CONTROL OF COCCIDIOSIS IN POULTRY : Strategies to Control Coccidiosis in Poultry
Coccidiosis, caused by various Eimeria species, is one of the most economically devastating infectious diseases of poultry, raisedunderdeep litter system.It occurs mainly in caecaland intestinal systems, and results in high morbidity and mortality.The coccidia consists of a wide variety of single-celledparasitic animals in the sub-kingdom Protozoa. As a group, thecoccidia of the genus Eimeria are predominatelyhost-specific, i.e., each species occurs in a single host. Worldwide, the poultry industry spends significant amount of money in prevention and treatment of coccidiosis, which causes substantial economic losses due to malabsorption, bad feed conversion rate, reduced weight gain and increased mortality.
Globally, the poultry industry spends significant money in the prevention and treatment of several poultry diseases. One of these diseases, avian coccidiosis, is caused by protozoan parasites of the genus Eimeria, developing within the intestine of most domestic and wild animals and birds. This parasite invades epithelial tissues of the intestine causing severe hemorrhagic enteritis in birds and as a result, significant economic losses. Seven species of Eimeria (E. acervulina, E. brunetti, E. maxima, E. mitis, E. necatrix, E. praecox and E. tenella) are recognized as infecting chickens. Although coccidiosis is a disease known for many years, it is still considered as the most economical important parasitic disease affecting poultry production worldwide. Coccidial oocysts are extremely resistant to environmental conditions and disinfectants. The use of several drugs, solely or in combination, has proven to be an effective alternative method in the struggle against avian coccidiosis. However, the emergence of drug resistant strains, especially after a prolonged use of a drug is a real problem. Thus, vaccines are the only preventative methods. Due to this, new alternative methods have emerged most of which are natural compounds extracted from plants or produced by microbes. Some of these compounds are antioxidants that damage the parasite, thus preventing the infection. Hence, eradication of coccidiosis from chicken houses mere by litter removal, cleaning and disinfection is not possible.
There are two types of coccidiosis:
- Clinical coccidiosis in which the affected birds show classical symptoms of the disease such as bloody droppings and increased mortality and
• Subclinical coccidiosis, since the affected birds do not show visible symptoms of the disease but when a random sample of birds is examined, the presence of the gross lesions and the coccidia are found. For many years coccidiosis prevention and control relied on the use of synthetic anticoccidials, commonly referred to as chemicals. In many cases, resistance to these drugs quickly occurred – within 1 to 3 years – and they became ineffective. Of this group, only Nicarbazin and Totrazauril remains effective today.
ETIOLOGY
Parasites causing coccidiosis are commonly found in places where chickens are raised. Coccidia can multiply rapidly inside the cell lining of intestine or caeca. Many species of Eimeria genus can infect poultry with no cross-immunity between them. Eimeria have a self-limiting life cycle and are characterized by high tissue and host specificity. They show a wide variation in their pathogenicityas shown in Table-1.
Table-1: Characteristics of important Eimeria spp. infecting chickens
| Host | Eimeria | Location | Pathogenicity* |
| Chickens | E. acervuline | Duodenum, Jejunum | ++ |
| E. brunetti | Ileum, Rectum | +++ | |
| E. maxima | Duodenum, Jejunum, Ileum | ++ | |
| E. mitis | Duodenum, Jejunum | + | |
| E. necatrix | Jejunum, Caeca | +++ | |
| E. praecox | Duodenum, Jejunum | + | |
| E. tenella | Caeca | +++ | |
| * – non-pathogenic; + low pathogenic; ++ moderately pathogenic; +++ highly pathogenic | |||
TRANSMISSION
Wild birds, insects or rodents spread sporulated oocysts mechanically via contaminated boots, clothing, equipment or dust.The natural route of infection is by direct oral transmission. Following the ingestion of sporulated oocysts, the microenvironment of host digestive tract stimulates excystation of oocyst in gizzard resulting in the release of sporozoites that invade and destroy cells in intestinal mucosa and begin the reproductive cell cycle as seen in Fig-1.
Fig-1: Reproductive cycle of the sporulated oocyst.
DIAGNOSIS
- CLINICAL SIGNS
Young birds are more susceptible to Eimeria species involved to cause coccidiosis than older, as the Eimeria lifecycle varies from 4-7 days. The severity of an infection depends on the age of birds, number of sporulated oocysts ingested, immune status of flock and environmental management. Infected birds frequently display a typical ‘sick bird’ attitude with depression, prostration, tend to huddle together, have ruffled feathers, consume less feed and water, soiled vents, and the droppings are watery to whitish or bloody.
- LESIONS
- acervulinalesions have a unique appearance, consisting of white patches or transverse white lines inside the gut that may be observed from outside. The lesions of maximaresults in multiple petechial haemorrhages,noted segmental ballooning or enlargement of mid-gut area with the presence of orange-tainted mucous. Gross lesions of E. tenellaare confined to caeca with the presence of haemorrhagesaround the wall of caeca;freeblood or chocolate-coloured fluid content inside caeca, thickening of caecal wall, and large core of cellular debris and blood.E.praecox and E. mitis are considered nonpathogenic or low pathogenic and experimental infections with these species may produce pathogenesis resulting in enteritis, diarrhea and reduced feed efficiencies.
- acervulinalesions maximalesions E. tenellalesions
Fig-2: Gross lesions of Eimeria species.
- LABORATORY TECHNIQUE
Coccidiosis is often diagnosed by counting coccidia per gram of faeces and by microscopic examination of oocyst. The rRNA and rDNA probes were used for identifying individual species through characteristic restriction fragment patterns, randomly amplifying polymorphic DNA assay to differentiate E. acervulina, E. tenella and their strains.
PREVENTION
POULTRY HOUSE MANAGEMENT
In USA, removal of caked litter and aeration of poultry houses at an interval of 2–3 weeks is practiced and top dressing with fresh litter before placing a new flock is a rule. On the other hand, a thorough cleanout between flocks is a common practice in most European countries and Canada. Strict biocontrol measures adopted by caretakers of poultry houses can play a great role in restricting the spread of infective oocysts.
PROPHYLACTIC APPLICATION OF ANTICOCCIDIALS
Now a day’s prevention and control of coccidiosis is dependent upon the proper usage of anticoccidial drugs or vaccines with proper cleaning and disinfection of farms along with better farm management practices. Eradication of coccidiosis by litter cleaning and disinfections is not feasiblein poultry farms because of the resistant capacity of coccidial oocysts to environmental conditions and some disinfectants.Hence, usage of various anticoccidials like ionophores or chemicals is necessary to avoid the losses due to coccidiosis outbreaks. Addition of starter and grower feed is referred as a straight program. The concentration of ionophore may be increased in grower feed for maximum protection at time of peak coccidian oocyst shedding (3-4 weeks) during straight program, which is referred as step-up program.Whereas, the decreased anticoccidial concentration in grower or finisher feed is referred as step-down program. The addition of chemical and ionophore anticoccidial in starter and grower feed respectively is referred as shuttle program. These practices minimize the risk of anticoccidial molecule resistance because time of exposure to same drug is limited. These rotation of anticoccidials involves the changing of the product every 4-6 month by giving proper rest to each category of anticoccidial molecules.
VACCINES
Live vaccines are commonly used in summer season because live vaccines containlive non-attenuated coccidian which induce some lesions, stimulate active immunity and predispose birds to necrotic enteritis. Broiler breeders are vaccinated twice intramuscularly during brooding growing phase which will help to pass maternal antibodies to their offspring and immunity to infection that has been demonstrated with E. acervulina, E. maxima, E. mitis and E. tenella.Developed countries like United States and Canada use vaccines like recombinant vaccines or live vaccines likelivacox (consisting of precocious and egg-passaged lines), coccivacandimmucox which contains several virulent coccidia species.
NATURAL ALTERNATIVES TO PREVENT COCCIDIOSIS
Recently use of natural products like fungal extracts, plant extracts and probiotics to reduce problems caused by coccidiosis has improved.Varying effects of some diet supplements include immune stimulation, anti-inflammatory effect, antioxidant activity and cytoplasmic damage.
FATS
Sources of fat containing docosahexaenoic acid, eicosapentaenoic acid and linolenic acid (known as n-3 fatty acids) in high concentrations from fish oils or flax seeds was observed to reduce the severity of Eimeria tenella infection in young broiler chicks. Diets supplemented with 2.5 to 10% fish oil, 10% flax seed oil, or 10% linseed oil significantly decreased cecal lesions, reduced parasitic invasion rate and development.
ANTIOXIDANTS
Antioxidant molecules plays an important role to control and reduce oxidative stress caused by increased levels of reactive oxygen species and free radicals. This can initiate chain reactions in the cell, resulting in the death or serious damage to cell. Usage of antioxidants from natural sources can restore balance of oxidants/antioxidants which helps to recover the coccidiosis affected birds. Curcumin extracted from Curcuma longa, may be useful to reduce the lesions caused by E. acervulina and E. maxima in upper and middle part of small intestine.An extract from Artemisia annua, Artemisinin,is useful in reducing oocyst shedding of E. acervulina and E. tenellathan E. maxima infections.
ESSENTIAL OILS
Addition of essential oils in the formulations or diets of poultry to control coccidiosis has been practiced recently. It was reported that in vitro destruction of Eimeria oocysts after a three-hour contact period was observed with addition of essential oils from artemisia, thyme and tea tree.Eimeria oocystsare destroyed by essential oils extracted from artemisia, thyme, tea tree and clove.
HERBAL EXTRACTS AND MEDICINAL PLANTS
Some plant extract has anticoccidial effects.The effect of 15 different herbs were assessed and found thatUlmusmacrocarpa, Pulsatillakoreana, Torilis japonica, Artemisia asiatica and Sophoraflavescens have shown higher survival rates in day old infected broilers with E. tenella,than those of the infected control.
IMMUNE RESPONSE MODULATORS
Diet with lyophilized powder of plums extract in chickens reported an increased body weight gain, reduced fecal oocyst shedding rate and an increased mRNA’s for IFN-γ and IL-15, greater spleen cell proliferation and enhanced immune responses.Recently, trend of probiotics and prebiotics usage as an alternative for antibiotics has increased. Use of these products had shown to control the establishment of pathogens in intestinal tract of chicken, which not only helped to improve the body weight gain and reduced feed conversion ratio but also livability and immunomodulation of chicken. A study showed that the commercial probiotics contacting Pediococcusacidilactici and Saccharomyces boulardii acts as prophylactic drug alternative for controlling coccidiosis. Diet containing Lactobacillishowed immunomodulatory effect by stimulating gut associated bacteria in neonatal chicks, which protect chickens from disease without any effect on growth performance, and can also be used as a possible replacement for antibiotics.
TREATMENTAND SUGGESTIONS
- Drugs which are effective to control the coccidiosis outbreaks are preferred.
- Sulfa trimethoprim,tolrazuril or sodium sulfachloropyrazinemonohydrate,amproliun with vitamin K,sulfadimethoxine or sulfamethazine (sulfadimidine) are generally used to control the coccidiosis outbreaks.
- Proper water lines flushing to be done to ensure that it does not contains residues of drugs and supplements given through water (vitamins, electrolytes, etc.,).
- Sulphonamides are more stable and effective at neutral to alkaline water pH.
- The required withdrawal periods vary between sulphonamides, which must be taken care during treatment.
- Be awareof label directions and withdrawal periods to ensure efficacy and avoid tissue residues.
- Choosing proper anticoccidial molecules through feed by following golden rules of anticoccidial rotation must be implemented by giving sufficient rest to each molecule, which will minimize coccidiosis outbreaks throughout year.
Strategies to control coccidiosis in poultry
1.A major breakthrough in the prevention of coccidiosis through feed medication occurred in 1972, with the launch of the first polyether ionophore anticoccidial, monensin. This type of anticoccidial agents have been commonly referred to as ionophores, a term derived from their general chemical structure. They are the most widely used drugs for coccidiosis prevention in broilers. Each has a different mechanism of action and so no chances of significant resistance have developed. Monensin, for example, is still used successfully more than 35 years after its introduction.
The following are the different types of control programs developed over the years.
a) Straight Program: In this program, the same ionophore anticoccidial is used in chicks and grower stage. Commonly used in spring and summer. Straight program further categorized in step – up program where the concentration of the anticoccidial may be increased in the grower feed to provide maximum protection at the time of peak coccidial oocyst shedding (3 – 4 weeks) and when the concentration of the anticoccidial may be decreased in the grower or finisher feed, this is known as a step – down program
b) Shuttle Program: In this type of preventive program, a chemical anticoccidial is used with the phase –I starter feed and an ionophore anticoccidial with the phase –II grower feed. For example, Diclazauril (Chemical compound) used in 0-2 weeks of phase-I and Madhuramycin (Ionophore anticoccidial) added in 3-4 weeks in commercial broiler feeds. These minimize anticoccidial resistance because the time of exposure to the same drug is limited.
Other examples of shuttle program for prevention of coccidiosis:
Monensin : Halofuginone: Diclazuril (an ideal winter program)
Salinomycin : Lasalocid – ideal for summer program
Salinomycin : Halofuginone – winter or summer program
Salinomycin : Diclazuril – winter or summer shuttle
c) Rotation program: In this program, one chemical type of coccidiostat used for certain period and then rotated or replaced with other ionophore coccidiostat for the similar period. Rotation of drugs may improve productivity. This is because the new drug will be effective against the buildup of coccidia that had reduced sensitivity against the previous product that had been used for a long time.
An example of a rotation program (change every 4 months) would be:
• 1st rotation (May-August) – ionophore i.e. Monensin
• 2nd rotation (September-December) – non-ionophore i.e. Diclazuril
• 3rd rotation (January-April) – shuttle Monensin: Halofuginone
- By Vaccination The second method for the prevention and control of coccidiosis in broiler chickens is through the use of live nonattenuated coccidiosis vaccines. For many years, the use of live coccidiosis vaccines was restricted to broiler breeder replacements. Coccidiosis vaccines usually contain small numbers of a mixture of important Eimeria species such as E. acervulina, E. maxima and E. tenella that parasitize the duodenum, mid-intestine and ceca of the digestive tract, respectively. The introduction of better and more practical vaccination techniques, e.g. the administration by coarsespray or gel-spray cabinet at the hatchery, has resulted in more uniform administration and better protective immunity. Use of coccidiosis vaccines has increased in broiler chickens but this remains a relatively minor use compared to anticoccidial drugs in the feed. New method of administration of live coccidiosis vaccines like the in-ovo injection method into embryonated chicken eggs at 18 days of incubation, which allows precise individual dosing and the early development of immunity. When live vaccines are used, their use is primarily limited to the summer, because the current vaccines contain live non-attenuated coccidia and since they induce immunity in the bird by cycling through it, the vaccines induce some lesions. These lesions stimulate active immunity but they also predispose the bird to necrotic enteritis, a fatal disease caused by Clostridium perfringens. So it is always suggested for using an antibiotic growth promoter in the feed with strongest anti-clostridial activity (such as virginamycin) when live coccidiosis vaccines are used. Another important factor to consider when live coccidiosis vaccines are used is the amount of moisture of the litter. Very dry litter is undesirable because it slows down the development of protective immunity against coccidiosis in vaccinated birds. 3. The moisture and pH of the litter should be always within the standard range. The coccidial oocyst will survive well in acidic pH and litter moisture more than 25%. The sprinkle of common salt @ 2gm / sq.ft in floor litter material will reduce the moisture and also increases the pH 4. Keep the litter dry by frequent turning of litter to reduce the sporulation of the oocysts and reduce the stock density for the reduction in contribution of moisture build up by bird faeces.
Compiled & Shared by- Team, LITD (Livestock Institute of Training & Development)
Image-Courtesy-Google
Reference-On Request.
