Prevention and Methods of Controlling Coccidiosis Among Chickens

In the past it has been realized that eradication of coccidia especially among chickens is not realistic and hygienic measures alone are not able to prevent infections. However, if an outbreak of coccidiosis occurs among chickens, treatment via the drinking water should start as soon as possible.

Today the prevention and control of coccidiosis is based on chemotherapy, using anticoccidial drugs and/or vaccines along with hygienic measures and improved farm management.

Anticoccidial (Anti-Coccidiosis) Drugs for Chickens

According to Shirley and Chapman (2005) the most significant study that had the greatest impact on control of coccidiosis was that of Delaplane et al., (1947) which showed that the administration of low concentrations of sulphaquinoxaline in the feed effectively controlled the disease.

The rapid development of the broiler industry in the 1950’s required the urgent availability of anticoccidial drugs. This soon led to intensive activities by several companies to produce a range of chemical products that were effective in the control coccidiosis.

However, the result was that the surviving coccidia quickly became resistant to the products and severe outbreaks of the disease occurred. According to Chapman (1994a) nicarbazin was introduced in 1955 to the USA and was extensively used in broiler production.

In the 1970s several other highly efficacious synthetic drugs were introduced but due to the rapid development of drug resistance, they were withdrawn shortly afterwards. The development of resistance was documented for these anticoccidial chemical drugs (Jeffers, 1974a,b; McDougald et al., 1986). It is likely that resistance has developed to more recent anticoccidial drugs but this has not been investigated and may have gone unrecorded (Chapman, 2005).

A major enhancement in coccidiosis control occurred in the 1970’s with the introduction of monensin as the first ionophore coccidiostat. Introduction of ionophores changed the ability to control coccidiosis, an impact that remains to this day (Shirley and Chapman, 2005). The effectiveness of ionophore coccidiostats lies in the fact that whilst they kill the majority of the invading parasites, they permit a small leakage of coccidia enabling a degree of host immunity to develop.

Resistance to ionophores develops very slowly and there is more of a tendency to increased levels of tolerance. Chapman and Hacker (1994) as well as Mathis (1999) observed a marginal to poor effect of different ionophores to several Eimeria sp.

Since the 1970’s, coccidiostats have been regulated under the Feed Additives Directive 524/70/EEC (EEC, 1970; 2004), which has now been replaced by Regulation No 1831/2003/EC (EC, 2003; 2007). As such, they have not been subject to veterinary prescription status, since they are required routinely in the feed of commercial broilers and turkeys.

Currently several types of anticcocidial drugs are available including synthetic compounds (chemicals), quinal one and certain ionophore antibiotics (Table3). In recent years, however, few new drugs have been introduced.

All types of drug used for coccidiosis control are unique; in their mode of action, the way in which parasites are killed or arrested, and the effects of the drug on the growth and performance of the bird. Very few drugs are equally efficacious against all Eimeria species (McDougald, 2003).

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Table 3. Some anticoccidial drugs used for prevention in chickens and turkeys in the EU.

Zusatzstoffe zur Verhütung der Kokzidiose bei Hühnern und Puten in der EU.

The efficiency of anticoccidial agents can be reduced by drug resistance and management programmes are designed to prevent this developing, which results in better gut health and feed utilization by birds. Using a drug rotation, with constant monitoring of the oocysts in the faeces and in the litter, or shuttle programme (ionophore/chemical) seems to be of great value.

Rotation involves changing the product used every 4–6 months. The alternative to a rotation programme is a continuous program where the same products are used until a problem develops or until a new product is introduced on the market. Rotations are only possible if drugs with different mode of action follow each other. On the other hand, a shuttle programme uses two or more products during the grow-out period of a flock.

The principle is to use the drug most suited to each phase of the grow-out, so that one drug is used for the starter period, whilst another is used during the grower and finisher phase. The drug withdrawal period is a very important consideration for treatments used in finisher feeds (Paeffgen et al., 1988; Smith, 1995). A ‘switch’ system can also be used where the anti-coccidial agent is changed at each restocking within an operation.

A coccidiosis ‘break’ is often an indication of an immunosuppression problem. Concurrent infection with immunosuppressive diseases such as Marek’s disease may interfere with development of immunity to coccidiosis (Biggs et al., 1969) and infectious bursal disease (IBD) may exacerbate coccidiosis, placing a heavier burden on anticoccidial drugs (McDougald et al., 1979).

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Vaccination

The poultry industry is facing problems of drug resistance, a lack of new anticoccidial products, the susceptibility of turkeys to ionophore toxicity and consumer pressure to decrease the use of antibiotics in animal feed. It is therefore being forced to seek alternative strategies to control Coccidiosis, which has made the use of vaccines more attractive.

Although it has been known for many years that the host exposure to low numbers of coccidia oocysts allows the development of a protective immunity, live coccidiosis vaccines weren’t used in poultry until the 1960’s.

There is now a tremendous amount of knowledge about the immune response of chickens to coccidia infections (Lillehoj, 2005) and the development and use of vaccines is increasing.

Several different live vaccines have been commercially developed and they are mostly composed of either virulent or attenuated parasitic strains. Non-attenuated vaccines have been used for many years.

In conclusion, Infections with coccidia are often associated with severe economic losses. Currently the prevention and control of coccidiosis is based on good hygiene, chemotherapy (Coccidiostats) and immunization. Monitoring programmes are essential for the early recognition strains developing resistance.

Generally, anticoccidial drugs or vaccination alone is of little value, unless they are accompanied by improvements in all aspects of management. More attention should be given to improved sanitation and hygiene at the farm level.

Including, all parameters which can improve litter quality such as; appropriate installation and management of watering systems, providing adequate feeding space, maintaining recommended stocking density and supplying adequate ventilation.

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