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Philophthalmus is a genus of globally distributed parasitic eye flukes with some members of the genus found in disparate locales. In particular, Philophthalmus gralli, a zoonotic trematode, appears to be a relatively new introduction to the Americas, facilitated by spillover from the invasive snails Melanoides tuberculata (red-rimmed melania) and Tarebia granifera (quilted melania), which were introduced via the aquarium trade, and perhaps furthered by avian dispersal. Given that two known intermediate hosts of Philophthalmus flukes are actively expanding their range as a result of human activities, we hypothesize that this spread is also associated with the spread of Philophthalmus flukes. To address this, we systematically reviewed the literature and examined whether the global expansion of P. gralli flukes is associated with the spread of invasive snails M. tuberculata and T. granifera. Here, we show that (1) specimens of P. gralli are only found in intermediate snail hosts M. tuberculata or T. granifera, suggesting intermediate host specificity for these 2 species, and (2) specimens of P. gralli have rarely been found outside the ranges (native and introduced) of M. tuberculata or T. granifera. Given the importance of distribution information of parasites in the role of identifying parasite invasions, we also review the known distribution of all Philophthalmus species. Considering recent outbreaks in humans and wild and domestic animal species, the continued spread of Philophthalmus presents a potential threat to veterinary and public health and conservation.

The present study aims to evaluate the efficacy of a novel drug delivery system of the modified rice hydrogel containing praziquantel (PZQ) against Philophthalmus gralli isolated from ostrich eyes and determine the toxicity of the preparation on chicken eye model. The parasiticidal activity of PZQ (0, 1, 10, and 100 µg/mL) was tested on P. gralli. The ophthalmic antiparasitic hydrogel was formulated with appropriate amount of PZQ and chemically modified rice gel. The parasitic morphology after exposure with the preparation was examined under scanning electron microscope (SEM). The anthelminthic efficacy of the preparation on motility and mortality of parasites was performed by visual inspection and vital dye staining. The ocular irritation of the preparation was evaluated for 21 days using standard avian model followed by OECD 405. The results demonstrated that the parasiticidal activity of PZQ against P. gralli appears to be in a concentration- and time-dependent manner. In addition, the concentration of PZQ 10 µg/mL (Chi squared test, p = 0.003) and exposure time for 24 h (log-rank test, p = 0.0004) is sufficient to kill parasites, when statistically compared to negative control group. Rice hydrogel containing a lethal concentration of 10 µg/mL PZQ was successfully prepared. The preparation illustrated good parasitic killing and motile inhibiting effect on P. gralli compared with PZQ 10 µg/mL and its control (p < 0.05). An appearance under SEM of non-viable parasite after being incubated with the preparation, showing parasitic deformity, was observed comparing with the viable parasite in 0.9% normal saline solution (NSS). Moreover, no irritation of chicken eyes was also observed. Our results contribute to understanding the efficacy and the safety of the rice hydrogel of PZQ which have a predictive value for controlling P. gralli on the animal eyes. However, the pharmacological application needs to be further investigated for the best possible therapeutic approach.

Minute intestinal flukes from several distinct families of endoparasitic platyhelminths are a medically important group of foodborne trematodes prevalent throughout Southeast Asia and Australasia. Their lifecycle is complex, with freshwater snails as primary intermediate hosts, with infecting multiple species of arthropods and fish as second intermediate hosts, and with birds and mammals including humans as definitive hosts. In Southeast Asian countries, the diversity of snail species of the Thiaridae which are frequently parasitized by trematode species is extremely high. Here, the thiarid Tarebiagranifera in Thailand was studied for variation of trematode infections, by collecting the snails every two months for one year from each locality during the years 2004–2009, and during 2014–2016 when snails from the same localities were collected and new localities found. From ninety locations a total of 15,076 T.granifera were collected and examined for trematode infections. With 1,577 infected snails the infection rate was found to be 10.46 %. The cercariae were categorized into fifteen species from eight morphologically distinguishable types representing several distinct families, viz. (i) virgulate xiphidiocercariae ( Loxogenoidesbicolor , Loxogenesliberum and Acanthatriumhistaense ), (ii) armatae xiphidiocercariae cercariae ( Maritreminoidescaridinae and M.obstipus ); (iii) parapleurophocercous cercariae ( Haplorchispumilio , H.taichui and Stictodoratridactyla ); (iv) pleurophocercous cercariae ( Centrocestusformosanus ); (v) megarulous cercariae ( Philophthalmusgralli ); (vi) furcocercous cercariae ( Cardicolaalseae , Alariamustelae and Transversotremalaruei ); as well as (vii) echinostome-type cercariae, and (viii) gymnocephalous-type cercariae. In addition, a phylogenetic marker (internal transcribed spacers 2, ITS2) was employed in generic and infrageneric level classifications of these trematodes, using sequences obtained from shed cercariae isolated from T.granifera specimens of the second study period collected in various regions in Thailand. We obtained ITS2 sequences of cercariae from nine species (of seven types): Loxogenoidesbicolor , Loxogenesliberum , Maritreminoidesobstipus , Haplorchistaichui , Stictodoratridactyla , Centrocestusformosanus , Philophthalmusgralli , as well as from one species each of echinostome cercariae and gymnocephalous cercariae. Thus, this analysis combines the parasites’ data on morphology and geographical occurrence with molecular phylogeny, aiming to provide the groundwork for future studies looking into more details of the parasite-snail evolutionary relationships.

Melanoides tuberculata that naturally harbored trematode larvae were collected at the Pampulha dam, Belo Horizonte (Minas Gerais, Brazil), during malacological surveys conducted from 2006 to 2010. From 7,164 specimens of M. tuberculata collected, 25 (0.35%) were infected by cercariae, which have been morphologically characterized as belonging to the Megalurous group, genus Philophthalmus. Excysted metacercariae were used for successful experimental infection of Gallus gallus domesticus, and adult parasites recovered from the nictitating membranes of chickens were identified as Philophthalmus gralli. This is the first report of P. gralli in M. tuberculata in Brazil. Melanoides tuberculata naturalmente infectados por larvas de trematódeos foram coletados na represa da Pampulha Belo Horizonte, Minas Gerais, Brasil durante estudos malacológicos realizados entre 2006 e 2010. De 7164 exemplares de M. tuberculata coletados, 25 (0,35%) apresentavam-se infectados por cercárias que foram caracterizadas morfologicamente como pertencentes ao grupo Megalura, gênero Philophthalmus. Metacercárias desencistadas foram utilizadas com sucesso para a infecção experimental de Gallus gallus domesticus e parasitos adultos recuperados da membrana nictitante das aves foram identificados como Philophthalmus gralli. Este é o primeiro relato de P. gralli em M. tuberculata no Brasil

A total of 17 commercially reared ostriches (Struthio camelus) from Msengi farm, Chinhoyi, Zimbabwe, observed with swollen eyes, severe conjunctivitis and constant lacrimation accompanied by a purulent exudate, were restrained for further clinical examination. Some of the birds were semi-blind with severe loss of body condition. When examined, tiny organisms were observed attached to the nictitating membranes and the conjuctival sacs of both eyes. The organisms were identified as Philophthalmus gralli, the \"oriental eye-fluke\" and Melanoides tuberculata, a prosobranch snail, was confirmed as the intermediate host through natural and experimental infection. To the best of our knowledge this is the first record of the oriental eye-fluke infection in birds in Zimbabwe and Africa and extends its known geographical range.

This paper reports the occurrence of parasitism by the Oriental eye-fluke, Philophthalmus gralli in ostriches reared in a commercial flock from the State of Minas Gerais State, Southeastern Brazil. The two affected birds presented lacrimation, inflammatory reaction and loss of body condition. After physical examination the birds revealed, 17 and 15 trematodes each, only in the right eyes. The economic impact of this parasite on Brazilian ostrich industry is still undetermined, requiring further studies.

A total of 17 commercially reared ostriches (Struthio camelus) from Msengi farm, Chinhoyi, Zimbabwe, observed with swollen eyes, severe conjunctivitis and constant lacrimation accompanied by a purulent exudate, were restrained for further clinical examination. Some of the birds were semi-blind with severe loss of body condition. When examined, tiny organisms were observed attached to the nictitating membranes and the conjuctival sacs of both eyes. The organisms were identified as Philophthalmus gralli, the \"oriental eye-fluke\" and Melanoides tuberculata, a prosobranch snail, was confirmed as the intermediate host through natural and experimental infection. To the best of our knowledge this is the first record of the oriental eye-fluke infection in birds in Zimbabwe and Africa and extends its known geographical range.

General features observed on the surface of Philophthalmus megalurus and Philophthalmus gralli rediae include 2 rounded ambulatory buds, a tapered tail, a slitlike birth pore, and an oral opening surrounded by uniciliate sensory receptors. The tegument is folded in a ribbed pattern and is covered with small microvilli. The sensory receptors are concentrated on the lip of the oral opening but are less dense inside the buccal cavity. Both the birth pore and the buccal cavity are lined with a honeycomblike surface that may support the structural integrity of these highly extensible orifices. Major differences between the 2 species were noted in the structure of the sensory receptors. In P. megalurus they have flexible cilia that originate from a bulbous tegumental base. Receptors of P. gralli rediae are less dense, appear to have rigid cilia, and lack a bulbous base. In general P. megalurus rediae resemble more closely rediae of the philophthalmid Parorchis acanthus than they do those of P. gralli.