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Vet on call: Befitting new year gift to pig farms

Saturday January 18 2020

Susan Thuo feeds a boar in her farm in Elburgon.

Susan Thuo feeds a boar in her farm in Elburgon. In many cases of viral infections in pigs, they do not kill the animals as the body produces antibodies. PHOTO | JOHN NJOROGE | NATION MEDIA GROUP 

DR JOSEPH MUGACHIA
By DR JOSEPH MUGACHIA
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I closed 2019 with unfinished business at Kariuki’s farm in Kiambu. By last week, we had not known the direction the unidentified disease would take.

However, signs of abating towards the end of the year were evident when my colleague Juliet and I joined Dr Lydiah of the county veterinary office to follow up on the case.

The pigs had responded well to my antibiotics combination therapy. No new cases had arisen and more than 10 sows had given birth to bouncing piglets.

We visited the farm on December 19 and agreed that Kiambu officials would follow up on the matter with the National Director of Veterinary Services (DVS).

I would keep searching for a suitable diagnostic kit for the disease since the tests were not available locally. The aim was to shorten the period it would take to arrive at a definitive diagnosis.

Dr Lydiah reminded me that even if we tested the disease and confirmed our suspicion, we could only implement the control measures after the DVS announced the results. Protocol demands that notifiable outbreaks be announced by the county DVS.

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By last week, I had obtained a test kit used to screen for the disease. The test was appropriate since the pigs were in the recovery phase.

We suspected the disease was caused by a virus that suppresses the immune system and causes heavy growth of opportunistic bacteria.

In many cases, viral infections do not kill but the body produces antibodies. Antibiotics are only used to help prevent bacterial infections.

Once cleared from the body, most viruses leave the antibody-producing cells with a memory to produce antibodies whenever the virus or its components are detected. The antibodies neutralise the virus. This is the basis of vaccination as a disease prevention strategy.

The cleared virus leaves a quantity of antibodies circulating in the blood. These form the body’s initial protection to infection before the cells produce more antibodies.

The antibodies are used in screening tests to find out if the animal has previously been exposed to a virus of interest

In our suspected case, the antibodies can be detected up to six months from the time of infection. We were therefore within the valid testing period. The test uses a plate with wells coated with the virus components.

RESPONDING WELL TO TREATMENT

Three drops of serum from the test animals are put in the wells and the antibodies in the serum react with the virus components, giving a coloured line visible to the naked eye.

It is called a screening test because it does not determine the level of protection or if there are viruses in the body.

It only indicates that the test animal had been exposed to the virus at least within the previous six months and therefore the herd is exposed to the disease.

Positive results justify execution of full disease investigation and search for the virus in the herd and others. Last Saturday, Dr Juliet and I visited Kariuki’s farm to collect blood samples from the recovering pigs.

Incidentally, there is an outbreak foot and mouth disease (FMD) in the area. We, therefore, also delivered FMD vaccine to the farm.

Zack, one of the paravets on the farm, restrained the pigs and we collected 3ml of blood from the five recovering animals. We noted that the pigs were still responding well to treatment and had gained a lot of weight. No new cases had developed.

Back in our lab, Dr Juliet extracted serum from the blood and tested it for the virus. We were excited to see the tests mature into negative results within the stipulated 10 minutes of dropping the serum into the wells.

Kariuki and his staff were happy when I relayed the results to them by phone. “My prayers have been answered,” he said. It was a befitting New Year gift for the farm.

I told Kariuki that it was most likely a heavy mixed bacterial infection caused by the lapse in hygiene resulting from the common waste drainage channel running through the pens. He committed to move the channel to the outside of the pens.

Things have moved fast on this case. I got a call from Dr Kahariri of the DVS office last Monday. He was already on Kariuki’s farm to investigate the outbreak and collect samples. I explained to him our findings and that I would forward the report through the Kiambu County DVS.

We agreed that there was no need to take more samples to avoid stressing the animals since they had also just been vaccinated against FMD. He, however, would come to my office for full briefing.

We agreed the case was closed but should there be a similar syndrome, I would submit a whole carcass to the National Veterinary Laboratories for exhaustive pathogen investigation. This entails testing for and isolating the main organisms contributing to the syndrome.

The disease I suspected in this outbreak is called porcine reproductive and respiratory syndrome (PRRS) or blue ear disease of pigs.