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Philophthalmus gralli

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Philophthalmus gralli (P. gralli) was found in the conjunctival sacs of birds causing congestion and erosion of the conjunctiva. It is also called oriental avian eye fluke. The oriental eye fluke was described to parasite the conjunctiva sac of various galliforms and anseriforms (Nollen and Murray 1978). Also this fluke was found in ostriches, causing conjunctivitis. Greve and Harrison (1980) described the first case of philophthalmiasis in captive reared ostriches in the United States. Mukaratirwa et al. (2005) reported a field outbreak of P. gralli in commercially reared ostriches in Zimbabwe, where 17 affected birds presented swollen eyes, severe conjunctivitis and constant lacrimation accompanied by a purulent exudates. In Brazil this parasitism was reported in native anseriforms species (Muniz-Pereira and Amato 1993).

Trematode species in the Family Philophthalmidae parasitize the eyes of birds. Human cases of philophthalmosis have been previously reported in Europe, Asia, and America (i.e., Yugoslavia, Sri Lanka, Japan, Israel, Mexico, and the United States). The worm was reported as Philophthalmus lacrimosus, Philophthalmus palpebrarum, or an uncertained species.


Life Cycle

Fully-embryonated eggs are shed into the water from the definitive host’s eyes . Miracidia hatch almost immediately in water and penetrate the snail intermediate host . Several snail genera may serve as intermediate hosts, including Thiara spp. and Melanoides spp. Inside the snail host, the miracidia (which contain a pre-formed redia) undergo a series of stages ( , ) and become cercariae. Cercariae are released from the snail and encyst on aquatic vegetation or other solid objects in the water . The definitive host, which is usually an aquatic bird, becomes infected upon ingestion of metacercariae . Metacercariae excyst in the mouth and migrate to the eye where the adults reside . Humans rarely serve as incidental hosts, but may do so when they ingest metacercariae on aquatic vegetation .

Caption text

The life cycle requires only two hosts. The adult lives in the eyes of bird definitive host and produces eggs containing eye-spotted miracidia that hatch immediately when they reach water. Miracidia infect snails first intermediate host and develop to redia and cercariae. The metacercariae encyst freely and openly, including on surfaces of food for birds. Successful direct infection of the definitive host of both cercariae and metacercariae can take place by entering the eye or by oral intake.