Gregorio Rosales, DVM, PhD, an independent poultry health consultant from Athens, Alabama, said pathogenic variants of the disease have increased significantly over the last 5 years.

And while there could be a number of reasons for the increase in outbreaks, the trend coincides with the reduction in antibiotic use in broiler production.

Causes and consequences

In addition to causing drops in production in broiler breeders and shell quality problems, pathogenic MS can affect feed conversion and uniformity in broilers, leading to an increase in condemnations.

In some cases, the disease in broilers can also cause an increase in respiratory diseases, especially in combination with other factors such as infectious bronchitis and even avian influenza.

Rosales said one of the other potential factors in the resurgence of the disease has been the increase in the use of live Mycoplasma gallisepticum (MG) vaccines.

When operations around the world start using live vaccines against MG, they need to reduce the use of antibiotics, which can interfere with vaccination,” he told Poultry Health Today. “That has resulted in some of the flocks being exposed to MS.

“Also, the industry in many parts of the world has been growing, and MS is typically seen in areas where there is a heavy concentration of birds.

“In those areas, you often have commercial layers, broiler breeders and broilers all in the same area, which is conducive to more and more broiler breeders being close to [MS] infected flocks — particularly commercial layers, and in many cases, organic chickens or those raised in backyard operations. It looks like, in some cases, close to 60% of [backyard flocks] have MG or MS and sometimes even both.”

Multiple approaches yield results

To combat the problem, Rosales said producers should take a combination of approaches, starting with sourcing mycoplasma-free stock from breeding companies and keeping birds free of infections throughout the production cycle.

In areas where there is a high risk of exposure to MS, Rosales said vaccination in broiler breeders with a live MS vaccine is a very useful tool — provided it is used correctly.

Environmental factors are also critical, so broiler producers should review their housing and ventilation to ensure broilers aren’t under any unnecessary environmental challenges.

The combination of Mycoplasma infection in broilers and poor management seems to be a really bad combination,” he said.

The impact of MS in broilers is seen on feed conversion, a greater incidence of respiratory problems particularly in combination with other challenges such as infectious bronchitis, cold weather, increased moisture in the litter, and in some areas even avian influenza. These factors combined with MS result in more air sac problems and condemnations at processing time.

Good ventilation is critical, and producers need to monitor conditions particularly at nighttime.

Many operations, particularly in the US, have recognized that these factors combined lead to increased problems and are doing a much better job in doing the basic things correctly, he added. “They are really working on improving chick quality, improving their management, improving the brooding conditions.”

If medication is needed there are products available that can be used in the feed and/or water. However, MS positive broiler flocks in many cases, if managed correctly, do not need to be medicated.

In broiler flocks raised without antibiotics there has been an increase in infections caused by Gram positive bacteria such as Clostridium and Enterococcus.

Despite the increased challenges in maintaining bird health in RWA production systems however, Rosales said he is positive about the industry’s ability to deal with them.

“If we continue to work in doing the basic management correctly, in doing the good things that we should have always done, we can have great success and be very profitable in new systems of production that require no antibiotics.”

Rosales noted that he authored a detailed article on the prevention and control of mycoplasmosis in broiler breeders and broilers that presents the pros and cons of different strategies and emphasizes the importance of biosecurity.¹