Emerging and Re-emerging Diseases of Poultry

Prof. R.N.Sreenivas Gowda*

*(Author: Former Prof and HOD department of Pathology, Veterinary College, UAS Bangalore, Former director, IAH&VB, Bangalore and Former and Founder VC, KVAFSU, Bidar)

Emerging infectious diseases can be defined as infectious diseases that have newly appeared in a population or have existed but are rapidly increasing in incidence or geographic range. The main reasons for emerging and reemerging diseases are:

• Increasing contact between wild animal species, livestock, and humans. (Zoonotic infections).
• Managemental aspects such as high stocking density, poor management, ventilation, and condition of litter, high levels of toxic gasses such as ammonia and carbon dioxide, hygiene, coexisting diseases, and secondary infections. 
• Global environmental changes such as altered temperatures in recent years and as humans continue to expand the boundaries of cities, living areas, and agricultural land.
• The emergence of highly pathogenic H7N9 AIV is an example of the problems associated with intensification of poultry production world over.

All of these factors increase the risk of emergence of new infectious diseases into the human and animal populations.

CLASSIFICATION

1. New diseases

In recent years, a number of emergent viruses have been identified in the global poultry population. These viruses can be mainly categorized into two groups:

1. Emerging novel poultry viruses, such as Astroviruses Causing Fatal Gout in Goslings, chicken circovirus, and diverse Avian Gyrovirus, which are found for the first time in poultry, West Nile virus and the Nipah virus,   avian metapneumovirus (aMPV)  and several new AI  strains.
2. The two most prominent viral emerging diseases to affect poultry in recent years are Poult enteritis mortality syndrome (PEMS) and hepatitis E virus infection, associated with hepato -speleno megaly or big liver and spleen disease (BLS).  non-enveloped RNA herpesvirus referred to as avian hepatitis virus (HEV), BLS was first described in Australia in the 1980s and later in the U.K. and U.S, then spread to   broiler and layer breeders world over. It is characterized by reduced egg production, increased mortality and enlarged livers and spleens. Turkey coronaviruses (TCV) and turkey astroviruses have been implicated, together with reoviruses and entropathogenic E.coli as secondary complicators.
3. Diseases that were believed to have disappeared but appear now in new form:
4. Highly virulent strains of Marek’s disease. Various possibilities that can occur through viral recombinations have been discussed by researchers. It has been described that recombinations can occur between Marek’s disease virus (an oncogenic herpesvirus), fowl pox virus and various oncogenic retroviruses.
5. These researchers point out that it is now recognized that Chicken Anaemia Virus (CAV) was created by several inter-family recombination events occurring between animal and plant viruses.
6. Virus may originate from another avian species,
7. Spread of Egg Drop Syndrome virus and Avian Influenza from wild birds to domestic poultry.
8. avian metapneumovirus, infection from ostriches in Africa.

Re-emerging poultry viral diseases

The most recent vital problems of poultry have been respiratory diseases. Avian flu, infectious bronchitis, Newcastle disease, avian metapneumovirus. All these ae expressing Changes in the pathogenicity, clinical signs and postmortem lesions.

• Infectious Laryngotracheitis Virus, ILV in young broilers.
• vv Marek’s disease
• Infectious Bronchitis Virus- QX genotype, first encountered in 2004, is identical in S1 sequence to a virus isolated in China in 1996.
• Infectious bronchitis (VVIBD)
• Fowl Adenovirus. (Fadv)
• Avian Hepatitis -E.
• Runting /stunting syndrome (RSS)
• inclusion body hepatitis (IBH)
• Egg Drop Syndrome virus (EDS76) 
• HPAI -H5N1 

Emerging and re-emerging Bacterial diseases

In addition to avian mycoplasmosis, erysipelas, Necrotic Enteritis and chlamydiosis appear to be making a comeback. The  re ports during recent years Salmonella (specially S. enteritidis) and Campylo-bacter sp. are the most common causes of human foodborne bacterial diseases linked to poultry products.

Worldwide the new emerging bacterial diseases are appearing such as Amyloid Arthropathy( isolation of Enterococcus faecalis (E. fae-calis) and a reovirus ) and Ornithobacterium rhinotracheale infections.

• Avian Mycoplasmosis, Erysipelas, Necrotic Enteritis and Chlamydiosis appear to be making a comeback.
• In recent years reveal Salmonella (specially S. enteritidis) and Campylobacter sp. are the most common causes of human food borne bacterial diseases linked to poultry products.
• Escherichia coli, Salmonella and Campylobacter jejuni are capable of inducing human disease.
• Just after hatching, disease transmission is mainly vertical, specifically poor hatching conditions and improper sanitation in the hatchery (omphalitis/yolk sac infection). This transmission can lead to infections with mycoplasma, aspergillus, E. coli, salmonella, pseudomonas, streptococci, staphylococci, encephalomyelitis, and hepatitis.
• Ornithobacterium rhinotracheale, E. coli, and mycoplasma are the most common poultry diseases around the world. 
• Enteric disorders that result from combined infection by rotavirus, coronavirus enteritis, and parasitic infestation problems and E. coli cause substantial losses to the poultry industry.
• Bacterial infections and microbial food borne diseases: Salmonella (specially S. enteritidis) and Campylobacter sp. Are the most common causes of human food borne bacterial diseases linked to poultry. Recently, verotoxin producing Escherichia coli 0157:H7 (VTEC) has surfaced as an additional food borne pathogen causing human illness. In addition, Clostridium perfringens and Listeria species and their toxins cause food borne infections.

Metabolic Diseases of Breeders:

A metabolic disease only develops if there is an altered expression of a specific set of genes. This altered pattern of gene expression may be the result of a combination of factors such as environment, genetic origin and nutrition.

Poultry metabolic diseases occur primarily in two body systems:

1. Cardiovascular ailments, which in broiler chickens and turkeys are responsible for a major portion of the flock mortality;
2. Musculoskeletal disorders, which account for less mortality, but in broilers and turkeys slow down growth (thereby reducing profit), and cause lameness, which remains a major welfare concern. In addition, conditions such as osteoporosis and hypocalcaemia in table-egg chickens reduce egg production and can kill.

Metab0lic Diseases

The chickens ( layers and broilers) affected by different metabolic disease which lead to increase the mortality and economic losses in flocks production , the important diseases which occur due to metabolic disorder are:

1. Sudden death syndrome (SDS), also known as flip-over disease, is characterized by the sudden death of birds that show no clinical signs of illness. SDS is believed to be a metabolic disease related to high carbohydrate intake.
2. Ascites, also known as”‘water belly,” is a disease in which fluid accumulates in a bird’s abdominal cavity.
3. Calcium tetany:  is one of the metabolic disease of chicken. A condition known as hypocalcemia, or calcium tetany (paralysis), has been seen in modern or high-yielding broiler breeder hens  appear at the onset of lay to peak egg production.
4. Fatty liver hemorrhagic syndrome: is a metabolic disorder that can occur when chickens are fed high-energy diets but have limited exercise to use up that energy. Diagnosis of the disorder is based on the sudden death of chickens and the occurrence of liver hemorrhage and fat engorgement when the chickens are necropsied. The disorder is controlled by balancing the levels of energy and protein in the diet. Supplementing the feed with selenium may also help.
5. Avian Urolithiasis (Visceral Gout): is a metabolic disease of chickens, with accumulation of urates in kidney and ureters. Due to its striking lesions, many names have been used to describe visceral gout, such as acute toxic nephritis, renal gout, kidney stones, nutritional gout, nephrosis and others.

Breast muscle defects

Green muscle disease:

It also called deep pectoral myopathy, is a degenerative muscle disease that affects the breast tenderloin (minor pectoral muscle) deep within the breast.

White-striping

White striping is a quality factor in chicken breast meat caused by deposits of fat in the muscle during the bird’s growth and development. It is like marbling in red meat.                   Dr Leeson joked that it be promoted as marbled chicken – like Wagyu beef. Because hypoxia is associated with white striping, it was thought that arginine supplementation could help with vasodilation, thus supplying the muscles with better oxygen resources.

Wooden breast (WB)

WB is an emerging  quality defect in breast muscle,  the condition starts by . fatty white blood cells, known as lipid-laden macrophages (LLM), that are located close to the veins are the key cells responsible for modifying the breakdown and storage of fats in the muscle at the onset of wooden breast. Macroscopically, it is characterized by palpably hard, pale ridge-like bulges at the caudal end, along with clear viscous fluid, small hemorrhages, and white striping, that may occur separately or together. The main cause is the high growth rate and high breast meat yield. There is no nutritional or management solution.

SKELE TAL DISORDERS / Skeletal integrity

These are not new but repeatedly occur in breeder chicken, either genetic, infectious  or deficiency in fast growing breeds, They have to be carefully monitored.

• Tibial dyschondroplasia (osteochondrosis)
• Cage layer fatigue (osteoporosis)
• Rickets (osteodystrophy)
• Chondrodystrophy (Perosis),
• Angular bone deformity,
• Valgus Varus bone deformity)
• Spondylolisthesis (Kinky back, Scoliosis)
• Femoral head necrosis (Brittle bone disease)
• Foot pad dermatitis (Podo -dermatitis)

CONCLUSION

Emerging and re-emerging viral infectious diseases have been a continual concern for the poultry industry. In recent years, a number of emergent viruses have been identified in the global poultry population. Emerging infectious diseases are infections that have recently appeared within a population or those whose incidence or geographic range is rapidly increasing or threatens to increase in the near future. Emerging infections can be caused by: Previously undetected or unknown infectious agents.

Early recognition and monitoring programs are essential in managing the infections and minimizing the economic impact. With new and re-emerging diseases evaluating their economic impact is essential to determine whether new control measures and especially new vaccines are needed.
*(Author: Former Prof and HOD department of Pathology, Veterinary College, UAS Bangalore, Former director, IAH&VB, Bangalore and Former and Founder VC, KVAFSU, Bidar)