Mycoplasma comes in three flavors – Mycoplasma meleagridis, Mycoplasma synoviae, and Mycoplasma gallisepticu. Each one has specific challenges. The least common is M. meleagridis,, and the prevalence of the other two depends on the geographic location. Backyard and hobby flocks have seen near epidemic spread and resurgence in cases of mycoplasma during the last few years. This article provides information about what is important to know to recognize the disease and what steps to take to keep your flock healthy and clear of infection.
Mycoplasma meleagridis (M meleagridis) is an egg-transmitted disease of breeder turkeys that primarily impacts progeny with airsacculitis. It has been associated with decreased hatchability from infected breeder flocks and poor growth and skeletal abnormalities in progeny. M meleagridis is mainly host-specific for turkeys (it does not affect chickens). With successful control programs such as the National Poultry Improvement Plan, major turkey breeders have eliminated the infection and produced eggs and poults free of M meleagridis. However, the risk still exists that wild turkeys can transmit M meleagridis to domestic turkeys, especially if the domestic turkeys are free-roaming.
M meleagridis reduces hatchability and diminishes poult quality and growth rate. Despite high rates of airsacculitis in poults from infected hens, producers might only notice mild respiratory signs. Egg-borne infections may impact early rapid growth of hock joints, periarticular tissues, cervical vertebrae, and the adjacent bone, producing skeletal abnormalities such as crooked (wry) necks or leg deformities. Adult breeders usually witness no signs of venereal or respiratory infection.
Mycoplasma synoviae (M synoviae) occurs most commonly as a subclinical infection of the upper respiratory tract, especially in multi-age layer flocks. M synoviae infection is also a complication of airsacculitis, in association with Newcastle disease or infectious bronchitis. It is distributed worldwide and is seen primarily in chickens and turkeys; however, ducks, geese, guinea fowl, parrots, pheasants, and quail may also be susceptible. M synoviae infections vary tremendously in severity; sometimes there are no visible symptoms and in other instances, it can cause severe disease and mortality. The first signs of infectious synovitis include pale-bluish head parts and lameness in many birds, with a tendency to sit. The more severely affected birds are depressed and found resting around feeders and waterers. Hocks and footpads are swollen, and breast blisters may be visible.
M synoviae is egg-transmitted. The infection rate in breeder hens is low, and some hatches of progeny may be free of infection. Horizontal transmission happens primarily via the respiratory tract, with direct and indirect routes. The incidence of M synoviae infection in commercial poultry in the USA has decreased due to the National Poultry Improvement Plan control programs implemented for chicken and turkey breeders. However, occasional large outbreaks involving breeder and market birds are typically limited to one or a few states and related to one especially virulent isolate. M synoviae infections of multiple-age layer flocks are common and can contribute to decreased egg production. There has been a resurgence in backyard poultry cases, mainly attributed to how the birds move and are acquired.
Mytcoplasma gallisepticum (M gallisepticum) is transmitted vertically from infected breeders to progeny, horizontally via infectious aerosols and through contamination of feed, water, and the environment, and by human activity on fomites (shoes, equipment, etc.). Infection may be latent in some birds for days to months. Yet, when birds experience stress, horizontal transmission may occur rapidly via aerosols and the respiratory route, after which infection and clinical disease spread throughout the flock. Once individuals or flocks are infected, they remain infected for life and act as carriers or reservoirs for infection. Flock-to-flock transmission occurs readily by direct or indirect contact from the movement of birds, people, or fomites from infected to susceptible flocks.
In chickens, the M gallisepticum infection may either be inapparent or result in varying degrees of respiratory distress, including slight to significant difficulty breathing, coughing, and/or sneezing. Nasal discharge and conjunctivitis with frothiness about the eyes may be present. Birds are very likely to show symptoms but less likely to die unless the disease is complicated with other bacteria in the flock; birds struggle to survive M gallisepticum if they are already fighting off another bacteria. M gallisepticum in layers and breeders is usually subclinical yet causes a reduction in the number of eggs laid per hen over the production cycle. In turkeys, which are more susceptible, swollen infraorbital sinuses are frequent. Infection also occurs in pheasants, chukar partridges, peafowl, pigeons, quail, ducks, geese, and psittacine birds. Feed efficiency and weight gains are reduced. Commercial broiler chickens and market turkeys may suffer high condemnations at processing due to airsacculitis. There may be a chronic increase in mortality and a decrease in the overall production rate in laying flocks. M gallisepticum is the most pathogenic avian mycoplasma; however, considerable strain variability exists as seen by the highly variable dose needed for disease expression, how severe the symptoms are, and outcome of the infection.
The National Poultry Improvement Program has been a critical component to increasing the overall poultry health status in the US. Any major hatchery and breeder company is required to test for the disease, and for a long time, mycoplasma was hard to find in backyard flocks as there were few flocks and many were of high health. Lately, I am finding mycoplasma, often with at least one other bacterium, in backyard flocks. To prevent contracting mycoplasma, limit your purchases to birds from mycoplasma-free sources, and do not allow anyone to visit your birds. Likewise, do not visit other flocks without following proper biosecurity protocols. Coop touring events such as a few that groups for hobby flocks recently held and purchasing or rescuing poultry are easy ways to bring in disease. Once the disease is present in your flock, the advice you will receive is to depopulate the flock, clean and disinfect, and start over. Sometimes the condition can be present in your flock without your knowledge. However, disease is often accompanied by hatchability and chick survival issues that can be demoralizing and expensive. Maintain healthy birds by keeping them isolated, purchasing healthy stock, and remaining vigilant about limiting those who interact with your birds and the birds you visit.