Poultry Coccidiosis: A Continuous Economic Threat to Poultry Industry
Coccidiosis is of universal significance in poultry production causing devastating losses due to a large number of birds per flock and high stock densities. The economic impacts of coccidiosis are: decreased profit caused by higher feed conversion, growth depression, increased mortality and the costs of prevention or treatment. Worldwide the annual costs inflicted by coccidiosis to commercial poultry have been estimated at € 2 billion.
Poultry industry is a leading profitable sector in livestock farming in India with high growth rate and huge potential in future to feed the ever increasing population. Coccidiosis is an important disease of poultry which badly compromises the production and affects the poultry producer’s income. It is an apicomplexan protozoan parasitic disease, widely prevalent in our country as well as throughout the world and the poultry farmers are well exposed to it because of its frequent occurrence. The broiler chicks are more prone to the disease in comparison to layers or breeders mainly because of the rearing system adopted. Chemoprophylaxis is widely practiced throughout the country by including anticoccidial feed additives in chick ration. Still, complete inhibition of its occurrence cannot be materialized because of the high biotic potential, sturdy infective stages, short prepatent period and ease of the parasite’s survival and transmission. Here, sound management and hygienic practices complimented with farmer’s awareness can play a pivotal role in early parasite detection, reduced transmission, lesser mortality and ultimately decreased potential economic losses to be caused by the disease. Keywords: Poultry, Coccidiosis, Eimeria, parasitic disease, economic losses.
INTRODUCTION
The poultry sector in India has been transformed over decades from unorganized backyard activity into organized commercial activity where commercial sector shares about 80% of the poultry market. It is one of the fastest growing subsectors of animal husbandry with present growth rate of around 6-7% for layer and 8-10% for broiler industry (Vision 2050, ICAR-DPR). Globally, India is ranked 3rd in egg and 5th in meat production with per capita availability of 54 poultry eggs and 2.36 kilograms per annum poultry meat which is much lower than ICMR’s recommended requirement of 180 eggs and 10.8 kg meat per annum (Vision 2050, ICAR-DPR). However, poultry products have a potential to meet the increasing demand of low cost, safe and healthy animal food/ protein for the growing population, there are many serious threats on its sustainability.
Among all the health threats, coccidiosis is economically one of the most significant disease of poultry industry worldwide. It is an old yet well recognized protozoan parasitic disease in its clinical form but remained under-estimated and underrecognized in its sub-clinical form. The clinical coccidiosis is recognized by prominent signs of mortality, morbidity, diarrhoea or bloody faeces but the sub-clinical form is manifested mainly by poor weight gain and reduced efficiency of feed conversion and is economically more detrimental. Although the disease is self limiting and is largely controlled by good management and hygienic practices, still the increasing drug resistance in the coccidian parasite, the increasing consumer’s preference for animal/bird products raised under no-antibiotic-ever (NAE) system and the ability of coccidiosis-causing parasites to survive the environmental challenges has insisted the poultry producers to revise their coccidiosis control programmes time and again. This article is an attempt to provide all the essential information about poultry coccidiosis and to highlight the disease related concerns which threaten the secure production of poultry-derived food products. Although, the word poultry includes a wide range of domesticated birds including chicken, turkey, geese, ducks etc., but in this article, as coccidian species are host specific and those affecting chicken are most detrimental and also the chicken contributes more than 85% of the poultry industry products, so the word “poultry coccidiosis” here focuses mainly on the disease in chicken.
Economic impact of poultry coccidiosis
Cause of poultry coccidiosis Chicken coccidiosis is caused by prozoan parasites of phylum Apicomplexa and seven species from the genus Eimeria: E. acervulina, E. brunetti, E, maxima, E. mitis, E. necatrix, E. praecox and/or E. tenella. The age group of chicken mostly affected by these species, their location in intestine and severity of their pathogenicity are tabulated in Table 1. The previously recognized two more species, namely E. mivati and E. hagani are not considered as valid species now. Apart from this, two more coccidial species, Cryptosporidium tyzzeri and Wenyonella gallinae are also present in chicken but are nonpathogenic. Generally mixed infections are present in outbreaks where a mixture of two or more Eimeria spp. is present in the infections.
General Life cycle of poultry coccidia:
There are two main phases in the life cycle of Eimeria spp. (Figure 1); one phase occurs outside the host (in environment) called sporogony involving the development of the infective stages (oocysts), and the major phase which occurs within the host and involves massive asexual multiplication (schizogony) and sexual reproduction (gametogony and syngamy). The life cycle starts as the oocyst, or microscopic egg, is passed through the infected chicken’s droppings. The oocyst develops to become infective (sporulate) in wet, humid conditions, easily provided around feeders and waterers, especially if these areas are not cleaned and maintained properly. If proper hygienic practices are not followed then these infective oocysts can also be spread from infected farm to uninfected farms unknowingly by clothings, shoes etc. of farm workers/visitors or equipments, such as shovels or pails etc. Birds become infected by ingesting oocysts either through feed/ water or scratching the ground. The number of oocysts ingested and the immune status of the host bird decides the severity of clinical signs. Young chickens (under six months of age) are most susceptible to the disease due to the lack of development of natural immunity. The oocyst then hatches inside chicken and invades the cell lining of thechicken’s small intestine. It multiplies in different parts of intestine depending upon the species infecting the bird (Figure 2). Here it multiplies rapidly through a number of cycles, rupturs the bowel cells and ultimately release large number of oocysts in the droppings. These oocysts after sporulation again are capable of infecting other birds in the surroundings. The prepatent period of disease is 4-8 days depending upon the Eimeria spp.
Factors affecting the disease epidemiology:
There are many factors which facilitate the disease transmission, predispose the birds to coccidiosis or affect the severity of disease pathology. These factors ultimately affect the disease epidemiology and should be taken into account by poultry producers in order to face least losses due to the disease. These are: 1. Parasite related factors: The severity of the disease depends on both the species of Eimeria and the size of the infecting dose of oocysts. High biotic potential and short prepatent period of parasite rapidly increase the infecting oocysts and thus helps the disease to spread like a wild fire. 2. Host related factors: The disease occurrence is affected by age of the bird, flock density, whether the birds are getting infection for the first time, number of passages or ability of the bird to develop proper specific immune response. Coccidiosis generally affects young birds between 3 to 18 weeks of age, but may occurs at any age. If the infecting dose is small then usually birds acquire immunity without the occurrence of clinical disease, followed by reduced oocyst shedding. Thus, adult birds are usually carriers of oocysts which can severely infect the susceptible young birds. 3. Management related factors: Wet litter, contaminated drinkers and feeders, bad ventilation, high stocking density, same laborer for all the pens or any stress causing factor (transport, debeaking etc.) will predispose the birds to coccidiosis or will increase the severity of clinical signs. Proper management practices play a pivotal role in disease epidemiology as it is almost impossible to raise coccidiafree poultry, but we can prevent its spread by maintaining proper hygiene. 4. Nutritional factors: Chicken usually fed on wheat based diets are more adversely affected than those fed on maize based diet, as higher amount of soluble non-starch polysaccharides in wheat increases the digesta viscosity. Diets higher in crude proteins may also increase the coccidial pathogenicity due to increased tryptic activity which leads to more efficient oocyst excystation. 5. Others: Immunosupressive diseases such as viral diseases of poultry (MD, IBD) or stressful conditions also make them more susceptible to coccidiosis. Presence of mycotoxins in poultry feed, even at permitted levels, may also aggravate the incidence and severity of coccidiosis by facilitating parasite colonization in the gut. Coarse feed particles, mycotoxins etc. may disrupt the intestinal cells whichfurther can be used as a growth substrate for pathogens such as Eimeria, Clostridium and Escherischia coli.
Clinical signs
Clinical signs of coccidiosis depend upon the Eimeria species affecting the bird, number of oocysts ingested at a time, age and immune status of bird and management sytem. If large numbers of oocyst of more pathogenic species are ingested by young birds which are reared in intensive system and deep litter system then the clinical signs will be most prominent leading to clinical form of disease. Otherwise, subclinical forms persist which may go unnoticed by poultry producers. In clinical forms, often yellow diarrhoea is the first and foremost symptom and affected birds display a characteristic posture as they hunch up, fluff up and can drop their wings. They may have diarrhea having soft mucoid faeces or bloody droppings, pink intestinal tissue in droppings, depression, weakness and listlessness, loss of appetite or even interest in water, pale comb or skin, weight loss (in older chickens), decreased growth rate (in young chickens), failure to lay eggs or laying eggs inconsistently and high rate of mortality may be seen in severe cases. Not all chickens will display the same symptoms and all of these symptoms might not be present in all the affected chickens.
Diagnosis of coccidiosis
The best way to diagnose coccidiosis is post mortem examination of affected birds as soon as possible. The location of parasitic lesions in intestinal tract and the type of lesions as given in Figure 2 and Table 1 and will be indicative of Eimeria spp. which will further be confirmed by oocyst finding in intestinal scrapings/ droppings and histopathology.
Breifly, oocysts with lesions in the caeca are E. tenella, in duodenum are E. acervulina or E. praecox, in mid intestine are E. necatrix or E. maxima and oocysts with lesions in the lower gut are E. mitis or E. brunetti. Many times the gross lesions are pathognomonic for species, like caecal plug/caecal core for E. tenella, salt and pepper like lesion with ballooning of mid intestine for E. necatrix, salmon coloured flecks or rice bran like mucosal contents in E. brunetti and ladder like transverse bands on serosal and mucosal surface in E. acervulina. Apart from this histopathology of intestinal tissue gives clear cut picture. Microscopic identification of oocysts after sporulation can also be helpful which require technical expertise. For this, computational analysis of microscopic images of oocysts is also possible now by a software called COCCIMORPH and molecular techniques like PCR involving ITS-1 and ITS-2 gene sequence are also used. Examination of feacal sample for oocysts may give false interpretation of disease pathogenicity, as existence of large number of oocysts may not necessarily indicate a severe pathogenic condition. Among various coccidian oocysts, species identification can be possible only after sporulation and that again is not easy.
Treatment
Early treatment is very important because coccidia must be killed within the bird before irreparable damage is done to the intestines and birds may die within a couple of days in severe cases. Anticoccidial drugs are of two types– coccidiostats and coccidiocides. Coccidicidal (cidal) medications kill the parasite but coccidiostatic (static) do not kill the parasites, but arrest their development irreversibly. Coccidiostats are given in the feed mostly to prevent the disease. For therapeutic purpose, coccidiocides likes sulphaquin® (Sulphaquinoxaline), Coccivet® (Amprolium, Ethopabate) and Baycox® (Toltrazuril) are given usually in drinking water to kill the parasite. A combination of amprolium and sulphaquinoxaline @ 1g/L of drinking water for 2 days, then 2 days gap and repeat of same drug @ 0.5 g/L for next 2 days is also considered as standard chemotherapy (Bera et al., 2010). Generally, coccidiocides dose rates are carefully balanced to kill enough of the coccidia to save the bird, yet still enable immunity to develop. In treating for coccidiosis more is not better as overdosing can be toxic to birds. Supplementary vitamin treatment (especially A and K) is also helpful.
PREVENTION AND CONTROL
a) Chemoprophylaxis: Prophylaxis of coccidiosis is more helpful than treatment as the parasite causes maximum damage before the clinical signs become apparent and severely affected birds remain unproductive even after successful treatment. Disease prevention can be done by means of chemoprophylaxis, immunization by vaccination, sound hygienic and management practices etc. In India, commercial broilers are mostly raised in deep litter system and critically require the prophylaxis while commercial layer, broiler and layer breeders are maintained mainly in the cage system for which prophylaxis is barely required. Chemoprophylaxis by using coccidiostatic drugs like maduramycin, diclazuril, salinomycin are in generally practiced by mixing in feed from day old to 16 weeks of age of birds. An effective coccidiostat will always inhibit the schizogonic stage and in turn develops immunity. But continuous use of these anticoccidials has lead to a further problem of drug resistance and drug residues in consumable meat and eggs. To combat drug resistance, shuttle and rotation systems of drugs are employed but still they can minimize resistance development, not fully prevent it. The different drugs are used during a period of juvenile growth to market size growth in shuttle programme, whereas the type of drug used is switched after one or several grow-out periods or seasonally in rotation programme. Alternative control measures are as follows:
b) Vaccination: Immunization by vaccination utilizes the concept that, mostly birds acquire infection in the first few weeks of life which induces a species specific good immunity. Immunity is best engendered by repeated exposure to low numbers of oocysts, so-called ‘trickle’ infection, and this is what usually takes place naturally. Initially live unattenuated vaccines (Coccivac, Advent, Immucox, and Inovocox) were used, but now their use is limited due to the risk induced by the live parasites and also they were recommended to be used along with chemical treatments to control the inherent pathogenicity of the parasites. But now live attenuated vaccines (Livacox, Paracox and HatchPak CocciIII) are more popular as there is a lower risk of disease occurring because there is a reduction in the proliferation of the parasites and as a result less damage to the intestine of the bird. Today, attenuation of Eimeria species is mostly based on “precociousness” where attenuated virulence is achieved by repeated passaging and collection of first shed oocysts are used for next infection resulting into a population of parasites that complete their life cycle up to 30 h faster thanparasites from the same parent strain indicating a significant reduction in their reproductive capacity and thus pathogenicity. In India, mostly Livacox Q, a live attenuated vaccine containing mixture of most pathogenic species like Eimeria tenella, E. acervulina, E. maxima and E. necatrix species is used in some of the breeder farms where cost of each dose was calculated as Rs 4.00 by Bera et al. (2010) and may be slightly increased today. Coccidia vaccination is not practiced commonly for commercial layers. Recently, a subunit vaccine, CoxAbic is also formulated and is used in some countries.
c) Sound management for coccidiosis control: Apart from chemoprophylaxis and vaccination, several management and hygienic practices should be followed, this includes:
1. To raise chicks on clean dry litter and avoid crowded or damp conditions. Litter should always be kept dry and special care and attention should be given to litter in which the farms located near water bodies.
2. To make sure drinkers are not spilling water into the litter. If possible, provide poultry nipple waterers, rather than open watering areas.
3. To make sure water and feed is uncontaminated by droppings.
4. To use medicated chick starter or grower.
5. To ensure that chicks are warmly housed out of draughts.
6. New birds should be quarantined first, before introducing them into your flock as inspite of appearing healthy; they can be carriers of a number of deadly diseases including coccidiosis.
7. Raise chicks in isolation from mature or adult birds.
8. Do not allow wild birds or insects to come in contact with your birds.
9. Thoroughly clean and disinfect the brooder between broods. This includes any equipment the chicks will come in contact with. Once the premises are dry, place four to six inches of dry, fresh litter material (wood shavings or a commercial absorbent litter material) on the floor.
10. In severe cases, to raise chicks on a wire grill that can reduce ingestion of the oocysts and help recovery.
11. In severe cases, to reduce the protein level in the feed and to prefer maize based feed upon wheat based.
12. To monitor droppings during and after treatment. Often morning droppings can show blood, even if the day is normal. Putting newspaper under perches or on brooder floors can make the droppings easier to see.
13. Sunlight is a natural disinfectant. Incorporate as much natural sunlight into your brooder as possible.
14. Do not wear the same clothing or shoes, or use the same tools and equipment with your chickens that have been used for other activities or on a neighboringchicken farm.
15. In order to provide adequate space and ventilation, be sure each chicken has at least four square feet of space inside coops, 10 square feet in chicken runs and 6 square feet of flooring in brooders for week old chicks.
16. Adding probiotic supplements to your chicks’ water can help create the conditions for competitive exclusion – a process where good bacteria compete for the resources of bad bacteria inside the gut. This can reduce the chances of infection with coccidiosis and improve immunity to other infections as well.
CONCLUSION
Poultry coccidiosis is a cosmopolitan parasitic disease with an enormous potential to have the detrimental effect on poultry production. It is considered almost impossible to raise the chicks in a coccidia-free environment. But the occurrence and severity of coccidiosis depend on many factors like the agent, host and management as well as environment related risk factors. Apart from this, early diagnosis made by aware farmers can save them from large economic losses. prevent the farmers Good hygienic measures and management practices are the best ways to prevent and control the disease.
Compiled & Shared by- This paper is a compilation of groupwork provided by the
Team, LITD (Livestock Institute of Training & Development)
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Reference-On Request
Coccidiosis in Poultry
