Poultry Coccidiosis and its Prevention, Control
Coccidiosis is the commonest and most important disease of poultry resulting in great economic losses worldwide. Therefore, the aim of this paper is to review on poultry coccidiosis. It is caused by the intracellular protozoa parasite of Eimeria species in the genus Eimeria. About nine species of Eimeria have been recognized in domesticated chickens, of which Eimeria brunette, Eimeria maxima, Eimeria necatrix, Eimeria tenella are the most pathogenic; Eimeria acervulina, Eimeria mivati are the less pathogenic and Eimeria praecox and Eimeria hagani are the lesser pathogenic. The disease is endemic in most of the tropical and subtropical regions where ecological and management conditions favour an all-year round development and propagation of the causal agent. Clinical signs are associated with tissue destruction from the release of the merozoites and mature oocysts from the mucosal surface during the last generations of merogony and throughout gametogony. Diagnosis of coccidiosis in chicken is best accomplished by postmortem examination of representative number of birds. Prevention of avian coccidiosis is based on a combination of good management and the use of anticoccidial compounds in the feed or water. Coccidiosis is recognized as the parasitic disease that has the greatest economic impact on poultry production. It is also endemic in Ethiopia, causing great economic losses particularly in young birds, in all production systems. Thus, proper treatment and management should be carried out to decrease the impact of coccidiosis on the economy of developing country.
Keywords: Coccidiosis; Chickens; Diagnosis; Eimeria; Prevention
Parasitic diseases have remained the major problem limiting the expansion and profitability of the developing agricultural countries, where skilled husbandry in-puts have not matched the rate of expansion and intensification of poultry holdings [1, 2]. Poultry coccidiosis is one of the most common and economically most important diseases of poultry worldwide [3].
Coccidiosis is caused by the intracellular protozoa parasite of Eimeria species in the genus Eimeria family Eimeridae order Eucoccidiorida and phylum Apicomplexa [4]. Eimeria colonize and infect the intestinal tract of different animals and birds (Haug et al., 2008) and infection with this parasite normally occurs through ingestion of feed or water contaminated with sporulated oocysts [5, 6]. About nine species of Eimeria have been recognized in domesticated chickens, of which Eimeria brunette, Eimeria maxima, Eimeria necatrix, Eimeria tenella are the most pathogenic; Eimeria acervulina, Eimeria mitis, Eimeria mivati are the less pathogenic and Eimeria praecox and Eimeria hagani are the lesser pathogenic [7].
Infections caused by coccidian parasites have had a major economic impact on the commercial broiler industry in the past several decades. It is endemic in most of the tropical and subtropical regions where ecological and management conditions favor an all year-round development and propagation of the causal agent [8]. Poultry coccidiosis is one of these diseases causing significant poultry losses in Ethiopia [9]. Coccidiosis resulting from the pathogenic Eimeria species is usually characterized by dysentery, enteritis, diarrhea, which may be bloody with certain Eimeria species, emaciation, lower feed conversion rate, delayed sexual maturity, drooping wings, poor growth and low production with attendant high mortality and morbidity rates [10].
The most common and pathogenic species that affects the poultry industry globally is the E. tenella with 100% morbidity and a high mortality due to extensive damage of the digestive tracts of chickens [11,12]. Mortality rates are usually high in young chicks, because most of the Eimeria species affects birds between the age of 3 and 18 weeks [13]. The occurrence of clinical coccidiosis is directly related to the number of oocysts ingested by poultry at one time, the pathogenicity of the Eimeria species, the age of the infected chicken and the management system [6].
The most frequent symptoms is at the beginning yellow diarrhea then become depressed, have ruffled feathers, the wings droop and tend to huddle together [14]. High incidence of coccidiosis is usually observed in poultry managed under intensive management system like deep litter due to increased likelihood of high oocysts accumulation in the litters [15]. Furthermore, higher stocking densities have been linked with increased incidence of coccidiosis due to a higher rate of infection and transmission of the coccidian oocysts in dense flocks from one poultry house to another [16].
For the control of coccidiosis in chickens and turkeys, a number of preventive medications have been approved for use world-wide, but reduced sensitivity and resistance are increasingly important as no new anticoccidial compounds are known to be under development [17]. The traditional control of coccidiosis mainly relies on chemoprophylaxis, which appeared to be effective in the last decades. However, the increased occurrence of resistance against routine anti-coccidial drugs has left the poultry industry with a renewed challenge for coccidiosis prevention and control and propelled the search for alternative strategies among which vaccination is of major importance [18]. Therefore, the objective of this paper is to review on poultry coccidiosis.
Avian coccidiosis is an enteric parasitic disease caused by multiple species of the protozoan parasite of the genus Eimeria. Coccidiosis is the commonest and most important disease of poultry resulting in great economic losses worldwide [19].
Among the infectious diseases of poultry, cocccidiosis is the major parasitic disease. Poultry coccidiosis is an economically important disease in chicken caused by the intracellular protozoa parasite of Eimeria species in the genus Eimeria family Eimeridae order Eucoccidiorida and phylum [4]. Seven species of Eimeria (E. acervulina, E. brunetti, E. maxima, E. mitis, E. necatrix, E. praecox and E. tenella) are recognized as infecting chickens as it detailed in Table 1. Although coccidiosis is a disease known for many years, it is still considered as the most economical important parasitic condition affecting poultry production worldwide.
Majority of Eimeria oocysts have ovoid shape. Other characteristics that is useful in species identification includes: zone of intestine parasitized, nature of macroscopic lesions, minimum sporulation time, minimum prepatent period, schizonts size and area in which it develops, location of the parasite within the epithelial cells and cross-immunity trails [21].
The life cycle of all Eimeria species involves two or more generation of an asexual development known as shizogony, followed by a sexual phase formed by gametogony which results in the formation of oocyst [22]. The infective stage, sporulated oocyst, is ingested and the action of mechanical and chemical factors in the gut (bile salt and trypsin) leads to the release of sporocysts and then sporozoites in the duodenal lumen and this stage is described in Figure 1.
The sporozoites invade the mucosa sometimes passing down the whole length of the alimentary tract before doing so. Then follow phases of intracellular growth and asexual multiplication with periodic release of merozoites entering in to the sexual phase of the life cycle known as gametogenesis [23]. These merozoites invade cells and develop in to either macro- gametes or micro- gametes. The former gives rise to a single macrogamete whereas the male gametocyte matures and ruptures, releasing seven large number of minute biflagellate micro-gametes. The micro-gametocyte grows to form a micro-gamete. A thickened wall forms around the macro-gamete, forming a zygote when the macro gamete is fertilized by microgamete. This stage is the young or immature oocyst [24].
The disease is endemic in most of the tropical and subtropical regions where ecological and management conditions favour an all-year round development and propagation of the causal agent [8]. The occurrence of different Eimeria species combinations and the intensity of infection vary considerably, both locally and globally [5]. High incidence of coccidiosis is usually observed in poultry managed under intensive management system like deep litter due to increased likelihood of high oocysts accumulation in the litters [13]. In Ethiopia, poultry coccidiosis caused by (E.acervulina, E. necatrix, E. maxima and E. tenella, is endemic in all parts of the country and affects mainly young growing birds [9].
Agent related risk factors of Coccidial infection in poultry: The occurrence of poultry coccidiosis is dependent on both the species of Eimeria and the size of the infecting dose of oocysts. Due to the short prepatent period of the parasite and its high biotic potential, the number of oocysts in the litter rises rapidly [26]. Poultry coccidia have high capacity to reproduce within the host; this leads to high level of the parasite within the susceptible host and subsequently high level of contamination of the environment [27].
Host related risk factors: Coccidiosis is usually a disease of young birds, but birds can be infected at any time, if never exposed before. Coccidia populations take time to build dangerous levels, therefore, outbreaks usually occur when birds are between 3 and 8 weeks of age [25]. High animal density cramped on a small space, age of the bird at the time of the first infection and number of passages of the infection as well as on ability of the bird to develop proper specific immune response [28].
Environmental and management related risk factors: Management of poultry houses plays a momentous function in the spread of coccidiosis because coccidialoocysts are omnipresent and are easily spread in the poultry house environment. Further, owing to their high reproduction potential, it is very complex to keep chickens coccidia free, especially under current intensive rearing [29]. Prevalence varied by management and did not vary by flock size while bad management, such as wet litter that encourages oocyst sporulation, contaminated drinkers and feeders, bad ventilation, and high stocking density, can worsen the clinical signs [12, 30].
Infection by coccidia in sufficient number to produce clinical manifestations of disease is called coccidiosis [31]. Though nine species of Eimeria have been identified as causative agents of poultry coccidiosis, only seven of them have been reported to be pathogenic [32]. Emeria tenella (E. tenella) and Emeria necatrix (E. necatrix) are the most pathogenic species. Emeria arcevulina (E.acervulina), Emeria maxima (E. maxima) and Emeria mivati (E. mivati) are common and slightly too moderately pathogenic while Emeriabrunetti (E. brunetti) is uncommon but pathogenic when it does occur. Emeria praecox (E. praecox) and Emeria hagani (E. hagani) are relatively non-pathogenic species [33].
Oocysts passed in the feces require suitable environmental conditions to sporu late. Moist, temperate, or cool conditions favor sporulation, whereas high tem peratures and dryness impede it [34]. Coccidiosis outbreaks are commonly classified according to the areas of the digestive tract for which the particular species of coccidia seem to have a special affinity. The protozoan parasite of the genus Eimeria multiplies in the intestinal tract and causes tissue damage, resulting in the interruption of feeding, digestive processes, nutrient absorption, dehydration, blood loss, loss of skin pigmentation and increased susceptibility to other disease pathogens [35].
Avian coccidiosis, caused by parasites of the genus Eimeria, produces anorexia and reduced weight gain and feed conversion in infected chicks [36]. Emeria tenella causes moderate to severe cecal lesions, sometimes death. The birds become depressed, have ruffled feathers, the wings droop, have diarrhea and tend to huddle. Food and water consumption usually decreases and may become emaciated and dehydrated. Laying hens will experience a reduction in rate of egg production. Cecal coccidiosis may produce bloody droppings and anemia [37].
Clinical signs are associated with tissue destruction from the release of the merozoites and mature oocysts from the mucosal surface during the last generations of merogony and throughout gametogony. In severe infections, much of the mucosal epithelium is sloughed off and nutrient absorption is compromised [38].
Diagnosis of coccidiosis in chicken is best accomplished by postmortem examination of representative number of birds. Diagnosis by fecal examination may lead to quite erroneous results [33]. In some instances the major pathology is produced before oocysts are shed in the feces (E. tenella) and, conversely, the presence of large number of oocysts may not necessarily indicate a serious pathogenic condition. Thus, with E. acervulina, which has a high biotic potential, comparatively larger numbers of oocysts are shed than, for example, with E. necatrix. Furthermore, the accurate identification of the oocysts of various poultry coccidia is not easy [34].
In recent years, various biochemical and molecular methods have also been [18]. As indicated, next to the fact Eimeriaare very effective parasites, one of the main reasons coccidiosis is still a major problem, is the difficult diagnosis. The classical parasitological methods of diagnosis are labor intensive and therefore costly. Oocyst per gram (OPG) counts in faeces or litters have a poor relation with the impact of the parasite on the performance of a flock. Identification of different species based on morphology of oocysts is very challenging and requires expertise [17].
Diagnosis of clinical disease caused by E. tenella is quite easy and action (therapy on the short term, change of preventive means on the long term) can be swift. These facts make its impact on the productivity of the broiler industry is relatively limited compared to the other species, although many broiler farmers associate coccidiosis only with caecalcoccidiosis. This is a good example of perception not being in accordance with the facts. E.acervulina and E. maxima, both much more prevalent, are less perceived to be related with clinical coccidiosis in the field. E. acervulina is causing white lesions in duodenum and in heavier infections also more caudal, interfering even with the ability for E. maxima to develop [39].
The type and locations of lesions in the gut indicates the species of Eimeria. Eimeria acervulina affects the upper parts of the small intestines, you may see small red spots and white bands on it; E. maxima affect the entire small intestine; the intestine looks watery and in later stages have blood and mucus. The intestine may look thickened and ballooned with red pinpoint lesions. Eimeria tenella affects the blind sacks of the gut. The intestine may be filled with blood and pus and turn in to a solid core [25]. Histopathologically, the wall of the gut is thickened indicating retention of fluid (edema). There may be blood in the lumen of the gut indicating blood loss (hemorrhage), or merely retention of an excessive amount of blood in the tissue (hyperemia) there is also infiltration with various body reactions and the development of immune response [40].
The effective use of anticoccidial feed additives over the past 50 years has played a major role in the growth of the poultry industry and has allowed the increased availability of high quality, affordable poultry products to the consumer. There are basically two means of prevention of coccidiosis: chemoprophylaxis and vaccination. Chemoprophylaxis using so-called anticoccidial products (ACP) or anticoccidials in the ration is by far the most popular [41].
Coccidiosis is by far more easily prevented than treated; Drugs have been very important in controlling coccidiosis but the emergency of coccidial drug resistance has affected the use of fullness of the drugs. The possibility that drugs may not always be relied up on to control coccidiosis has led to an interest in other means of control [42]. Apart from the use of drugs, control is now based on hygiene, vaccine and genetics. But genetics is a theoretical strategy not in practical use [26].
Prevention of avian coccidiosis is based on a combination of good management and the use of anticoccidial compounds in the feed or water. Litter should always be kept dry and special attention should be given to litter near water fonts or feeding troughs [4, 43]. The prophylactic drugs used for prevention of coccidiosis are coccidiosistats. An effective coccidiostat should inhibit the schizogonic stage and allow immunity to develop. Prophylactic use is performed because most of the damage occurs before signs become apparent and because drugs cannot completely stop an outbreak [14].
Coccidiosis is one of diseases of poultry that play inhibitory role in the growth of this industry. It is a disease complex of poultry caused by different species of parasite of Eimeria. It inflicts the birds in both clinical and sub-clinical forms. The clinical form of the disease manifests through prominent signs of mortality, morbidity, diarrhoea or bloody faeces and sub-clinical coccidiosis manifests mainly by poor weight gain and reduced efficiency of feed conversion and gives rise to highest proportion of the total economic losses [44].
The prevalence of poultry coccidiosis has been reported in different part of Ethiopia in different years (Prevalence of Coccidiosis was reported by researcher; Gebremeskel and Tesfa, 2016; Oljira, 2012; Alemayehu, et al. 2012; Feyisa and Chalchisa , 2017) as listed as, 20.57%, 28.2%, 25.5% and 39.6% respectively. The variation of this all prevalence of coccidiosis may be due to epidemiology of study time, breed and management system differences and possibility of drug resistance [45-48].
Coccidiosis is an important enteric parasitic disease of poultry associated with significant economic losses to poultry farmers worldwide. It has been indicated that there are several species of Eimeria affect chickens with varying pathogenicity. The occurrence of coccidiosis dependent on agent, host and management as well as environment associated risk factors. The presence of lesions and part of intestine affected in combination with histo- pathology could help in better diagnosis of coccidiosis. Anticcocidials and good management are important for control and prevention of coccidiosis in domestic chickens.
Therefore, based on above conclusion the following recommendations are forwarded:
➢ Proper diagnostic methods and biosecurity measures should be performed to prevent and control the disease in the chickens.
➢ Proper prophylactics treatment and management should be carried out to decrease the impact of coccidiosis on the economy of developing country.
➢ To control this economically important parasitic disease of poultry, further studies need to be undertaken to come up with sustainable and cost-effective prevention and control methods.
