Sarcosporidiosis
Sarcosporidiosis is a rare parasitic infection caused by species of the genus Sarcocystis, primarily affecting the intestines or muscles of humans and nonhuman animals. The most common species associated with human infections are S. bovihominis and S. suihominis, typically contracted through the consumption of raw or undercooked beef and pork containing mature sarcocysts. Infection can lead to intestinal symptoms such as nausea, abdominal pain, and diarrhea, while muscular sarcosporidiosis is often asymptomatic but may cause muscle weakness and pain.
Although serious complications are uncommon, some individuals may experience more severe symptoms. The disease is diagnosed through fecal examinations or muscle biopsies, depending on the type of infection. Treatment often involves managing symptoms and may include antibiotics and corticosteroids for muscular forms of the infection. Preventive measures focus on thoroughly cooking or freezing meat to kill the parasites, as they can be prevalent in livestock worldwide. Awareness and proper food handling are essential to reducing the risk of sarcosporidiosis.
Sarcosporidiosis
- ANATOMY OR SYSTEM AFFECTED: Gastrointestinal system, intestines, muscles, musculoskeletal system
- ALSO KNOWN AS: Sarcocystosis
Definition
Sarcosporidiosis is a rare intestinal or muscular infection caused by various species of the genus Sarcocystis , an intracellular protozoan parasite that infects humans and, mostly, nonhuman animals. Humans may (rarely) serve as intermediate hosts or (accidentally) as definitive hosts for various Sarcocystis species that have an obligatory two-host life cycle.
Causes
There are more than one hundred species of Sarcocystis, and they have worldwide distribution. The most common species that cause sarcosporidiosis in humans include S. bovihominis and S. suihominis. Humans acquire intestinal sarcosporidiosis after eating raw or undercooked beef and pork that contain mature sarcocysts. The ingested infective sporozoites replicate and discharge in the stool as sporocysts. Once shed, sporocysts are typically ingested by an intermediate host (usually a cow or pig). Muscular sarcocystosis is probably caused by ingestion of sporocysts excreted by various definitive hosts.
Risk Factors
At increased risk of infection are persons who ingest undercooked beef or pork and persons who practice poor hand hygiene (and, thus, increase their risk of exposure to the bacteria). Human sarcosporidiosis is distributed worldwide, but most cases have been documented in Southeast Asia. Fewer than one hundred cases have been reported.
Symptoms
Infection with Sarcocystis in healthy persons causes intestinal or muscular sarcosporidiosis (based on whether the person is serving as a definitive or intermediate host). Intestinal sarcosporidiosis most commonly manifests with nausea, abdominal pain, diarrhea, and generalized myalgia. Serious complications are rare and may include dehydration, eosinophilic enteritis, and ulcerative obstructive entercolitis. Intestinal sarcosporidiosis is transient and usually self-limited. Muscular sarcosporidiosis is mostly asymptomatic and found incidentally, though painful muscle swellings, generalized muscle weakness, fever, myositis (that may persist for many years), vasculitis, or periarteritis are possible.
Screening and Diagnosis
Intestinal sarcosporidiosis can be diagnosed in the lamina propria of the small bowel and by fecal examination. Oocysts with two sporocysts or individual sporocysts in human feces are diagnostic for intestinal infection. Muscular sarcosporidiosis is diagnosed by microscopic examination of muscle biopsies.
Treatment and Therapy
Specific antiparasitic therapy for intestinal sarcosporidiosis is not indicated, as the infection in humans represents the fully formed terminal stage of the parasite. In muscular sarcosporidiosis, metronidazole and cotrimoxazole (antibacterial and antiprotozoal drugs) can be used. Corticosteroids can be used to reduce inflammation associated with muscular involvement. Persons with intestinal sarcosporidiosis will need a six-month follow-up after infection that includes testing to document the clearance of the sarcocyst from the stool.
Prevention and Outcomes
Prevention of the disease in humans consists of avoiding the consumption of raw or undercooked beef and pork. Because sarcocysts can be found in a large percentage of the world’s beef cows, and to a lesser extent in pigs, camels, sheep, horses, and other domesticated animals, all associated meat products should be properly cooked or frozen before consumption. Also, one can prevent infestation in domesticated animals by feeding them deep-frozen or processed meat products only. A person can destroy sarcocysts by cooking meat at 158° Fahrenheit (70° Celsius) for fifteen minutes, by freezing meat at 25° F (−4° C) for two days, or by freezing meat at −4° F (−20° C) for one day.
Bibliography
Fayer, Ronald. “ Sarcocystis spp. in Human Infections.” Clinical Microbiology Reviews 17 (October 2004): 894-902.
"Sarcosporidiosis." Medscape, 7 Nov. 2023, emedicine.medscape.com/article/228279-overview?form=fpf. Accessed 4 Feb. 2025.
Velásquez, J.N., et al. “Systemic Sarcocystosis in a Patient with Acquired Immune Deficiency Syndrome.” Human Pathology 39 (2008): 1263-1267.