The epidemiology of melioidosis in Papua New Guinea

Warner, Jeffrey Mitchell (2004) The epidemiology of melioidosis in Papua New Guinea. PhD thesis, James Cook University.

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Abstract

Melioidosis has only been sporadically reported in PNG and its contribution to the disease burden of Papua New Guineans has been questioned. The rural district of Balimo, located within the Aramia flood plain of the Western province, was chosen to test the hypothesis that melioidosis is under recognised in rural PNG due to a lack of clinical awareness and a poorly resourced laboratory sector. A prospective clinical screening program conducted at Balimo Health Centre revealed melioidosis as the cause of a previously recognised fatal febrile illness affecting children. The implementation of diagnosis and treatment protocols reduced the apparent case fatality rates from 100% to 45%. Although case numbers were small, features of melioidosis in this community include childhood predilection (average age 12-years), a lack of traditional co-morbidity and regional clustering. Simple methods of isolate identification were tested against gold standards of phenotypic and genotypic techniques and found to be sensitive and sustainable. An IHA serological study of 747 children demonstrated a correlation between sero-reactivity and clinical incidence. Furthermore, selective culture of 374 soil samples taken from the environment within this region revealed autochthonous B. pseudomallei from village communities demonstrated to be melioidosis endemic. Of the 191 samples taken from areas within these villages where children play, 3.7% were found to harbour the organism. DNA macro restriction analysis demonstrated clonality between clinical and environmental strains further substantiating the hypothesis that a driver of childhood predilection is behaviour typical of children which encourages exposure to B. pseudomallei from permanently saturated soil and/or water, most likely through preexisting abrasions or pernasal inoculation. A lack of genetic diversity of B. pseudomallei revealed by DNA macro restriction analysis is a feature. This may represent recent importation or the comfortable niche of environment - host cycling of this virulent saprophyte. This is in contrast to the diversity demonstrated in the analysis of the avirulent PNG derived B. thailandensis. In a geographical analysis of the Balimo region, the environmental attributes of low altitude (<600 m), inundation and extent of inundation and hydraquents as the predominate soil type are typical of this melioidosis implicated region. The subsequent mapping of PNG in terms of these attributes revealed only isolated regions which share these features. If the rare reports of melioidosis elsewhere in PNG is an accurate reflection of the national burden of the disease, these environmental attributes may represent important biogeographical boundaries for melioidosis in PNG. These data may serve in the remote sensing of melioidosis in PNG and throughout the Pacific-Australasian region.

To further substantiate the importance of these geographic boundaries, an indirect IgG ELISA-based sero-epidemiological assay was developed using antigen derived from PNG B. pseudomallei and used on samples taken from individuals from 16 regions throughout PNG. The assay was able to detect sero-reactivity that was dependent on region which varied according to degrees of melioidosis prevalence. The true sero-prevalence ranged from 0 - 55%, demonstrating significant spatial sero-clustering. Further, when regions were classified into risk-localities based on sero-reactivity, a correlation was revealed between regions determined high-risk by population sero-reactivity and biogeography.

A prospective study in Port Moresby where 3561 samples were selectively screened for B. pseudomallei demonstrated melioidosis to be endemic in the empirically diagnosed tuberculosis (TB) patient cohort and patients presenting with sepsis associated type 2 diabetes, although the incidence is low. In demonstrating endemic melioidosis in rural PNG for the first time, it is hoped this work will contribute to decreasing the fatality rates of pneumonia and sepsis in this rural subsistence community and may aid in the uncovering of the submerged iceberg that is melioidosis within this region.

Item ID: 1278
Item Type: Thesis (PhD)
Keywords: Melioidosis, Burkholderia pseudomallei, Balimo, Papua New Guinea, Diagnosis and treatment protocols, Childhood predilection, Lack of traditional co-morbidity, Regional clustering, Simple methods of isolate identification, Correlation between sero-reactivity and clinical incidence, Autochthonous B. pseudomallei, Clonality between clinical and environmental strains, Lack of genetic diversity, Low altitude, Inundation, Hydraquents, Biogeographical boundaries, Indirect IgG ELISA-based sero-epidemiological assay, Spatial sero-clustering, Correlation between sero-reactivity and biogeography, Tuberculosis, Sepsis associated type 2 diabetes, Endemic melioidosis in rural PNG, Aramia flood plain, Western province
Date Deposited: 28 Nov 2006
FoR Codes: 11 MEDICAL AND HEALTH SCIENCES > 1117 Public Health and Health Services > 111706 Epidemiology @ 34%
11 MEDICAL AND HEALTH SCIENCES > 1108 Medical Microbiology > 110801 Medical Bacteriology @ 33%
06 BIOLOGICAL SCIENCES > 0603 Evolutionary Biology > 060302 Biogeography and Phylogeography @ 33%
SEO Codes: 92 HEALTH > 9201 Clinical Health (Organs, Diseases and Abnormal Conditions) > 920109 Infectious Diseases @ 100%
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