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Atoxoplasmosis (black spot disease / enlarged liver) in canaries and finches

Cause: Isospora (Atoxoplasma) spp. - infect the blood and liver, not only the intestines · Type: Parasitic · Quarantine: 45 days

Other names: Atoxo، Black spot، Liver enlargement، The black dot

Symptoms

How it spreads

Through the beak and droppings (fecal-oral): the oocysts pass in the droppings, mature on the ground and infect other birds. Adult birds become carriers and infect the chicks.

Diagnosis

The droppings may not always show oocysts. The vet may do a blood smear (buffy coat) or PCR, and necropsy shows enlargement of the liver and spleen (Merck). Naming warning: Arab breeders use the name "the black dot" for three different things in canaries: atoxoplasmosis, coccidiosis and circovirus (and sometimes a bacterial infection), because the liver/gallbladder appears as a dark dot through the abdominal skin in chicks. Laboratory diagnosis is required.

Treatment

Breeders and vets use toltrazuril or sulfonamides (such as sulfachloropyridazine). Treatment stops oocyst shedding but it is hard to eliminate the disease completely. This is a disease that needs a veterinary diagnosis. [Update 3] Confirmed: Merck says the disease is highly virulent in canaries and is still diagnosed in them (enlarged liver and spleen); a published trial with toltrazuril in passerines stopped oocyst shedding within a week (Mohr 2017), with possible transmission through the egg. An Iranian study in 2023 confirmed that the "black dot" in dead canaries was visceral Isospora in a sample of 50 birds. No published dose for canaries was found in the sources read. (All under veterinary supervision.)

Prevention

Daily cleaning of droppings, a mesh floor, separating the chicks from the adults after weaning, and preventive treatment before the season if the disease is present on the farm.

Season

Highest in summer and autumn (weaning and molt season)

Treatment and doses are decided by an avian vet after an exam; Zajel does not publish doses.

Other diseases

Sources