How clayen fridge will allow better rabies vaccine storage

Wednesday May 22 2019

Veterinarians

Veterinarians carry vaccines in coolers in an exercise to vaccinate livestock against rabies, lumpy skin and anthrax. PHOTO | JOSEPH KANYI | NMG 

VERAH OKEYO
By VERAH OKEYO
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In the 1990s, rabies—a viral disease that is incurable once the symptoms set it—nearly wiped out the tiny population of African wild dogs living in the Tanzanian side of the Serengeti National Park. It also killed many people.

It was believed the wild dogs infected the people around the park until studies revealed that it was man’s best friend, the domestic dog, that was responsible for the transmissions.

This cycle of events—disease emerges, deaths, scientists painstakingly try to figure out what is going on and then a possible solution being arrived at—is not uncommon in public health.

However, the outbreaks in the Serengeti made Tanzania a country from which Kenya and Uganda learnt how to handle even dog-transmitted rabies.

Dr Felix Lankester, director of Rabies Free Tanzania, a programme co-ordinated by Washington State University’s Paul G.

Allen School for Global Animal Health, says there is a revolutionary way to store the rabies vaccine to keep it working under the hot temperatures prevalent around the Serengeti.

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The government of Tanzania in collaboration with Washington State University, is about to roll out a decentralised delivery strategy that will use livestock field officers to deliver vaccines to villages and a “refrigerator” called Zeepot made from clay.

Rabies, which is transmitted by bites from an infected dog, is a huge public health concern in Africa and only quick attention and vaccination can save a life.

Dr Lankester estimated that rabies kills 59,000 people annually and over 99 per cent of these cases caused by bites by rabid domestic dogs.

You do not want to wish Rabies even on your worst enemy, not only because it is incurable once the symptoms set in but also due to the agonising and painful way that it kills.

Once bitten, the virus from the saliva of the rabid dog travels to the nerves, spinal cord and then the brain from where it multiplies and spreads everywhere, including the salivary glands.

Cycle of infection

The nervous system is affected, which sometimes results in the patient being unable to swallow, which leads to the fabled hydrophobia suffered by rabies victims. Slowly, disorientation and confusion set in, followed by convulsions.

Then the patient lapses into a coma and dies. These symptoms are similar to those caused by cerebral malaria and other conditions that affect the brain, causing rabies to often be misdiagnosed – it is even frequently thought the victims are affected by witchcraft!

Yet with so horrible a reputation, most veterinarians consider rabies an interesting disease: Rabies is actually relatively straight forward to eliminate — through the mass vaccination of domestic dogs. This is the cheapest way as it can cost less than a dollar to vaccinate one dog.

During the mass vaccinations following the outbreaks in African wild dog population in the 1990s, Dr Lankester said, scientists discovered that if they vaccinated 70 per cent of the dog population each year, they would break the cycle of infection for the virus from one dog to another, and eventually to people.

Vaccination

The other way to control human rabies is to vaccinate every person that is bitten, but this is expensive, ranging from $150 to $280 for a complete course of four doses. No public health system in East Africa is able to afford that.

Dr Lankester and his team have worked to find a solution.

Since time immemorial, the vaccines, which remain potent between 2 and 8 degrees Celsius, were stored at the district veterinary headquarters and brought down to the community by vehicle.

Unfortunately, as in most villages, there are power challenges to sustaining the cold chain and so the vaccines could not be stored among communities due to the twin problems of electricity and centralisation.
They sought a way to have the vaccines decentralised so that vaccines are delivered in batches to communities to be stored, utilised and managed therein at temperatures above 2 to 8 C above room temperature.

The clay “refrigerator” called Zeepot made economic and practical sense because the “low tech cooling devices” from clay, sawdust and sand can keep the temperatures below 25 degrees Celsius on the inside even when the outside was baking at over 37.

Remarkably, the vaccines remain as potent as cold-chain stored vaccine despite being stored at temperatures up to 25°C for three months.

Tanzanian livestock field officers were coached on how to manage the vaccines. They were the perfect ambassadors because they also have in-depth knowledge of communities within their jurisdictions. It is a win-win situation.