Vaccinate against this disease and maintain hygiene to forestall losses
Roy Mugo the owner and manager of Yehuda farms in Embu, checks on one of his birds. FILE PHOTO | NATION MEDIA GROUP
What you need to know:
- Infectious coryza barely kills the birds and if any deaths, mortality would range between five to 20 per cent.
- While infectious coryza, is often seen as a simple mild upper respiratory disease, it can be a more complicated disease due to secondary infections resulting in severe diseases and significant economic losses.
- Vaccines can be obtained from agro-vets and should be carried out when birds are between the ages of five and six weeks.
- The preventive method also helps farmers to save on money they would have spent on antibiotics.
Last week, I got a call from one of our project farmers, Peter. “The nuisance disease is back again and it’s really affecting my chickens,” he said, sounding very distressed.
I didn’t quite make sense out of his statement.
He further explained, “Some kukus have swollen faces with foul-smelling, thick and sticky discharge from the nostrils and eyes combined with laboured breathing. Others have gotten to the point of completely closing their eyes, and when I open the eyes there is a gel-like substance on the surface of the eye ball. Two years into the business, I have experienced the disease four times and it is heavily affecting production and my profits. Last year, I sought advice from an agro-vet who suggested I use antibiotics in their drinking water and then squeeze out the gel substance from the eye and apply eye ointment (oxy-tetracycline), but this doesn’t seem to have worked.”
Based on Peter’s description the quickest diagnosis I would make out of the symptoms is that his flock is suffering from infectious coryza.
Let me take you back a bit on why Peter refers to this disease as the ‘nuisance disease’.
Infectious coryza barely kills the birds and if any deaths, mortality would range between five to 20 per cent.
Instead, it spreads at a high rate (up to 90 -100 per cent morbidity rates) causing depression in birds and the tendency to sit quietly in a corner with their heads tucked in and eyes partly closed.
Gradually, as the infection progresses (scientifically, we call this the incubation period of the bacteria causing the disease while slowly weakening the immune system of the bird) the infected bird begins to show the symptoms Peter mentioned.
At this point feed and water consumption is usually reduced having a negative implication on performance of the birds.
Infected birds will transmit the bacteria to others by direct contact, airborne droplets or drinking water and feeds.
To help Peter, I visited his farm later in the day. On arrival, I did rounds in the poultry houses to observe the flock and management to guide on how best to advise Peter.
I also collected samples of litter material from his poultry houses for laboratory examination of the bacteria causing the disease.
Two days later I went back with results and several suggestions for the farmer.
HEALTHY CARRIERS
From the survey, Peter operates a one-stop shop for indigenous chicken meat and eggs.
The farm has four poultry houses and all are managed by one person; breeding flock house, chicks brooding house, cockerel house (reared for meat production) and egg production house.
He re-stocks the production flock from his own flock by selecting high producing and healthy males and females to maintain a breeding flock of 50 females and 10 males every year to avoid inbreeding.
Results from the laboratory indicated that the litter material we collected from all his houses had the bacteria with the breeding house and the egg producers’ house being heavily infested, which could explain why the layers in both houses (breeding and production) were the most affected.
I put across several concerns that could be making Peter’s farm susceptible. Looking at bio-security issues, there is the possibility that Peter could be using birds that appear healthy and are carriers of the disease as the breeding stock hence being the major reservoir of the bacteria since they stay longer in the farm compared to the production birds.
Also the fact that he has one person managing all the flocks from breeders, chicks to producers could also be an agent of transmission of the bacteria from one house to the other.
“I am just wondering why after religiously following the treatment plan as advised by the agro-vet and spending so much money on drugs the disease recurred again not once but twice,” Peter wondered.
My explanation for this type of situation is that although the farmer followed the treatment plan as advised by the agro-vet, the antibiotics he administered to his flock were only effective in reducing clinical signs of the disease or the severity of reactions but did not eliminate the bacteria from the birds making them carriers of the disease.
On a lighter note I told him: “Most of you guys do not take the disease seriously because of the low mortality rates. Yet you spend a lot of money on antibiotics to control the disease without noticing the effect it has on the profits.”
Peter concurred. “For as long as I can remember I have been using bio-trim (broad-spectrum antibiotic) each time these signs erupt and looking at my annual production costs managing the disease accounts for about 40 per cent.”
I advised him that the long-term use of the same drug to treat the same disease is likely to become ineffective due to pathogen strains evolving and adapting to the drug.
Peter has also incurred huge economic losses due to increased number of culls of the infected birds and a 20 – 40 per cent drop in egg production while the males meant for meat production rarely reach market weight at the point of sale.
DRUG RESIDUES
What most poultry farmers don’t understand is that infectious coryza, while often seen as a simple mild upper respiratory disease, can be more complicated disease due to secondary infections resulting in severe diseases and significant economic losses.
Birds that have recovered from the disease remain carriers of the organism and may occasionally shed the bacteria during their lifetime or productive period making it difficult to fully eradicate the disease.
To completely eradicate infectious coryza, I advised Peter to depopulate his entire flock, clean and disinfect the house and equipment they have come in contact with.
Then leave the premises uninhabited and equipment used for about two months before starting over again by obtaining birds from a reputable or well-known supplier or hatchery.
Thereafter, he should apply an all-in/all-out production policy.
The thought of depopulating his whole flock made Peter rather displeased with the suggestion, which is totally understandable looking at it from an economic perspective.
In that case I offered Peter an alternative solution, “You may retain your flock. However, isolate the birds with signs of the infection for thorough medication but products from these birds should be withdrawn from consumption due to drug residues on the products. As for the healthy birds or those that appear uninfected, provide vaccination against the infection. This should be combined with good management, rigorous sanitation, and a comprehensive biosecurity plan by having different workers for each house.”
While the focus is on vaccinating against common diseases such as new castle, gumboro, fowl pox and fowl typhoid, not so many know that infectious coryza can also be vaccinated against.
This preventive method helps farmers to save on the amount of money they would have otherwise spent on antibiotics even as production dips.
Vaccines can be obtained from agro-vets and should be carried out when birds are between the ages of five and six weeks.
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Ms Miyumo is a livestock expert at Egerton University
