Sarcocystosis in Travelers to Tioman Island, Malaysia

Abstract and Commentary

By Mary-Louise Scully M.D.

Dr. Scully is Director, Travel and Tropical Medicine Center, Samsun Clinic, Santa Barbara, CA.

Dr. Scully reports no financial relationships to this field of study.

Synopsis: An outbreak of suspected eosinophilic myositis secondary to Sarcocystis is reported in 32 patients who traveled to peninsular Malaysia during the summer of 2011.

Source: Centers for Disease Control and Prevention. Acute Muscular Sarcocystosis Among Returning Travelers – Tioman Island, Malaysia, 2011. MMWR 2012; 61(2):37-38.

In October 2011, GeoSentinel, the global surveillance program of the International Society of Travel Medicine, first reported on the initial findings in probable cases of sarcocystosis among travelers returning from Malaysia. With further investigation, a total of 32 suspected cases of acute muscular sarcocsytosis have now been described. In particular, all of the patients had visited Tioman Island during the summer of 2011. Approximately half of the patients were identified post-travel in Germany; others were from other parts of Europe, North America, and Asia.

All of the patients experienced fever and muscle pain, often prolonged and severe, within days to weeks of returning home. It was noted that all patients had peripheral eosinophilia and many also had elevated serum creatinine phosphokinase levels. Serological tests for trichinosis and toxoplasmosis were negative in all patients tested. One patient (of a group of 5 symptomatic patients who had traveled together) consented to a muscle biopsy, which demonstrated organisms consistent with sarcocsytosis. Similarly, another patient from a group of three that traveled together also had a positive muscle biopsy.

Sarcocystis species are intracellular protozoan parasites classified phylogeneticaly with Babesia, Plasmodium, and Coccidia such as Toxoplasma. More than 100 different species of Sarcocystis species exist worldwide and typically have a two-host life cycle based on a prey-predator (intermediate-definitive) host relationship. Humans are the definitive host for Sarcocystis hominis and Sarcocystis suihominis, acquired through eating undercooked sarcocyst-containing beef or pork, respectively. The resulting infection and sexual reproduction of the parasite in the intestine is often asymptomatic, but it may cause self-limited symptoms of acute gastroenteritis.

Alternatively, humans can serve as intermediate hosts for many of the zoonotic Sarcocystis species that are transmitted in nature. In this case, humans ingest oocysts or sporocysts in food or water contaminated with feces from an infected predator animal or reptile. After reproductive and migratory stages, the parasites ultimately disseminate to skeletal, smooth, or cardiac muscle where the formation of sarcocysts cause the classic symptoms of eosinophilic myositis, as seen in this outbreak.

Although there are fewer than 100 reports of human muscular sarcocystosis in the literature it appears that human sarcocystosis is prevalent in Malaysia. A study found sarcocysts in 21% of 100 consecutive autopsy specimens of Malaysians and a seroprevalence study also found evidence of asymptomatic infection in 20% of 243 Malaysians.1,2

Histologic examination and DNA amplification are being performed on existing muscle specimens from this outbreak to confirm the diagnosis of muscular sarcocystosis and identify the responsible Sarcocystis species.


Human sarcocystosis cases are unusual, with less than 100 cases reported thus far in the literature. However, this may change with the ever-increasing travel to higher risk areas, such as Malaysia. Tioman Island is a small island off the east coast of Peninsular Malaysia. It is a popular destination for diving and snorkeling, tourists being drawn to the crystal clear blue waters and the variety of tropical fish and marine species. Some of the islands' non-human inhabitants include very large monitor lizards and domestic cats that freely roam the island.

Epidemiologic details on this outbreak are awaited to determine if there was a common source of contaminated food or water exposure. The largest previous outbreak of eosinophilic myositis attributed to Sarcocystis occurred in seven members of a U.S. military team deployed in 1993 to rural peninsular Malaysia for a joint U.S-Malaysian civic action project.3 Several weeks after returning, the first soldier (index case) reported symptoms of fever, myositis, bronchospasm, fleeting rashes, and eosinophilia. A muscle biopsy of this patient was positive for Sarcocystis species. Six out of seven symptomatic patients also had positive serum serology for Sarcocystis. The soldiers were assigned to construct huts and irrigation sluices in a jungle village about 80 km north of Kuala Lumpur. The stay lasted only one week, but it was during seasonal monsoon rains that were particularly heavy that year. The soldiers reported extensive physical contact with the soil, including exposure to both nose and mouth, especially during recreational sporting activities in the ankle deep mud, i.e. "mud wrestling." They also reported having swum in fresh water pools, drinking untreated water, and consuming native foods, including lizard meat. All the patients had mild, self-limited illness except for the index patient who had more serious and chronic sequelae, including possible myocarditis, that appeared to respond to re-treatment with courses of albendazole.

The returning traveler with illness and eosinophilia represents a challenge to travel medicine and infectious disease physicians. Consideration of this as the causative organism in any returning ill patient with myalgia, rash, and eosinophilia is appropriate, especially if the patient is returning from Malaysia. As serology is not readily available, muscle biopsy would seem the most expedient way to make the diagnosis in a suspected case. Any new suspected cases should be reported to the CDC and the corresponding contributor of this report. Although patients often are treated empirically with albendazole and adrenal corticosteroids, there is no known effective treatment or prophylaxis for either intestinal or eosinophilic myositis secondary to Sarcocystis.


  1. Wong KT, et al. High prevalence of human skeletal muscle sarcocystosis in South East Asia. Trans R Soc Trop Med Hyg 1992; 86:631-632.
  2. Thomas V, et al. Antibodies to Sarcocystis in Malaysians. Tran R Trop Med Hyg 1978;72:303-306.
  3. Arness MK, et al. An outbreak of acute eosinophilic myositis attributed to human Sarcocystis parasitism. Am J Trop Med Hyg 1999;61:548-553.