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Query: UMLS:C0022568 (keratitis)
 5,133 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Involvement of the outer eye in Onchocerca volvulus infection is characterized by an inflammatory process around degenerating microfilariae. Individual microfilariae in the cornea may be associated with localized punctate lesions or, especially when present in large numbers, may provoke a sclerosing keratitis due to invasion by fibrovascular pannus from the limbal conjunctiva. Anterior uveitis develops in some patients and can be either granulomatous, probably as a result of direct microfilarial invasion of the iris and ciliary body, or non-granulomatous, in which case the inflammation is likely to be a response to free microfilarial antigens. Posterior segment involvement takes the form of either inflammatory or atrophic lesions, or both. It is possible that the marked atrophy of the retina and choriocapillaris seen in some cases is largely attributable to preceding choroiditis and that the optic nerve atrophy has a similar pathogenesis.
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PMID:Pathology of ocular onchocerciasis: human and experimental. 84 43

Corneal blindnesses make up a main public health problem in numerous developing countries where they constitute a sign of low sanitary level. The main diseases which cause corneal blindnesses are: Trachoma. Xerophthalmia. Measles. Corneal ulcerations and keratitis. Onchocercosis. Neonatorum ophthalmia. Leprosy. Injuries. Some therapeutic practices. Epidemiological analysis leads to the definition of risk groups: Small children. Isolated rural communities. Unhealthy urban communities. Out of place populations. Under-fed populations. Only a joint prevention can be able to fight against this social, economic, a human plague constituted by corneal blindnesses. Simple prevention measures which are often not very expensive, showed their efficiency. They are as follows: Individual and collective hygiene measures. Improvement of alimentary conditions. Earliness and quickness in ocular care. Vaccination against measles. Improvement of the care to mother and child. Sanitary education for prevention. These prevention tasks are supported by the health workers who are spread out inside the population. Their formation, the means they are granted with constitute a main priority which has to be taken into account in the choices and the decisions to be made in order to fight against blindness linked with cornea opacification with efficacy.
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PMID:Corneal blindnesses in tropical environment. 213 84

Onchocerciasis can cause severe dermal and ocular disease due, it is thought, to the events surrounding the destruction of the microfilarial stage. The evolution of papular pruritic dermatitis and punctate keratitis is clearly related to the killing of microfilariae. Other more chronic changes such as dermal and epidermal atrophy are probably due to repeated episodes of microfilarial killing. It is common to find that not all patients are, at any one time, mounting clinically obvious destructive host responses against the microfilariae, and such individuals can carry very high loads of parasites without any apparent adverse effects. The immunological basis of the differences between these types of patients forms one of the most important questions in the pathogenesis of onchocerciasis today. Various explanations are now emerging. These include immunosuppressive factors and variation in the form of Onchocerca volvulus antigens presented to the host. Clinical presentations of this disease appear to reflect variations in host responses and can be used to provide information concerning the protective immune responses an individual can mount against this parasite.
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PMID:Clinical responses in human onchocerciasis: parasitological and immunological implications. 329 60

Hartley guinea pigs were injected with microfilariae (Mf) of Onchocerca lienalis as a model for acute inflammatory responses to Mf in human Onchocerca volvulus infection. IgG autoantibody reactive with a 3 M KCl extract of guinea pig cornea was detected by ELISA in the serum of guinea pigs injected with O. lienalis Mf three or more times sub-conjunctivally, or two or more times subcutaneously. Administration of the microfilaricides diethylcarbamazine citrate and ivermectin did not alter the proportion of animals expressing autoantibody or the mean autoantibody titer. The severity of acute corneal inflammatory reactions to Mf was similar in animals with and without circulating autoantibody. Although autoantibody responses did not correlate with acute corneal inflammatory reactions to dead Mf, the ability of Mf to induce formation of an antibody reactive with a component of autologous cornea suggests that autoimmune mechanisms might participate in chronic onchocercal lesions in the cornea, eg, sclerosing keratitis.
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PMID:Autoantibody induced by experimental Onchocerca infection. Effect of different routes of administration of microfilariae and of treatment with diethylcarbamazine citrate and ivermectin. 336 73

Onchocerca volvulus infection of the residents of two villages in the Upper Atbara River region of Sudan (63.4% prevalence) was found to be medically and socially significant with a remarkable degree of pruritus and dermal pathology present. The severest skin changes, which were often confined to certain areas of the body, were most common in the teenage group (13-19 years). Quantitation of the clinical changes showed that the most severe alterations were present in patients with the lower levels of microfilariae in the skin (0.1-6 mf mg-1) rather than in those with higher levels. Nodules containing adult O. volvulus were found in many individuals, and often in clusters in older patients. Major losses of vision due to O. volvulus were not found, although microfilariae were frequently seen in the cornea and anterior chamber. The commonest corneal change was punctate keratitis, and this was most frequently seen in the teenage group. Trachomatous changes of eyelids and corneas were also seen. The prevalence values of O. volvulus infection in the two villages were significantly increased when, in addition to microfilarial presence in skin biopsies, onchocercal signs such as punctate keratitis, nodule presence and microfilariae in the anterior chamber were taken into consideration. This illustrates the need to consider factors other than skin snip parasitology in obtaining a diagnosis. This study also emphasizes the degree of severity that onchodermatitis can reach and that low levels of dermal microfilariae can be accompanied by very extensive skin changes without any loss of vision. The necessity of considering the severity of skin changes when defining tolerable levels of onchocerciasis in a community is discussed.
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PMID:Severe onchocercal dermatitis in the Ethiopian border region of Sudan. 344 29

The prevalence, intensity and clinical manifestations of onchocerciasis were investigated in three village communities along the Bahr El Arab and its tributaries in Southern Darfur, Western Sudan. Onchocerca volvulus has not been reported from this region before. Over 300 people were examined and the selection of patients was aimed at obtaining a cross-sectional view of the disease at all ages and in both sexes. Prevalence rates were high (67.5%, 28.6% and 32% in Titribi, Radom and Kafia Kingi, respectively). The intensity of infection in young adults was generally about 30 mf/mg, but ranged up to 100 mf/mg. Infections were detected in subjects as young as two years old; about one quarter of those sampled in Titribi had nodules, mostly in the pelvic region. Clinical signs of acute and chronic dermal changes were especially marked in Titribi. This village was located closest to the breeding sites, which appear in the rainy season only. More than a third of those samples had severe pruritus and showed many self-inflicted excoriations. Both anterior and posterior eye segment changes were detected in each community, and cases of onchocercal blindness were attributed to sclerosing keratitis and to optic and chorioretinal atrophy. One case typical of intensely localized disease was seen, where the affliction was unilateral and severe with oedema and pigment changes, but very few microfilariae present. Onchocerciasis appears to be well established in this region and has apparently caused abandonment of some settlements in recent years.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Onchocerciasis in Sudan: the Southern Darfur focus. 360 40

Onchocerciasis is a leading cause of blindness in equatorial Africa and in endemic regions in Central America. Understanding of the pathologic processes involved in onchocercal eye disease and of the role of immunopathologic mechanisms in its development has been substantially limited by the shortage of eyes for histologic study and by the lack of a naturally occurring animal model. The inoculation of microfilariae of Onchocerca species into the eyes of laboratory animals may reproduce selected aspects of onchocercal eye disease, such as punctate keratitis. Studies in these models support the hypothesis that immunopathologic mechanisms mediated by IgE antibody are involved in the development of ocular lesions. In some laboratory animal models, diethylcarbamazine citrate, a microfilaricidal drug that causes severe inflammatory reactions to microfilariae in humans, increases the severity of ocular lesions, and stimulates IgE antibody responses. Laboratory animal studies are potentially highly useful for understanding the immunopathogenesis of ocular onchocerciasis.
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PMID:Onchocerciasis: experimental models of ocular disease. 407 Sep 20

Diethylcarbamazine (DEC) therapy for Onchocerca volvulus infection results in frequent ocular and systemic complications, but the pathogenesis of these complications is unclear. Twenty men with O. volvulus infection were treated over a period of six months with DEC given daily for one week and weekly thereafter. Major systemic and ocular complications included proteinuria, severe pruritus, visual field constriction, optic nerve pallor, chorioretinitis, anterior uveitis, and punctate keratitis. Levels of circulating immune complexes (CICs) were increased (greater than 11% [125I]C1q binding) in 14 of the 20 men prior to treatment. Persons with pretreatment C1q binding activity of greater than 30% were at increased risk to develop constriction of visual fields (P less than 0.05) and proteinuria (P less than 0.015). Linear regression analysis revealed a striking correlation between pretreatment levels of CICs and the total number of both systemic and ocular complications (P less than 0.001) and ocular complications alone (P less than 0.005). These results suggest that CICs may be important in the pathogenesis of the delayed systemic and ocular complications following DEC therapy for O. volvulus infection.
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PMID:Ocular and systemic complications of diethylcarbamazine therapy for onchocerciasis: association with circulating immune complexes. 684 23

An evaluation of the effects on onchocerciasis of a 3-year period of vector control was undertaken during 1978 in the Onchocerciasis Control Programme area in West Africa. The results revealed that the overall prevalence of ocular onchocerciasis showed only a slight decrease at the follow-up in 1978, but that there was significantly less infection among children in the age group 5-14 years as compared with 1975. There was a total incidence of ocular signs of onchocerciasis of 8.6% over the 3 years, but also a disappearance of those signs in 11.7% of the sample examined. The incidence of severe onchocercal eye manifestations was low, compared with similar areas of uncontrolled transmission. The particularly low incidence of sclerosing keratitis may be associated with the finding of a significantly decreased microfilarial load in the cornea, whereas the number of living microfilariae in the anterior chamber of the eye was apparently unchanged. The incidence of blindness due to onchocerciasis was low and confined to individuals who already presented severe eye manifestations of the disease before the beginning of the vector control campaign.
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PMID:A three-year follow-up of ocular onchocerciasis in an area of vector control. 696 41

Corneal inflammation (keratitis) is a major cause of visual impairment in Onchocerca volvulus infection. Previous studies showed that onchocercal keratitis can be induced in mice following s.c. immunization and intracorneal injection with soluble O. volvulus Ags (OvAg), and that the inflammatory response is dependent on T cells and IL-4. Since recombinant IL-12 impairs IL-4-dependent, Th2-mediated responses in other parasitic infections and in models of allergic asthma, the present study was undertaken to determine the effect of IL-12 on onchocercal keratitis. Mice were injected i.p. with IL-12 or saline at the time of initial sensitization to OvAg. Surprisingly, IL-12 treatment caused significant exacerbation of corneal pathology, which was associated with increased eosinophil and mononuclear cell infiltration into the corneal stroma. Consistent with the well-documented effect of IL-12 on Th1 cell development, corneas of IL-12-treated animals had elevated expression of the Th1 cytokine IFN-gamma and diminished expression of the Th2 cytokines IL-4, IL-5, IL-10, and IL-13. However, corneas from these animals also had marked elevation of alpha- and beta-chemokines known to be active on eosinophils and mononuclear cells, including IFN-gamma-inducible protein (IP)-10, macrophage inflammatory protein-1alpha, macrophage inflammatory protein-1beta, JE/monocyte chemotactic protein-1, RANTES (regulated upon activation, normal T expressed and secreted), and eotaxin. Together, these data indicate that IL-12 exacerbates OvAg-mediated corneal pathology by enhancing chemokine expression and recruitment of inflammatory cells.
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PMID:IL-12 exacerbates helminth-mediated corneal pathology by augmenting inflammatory cell recruitment and chemokine expression. 899


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