Materiały źródłowe

• #1 Trachoma – StatPearls – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/books/NBK559035/

  Trachoma is a debilitating eye disease caused by the Chlamydia trachomatis bacterium and is one of the leading causes of blindness worldwide. Trachoma predominantly affects the conjunctiva, and the infection results in inflammation, roughening, and scarring of the inner surface of the eyelids, along with erosion of the corneal surface. […] The interaction between the life cycle of bacteria and the host’s immune system plays a crucial role in the development of trachoma. Upon entering the eye, C trachomatis initiates the infection by entering the epithelial cells of the conjunctiva and undergoes a biphasic developmental cycle. The infectious form of the bacteria, known as the elementary bodies, initially binds to and penetrates the host cells. […] The typical clinical signs of trachoma, such as conjunctival inflammation, follicular enlargement, and eventual scarring of the eyelids, are caused by the localized inflammatory response elicited by the replication of reticulate bodies. The pathophysiology and regulation of trachoma are significantly influenced by the immunological response triggered by the infection.

• #2 Trachoma: Background, Pathophysiology, Epidemiology

  https://emedicine.medscape.com/article/1202088-overview

  Trachoma is caused by serovars A, B, Ba, and C of C trachomatis. Different serovars predominate in different families and in different communities. […] Chlamydiae are gram-negative, obligate intracellular bacteria. The species C trachomatis causes trachoma and also genital infections (serovars D-K) and lymphogranuloma venereum (serovars L1-L3). Serovars D-K occasionally cause a subacute follicular conjunctivitis that may be clinically indistinguishable from trachoma, including follicular conjunctivitis with pannus, but rarely conjunctival scarring. However, these genital serovars do not typically enter stable transmission cycles within communities. Therefore, they are not involved in the genesis of trachoma blindness. […] Infection causes inflammation, that is, a predominantly lymphocytic and monocytic infiltrate with plasma cells and macrophages in follicles. The follicles are typical germinal centers with islands of intense B-cell proliferation surrounded by seas of T cells. Recurrent conjunctival reinfection causes the prolonged inflammation that leads to conjunctival scarring. Scarring is associated with atrophy of the conjunctival epithelium, loss of goblet cells, and replacement of the normal, loose, vascular subepithelial stroma with thick compact bands of type IV and type V collagen.

• #3 Trachoma – EyeWiki

  https://eyewiki.org/Trachoma

  Trachoma is caused by the bacterium Chlamydia trachomatis, which was first discovered by Prof. Feifan Tang and Xiaolou Zhang in 1956. […] Blindness from trachoma is due to recurrent episodes of active infection over months to years. The initial infection is confined to the conjunctival epithelium and triggers an immune response presenting as conjunctival follicles. Repeated infections with subsequent inflammatory responses results in tissue destruction with fibrosis and contraction, cicatricial entropion with trichiasis and lash corneal touch resulting in corneal erosions, ulcerations, scarring and vascularisation resulting in corneal opacification and resultant blindness.

• #4 Insights into Pathogenesis of Trachoma

  https://www.mdpi.com/2076-2607/12/8/1544

  The diverse manifestations of Ct infections are attributed to inactivating mutations found in the genomic sequences of the tryptophan synthase operon (trpRBA), located within a region known as the plasticity zone (PZ). Ocular serovars A, Ba, and C have mutations in the TrpA gene, which codes the α subunits of tryptophan synthase, resulting in the synthesis of a truncated, enzymatically inactive TrpA. In contrast, all urogenital serovars (D–K) encode a full-length, active TrpA. […] Ct has a life cycle consisting of two morphologically distinct forms: the elementary body (EB), which is the small, metabolically inactive extracellular form of the microorganism in which it moves between host cells, namely human epithelial cells, and the reticulate body (RB), the larger, metabolically active, intracellular stage.

• #5 Trachoma | Nature Reviews Disease Primers

  https://www.nature.com/articles/s41572-022-00359-5

  The elementary body has a rigid cell wall, which facilitates survival under unfavorable conditions. The major outer membrane protein is the most abundant cell wall surface protein, comprising ~60% of cell wall mass. It is involved in host cell surface adhesion and is encoded by a single-copy chromosomal gene, OmpA. […] The mechanism by which conjunctival Ct survives in this milieu and whether its peculiar biochemistry could be exploited against human disease is unknown. […] The limited longitudinal data available indicate that a primary infection episode in a child is characterized by a short preclinical phase of a few days before the development of signs of inflammation. In adult human volunteer experiments, clinical inflammation developed ~10 days after conjunctival Ct inoculation. […] The different time courses of conjunctival infection and active trachoma explain the partial mismatch observed between infection and disease at the individual level. This disparity has important implications for trachoma programmes, as individually targeted antibiotic treatment decisions based on observable conjunctival inflammation of at least moderate intensity would miss many infected individuals with a mild clinical response.

• #6 Trachoma | Ento Key

  https://entokey.com/trachoma-2/

  During its developmental cycle, C. trachomatis exists as reticulate bodies that are metabolically active in the intracellular stage and as elementary bodies that are the metabolically inactive extracellular form of the organism that can transfer between host cells and organisms. […] The infectious cycle begins with the attachment of the elementary bodies to the surface of epithelial cells, followed by endocytosis of the bacteria. Inside the host cell, within 6 to 9 hours, the elementary bodies transform into the reticulate form and replicate by binary fission.

• #7 Trachoma | PPT

  https://www.slideshare.net/slideshow/trachoma-250557660/250557660

  Primary infection induces purulent follicular conjunctivitis Primary infection resolves spontaneously, induces transient protective immunity, but do not protect from reinfection Multiple or persistent infection are essential characteristics in pathogenesis. Recurrent infection elicits cell mediated delayed hypersensitivity(type IV) Chronic inflammation leads to follicular conjunctivitis and papillary hypertrophy of the upper palpebral conjunctiva, a superior superficial corneal pannus, and fine epithelial keratitis. Eventually, multiple reinfection leads to scarring and cicatrization of the cornea, conjunctiva, and eyelids. […] Both humoral and cell mediated immune responses are involved. Humoral response Target antigens Major outer membrane protein (MOMP) and Heat shock proteins (HSP60) Polymorphic outer membrane proteins (POMPs) IgM and IgG antibodies appear in serum IgG and IgA in mucosal secretions Antichlymadial antibodies -Neutralize chlamydiae -Block attachment -Inhibit internalisaton of the organism.

• #8 Volume 5, Chapter 60. Pathogenesis and Control of Blinding Trachoma

  http://www.oculist.net/downaton502/prof/ebook/duanes/pages/v5/v5c060.html

  Chlamydial Infection Trachoma agent cannot be identified in all cases of clinically active trachoma. With the highly sensitive and specific DNA amplification technology (polymerase chain reaction [PCR], ligase chain reaction [LCR]), C. trachomatis is found most frequently in severe intensity cases (80% positive), less often in moderate cases (60%), but also in clinically inactive cases (15% to 30%). […] Immunologic studies of trachoma and other chlamydial infections have had two main goals: (1) understanding the pathology of the disease, and (2) identifying protective mechanisms to develop effective vaccines. Both humoral and cell-mediated immune responses to chlamydiae occur in trachoma but consensus is that protective immunity to chlamydia is a type 1 helper T-cell (Th-1)-mediated response.

• #9 Insights into Pathogenesis of Trachoma

  https://www.mdpi.com/2076-2607/12/8/1544

  The infection can resolve or progress to eyelid scarring. The resolution of Ct is believed to rely on the presence of interferon gamma (IFNγ) derived from an immune response mediated by CD4+ T helper 1 (TH1) cells. […] The primary clinical indicator associated with the formation of scarring is intense conjunctival inflammation, which correlates with a heightened expression of various pro-inflammatory factors. Additionally, studies have found that both active and scarring trachoma show increased amounts of matrix metalloproteinases (MMPs) 7, 9, and 12. MMPs are a family of extracellular matrix (ECM) remodeling endopeptidases that have the capacity to degrade almost every component of the ECM, promoting the contraction of scars. […] Exploring the pathophysiology of trachoma not only unveils the intricate pathways and mechanisms underlying this devastating eye disease but also underscores the multifaceted dimensions that must be considered in its management.

• #10 Trachoma | PPT

  https://www.slideshare.net/slideshow/trachoma-250557660/250557660

  Cellular response Phagocytose EB Neutrophil elastase and cathepsin G Help in limiting the initial infection PMN Higher preponderence of T cells Th-1 resolution of infection Th -2 involved in scarring T cell B cell Stimulate tissue remodelling Increased collagenase production from fibroblasts IL-1 TNF- Involved in progressive scarring TGF- Inhibits replication of bacteria by reducing intracellular level of tryptophan and stimulating iNOS activity Resulting in large ,morphologically aberrant persistent bodies(PBs). […] Chronic inflammation characterized by papillary hypertrophy of epithelium and lymphoid infiltration of subepithelial tissue. Follicle Mass of mononuclear cells surrounded by phagocytes, giant phagocytes (Lebers cells), polymorphs, mast cells and eosinophils. […] In progressive pannus, infiltration of cornea is ahead of vascularisation In regressive pannus, vessels extend a short distance beyond the area of infiltration.

• #11 Trachoma: Background, Pathophysiology, Epidemiology

  https://emedicine.medscape.com/article/1202088-overview

  The clinical changes are a delayed-type hypersensitivity reaction to the chlamydial antigens (thought to be HSP-60). This induces an immune response with germinal centers (seen as follicles) and intense inflammatory infiltrate and the formation of papillae. Over time, this intense inflammation leads to scar formation, which, in turn, causes contraction and buckling of the tarsal plate of the upper lid, producing entropion and trichiasis.

• #12 Trachoma – StatPearls – NCBI Bookshelf

  https://www.ncbi.nlm.nih.gov/books/NBK559035/

  The pathophysiology of trachoma is characterized by the development of conjunctival scarring, which results from recurrent cycles of tissue repair and inflammation. Extracellular matrix proteins such as collagen and fibronectin are deposited throughout the scarring process, leading to fibrosis and contraction of the conjunctival tissue. […] Bacterial infection, inflammatory reactions, tissue remodeling, and host factors intricately interact in the pathophysiology of trachoma. […] The obligate intracellular bacterium C trachomatis and the host’s immune system interact intricately in the pathophysiology of trachoma, leading to conjunctival scarring, tissue destruction, and increasing inflammation. […] The inflammatory cascade triggered by C trachomatis infection releases proinflammatory cytokines and chemokines, which further amplify the immune response and contribute to tissue damage. Chronic inflammation on the conjunctival surface results in the formation of follicles, which are aggregations of lymphocytes, plasma cells, and epithelial cells. […] Understanding these mechanisms is imperative for developing targeted interventions aimed at halting the progression of the disease and reducing the incidence of blindness caused by trachoma.

• #13 Trachoma | IntechOpen

  https://www.intechopen.com/chapters/82829

  Trachomatous inflammation begins with the recruitment and activation of a host of leukocytes in the conjunctival tissue. Increased expression of certain proteases like matrix metalloproteinases (MMPS), e.g. MMP7, MMP9, and MMP12, and pro-inflammatory agents like chemokines and cytokines are associated with severe disease. Research has shown that the predominant cellular constituents of trachoma follicles are macrophages, plasma cells with lymphocytic and monocytic infiltrate. Typically, the follicles are made up of germinal centers with clumps of intense B-cell proliferation that are surrounded by multiple T cells. Scarring ensues when conjunctival epithelium lose goblet cells and compact collagen bands replace the normally freely mobile and vascular subepithelial stroma. […] Trachoma evades host immune responses through intracellular invasion. Therefore, the leading sequalae are a result of inflammation rather than infection by C. Trachomatis. It is now clear that host immunity plays a significant role in clinical presentation and disease severity. The most likely pathway is that increased chemokine responses lead to neutrophil activation, chemotaxis, and fibrosis. This is mediated by the activities of TH1 as a pro-inflammatory as well as TH2 serving as a potent inducer of anti-inflammatory responses. […] Blindness from trachoma occurs from conjunctival scarring which is attributed to recurrent infection. Subconjunctival fibrotic bands eventually cause scar contraction leading to entropion, trichiasis, and finally corneal opacification.

• #14 Trachoma: Protective and Pathogenic Ocular Immune Responses to Chlamydia trachomatis | PLOS Neglected Tropical Diseases

  https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0002020

  The matrix metalloproteinases are a group of more than 25 endopeptidases with multiple, complex functions. While MMPs are required for normal tissue homeostasis, there is also evidence that they play a role in the pathogenesis of a range of inflammatory-fibrotic diseases. An important step is the disruption of the basement membrane, aiding the recruitment of inflammatory cells. MMPs also have wide-ranging effects on inflammatory and immune processes such as modulating chemokine activity and activation of TGF, IL-1, and TNF. […] Scarring develops when normal tissue architecture is disrupted and replaced by excessive connective tissue through the abnormal accumulation of ECM components. Tissue damage can be mediated through a variety of cell types and mechanisms. Neutrophil infiltration appears important in trachoma: they have been identified in conjunctival biopsies of trachomatous tissue, they produce toxic reactive oxygen and nitrogen species that damage host tissue in animal models of genital tract infection, and they can also produce MMPs.

• #15 Trachoma – Symptoms and causes – Mayo Clinic

  https://www.mayoclinic.org/diseases-conditions/trachoma/symptoms-causes/syc-20378505

  Trachoma is caused by certain subtypes of Chlamydia trachomatis, a bacterium that can also cause the sexually transmitted infection chlamydia. […] Trachoma spreads through contact with discharge from the eyes or nose of an infected person. Hands, clothing, towels and insects can all be routes for transmission. In developing countries, eye-seeking flies also are a means of transmission. […] The World Health Organization (WHO) has identified five stages in the development of trachoma: Inflammation follicular. The early infection has five or more follicles small bumps that contain lymphocytes, a type of white blood cell visible with magnification on the inner surface of your upper eyelid (conjunctiva). Inflammation intense. In this stage, your eye is now highly infectious and becomes irritated, with a thickening or swelling of the upper eyelid. Eyelid scarring. Repeated infections lead to scarring of the inner eyelid. The scars often appear as white lines when examined with magnification. Your eyelid may become distorted and may turn in (entropion). In-turned eyelashes (trichiasis). The scarred inner lining of your eyelid continues to deform, causing your lashes to turn in so that they rub on and scratch the transparent outer surface of your eye (cornea). Corneal clouding (opacity). The cornea becomes affected by an inflammation that is most commonly seen under your upper lid. Continuous inflammation compounded by scratching from the in-turned lashes leads to clouding of the cornea.

• #16 Trachoma: Protective and Pathogenic Ocular Immune Responses to Chlamydia trachomatis | PLOS Neglected Tropical Diseases

  https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0002020

  A key clinical observation pointing to the immunopathogenic nature of trachoma is that visible conjunctival inflammation is frequently found in the absence of detectable Ct. In longitudinal studies, discrete episodes of active disease persist long after the associated initiating infectious episode has resolved. […] The immunological paradigm suggests that tissue damage and fibrosis in chlamydia-related disease results from CMI responses against specific chlamydial antigens. It argues that specific T-cell responses, which are important in clearing Ct infection, also cause collateral tissue damage. […] The cellular paradigm does not differentiate between damage resulting from professional innate immune cells, such as neutrophils and monocytes, and adaptive immune cells. However, it does propose that chronic inflammatory responses, tissue damage, and fibrosis in Ct-related disease is largely driven from the epithelium rather than by CMI. There is now increasing evidence that innate immune responses are a prominent feature of responses in trachoma and likely interact with the adaptive response.

• #17 Volume 5, Chapter 60. Pathogenesis and Control of Blinding Trachoma

  http://www.oculist.net/downaton502/prof/ebook/duanes/pages/v5/v5c060.html

  Trachoma is a chronic infectious keratoconjunctivitis that is a major cause of blindness in many developing countries. It presents initially as a follicular conjunctivitis, with superficial keratitis and corneal vascularization, and gradually progresses to conjunctival scarring and lid distortion. Damage to the cornea occurs from the chronic inflammatory disease and later from exposure and trauma from the distorted lids and inturned lashes. […] Trachoma is a chronic inflammation of the conjunctiva and cornea that progresses to conjunctival scarring and corneal vascularization. Chlamydia trachomatis is the specific and unique etiologic agent of trachoma but other pathogenic microorganisms often contribute to the disease process. In its communicable inflammatory phase, the conjunctiva in trachoma is characterized by the presence of lymphoid germinal centers (lymphoid follicles) surrounded by intense and inflammatory diffuse infiltration and hyperemia (papillary hypertrophy) and by the growth of superficial blood vessels over the superior cornea (vascular pannus).

• #18 Trachoma | PPT

  https://www.slideshare.net/slideshow/trachoma-250557660/250557660

  Other changes The desquamated conjunctival epithelium exhibits glycogen-rich intracytoplasmic inclusion bodies and large macrophages containing nuclear fragments (Leber cells) Alteration of extracellular matrix formation of new collagen type I,II , III,IV Increase in basement membrane collagen type IV and V and decrease in types I,III (in scarred trachoma)(role of matrix metalloproteinase B). […] If sufficient tarsoconjunctival scarring accumulates, contraction of it over the years will cause the upper eyelid to turn inward so that the lashes rub against the globe. This is known as trichiasis. When the whole lid margin is turned in, the condition is known as entropion. Scars around the bases of hair follicles can pull individual eyelashes into contact with the cornea, even without entropion. In addition to the direct abrasive effect of the in-turned lashes, secondary bacterial and fungal infections of the cornea and corneal drying due to scarring of forniceal-mucous, lacrimal, and meibomian glands accelerate epithelial damage. Collagenous scar is laid down as part of the repair process. Because scars are opaque, vision can be affected by scarring that involves the central part of the cornea.

• #19

• #20 Trachoma – Wikipedia

  https://en.wikipedia.org/wiki/Trachoma

  Trachoma is caused by Chlamydia trachomatis, serotypes (serovars) A, B, and C. It is spread by direct contact with eye, nose, and throat secretions from affected individuals, or contact with fomites (inanimate objects that carry infectious agents), such as towels and/or washcloths, that have had similar contact with these secretions. Flies can also be a route of mechanical transmission. Untreated, repeated trachoma infections result in entropion (the inward turning of the eyelids), which may result in blindness due to damage to the cornea. Children are the most susceptible to infection due to their tendency to get dirty easily, but the blinding effects or more severe symptoms are often not felt until adulthood. […] Blinding endemic trachoma occurs in areas with poor personal and family hygiene. Many factors are indirectly linked to the presence of trachoma including lack of water, absence of latrines or toilets, poverty in general, flies, close proximity to cattle, and crowding. The final common pathway, though, seems to be the presence of dirty faces in children, facilitating the frequent exchange of infected ocular discharge from one child’s face to another. Most transmission of trachoma occurs within the family.

• #21

  https://www.who.int/news-room/fact-sheets/detail/trachoma

  Trachoma is a disease of the eye caused by infection with the bacterium Chlamydia trachomatis. […] The infection is transmitted by direct or indirect transfer of eye and nose discharges of infected people, particularly young children who harbour the principal reservoir of infection. These discharges can be spread by particular species of flies. […] After years of repeated infection, the inside of the eyelid can become so severely scarred (trachomatous conjunctival scarring) that it turns inwards and causes the eyelashes to rub against the eyeball (trachomatous trichiasis), resulting in constant pain and light intolerance. This and other alterations of the eye can lead to scarring of the cornea. Left untreated, this condition leads to the formation of irreversible opacities, with resulting visual impairment or blindness. […] Environmental factors associated with more intense transmission of C. trachomatis include inadequate hygiene, crowded households, inadequate access to water, and inadequate access to and use of sanitation.

• #22 Volume 5, Chapter 60. Pathogenesis and Control of Blinding Trachoma

  http://www.oculist.net/downaton502/prof/ebook/duanes/pages/v5/v5c060.html

  In Gambia, those with the A*6802 allele of HLA-A28 (class I) had significantly more trachomatous scarring. Scarring from trachoma in Gambia was also associated with a polymorphism in the TNF- genes promoter, independent of the HLA type. […] In Oman, blinding trachoma (trichiasis and corneal opacity) was significantly associated with HLA-DR16 (a DR2 subtype). Blinding trachoma was significantly lower in patients in the HLA-DR53 group. Thus, it appears that there are multiple genetic factors that affect susceptibility to infection and the risk of developing scarring and visual loss in trachoma.

• #23 Genetic susceptibility to scarring trachoma | LCNTDR

  https://www.londonntd.org/research/projects-search/genetic-susceptibility-to-scarring-trachoma

  Trachoma is the leading infectious cause of blindness worldwide. Repeated conjunctival infection by Chlamydia trachomatis throughout childhood triggers a poorly understood inflammatory-driven scarring response in the eyelids, which continues throughout the lives of some individuals even in the absence of detectable infection. […] This study aims to identify the genetic determinants associated with the development of scarring trachoma subsequent to ocular infection with C. trachomatis. This will enable us to identify the key genes and biological pathways that contribute to the pathogenesis of this disease. […] These studies in Tanzania will serve as both discovery and validation studies of case-control studies performed in The Gambia, and are an essential step in determining the causal and common pathways to scarring disease that might inform vaccine design.

• #24 Volume 5, Chapter 60. Pathogenesis and Control of Blinding Trachoma

  http://www.oculist.net/downaton502/prof/ebook/duanes/pages/v5/v5c060.html

  The pathognomonic lesion of trachoma is the lymphoid follicle, which forms in the subepithelial tissue. Small follicles consist only of masses of lymphoid cells. In larger follicles, the center consists of large lymphocytic cells, with abundant cytoplasm and a few macrophages. Surrounding this is a zone of small lymphocytes, which may extend to the layer immediately below the basement membrane of the epithelium. […] Fibrosis in the subconjunctival connective tissue occurs by fibroblast formation from blood vessels and by cicatrization of necrotic follicles. This scar formation often forms a network, leaving islands of relatively unscarred conjunctiva that protrude above the depressed scars. Scarring also obliterates the layer of subconjunctival vessels, grossly deranging the normal vascular architecture.

• #25 Immunopathogenesis of conjunctival scarring in trachoma | Eye

  https://www.nature.com/articles/eye1998104

  Trachoma, a chronic follicular conjunctivitis caused by infection with Chlamydia trachomatis, is the leading cause of preventable blindness. The blinding complications are associated with progressive conjunctival scarring that may result from immunologically mediated responses. […] The upregulated local production of IL-1, IL-, TNF- and PDGF might contribute to conjunctival damage and scarring in trachoma.

• #26 The Development of an Age-Structured Model for Trachoma Transmission Dynamics, Pathogenesis and Control | PLOS Neglected Tropical Diseases

  https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0000462

  Trachoma, the worldwide leading infectious cause of blindness, is due to repeated conjunctival infection with Chlamydia trachomatis. […] The model is based on the concept of multiple reinfections leading to progressive conjunctival scarring, trichiasis, corneal opacity and blindness. […] Several studies have postulated that the sequelae of trachoma are caused by immunopathological processes that increase in severity with increasing age. […] It is assumed that adaptive immunity does not protect from acquiring infection but results in an increasing rate of recovery from infection as the number of previous infections increases; such a framework was chosen here due to the limited evidence for protective immunity against infection. […] The model assumes that scarring worsens through repeat infection with C. trachomatis and that, as scarring (TS) becomes worse, the more severe disease sequelae (TT and CO) occur. […] The model captures well the progression of scarring with age and reproduces the observed age-profiles of ocular sequelae prevalence.

• #27 Scholarly Article or Book Chapter | Trachoma | ID: ks65hp473 | Carolina Digital Repository

  https://cdr.lib.unc.edu/concern/articles/ks65hp473

  Trachoma is a neglected tropical disease caused by infection with conjunctival strains of Chlamydia trachomatis. It can result in blindness. Pathophysiologically, trachoma is a disease complex composed of two linked chronic processes: a recurrent, generally subclinical infectious inflammatory disease that mostly affects children, and a non-communicable, cicatricial and, owing to trichiasis, eventually blinding disease that supervenes in some individuals later in life. […] At least 150 infection episodes over an individuals lifetime are needed to precipitate trichiasis; thus, opportunity exists for a just global health system to intervene to prevent trachomatous blindness. […] Blindness attributable to trachoma can appear in communities many years after conjunctival C. trachomatis transmission has waned or ceased; therefore, the two linked disease processes require distinct clinical and public health responses.

• #28 Scholarly Article or Book Chapter | Trachoma | ID: ks65hp473 | Carolina Digital Repository

  https://cdr.lib.unc.edu/concern/articles/ks65hp473?locale=en

  Trachoma is a neglected tropical disease caused by infection with conjunctival strains of Chlamydia trachomatis. It can result in blindness. Pathophysiologically, trachoma is a disease complex composed of two linked chronic processes: a recurrent, generally subclinical infectious inflammatory disease that mostly affects children, and a non-communicable, cicatricial and, owing to trichiasis, eventually blinding disease that supervenes in some individuals later in life. At least 150 infection episodes over an individual’s lifetime are needed to precipitate trichiasis; thus, opportunity exists for a just global health system to intervene to prevent trachomatous blindness. […] Blindness attributable to trachoma can appear in communities many years after conjunctival C. trachomatis transmission has waned or ceased; therefore, the two linked disease processes require distinct clinical and public health responses.

• #29 Insights into Pathogenesis of Trachoma

  https://www.mdpi.com/2076-2607/12/8/1544

  Trachoma is the most common infectious cause of blindness worldwide. This review investigates the pathogenesis of trachoma, focusing on its causative agent, transmission pathways, disease progression, and immune responses. Trachoma is caused by serovars A–C of the bacterium Chlamydia trachomatis (Ct). Transmission occurs through direct or indirect exchanges of ocular and nasal secretions, especially in regions with poor hygiene and overcrowded living conditions. The disease is initiated in early childhood by repeated infection of the ocular surface by Ct. This triggers recurrent chronic inflammatory episodes, leading to the development of conjunctival scarring and potentially to trichiasis, corneal opacity, and visual impairment. Exploring the pathogenesis of trachoma not only unveils the intricate pathways and mechanisms underlying this devastating eye disease but also underscores the multifaceted dimensions that must be considered in its management.

• #30 Trachoma – PAHO/WHO | Pan American Health Organization

  https://www.paho.org/en/topics/trachoma

  The main risk factors for the occurrence of the disease are related to lack of access to water, the presence of flies, poor hygienic conditions, and overcrowding. Repeated infections since childhood and during youth seem to be necessary to produce the complications that occur later in life. A single episode of acute C. trachomatis conjunctivitis is not considered vision threatening because there is virtually no risk of prolonged inflammation or chronic complications. […] Major interventions should be directed at preventing trachoma infection including improved sanitation and increased facial hygiene activities (with clean water) for children at risk for the disease. The pain and suffering due to trachomatous trichiasis, which can eventually cause visual impairment and irreversible blindness, can be alleviated by a simple surgical procedure performed locally.

• #31 Severity of Trachomatous Scarring among Adults in Trachoma-Endemic Amhara Region of Ethiopia in: The American Journal of Tropical Medicine and Hygiene Volume 111 Issue 3_Suppl (2024)

  https://www.ajtmh.org/view/journals/tpmd/111/3_Suppl/article-p121.xml

  Trachomatous scarring has been shown to progress regardless of active ocular Chlamydia trachomatis infection, indicating that scarring drivers may be unrelated to ongoing transmission. […] Trachomatous scarring of the conjunctiva is a result of a T helper 2 cell-mediated immune response initially triggered by repeated C. trachomatis infections and is generally noted to occur in adulthood, although studies within communities of high endemicity have observed scarring in children. […] Although repeated C. trachomatis infection is required for the development of conjunctival scarring, once acquired, progression of scarring may in part be independent of ongoing transmission. Progression may be related to inflammatory processes potentially triggered by non-chlamydial bacterial infections or adverse environmental conditions.

• #32 Severity of Trachomatous Scarring among Adults in Trachoma-Endemic Amhara Region of Ethiopia in: The American Journal of Tropical Medicine and Hygiene Volume 111 Issue 3_Suppl (2024)

  https://www.ajtmh.org/view/journals/tpmd/111/3_Suppl/article-p121.xml

  The aim of this study was to investigate the prevalence and severity of scarring among men and women in a trachoma-hyperendemic setting using survey-collected conjunctival photographs and a validated five-point scarring scale. […] This study revealed that increasing age, female sex, and increasing district-level TF prevalence were all independently related to increasing odds of conjunctival scarring severity among adults. […] The progression of scarring at younger ages among endemic communities is expected to be a result of both accumulating C. trachomatis infection and recurrent inflammation. […] Scarring progression and the development of TT have also been observed in the absence of ongoing C. trachomatis infection, likely through continual inflammatory processes. […] The results from this study, which demonstrated a correlation between higher district-level TF prevalence and scarring severity, suggest that trachoma control programs may also want to focus surveillance efforts on those districts that were formerly the most highly endemic.

• #33 Pathogenesis of progressive scarring trachoma in Ethiopia and Tanzania and its implications for disease control: two cohort studies. | InfoNTD

  https://www.infontd.org/resource/pathogenesis-progressive-scarring-trachoma-ethiopia-and-tanzania-and-its-implications

  Trachoma causes blindness through a conjunctival scarring process initiated by ocular Chlamydia trachomatis infection; however, the rates, drivers and pathophysiological determinants are poorly understood. […] Progressive scarring was found in 135/585 (23.1%) of Ethiopian participants and 173/577 (30.0%) of Tanzanian participants. There was a strong relationship between progressive scarring and increasing inflammatory episodes (Ethiopia: OR 5.93, 95%CI 3.31-10.6, p0.0001. Tanzania: OR 5.76, 95%CI 2.60-12.7, p0.0001). […] Scarring progressed in the absence of detectable C. trachomatis, which raises uncertainty about the primary drivers of late-stage trachoma. Chronic conjunctival inflammation appears to be central and is associated with enriched expression of pro-inflammatory factors and altered expression of extracellular matrix regulators. Host determinants of scarring progression appear more complex and subtle than the features of inflammation. Overall this indicates a potential role for anti-inflammatory interventions to interrupt progression and the need for trichiasis disease surveillance and surgery long after chlamydial infection has been controlled at community level.

• #34 Trachoma – The International Agency for the Prevention of Blindness

  https://www.iapb.org/learn/knowledge-hub/eye-conditions/trachoma/

  Trachoma results from bacterial infection of the conjunctiva by Chlamydia Trachomatis. Repeated infections of the conjunctivae with Chlamydia trachomatis can lead to trichiasis, corneal opacity and blindness. […] Infection occurs primarily among younger children and is transmitted from person to person mainly through contact and sometimes by eye-seeking flies. […] Progress to eliminate trachoma as a public health problem has been accelerated by significant coordination between health ministries, donors, implementing partners to scale up the WHO-endorsed SAFE strategy, which consists of multiple interventions to target various routes of transmission, as well as treating infection and its disabling effects. […] The strategy consists of: Surgery to correct trachomatous trichiasis, Antibiotics for C. trachomatis infection, Facial cleanliness to reduce transmission, Environmental improvement to reduce risk of transmission and infection.

• #35 Trachoma: how a common cause of blindness can be prevented worldwide – Our World in Data

  https://ourworldindata.org/trachoma-how-a-common-cause-of-blindness-can-be-prevented-worldwide

  The spread of the Chlamydia trachomatis bacteria can be reduced. With more access to clean water and sanitation, better waste management, and hygiene, it becomes less likely that the bacteria spread between people. Insecticides can also help deter flies. […] The disease can be prevented in people who have been infected. For example, antibiotics such as azithromycin and tetracycline can kill the bacteria causing the disease. For people who have progressed to later stages of the disease, there are also cheap surgeries, which reshape the patients eyelids or remove in-turned eyelashes. These help prevent the clouding of the cornea and blindness. […] Gambhir et al. (2009) estimate that it takes over a hundred infections per individual, on average, for trichiasis (when the eyelashes begin to scratch the cornea) to develop. This estimate is based on simulations using data on the duration of each infection and infection load and may be revised based on further data. […] Indoor spraying of insecticides and the wearing of insecticide-treated scarves have been found to protect against trachoma infections.

• #36 Trachoma – The International Agency for the Prevention of Blindness

  https://www.iapb.org/learn/knowledge-hub/eye-conditions/trachoma/

  The World Health Organizations World Report on Vision and Ending the Neglect to Attain the Sustainable Development Goals: A road map for neglected tropical diseases 20212030, provide blue prints to accelerate progress towards the elimination of trachoma as a public health problem by 2030, through comprehensive integrated people centred approaches.

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