75 research outputs found
Osteogenic tumour in Australopithecus sediba: Earliest hominin evidence for neoplastic disease
We describe the earliest evidence for neoplastic disease in the hominin lineage. This is reported
from the type specimen of the extinct hominin Australopithecus sediba from Malapa, South Africa,
dated to 1.98 million years ago. The affected individual was male and developmentally equivalent
to a human child of 12 to 13 years of age. A penetrating lytic lesion affected the sixth thoracic
vertebra. The lesion was macroscopically evaluated and internally imaged through phase-contrast
X-ray synchrotron microtomography. A comprehensive differential diagnosis was undertaken
based on gross- and micro-morphology of the lesion, leading to a probable diagnosis of osteoid
osteoma. These neoplasms are solitary, benign, osteoid and bone-forming tumours, formed from
well-vascularised connective tissue within which there is active production of osteoid and woven
bone. Tumours of any kind are rare in archaeological populations, and are all but unknown in
the hominin record, highlighting the importance of this discovery. The presence of this disease
at Malapa predates the earliest evidence of malignant neoplasia in the hominin fossil record by
perhaps 200 000 years.NCS201
New fossil remains of Homo naledi from the Lesedi Chamber, South Africa
The Rising Star cave system has produced abundant fossil hominin remains within the
Dinaledi Chamber, representing a minimum of 15 individuals attributed to Homo naledi. Further
exploration led to the discovery of hominin material, now comprising 131 hominin specimens,
within a second chamber, the Lesedi Chamber. The Lesedi Chamber is far separated from the
Dinaledi Chamber within the Rising Star cave system, and represents a second depositional context
for hominin remains. In each of three collection areas within the Lesedi Chamber, diagnostic
skeletal material allows a clear attribution to H. naledi. Both adult and immature material is present.
The hominin remains represent at least three individuals based upon duplication of elements, but
more individuals are likely present based upon the spatial context. The most significant specimen is
the near-complete cranium of a large individual, designated LES1, with an endocranial volume of
approximately 610 ml and associated postcranial remains. The Lesedi Chamber skeletal sample
extends our knowledge of the morphology and variation of H. naledi, and evidence of H. naledi
from both recovery localities shows a consistent pattern of differentiation from other hominin
species.SP201
Reciprocal regulation of fat content and flight activity in male tsetse flies (Glossina palpalis)
The feeding behaviour, activity and trappability of wild female Glossina pallidipe in relation to their pregnancy cycle
Population dynamics and density-dependent seasonal mortality indices of the tick Rhipicephalus appendiculatus in eastern and southern Africa
Towards a general rule for estimating the stage of pregnancy in field-caught tsetse flies
The basic reproduction number for complex disease systems: defining Ro for tick-borne infections
Characterizing the basic reproduction number, R(0), for many wildlife disease systems can seem a complex problem because several species are involved, because there are different epidemiological reactions to the infectious agent at different life-history stages, or because there are multiple transmission routes. Tick-borne diseases are an important example where all these complexities are brought together as a result of the peculiarities of the tick life cycle and the multiple transmission routes that occur. We show here that one can overcome these complexities by separating the host population into epidemiologically different types of individuals and constructing a matrix of reproduction numbers, the so-called next-generation matrix. Each matrix element is an expected number of infectious individuals of one type produced by a single infectious individual of a second type. The largest eigenvalue of the matrix characterizes the initial exponential growth or decline in numbers of infected individuals. Values below 1 therefore imply that the infection cannot establish. The biological interpretation closely matches that of R(0) for disease systems with only one type of individual and where infection is directly transmitted. The parameters defining each matrix element have a clear biological meaning. We illustrate the usefulness and power of the approach with a detailed examination of tick-borne diseases, and we use field and experimental data to parameterize the next-generation matrix for Lyme disease and tick-borne encephalitis. Sensitivity and elasticity analyses of the matrices, at the element and individual parameter levels, allow direct comparison of the two etiological agents. This provides further support that transmission between cofeeding ticks is critically important for the establishment of tick-borne encephalitis
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