Infectious disease viral in origin characterized by alterations of the membranes, synovial, tendon sheaths, and myocardium. Viral arthritis is also known as “tenosynovitis.”

The malabsorption syndrome is produced by the same causal agent, and is presented as a disease with digestive symptoms or poor absorption of food.

Symptoms may include be of three types:

– General:

Sometimes these symptoms do not appear, and the flock appears normal. In some cases, certain birds tend not to move, and when forced to do so, they show signs of lameness.

Locomotives:

The birds exhibit lameness. Have tendon thickened and appears above the joint tarsal, a nodule of two or three centimeters.

– Digestive “malabsorption syndrome”:

It is a condition characterized by sparse feathering, with the feathers on the upper front part of the back standing on end, giving the appearance of helicopter blades.

Both in the form of lameness as in the syndrome of malabsorption, the morbidity, and mortality vary dramatically among the lots affected.

History:

Since the late 1970s, the poultry industry has been facing a new problem that undermines the economic efficiency of meat production, a condition now known as malabsorption syndrome.

This disease was believed to be caused by various factors that lead to malabsorption of nutrients and result in a wide range of clinical and pathological manifestations; these factors include the effects of certain viruses on the digestive system, mycotoxins, management practices, genetic factors, and others.

The disease was first identified and studied in broiler chickens, which suffer the greatest economic losses, but it has since been diagnosed in laying hens and turkeys as well. First described in the Netherlands, the disease has spread rapidly around the world, and today nearly every country is affected by it, including ours. Reoviruses are currently considered a key factor in the disease.

The following is a summary of the key findings regarding this condition, drawn from the extensive existing literature on the subject. In the Netherlands, Kouwenhoven and colleagues described a syndrome in broiler chickens in the late 1970s, characterized by dwarfism, poor feathering, and leg weakness, which was later reproduced experimentally in broiler chickens.

Inoculating material by the pro ventricle and intestine of chickens affected; and in this way open the door to a possible infectious cause, for what was there called the condition of the “Dwarfism infectious”, because it slows the growth of affected animals, was a fact of great significance.

Subsequently, outbreaks with similar characteristics were reported in various European countries, each of which was given a different name based on the predominant clinical and pathological findings:

— Disease of the chicken helicopter: Due to the bad position of the feathers in the wings.

Dwarf Chicken Syndrome: By the relatively high percentage of birds that do not reach the size and the desired weight.

Avascular necrosis of the femoral head: Since this lesion has been found in adult chickens in some cases.

Brittle bone disease: Or osteoporosis due to the bone fragility that often accompanies it, etc. In the early 1980s, similar outbreaks began to be reported in the United States, where the disease spread rapidly, receiving the names mentioned above and others such as:

Pale Chicken Syndrome By the lack of pigmentation of the ridge, the chins, and plants.

—Infectious ventriculitis: The frequency of this injury in cases in which it was studied. 

— Malabsorption syndrome: According to Van der Heide in 1982, this is because the chicken apparently consumes the necessary nutrients but, for some reason, does not absorb them.

In addition to Europe and the United States, this disease has been confirmed in South America, Mexico, Australia, etc

Economic importance:

The most significant losses associated with this disease have been the stunted growth of affected animals, which can account for 5 to 30% of the affected flock, resulting in a reduction in slaughter weight of up to 30 or 40% compared to healthy birds.

Some compensatory growth can be expected starting in the seventh and eighth weeks of rearing for these animals, which would entail extending the fattening period and incurring considerable feed costs—a measure that generally does not justify such an extension.

In addition to weight loss caused by dwarfism, injuries to the musculoskeletal system that result in lameness further hinder weight gain.

The de-pigmentation which often appear in all the sick animals makes the chicken to diminish significantly its value in the market affected the aesthetics of the product and appear to an animal with less nutritional value, while all other indices are satisfactory.

The mortality tends not to be a factor of great concern within the economic losses, since they are usually low between 5 and 7 %, although it may be much higher in cases associated with other diseases and processes such as bursitis and infectious avian coccidiosis.

Etiology:

It has been noted that the increased growth rate of today’s broiler chickens contributes to the onset of stress when feed is unable to fully meet their nutritional requirements—both in terms of quantity and quality—particularly with regard to:

Essential amino acids, vitamins A, B, E, and the B-complex, as well as certain minerals; therefore, any factor that interferes with the normal absorption of nutrients could lead to the development of what is now known as malabsorption syndrome, which is why the theory of its multifactorial aetiology is gaining increasing support.

Viral agents:

Viruses are commonly isolated from sick birds, particularly from the digestive tract, and many of these isolates have been able to reproduce the disease. Among the wide variety of viral isolates obtained, the largest percentage has been reoviruses; however, the experimental reproduction of the disease using such inoculants is not always successful.

Many of the isolated reoviruses with proven pathogenicity share the same antigenic properties as the reference strain used for the production of viral arthritis vaccines (strain S1133); therefore, reoviruses—and especially those that share these antigenic properties with strain S1133—could play an important role in the development of this condition.

The viral arthritis reovirus, isolated from clinically affected field cases of this disease, has been shown to cause SMA under experimental conditions, with a higher incidence in chickens fed high-energy diets.

Other viruses have also been isolated in natural outbreaks of the disease and, as agents that cause diarrhea, may well be important factors in SMA; these include:

Parvovirus, calicivirus, adenovirus, and coronavirus, although little is yet known about their actual role.

Nutritional factors:

Since the pathophysiological basis of SMA is associated with malabsorption of nutrients, various authors agree that poorly balanced diets or diets lacking certain key nutrients could produce the same effects as the action of various biological agents or promote the progression of the disease following exposure to these agents.

Rickets and osteomalacia, which commonly occur in birds affected by SMA, have been observed in broiler chickens due to vitamin D deficiencies when mineral levels have been poorly balanced.

Encephalomalacia, stunted growth, feathering problems, and rapid growth are also described as very common nutritional deficiencies in the rearing of high-performance broiler chickens.

Factors toxic substances (mycotoxins):

The harmful effects of mycotoxins on the economics and management of broiler chicken production have been well established, and among their main effects are:

Its detrimental effect on immune processes, its negative impact on growth, and its interference with proper nutrient utilization.

— Increased morbidity depresora of renal function and disorders of pigmentation of the birds.

Locomotor disorders in broiler chickens have repeatedly been linked to the effects of mycotoxins.