CoccidiosisFarooq Sarwar

Talha Hussain

Amanat Ali

Definition

Coccidiosis is a parasitic disease of the intestinal tract of animals caused by coccidian protozoa.

The disease spreads from one animal to another by contact with infected feces or ingestion of infected tissue.

Diarrhea, which may become bloody in severe cases, is the primary symptom.

Most animals infected with coccidia are asymptomatic, but young or immunocompromised animals may suffer severe symptoms and death.

Etiology

Coccidia are almost universally present in poultry-raising operations, but clinical disease occurs only after ingestion of relatively large numbers of sporulatedoocysts by susceptible birds.

Both clinically infected and recovered birds shed oocysts in their droppings, which contaminate feed, dust, water, litter, and soil.

Oocysts may be transmitted by mechanical carriers (eg, equipment, clothing, insects, farm workers, and other animals).

Fresh oocysts are not infective until they sporulate; under optimal conditions (70°–90°F [21°–32°C] with adequate moisture and oxygen), this requires 1–2 days.

Etiology

Coccidia are host-specific, and there is no cross-immunity between species of coccidia.

The prepatent period is 4–7 days. Sporulated oocysts may survive for long periods, depending on environmental factors.

Oocysts are resistant to some disinfectants commonly used around livestock but are killed by freezing or high environmental temperatures.

Pathogenicity

Pathogenicity is influenced by

host genetics

nutritional factors

concurrent diseases

age of the host

and species of the coccidium

Pathogenicity

Eimeria necatrix and Eimeria tenella are the most pathogenic in chickens,

E kofoidi and E legionensis are the most pathogenic in chukars

E lettyae is most pathogenic in bobwhite quail.

E phasiani and E colchici are pathogenic in pheasants.

Factors contributing to outbreaks

litter moisture content exceeding 30% due to ingress of rain or leaking waterers.

immunosuppression (Marek’s disease, IBD, mycotoxins)

suboptimal inclusion of anticoccidials or incomplete distribution (poor mixing) in feed.

environmental and managemental stress such as overstocking,

inoperative feeding systems, inadequate ventilation.

Epidemiology Coccidiosis is seen universally, most commonly in young animals

housed or confined in small areas contaminated with oocytes.

Coccidian are opportunistic pathogens; if pathogenic, their virulence may be influenced by various stressors.

Therefore, clinical coccidiosis is most prevalent under conditions of poor nutrition, poor sanitation, or overcrowding, or after the stresses of weaning, shipping, sudden changes of feed, or severe weather.

In general, for most species of farm animals, the infection rate is high and rate of clinical disease is low (5–10%), although up to 80% of animals in a high-risk group may show clinical signs.

Older animals usually are resistant to clinical disease but may have sporadic inapparent infections. Clinically healthy, mature animals can be sources of infection to young, susceptible animals.

Clinical signs

Signs of coccidiosis range from decreased growth rate to a high percentage of visibly sick birds,

severe diarrhea,

high mortality

Feed and water consumption are depressed

Weight loss

decreased egg production

Clinical signs

increased mortality may accompany outbreaks.

Mild infections of intestinal species, which would otherwise be classed as subclinical, may cause depigmentation and potentially lead to secondary infection, particularly Clostridium spp infection.

Survivors of severe infections recover in 10–14 days but may never recover lost performance.

1. E tenella

E tenella infections are found only in the ceca and can be recognized by

accumulation of blood in the ceca

and by bloody droppings.

Cecal cores, which are accumulations of clotted blood, tissue debris, and oocysts, may be found in birds surviving the acute stage.

Coccidiosis site parasitized

by E tenella in poultry.

2. E necatrix

E necatrix produces major lesions in the anterior and middle portions of the small intestine.

Small white spots, usually intermingled with rounded, bright- or dull-red spots of various sizes, can be seen on the serosal surface. This appearance is sometimes described as “salt and pepper.”. In severe cases, the intestinal wall is thickened, and the infected area dilated to 2–2.5 times the normal diameter. The lumen may be filled with blood, mucus, and fluid. Fluid loss may result in marked dehydration. Although the damage is in the small intestine, the sexual phase of the life cycle is completed in the ceca. Oocysts of E necatrix are found only in the ceca. Because of concurrent infections, oocysts of other species may be found in the area of major lesions, misleading the diagnostician.

Developmental stages of E necatrix from scraping of midgut(poultry), Feulgen stain, 40X.

Gross lesions of E necatrix with frank hemorrhaging into the midgut in a chicken.

Coccidiosis site parasitized by E necatrix in

poultry.

3. E acervulina

E acervulina is the most common cause of infection.

Lesions include numerous whitish, oval or transverse patches in the upper half of the small intestine, which may be easily distinguished on gross examination.

The clinical course in a flock is usually protracted and results in poor growth, an increase in culls, and slightly increased mortality.

Developmental stages of E acervulina from mucosal scraping of duodenal loop in poultry, new methylene blue, 40X.

Gross lesions of E acervulina with white longitudinal plaques in the duodenal loop of a broiler chicken.

Coccidiosis site parasitized by E acervulina in poultry.

4. E brunetti

E brunetti is found in the lower small intestine, rectum, ceca, and cloaca.

In moderate infections, the mucosa is pale and disrupted but lacking in discrete foci, and may be thickened.

In severe infections, coagulative necrosis and sloughing of the mucosa occurs throughout most of the small intestine.

Oocysts of E brunetti from mucosal scraping of small intestine, new methylene blue, 100X.

Gross lesions of E brunetti in small intestine of a broiler chicken.

Coccidiosis site parasitized by E brunetti in poultry.

5. E maxima

E maxima develops in the small intestine, where it causes dilatation and thickening of the wall; petechial hemorrhage; and a reddish, orange, or pink viscous mucous exudate and fluid. The exterior of the midgut often has numerous whitish pinpoint foci, and the area may appear engorged. The oocysts and gametocytes (particularly macrogametocytes), which are present in the lesions, are distinctly large.

Oocysts of E maxima, 100X. Coccidiosis site parasitized by E maxima in poultry.

Diagnostic table of coccidia

Differential diagnose

Coccidioses should be differentiated from NE, UE and histomonosis(typhlohepatitis).

Control

Poultry that are maintained at all times on wire floors to separate birds from droppings have fewer infections; clinical coccidiosis is seen only rarely under such circumstances.

Other methods of control are vaccination or prevention with anticoccidial drugs.

Treatment

sulfonamides are widely used:

sulfadimethoxine, sulfaquinoxaline, I sulfamethazine, but they should not I be used in layer hens.

The supplementation I of vitamins A and K promotes the recovery.

References

http://www.thepoultrysite.com/

http://www.merckmanuals.com/

Diseases of Poultry Y M saif

A Color Atlas Of Poultry Diseases