Claire Thompson
Coccidiosis is a disease caused by the ingestion of infective sporulated oocysts from a contaminated environment. It affects several animals, including poultry, and is characterized by parasite replication in host cells, leading to extensive damage to the intestinal mucosa. While coccidia are almost always present in poultry-raising operations, clinical disease only occurs after the ingestion of a large number of sporulated oocysts by susceptible birds. The protozoan parasite, Eimeria tenella, is one of the most pathogenic in chickens, causing coccidiosis when ingested in the sporulated oocyst stage. However, it is important to note that oocysts passed in the host's feces are not immediately infective and require specific conditions for sporulation. Therefore, it is unlikely to find sporulated oocysts in the chicken cecum, as they are typically passed out in the droppings for a short period following infection.
| Characteristics | Values |
|---|---|
| Sporulated oocysts cause | Coccidiosis |
| Protozoan parasite | Eimeria tenella |
| Oocysts expelled from the host | Uninfectious, unsporulated form |
| Sporulation occurs | Within several days |
| Oocysts have | Thick, resistant shell |
| Oocysts survive best | Between 20 and 25°C |
| Oocysts survive | Over a year |
| Oocysts are resistant to | Some disinfectants |
| Oocysts are killed by | Freezing or high temperatures |
| Oocysts are transmitted via | Equipment, personnel, insects, rodents |
| Oocysts are infective | After 1-2 days |
| Oocysts are identified in feces by | Salt or sugar flotation methods, direct intestinal smears, McMaster counting chamber |
| Oocysts are identified by | Isozyme analysis, rRNA and rDNA probes, DNA assays, recombinant DNA techniques |
| Oocysts are infective | When ingested |
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What You'll Learn
- Sporulated oocysts are not immediately infectious and require moisture, oxygen, and warmth to sporulate
- Oocysts are transmitted via insects, rodents, and equipment, and are resistant to some disinfectants
- Oocysts are released in their non-infectious, unsporulated form through the faeces of the host
- Oocysts are highly resistant to environmental pressures due to their multi-layered cell wall
- Coccidiosis is caused by the ingestion of infective sporulated oocysts from a contaminated environment
Sporulated oocysts are not immediately infectious and require moisture, oxygen, and warmth to sporulate
Oocysts are a type of protozoan parasite that can infect a wide variety of birds, mammals, and reptiles. They are transmitted orally, through ingestion of contaminated food or water, or via equipment, personnel, insects, and rodents. Oocysts are not immediately infectious upon excretion from the host and require specific environmental conditions to become infectious. This process is known as sporulation.
Sporulation occurs when oocysts come into contact with oxygen and moisture, and the optimal temperature range for this process is between 20°C and 32°C. In the case of oocysts from mammals, the ideal temperature range is slightly lower, between 20°C and 25°C. Under these optimal conditions, sporulation can occur within 1 to 2 days, and the oocysts become infectious. However, it's important to note that oocysts are sensitive to temperature extremes, surviving poorly at temperatures below 30°C or above 40°C.
The process of sporulation involves the nucleus of the oocyst dividing multiple times to produce sporocysts, which then divide into two sporozoites each, becoming a sporocyst. The sporulated oocyst can contain four or more sporocysts, depending on the species. Once ingested by a susceptible host, the sporulated oocyst releases thousands of sporozoites into the intestine, causing infection and potentially leading to coccidiosis.
Coccidiosis is a disease caused by protozoa of the phylum Apicomplexa, and it is characterized by rapid parasite replication in host cells, resulting in extensive damage to the intestinal mucosa. The parasites invade the intestinal epithelial lining and underlying connective tissue of the mucosa, leading to inflammation and hemorrhage. Clinical signs of coccidiosis include diarrhea, decreased growth, dysentery, dehydration, and tenesmus.
In chickens, Eimeria tenella is a significant cause of coccidiosis. When ingested in the sporulated oocyst stage, E. tenella develops in the epithelial cells of the cecal pouches, causing coccidiosis. During this developmental period, some invaded epithelial cells become wandering cells, carrying the parasites deep into the mucosa and submucosa. This results in the entrapment of oocysts in the inflammatory tissues, which can remain for an extended period even after the initial infection has subsided.
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Oocysts are transmitted via insects, rodents, and equipment, and are resistant to some disinfectants
Oocysts are infective agents that are transmitted in a variety of ways, including via insects, rodents, and equipment. They are also known to be resistant to some disinfectants.
Oocysts are often transmitted via insects, such as flies and mosquitoes. For example, mosquitoes can ingest oocysts when they feed on infected human blood, as seen in cases of malaria. Oocysts are then transmitted to humans by mosquitoes. Oocysts can also be transmitted via rodents, such as rats, which can carry the parasite Toxoplasma gondii. T. gondii can infect and be transmitted by a wide range of warm-blooded animals, including humans.
Equipment and personnel, such as shoes, can also transmit oocysts. This is particularly relevant in agricultural and poultry settings, where oocysts can contaminate soil, housing, or tools. Oocysts can also be transmitted via water, as they are able to survive sewage treatment and travel through river systems to coastal areas.
Oocysts are known for their resistance to some disinfectants and environmental stress. Cryptosporidium oocysts, for instance, are resistant to many commonly used disinfectants, including chlorine-based disinfectants. This is due to the robust and impervious wall of the oocyst, which makes chemical disinfection extremely difficult. Oocysts are also highly resistant to most physical stress and environmental conditions, contributing to their ability to spread and survive in the environment for months.
While oocysts are resistant to many disinfectants, there are some treatments that can be effective. For example, peroxygen-based disinfectants, such as Ox-Virin, have been shown to reduce the viability of Cryptosporidium parvum oocysts. Increasing the time of exposure and concentration of the disinfectant can further enhance its effectiveness. Additionally, UV-C disinfection has been found to be effective in inactivating and possibly sterilizing oocysts in water.
Overall, the transmission and resilience of oocysts highlight the importance of hygienic measures and effective disinfection methods to prevent and control the spread of infections.
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Oocysts are released in their non-infectious, unsporulated form through the faeces of the host
Oocysts are a type of protozoan parasite called coccidia, which can infect a wide variety of birds, mammals, and reptiles. They are almost universally present in poultry-raising operations. However, clinical coccidiosis occurs only after the ingestion of relatively large numbers of sporulated oocysts by susceptible birds.
When schizonts rupture, merozoites are released, which either infect more enterocytes or develop into male or female gametes through gametogenesis. These gametes then fuse to form an oocyst, which is released in its non-infectious, unsporulated form through the faeces of the host. This process is known as the exogenous phase of the Eimeria life cycle. The unsporulated oocysts have a multi-layered cell wall that makes them highly resistant to environmental pressures.
Once expelled from the host, the unsporulated oocysts undergo sporulation upon contact with oxygen and moisture. This process can take anywhere from 1 to 7 days, depending on environmental conditions. Optimal conditions for sporulation are temperatures between 20 and 30°C, adequate moisture, and oxygen. Under these conditions, the oocyst nucleus divides several times to produce sporocysts, which then divide into two sporozoites, becoming a sporocyst.
Sporulated oocysts are infectious and can survive outside their host for up to 602 days. They are resistant to some commonly used disinfectants and can be transmitted via equipment, personnel, insects, and rodents. Ingestion of sporulated oocysts by susceptible chickens leads to the development of coccidiosis, a deadly disease that affects the intestinal tract.
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Oocysts are highly resistant to environmental pressures due to their multi-layered cell wall
Oocysts are a significant contributor to T. gondii infections, and they are prevalent in water, soil, and food. They are also responsible for coccidiosis in poultry, which costs the United States over $1.5 billion in annual losses. Coccidiosis is caused by protozoa of the phylum Apicomplexa, family Eimeriidae, and the most prevalent species of Eimeria that cause coccidiosis in poultry are E. tenella, E. acervulina, and E. maxima.
Oocysts are released into the environment by an infected host in their unsporulated form. These unsporulated oocysts have a multi-layered cell wall, which makes them highly resistant to environmental pressures. The outer layer of the oocyst wall is composed primarily of proteins and carbohydrates, providing structural strength, while the inner layer is primarily composed of lipids, offering protection from chemical insults. The multi-layered structure of the oocyst wall is essential for the parasite's survival in the external environment, acting as the first line of defense.
The oocyst wall's chemical constituents play a crucial role in its highly resistant nature, protecting the developing sporoplasm within. The outer part of the inner layer has a minor amount of lipid, while the innermost part contains a significant amount of lipid in its protein lamella. This unique composition provides the oocyst with the ability to withstand physical and chemical challenges, ensuring its survival in the environment for extended periods required for transmission between hosts.
The oocyst wall's resistance to environmental pressures is further demonstrated by its resilience to chlorination and other chemical water treatment strategies. The complex molecular structure of the wall, including its protein-lipid-carbohydrate matrix, contributes to this resilience. However, it is important to note that the oocyst wall is not completely impenetrable, and treatments such as UV irradiation and trypsin pretreatment have been shown to disrupt the wall's structure and facilitate the inactivation of oocysts.
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Coccidiosis is caused by the ingestion of infective sporulated oocysts from a contaminated environment
Coccidiosis is a parasitic disease of the intestine that is prevalent among pigeons, poultry, pigs, cattle, sheep, and rabbits. It is caused by the ingestion of infective sporulated oocysts from a contaminated environment. Oocysts are shed in the faeces of infected hosts and ingested by uninfected animals. Coccidiosis is a disease of animals kept under crowded conditions and occurs in many breeding establishments. Intensive, damp, dirty conditions predispose to coccidiosis, and the environment can become heavily contaminated.
The disease is caused by a protozoan parasite with a complex life cycle. Coccidia strains are highly host-specific. Oocysts are released in the non-infectious, unsporulated form through the faeces of the host. Once released, the unsporulated oocysts undergo meiosis upon contact with oxygen and moisture. This process is known as sporulation, and the oocysts take approximately 2 to 7 days to become infectious. The sporulated oocyst is said to be tetrasporic, meaning it contains four sporocysts, while each sporocyst contains two sporozoites.
Once ingested, the oocysts undergo a process called excystation, whereby thousands of sporozoites are released into the lumen of the intestine. The sporozoites invade the intestinal mucosa and become rounded trophozoites, which then divide into nucleated elongated merozoites that together form a meront. Once developed, the meront ruptures, as does the containing intestinal cell wall, thereby releasing the merozoites. Merozoites may repeat the process of meront production in one or more cycles before they ultimately progress to the gametogony stage.
The severity of the disease is directly dependent on the number of infective oocysts that are ingested. The more oocysts ingested, the more severe the disease. Clinical signs of coccidiosis include lethargy, depression, reduced normal grooming behaviour, and bloody diarrhoea.
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Frequently asked questions
Sporulated oocysts may not be found in a chicken cecum because the oocysts are not yet infectious.
Optimal conditions for sporulation are 70°–90°F (21°–32°C) with adequate moisture and oxygen.
Under optimal conditions, sporulation occurs within 1-2 days.
There are three stages in the life cycle of oocysts: sporogony, merogony, and gametogony.
Chickens become infected with oocysts by ingesting them from a contaminated environment.
