Bacterial Diseases Effecting On Egg Production Of Laying Hens

Poultry is the most vibrant segment of livestock. Pakistan has ranked 11th largest poultry producer in the world.  Poultry meat production showed a growth rate of 9.1 percent whereas egg production showed a growth of 5.6 percent (19.0 billion Nos.)

By Farzana Rizvi, Muhammad Zulqarnain Shakir, Nasir Mahmood and M. Wasim Usmani

There are now over 6,500 controlled environment poultry sheds in the country which indicates that our poultry sector is moving in the direction of modernization and using advanced technology. Despite all these tremendous achievements, the poultry sector is continuously vulnerable to many diseases that affect egg quality and quantity. This chapter addresses diseases and syndromes which have been shown, or are reported, to have adverse effects on egg production and quality. However, any disease of poultry can adversely affect egg production and quality indirectly, by affecting the health of the bird. The main topics are the effect on egg production and quality of bacteria (SalmonellaMycoplasmaEscherichia coli, infectious coryza, OrnithobacteriumGallibacterium, spirochaetosis), viruses (infectious bronchitis virus, egg drop syndrome, swollen head syndrome, avian encephalomyelitis, influenza, Newcastle disease, laryngotracheitis), syndromes (fatty liver haemorrhagic syndrome, cage layer osteoporosis) and toxic agents. A short section on clinical perspectives reports on information obtained from practising poultry veterinarians as such observations can provide valuable starting points for future research.

Key words: egg quality, avian disease, virus, bacteria

Any disease of poultry can adversely affect egg production and quality either directly, by having effects on the reproductive system, or indirectly, by affecting the health of the bird. Respiratory infections which result in air saculitis may, in turn, infect the ovary and oviduct. In addition, some diseases infect the oviduct and ovary by ascending infection. It is frequently difficult to diagnose the cause or causes of reduced egg quality because it is often a combination of factors that leads to poor egg quality. Management, nutrition, and disease may, in combination, result in a reduction in egg internal quality and/or eggs shell quality. Here are some bacterial diseases that affect egg production and quality.

Effects of bacterial disease on egg production and quality

  1. Salmonella

These are infections caused by Salmonella Gallinarum (S. Gallinarum) and Salmonella Pullorum (S. Pullorum) and include pullorum disease (PD), fowl typhoid (FT), and infections of chicks and hens that are characterized by septicemia. Adult fowl are prone to fowl typhoid, while young fowl are prone to pullorum disease. The transmission sources of Salmonella Gallinarum (S. Gallinarum) are hatcheries, feed, and poultry houses. On the other hand, Salmonella Pullorum (S. Pullorum) transmission can occur within 48 hours of hatching, in which case shell penetration and feed contamination occur at a lower rate. S. Pullorum localizes in the reproductive tract of layers, and more densely in the ovary and oviduct with sexual maturation.

Clinical signs in layers: egg production and quality

Amorphous and cystic follicles can cause minimal lesions such as small nodules or regression of ovarian follicles and can be seen when chronic infection occurs. In this case, the oviduct fills with a caseous exudate, causing the dysfunction of the ovary and oviduct, thus leading to peritonitis. Transovarian infection can occur. Experimental infection of birds with Salmonella Enteritidis increased the incidence of hairline cracks in eggs, leading to an increased risk of contamination.

  1. Fowl Cholera

This is a septicemic disease of domestic and wildfowl with high mortality and morbidity rates, caused by Pasteurella multocida (P. multocida) of the Pasteurellaceae family. Adult chickens are more prone than young fowl, and broilers are more resistant to the disease than layers, resulting in deaths at higher rates in laying hens.

Epidemiology

Transmission occurs through the digestive tract, respiratory tract, skin, and conjunctiva, and is particularly transmitted through the feces or oral/nasal discharge of animals that have recovered from the infection.

Clinical signs and symptoms

The ovaries are infected cases of acute cholera in laying hens. Matured follicles take on a flabby and densely vascularized appearance, and the follicular content is released into the peritoneum as soon as the follicles rupture. The stroma of unmatured follicles and ovaries is hyperemic, which leads to a decrease in production in laying hens.

  1. Mycoplasma

Etiology

Mycoplasmas are eubacteria devoid of cell walls and are members of the class Mollicutes, Order I Mycoplasmatales. Genus I, Mycoplasma, has more than 100 species of which 25 infect avian species, and 10 of which infect chickens.

Epidemiology

Mycoplasma gallisepticum causes chronic respiratory disease (CRD) in chickens as well as infectious sinusitis in turkeys and often co-occurs with a respiratory virus infection. Oviduct infection can occur owing to proximity to infected air sacs. Msynoviae also causes respiratory disease but can become systemic, causing disease primarily in joints and tendon sheaths in chickens and turkeys. Mgallisepticum and Msynoviae also infect a range of other avian species.

Clinical signs in layers: egg production and quality

Decrease egg production, co-inflammation of the cornea and conjunctiva, facial edema, and tear secretion are clinically apparent. Oviduct thickening and salpingitis in laying hens are causes of decreases in production. Chicks that hatch from the eggs of infected animals play a significant role in lateral transmission. The most significant route is transmission through eggs. Vertical transmission through infected eggs is observed. MS infection is seen in chickens older than 4 weeks of age. It is usually an upper respiratory tract infection. Strains isolated in recent years were frequently isolated from flocks with decreased egg production and egg defects. The agent causes the eggshell to become thinner, lose opacity, and develop a rough surface. Thus, eggs tend to crack or break more easily. The agent causes more than 10% of eggs to be unfertilized as well as a decrease in egg production.

  1. Colibacillosis

Etiology

This is a disease that is characterized by colisepticemia, hemorrhagic septicemia, coligranuloma, air sac disease, swollen head syndrome, venereal colibacillosis, cellulitis, peritonitis, salpingitis, osteomyelitis, yolk sac infection and enteritis caused by the avian pathogenic Escherichia coli (APEC) of the Enterobacteriaceae family.

Epidemiology

  1. Ecoliis commonly found in the intestines of poultry and is transmitted to eggs primarily by faecal contamination of the shell surface followed by entry into the egg.

Clinical signs in layers: egg production and quality

Inflammation in the oviduct due to APEC results in the reduction of egg production and sporadic mortality. Exudate, which accumulates with the inflammation that occurs because of egg peritonitis causes the formation of egg yolk that coagulates in the body. In addition, colisepticemia, which affects egg production, can often be seen in young laying hens, but rarely in mature animals.

  1. Infectious Coryza

Chickens are natural hosts of the agent Avibacterium paragallinarum (A.paragallinarum). The disease is characterized by swelling around the eyes and face

Epidemiology

The agent is transmitted through secretions and excretions between animals. Transmission can also occur through the exchange of machinery/equipment between farms, and also by personnel

Clinical signs and symptoms

It causes a 10–40% decrease in egg production. The morbidity of the disease is 80–100%, while mortality is around 10%

  1. Ornithobacterium rhinotracheale (ORT) Infection

Etiology

Ornithobacterium rhinotracheale is a Gram-negative, non-motile, pleomorphic, rod-shaped, a non-sporulating bacterium.

Epidemiology

  1. Orhinotrachealecauses respiratory disease in chickens and a wide range of other avian species. High seroprevalence of Orhinotrachealewas found in a study in the north-central region of the United States. The organism is transmitted vertically.

Clinical signs in layers: egg production and quality

Clinical signs are respiratory disease and the severity of the disease is worsened when birds have coexisting infections with other respiratory disease agents. It can also develop into peritonitis. In commercial laying flocks, Orhinotracheale results in production drops, decreased egg size, misshapen eggs, and increased mortality. Similar symptoms have been reported for flocks of broiler breeders.

  1. Gallibacterium anatis

Etiology

The genus Gallibacterium is in the family Pasteurellaceae and contains avian bacteria formerly known as Pasteurella haemolyticaActinobacillus salpingitidis or Pasteurella anatis. It includes the species Ganatis and Ggenomospecies 1 and 2. Ganatis comprises two biovars, a hemolytic biovar haemolytica, and a non-hemolytic biovar anatis.

Epidemiology

Gallibacterium spp can be isolated from a wide variety of birds.

Clinical signs in layers: egg production and quality

Gallibacterium anatis, biovar haemolytica, has been suggested as causing peritonitis and salpingitis in chickens and other species and has been isolated from laying birds suffering from reproductive disorders. Similar symptoms have been induced experimentally.

  1. Spirochetosis

Etiology

Spirochaetes are classified in the Order Spirochaetales which contains three families, Spirochaetaceae, Brachyspiraceae, and Leptospiraceae, and a total of nine genera. However, spirochaetes that cause avian intestinal spirochaetosis (AIS) are all of the family Brachyspiraceae, genus Brachyspira.

Epidemiology

AIS occurs primarily in flocks of layers and broiler breeder hens so is a disease of birds that are producing eggs. A survey conducted in eastern Australia reported that birds in 43% of broiler breeder and 68% of layer flocks were infected with intestinal spirochaetes but no broiler flocks were infected.

Clinical signs in layers: egg production and quality

Intestinal spirochaetes colonize the caecum and/k8or rectum and can cause diarrhea. The disease also results in reduced egg production and hatchability and eggshell quality deteriorates.

Conclusion

It has been demonstrated that egg production loss can be attributed to several causes other than management error in establishments, with infectious agents led by bacterial and viral diseases emphasized. When infectious factors affecting egg production are considered individually, the measures to be taken in poultry houses should be considered more significant than the treatment of disease. Accordingly, every poultry house/establishment should prepare a biosecurity plan. Protection, control, and eradication program should be implemented with information obtained from monitoring of the diseases that affect egg production.

 

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