Peter keeps pigs in Ruiru, on the outskirts of Nairobi, and always he feeds them on commercial foods.
Having done pig farming for about five years, he has mastered the science and art of growing the swine from birth to finishing for the slaughter market.
Peter even sometimes calls me to report a sick pig and goes ahead to suggest what could be wrong with the animal.
I was, therefore, concerned when about a month ago, Peter called me and reported he had a case of weak pigs, some looked confused and others appeared to have difficulties in standing. Some of the animals had diarrhoea.
“And what is the temperature of the sick pigs?” I asked Peter as he always has the temperature of ailing pigs when he reports. It ranged between 38.8 and 39.5 degrees Centigrade.
That was within the normal range of 38.8 to 40 degrees Centigrade.
I arrived at Peter’s farm in 40 minutes and found eight sick pigs in two adjacent pens. The signs of illness were just as he had described.
While diarrhoea was present, it was mild and was unlikely to be the cause of the general weakness and difficulties in standing for some of the pigs.
One clear pattern was that the young pigs weighing about 20kg were the most affected.
Peter’s farm worker, in-charge of the pigs, informed me the animals had started showing the signs the previous evening.
I examined all the sick pigs and their temperature agreed with Peter’s report. Some of the pigs had slightly elevated breathing rate but everything else looked normal.
Some pigs showed weakness of the legs but did not have diarrhoea.
I ran through my mental disease checklist and returned a blank.
CHANGE IN FEEDING
I told him I needed full history of the pigs for the last one month because the disease appeared unusual. I wanted to know what the animals had been fed on and whether there was any change in feeding.
I also wanted to know whether there was a change in the drinking water supply.
Peter said about three weeks earlier, a friend had visited the farm and noticed the leafy greenish red plants growing abundantly at the pig manure dump pit.
He said he used to rear pigs and they really liked to eat the plant. He picked some of the plants and fed the pigs in the two pens. The pigs happily ate the plants.
“That is the only change that I know has occurred with these pigs in the last one month,” Peter concluded. He said he did not object to his friend’s action because the pigs seemed to like the plant and the plant had been collected from his farm.
I prompted George, the worker, to add onto the testimony his boss had given. “We have continued giving the pigs in these two pens those leaves because they appeared to like them but stopped about five days ago when the plants got finished,” he volunteered.
I visited the manure dump pit and confirmed the presence of cut stumps of the Amaranthus reflexus plant. There were also many small plants with only a few leaves growing in the area.
The place also buzzed with numerous flies of different colours ranging from blue to green and the normal housefly.
The pit was a perfect breeding ground for the flies. The insects were patching on every available surface of the plants around the pit.
POISONS THE KIDNEY
The dump pit was definitely another change on Peter’s pig farm. Previously, the pit used to be about 100m from the pigsty.
I enquired the reason for the change and he explained that he had seen they were using a lot of water to flush the manure the long distance.
He had, therefore, decided to bring the pit closer to the pigs to save some water.
These set of findings provided the solution to the pig disease puzzle. I turned to face the farmer and informed him, “Peter, your pigs are suffering from amaranthus reflexus plant poisoning and bacterial infection of the intestines.”
I treated the pigs with antibiotics for the diarrhoea. Further, I prescribed multivitamins and a lot of water to be given to the pigs for three days.
I advised Peter never to give the Amaranthus plant to pigs again and to only feed them commercial feeds as he had been doing before. He would also use chemicals to control fly breeding at the manure dumping pit.
Amaranthus plant species are also referred to as the pig weed. They grow well in fertile soils especially around animal houses or manure damping sites.
The type that poisoned Peter’s pigs is called red root pig weed and they like eating it. Unfortunately, it contains nitrates and an unidentified toxin that poisons the kidney.
The kidney toxin causes swellings and accumulation of water in the tissues surrounding the kidney. It also causes death of kidney tissue, accumulation of fluid in the chest and heart failure in pigs, and other livestock like cows, goats and sheep, with the animals exhibiting similar symptoms.
It takes a minimum of eight days for the signs of poisoning to show. The signs include poor appetite, increased breathing rate, normal temperature, weakness and inability to stand.
Pigs that are reared in doors are particularly sensitive to red pig weed poisoning.
On the other hand, people eat Amaranthus as a vegetable without any problem because the toxins are deactivated by cooking. In Kenyan eateries, the vegetable is offered as “terere or dodo”.
The bacterial infection seen in Peter’s pigs was most likely caused by the consumption of the amaranthus plant contaminated with bacteria spread by the many flies observed at the manure dumping pit, since only the pigs that ate the plant had diarrhoea.
The pigs recovered.
There is no specific treatment for amaranthus poisoning in pigs, sheep, goats or cows but many affected animals recover over a period of time from mild poisoning when access to the weed is removed.
In severe cases, up to 80 percent of the animals die.