Sarcocystis

What is Sarcocystis?

Sarcocystis species are tiny parasites that live inside cells. They were first discovered in 1843 by Miescher, who found white, threadlike cysts in the muscle of a mouse. For about 20 years, these cysts were called Miescher’s tubules. For a long time, scientists didn’t know if they were fungi or a type of protozoa, which are small, one-celled organisms.

Similar structures were discovered in the muscle of a pig in 1865. Then, in 1967, scientists used a powerful tool called an electron microscope to take a closer look. They found that these bodies, shaped like spindles or crescents, had features like the ones seen in other protozoans, such as Toxoplasma and Eimeria.

It has been found that Sarcocystis species have a complex life cycle involving more than one host, and this was determined in 1972. This life cycle depends on a relationship between prey and predator, resulting in what are called definitive and intermediate hosts.

Over time, about 150 human cases in which symptoms were noticed, have been reported. More than 100 different types of Sarcocystis have been found, mostly in muscle tissue from various hosts. These hosts can include mammals, birds, and reptiles.

What Causes Sarcocystis?

Sarcocystosis is a type of infection caused by a parasite called Sarcocystis. In humans, this infection can appear in two forms: one affects the intestines and the other affects the muscles.

Humans can play two roles in the life cycle of this parasite. They can serve as either ‘definitive’ or ‘intermediate’ hosts. ‘Definitive’ means that the parasite reaches maturity and reproduces in humans, while ‘intermediate’ means that the parasite lives part of its life cycle in humans before moving on to another host.

For instance, Sarcocystis hominis, found in cattle, and Sarcocystis suihominis, found in pigs, see humans as definitive hosts. These types of Sarcocystis can lead to intestinal Sarcocystosis, an infection in the gut.

On the other hand, there are types of Sarcocystis that likely use reptiles as definitive hosts, such as Sarcocystis nesbitti. Humans can become infected with these parasites by eating food or drinking water that has been contaminated with the parasite’s eggs.

It is also possible that there are undetermined species of this parasite where humans can serve as a definitive host. This is because people around the world consume a wide range of meats from domesticated and wild animals, as well as birds.

So, it’s crucial to ensure food and water are free from contamination to avoid these infections.

Risk Factors and Frequency for Sarcocystis

Sarcocystis is a type of infection that can affect humans and it’s found in different parts of the world. Muscular sarcocystosis, a form of this infection, is most frequently reported in Asia and Southeast Asia. However, there have been isolated cases reported in Europe, Africa, and the Americas. In West Malaysia, a study found that nearly 20% of the population tested had antibodies for Sarcocystis, indicating exposure to the infection.

Another form of this infection, intestinal sarcocystosis, is reported globally except in Africa and the Middle East. It’s more often found in Europe when compared with other continents. Many cases can go undetected or unreported because they might not show any symptoms. When symptoms do appear, they’re usually in the form of acute or rare chronic gastrointestinal discomforts, which can be easily misdiagnosed. In studies from Poland and Germany, 10.4% and 7.3% of the examined children’s fecal samples, respectively, showed signs of Sarcocystis. Cases have also been reported in countries like Vietnam, Slovakia, Spain, Tibet, Cambodia, Iran, and Australia.

Signs and Symptoms of Sarcocystis

If you’ve eaten undercooked or raw pork and beef, there’s a chance you could be at risk for a condition known as sarcocystosis. It’s important to note that this condition can also be caused by eating undercooked meat from other animals like domestic or wild mammals, birds, and reptiles. However, most instances of sarcocystosis don’t cause any noticeable symptoms in humans.

If this infection does lead to symptoms, they can manifest in two specific ways or as a combination of both. The first type, called muscular sarcocystosis, can result in:

• Fever
• Musculoskeletal pain
• Rashes
• Bronchospasms (difficulty breathing because of tightened airways)
• Cardiomyopathy (heart muscle disease)
• Subcutaneous swelling (swelling under the skin)

The second type, known as intestinal sarcocystosis, can lead to symptoms such as:

• Nausea
• Loss of appetite
• Vomiting
• Abdominal pain
• Bloating
• Diarrhea

When examined by a medical professional, people with this condition might show signs of enlarged lymph nodes, enlarged liver, or tender muscles, particularly if the disease has spread throughout the body. These symptoms may also be present in cases where the disease is localized in the muscles or intestines.

Testing for Sarcocystis

Blood tests may show increased levels of certain types of white blood cells called lymphocytes and eosinophils. Some people may also have increased levels of liver enzymes such as alanine aminotransferase, lactate dehydrogenase, slight increases in C-reactive protein (a substance produced in the liver in response to inflammation), and erythrocyte sedimentation rate (a measurement of how quickly red blood cells settle at the bottom of a test tube, with high rates usually indicating some sort of inflammation in the body).

In cases where the muscle is affected, we might find increased levels of creatine kinase or lactate dehydrogenase (these are markers indicating muscle damage). Importantly, a definitive diagnosis may also be aided by your health history, including symptoms of stomach illness and eating habits like consuming raw or partially cooked meat.

To detect the presence of specific parasites, stool studies can be utilized. These can involve different laboratory techniques that help to identify parasite eggs or cysts in the fecal samples. Methods such as periodic acid-Schiff stain can be used to detect parasitic structures, called oocysts or sporocysts, in the stool samples.

Muscle biopsy under a microscope can show the presence of a particular kind of parasite, sarcocyst, which may contain numerous slow multiplying cells, also called bradyzoites. Furthermore, imaging techniques such as MRIs can help to find cysts in your muscle and guide biopsies.

Currently, we do not have accurate and sensitive tests for detecting Sarcocyst infections. Although past attempts have been made to utilize methods such as Immunofluorescence assays, enzyme-linked immunosorbent assays, and serological methods to detect antibodies to this parasite, these tests are not broadly available and their reliability is still under investigation. The exact response of the immune system to this parasite is yet to be understood fully due to limited case studies and complex interactions between the host and the parasite. Detection of Immunoglobulin G, an antibody, is not a reliable method either.

Treatment Options for Sarcocystis

Intestinal sarcocystosis is a condition that currently doesn’t have any proven prevention or treatment approaches, whether in humans or animals. Doctors have suggested various treatments, but they have found varied levels of success and are usually based on individual case reports and experiences. Treatments that have been explored include medications such as Dithiazanine, Pyrimethamine with sulfisoxazole, and Acetylspiramycin, but none have shown to be completely successful. In some cases, doctors have tried surgery to remove the affected part of the small intestine, known as the ileum.

For a different form of the disease called muscular sarcocystosis, medications like Albendazole have been tried but were found to be ineffective. The drug cotrimoxazole might help improve symptoms and prevent an increase in creatine kinase levels, a substance that can indicate muscle damage. Corticosteroids, a type of medicine that helps reduce inflammation, were shown to improve muscle inflammation known as myositis. However, it’s uncertain whether medicines that suppress the immune system would lessen inflammation or actually support the growth of the parasites causing this condition.

Lab studies have suggested that the drugs Pyrimethamine and Trimethoprim could help fight against Sarcocystis, the parasite that causes sarcocystosis. However, no structured clinical trials have been done to test these results in real patients. Right now, researchers can’t recommend one treatment as being superior due to a lack of controlled studies and enough proof concerning available treatment approaches and their effectiveness.

What else can Sarcocystis be?

Sometimes, Sarcocystis can be mistakenly identified as other parasites that form cysts, like Toxoplasma or Neospora. There are also other health conditions that could be confused with muscular sarcocystosis. These include:

• Autoimmune myositis, which is inflammation of the muscles caused by the body’s own immune system
• Infective myositis due to leptospirosis, toxocariasis, or trichinellosis, all of which are infections that can cause muscle inflammation
• Rickettsial disease, which is caused by bacteria and can affect many parts of the body, including the muscles
• Toxoplasmosis, another type of parasitic infection
• Conditions caused by drugs like alcohol, cocaine, antimalarials, penicillamine, and statin
• Toxin-induced myositis, including what’s known as Haff disease, which causes muscle inflammation

It’s crucial for doctors to consider these other possibilities when trying to diagnose muscular sarcocystosis.

What to expect with Sarcocystis

Infections typically resolve on their own after a while. For most people, the discovery that they are playing host to unidentified Sarcocystis species (a type of parasite) is often unexpected. On rare occasions, the disease can spread throughout the body leading to serious health problems.

Possible Complications When Diagnosed with Sarcocystis

Sarcocystosis in the intestines can potentially lead to conditions like segmental eosinophilic enteritis or necrotizing enteritis. In some cases, muscular sarcocystosis gets severe and can result in intense muscle inflammation, known as severe myositis. Though it’s quite rare, sarcocystosis can spread and start affecting numerous organs in the body.

Common Observations in Sarcocystosis:

• Segmental eosinophilic enteritis
• Necrotizing enteritis
• Severe myositis in cases of muscular sarcocystosis
• In rare instances, the disease can spread to multiple organs

Preventing Sarcocystis

The best way to avoid getting sick is to prevent infections from happening in the first place. This is especially true when there aren’t many effective ways to treat or prevent the infection. It’s important for you to be knowledgeable about safe food handling practices. For example, properly cooking or freezing meat to kill any harmful parasites known as ‘bradyzoites’ housed in the cysts found in the meat. Fully cooking the meat makes these parasites harmless.

You should also ensure you have clean drinking water to avoid swallowing ‘sporocysts,’ another type of parasite. Boiling water is an effective way to kill them. Using chemical disinfectants like chlorine isn’t effective in eradicating these particular parasites.

Furthermore, it’s crucial to control the presence of these parasites in animals you frequently come in contact with. This can help prevent you from getting the infection.