Tropical pyomyositis in eastern Ecuador

90 TRANSACT[ONSOF

Tropical

THE ROYAL SOCKTVOFTROPICAL

pyomyositis

Kevin R. Kerrigan’

MEDICINEAND

in eastern

andStephen J. Nelson

HVGCENE (1992)

86,90-91

Ecuador Hospital Vozandes Or-iente, Shell, Pastaza, Ecuador Abstract

In the ten year period 1980-1989,97 patientswere treatedfor tropical pyomyositisat Hospital Vozandes Oriente in easternEcuador, accountingfor 2.2% of surgicaladmissions.Operation recordsfrom an affiliated hospitalin Quito showedthat, high on the Andeanplateau,pyomyositisaccountedfor only 0.1% of surgicaladmissions.Among the patient populationof Ecuador’seasterntropical rain forest, personswho weremembersof an indigenousethnic groupwereaffectedwith pyomyositistwice asoften aswould be expectedfrom their representationin the generalpopulation. Results

Introduction

Tropical pyomyositisis a disease characterizedby the apparentlyspontaneous appearance of bacterialabscesses within the fascialboundariesof skeletalmuscles. Staphybcoccus aureus is the organismisolatedfrom the overwhelming majority of cases.Although sporadiccases have been reported from temperateregions(GIBSON et al., 1984).,the vast majority of cases occur in the tropics. The preciseetiology of tropical pyomyositisremainsundetermined.It is generallyheld that the bacteriagainaccessto the musclevia a haematogenous route, but the fundamentalquestionis how a tissuewhich is normally very resistantto bacterialinfection (SMITH& VICKERS, 1960)shouldbe renderedsusceptibleto abscess formation. A variety of conditionscommonto the tropics has been investigated as possibleaetiologicalagentsand found wanting (FOSTER,1965;BURKITT,1947). As shown by MIYAKE (1904), if skeletal muscleis damagedmechanicallybefore the occurrenceof bacteraemia,abscess formation doesoccur in the traumatized muscle, However, implication of gross mechanical trauma asan aetiologyfor pyomyositisdoeslittle to explain its tropical distribution. The concept, first proposed by ANAND & EVANS (1964), that antecedent arthropod-borneviral infection may be the agentwhich damagesskeletalmuscleis supportedby both epidemiological (HORN & MASTER,1968; FANNEYet al., 1982) andhistologicalevidence(TAYLOR~~al., 1970,1976). Although tropical pyomyositiswasfirst reportedfrom Jamaica(SCOTT,1912),very little informationpertaining to its occurrencein tropical America hasappearedsince then. The current paperis intendedto report the experiencewith tropical pyomyositisobtainedat a singlemedical institution in easternEcuador. Hospital Vozandes Oriente (HVO) is located on the slopesof the Andes mountainsat an altitude of 1000 m. HVO servesas a primary and referral health care facility for the population of-Ecuador’seasternjungle, or Oriente, which consistsof about 15000 km Cnearlv6000sauaremiles1of tropical rain forest. The popula;on, approximately200 000, is comprised

of persons belonging

to one of 3 dis-

tinct indigenousgroupsaswell asthoseof mixed Spanish andindigenousdescent. Materials

and Methods

The in-patient and emergencydepartmentrecordsat HVO for 1980-1989were screenedand the chartsof all patients with a diagnosisof abscess were reviewed. All casesdocumentedashavingan abscess within the fascial boundaries of skeletal muscle were included in the study. Patientswhoseabscesses werecausedby penetrating injury and those who, concommitantly or subsequently, were found to have osteomyelitiscontiguous with the abscesscavity were excluded from the study. Ninety-sevencaseswerethusselected. *Enen;

address:

KijabeMedicalCentre,P.O. Box20,Kijabe,

Incidenceand seasonal variation Eighty-three of the 97 casesselectedwere admitted to the hospital,while the remaining 14 were treated as outpatients.The 83hospitalpatientsrepresented2.2% of all surgicaladmissions to HVO during the period of study. 63%of all casesoccurredduring the first 6 monthsof the year. June, the month of highestrainfall in Oriente, was alsothe month with the greatestnumberof casesof pyomyositis. Climate and altitude

All but one of the 97 patientswith pyomyositislived in areasclassifiedastropical, lessthan 1800 m abovesea levelwith year-roundtemperaturesof 18”-28°C. Randomsamplingof 250 patients admitted to HVO during the period of this study showedthat 96%of these patients without pyomyositis alsolived at altitudes of lessthan 1800 m. The incidenceof pyomyositisat HVO was compared with that at an affiliated hosuital. Hosuital VozandesQuito (HVQ), located 3000 & abcwe sea level. Nearly 5000post-operativediagnoses of patientsoperatedupon at HVQ during a 4 year periodcoincidentwith the study period werereviewed. Of these,only 3 confirmed and 2 possiblediagnoses of pyomyositiswerefound. Age and sex distribution

Seventy-three percent of casesoccurred among patients in their first 2 decadesof life. There were 70% more patientswith pyomyositisin the agegroup 10-19 yearsthan would have beenexpectedfrom their representationin the generalpopulation. All other agegroups were representedslightly lessthan their representation in the generalpopulation. Fifty-eight patients were male and 39 female, a male:femaleratio of 1.5: 1. Distributionby ethnic group Sixty-four patients(66%)were membersof one of the indigenousgroups of the region. The remaining onethird were of mixed Spanishand indigenousdescent. This distribution of patientswith pyomyositiswascomoaredwith that found in a random samoleof 250medical admissions,and another 250 surgicaladmissionsto HVO during the sameperiod (Table). Table.Distribution of cases of tropicalmyositis by ethnicgroup Medical Indigenous Non-indigenous Totals

50 (20%) 200 (80%) 250 (100%)

Admissions Surgical 72 (29%) 178 (71%) 250 (100%)

Pyomyositis 64 (66%) 33 (34%) 97 (100%)

To investigatefurther this apparent predilection for indigenouspeople, we consideredonly those patients from the province of Morona-Santiago,where moreprecise demographicdata were available. The populated portion of this province is situatedalmostentirely within

91 an area of high risk for pyomyositis (i.e., <1800 m elevation). Statistics from the 1982 government population census showed that 45% of the 67 000 inhabitants of this province were indigenous persons. However, of the 44 cases of pyomyositis from Morona-Santiago province, 37 (84%) occurred in indigenous people. of multiple abscesses Eighty-three patients (85%) presented with a single abscess confined to one anatomical site. Ten patients had abscesses in 2 anatomical locations, 2 patients in 3 sites, and 2 patients in 4 anatomical sites. Thus, there was a total of 117 abscesses among the 97 patients.

Frequency

Distribution

by anatomical

site

The lower extremity, primarily the large muscle groups of the thigh, accounted for the majority of the abscesses in our patients. Sixty-one of the 117 abscesses (52%) occurred on the lower extremity, 46 cases (40%) on the trunk, and 10 cases (8%) on the upper extremity. Of the cases occurring on the trunk, 11 abscesses originated in the psoas muscle, making pyomyositis the Ieading cause of psoas abscess at our hospital.

Clinicalpresentation

The presenting complaint in all patients was pain at the site of abscess. Only 21% gave a history of antecedent trauma to the affected part. The average time delay between onset of symptoms and arrival at our hospital was 14 d (range 3-60 d). On physical examination at the time of admission, 95% of natients were found to have a oalnable mass: 80% were febrile, and 15% demonstrated-in&eased temperature of the skin overlying the mass. Erythema and fluctuance were each found in only 9% of cases.

References

Anand, S. V. & Evans, K. T. (1964). l’yomyositis. BritishJournal ofSurgen/.

51.917-920.

Ashken, My ii. & Cotton, R. E. (1963). Tropical skeletal muscle abscesses.BritishJournal of Surgery, 50, 846-852. Burkitt, R. T. (1947). Tropical pyomyositis.Journal of Tropical Medicine

and Hygiene,

Aerobic bacterial cultures of abscess contents were obtained either by aspiration or at the time of surgical drainage in 76 cases. Staphylococcus was isolated in pure culture from all of these, and all but 3 isolates were characterized as Staph. aureus. and mortality

Ten complications occurred in 9 of the patients. Six patients required a second surgical procedure to provide better drainage for an inadequately drained abscess. Septic arthritis adjacent to the site of pyomyositis occurred in 2 patients. In both cases, the time course was such that the septic arthritis was clearly a complication and not the aetiology of the pyomyositis. Endocarditis and staphylococcal empyema occurred in one patient each. Discussion The occurrence of pyomyositis among 3-4% of surgical admissions to Mulago hospital in Uganda reported by HORN & MASTERS (1968) is the highest rate reported anywhere in the world. The finding in our study of pyomyositis accounting for 2’2% of surgical admissions indicates that pyomyositis is nearly as frequent a problem in the eastern rain forest of Ecuador as it is in Uganda. The disease as seen in our study population appeared to be both epidemiologically and clinically identical to that reported from other areas of the tropics. Our study differs from prior reports from other areas of the world with regard to predilection for pyomyositis based on ethnic group. There has been very little agreement on this point in previous studies of the disease. HORN & MASTERS (1968) reported that pyomyositis in East Africa was ‘almost entirely confined to the in-

50,71-75.

Fanney, D., Thomas, L. C. & Schwartz, E. (1982). An outbreak of pyomyositis in a large refugee camp in Thailand. AmericanJournal 135.

Bacteriology

Morbidity

digenous population’. However, ROBIN (1961), in Malaya, reported the occurrence of pyomyositis among Europeans living in the tropics. ASHKEN & COTTON (1963), also reporting from Malaya, showed that ethnic groups from high altitudes where pyomyositis was virtually nonexistent were subject to the disease while living in hot, humid climates. This observation was confirmed by SMITH et al. (1978), who found that people immigrating to Uganda from the highland regions of Ruanda and Burundi ‘appear to suffer tropical myositis equally with the indigenous Baganda’. These same investigators, in reporting the relative incidence of pyomyositis among various ethnic groups in Uganda, found ‘an apparent excess of patients from the Ganda ethnic group’. MARCUS & FOSTER (1968), also reporting from Uganda, had earlier found that the ‘incidence in the Kampala area among the different tribes corresponds closely to their relative proportions to the general population’. In the present study, pyomyositis occurred approximately twice as often among indigenous peoples in Morona-Santiago province as would be expected from their representation in the general population. Whether the explanation for this finding is related to genetic predisposition, altered immunological response, nutritional or hygienic factors, or to some other factor, is subject for further study.

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Medicine

and Hygiene,

31, 131-

Foster, W. D. (1965). The bacteriology of tropical myositis in Uganda. Journal of Hygiene, 63,5 17-5 14. Gibson. R. K.. Rosenthal. S. 1. & Lukert. B. I’. 11984). Pvomyoiitis: increasing recognition in tempe;ate clirnates.‘Am&L canJournal of Medicine, 77,76&772. Horn, C. V. & Master, S. (1968). Pyomyositis tropicans in Uganda. East A ftican Medical.7oumal,45,463-471. Marcus, R. T. & Foster, W. D. (1968). Observations on the clinical features, aetiology and geographical distribution of pyomyositis in East Africa. East African Medical3ouma1, 45, 167-176. Miyake, H. (1904). Beitrage zur Kenntis der sogennanten Myositis mfectiosa. Mitteilungen aus den Grenzgebieten der Medizin und Chirurgia, 13, 155-198. Robin, G. C. (1961). Tropical myositis in Malaya. Journal of Tropical Medicine and Hygiene, 64,288-291. Scott, H. H. (1912). Deep suppuration of the thigh associated with a peculiar bacillus. Journal of Tropical Medicine and Hygiene, 15,97. Smith, I. M. & Vickers, A. B. (1960). Natural history of 338 treated and untreated patients with staphylococcal septicaemia. Lancet, i, 1318-1322. Smith, P. G., Pie, M. C., Taylor, E. & Taylor, J. F. (1978). The epidemiology of tropical myositis in the Mengo districts of Uganda. Transactions of the Rgval Society of Tropical Medicine and Hygiene, 72,46-53. Taylor, J, F., Templeton, A. C. & Henderson, B. (1970). Pyomyositis: a clinicopathological study. East Aftican Medical Journal, 47,493-501. Taylor, J. F., Fluck, D. & Fluck, D. (1976). Tropical myosiris: ultrastructural studies. Journal of Clinical Pathology, 29, 1081-1084. Received publication

12 April 24July

1991; revised 1991

1SJuly

1991;

accepted

for