Vetstoria

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Scientific name

Eimeria spp

Cause

Coccidiosis in chickens is caused by seven different species of coccidia (genus Eimeria), which are single celled parasites that live in the gut wall of their host. These coccidia are host specific: turkeys and other species are not infected by fowl coccidia and vice-versa. The different species of coccidia live in different parts of the gut and can be divided into those causing intestinal coccidiosis (the majority) or caecal coccidiosis (one species).

Spread

Ingestions of faecal material containing the infective stage of the coccidian (small egg-like bodies called oocysts) which:

• Remain alive for a year in poultry sheds
• Very resistant to most disinfectants
  

Symptoms

• Mainly young birds (less than 3 weeks)
• Lethargy
• Muscle waste
• Pallor
• Ruffled feathers
• Drooping wings
• Pale and dry shanks
• Whitish soiling around the vents
• Diarrhoea (with blood)
• Sudden death
  

Post mortem findings

Depends on the type of coccidian responsible:

1. Caecal coccidiosis:

• Swollen blind guts (caeca)
• Caeca filled with blood/ cheesy plugs

2. Intestinal coccidiosis:

• White streaks/ spots in upper gut
• Intestin filled with blood
• Red spots/ dead tissue in lower gut
  

Diagnosis

Definite diagnosis can be confirmed only by laboratory examination. Material scraped from the lining of the gut is examined under a microscope and the coccidia are identified based on shape, size and location in the gut.

Coccidiosis can be confused with similar diseases such as blackhead, salmonellosis and necrotic enteritis.

Similar diseases

• Blackhead
• Salmonellosis
• Necrotic enteritis

Prevention - management aspects

• Because coccidia require moisture to become infective, the litter must be kept dry. Ventilation must be good and the birds should not be overcrowded.
• Birds gradually become immune if they are exposed to a low level of infection, but clinical disease occurs if the coccidiosis challenge is too great.
• Immunity to one species of coccidia does not protect poultry against other coccidial species.
• It is very risky to rely on hygiene alone to produce satisfactory control.
  

Vaccination

Effective live vaccines are available in the UK
Early exposure advisable
Closely follow the manufacturer's recommendations

Medication

Medication programs may be used as an alternative to vaccination. A wide selection of drugs (coccidiostatics) is available for prevention and treatment. The choice of drug will depend on the type of flock, the type of coccidia and the aim of the medication program. Most coccidiostatics have withholding periods and medication programs must take this into account.

Low dose rates of coccidiostatic may:

• Slow down a major build-up of coccidian
• Reduce the challenge to the bird
• Prevent outbreaks while allowing immunity to develop
• Be overwhelmed by heavy infestations

Outbreaks of coccidiosis may occur if:

• Low level of coccidiostatic in the feed
• Birds are not eating enough
• Early (before immunity has developed) withdrawal of coccidiostatic
• Lack of vitamin A and K
• Other diseases

Treatment

Treatment should start immediately when coccidiosis has been diagnosed. Whichever drug is used, the manufacturer's instructions must be followed.
Coccidiosis will often respond to treatment using coccidiostatics delivered in the drinking water.