The Onchocercal Nodule: Interrelationship of Adult Worms and Blood Vessels

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  • Department of Infectious and Parasitic Disease Pathology and the World Health Organization Collaborating Centre for the Histopathology of Filarial Diseases in Man, Armed Forces Institute of Pathology, Washington, DC 20306-6000
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This study of onchocercal nodules reveals an intimate relationship between the cuticle of Onchocerca volvulus and the capillaries of the host. Perfusion of blood vessels with India ink and other special techniques reveal a proliferation of capillaries around the worms and communication between small vessels and the spaces around the worms. The space around the worm is continuous with the central fibrin lake. These findings, together with the fact that the worm's gut contains hemosiderin, suggest that the worm subverts the vascular reaction and causes within the nodule a controlled hemorrhage that serves the worm's nutritional needs. We believe this explains, in part, how worms survive in fibrous nodules for many years.