Toxoplasmosis is a coccidian protozoan parasitic disease that affects mammals, birds, and reptiles. It primarily affects the central nervous system but can also affect the reproductive system, skeletal muscles, and critical organs, such as the heart, liver, and lungs. A single species, Toxoplasma gondii, is the cause of toxoplasmosis in all cases. It is a human health concern as well, with some 14% of the United States’ population being affected in serologic surveys. (As high as 68% in some geographic areas of the world.) It was as recently as 1969 that it was discovered that Toxoplasma was actually a close relative of Eimeria (a coccidian genus – commonly the cause of coccidiosis in poultry).
Unfortunately, Toxoplasma is rarely considered when trying to diagnose poultry problems with ataxia and incoordination. Turkeys, and waterfowl in particular, are typically asymptomatic and infections usually go unnoticed. Chickens can also be infected but suffer a greater number of symptoms, along with a higher rate of mortality.
Where Toxoplasmosis causes the greatest problem though, is in young ducklings. If passed to the duckling by its hen in the embryonic stage, the mortality rate after hatch is extremely high. Although not common, according to one study a hen can pass the parasite to one in every 327 fertile eggs. This method of infection or by environmental exposure at a very young age is what is of the greatest concern for mortality rate and/or permanent central nervous system damage. Once ducks reach adult age, Toxoplasmosis is typically chronic in nature and usually goes unnoticed. The youngsters are the ones that suffer the most.
The first sign of Toxoplasmosis is usually a young duckling flipping over onto its back with the inability to right itself. Sometimes a young duckling will simply be uncoordinated, flip over on its back occasionally, and then over time, learn how to right itself on a regular basis until he finally grows out of this awkward stage. Very small ducklings, when placed in the same pens as older, heavier ones will simply get knocked over in a flurry of activity. These are not the cases I’m referring to. I’m talking about the case where a young duckling spends most of his time on his back and ultimately gets trampled to death by the other ducks, dies from exhaustion from trying to right himself to no avail, or dies from starvation from the inability to reach food or water – unless you’ve intervened somehow on his behalf.
If you do intervene at this stage, you’ll probably find that the bird is also suffering from ulcerative conjunctivitis from grinding his eye into the earth or bedding, while trying to right himself. Symptoms for Toxoplasmosis also include congestion, weight loss, paleness and shrinking of the comb (in chickens), drop in egg production, whitish droppings, diarrhea, incoordination and ataxia, trembling, and blindness.
Although systemic in nature, the disease does most of its damage in the young and weak within the central nervous system. Even if treatment is found to be effective in killing the parasite within the system, the damage that causes the ataxia and incoordination is usually permanent. In rare cases, immediate treatment before too much damage is done can be effective.
The easiest method of treatment is the practice of prevention. The only known definitive hosts for T. gondii are cats and other members of the Felidae (feline) family through their droppings. Feral cats are the most obvious source but resident cats may also carry the disease with no obvious symptoms. (This subject may be somewhat familiar to you even though you don’t immediately recognize it, in that the risk of Toxoplasmosis is the primary reason why obstetricians recommend that pregnant women don’t keep cats or clean out the litter box if they already have a cat.)
In an open yard where there are free-ranging adult ducks, there may be little problem. And even if the ducks pick it up and are pretty healthy otherwise, they’re usually asymptomatic. But if the younger ducks or ducklings have any contact with the same yard or the droppings of cats, even through the travel of rodents, they become at risk.
There’s also a little known treatment process you can undertake if the duck is valuable and you think you’ve caught it immediately. You won’t find this under poultry health texts. Through research, I discovered this information through a combination of information found in general avian medicine texts, along with a veterinary drug handbook. (The treatment for cats would be the same as it would be for any poultry.)
The treatment calls for a drug called pyrimethamine at the rate of 0.5mg/kg PO (oral) per day given in two equal doses every 12 hours for 7 – 10 days, with sulfadiazine at the rate of 30 mg/kg also given orally with the daily dose split in two equal doses every 12 hours, for the same time period. I had my pharmacist combine the two in proper proportion in one liquid oral suspension that I was able to drench twice a day.
This treatment can be highly toxic to the bird and must not be given for a period longer than 2 weeks. To alleviate some of the toxicity, the Veterinary Drug Handbook recommends that you administer folic (or folinic) acid, at the rate of 1 mg/kg/day for the duration of the treatment. I also had this put into an oral suspension – but separately.
You will need the help of a qualified pharmacist to blend this medication for you and he will require a written, faxed, or phoned-in prescription from your vet, along with the bird’s precise weight for proper dosage. He’ll need the above drug dosage rates in order to calculate the proper strength of the oral suspension he’ll produce for your particular bird. If you don’t have a vet that’s willing to write the prescription for you, perhaps an agricultural college’s poultry lab would be willing to help.
The above treatment is the only known drug therapy for Toxoplasmosis, and is not always effective. Catching it early is the key.