- May 11, 2008
It is not the nematode, but its endosymbiont, Wolbachia pipientis, that causes the severe inflammatory response that leaves many blind.
It is the "chronic" extreme inflammation that causes the blindness.
Thus a temporary infection causes damage but not blindness. A chronic infection causes blindness. Would that not account as an inability of the immune system to get rid of the pathogen ?
I can understand that an immune suppression might be handy here, but only with a treatment to get rid of the bacteria.
Nevertheless, that is quite an interesting bacteria indeed.
Adult worms remain in subcutaneous nodules, limiting access to the host's immune system. Microfilariae, in contrast, are able to induce intense inflammatory responses, especially upon their death. Dying microfilariae have been recently discovered to release Wolbachia surface protein that activates TLR2 and TLR4, triggering innate immune responses and producing the inflammation and its associated morbidity. Wolbachia species have been found to be endosymbionts of O. volvulus adults and microfilariae, and are thought to be the driving force behind most of O. volvulus morbidity. The severity of illness is directly proportional to the number of infected microfilariae and the power of the resultant inflammatory response
Ocular involvement provides the common name associated with onchocerciasis, river blindness, and may involve any part of the eye from conjunctiva and cornea to uvea and posterior segment, including the retina and optic nerve. The microfilariae migrate to the surface of the cornea. Punctate keratitis occurs in the infected area. This clears up as the inflammation subsides. However, if the infection is chronic, sclerosing keratitis can occur, making the affected area become opaque. Over time, the entire cornea may become opaque, thus leading to blindness. Some evidence suggests the effect on the cornea is caused by an immune response to bacteria present in the worms.
Oh lord, i used a car analogy...
I am doomed forever... :'(