When human beings observe disease events in animals, the immediate response is to quickly scan their memory bank for a comparative occurrence in people.
This is perfectly normal because we are wired to think from the known to the unknown. Unfortunately, most animal disease events are very different from human occurrences.
That brings me to a report I received in February. “Hello Doctor, my layers are having heart attacks. They shiver, try to sit like penguins and drop dead,” Stanley told me on phone.
He also reported his well-fed Isa Brown layers had dropped egg production from 89 to 60 per cent in two weeks.
Upon arriving on the farm in Ruiru, I noted the chicken buildings were well done with stone and iron sheets. They had nice setting for ventilation, lighting and natural heating.
The sides of the buildings were made of metal bars and two layers of mesh wire of different gauges. That made the houses vermin proof.
The farm was fenced off with a high stone wall. There was a deep disinfectant bath at both the entry and exit gates.
The setup was impressive. Inside the houses, the chickens were in clean steel cages.
As I put on my protective clothing, Kariuki, Stanley’s farm manager, came over and started his briefs. “We have 6,000 layers and have lost five mysteriously over the last three days. They appear to get heart attacks and die.”
It is interesting that most farmers tend to give the doctor a diagnosis instead of explaining what they have seen and letting the doctor make his observation by combining the history of the case and examination findings.
Kariuki explained that the chicken looked normal, though there were some with unusual standing positions tending to let their bottoms drop close to the cage floor and pushing their chests up and backwards.
That is what Stanley had correctly referred to as the “penguin standing position”. Some chickens would then suddenly drop dead.
HOT ENLARGED ABDOMENS
The chickens were in three lots and the problem had occurred in the lot in its peak laying. I quickly observed all the birds in the cages and noticed three which fitted the description Kariuki had given.
I selected them for detailed examination and found they had hot enlarged abdomens.
I usually do not take the temperature of chickens because their normal body temperature, at 42 degrees centigrade, is already at the top of the thermometer scale.
An experienced doctor is, however, able to feel a higher than normal temperature.
I proceeded to carry out post-mortem examination on two chickens, which had died in the night. On opening the abdomen, I found a lot of egg yolk in the abdominal cavity, otherwise called the peritoneal cavity.
There was a lot of inflammation and a putrid smell coming from decomposing tissues. There was also pus in many of the tissues around the eggs.
The ovaries and oviduct, also known as the egg tube, were much reddened.
“Your chickens are laying into themselves. These two are carrying several eggs which should have been on the breakfast table days ago,” I told Kariuki as I pointed at two of the dead birds which had many egg yolks laid in their abdomens.
This phenomenon in chickens and other birds is called internal or blind-laying. The life-threatening anomaly occurs because the oviduct is an open tube with a funnel like internal opening that, under normal circumstances, captures the mature egg yolk as it is released from the ovary and prevents it from falling into the abdominal cavity.
Through a series of contractions towards the external world, the ovary slowly, over a 24 hour period, pushes the forming egg towards the vent for the normal laying.
During the journey, the egg acquires the egg white, the shell membranes and finally the shell.
In some cases, as with Stanley’s layers, the oviduct is unable to capture the egg yolk and the yolk falls into the belly. If this happens accidentally, the chicken can absorb the yolk over time with no severe consequences.
INFLAMMATION OF ABDOMINAL TISSUES
Unfortunately in most cases, the bird piles the yolk in the abdominal cavity faster than it can absorb it.
The accumulation of yolk results in severe inflammation of abdominal tissues and often movement of bacteria from the oviduct into the peritoneal cavity.
Egg yolk being a good bacterial food, infection sets in and toxins are produced from the decomposing yolk and tissues. It is the bacterial activity and tissue inflammation that make the bellies of internal layers feel hot to touch.
Sudden death usually occur due to massive absorption of toxins in the body.
Layers that are overweight are known to be vulnerable to internal laying. Other causative factors are infection of the oviduct by bacteria or viruses and exhaustion of the oviduct as chickens complete their laying cycle.
“So doctor, what is the cause of the problem?” Kariuki asked. From my observation, the most likely culprit was bacterial infection.
I checked into the clean chicken house, wondering why the problem was only in one lot of birds. I identified the suspect.
The water cisterns of the automatic drinking system were partially open and they had greenish brown slurry at the bottom.
The chickens were definitely drinking a micro-organism soup throughout.
Kariuki agreed to clean and disinfect all the cisterns and the drinking system. I prescribed a broad spectrum drug, vitamins and minerals to be given to the birds in drinking water for three days.
Two weeks later, I got a report the birds were recovering well and the laying curve was up at 76 per cent.