Avian Mycoplasma Control – Central For Antibiotic Independent Production

C.J. MORROW Bioproperties, Ringwood, Victoria, Australia

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The effects of avian mycoplasma infections are overt disease (often chronic), subclinical losses and antibiotic dependence. Routine administration of antibiotics in broilers at 18-22 days was developed to prevent Chronic Respiratory Disease in vertically mycoplasma infected broilers. The timing of this administration is after all the birds are infected but before overt disease occurs. The routine administration of antibiotics to layers (and in some parts of the world breeders) every 4 to 8 weeks during lay is to similarly knock back mycoplasma on a regular basis. Mycoplasma infection freedom (MIF) was developed as a strategy to prevent these problems. It has one big problem which is that the birds in uninfected flocks are totally unprotected against infection. Live vaccines that are safe (low transmission) and efficacious (protecting against wild strain disease) can provide the additional benefit of increasing the resistance of flocks to mycoplasma wild strain infection. This is particularly important where neighbouring operations may not have the same priority on controlling both MG and MS and challenge is continuous. Having vaccines to protect against both MG and MS infection means that no antibiotics are needed. Other infections that routine antibiotics have controlled include Brachyspira, Avibacterium and Pasteurella but these can be attacked with biosecurity, other interventions and vaccines as well and are not the universal problems that mycoplasma infections are. MIF is at the core of being able to farm poultry and egg layers in modern production systems without dependence on routine therapeutic antibiotic administration and perhaps with vaccination should be considered state of the art in high risk areas.

In chickens Mycoplasma gallisepticum (MG) and M. synoviae (MS) are chronic infections that have been causing big problems including disease, production inefficiencies and antibiotic dependence since the development of modern production systems.

Although a lot of people have the opinion that MS infection has little impact in layer, or sometimes even breeder operations, this opinion has to be interpreted with an understanding of the antibiotic use in the organisation. Sometimes production people look at antibiotics in-production out whereas the veterinary view is antibiotics in- production out- therefore a bacterium is part of the problem.

Morrow (2014) described the rationale behind mycoplasma control being central to reducing antibiotic dependence in poultry industries. This paper will look at examples where antibiotic reduction has followed introduction of MS control by MSH vaccination and total mycoplasma control by MSH and ts-11 vaccination.

Materials and methods

Case studies of antibiotic reduction from introduction of live mycoplasma vaccination

Case studies on the impact of the introduction of live mycoplasma vaccination on antibiotic usage were collected from individual supervising veterinarians (Table 1) in various parts of the world. Most were where MS associated disease was confirmed and antibiotics had been used for a long time with varying degrees of success in controlling clinical signs. The US study was where MSH vaccine was used under permit.

One study in Indonesia looked at a straight substitution from F strain vaccine and antibiotic to MG ts-11 and MS MSH vaccine with no antibiotic in a large poultry company with broiler breeders and layer breeders. The data presented concerns the broiler breeder side of the company and does not include benefits past DO broiler chicks or layer information. The DOC price here was chosen as 30c per chick while the feed price was U$700 per tonne.

Estimate of the total antibiotic usage in Europe combating MS infection

Using the data from Feberwee et al 2008 on the prevalence of MS infection in the Netherlands, a dose rate of 25 mg/kg and treatment regimens typical of European production systems, an estimate of the total amount of antibiotic used against MS in the EU was made. No estimate was made for antibiotic use benefits in broiler progeny production.

Results

Indonesian case study

A Cobb PS programme with 800K PS was having problems with respiratory disease despite using extensive antibiotics and F strain vaccination. No diagnostics were undertaken. The results were dramatic with a cure of clinical signs (perhaps they were having problem with tylosin resistant Mycoplasma (Morrow 2015).

An estimate of the amount of antibiotic used to combat MS infection in Europe.

This accuracy of this estimate is hard to assess but it is a starting point. Over the years of use of these vaccines in Australia the dependence of the poultry industries on routine antibiotics given at therapeutic levels has markedly dropped.

Anecdotally the introduction of MSH in Iran with extensive use in broiler breeders was associated with U$D 1 million [wholesale price] of tylosin (generic) expiring in storage.

Conclusion

The economic benefits of mycoplasma control especially Mycoplasma control in layers needs to be revisited. The effects reported on FCR in the conversion of feed to eggs (Ouchi et al 2009) or saleable chicks need to be confirmed. Indeed studies on this effect from MG infection also are warranted. The reduction in feed costs pays for the vaccination in real time – each feed bill – independent of the market prices realized for products.

With the push for a reduction in antibiotic dependence in poultry production systems live mycoplasma vaccines need to be considered as a tool. These examples show that live mycoplasma vaccination of breeders and layers (in areas of significant challenge) can be expected to reduce the dependence of these industries and perhaps broiler production as well on the dependence of routine antibiotic treatments. The secret is to stop/review use of antibiotics after the introduction of vaccination (and not to combine the vaccination with killed mycoplasma vaccines). MIF needs to be updated to include considering vaccinated breeder flocks as being mycoplasma free for regulatory purposes or a new category (vaccinated).