Mycoplasma | in poultry

What is it and what causes it?

Mycoplasma synoviae and Mycoplasma gallisepticum are small, bacteria-like, organisms that occur in chickens and turkeys. Both M. synoviae and M. gallisepticum primarily infect the respiratory apparatus; in M. gallisepticum this often leads to clinical, often recurrent respiratory problems ("chronic snot"), in M. synoviae the infection often remains subclinical, i.e., without obvious signs of disease. In older laying and parent birds (chickens), M. gallisepticum also causes laying problems (lower production). Strains of M. synoviae frequently occur with greater preference for infecting the joints and oviduct, resulting in lameness, decrease in production and failure.

In fattening turkeys, M. gallisepticum infection can cause great economic damage by stunting growth, increasing failure rates and higher feed conversion rates; also, drug costs in infected flocks are high. Mycoplasma infections cause a robust immune system response, making animals more susceptible to other infections (secondary), such as Infectious Bronchitis and Escherichia coli.

Mycoplasma is transmitted both vertically (from dam to chick) and horizontally (introduction from the environment). The horizontal route of infection is the most important. Infection occurs through contact with contaminated dust or water particles in the air that enter the chicken through the nose or eye mucosa. These particles can also travel some distance outside the farm.

Mycoplasmas are very small and can survive in feathers, dust and manure for days to weeks. In egg material, the germ can survive as long as six to 18 weeks. In a flock of chickens, therefore, they are practically impossible to eradicate. However, they are well susceptible to disinfectants and dehydration. In a clean, dry, empty barn, they will not survive for long.

Because of the organized approach, the number of infections has decreased considerably, but new infections still occur, especially in the laying sector, and Mycoplasma remains a threat.

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Which animal?

Poultry

Broiler breeders are relatively highly infected with M. synoviae and in the laying sector we also still see it relatively often, often at a slightly older age.

Which organ system?

Respiratory system, locomotor system, reproductive system.

How to recognize it.

An infection with M. synoviae causes, depending on the strain involved, lameness due to inflammation of tendons and joints, abnormalities of the eggshell, or a decrease in egg production. When oviducts are affected, the eggshells will become weaker and the percentage of ruptures will increase; we will see lower production and more second choice eggs. This also causes the greatest damage.

M. gallisepticum causes respiratory symptoms in chickens, especially young chickens. Common symptoms are sneezing and nasal discharge. In addition, they may develop small, fluid-filled bumps at the corners of the eyes or a swollen face. In adult animals, depending on the strain, the symptoms are usually milder with possibly a lay drop.

What other symptoms are there?

If young chicks develop a secondary bacterial infection in addition to the Mycoplasma infection, for example with E. coli, respiratory symptoms can be very severe, resulting in severe shortness of breath or even suffocation. Often animals then make roaring noises. Because the problems often recur, this condition is called "chronic snot. Chicks that survive infection usually lag in weight and respond violently to inoculations with live viruses.

What are the risk factors?

Pairs of chickens usually become infected during transport or upon arrival at the new farm. Therefore, it is of utmost importance to thoroughly clean, disinfect and dry the barn when empty. Mycoplasma can also be introduced to a farm through infected persons or materials (egg trays, boots, clothing, farm equipment, drinking troughs). Direct and indirect contact between flocks should therefore be avoided as much as possible. In addition, wild birds that may come in contact with the flock may also transmit the infection. Free-range chickens are therefore more likely to be infected.

What does this disease mean for the farmer and the farm?

Monitoring for Mycoplasma gallisepticum is mandatory for breeding animals.

An infection in a flock of chickens is virtually impossible to eradicate. This is because Mycoplasma can survive in the environment for a long time if it is found in animal material. In addition, the bacteria reside in the respiratory system, where it is difficult for antibiotics to reach. Therefore, the infection remains present in the flock.

Economic damage will mainly be caused by laying drops, respiratory symptoms and lameness among chickens.

How can you prevent the disease?

The management of Mycoplasma relies on detecting infected farms and culling infected reproductive farms because of maternal-to-chick transmission. On-farm prevention of Mycoplasma relies on optimal farm hygiene and vaccination. Vaccination is particularly used in the laying sector to reduce economic losses in the event of infection. Indeed, vaccination reduces respiratory symptoms, production decline, mortality and transmission of the pathogen. To prevent transmission of disease from wild birds, contact with these birds should be avoided.

How can you treat the disease?

Treatment options in laying poultry are very limited due to accumulation of antimicrobials in the eggs. In addition, the infected flock rarely becomes completely free of the germ. Therefore, treatment is given only when the clinical signs warrant it, such as when there is a highly pathogenic (pathogenic) Mycoplasma strain or a secondary bacterial infection. However, symptoms often return after treatment is stopped. The main emphasis in the management of Mycoplasma is to prevent infection.

Alternative names

Chronic snot

Keywords

Mycoplasma synoviae, Mycoplasma gallisepticum, chronic snot

Sources

Animal Health Service, "Mycoplasma in Poultry," accessed November 26, 2021.

Landman, Wil JM. "Is Mycoplasma synoviae outrunning Mycoplasma gallisepticum? A viewpoint from the Netherlands." Avian Pathology 43.1 (2014): 2-8.

Levisohn, S., and S. H. Kleven. "Avian mycoplasmosis (Mycoplasma gallisepticum)." Revue scientifique et technique (International Office of Epizootics) 19.2 (2000): 425-442.

Ter Veen, C., et al. "Decrease of Mycoplasma gallisepticum seroprevalence and introduction of new genotypes in Dutch commercial poultry during the years 2001-2018." Avian Pathology 50.1 (2021): 52-60.

Ter Veen, C., Feberwee, A., Santman-Berends, I. "Monitoring Mycoplasma gallisepticum". Poultry, WUR. April 2017.