**6. Cestodes infections**

#### **6.1. Cysticercosis**

Cysticercosis is caused by the larval cysts of the tapeworm *Taenia solium.* Humans acquire cysticercosis infection by the consumption of food contaminated with the *Taenia solium* eggs, passed in feces of the infected humans, harboring the adult worms in their intestine as depicted in Figure 17 [216]. Autoinfection has also been reported in persons suffering from taeniasis that may result in cysticercosis. Eating of raw or uncooked pork results in adult worm infection, the taeniasis. It is considered as one of the important neglected parasitic infections (NPIs), prevalent in Asia, Africa and Latin America where poor sanitation conditions prevail (Figure 11) [217]. These larval cyst may lodge into different organs/tissues (brain, muscles, eyes or other tissues) [218], resulting in varying clinical symptoms.

Ocular involvement is well documented and several case reports have documented the orbital, intraocular, subretinal and optic nerve involvement due to cysticercosis [219, 220]. Freefloating cyst can be found in vitreous or anterior chamber of the eye. Cranial nerve or intra‐ ocular muscles lesions may result in gaze palsies [221–223].

Diagnosis is usually established by ophthalmoscopic examination along with imaging evidence of ultrasonography, CT scan or MRI scan. Although serology is easy to perform, it is usually negative in isolated ocular cysticercosis patient [224]. Molecular techniques such as

**Figure 18.** Life cycle of *Echinococcus* (Diagrammatic representation).

conventional PCR, real-time PCR [218] and loop-mediated isothermal amplification (LAMP) [225] can be utilized for establishing the diagnosis of ocular cysticercosis and for genotyping [30, 226]. However, it requires a sophisticated molecular laboratory setup, which is not available widely in developing nations.

Without treatment, symptoms related to visual disturbances persist. Symptoms resolve with surgical and medical treatment [227]. Albendazole along with steroids are the main drugs used in the treatment. Steroid treatment decreases the inflammatory response associated with the antihelminthic therapy around the lesions. Surgical removal of large cysts is recommended where there is an impairment of the vision [224].

#### **6.2. Echinococcosis**

**6. Cestodes infections**

70 Advances in Common Eye Infections

Cysticercosis is caused by the larval cysts of the tapeworm *Taenia solium.* Humans acquire cysticercosis infection by the consumption of food contaminated with the *Taenia solium* eggs, passed in feces of the infected humans, harboring the adult worms in their intestine as depicted in Figure 17 [216]. Autoinfection has also been reported in persons suffering from taeniasis that may result in cysticercosis. Eating of raw or uncooked pork results in adult worm infection, the taeniasis. It is considered as one of the important neglected parasitic infections (NPIs), prevalent in Asia, Africa and Latin America where poor sanitation conditions prevail (Figure 11) [217]. These larval cyst may lodge into different organs/tissues (brain, muscles, eyes or

Ocular involvement is well documented and several case reports have documented the orbital, intraocular, subretinal and optic nerve involvement due to cysticercosis [219, 220]. Freefloating cyst can be found in vitreous or anterior chamber of the eye. Cranial nerve or intra‐

Diagnosis is usually established by ophthalmoscopic examination along with imaging evidence of ultrasonography, CT scan or MRI scan. Although serology is easy to perform, it is usually negative in isolated ocular cysticercosis patient [224]. Molecular techniques such as

other tissues) [218], resulting in varying clinical symptoms.

**Figure 17.** Life cycle of *Taenia solium* (Diagrammatic representation).

ocular muscles lesions may result in gaze palsies [221–223].

**6.1. Cysticercosis**

Echinococcosis/hydatidosis is caused by infection of the larval stages of the *Echinococcus* spp [228], and ocular manifestations occur approximately in 1% of the cases suffering from hydatid disease [229]. Echinococcosis is mainly found in Asia, Africa, Latin America, Russia, Australia and the Mediterranean regions (Figure 11) [230]. It is acquired by the consumption of conta‐ minated food and water with fecal matter containing eggs of *Echinococcus* parasites. The life cycle includes development of adult worms in small bowel of definitive hosts such as dogs and other canids. Eggs are passed in feces and contaminate environment as shown in Figure 18. The symptoms and signs depend on the location of the cyst in the target organ. Most common ocular finding is the development of proptosis due to the presence of intraorbital space occupying lesion. This may further lead to exposure to keratitis and ulceration of the cornea. Other complications due to the local invasion of the expanding cyst may lead to erosion of orbital wall, optic atrophy and optic neuritis. Subretinal hydatid cyst has been reported. In severe cases, blindness may also occur [231].

The diagnosis depends on the clinical findings suggestive of hydatid cyst on ocular examina‐ tion and confirmed by radiological techniques such as ultrasonography, CT scan and/or MRI [232, 233]. "Double wall" sign is a characteristic of orbital hydatid cyst seen by ultrasonography [232]. Serology may also aid in diagnosis. However, in majority of the commercially and inhouse serological assays, hydatid fluid is the main antigenic component and sensitivity of IgG-ELISA reported in various studies varies from 64.8 to 100%, while specificity varies from 87.5 to 100%. Purified and recombinant antigens are also being tried for developing ELISA with high sensitivity and specificity [234]. Fine needle aspiration cytology can also be performed for establishing the diagnosis [235].

Symptoms persist if not treated [236]. Surgical removal of the cyst is the treatment of choice. Medical therapy includes administration of albendazole or mebendazole to prevent the recurrences due to the contents of the cyst leaking into the surgical sites [237]. If the cyst is accidently ruptured, in situ irrigation with hypertonic saline should be performed. However, it causes local inflammatory reaction that may lead to atrophy of optic nerve [238].
