Range of Health Issues Addressed in Final AVMA Poultry Session28 December 2013
Among the topics discussed in the final 'Miscellaneous' session on poultry disease at the 150th annual convention of the American Veterinary Medical Association (AVMA) in Chicago in July 2013 were clostridial dermatitis in turkeys, Intestinal Dilation Syndrome in brown hens, health issues in small flocks and an unusual condition causing elevated mortality in young broilers.
Effects of Haemorrhagic Enteritis Virus Infection in the Development of Clostridial Dermatitis in Turkeys
Clostridial dermatitis is an acute disease causing high mortality and significant economic losses for the turkey industry, explained Anil J. Thachil of the University of Minnesota. Clostridium septicum and C. perfringens have been consistently isolated from these cases but experimental reproduction of disease through oral route is often unsuccessful.
The objective of this study was to investigate the development of clostridial dermatitis in turkeys due to C. perfringens and C. septicum, with and with out post-haemorrhagic enteritis virus infection.
Twelve-week old turkey poults were exposed to haemorrhagic enteritis virus orally. The birds with and without post-haemorrhagic enteritis virus infection were exposed to C. perfringens or C. septicum orally or subcutaneously to investigate the development of clostridial dermatitis.
Birds exposed to C. perfringens orally did not show any clinical signs where as birds exposed to C. perfringens and coccidia showed signs of diarrhoea, necrotic enteritis and clostridial dermatitis. However, birds exposed to C. septicum orally with or with out haemorrhagic enteritis virus showed no signs of enteritis or clostridial dermatitis in this study.
Birds exposed to C. perfringens and C. septicum through subcutaneous route showed the highest incidence of clostridial dermatitis.
Thachil commented the the findings support more of a subcutaneous route of infection than oral route of infection for clostridial dermatitis in turkeys.
Clinical Presentation and Pathology of Intestinal Dilation Syndrome (IDS) in Cage-Free Brown Layer Breeders and Brown Layers
This clinical report presented by the University of Georgia's Guillermo Zavala, summarises relevant characteristics of IDS, a newly recognised economically significant condition of cage-free brown layer breeders and layers.
IDS has been observed in various countries, including the US, Mexico, Costa Rica, Chile, Brazil, Japan and various European countries.
The syndrome, which may affect different breeds or breed crosses of brown layers produced by various primary breeders, is characterised by a severe dilatation of the mid-gut, approximately 10 to 15cm proximal and distal to Meckel’s diverticulum. Severe emaciation, volvulus, torsions, impactions and ulcerations are common consequences or complications of IDS, which invariably occurs after 25 weeks of age and peaks before 40 weeks of age.
IDS can be present in flocks vaccinated or treated preventatively against coccidiosis, and always occurs in birds reared on the floor but virtually never in caged layers or layer breeders.
Split-sister flocks reared in cages versus on the floor exhibit the syndrome exclusively in hens reared on the floor. White Leghorn breeders reared simultaneously in the same premises and fed the same ration never developed IDS whereas the brown breeders did.
Affected hens are almost always non-egg-producers and their frequency may reach up to 15 to 20 per cent of the flock in severe cases. Microscopically, the intestinal lamina propria is severely thickened due to gross infiltration with mononuclear cells, heterophils and macrophages.
Some specimens may display significant eosinophilic infiltration, which would suggest a possible allergic reaction and/or a response to parasitic insult. However, Zavala commented, no significant specific infections or infestations have been consistently found so far.
Multi-state Disease Survey of Backyard Poultry and Small Commercial Flocks
Raising small chicken flocks in urban and suburban areas is a growing activity in the United States. Jarra F. Jagne from Cornell University's College of Veterinary Medicine reported that there is very little information on backyard poultry flock populations and disease status.
These flocks represent a unique challenge for poultry veterinarians and the poultry industry in terms of disease control and management. Veterinarians working in the field and in diagnostic laboratories are increasingly dealing with cases from small backyard and commercial flocks.
The purpose of this informal survey was to bring together disease information from such flocks from the period covering August 2011 to August 2012.
The survey information came from a total of 12 state/university diagnostic labs covering a wide geographic region. Survey respondents were asked to provide the number of diseases diagnosed in backyard chickens, turkeys, game birds, ducks and other species.
Analysis of the survey results showed intestinal parasites topping the list for all the species followed by respiratory diseases caused by bacteria, viruses and mycoplasma.
Marek’s disease seemed to be quite a significant problem and was marked by presence of both visceral and nerve lesions.
With a small sample of 12 diagnostic labs responding to the survey, Jagne said, a clear picture of diseases present in backyard flocks emerged and points to the importance this growing sector has for the poultry industry.
The Disease Triad Revisited: A Brief Anthology of the Role of the Non-infectious Factors in Infectious Poultry Diseases
Many modern poultry diseases are multifactorial in nature, that there is considerable variability in the clinical expression of the infectious diseases, and occasional discussion as to the putative role of the some infectious agents in the disease process, when Koch’s postulate does not necessarily yield straightforward answers.
A presentation by Daniel A. Bautista from the University of Delaware-Lasher Laboratory highlighted a collection of interesting poultry disease cases that may serve as a stimulus for discussion and a continuing education opportunity in poultry disease diagnosis for beginners and experienced poultry disease professionals alike.
What Happened at Peter’s Farm? Part 1: Field Diagnosis
Philip A. Stayer of Sanderson Farms, Inc. presented the first of a three-part series on an unusual mortality pattern of 14-day-old commercial broiler chickens in four of six houses on a contract grower’s farm.
The state diagnostic laboratory first reported dehydrated birds with severe corneal abrasions - presumably from excessive ammonia exposure - seen in the sample birds submitted for necropsy.
A farm visit by the attending clinician revealed severe non-uniformity upon entry into any of the four affected houses with many birds not moving, eyes closed and ruffled. Most birds appeared 'ammonia-blind' despite low ammonia levels (<20ppm as detected by smell).
Gross lesions seen in the birds necropsied on the farm included severe corneal ulcers, dark muscles (dehydration), swollen proventricular glands, excessive proventricular mucus, occasional gizzard erosions and pale, urate-laden kidneys. Gizzard contents contained some normal appearing moist feed contents, with green-stained contents closer to the mouth than the normal feed colour.
Mortality peaked during the third week of grow-out but persisted into the fifth week.
Multiple farm visits by multiple veterinarians did not definitively determine causative agent. Flock was treated based upon presumptive diagnosis and laboratory tests. A later challenge model recreated some of the gross lesions seen in the clinical case.
What Happened at Peter’s Farm? Part 2: Laboratory Diagnosis
Danny L. Magee from Mississippi State University College of Veterinary Medicine presented the second of this three-part presentation on an unusual mortality pattern of 14-day-old commercial broiler chickens. Mortality peaked during the third week but persisted into the fifth week. During the progression of the flock, feed, water and tissue samples were taken for laboratory analyses.
Copper, aluminium and zinc were tested in feed, ingesta and organs. Feed and body fat from affected birds were tested for pesticides. Water was tested for routine water quality measures. Water and ingesta were simultaneously tested for pH. Blood chemistry was determined for affected and unaffected birds.
Laboratory tests determined affected birds had endured a metabolic challenge and that the meat was safe for human consumption.
What Happened at Peter’s Farm? Part 3: Challenge Models
The final part of a three-part series on an unusual mortality pattern of 14-day-old commercial broiler chickens was presented by Philip A. Stayer.
Two challenge models were tested with naïve commercial broilers reared in test cages. One model recreated some of the lesions but not at the level of severity seen in the diagnostic case. The second model did not induce any lesions with the suspected causative agent. Both models started with young chicks and ran over two weeks duration.
Further details of the challenge models were discussed at the meeting.
Use of Poultry Production Expertise to Impact Childhood Malnutrition in Developing Countries
Many opportunities exist for poultry professionals to use their experience and education for the purposes of commercial poultry production, according to Albert M. Payne of Elanco Animal Health. With the ongoing demands of the production environment, it is often easy to overlook the other opportunities that this wealth of knowledge and expertise can have in the ultimate value of animal agriculture - feeding a hungry world through the reduction of food insecurity.
His paper reviewed an ongoing project in the Western Highlands region of Guatemala to improve childhood nutrition through a sustainable programme of small flock broiler production and supplemental farming to provide a higher quality of protein and nutrition to families with young children.
The paper aimed to share the adjustments and ingenuity used to teach rural families the basics of poultry husbandry and how to apply that knowledge in their local villages and homes.
Procurement of supplies and obtaining broiler genetics were presented by Dr Payne. A review of the strategy for future growth and opportunities for replication in other developing parts of the world were discussed.
He shared key lessons learned over the past few years in hopes that others that have similar opportunities to use their agricultural expertise will be more confident in knowing that food insecurity can be addressed in many ways, including poultry production in developing countries.
Find out more information on the diseases mentioned by clicking here.