By Tony Greaves
Vets from across Canada described field problems
By Tony Greaves
Vets from across Canada described field problems and summarized research results for their peers
WestVet 16, or the sixteenth Western Meeting of Poultry Clinicians and Pathologists, was held October 4th in Lake Louise, Alberta. As in previous years, this was a day in advance of the Poultry Service Industry Workshop in nearby Banff.
The meeting is open only to veterinarians (and this closely monitored representative of Canadian Poultry Magazine). The program consists of a series of 15-minute presentations where research findings are interspersed with reports on field problems that are either undiagnosed or have only a tentative diagnosis. Suggestions from the speakers’ peers are encouraged. Since the audience comes from most provinces across Canada and from many of the “poultry states” in the U.S., many times the problems they describe have been encountered elsewhere.
Quebec veterinarian Dr. Daniel Venne used and displayed on-screen, a computer modelling program developed by Dr. Robert Charrette and himself, which he uses to explain IBD vaccination failure.
He described results from three flocks of roasters and, in graph form, showed how parental maternal antibodies declined and how the flocks responded to infection after the use of various vaccines at varying dates.
In general, Venne stated that the antibody half-life (when half of the protection has dissipated in the commercial chick) is connected to their growth rate. He said that chicks that grow faster lost their antibody titer faster. He also commented that he would welcome a one-day withdrawal time for Gumboro vaccine – as in Europe.
Dr. David Smith summarized “OPR” or other people’s research, regarding Flushing/Stunting syndrome.
He said that there had been suggestions that the inclusion of “bad” fat in feed was involved. One company had a widespread problem that disappeared over the summer months. But in 2004/2005, the problem reappeared in flocks fed by three different companies in Georgia. A similar syndrome has been reported in Alabama, North Carolina, Tennessee and Arkansas.
“Is this a new disease?” Smith asked.
He reported that flock uniformity was very poor at six to ten days with pasty vents, caked and slick litter – so bad that it was, at times, treacherous to walk on. The chicks were huddled together, they were stunted and had ruffled feathers. “They have been described as having long beak disease. Due to the disproportionate growth, the primary feathers extended well past the vent. In short the flock showed the shoe-store syndrome – all sizes available.”
Smith said average mortality was in the region of 10% and up to 40% in some cases. The cost to the industry was from $200,000 to $500,000 per week. “In some barns thousands of birds were stunted.”
Diarrhea “striped” downwards from their vents. He said that runting/stunting syndrome is not a good name for this problem as there is a specific gut lesion associated with the condition.
Gut tissue is very pale, but bone marrow was acceptable, so it was not anemia. The chicks had normal bursae and thymus, although the spleen may be smaller than expected in some birds.
There is undigested feed in a watery liquid, which can be seen through the gas-distended, translucent gut wall. The cecum was somewhat distended. Smith reported that there was cyst formation in the intestinal crypts on histopathology.
By 20 days of age the gut was back to normal, but affected birds never catch up, Smith stated. Increasing barn temperature to 100°F for 100 hours has some beneficial effect, but doesn't prevent the problem. Some have tried vitamins and even liquid aspirin – to no avail.
The condition increased days to market by two. Feed conversion was 10 points higher, there was some immunosuppression and secondary septicemia. Condemnation levels were variable.
New farms seem to be spared, but once infected, the farm seemed to have a repeat problem. Barn clean-out helps and the chicks seem OK when grown on non-infected premises. No strain of broiler show a greater problem than any other. The use of antibiotics helped against secondary infections.
“It is believed this problem is associated with the short downtime between flocks and chicks from young breeder flocks seem to be more susceptible. I don't understand it,” Smith said.
He conjectured that it may be a new wave of “Helicopter disease” and similar problems encountered by the industry since the 1970’s.
Smith said the flock managers were attempting to “manage” their way out of the problem, but are dreading what the coming winter will bring.
He added, “The current good returns in the U.S. broiler chicken industry mean that down time between flocks can be as low as three days.”
Dr. Brenda Allan’s presentation revolved around TLRs or Toll Like Receptors, which allow a host to recognize when a pathogen is present. They activate an innate immune response, recognizing “motifs” found on invading microbes.
She said that only some types of the currently recognized 14 TLRs are found in chickens: TLR 2, TLR 4, TLR 5 and TLR 7 recognize different bacterial or viral components and may play a role in resistance to these infectious agents. To date no TLR-9 has been identified in poultry. TLR 13 and 14 have been identified by researchers in Ireland, with TLR-13 “expressed” in the tongue, bursa, cecum and bone marrow tissue. TLR 14 has not been identified in other species, Allan said.
To test their action, Dr. Allan grew chicks to five weeks then orally infected them with salmonella, testing their ceca two days later and compared the results to uninfected controls.
“This is where genotyping meets the real world,” Allan said. “This will allow us to say if a specific strain of bird has an innate resistance to specific challenges.”
“It seems like far-fetched research, but,” Dr. Allan predicted, “in five or ten years time, we should be able to ask what these disease resistance profiles are like in grandparents.”
Type A Marek’s?
Dr. Rick Stanley from Vancouver Island described a case of high mortality in broilers. A broiler flock is housed in a seven year old, two storey barn, located 30 metres from the roaster barn and a slaughter facility.
Roasters are either transferred from the broiler barn or purchased and put into the barn before they are slaughtered, so it’s a multi-age facility. The high mortality in the broiler flock was believed to be caused by Type A Marek's, showing up initially in the brain, then later on the skin and in the bird's nerve structure. Vaccination for infectious bursal disease and fumigation helped somewhat, but mortality continued. Vaccination with a higher dose of Marek’s so far has appeared to prevent recurrence.
Stanley stated that he expected the problem to show up again in the Vancouver Island broiler chicken industry because it is so highly dependent on mainland-located infrastructure. As a result, growing facilities on the Island are not being upgraded.
Two vets in the audience suggested that transient paralysis and botulism should be considered as potential alternate causes.
Dr. Jane Pritchard discussed her pre-harvest surveillance of broiler flocks for enteric zoonotic pathogens this past summer. She reported that she avoided difficulty in getting access to broiler barns in the Fraser Valley by using cecal culture at the processors. Problems with fungal over-growth on cultures was overcome by adopting the new Campy-Line culture media.
A summer student collected ceca from 20 birds from each of 209 flocks submitted to two processing plants. These were pooled into two samples of 10 ceca per flock over a 12-week collection period. She found that 51% of 413 samples were positive for campylobacter. The age of the positive flocks ranged from 38.4 to 39 days of age. The flocks in question went to two processing plants, one with a high speed line, the other using low speed. She found 53% and 38% of the flocks positive respectively by plant.
The incidence graph did not give the expected bell-curve of positives as the summer progressed from June 1st to August 18th. Peaks showed up at the end of June and again mid-August, but neither ambient temperature nor rainfall was found to be a predictor.
Pritchard tested the microbes for resistance and was pleased to report that although 41% of the species showed resistance, over half, therefore, had no resistance. In addition, they all showed zero resistance to erythromycin, an antibiotic important in treatment of human Campylobacteriosis.
Dr. Pritchard concluded by saying that the darkling beetle is considered less likely as the main vector for campylobacter. Instead, it seems possible that flies are a good candidate, with the microbe entering water drainage systems from dairy farms, then being carried to the broilers by the flies.
Inclusion Body Hepatitis
Dr. Susantha Gomis of the Dept. of Veterinary Pathology at the University of Saskatchewan, summarized the situation regarding inclusion body hepatitis in that province.
He reported that it caused mortality of from 150 to 500 birds per day for four to seven days of a 25,000 bird flock and total mortality can be up to 30% in some flocks.
“Typically I find necrotic livers in which it is easy to find virus particles in the nuclei,” he said.
Gomis reported that Australian researchers had found evidence of vertical transmission in 1980 and vaccination of the broiler breeders solved the problem. “But in the Saskatchewan situation, is it a primary or secondary disease?” he asked.
He reported that he followed the progeny from 18 broiler breeder flocks from the premises of eight producers. While the IBD titers were 9,000 in the broiler breeders, titers were down to 4,000 in day-old chicks and to 2,000 at slaughter.
Dr. Gomis also reported that the weight of the bursa was highly correlated to the body weight of the broiler.
Of the 18 broiler breeder flocks, he reported that six were most often associated with isolations of inclusion body hepatitis. However, there seemed to be no correlation of infectious bursal disease (IBD) or CIA (chick anemia virus) with IBH titers in the commercial broiler chicks.
Overall, Dr. Gomis stated that the producers are managing their flocks correctly and concludes that vaccinations for IBD and CIA are effective in the breeder flocks. He ended his talk by stating that he hoped that future research would develop a live or killed vaccine against inclusion body hepatitis.
Four Or Five Times Higher
Dr. Bob Goodhope of the Dept. of Veterinary Pathology at the University of Saskatchewan, reported on the increased incidence of inclusion body hepatitis in the province. Since 2003, he reported that the incidence was four or five times higher. Onset is between nine and 23 days, duration is from four to nine days and losses range all the way up to 30%.
He said the problem seems to be a primary pathogen adenovirus and is more common in summer and fall, with September being the worst month, accounting for 60% of all outbreaks. Fifteen per cent of all Saskatchewan barns have had IBH outbreaks and 45% of the broiler farms have encountered the problem. Of all outbreaks, 60% are repeat events for that farm. In fact, Goodhope reported that two farms have had diagnoses of inclusion body hepatitis six times in two years.
“There is a big difference between the incidence of inclusion body hepatitis in the last ten years with a large increase in the last three years,” Goodhope stated.
E. coli in Alberta
Dr. Tom Inglis outlined the research he had been doing on the strains of E. coli found in Alberta poultry and the resistance to antibiotics that they carried.
He said that the strain was not found to be very indicative of its source, which ran counter to prior assumptions and caused some frustration.
Inglis described E. coli control as, “Pulling drugs out of the toolbox one by one, until one worked, But we still do not understand the interaction between the drugs and the bird.”
In broilers, the number of strains of E. coli found was limited. In addition he found that E. coli showed considerable resistance to amoxicillin, an antibiotic not frequently used in Alberta.
Inglis tested the efficacy of some antibiotics no longer used and found that the susceptibility had improved somewhat over time, unless that drug had a close relationship to another drug still being used. Enrofloxacin gave better results, but is no longer available for use with birds.
His work showed that there is a close relationship between E. coli infections and dirty broiler hatching eggs.
There is also a high correlation between highly pathogenic types of E. coli challenging poultry and those causing human health problems. He wondered what affect non-treatment of an E. coli problem in poultry flocks has on human health.
Dr. Inglis pointed out that most strains of disease organisms have been sorted by their pathogenicity. “But that's not so with E. coli,” he said.
His final comments were: “Properly cooking poultry meat would solve E. coli problems in human health, but until that goal is achieved, what are we going to do without Baytril?”
All Veggie Diet
Daniel Venne returned to the podium to discuss his findings during the use of an all vegetable diet.
In the first flock there was a slightly higher mortality during the first few days and some pasty vents were encountered. There was more water than normal found under the water lines. Venne said that in Quebec, where he practices, in some cases the levels of potassium in the feed are a bit high at 0.90 or more. But he added later in his presentation that in a trial, electrolytes or sodium bicarbonate were added to try to balance the excess potassium in all-vegetable feed. Autopsies on the dead chicks from this flock showed omphalitis and pericarditis. In addition, there were three that were dehydrated and one more without any special lesions.
He pointed out that soya is very rich in potassium, thereby increasing the intake of that chemical when the birds are fed an all vegetable diet. He pointed out that sodium, chloride and potassium are the main electrolytes that regulate the blood pH and that research and the NRC (National Research Council) recommend potassium levels of between 0.21 and 0.73.
With flock #2, 60 of the 8,000 bird flock died up to day three. No infections were seen, however, the kidneys were somewhat red, with visible urates in the kidneys and in the cloacal region. They were obviously dehydrated. The intestines were distended and were heavy with liquid.
The feed had a sodium level of 0.11 and potassium of 0.87, but with a low electrolyte balance. The water supply was softened and showed a low calcium level of 3.73. Potassium was at 265 ppm. It was discovered that a potassium salt had been used to soften the water, because the sodium level in the water had been criticized.
The end result was that the corn/soya vegetable diet was reformulated with a lower potassium level.
Venne said that the higher the protein, the more potassium shows up in the diet. “One has to get under 20% protein to keep potassium levels under 0.90%.” He added, “Over time I have found that when soya is expensive, potassium levels in the feed tends to decline. When soya decreases in price, soya levels increase followed by potassium levels.”
Venne pointed out that chickens can control blood potassium very accurately later in life by diluting their blood to keep potassium levels on target. However, he said that excess potassium can cause significant muscle damage in the first 14 days and recommended additional vitamin E to help correct any such situation. He recommended that to avoid similar problems with all vegetable diets early in life, protein levels in the first starter should be decreased and specific amino acids added to fulfil the birds' amino acid needs.
Since all vegetable fed chicken is a marketing luxury, more money should be put into proper feed formulation to avoid the health problems associated with excess potassium and unbalanced diets.
Venne said that the big question in his mind is, “Is a veggie based chicken diet with excess potassium better for the human consumer, even if the chickens had diarrhea?”
Late in the day the group held a short business meeting. Three drug companies – Intervet, Schering Plough and Merial – were singled out for particular thanks for sponsoring WestVet meetings over the previous 15 years. Dr. Stew Ritchie reported that they had been very successful years with never less than 24 vets in attendance, often from all Canadian provinces plus a number of U.S. states.
“Chicken Stew” then presented toques to the two vets who had travelled the furthest to attend WestVet 16. They were Dr. David Smith of Merial, in Gainesville GA and Dr. Ron Dunphy of St. John's Newfoundland.
WestVet attendees were told that CgFARAD, the organization that provided a centralized database about drug use and withdrawal periods, had insufficient funds to continue operations, with the main staff-member being let go. CgFARAD had been operating with funds provided by a government grant.
Dr. Tom Inglis turned over the president’s gavel to the newly elected Dr. Bill Cox. He will serve until Fall 2006. Dr. Stew Ritchie, aided by Shirley Fast, will continue as secretary-treasurer. Ms. Fast’s work for the organization was signalled by a round of applause.
In the burning question period that followed, Dr. Vicki Bowes summarized the swine flu outbreak that moved west across Canada from Manitoba and which had such a heavy economic toll on the turkey industries in B.C., and later Manitoba and Ontario.
Dr. Bowes went on to describe the effects of the swine flu on the Fraser Valley turkey industry. “It blind-sided us,” she said.
The swine flu had first been found in the U.S., then had moved up into Manitoba, then west to the Fraser Valley, where it infected a flock of turkeys, and had a very heavy economic impact.
The H3N2 virus is not reportable, so the information about the infection could not be disseminated, tying the hands of the lab. Bowes asked, “How can we do our job if confidentiality has to be maintained – for the poultry industry as well as the swine sector.”
Dr. Bowes said that, unfortunately, the turkey industries in both Manitoba and Ontario were similarly impacted, again with heavy economic loss.
Another vet in the audience pointed out that since veterinarians and others in close contact with the H3N2 infected swine herds in the U.S. have sero-converted for that strain of flu, public health departments are very concerned. As during the Fraser Valley avian influenza outbreak, public health is worried that a mutation could trigger human to human transmission.