A poultry farmer was raising more than 3000 broiler chickens on floor litter. Starting at 20 days of age, deaths began to occur, with more than 10 birds dying each day. Sick birds showed ataxia, drooping wings, spasmodic contractions of both legs, complete loss of appetite, increased thirst, pale combs and visible mucous membranes indicative of anemia, and bloody diarrhea. The mortality rate could reach around 85%. A summary of the diagnosis and treatment is provided below for reference by fellow professionals and poultry farmers.
I. Clinical signs
Sick birds were lethargic, stood motionless with their eyes closed, had fluffed-up feathers and drooping wings, and showed reduced appetite and increased water consumption. They were first constipated and then developed diarrhea, with feathers around the vent stuck together. Later, both wings became mildly paralyzed, their gait became unsteady, and their crops filled with fluid. They refused feed, and their droppings changed from watery and blood-tinged to bloody. Their mucous membranes and combs were pale, and they became emaciated. Most affected chicks died within 6 to 10 days of the onset of illness.
II. Postmortem findings
The ceca of sick birds were dilated and swollen, with thickened intestinal walls and inflamed, hemorrhagic mucosa that was reddish-brown in color. The tissue was firmer than normal. The intestinal contents consisted of blood and clots; in some birds, they contained a yellowish-white, caseous necrotic material mixed with blood. No obvious changes were observed in other organs.
Three, laboratory examination
1, smear microscopy
Take a small amount of the feces being examined or scrape material from the lesion and place it on a glass slide. Add 1–2 drops of physiological saline and mix thoroughly. Cover with a coverslip and examine under high magnification. If numerous spherical schizonts resembling peeled oranges, banana-shaped or crescent-shaped merozoites, and round oocysts are observed, coccidiosis can be provisionally diagnosed.
2, hemocytometer counting
Take 2 grams of the fecal sample to be tested, place it in a 50 ml beaker, add a small amount of tap water and mix well, then filter through a 60-mesh copper wire or nylon screen, and rinse the screen several times with tap water. Centrifuge the filtrate at 2 50() r/min for 10 minutes. Mix the precipitate with a small amount of saturated saline, transfer it to a 100 mI measuring cup, add saturated saline to the 60 mI mark, and mix thoroughly. Use a pipette to fill a McMaster egg counting chamber with the suspension. Let it stand for 5 min, then examine the McMaster egg counting chamber under a microscope at 10×10 or 10×40 magnification. Count all oocysts in each counting cell (1 cm × 1 cm × O.15 cm := 0.15 cm’ containing 100 small squares), calculate the average, and then perform the calculation.
Four. Prevention and control measures
Sulfonamide or sulfamethazine may be mixed into the feed at a proportion of 0.4%, fed for 3 days, withheld for 2 days, and then fed for 3 days; sulfachloropyrazine is mixed into the drinking water at 0.03% and used continuously for 3 days, with a withdrawal period of 5 days; nicarbazin may be added to the feed at 0.12 grams per kilogram or prepared as a 0.02% aqueous solution for free-choice drinking. Use continuously for 3～5 days to treat an outbreak of coccidiosis.
Strengthen husbandry management and maintain environmental hygiene. Strictly control all vehicles and personnel entering the chicken farm, and disinfect them thoroughly upon entry and exit. Bury or burn dead chickens, and prohibit animals such as dogs and cats from entering the farm. Begin using preventive medication on the first day after the chicks hatch.
V. Prevention and control experience
Under intensive farming conditions, the occurrence of coccidiosis shows no marked seasonal variation. The temperature of 22–30 degrees Celsius in a poultry house, which is suitable for chicken growth, is also the optimum temperature for coccidian oocysts to sporulate. Conditions such as excessively moist litter and poor ventilation favor the development of oocysts into infective sporulated oocysts.
Disinfectants commonly used in poultry houses have little effect on killing coccidian oocysts; flame disinfection is relatively effective. Note that disinfecting a poultry house can only provide an initial safe environment and cannot offer complete prevention. Large numbers of coccidian oocysts always accumulate during the 3–4 weeks after chicks are placed in the house.
The key to treating coccidiosis is detecting it promptly. Otherwise, the best time for treatment may be missed, resulting in chicken deaths and a longer treatment period.
Anticoccidial drugs can readily lead to drug resistance. When using them, rotation must be considered not only within the same batch of chickens, but also between batches housed in the same pen. Drug rotation means alternating between different types of anticoccidial drugs, not arbitrarily switching to another anticoccidial drug.
During treatment, care should be taken to select drugs whose peak activity occurs on days 3–4 of coccidian development. This makes the treatment more targeted and yields the best results.