How Coccidia do Harm to the Goat

and why it is Potentially Fatal

The basic life cycle of the coccidia parasite

Life Cycle of Coccidia

• The oocysts of coccidia will contain about eight parasites.   They will shed themselves in the feces of an infected animal.   These oocysts can survive up to one year.
   
• If a goat  ingests an oocyst, the parasites will be released and invade the gut of the new host.
• The parasites will then divide through asexual reproduction into a hundred or more daughter cells.
• The daughter cells will eventually break out of the gut wall to invade a new area and repeat the process.
  • In 10-14 weeks the daughter cells can multiply over a millionfold.
• During this stage, parts of the gut wall will have parasites attached that have developed into male and female sex cells.
• The female sex cells are fertilized and secrete oocysts into the gut wall and around themselves.
• The oocysts will then shed in the feces and thus will complete the lifecycle.
   
• Coccidia is caused by the protozoa Eimeria
  • There are four types of pathogenic species:
    • Eimeria Crandalis
      • Infects ileum
      • Impairs absorptive capacity, causing scours
    • Eimeria Ovinodalis
      • Infects ileum, cecum and colon
      • Impairs absorptive capacity, causing scours
      • Damages the gut's ability to regenerate causing more severe, prolonged diseases
    • Eimeria Ahsata
    • E Ovinoidali

So.. What does this all mean?

 Simply put.. the numbers of coccidia in the small and large intestine, do damage to the walls of the intestine making  nutritional  absorption almost nil- there by basically starving the goat internally. The oocysts also kill off the mucosal lining and the intestine can become necrotic, dying off and leaving the goat with the inability to  absorb nutrients form the food they eat..  Goats who have had severe cases of coccidiosis, and survive may never be fully able to grow, add weight  and thrive like a goat who has not had intestinal damage. All livestock have coccidia, it is when something stressful happens to the animal that the parasite  increases in horrendous numbers  and does the damage  it does.

 Numerous species of Eimeria  are found in goats in North America. The Eimeria  spp  are host-specific and are not transmitted from sheep to goats. E arloingi , E christenseni , and E ovinoidalis are highly pathogenic in kids.

Clinical signs include

1. diarrhea with or without mucus or blood 
2. dehydration
3. emaciation
4. weakness
5. anorexia
6. and death.

Some goats are actually constipated and die acutely without diarrhea. Usually, stages and lesions are confined to the small intestine, which may appear congested, hemorrhagic, or ulcerated, and have scattered pale, yellow to white macroscopic plaques in the mucosa.

Histologically, villous epithelium is sloughed, and inflammatory cells are seen in the lamina propria and submucosa. In addition, there have been several reports of hepatobiliary coccidiosis with liver failure in dairy goats.

Diagnosis of intestinal coccidiosis is based on finding oocysts of the pathogenic species in diarrheal feces, usually at tens of thousands to millions per gram of feces. It is not unusual to find oocyst counts as high as 70,000 in kids without overt disease, but weight gain may be affected.

Angora and dairy goats, raised under different management practices, may have similar patterns of exposure of kids. Just after parturition, nursery pens and surrounding areas may be heavily contaminated with oocysts from does.

Resistance to infection is decreased just after shipping, changing rations, introducing new animals, or mixing young with older animals. Coccidiostats can be administered to a herd immediately after diagnosis or as a preventive in predictable situations such as those mentioned above. Merck Veterinary Manual

 Coccidia Lifecycle Phases

EXTERNAL PHASE (grass, feed or water contaminated with feces)
After sporulation, the oocyst is able to withstand commercial cleansers and disinfectants
and can survive and remain in the environment for years.

Step 1
The sporulated oocyst is a mature egg containing 4 sporocysts, each with 2 sporozoites.

SUBCLINICAL PHASE (small intestine)
Subclinical coccidial infections damage the villi of the small intestine and can reduce nutrient absorption.

Step 2
After the sporulated oocyst is ingested and exposed to carbon dioxide and digestive enzymes in the host’s digestive tract, it splits open (or excysts) and releases its 8 sporozoites.

Step 3
Each highly motile sporozoite swims or glides to the small intestine.

Step 4
3 to 7 days after ingestion, sporozoites enter the small intestine and reproduce asexually through a budding process called schizogony (completed Day 5 through Day 10). Each sporozoite can produce up to 120,000 first-generation merozoites, which are released when the host cell bursts.

Step 5
These merozoites undergo another asexual division in the lower small intestine and upper large intestine. Each first-generation merozoite can produce 30 second-generation merozoites.

CLINICAL PHASE (large intestine)
Clinical signs of coccidiosis include bloody scours, blood-tinged feces, dehydration, anemia and general loss of body condition.

Step 6
Second-generation merozoites penetrate the large intestine, differentiating themselves as either male (microgametes) or female (macrogametes) and begin the sexual stage of the life cycle.

Step 7
A microgamete fertilizes a macrogamete to produce a zygote. The zygote forms a protective wall and becomes an oocyst, which causes the host cells to rupture.

EXTERNAL PHASE (feces, contaminated grass, feed or water)
After sporulation, the oocyst is able to withstand commercial cleansers and disinfectants and can survive and remain in the environment for years.

Step 8
The oocyst is passed, along with tissue and fluids from the ruptured cells, in the feces. At this stage the oocyst is unsporulated (immature) and is not infective.

Step 9 In the presence of oxygen, the oocyst undergoes a process called sporulation. It takes 2 to 4 days for an oocyst to become a sporulated oocyst, capable of infecting cattle. A single oocyst can produce up to 23 million oocysts during the next life cycle.

Coccidia Reproduction

A single sporulated oocyst has the potential to turn into 23 million oocysts after just 21 days inside the host animal. During asexual division, one sporulated oocyst divides into 8 sporozoites, each of which can divide into 120,000 first-generation merozoites (a total of up to 960,000).

Coccidia Facts in Cattle (same applies to Goats)

• Coccidia are obligate intracellular parasites and must return to the host to continue their life cycle.
• The coccidia life cycle is a continuous process, with reinfection occurring daily.
• Cattle routinely ingest thousands of oocysts each day through feces, contaminated feed and water, or by preening their own coat or licking that of another animal.
• As few as 50 thousand oocysts can cause severe disease in the calf.
• Cattle can develop immunity to coccidia after extended subclinical infection.
• The most effective way to manage coccidial infections is a combination of preventive and treatment measures.
• Single cell oocysts are passed in the feces of cattle, are resistant to disinfectants, and can remain in the environment (particularly moist, shady areas) for long periods of time (years) and maintain their infectivity.