Coccidiosis

One of the biggest causes of economic losses in poultry

Introduction • Disease characterised by bloody diarrhoea and high mortality • Coccidia grow in intestinal tract and causes – Defective digestion and absorption – Dehydration – Blood loss – Increase susceptibility to diseases

Nature of disease • Subclinical • Clinical – Subclinical infection cause defective feed conversion – Clinical outbreaks common between 3-6 weeks of age and rarely in flocks < 3 weeks – Disease mild or severe depending on the no. of oocysts ingested – Overcrowding predisposes to disease

Etiology • Eimeria spp. • No cross immunity between species • Affects mainly broilers, growers on deep litter • Rarely affects layers and breeders • Short direct life cycle and high reproductive ability • Prepatent period 4-5 days

Different species of Eimeria • • • • • • • •

Seven disease producing species E. tenella , E. necatrix and E. brunetti most harmful E. acervulina and E. maxima moderately harmful E. mitis and E. praecox least harmful found in duodenum E. tenella affects caeca E. necatrix and E. maxima affect middle portion of intestine E. brunetti lower portion of intestine E. acervulina upper portion of intestine

Sporulation • Sporulated oocyst - infective • Non sporulated oocyst - non infective • Sporulation is conversion of noninfective form of oocyst to infective form • Requires warmth (25-30oC),moisture and oxygen

Sporulated Oocyst • Protected by thick oocyst wall • Survive for months or years in environment • Killed by temperature above 56oC, drying • Tolerate most disinfectant • Killed by ammonia and methyl bromide but these are harmful gases

Source Of Infection • Millions of oocysts are formed from single ingested oocysts • As few as 10,000 ingested oocysts produce coccidiosis on ingestion • Faecal material (teaspoonful), has millions of oocysts • Other sources are shoes , feed trucks, crates ,pets, rodents, equipments

Immunity • Day old chicks do not get maternal antibodies • Birds acquire active immunity by infection during first few weeks of life • Species specific • Best by “trickle infection” (repeated exposure to low dose of oocysts) • Cell mediated immunity more important • IgA > role than IgM, IgG

Occurrence • Oocysts continue to exist in environment • Occurrence depends on trickle infection and increase in parasite population • Severity depends on dose of oocysts and species • Wet litter favors sporulation and therefore increases disease occurrence • Floor reared birds caged for laying show disease due to prevention of reinfection • Less in summer more in winter and rainy

Spread • Ingestion of sporulated oocyst (natural method) • Mechanically by animals, insects, equipments, wild birds ,dust • Movement of people and equipments between farms

Pathogenesis • Harm due to destruction of epithelial cells • Surviving cells stimulated so hyperplasia of the intestinal epithelium • Enlargement of villi • In heavy infection-denudation of mucosa so severe hemorrhage and anemia may result • Infection causes intense inflammation of the lamina propria and submucosa

Symptoms • Caecal coccidiosis – Blood droppings – High mortality – Reduced weight gain – Emaciation – Mortality occurs 5-6 days following infection

Symptoms • Intestinal coccidiosis (caused by Eimeria necatrix) – Common in relatively older birds – Droppings contain blood, fluid and mucus – 25% mortality in commercial flocks • Moderately harmful species cause reduced wt. gain, poor FCR, diarrhea, loss of appetite and sometimes mortality

PM Findings • Vary with the species of coccidia involved • E.tenella- Caeca greatly enlarged and distended with clotted blood. • E. necatrix- The middle portion of the small intestine is usually distended to twice its normal size and the lumen may be filled with blood. Infection is seen as white or red foci from surface. • E. brunetti-The lining of intestine is covered with tiny hemorrhages. Mucosa may be swollen and thickened.

Cont… • E.maxima- Middle portion of the small intestine may be lose and filled with fluid, containing mucus and blood. • E. acervulina-The mucosa may be covered with white plaques, which tend to arrange in transverse fashion and cause a ladder like appearance because of striations. • E. mitis and E. praecox- the changes are very slight and can be easily

Eimeria necatrix: is highly pathogenic species. Red petechiae visible on serosa

Eimeria necatrix: petechiae, white patches on serosa.

Eimeria necatrix: extensive hemorrhages in small intestine

Moderate Eimeria maxima infection in the jejunum of a chicken. The lesions are subtle compared to other forms of coccidiosis. The intestine is slightly thickened and there are scattered hemorrhages in the mucosa when seen from the inside.

Diagnosis • Symptoms • PM examination • Microscopical examination of mucosal scraping – Finding of few oocysts indicate presence of infection not disease – Disease diagnosed as coccidiosis only when gross lesions are severe and associated with mortality

Treatment • • • •

Sulfonamides Amprolium Toltrazuril Diclazuril Treatment is costlier so control should be followed in broilers

Control • Disease easy to prevent than to treat – Drugs – Hygiene – Vaccine

Drugs • Ionophores- maduramycin, salinomycin, monensin • Thiamine analogs – amprolium • Sulphonamide- toltrazuril, diclazuril • Carbanilid- nicarbazin • Pyridones- clopidol • Quinolones-decoquinate

Features And Effects Of Anticoccidials • • • •

May be static or cidal Each class unique in type of action Some are effective against all species Toxic at higher doses (ex. Ionophores cause temporary paralysis) • Toxicoses may cause death (may be >70%) due to respiratory failure and dehydration

Drug Resistance • Use of single drug causes drug resistance • To overcome this: – Shuttle programme- Use one drug in starter and another in grower feed – Rotation of drugs- Improve productivity as new drug will be effective against build up coccidia

Hygeine • Reduces no. of oocysts contaminating environment • Keep litter dry • Maintain birds on perforated floors • Sometimes this is disadvantageous as aquired immunity while on litter may decrease

Vaccines • Live vaccine-contain all seven species, given at 5-9 days of age • Killed vaccine – contains purified antigen from gametocyte stage of Eimeria in oil emulsion • Dose 0.5 ml I/M into breast muscle • Regimen –twice before laying between 1822 weeks at 4-8 weeks interval