What is Sarcocystis Infection?
Sarcocystis is caused by a protozoan parasite species called Sarcocystis, which is usually transmitted to canines by the ingestion of infected meat. The Sarcocystis parasite has a complicated life cycle which requires two separate hosts to complete and can be found in diverse populations of animals. Sarcocystis infections commonly go unnoticed, often only uncovered as an incidental finding during necropsies. The cyst caused by the parasite can occasionally cause swelling in the tissues it settles in, which can lead to additional complications.Sarcocystis is an infection caused by a protozoan parasite species called Sarcocystis. Most Sarcocystis infections are asymptomatic, but complications can arise when the parasite migrates from the gut to other tissues in the body.
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Symptoms of Sarcocystis Infection in Dogs
Infections from Sarcocystis are generally asymptomatic, but in rare cases, serious complications can arise. Indications of complications caused by Sarcocystis can include:
- Severe myositis (swelling of the muscle tissue)
- Sensitivity to touch
- Muscle pain
- Hind limb paresis
- Involuntary rapid eye movement
- Low white blood cell count
There are many varieties of the Sarcocystis parasite. The strains are similar enough that it can be difficult to differentiate one from another. Although they are similar in lifecycle and behavior, they can often be distinguished by size, geographical location or host preference. Canines are susceptible to many varieties, both as direct and intermediate hosts.
Specific varieties that canines are susceptible to include:
- Sarcocystis arieticanis
- Sarcocystis camelicanis
- Sarcocystis capracanis
- Sarcocystis cruzi
- Sarcocystis hircicanis
- Sarcocystis neurona
- Sarcocystis suicanis
- Sarcocystis tenella
- Sarcocystis wenzel
Causes of Sarcocystis Infection in Dogs
Sarcocystis is caused by a protozoan parasite species called Sarcocystis which migrate from the intestines to the muscles and other tissues and cause cysts of varying sizes. These cysts can be particularly problematic when they migrate to skeletal muscle, or lung and brain tissues. The protozoa Sarcocystis has a complicated life cycle that requires two hosts of differing types. It is transmitted to dogs in one of two ways:
- Through exposure to tainted feces
- Through eating infected meat and tissue
It is much more common for predators such as dogs to get the infection from eating raw meat than through exposure to feces.
Diagnosis of Sarcocystis Infection in Dogs
The self-limiting nature of a Sarcocystis infection and the common lack of apparent symptoms means that in most cases it goes unnoticed. In the rare event that your canine develops symptoms that could be related to a Sarcocystis infection, you will want to inform your veterinarian if you are aware of any raw or untreated meat that they may have ingested. The veterinarian is likely to begin the process of diagnosis by looking for obvious cysts on extremities and examining the fecal matter closely.
Definitive diagnosis of Sarcocystis is either through examination of the feces through biopsy of excised tissue and visual confirmation of infective sporocysts. Other parasites such as Toxoplasma gondii and Neospora caninum, are often diagnosed the same way. It may be several days after the ingestion of tainted meat for the sporocysts to begin to show up in the feces. Some species of the parasite are large enough to be spotted with the naked eye while others are difficult to detect even microscopically, and special dyes are often required to locate the sporocysts.
Treatment of Sarcocystis Infection in Dogs
A Sarcocystis infection does not commonly cause much distress for canines, and generally clears up on its own. As such symptomatic Sarcocystis may not require any treatment at all. Therapeutic treatments have been mostly ineffective on tissue cysts once they develop, but depending on your specific circumstances your veterinarian may choose to consider anti-parasitic agents or antimicrobial drugs in an attempt to reduce the length and severity of the infection.
Anti-inflammatory drugs may also be used to manage the pain and swelling caused by the infestation, but in the case of Sarcocystis, the best treatment is prevention. Avoid feeding any meat to your dogs that have not been either heated to at least 158 degrees for 15 minutes or frozen for 1-2 days. Preventing them from eating dead animals will also reduce the risk of infection. Infection by the Sarcocystis parasite tends to be more problematic for livestock than for dogs or cats, and it can put horses at risk for Equine protozoal myeloencephalitis and multifocal myelitis. If your canine has been diagnosed with an active Sarcocystis infection, even if it is asymptomatic, it is best to avoid direct or indirect contact with livestock and horses.
Recovery of Sarcocystis Infection in Dogs
Follow your veterinarian’s instructions for any medications that may end up being prescribed. It is important to complete the prescription even if your animal stops showing symptoms in order to prevent the infection from reoccurring. Keep in mind that if your dog is experiencing symptoms there is a good chance that he or she is much more sensitive to touch than usual. Use care in interacting with your companion and ensure that others do as well to avoid discomfort, especially if swelling is involved.
Clean and discard feces promptly and securely to avoid infecting any other creatures and perpetuating the disease. It is also a good idea to disinfect all crates, water bowls, feeding dishes, floors and bedding at home as well, repeating the process regularly until the infection is cleared.
Sarcocystis Infection Questions and Advice from Veterinary Professionals
Is the Sarcocyst that affects dogs the same that causes EPM in horses? And are the signs the same?
There are many different species under the genus Sarcocystis, the one responsible for equine protozoal myeloencephalitis is Sarcocystis neurona, the definitive host is opossum but there are reports of infection in dogs; there are numerous species of Sarcosystis which are named after the hosts they infect (goat – dog, Sarcocystis capracanis). Usually in dogs, the parasite resides in the gut at the final stage of the life cycle and sheds in the faeces; the only problem for dogs is if the parasite migrates to other bodily tissues which would cause symptoms depending on the location of migration which is normally muscle swelling, pain, hind limb paresis, change of behaviour or fever. Regards Dr Callum Turner DVM
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