AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

Sarcosporidiosis (Sarcocystis infection) is caused by an intracellular protozoan parasite that predominantly affects animals. It can rarely be found in human skeletal and cardiac muscle when humans are the intermediate or accidental host. Humans can also serve as the definitive host for this parasite after ingesting the cysts in raw or undercooked beef or pork. After invasion of the GI tract, the infective sporozoites replicate and are subsequently eliminated in the stool. These oocysts are ingested by an intermediate host (eg, usually cow or pig) to complete the life cycle.

Pathophysiology

Sarcosporidiosis in humans has 2 distinct forms. In the first form, ingestion of water or food contaminated with sporocysts from the feces of a carnivore (eg, dog, wolf) is followed by sporocyst penetration of the intestinal wall. Proliferation in vascular endothelium and subsequent hematogenous dissemination leads to invasion of skeletal and cardiac muscle. These cysts subsequently disintegrate with accompanying vasculitis and fibrosis of the tissue (myositis).

The second form of sarcosporidiosis in man occurs after ingestion of meat contaminated by infective oocysts. The oocysts undergo sexual reproduction and maturation in the intestinal tract. Infective oocysts are shed into the stool (enteritis). A systemic phase and a subsequent tissue phase do not occur in this form of the infection.

Frequency

United States

Sarcosporidiosis has worldwide distribution. In the United States, more than 60 cases of muscle involvement by Sarcocystis species have been described, mostly in collections of case reports of 5-10 cases.

Since this finding is often incidental, many more undetected cases probably exist. The definitive form of sarcosporidiosis causes a self-limited nonspecific enteritis and is often not suspected clinically.

International

Most cases of human sarcosporidiosis occur in Southeast Asia. The incidence of intestinal Sarcocystis infection in Thai laborers was measured at 23%. A study of autopsy specimens of patients in Southeast Asia showed a prevalence rate of 21% in 100 consecutive patients evaluated. The seroprevalence of sarcosporidiosis in Malaysia was estimated at 19.8%.

Mortality/Morbidity

Although sarcosporidiosis can involve the heart, no deaths specifically related to its myocardial involvement have been documented. Painful muscle swellings, fever, and weakness can occur with skeletal muscle involvement. Sarcosporidiosis has not been described as causing a chronic diarrhea or malabsorptive state.

Race

The condition has no known race predilection, but most described cases have been from Southeast Asia.

Sex

The condition has no known sex predilection.

Age

The condition has no known age predilection; however, because muscle involvement clinically occurs after cyst deterioration, adults are more likely to present with skeletal muscle involvement than are children.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

Patient history in the myositic form of sarcosporidiosis includes painful muscle swellings accompanied by erythema, muscle tenderness, generalized muscle weakness, and fever. Bronchospasm can also occur. Cardiac involvement is asymptomatic, but sarcosporidiosis has been known to cause second-degree atrioventricular block in sheep.

Within a day after ingestion of contaminated beef or pork, subjects who develop the enteritis form of this infection have diaphoresis, chills, fever, vomiting, and diarrhea.

Physical

• Fever
• Muscle swelling (1-3 cm in diameter) with erythema and tenderness occur in the myositic form of sarcosporidiosis.
• Dehydration and diffuse abdominal tenderness occur in patients who ingest the oocyst.

Causes

The following persons have an increased risk of Sarcocystis infection:

• People who eat raw beef or raw pork, including raw kibbe.
• Farmers who raise cattle or pigs
• People living in poor sanitary conditions who can ingest feces contaminated with sporocysts from cattle or dogs

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Trypanosomiasis (Trypanosoma cruzi infection)

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• In intestinal Sarcocystis infection, sporulated sporocysts in freshly voided stool can be found by flotation technique. Sporocysts contain 4 sporozoites.
• A complete blood count (CBC) usually reveals eosinophilia. In cases of myositis, creatine kinase levels may be elevated.
• Polymerase chain reaction (PCR) techniques can be used to exclude Toxoplasma gondii infection.
• Indirect immunofluorescent antibody test are genus specific but not widely available.
• A muscle biopsy is diagnostic of myositis.
• Toxoplasma and Sarcocystis organisms are periodic acid-Schiff (PAS) positive; trypanosomes are PAS negative.
• Common species found in raw kibbe include Sacrocystis hominis, Sacrocystis hirsuta, and Sacrocystis cruzi.

Imaging Studies

• An x-ray of the involved extremity may identify calcified cysts of Taenia solium (ie, cysticercosis)
• CT scan or MRI of extremities may demonstrate the cysts of sarcosporidiosis, which can grow to a diameter of 5 cm.

Procedures

• Excisional biopsy in the area of the painful muscle swelling is often performed for diagnostic purposes but is not needed therapeutically.

Histologic Findings

Intact sarcocysts observed in muscle are not associated with inflammation. The sarcocysts are rather large (ie, 11 µm X 350 µm) and septate, and they can have a thick, radially striated wall. Seven distinct histopathologic types are described. The tissue form is PAS positive. After the sarcocysts disintegrate, inflammatory cells can be observed, including lymphocytes and neutrophils and an intense eosinophilic infiltrate surrounding the muscle cyst. Localized vasculitis and fibrosis of the muscle are observed.

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical Care

No specific antiparasitic agent is indicated, as Sarcocystis infection in humans represents the fully formed terminal stage of the parasite. Corticosteroids can be used to reduce the inflammation associated with muscular involvement with this parasite.

Surgical Care

Excisional biopsy in the area of the painful muscle swelling is often performed for diagnostic purposes but is not needed therapeutically.

Consultations

Consultation with an infectious disease physician and a pathologist skilled in tropical medicine is indicated.

Diet

Patients should avoid eating raw pork or raw beef. Patients should not eat food that has been contaminated by feces or dirt.

Activity

No restrictions

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Metronidazole and cotrimoxazole are reportedly being used in eosinophilic myositis, although no specific outcomes have been studied. One case report noted cure of Sarcocystis infection with use of cotrimoxazole. Corticosteroids can be used to reduce inflammation associated with muscular involvement.

Drug Category: Corticosteroids

Treat allergic and inflammatory conditions.

Drug Category: Antibiotics

Therapy must be comprehensive and cover all likely pathogens in the context of this clinical setting.

Drug Name	Metronidazole (Flagyl)
Description	Imidazole ring-based antibiotic active against various anaerobic bacteria and protozoa. Used in combination with other antimicrobial agents (except for Clostridium difficile enterocolitis).
Adult Dose	Loading dose: 15 mg/kg IV or 1 g for 70-kg adult IV over 1 h Maintenance dose (6 h following loading dose): 7.5 mg/kg or 500 mg for 70-kg adult IV infusion over 1 h q6-8h; not to exceed 4 g/d
Pediatric Dose	Administer as in adults using body weight
Contraindications	Documented hypersensitivity
Interactions	May increase toxicity of anticoagulants, lithium, and phenytoin; cimetidine may increase toxicity of metronidazole; disulfiram reaction may occur with orally ingested ethanol
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Adjust dose in hepatic disease; monitor for seizures and development of peripheral neuropathy

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Further Inpatient Care

• Patients are usually treated as outpatients.

Further Outpatient Care

• Test patients with the enteric form of the infection to document clearance of the sarcocyst from their stool. Shedding can continue for up to 6 months.

In/Out Patient Meds

• Oral corticosteroids are indicated in the outpatient setting for symptomatic inflammatory muscular involvement.

Deterrence/Prevention

• Instruct patients not to eat raw beef or pork if the risk of sarcosporidiosis is present in the community.
• Practice good food hygiene to prevent fecal-oral transmission of this parasite.
• Freezing meat to -20°C can prevent transmission.

Complications

• Dehydration
• Eosinophilic enteritis
• Ulcerative obstructive enterocolitis

Prognosis

• Sarcosporidiosis is a self-limited disease with an excellent prognosis. Rarely, eosinophilic myositis symptoms can persist for many years, recurring when further cyst wall deterioration occurs.

Patient Education

• Sarcosporidiosis is a significant food-borne zoonotic infection and is a risk in travelers to and from Southeast Asia. The patient who sheds infected oocysts in their stool can spread the infection to others through the fecal-oral route if sanitation is poor. Instruct patients not to eat raw beef or pork and to practice good food hygiene. People should understand that this infection does not necessitate routine treatment and usually is an incidental finding discovered on muscle biopsy.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Failure to recognize the infection: Sarcocystis infection may be mistaken for Toxoplasma infection, since both are PAS positive.
• Failure to provide the proper treatment: Sarcosporidiosis can be distinguished serologically and by PCR techniques, but diagnostic confusion can lead to mistreatment of Sarcocystis infection with medications designed for Toxoplasma infection.

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

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• Mehrotra R, Bisht D, Singh PA, et al. Diagnosis of human sarcocystis infection from biopsies of the skeletal muscle. Pathology. Aug 1996;28(3):281-2. [Medline].
• Pamphlett R, O''Donoghue P. Sarcocystis infection of human muscle. Aust N Z J Med. Oct 1990;20(5):705-7. [Medline].
• Pathmanathan R, Kan SP. Three cases of human Sarcocystis infection with a review of human muscular sarcocystosis in Malaysia. Trop Geogr Med. Jan 1992;44(1-2):102-8. [Medline].
• Pena HF, Ogassawara S, Sinhorini IL. Occurrence of cattle Sarcocystis species in raw kibbe from Arabian food establishments in the city of Sao Paulo, Brazil, and experimental transmission to humans. J Parasitol. Dec 2001;87(6):1459-65. [Medline].
• Piekarski G, Heydorn AO, Aryeetey ME, et al. [Clinical, parasitological and serological investigations in sarcosporidiosis (sarcocystis suihominis) of man (author''s transl)]. Immun Infekt. Aug 1978;6(4):153-9. [Medline].
• Rezakhani A, Cheema AH, Edjtehadi M. Second degree atrioventricular block and sarcosporidiosis in sheep. Zentralbl Veterinarmed A. Mar 1977;24(3):258-62. [Medline].
• Van den Enden E, Praet M, Joos R, et al. Eosinophilic myositis resulting from sarcocystosis. J Trop Med Hyg. Aug 1995;98(4):273-6. [Medline].
• Wilairatana P, Radomyos P, Radomyos B, et al. Intestinal sarcocystosis in Thai laborers. Southeast Asian J Trop Med Public Health. Mar 1996;27(1):43-6. [Medline].
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Article Last Updated: Feb 15, 2006