Philophthalmus gralli

Philophthalmus gralli, commonly known as the Oriental avian eye fluke, parasitises the conjunctival sac of the eyes of many species of birds, including birds of the orders Galliformes and Anseriformes.[2] In Brazil this parasite was reported in native Anseriformes species.[3] It was first discovered by Mathis and Leger in 1910 in domestic chickens from Hanoi, Vietnam.[1] Birds are definitive hosts and freshwater snail species are intermediate hosts (e.g. Tarebia granifera and Melanoides tuberculata).[4] Human cases of philophthalmosis are rare, but have been previously reported in Europe, Asia, and America (i.e., Yugoslavia, Sri Lanka, Japan, Israel, Mexico, and the United States).

Philophthalmus gralli
Scientific classification
Kingdom: Animalia
Phylum: Platyhelminthes
Class: Rhabditophora
Order: Plagiorchiida
Family: Philophthalmidae
Genus: Philophthalmus
Species:
P. gralli
Binomial name
Philophthalmus gralli
Mathis & Leger, 1910[1]

Life cycle

Philophthalmus gralli reaches sexual maturity in a bird and produces eggs. Fully embryonated eggs are shed into the water from the definitive host's eyes. Miracidium is induced to hatch when ripe eggs are released from the worm into water. Upon contact with a snail, the miracidium perforates the host epidermis with the aid of secretions and the anterior cilia. It penetrates the snail far enough to release a single rediae. The mother redia localizes in the heart and produces daughter rediae, which migrate to digestive glands to continue its development and produce megalurous 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. Excystment of the metacercariae occurs immediately upon reaching the mouth or crop of the bird and not in the stomach or intestine as in many other digenetic trematodes. Within three to five hours after ingestion, immature worms may be found in the esophagus, nasal passages, the orbit and the lobes of the lacrimal gland. Humans rarely serve as incidental hosts, but may do so when they ingest metacercariae on aquatic vegetation.[5]

Morphology

The P. gralli egg is nonoperculate and oval. The shell is thin and elastic and has an internal thickening at the small end.

The miracidia is composed of twenty epidermal plates arranged in four tiers, which have six, eight, four, and two cells, respectively. It consists of two excretory pores and two pairs of lateral sensory papillae.

The morphology of a redia is elongated and cylindrical. It has a well-developed anterior pharynx and a long intestinal tract. Birth pore is found between first and second quarter of body. Lateral processes are near posterior tip of body.

The cercaria has two suckers: a ventral sucker and rounded subterminal sucker. Intestinal ceca bifurcate posterior to pharynx. Excretory bladders are located at posterior end of the cercarial body.

The metacercarial cyst is elongated and oval-shaped with sensory papillae. The excysted metacercarial is oval-shaped with a subterminal sucker and a ventral sucker.

The adult form of P. gralli is fusiform shaped. Body surface is covered by small spines at acetabular region. The two suckers are orally and subterminally located. Pharynx is located immediately posterior to oral sucker. Acetabulum is located at anterior third level of body. Both female and male organs are found within the body.[5]

Therapy

The most common way to rid of Philophthalmus gralli is removal with forceps or flushing the worms out. Doramectin may also be used.[6]

Clinical symptoms

Clinical symptoms are a result of flukes attaching to the conjunctiva. It has different effects, depending on the host. Infection may cause congestion and erosion of the conjunctivae,[7] conjunctivitis with persistent lacrimation,[8] and semilunar fold swelling[9] in chickens, ostriches, and humans, respectively.

Infections in ostriches

The first case of philophthalmiasis in captive-reared ostriches was described in the United States in 1980.[8] An outbreak of Philophthalmus gralli has been reported in 2005 in ostriches in Zimbabwe; 17 were found to be infected by this parasite. They had swollen eyes, severe conjunctivitis, and constant lacrimation, accompanied by a purulent exudates. A fraction of the birds became semi-blind from the infection.[4]

Philophthalmus gralliPARASITE SUMMARY
Alternative Names:Philopthalmus anatinus, Philopthalmus nyrocae
DescriptionFluke
Systems affectedEye - conjunctival sac.
Life cycleEggs escape from eye and mouth or nostrils of final host, hatch immediately after contact with water; cercariae develop in fresh-water immediately after contact with fresh-water prosobranch snail in 95 days after infection, encyst on surfaces shortly after emergence; metacercariae ingested by final host, make way to conjunctival sac, mature in 24–29 days after ingestion.
Geographic distributionVietnam, USA (Florida and Hawaii), Indochina, Formosa, Europe (USSR - Dnieper River) and Africa.[4]
Associated Waterfowl DiseasesOcular Fluke Infection (Philophthalmus gralli infection, Oriental eyefluke infection, Ocular trematode infection)
Waterfowl Disease SummaryOcular infection due to a trematode (fluke).

References
  1. Mathis, C.; Leger, M. (1910). "Douve oculaire de la poule". Bulletin de la Société de Pathologie Exotique (in French). 3: 245–251.
  2. Nollen, PM; Murray, HD (February 1978). "Philophthalmus gralli: identification, growth characteristics, and treatment of an oriental eyefluke of birds introduced into the continental United States". Journal of Parasitology. 64 (1): 178–80. doi:10.2307/3279646. JSTOR 3279646. PMID 627963.
  3. Muniz-Pereira, Luís Cláudio; Amato, Suzana B. (December 1993). "Philophthalmus gralli (Digenea: Philophthalmidae) parasite of Anas bahamensis and Amazonetta brasiliensis, from Lagoons of Maricá county, Rio de Janeiro, Brazil". Memórias do Instituto Oswaldo Cruz. 88 (4): 567–569. doi:10.1590/S0074-02761993000400012.
  4. Mukaratirwa, S; Hove, T; Cindzi, ZM; Maononga, DB; Taruvinga, M; Matenga, E (September 2005). "First report of a field outbreak of the oriental eye-fluke, Philophthalmus gralli (Mathis & Leger 1910), in commercially reared ostriches (Struthio camelus) in Zimbabwe". Onderstepoort Journal of Veterinary Research. 72 (3): 203–6. doi:10.4102/ojvr.v72i3.197. PMID 16300188.
  5. West, A. Fred (October 1961). "Studies on the biology of Philophthalmus gralli Mathis and Leger, 1910 (Trematoda: Digenea)". American Midland Naturalist. 66 (2): 363. doi:10.2307/2423036. JSTOR 2423036.
  6. Martin, Charles L. (2009). "Chapter 8. Conjunctiva and third eyelid. Parasitic conjunctivitis". Ophthalmic Disease in Veterinary Medicine. CRC Press. p. 196. ISBN 9781840765953.
  7. Kingston, N. 1984. Trematodes, in Diseases of poultry, edited by M. S. Hofstad. Ames: Iowa University Press.
  8. Greve, JH; Harrison, GJ (1 November 1980). "Conjunctivitis caused by eye flukes in captive-reared ostriches". Journal of the American Veterinary Medical Association. 177 (9): 909–10. PMID 7451339.
  9. Mimori, T; Hirai, H; Kifune, T; Inada, K (July 1982). "Philophthalmus sp. (Trematoda) in a human eye". American Journal of Tropical Medicine and Hygiene. 31 (4): 859–61. doi:10.4269/ajtmh.1982.31.859. PMID 7102921.

"Philophthalmus gralli". Integrated Taxonomic Information System.

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