Multicausal enteric disease in poultry is characterized by stunted growth, lack of pigmentation, decreased weight gain, elevated feed conversions, poor feathering, and passage of undigested feed in chickens or turkeys. Numerous viruses have been associated with the disease. Presumptive diagnosis is based on clinical signs and microscopic evaluation of intestines from affected birds; however, no confirmatory tests or effective treatments exist.
Multicausal enteric disease in poultry is a general term for infectious intestinal disease, caused by any number of pathogens, that leads to an economically important problem affecting poultry production. In chickens, the disease has been referred to as malabsorption syndrome, pale bird syndrome, and infectious stunting syndrome. In turkeys, it is also referred to as poult enteritis mortality syndrome or poult enteric complex. The many names of multicausal enteric disease are derived from clinical signs in affected birds.
Etiology and Transmission of Multicausal Enteric Disease of Poultry
Multicausal enteric disease in poultry is infectious and has been reproduced with bacteria-free intestinal homogenates, suggesting a viral origin. Numerous viruses (eg, enteroviruses, parvoviruses, astroviruses, caliciviruses, arenaviruses, togaviruses, reoviruses, and rotaviruses) have been implicated.
In the late 1980s, reoviruses were isolated from clinical cases of what was then referred to as malabsorption syndrome in broilers. The disease was reproduced with a reovirus isolated from the tissues of affected birds. However, the reproduction of disease with reovirus or other isolated viruses in similar clinical cases (to support an inference of a causal relationship) has not always been successful, likely due to the multifactorial nature of disease and numerous noninfectious contributing factors.
Many of the viruses implicated in the disease are not cultivable in the laboratory, making it difficult to determine the etiology. Bacteria also likely play a role in the etiology; however, the complex interactions of viruses with bacteria are poorly understood.
Because the disease occurs in very young chicks, viruses are likely vertically transmitted, although fecal-oral transmission occurs after hatching and at placement in the poultry house. In addition to viral etiologies, environmental factors, feed contaminants (eg, mycotoxins), and management can contribute substantially to severity of disease. Cold brooding also can strongly impact severity of disease.
Clinical Findings of Multicausal Enteric Disease of Poultry
Birds that are very young (ie, < 3 weeks old) have an age-related susceptibility to multicausal enteric disease.
A wide range of clinical signs and findings is present in affected flocks, including the following:
diarrhea
vent striping or pasty vents
uneven growth
temporary stunting
permanent runting
lack of pigmentation in the skin, feet, or beak (eg, pale combs, wattles, and legs)
slow or poor feathering (see poor feathering image)
broken or twisted feathers (“helicopter wings”)
undigested feed in feces
poor feed conversion ratios
Courtesy of Dr. Jean Sander.
Other clinical signs can include lameness, osteodystrophy, and secondary encephalomalacia.
Severely affected birds do not respond immediately to changes in feed or management practices and are usually culled from flocks before processing. The number affected in flocks can vary from a few to 90%.
Lesions
Severity of clinical disease observed in field cases varies greatly, as do gross lesions. Gross lesions often include enlarged proventriculi; small gizzards; atrophy of the pancreas, thymus, and bursa; and orange mucus in the small intestinal lumen.
No consistent microscopic lesions are found, although intestinal dysbiosis and villus blunting in the intestinal epithelial lining are commonly observed (see thin-walled intestine image). Damage to intestinal epithelial cells results in decreased nutrient absorption from feed and leads to decreased body weight gain and increased feed conversion ratio.
Encephalomalacia or rickets occurs occasionally, presumably as a result of malabsorption or malassimilation of nutrients.
Courtesy of Dr. Jean Sander.
Diagnosis of Multicausal Enteric Disease of Poultry
Clinical signs and postmortem lesions permit a presumptive diagnosis of multicausal enteric disease in poultry.
Sections of the GI tract from affected birds should be collected for diagnostic evaluation:
The duodenal loop (including pancreas), jejunum-ileum junction, and large intestines should be collected in neutral-buffered 10% formalin for histological evaluation.
Matching samples should be collected separately for molecular testing by PCR and RT-PCR assay.
Because of the disease's complex etiology and the presence of the implicated viruses in normal flocks, diagnostic test results can be difficult to interpret. Poor early flock management (especially feed and water supply and temperature control) can result in similar clinical observations in a flock in the absence of infectious agents.
Prevention and Control of Multicausal Enteric Disease of Poultry
There is no effective treatment for multicausal enteric disease in poultry. Good farm hygiene and good husbandry practices will decrease the burden of challenge caused by multiple infectious organisms.
No vaccines are currently available to prevent disease; however, some reovirus vaccines contain malabsorption syndrome-origin isolates and are marketed to prevent stunting and poor feed conversions due to pathogenic reoviruses.
Good flock nutrition and sanitation and avoidance of intercurrent disease are beneficial. Antimicrobials and vitamin supplements can be helpful. Feeds should be analyzed for dietary toxins, and feed with high toxin levels should not knowingly be fed to commercial poultry. (See Mycotoxicoses in Poultry and Poisonings in Poultry for more information.)
Zoonotic Risk of Multicausal Enteric Disease of Poultry
No reported zoonotic risks have been associated with multicausal enteric disease.
Key Points
Multicausal enteric disease can cause substantial decreases in body weight.
Multicausal enteric disease is likely of viral etiology.
No specific prevention or treatment is available.
For More Information
Poultry enteritis and mortality syndrome. NC State University College of Veterinary Medicine.
Malabsorption syndrome. Poultry World.
See also runting and stunting syndrome in the Viral Enteritis chapter.
