Control of Coccidiosis in Turkeys
- Global Review -

Peter Gazdzinski DVM, PhD. Dip.Path. Dip. ACPV. Cuddy Farms Inc, Strathroy, Ontario

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Coccidiosis is among the most common diseases in turkeys. Coccidia are species specific enteric parasites, and in turkeys seven Eimeria species have been described although only four are of major concern to the turkey industry: E.adenoides, E. meleagrimitis, E.gallopavonis and E. dispersa. Of these, the first two are the most significant and most common pathogens.

Transmission of coccidiosis is by fecal material and there are no intermediate hosts. The clinical signs are not very specific and they are the same as we see with many other diseases: lethargy, anorexia, diarrhea, ruffled feathers and huddling. It is considerably more difficult to diagnose subclinical coccidiosis in turkeys than in chickens, since there is a lack of discrete lesions in turkeys. The peak of shedding of oocysts occurs between 3-6 weeks. Fortunately, coccidia are very immunogenic and most treatment programs and vaccines rely on the immune response to control the disease. There is probably no age resistance as described by some authors but rather immunity as a result of some exposure.

Current approaches to coccidiosis prevention in turkeys include:

1. Chemotherapy with anticoccidials.
2. Vaccination with live oocysts.

At the present time, anticoccidials are still the main measure of prophylaxis in Europe and North America. However, vaccination is used more and more often. In Ontario, approximately 35% of all produced turkeys are vaccinated.

Chemotherapy

The number of anticoccidials available for turkeys is very limited. Some anticoccidials used in chickens can create severe toxicity in turkeys (f.e.salinomycin). Intoxication with salinomycin leads to high mortality on the order of 28%- 46%. Narasin is also toxic for turkeys. There are also reports that monensin can lead, in certain circumstances, to toxic effects and this is so called "knock-down" syndrome. The frequency of occurrence of "knock-down" is higher in the summer and early fall. Other aspects of anticoccidials are incompatibilities between therapeutics and coccidiostats such as sulfonamides and ionophores.

The list of commonly used anticoccidials is enclosed in the table below. They can be divided into two groups: Ionophores and Chemicals. All drugs used for coccidiosis control are unique in the mode of action. A drug may be efficacious against one or several species and very few are equally efficacious against all. The ionophores which include Monensin, Lasalocid and Maduramicine cause upset of the osmotic balance of the protozoan cell by changing the permeability of cell membranes for some cations. The ionophore anticoccidials seem to be more efficacious for long term application than chemicals. There may be two reasons responsible for this. It has been reported that ionophores, unlike chemical drugs, allow the development of certain number of coccidia, therefore allowing a higher degree of immune response to be induced. Another reason could be that since ionophores cause massive disruption to cell membranes of coccidia, affecting all enzyme systems, it may take much longer for mutations to render the coccidia resistant to disruption to their various systems.

The majority of drugs in North America are used up to 9 or 10 weeks of age. In Europe they are used longer till 12-16 weeks. However, the oocyst excretion can even be up to 20 weeks. There are very little data on resistance of coccidia to the anticoccidials in turkeys. In order to minimize the induction of resistance the rules of thumb are:

1. Do not use products continuously on the same farm,
2. Give the various products a sufficient rest period after each use
3. Rotate between products of different chemical classes
4. Respect the advised concentration in the turkey feed because some can be very toxic to turkeys.

Chemical Group	Active Substance	Brand Name	Minimum Concentration in PPM	Maximum Concentration in PPM	Withdrawal Time in days
Ionophores	Monensin Lasalocid Maduramicin	Coban Avatec Cygro	90 90 5	100 125 5	0 0 5
Benzenacetonitril	Diclazuril	Clinacox	1	1	5
Quinazoline derivative	Halofuginone	Stenrol	2	3	5
Guanidine	Robenidine	Cycostat	30	36	6
Pyridine derivatives	Clopidol	Lerbek	110	110	5
Thiamine analogues	Amprolium	Amprol	66.5	133	0

Vaccination

The use of vaccination for the control of coccidiosis became more common in the last 7 years. There are only 8 anticoccidial drugs effective in turkeys and more than 25 in chickens. The emergence of coccidia resistance to the limited anticoccidials, the susceptibility of turkeys to ionophores toxicity, and public opinion against the use of chemicals and drugs has made the use of vaccines more attractive.

The principle of immunization by exposure to a small number of pathogenic oocysts of important species of coccidia was developed with chickens first and then in turkeys. In North America there are two vaccines available for turkeys: Immucox made by Vetech Laboratories, Guelph Ontario and Coccivac T made by Shering Plough, Animal Health. In spite of the big demand for vaccination in Europe, there is only one vaccine for turkeys Livacox T made in Chech Republic. In some countries like Poland and Denmark Immucox has been registered and used in the last few years.

Immucox vaccine has been successfully used in North America in the last 7 years. The majority of this vaccine is used in a gel pack form for poult consumption up to 3 days of life. The gel delivery system replaced the liquid application via drinking water which is more labor intensive. Immucox vaccine contains the species of E.adenoides and E.meleagrimitis. Coccivac T vaccine has been introduced last year in the USA and Canada. It is administered in the hatchery by spray cabinet. The vaccine contains four species: coccidia E. adenoids, E.meleagrimitis, E.gallopavonis and E.dispersa.

Vaccination is a controlled exposure of poults to defined numbers of oocysts. All poults must receive an adequate number of oocysts of each of pathogenic species to provide protective immunity to the oocysts that will be picked up from the litter. Birds develop immunity after two or three cycles of coccidia. The first cycle is from the vaccine and the second and third from a lifter. It is important that they don't pick up excessive numbers of oocysts from the litter when immunity is not fully developed. Practically, after 2 or 3 weeks the immunity should be fully developed. The immunity after vaccination is based on cellular immunity.

Performance of vaccinated birds will be discussed. In general in many trials performance of turkeys vaccinated with Immucox was the same or better compared to anticoccidials. Viewing the trends of limited use of anticoccidial drugs, vaccination against coccidiosis seems to have a good future. New methods of their administration may improve efficacy and eliminate side effects.

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Copyright © 2007, Vetech Laboratories Inc.