Toxoplasmosis In Dogs
Toxoplasmosis: Infection Dangerous for Dogs and Humans
Toxoplasmosis is the most common parasitic infection worldwide. The organism that causes toxoplasmosis is Toxoplasma gondii. Toxoplasma gondii infects a wide range of warm-blooded vertebrates, including humans, and is one of the world's most successful parasites. T. gondii is used as a model for understanding infection by a variety of related parasites such as Plasmodium and Cryptosporidium. These parasites have a unique ability to directly penetrate their host cell, without the need for host uptake mechanisms. Invasion occurs very rapidly and avoids triggering off the respiratory burst in macrophages.
Within the host cell, the parasite resides in a modified vacuole that resists destruction, while intimately associating with host cell structures. Active secretion of parasite proteins results in modification of the vacuole, rendering it permeable to small molecules. Within this porous vacuole the parasite acquires nutrients from the host, allowing rapid replication. Understanding the complex biology of intracellular survival by T. gondii has bearing on the mechanisms of host resistance during both acute and chronic infection.2
Role of Dogs in Transmitting Toxoplasmosis
Dogs may act as a mechanical factor in transmitting toxoplasmosis to humans by rolling in infective substances and by ingesting fecal material. Just remember that 50% of stray dogs and cats carry T.gondii antibodies, which means that they have been infected and may transmit the parasite to you.
In dogs, toxoplasmosis is rare. It usually occurs in young dogs infected with distemper or other viral infection. In other cases, dogs develop disease without any other present infectious disease. It appears that many cases that were once considered to be toxoplasmosis in dogs are actually neosporosis, an infectious disease of dogs caused by Neospora caninum. The dogs pass parasite cysts in the feces which are ingested through contaminated food and water by cattle, sheep, goats, horses and other animals. Tissue cysts develop in these animals and dogs become infected by ingesting raw tissue containing these cysts.
Signs of Toxoplasmosis
Testing shows that many dogs are infected and are carriers of this parasite, but mostly puppies and young dogs develop the disease with clear clinical signs. These signs may include hepatitis, pneumonia, and ulcerative dermatitis. Infection of the central nervous system and musculature may result in behavioral changes, limb shaking, blindness, circling, muscle pain, progressive paralysis and finally death. Younger animals may have limb paralysis.
Diagnosis of Toxoplasmosis
Diagnosis is difficult and usually requires complex testing. The disease resembles many other infections such as distemper and rabies. In some cases treatment is effective, however, your dog may develop very serious complications affecting nervous system and muscles.
Prevention of Toxoplasmosis
- Avoid handling free-roaming dogs or any that show signs of illness.
- Protect your dogs from infections by avoiding feeding them raw meet or unpasteurized dairy products.
- Pregnant women should avoid changing cat litter if possible. If no one else is available to change the cat litter, use gloves, then wash hands thoroughly. Change the litter box daily because Toxoplasma oocysts require several days to become infectious. Pregnant women should be encouraged to keep their cats inside and not adopt or handle stray cats. Cats should be fed only canned or dried commercial food or well-cooked table food, not raw or undercooked meats.
References:
1. Parasitic Disease Information
2. Audra Charron, Sebastian Hakansson and Dana Mordue. Invasion and Intracellular Survival of Toxoplasma (In: Protozoans in Macrophages).
Comments
There are three infectious stages in the life cycle of T. gondii, i.e. tachyzoites, bradyzoites contained in tissue cysts, and sporozoites contained in sporulated oocysts. All three stages are infectious. Tachyzoites play the major role in vertical transmission of T. gondii. By contrast, they are very sensitive to environmental conditions and are usually killed rapidly outside the host. T. gondii may be transmitted via consumption of unpasteurised goat's milk. Therefore, it is advisable that milk, in particular goat's milk, should be pasteurised or boiled before human consumption. This is particularly important for its use in infants who have a lower concentration of proteolytic enzymes in the digestive tube and who are more susceptible to toxoplasmosis than adults.
Posted by Guest_3444 on Thursday, November 10, 2011
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