keeps in his farm in Meru.

Franklin Mutembei attends to one of the dairy cattle that he keeps in his farm in Meru. Research has shown that the signs of mad cow disease seen in both humans and cattle are due to destruction of brain tissue by the prions. PHOTO | CAROLINE WAMBUI | NMG  

DR JOSEPH MUGACHIA
By DR JOSEPH MUGACHIA
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I was at a social function last Sunday when one of the participants asked me how Kenya had eradicated mad cow disease, otherwise called bovine spongiform encephalopathy (BSE).

I promptly responded that Kenya has never had a reported or suspected case of BSE.

“You definitely didn’t read today’s Sunday Nation,” the inquirer jogged my mind. I told him the statement in the newspaper had been made by an official who did not understand the past and current status of animal diseases in the country and who was also overstepping his mandate.

The newspaper had quoted a statement from the Ministry of Foreign Affairs saying, “Kenyan meat and meat products have been locked out of the Ugandan market for 17 years since the serious mad cow epidemic ravaged our land.”

When I read the article, I was astonished at how a senior official from one ministry can make such an unfounded and damaging statement oblivious of the fact that he was encroaching on the mandate of another official in the Livestock ministry responsible for animal disease control and meat safety.

He was also ignorant of the fact that such a statement could mean that Kenya had been lying to the world that it was free of BSE.

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Such utterances only serve to tarnish the country as they are never taken lightly by other countries. You see, governments are known to sometimes hold deep secrets even against other governments. Many times the secrets leak out from blunders made by those holding the secrets.

Fortunately for Kenya, there is nothing secret about BSE occurrence. To buttress my authority on the matter, I searched for information on the internet and among veterinary colleagues on the present and past status of the disease in Kenya.

SUSPECTED THE COUNTRY COULD BE AT RISK

We have not had the disease. The closest I could come to linking Kenya with BSE is a risk assessment done by the European Commission on BSE in 2001. They found that the disease was unlikely in Kenya but not fully excluded.

They concluded so because Kenya had imported meat and bone meal between 1987 and 1990 from the United Kingdom and also from Belgium, Denmark and the Netherlands since 1994.

The data made available to the risk assessors did not clearly show where all the imported meat and bone meal was used.

This meant that some of it could have reached Kenyan cattle through manufactured animal feeds. On the other hand, there was no certainty that the meat and bone meal was infected with BSE and that it had actually been used in cattle animal feeds in the country.

I confirmed with Dr Michael Cheruiyot, a senior deputy director of veterinary services that Uganda in fact banned beef and beef products importation from Kenya in 1996.

Like the Europeans, they suspected the country could be at risk of BSE outbreak due to the imports of bone and bone meal from Europe.

Europe, especially the United Kingdom, was the region most affected by the BSE outbreak of the 1990s. To underscore the seriousness of BSE, the UK implemented an eradication programme and destroyed about four million cattle.

They also developed a policy where all slaughter cattle older than 30 months had to be tested for BSE. Another action was the ban on the use of animal tissues in the manufacture of feeds for cattle, sheep and goats.

With this drastic and rigorous action, they were able to put the disease under very strict control. Only occasional cases of the disease are seen since the end of the eradication programme.

In my article last week, I expounded on why livestock farming requires very stringent regulation. The UK case with BSE demonstrates the efficacy of such regulation and the impact on food safety and trade at the national and global level.

NOT VISIBLE UNDER THE MICROSCOPE

Good regulation and enforcement in livestock farming is also a tool of economic empowerment because farmers are able to grow their animals to maturity and fetch good prices on the market.

So why is BSE such a big deal? It is one of the rare but very deadly diseases transmitted from cattle to humans. The disease takes long to develop in both species but once the signs appear, death is inevitable.

BSE is caused by an infective protein called a prion. Prions are not visible under the microscope and their diagnosis is done through complex methods and microscopic examination of brain tissue after death.

They cause such diseases as BSE in cattle, scrapie in sheep and Creutzfeldt-Jacob disease (CJD) in humans. Prions resist destruction even when the affected meat is cooked or heat-treated.

When BSE is transmitted to humans, it causes a disease similar to CJD and is called variant Creutzfeldt-Jacob disease (vCJD).

BSE developed and spread widely in the UK due to the liberal use of ruminant tissues such as intestines, blood and bone in manufacturing the feeds for young calves and dairy cattle. It was a cheaper source of protein than soya bean.

People got infected with BSE when they consumed beef products from cattle infected with the disease. CJD, on the other hand, is a prion disease that spontaneously occurs in humans.

Despite the many biomedical studies that have been carried out globally on prions, there is still a lot that is not understood about how the infective agents come about and how they cause disease.

Research done in Kenya and published in 2005 showed the disease existed in the country but had no relationship with BSE or vCJD.

Both human and cattle patients of BSE show progressively deteriorating nervous disease leading to death within days to months.

DESTRUCTION OF BRAIN TISSUES

Infected cattle do not show signs of illness immediately due to the disease’s extremely long incubation period ranging from 2.5 to 8 years.

Signs of BSE often start with abnormal gait, changes in behaviour such as anxiety and aggression, tremors and hyper-responsiveness to otherwise normal situations.

Some animals may show nervousness and frenzy. Persistent pacing, rubbing and licking have also been observed. Non-specific signs including weight loss, reduced milk yield, lameness, ear infections and teeth grinding have been seen too.

The disease worsens over a period of days to months until the animal is unable to stand, becomes unconscious and dies.

Any farmer or animal health service provider observing these signs in cattle they are attending to should report to the animal health and administration authorities.

Research has shown that the signs of the disease seen in both humans and cattle are due to destruction of brain tissue by the prions.

Once the infection reaches a critical stage to show disease signs, brain cells die off in large numbers. Physical and mental abilities degenerate, and ultimately the patients die because the brain is no longer able to control body function.

When examined under the microscope, the brain appears to have holes.