Acute muscular sarcocystosis: an international investigation among ill travelers returning from tioman island, malaysia, 2011-2012.

BACKGROUND Through 2 international traveler-focused surveillance networks (GeoSentinel and TropNet), we identified and investigated a large outbreak of acute muscular sarcocystosis (AMS), a rarely reported zoonosis caused by a protozoan parasite of the genus Sarcocystis, associated with travel to Tioman Island, Malaysia, during 2011-2012. METHODS Clinicians reporting patients with suspected AMS to GeoSentinel submitted demographic, clinical, itinerary, and exposure data. We defined a probable case as travel to Tioman Island after 1 March 2011, eosinophilia (>5%), clinical or laboratory-supported myositis, and negative trichinellosis serology. Case confirmation required histologic observation of sarcocysts or isolation of Sarcocystis species DNA from muscle biopsy. RESULTS Sixty-eight patients met the case definition (62 probable and 6 confirmed). All but 2 resided in Europe; all were tourists and traveled mostly during the summer months. The most frequent symptoms reported were myalgia (100%), fatigue (91%), fever (82%), headache (59%), and arthralgia (29%); onset clustered during 2 distinct periods: "early" during the second and "late" during the sixth week after departure from the island. Blood eosinophilia and elevated serum creatinine phosphokinase (CPK) levels were observed beginning during the fifth week after departure. Sarcocystis nesbitti DNA was recovered from 1 muscle biopsy. CONCLUSIONS Clinicians evaluating travelers returning ill from Malaysia with myalgia, with or without fever, should consider AMS, noting the apparent biphasic aspect of the disease, the later onset of elevated CPK and eosinophilia, and the possibility for relapses. The exact source of infection among travelers to Tioman Island remains unclear but needs to be determined to prevent future illnesses.

Primary lowland dipterocarp forest at Danum Valley, Sabah, Malaysia. Species composition and patterns in the understorey

The spatial distributions of species of tree ≥10 cm gbh were examined in two 4 ha plots and related to the local variation in topography and soil chemistry. The plots were similar in their species composition, particularly in terms of the densities of small trees, and they showed very similar edaphic characteristics. Size class distributions varied little within and between plots. Ordination of 0.25 ha subplots highlighted parallel gradients in the vegetation of both plots when the densities of trees ≥10 cm gbh were considered. Focusing on understorey trees in the 10-<50 cm gbh class at the 0.04 ha subplot scale showed a similar vegetation gradient in both plots closely associated with change from lower slope to ridge. No relationship with soil chemistry was found. On the ridges a special group of understorey species formed clumps and these species contributed importantly to the ordinations. Borneo has a regional history of occasionally severe droughts. It is suggested here that the observed patterns in the understorey are due to differential responses to low soil water supply, the ridges probably tending to dryness more than the lower slopes. Within the large and diverse family Euphorbiaceae, which dominates the understorey at Danum, there may be ecophysiological groupings of species. The long-term effects of disturbance interacting with local edaphic factors on forest structure and composition are discussed.

Primary forest dynamics in lowland dipterocarp forest at Danum Valley, Sabah, Malaysia, and the role of the understorey

Changes in species composition in two 4–ha plots of lowland dipterocarp rainforest at Danum, Sabah, were measured over ten years (1986 to 1996) for trees greater than or equal to 10 cm girth at breast height (gbh). Each included a lower–slope to ridge gradient. The period lay between two drought events of moderate intensity but the forest showed no large lasting responses, suggesting that its species were well adapted to this regime. Mortality and recruitment rates were not unusual in global or regional comparisons. The forest continued to aggrade from its relatively (for Sabah) low basal area in 1986 and, together with the very open upper canopy structure and an abundance of lianas, this suggests a forest in a late stage of recovery from a major disturbance, yet one continually affected by smaller recent setbacks. Mortality and recruitment rates were not related to population size in 1986, but across subplots recruitment was positively correlated with the density and basal area of small trees (10 to <50 cm gbh) forming the dense understorey. Neither rate was related to topography. While species with larger mean gbh had greater relative growth rates (rgr) than smaller ones, subplot mean recruitment rates were correlated with rgr among small trees. Separating understorey species (typically the Euphorbiaceae) from the overstorey (Dipterocarpaceae) showed marked differences in change in mortality with increasing gbh: in the former it increased, in the latter it decreased. Forest processes are centred on this understorey quasi–stratum. The two replicate plots showed a high correspondence in the mortality, recruitment, population changes and growth rates of small trees for the 49 most abundant species in common to both. Overstorey species had higher rgrs than understorey ones, but both showed considerable ranges in mortality and recruitment rates. The supposed trade–off in traits, viz slower rgr, shade tolerance and lower population turnover in the understorey group versus faster potential growth rate, high light responsiveness and high turnover in the overstorey group, was only partly met, as some understorey species were also very dynamic. The forest at Danum, under such a disturbance–recovery regime, can be viewed as having a dynamic equilibrium in functional and structural terms. A second trade–off in shade–tolerance versus drought–tolerance is suggested for among the understorey species. A two–storey (or vertical component) model is proposed where the understorey–overstorey species’ ratio of small stems (currently 2:1) is maintained by a major feedback process. The understorey appears to be an important part of this forest, giving resilience against drought and protecting the overstorey saplings in the long term. This view could be valuable for understanding forest responses to climate change where drought frequency in Borneo is predicted to intensify in the coming decades.