Vet on call: Watch out for this ‘harmless’ pig disease

Piglets feed on their mother's milk in a farm in Meru. Pig farmers should watch out for swine pox which is caused by a virus similar to many other pox viruses that affect mammals and birds and is potentially dangerous to young animals. PHOTO | PHOEBE OKALL | NATION MEDIA GROUP

What you need to know:

  • Swine pox disease is spread by flies, mosquitoes, lice, mites, pig-to-pig contact and human-to-pig contact.
  • Swine pox is caused by a virus similar to many other pox viruses that affect mammals and birds.
  • The disease is mainly mild in pigs but may cause deaths in young animals, especially those that are born already infected with the virus.
  • Each pen should have its own entrance and exit. Workers should have easily washable protective clothing such as coveralls and gumboots.

Daisy, a farm manager from Ruiru called me the other day early morning and the first thing I picked from her voice was that she was deeply distressed.

“Our pigs appear to be in big trouble. Please check the photos on your WhatsApp,” she said after a greeting, though I told her to directly tell me what the problem was.

She reminded me that I had once discussed in this column about African swine fever which turns pigs red and then purple before dying.

She wondered if that could be the problem with her pigs. “Please don’t jump into conclusions. Kindly tell me what you are seeing on the pigs,” I guided her.

Daisy supplied the disease history in her pigs, noting about 15 animals in five pens had turned red on the ears, underside, inside parts of the legs and on the back.

They looked like they had sun burn yet they were in a roofed shelter. Some of the pigs appeared to have red pimples. The disease had started with two pigs about three days earlier but she had thought the animals had scratched themselves.

While the disease was spreading fast, the pigs were eating well, and the body temperature was within the normal range of 38-40 degrees Centigrade.

Daisy manages 600 pigs on the farm. She is meticulous with operations and loves her pigs. And her work is superb as since she was engaged three year ago, disease level had reduced drastically and quality of the pigs had greatly increased with the owner being happy with his swine investment.

From her description, it was obvious she did not have an emergency but I still could not make a diagnosis and prescribe treatment remotely even with the photos she had sent.

On the way to the farm, I mentally made my differential diagnosis of the problem. This is the list of the most likely diseases that could cause the signs Daisy had described.

The list included parasites such as mites, sunburn, allergic reactions and swine pox. A differential diagnosis, medically, abbreviated as DDx, is a routine that is second nature to a doctor. It is a valuable tool for diagnosing diseases and makes doctors behave in a predictable manner in disease diagnosis.

THE SUBTLE NUISANCE

Once on the farm, I examined the pigs and the situation matched Daisy’s narration. However, I noticed some of the red pimples were drying in the centre and beginning to change colour to black.

Some of the pimples in the two pigs that first showed the disease had dried up and formed black scabs.

The additional signs provided me with an undisputable diagnosis. “This is swine pox,” I informed Daisy, her face brightening.

“The bad news, however, is that it will take three to four weeks for each affected pig to recover. That will delay selling your animal,” I added.

Swine pox is caused by a virus similar to many other pox viruses that affect mammals and birds. The disease is mainly mild in pigs but may cause deaths in young animals, especially those that are born already infected with the virus. Swinepox may sometimes occur and pass unnoticed in pig herds with lax disease detection.

The disease starts suddenly as Daisy had noticed and quickly spreads through the herd if effective measures are not taken to contain the infection.

Infected pigs will mostly have normal appetite and normal temperature except if the pimples are infected by bacteria.

Swine pox has no specific treatment and the body develops immunity and self-cures in three to four weeks. A pig that recovers from the disease develops lifelong immunity.

The disease is spread by flies, mosquitoes, lice, mites, pig-to-pig contact and human-to-pig contact. Workers cleaning the pig pens can easily spread it in the whole piggery.

I normally call the infection “the subtle nuisance” because it causes losses to the farmer indirectly through delayed sale of slaughter ready pigs and reduced weight gains in some infected pigs.

The disease may also cause losses by raising the mortality of piglets that are born already infected.

It is controlled by maintaining high levels of hygiene on the farm and a good pigsty construction.

The pests that transmit the disease should be kept under strict control through proper waste disposal for the flies, elimination of stagnant water to control mosquitoes and spraying the pigs with suitable pesticides to curb lice and mites.

SPRAYED ONCE PER WEEK

The pigsty should be constructed with easily washable material such as plastered concrete.

Each pen should have its own entrance and exit. Workers should have easily washable protective clothing such as coveralls and gumboots.

They should further avoid contact with pigs as they work within the pens and wash their hands and gumboots once they finish attending to the animals in one, before proceeding to the next.

The swine pox virus lives in the environment and is persistent. Once the disease is established in the first pig, which we scientifically call the “index case”, it becomes available for transmission by all the other vectors as well as pig-to-pig and pig-to-human contact.

On Daisy’s farm, I informed her transmitters (vectors), were flies, mosquitoes and the workers.

I further realised Daisy had extended the pig housing with two large additional units each with six pens holding 15 pigs. There was a series of five doors connecting all the six pens apparently to increase the efficiency of cleaning.

Unfortunately, this reduced hygiene and increased the ease of disease transmission among the pigs.

The drainage trench from the additional pens had a low gradient and the water and other waste tended to stagnate providing a good environment for breeding of flies and mosquitoes.

I advised Daisy to provide each pig pen with its own door and seal all the connecting doors, increase the gradient of water and waste flow into the disposal pit and spray the drains to control flies and mosquitoes.

The pigs would be sprayed once a week with a suitable pesticide such as pyrethroid to control flies, mosquitoes, lice and mites.

***

Swine fever

  • African Swine Fever is the most deadly pig disease.
  • The viral disease is highly contagious and affects domesticated and wild pigs and warthogs
  • It has no treatment and can wipe out an entire pig farm.
  • No vaccines have been found but several bio-security measures can be observed to minimise its spread.
  • Watch out for biting flies, ticks, and limit the number of vehicles and people visiting the farm.

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