Ocular toxocariasis

Introduction to ocular toadstool disease Ocular toxoplasmosis (oculartoxocariasis) is an infectious disease caused by larvae of canine aphids or cat mites that invade the tissues of the eye. Human infections are caused by food contaminated with eggs infected with toadstools. basic knowledge The proportion of sickness: 0.01% Susceptible people: no special people Mode of infection: digestive tract spread Complications: retinopathy retinal detachment choroidal detachment amblyopia strabismus

Causes of ocular toadstool disease

(1) Causes of the disease

Canine toadstools complete their life cycle in dogs. People and many other animals are infected with the second stage larvae, that is, the larvae hatch in the small intestine, and the blood flow through the intestinal wall is the second stage. The infection is usually in the canine body. The blood vessels migrate to the surrounding tissues, and the larvae become cysts. When the female dog is pregnant, the cysts or the larvae in the latent body move again, and then enter the bloodstream and infect the puppies before birth through the placenta, the second period after birth. The larva enters the lungs and becomes the third stage larva. It coughs up and swallows into the small intestine of the small dog to form the fourth stage larva. The larva can mature in 3 weeks and begin to lay eggs in large quantities. One aphid can lay eggs 200,000 in one day. These infected eggs are excreted by feces, contaminated everywhere, and become the root cause of human and animal infections. Dogs and cats are fixed hosts of Toxoplasma gondii, and humans are intermediate hosts or accidental hosts. This parasite cannot mature or multiply in the human body.

Human infection is caused by the swallowing of fertilized eggs of infected dogs. Especially those who are in close contact with dogs, cats, and people who are not paying attention to hygiene are more likely to cause infection. Fertilized eggs hatch in the small intestine, and the second stage larvae enters the blood from the intestines. Transfer to the liver, heart, lungs, brain, eyes and surrounding circulation. When the larva reaches the small artery whose vascular diameter is smaller than the body, it passes through the wall of the tube and enters its organ. The development of the locust in the human body does not exceed the second stage. Therefore, it is impossible to breed eggs in the human body, so the human stool test is negative, the larva can remain as a quiet cystic state in the surrounding tissue and is asymptomatic, but acute visceral aphid migration (VLM) occurs when it moves. In the eye, a single larva can cause vision loss. The larva can enter the eye directly through the choroidal ciliary body or the central retinal artery. Before entering the eye, the larva can be a cyst and located in the surrounding tissue.

(two) pathogenesis

Canine serrata is a common intestinal parasite in dogs. The fertilized eggs of C. elegans are excreted with feces and develop into infectious eggs under appropriate conditions. When swallowed by adult dogs, larvae hatch in the small intestine. Out, entering the blood through the intestinal wall, the larva can not complete the migration from the lung to the small intestine, so can not further develop into adult worms, only migrate to the various tissues and organs in the body to form cysts, when the female dog is pregnant, the wrapped larvae can recover The habit of migration, with the blood entering the fetal dog through the placenta to reach the liver, after the birth of the fetal dog, the larva migrates to the lungs and reaches the pharynx through the trachea, swallows into the stomach and enters the small intestine to develop into an adult. Another infection is 3 Infants under the age of one month swallowed infected eggs and hatched into larvae in the small intestine. The larvae entered the lymphatic system of the intestinal wall, reached the liver through the blood circulation, and then reached the pharynx through the lungs and trachea. After being swallowed, they developed in the small intestine. For adults, if humans infect infected eggs, the larvae hatch in the small intestine and enter the intestinal wall through the lymphatic system to the mesenteric lymph nodes, then reach the liver via the blood, and then the blood to the lungs. Since human beings are not suitable hosts, larvae cannot complete the migration from the lungs to the small intestines to develop into adults. Therefore, there are no eggs of the genus Canines in human feces, and the larvae spread throughout the body to form visceral larval migration, which can invade the liver. Tissues such as the lungs, brain, kidneys, heart, muscles and eyes are usually surrounded by reactive inflammatory granuloma, many of which can survive in the cyst for many years.

This disease can cause uveitis by directly invading the tissues in the eye and/or by causing an immune response. The larvae that invade the tissues in the eye often cause chronic vitreitis, focal necrotizing granulomatous inflammation, which is characterized by Eosinophils, epithelial cells, multinucleated giant cells, plasma cells and lymphocytes infiltrate around the larvae. Studies have found that patients with vitreous and aqueous humor have high titers of anti-bowworm antibodies (IgG, IgE), suggesting an immune response in the eye. The occurrence of toxoplasmosis may play an important role.

Eye toadstool disease prevention

The important problem for toxoplasmosis is prevention, attention to personal hygiene, cats, dogs should pay more attention, not too close, domestic animals should be quarantined at the right time, if necessary, should be treated.

Ocular arch tsutsugamushi complications Complications retinopathy retinal detachment choroidal detachment amblyopia strabismus

Ocular toxoplasmosis is prone to cause proliferative vitreoretinopathy and traction retinal detachment; resulting ciliary membrane contraction can lead to detachment of the ciliary body and choroid, affecting aqueous humor production and leading to low intraocular pressure; due to severe impact on the patient's vision There may be complications such as strabismus and amblyopia.

Symptoms of ocular toadstool disease Common symptoms unilateral fundus appears... Aphid infection pruritus keratitis nodular retinal detachment

1. Whole body performance: Because the larva not only invades the tissues in the eye, but also invades any other organs and tissues at the same time, causing fever, fatigue, weight loss, cough, wheezing, liver, itching of the trunk and lower extremities, rash and nodules, etc. Individual patients may have manifestations of central nervous system involvement, such as encephalitis, brain eosinophilic granuloma, epilepsy, etc., but many patients do not have any systemic symptoms and signs.

2. Ocular manifestations : ocular symptoms may have dark shadows in front of the eyes, decreased vision, etc. The degree of visual acuity may vary greatly from patient to patient. Some patients are often difficult to express exact clinical symptoms due to their young age.

The most common change in this disease is a granulomatous change in the unilateral fundus, which is caused by the formation of cysts after the second stage larva invades the choroid. The granuloma can occur in the posterior pole, but also in the peripheral, posterior Lesions 3 / 4 ~ 3 optic disc diameter, gray or white bulge, often accompanied by mild to severe vitreous inflammatory response and decreased vision, some patients may have chalk or strabismus, peripheral granuloma is a common The change is often manifested as a white bulging lesion in the peripheral fundus, which is easily accompanied by retinal folds. This fold can extend from the peripheral part to the optic disc, and the peripheral lesion sometimes changes like a snowy embankment of the middle uveitis.

Ocular arch tsutsugamushi can cause chronic endophthalmitis, manifested as mild anterior uveitis, post-iris adhesion, ciliary membrane formation, vitreous inflammation and retinal detachment, occasionally causing anterior chamber empyema, optic discitis, macular edema Some patients may also have peripheral retinitis, which may be caused by larval arrest in the peripheral retinal vessels; in a few patients, live larvae can still be seen in the retinal vessels; ocular toxoplasmosis can still cause neuroretinitis, Retinal branch artery occlusion, scleritis, keratitis, etc., in addition to the invasion of the lens by the mites, causing a lens mass.

Eye bow tsutsugamushi examination

1. Blood routine : blood routine examination during activity can be found to increase white blood cells, even up to 100,000/mm3. Elevated white blood cells are mainly eosinophils, which can account for 50% to 90%, and the rise of white blood cells can be It lasts for months or even years.

2. Serological examination : serum IgG, IgM and IgE are usually elevated. Enzyme-linked immunosorbent assay (ELISA) is a stable and reliable diagnostic test. At least two antigens are used, one from embryonic eggs. The other is an external antigen. The antibody assay has higher sensitivity (90%) and specificity (90%). Generally, the cut-off point of antibody titer is set at 1:8, and most patients have found positive results. As the selected cut-off value (potency) increases, the sensitivity gradually decreases, but the specificity also gradually increases. During the disease process, the specific antibody titer gradually decreases with the prolongation of the disease course, so the specific antibody is When judging the results of the measurement, it must be considered in combination with clinical manifestations.

A more valuable laboratory test for the determination of anti-bowworm antibodies in aqueous humor. The aqueous antibody titer and serum antibody titer are calculated by the Goldmann-Witmer formula. When the Goldmann-Witmer coefficient exceeds 4, the eye can be diagnosed as an eye bow. Ascariasis, the coefficient is 1 to 4, which is suspicious ocular toxoplasmosis, and the coefficient is less than 1 is negative.

3. Ultrasound examination : Ultrasound examination can provide important clues for the diagnosis of patients with significant vitreous opacity. There are three types of ultrasound examination changes for ocular toxoplasmosis:

1 high reflective solid mass around the periphery of the retina;

2 connected to the posterior pole and the vitreous membrane of the mass;

3 traction retinal detachment or retinal folds extending from the posterior pole to the mass.

4. CT examination: CT examination found intraocular calcification, which is helpful to identify ocular tsutsugamushi disease and retinoblastoma.

Diagnosis and identification of ocular toadstool disease

diagnosis

Patients usually have a history of raising dogs or raising cats. Some patients have heterosexual convulsions. Systemic performance has a suggestive effect on diagnosis. Typical clinical manifestations of the eye have important value for diagnosis. Laboratory tests are important for diagnosis, but arch tsutsugamushi disease The diagnosis is generally difficult because the serum test of Toxoplasma gondii cross-reacts with other ascariasis, the stool test is negative, and some patients do not touch the cat. The history of the dog can only be diagnosed according to the following points:

1. Clinical manifestations: There are mainly eosinophilia, especially the limited granulomatous inflammation of the fundus, and the vitreous is generally turbid.

2. Serum ELISA method: It has high specificity for toxoplasmosis and no obvious cross-reaction with other helminth infections. It is more sensitive with vitreous examination. The disadvantage is that it is not easy for small laboratories to carry out such tests.

3. Aqueous and vitreous absorption: Check eosinophils.

4. Ultrasound examination: Granuloma lesions can be found, which is more favorable for those who cannot see the fundus.

Differential diagnosis

Ocular arch tsutsugamushi should be identified mainly with retinoblastoma, infectious endophthalmitis, intermediate uveitis, ophthalmic toxoplasmosis, retinopathy of prematurity, permanent primordial vitreous hyperplasia, Coats disease, etc.

1. retinoblastoma: ocular toxoplasmosis can cause changes similar to retinoblastoma, especially if both are prone to occur in children, can cause white sputum, but the consequences of the two are very different, Retinoblastoma is extremely harmful and can even cause death of patients. Therefore, retinoblastoma should be excluded in the diagnosis of ocular toxoplasmosis. Eye tsutsugamushi disease occurs mostly in children aged 4 to 8 years, and the mass usually does not increase. Often accompanied by significant inflammatory changes and proliferative vitreous changes, and retinoblastoma is more common in children 22 to 24 months, few of the above two changes, and progressive enlargement of the mass, serum and aqueous humor specific antibody determination Intravitreal cytology, retinal biopsy, etc. are of great value for diagnosis and differential diagnosis.

2. Infectious endophthalmitis: Infective endophthalmitis has a history of trauma, history of internal eye surgery, long-term application of immunosuppressive drugs, diabetes and other medical history, patients have obvious red eyes, eye pain, photophobia, tearing, decreased vision Other symptoms, conjunctival edema, corneal edema, massive anterior chamber fibrinous exudation or anterior chamber empyema, vitreous yellow-white opacity, white or yellow-white borders in the fundus, lesions progress rapidly, blood, urine and eyes Internal liquid bacterial culture, smear examination, etc. are helpful for diagnosis and differential diagnosis.

3. Intermediate uveitis: The central uveitis is typically characterized by a vitreous lesion in the vitreous base and ciliary body flat and snowball opacity in the vitreous, often accompanied by peripheral retinal vasculitis, cystoid macular edema and anterior chamber Inflammatory reaction, prone to opacity of the posterior capsule of the lens, retinal neovascularization and other complications, although the eye tsutsugamushi disease may have snow-like changes, but the age of onset is small, serum and aqueous humor antibody detection is helpful for diagnosis and differential diagnosis .

4. Ocular toxoplasmosis: Ocular toxoplasmosis is also prone to occur in children, and there are many cases of raising dogs and/or cats, but the characteristic changes caused by them are around the retinal choroidal lesions in the posterior pole of the fundus. Active lesions, in addition to causing neuroretinitis, intermediate uveitis, etc., ocular tsutsugamushi disease mainly causes white uplift lesions in the posterior or peripheral part, prone to proliferative vitreoretinopathy and traction retinal detachment, serum And intraocular fluid antibody detection helps differential diagnosis of both.

5. Retinopathy of prematurity: This lesion occurs in premature and low-weight children, involving both eyes, typically showing proliferative lesions, generally without signs of inflammation, while ocular arch tsutsugamushi causes changes in vitreoretinal proliferation. It mainly causes inflammatory changes and has white-induced retinopathy. Specific antibody assays contribute to the diagnosis and differential diagnosis of both.

6. Coats disease: This disease mainly occurs in young males, characterized by the appearance of posterior subretinal white fibrotic lesions with telangiectasia and lipid exudation, but does not cause the anterior membrane of the retina, according to these characteristics It is distinguished from ocular toadstool disease.

The material in this site is intended to be of general informational use and is not intended to constitute medical advice, probable diagnosis, or recommended treatments.