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The text is the summary of recent articles on Sowda at 75 thresold from National Library of Medicine (NLM). This information is subject to NCBI's Disclaimer and Copyright notice.


A national control programme with goals to eliminate onchocerciasis has yet to be launched due to the current upheaval and social unrest in the country [1]. Adoption of ivermectin use at three-month intervals as a control strategy has not been evaluated because the drug is mostly used in clinics and distributed to only a few affected communities [2]. This paper addresses key aspects of onchocerciasis in Yemen and highlights the need for screening at-risk populations using highly sensitive techniques and mapping the distributions of the parasite in human and vector populations of blackflies [3]. We investigated whether hyperreactivity was reflected by lower local TGF-β production, analysing stable latent TGF-β1 expression in onchocercomas, lymph nodes and skin from hyperreactive and hyporeactive patients by immunohistochemistry [4]. TGF-β was weakly and less frequently expressed by various cell types in onchocercomas, skin and lymph nodes from hyperreactive compared to hyporeactive patients [5].

This applied to reactions around living and dead Adult worms as well as dead microfilariae [6]. Antigen-presenting cells strongly expressed HLA-DR in both forms, but their numbers were reduced in hyperreactive Nodules [7]. Plasma Cells produced more IgE and IgG1, but less of the anti-inflammatory Antibody IgG4 in hyperreactive onchocercomas [8]. We investigated the cellular composition of secondary lymph follicles in Subcutaneous Nodules from eight patients with hyperreactive onchocerciasis (synonymous "localised" form or sowda) using immunohistology [9]. Few of the B Cells were labelled for IgG1, IgG2 and IgG4, whereas in other zones of the nodule IgG1 was expressed by plasma Cells and IgG1-coated dead microfilariae [10].

The Lesion was characterized by a sever papule Dermatitis Localized to the lower limbs, with marked skin darkening [11]. There was extensive follicular Hyperplasia of the regional lymph nodes in two cases only [12]. The skin snips taken from the three patients were positive microfilariae [13]. Following several missions of bio-clinical and epidemiological evaluations in neighbouring villages of wadis, it has been possible to study different clinical aspects: one reminding the classical african onchocerciasis with Generalized and diffused Dermatitis, and, on an other Hand, a hyperreactive Dermatitis on one side of the body and associated with a collateral lymphatic ganglion [14]. Frequent eye lesions of the West African onchocerciasis are not found in sowda cases [15].

In classical optical Microscopy, microfilaria is morphologically indifferenciable between sowda and onchocerciasis clinical aspects [16]. This phase was followed by hybridisation of amplification products by PCR to specific stains: OVS-2 for Onchocerca volvulus species, OCH for Onchocerca ochengi, PFS1 and PSS1-BT respectively for the forest strain and the savannah strain of Onchocerca volvulus as described previously [17]. The second one corresponds to 2 patients with less than 5 microfilaria in their snip-test [18]. It seems quite probable that the clinical picture of sowda be the result of developing onchocerciasis of animal origin and not identified as to day [19]. The ivermectin, therapeutic of choice for African onchocerciasis in annual unique cure seems less effective in the coverage of sowda [20].

The aim of this study was to investigate a possible association of a variant of the IL-13 gene, which confers an IgE-independent risk for asthma and atopy, with the immunologically hyper-reactive sowda form of onchocerciasis [21]. sowda patients had higher IgE levels than those with Generalized onchocerciasis [22]. Volvulus who exhibited either a hyperreactive or a Generalized form of onchocerciasis and in persons with no filarial infections [23]. Volvulus-negative Africans coinfected or infected with intestinal nematodes (hookworm and/or Ascaris lumbricoides) revealed higher serum granule protein concentrations and/or absolute Eosinophil counts and urinary ECP than those without nematode infections [24]. Statistical differences between both sections were found for the absolute Eosinophil counts and for serum EDN/EPX and IgE in Generalized onchocerciasis, and for urinary ECP in sowda, indicating stimulation of the Eosinophil potential of O [25].

From these results it is concluded that in nematode diseases, ECP and EDN/EPX levels reflect the degree of antigenic stimulation, Eosinophil activation and Eosinophil turnover rates [26]. For further characterization of the immune response, the localization and frequency of mast Cells in onchocercomas from untreated and ivermectin-treated patients with hyperreactive onchocerciasis from Liberia and the Yemen were analysed and compared to the Generalized form by immunohistochemistry with Antibodies specific for human mast cell tryptase and chymase, histamine and IgE [27]. Throughout the nodular tissue of the hyperreactive form, mast Cells accumulated in the strong inflammatory infiltrates, especially near Eosinophils and around cellular attacks on microfilariae as well as perivascularly [28]. Their Number was significantly higher in the whole Nodular tissue compared to the Generalized form [29]. No mast Cells were observed in the Cystic parts or attached to Adult worms or microfilariae [30].

In onchocercomas, 1 and 3 days after treatment with ivermectin, microgranuloma formation by Eosinophils and macrophages around damaged microfilariae was enhanced and accompanied by numerous mast Cells [31]. Ivermectin (Mectizan) chose as a control strategy plan in onchocerciasis is active during 3 months for the less on clinical and histological data [32]. We report the findings of long-term control of this infection in the Río Santiago focus in Ecuador, between January 1990 and December 1996, using a strategy of giving ivermectin treatments biannually in hyperendemic communities and annually in meso- and hypoendemic communities [33]. In Western blot analysis, the sera of persons with Generalized onchocerciasis recognized 7 protein bands [34]. Volvulus collagen specified by clone PG3 was confirmed by measuring Antibody levels to the expressed product in individual sowda and Generalized onchocerciasis sera, respectively [35].

The hyporeactive, Generalized form, the Chronic hyperreactive (sowda) form and persons without signs of onchocerciasis from a hypoendemic area for onchocerciasis were compared [36]. Eosinophils from sowda patients responded more strongly to the Inflammatory mediator platelet-activating factor (PAF) than those from Generalized patients and persons without onchocerciasis [37]. Volvulus antigen, which may be useful in the diagnosis of onchocerciasis [38]. Single doses of ivermectin resulted in good clinical responses and created much goodwill among villagers [39]. We recommend that, during Mass Distribution of ivermectin, community involvement in planning overall health improvement should be included, since the treatment initiates the process well [40].

Initial skin snips from 12 patients contained microfilariae (1-9 per mg skin) [41]. Skin snips from all patients on days 3 and 28 revealed no microfilariae [42]. Pooled sera from General onchocerciasis or Bancroftian filariasis patients reacted only with the C-terminal region of the OVIF protein, whereas sowda onchocerciasis sera reacted 1-2 orders of magnitude more strongly and with a number of other epitopes [43]. Following their disappearance from the skin, a large Number of microfilariae was found in the regional lymph nodes [44]. The lymph nodes from treated patients had over ten times more Eosinophils compared to those from untreated persons with a peak of Eosinophil density at 40-48 hours after treatment [45].

Degenerating microfilariae in the lymph nodes were encircled by Eosinophils, which showed positive immunostaining for ECP, EPO or CLA [46]. Intra- and extracellular Eosinophil granules revealed a great variation in their condition [47]. Microfilaria appeared to be scarce and adult worms could not be detected clinically, as well as by ultrasonography (except in one case) [48]. Ninety-two patients had Generalized onchocerciasis, 21 patients suffered from the Chronic hyperreactive form of onchocerciasis (sowda), and 7 probands served as controls [49]. Reactivity and modulation by diethylcarbamazine of isolated Eosinophilic and Neutrophilic granulocytes from patients with generalized and Chronic hyper-reactive onchocerciasis (sowda or Localized form) from endemic foci in Liberia were evaluated under varying serum conditions [50].

In the presence of pooled sera from patients with Generalized onchocerciasis granulocytes from both polar groups of patients exhibited similar adherence rates, whereas immobilization rates were higher for Eosinophils than for neutrophils [51]. In Localized onchocerciasis, the use of autologous serum resulted in a significant decrease in adherence and immobilization rates for both eosinophils and Neutrophils [52]. After preincubation of Eosinophils, but not of microfilariae, with diethylcarbamazine autologous serum-mediated adherence and cytotoxicity were enhanced to rates similar to those found with pooled serum from individuals with generalized onchocerciasis [53]. These results suggest that granulocytes from both forms of onchocerciasis did not differ with respect to their anti-parasitic reactivity and that Antibodies as well as additional serum factors appear to contribute to the functional activity of these effector Cells [54]. This survey compared the prevalence of different forms of skin disease in two villages, one of which was located within the endemic zone for onchocerciasis (Zapallo Grande), in a lowland rain forest area of western Ecuador [55].

In addition changes closely correlated with the presence of microfilariae in skin snips were found in Zapallo Grande--such as atrophic gluteal changes, and acute and Chronic papular dermatitis [56]. The Amerindians in the endemic onchocerciasis area were more likely than Negroes to have Generalized Atrophic changes of the skin, whereas in the latter group significant numbers of individuals had no obvious skin lesions but large numbers of microfilariae were detected in skin snips [57]. Acute Papular dermatitis was common in both groups and in biopsied lesions microfilariae could usually be identified within the epidermis or close to the dermo-epidermal junction [58]. As an illustration, we have presented an interesting correlation between one particular clinical condition of onchocerciasis (Sowda) and the serological response, defined both in terms of the parasite antigens and an immunoglobulin class-restricted Antibody response [59]. In all cases except IgG3 the patterns of recognition by human Antibody classes were similar in sowda and generalized onchocerciasis [60].

Here, two major antigens (9 kD and 72kD) were recognized by IgG3 Antibodies in sowda sera but not generalized onchocerciasis sera [61]. Furthermore, these two antigens were not recognised by any other Ig class, either in Generalized or sowda onchocerciasis, nor were they detected by Antibodies of any class present in a collection of sera representative of other nematode infections [62]. This difference in the IgG3 response was so pronounced that sowda sera could be distinguished from generalized onchocerciasis sera by an IgG3-specific ELISA assay with a PBS parasite extract as the antigen [63]. The relevant illustration presented in this context is an interesting correlation between one particular clinical condition of onchocerciasis ("sowda") and the serological response, defined both in terms of the parasite antigen and an immunoglobulin class restricted Antibody response [64]. This contrasts with African onchocerciasis, where the lymph nodes tend to be Atrophic and microfilariae are usually present [65].

No microfilariae were detected in the Eyes of any of the patients who had positive outer canthus snips [66]. These patients appear to be anergic, with depressed Immune responses and numerous microfilariae in the skin [67]. Dermal changes were deeper and more diffuse than in African onchocerciasis, with many large fibroblasts and plasma cells [68]. When patients were treated with diethylcarbamazine, the dermatitis became suddenly worse as the microfilariae degenerated and provoked acute Inflammation [69]. The examination of microfilariae and Adult worms by scanning electron Microscopy as well as the histochemical staining of microfilariae for the demonstration of acid phosphatase activity confirmed that the concerned filaria belongs to the species Onchocerca volvulus [70].

The lack of delayed skin reaction in the generalized form of onchocerciasis is discussed, and a comparison is made with other diseases [71]. There microfilariae were most numerous in the capsule and in the fibrous tissue of the medulla, but smaller numbers were also found within lymphoid tissue, in dilated lymphatics and in blood vessels [72]. We believe that in Africians, antigens released from microfilariae of O [73].

References: 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 ,

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