Pathology and first report of natural infections of the eye trematode Philophthalmus lachrymosus Braun, 1902 (Digenea, Philophthalmidae) in a non-human mammalian host

A Molecular Phylogenetic Study of the Eye Fluke Philophthalmus lacrymosus (Trematoda: Philophthalmidae) Found in Larus dominicanus (Aves: Laridae) from Brazil

PURPOSE

Species of the genus Philophthalmus are eye flukes with a complex taxonomy, which began to be improved with the help of molecular data only recently. However, most described species have never been placed into a phylogenetic context. In this study, eye flukes previously found on kelp gulls, Larus dominicanus, from Brazil and identified as Philophthalmus lacrymosus were subjected to molecular analysis.

METHODS

For the molecular analyses, we analyzed parasites found in six infected gulls (one worm per bird) collected from different municipalities of the state of Santa Catarina, Brazil. We carried out the amplification and sequencing of the partial region of the 28S and cox1 genes and the data obtained were compared with sequences available to philophthalmid species and subjected to phylogenetic analysis.

RESULTS

The isolates of P. lacrymosus from Brazil grouped in well-supported clades with five other species of Philophthalmus with sequences available for comparison. Interspecific divergences of 0.1-1.6% in 28S and 8.2-14.9% in cox1 were found in relation to other isolates of Philophthalmus spp. Two cox1 haplotypes differing in one nucleotide (0.1%) were found between the six eye flukes isolates in gulls from different localities. The Brazilian isolates grouped in a subclade with parasites identified as P. lacrymosus in Portugal; however, the molecular divergences found in cox1 (8.2-8.5%) strongly suggest that these isolates belong to different species. The phylogenetic trees obtained and the intergeneric divergences to species of the genera Cloacitrema and Parorchis did not support the validity of the genus Natterophthalmus, for which P. lacrymosus was proposed as the type species in the past.

CONCLUSION

As P. lacrymosus was described from Brazil, we recommend that this name be applied to the South American isolates and that the Portuguese isolates be provisionally considered as Philophthalmus sp., a probable cryptic species. Moreover, data obtained supports the previous morphology-based synonymizing between Natterophthalmus and Philophthalmus. Considering our results and most of previous reports of P. lacrymosus in South America, we suggest this species presents a marine life cycle.

Outbreaks of philophthalmiasis in ostriches (Struthio camelus) in Northeast Brazil

ABSTRACT: This study discusses the epidemiological, clinical, and pathological characteristics of two outbreaks of ocular infection in ostriches (Struthio camelus) caused by the trematode Philophthalmus sp. The outbreaks occurred in the states of Ceará and Rio Grande do Norte in Northeast Brazil. Ostrich farming was categorized as semi-intensive farming with free access to the weir and river. The clinical symptoms for infection included nictitating membrane inflammation, epiphora (tearing), eyelid edema, ocular congestion, eyeball destruction, emaciation, and death, and the infection period ranged from 8 to 16 months. Macroscopically, thickening of the eyelids and conjunctiva were observed, with orange parasites infestation. Histologically, the lesions were characterized as lymphoplasmacytic and heterophilic, multifocal to coalescing, moderate, chronic conjunctivitis associated with hyperplasia and ectasia of the Harderian gland, and numerous parasites. The parasites were oval and flattened with an oral suction cup, acetabulum, and thick cuticle containing spicules. The diagnosis of philophthalmiasis was based on epidemiological, clinical, and pathological findings associated with the morphological characteristics of the parasites present in the conjunctival sacs which were similar to the trematode Philophthalmus sp. Philophthalmiasis can occur in ostriches raised on urban and rural properties in Northeastern Brazil, probably associated with the contact of birds with contaminated water, and is characterized by severe conjunctivitis that can result in the loss of the eyeball and death of the animals.

Identification and molecular characterization of digenean trematode parasites of Aylacostoma chloroticum (Gastropoda: Thiaridae) from a Neotropical Basin

Thiarids are pantropical gastropods distributed from South America to Australia and found in lentic and lotic freshwater environments. These gastropods act as intermediate hosts for several species of digeneans. There are difficulties in the correct identification of these digeneans in certain stages of the life cycle as the larvae have a reduced size and few morphological characteristics for diagnosis. Because of this, techniques based on molecular markers have become an extremely useful tool. Our objective was to molecularly characterize the digeneans found in gastropods from the Ivaí River, Paraná, Brazil, using the mitochondrial molecular marker cytochrome c oxidase (COI) and the 28S ribosomal marker. With the molecular marker COI, gastropods showed high genetic similarity with Aylacostoma chloroticum. For the parasites, four different taxa were characterized with both markers. The 28S ribosomal marker proved to be more effective for the identification of Ivaí River parasites, being possible to suggest the identification of two species among the four groups found. Considering that there are no records in the literature of studies involving parasites and gastropods as intermediate hosts in the Ivaí River, this study is the first regarding these relationships.

Ocular disease caused by the trematode Philophthalmus lachrymosus in free-living kelp gulls (Larus dominicanus) of Brazil

In this study, clinical, parasitological and histopathological findings of thirteen kelp gulls (Larus dominicanus) found infected with eyeflukes in Brazil are presented. Parasites detected in the ventral conjunctival fornix were identified as Philophthalmus lachrymosus [mean intensity of infection: 16 (5-36) worms/bird]. Eleven birds (85%) presented signs of systemic disease, such as emaciation, dehydration and depressed consciousness. Conjunctival hyperemia was observed in 22 eyes (85%). Keratitis, corneal ulcers, corneal abscess and chemosis were also detected in some eyes (4-8%). Histopathologic lesions, likely due to the parasite attachment to the conjunctiva, were found in the eyes of one infected bird that died from unrelated causes. Philophthalmosis by P. lachrymosus is here reported as a clinically relevant eye disease in kelp gulls.

Philophthalmus gralli in domestic waterfowl: An environmental study in an urban area from Brazil

Philophthalmosis is a zoonotic ocular disease that affects mainly domestic and wild avian species in different parts of the world. However, aspects related to its epizoology in domestic animals are not completely known. In the present study, 47 Muscovy duck (Cairina moschata), 8 mallards (Anas platyrhynchos platyrhynchos) and 6 African geese (Anser cygnoides), free-living in an urban lake in Belo Horizonte, Minas Gerais, Brazil, were evaluated for eye fluke infection. The animals were manually contained, and the conjunctival sac and nictitating membrane were evaluated by direct ophthalmic examination (DOE), in which the fluke burden was estimated by a semiquantitative scale. Moreover, the conjunctival sac lavage (CSL) technique was applied for the search of parasite eggs. When possible, the detected trematodes were carefully removed for fixed for taxonomic identification. In order to characterize the parasite-host-environmental system, malacological collections were performed at the locality, and the collected intermediate host mollusks (Melanoides tuberculata) were evaluated for infection with larval philophthalmids. In addition, wild vertebrates found dead in the locality, including one common gallinule (Gallinula galeata) and two capybaras (Hydrochoerus hydrochaeris), were necropsied for the search of eye flukes. Samples from the developmental stages obtained from the hosts were subjected to morphological and molecular studies (amplification and sequencing of a partial region of the Nad-1 gene). In the DOE, the presence of eye flukes was verified in 67% (4/6), 31% (15/47) and 25% (2/8) in geese, Muscovy ducks and mallards, respectively. In most cases, the birds showed mild parasitism (1-5 trematodes), with no apparent eye damage, characterizing a subclinical infection. In only one goose, which had a high fluke burden (20 trematodes), it was possible to obtain eggs by CSL. Regarding the malacological survey, 73/4545 (1.6%) specimens of M. tuberculata evaluated were found infected with megalurous cercariae, compatible with representatives of the family Philophthalmidae. Additionally, 147 flukes were recovered from a specimen of G. galeata found dead at the lake. The morphological and molecular study of parasites obtained from different hosts evaluated in this study enabled the identification of Philophthalmus gralli, a species native from Asia and introduced in the Americas. Factors such as the wide distribution of the intermediate host and the participation of domestic and wild reservoirs in the parasite transmission chain may favor the occurrence of parasite spillover from wild to domestic birds. Furthermore, the occurrence of the life cycle of P. gralli in an urban waterbody serves as an alert to the possibility of human cases of this zoonotic eye parasite.

Parasites Circulating in Wild Synanthropic Capybaras (Hydrochoerus hydrochaeris): A One Health Approach

Capybaras (Hydrochoerus hydrochaeris) are affected by a wide range of protozoan and metazoan-derived parasitic diseases. Among parasites of free-ranging capybaras are soil-, water-, food- and gastropod-borne parasitosis, today considered as opportunistic infections in semiaquatic ecosystems. The overlapping of the capybara’s natural ecological habitats with human and domestic animal activities has unfortunately increased in recent decades, thereby enhancing possible cross- or spillover events of zoonotic parasites. Due to this, three synanthropic wild capybara populations in the Orinoco Basin were studied for the occurrence of gastrointestinal parasite infections. A total of forty-six fecal samples were collected from free-ranging capybaras in close proximity to livestock farms. Macroscopical analyses, standard copromicroscopical techniques, coproELISA, PCR, and phylogenetic analysis revealed thirteen parasite taxa. In detail, the study indicates stages of five protozoans, four nematodes, one cestode, and three trematodes. Two zoonotic parasites were identified (i.e., Plagorchis muris, and Neobalantidium coli). The trematode P. muris represents the first report within South America. In addition, this report expands the geographical distribution range of echinocoelosis (Echinocoleus hydrochoeri). Overall, parasitological findings include two new host records (i.e., P. muris, and Entamoeba). The present findings collectively constitute baseline data for future monitoring of wildlife-derived anthropozoonotic parasites and call for future research on the health and the ecological impact of this largest semiaquatic rodent closely linked to humans, domestic and wild animals.

Spread of An Avian Eye Fluke, Philophthalmus gralli, Through Biological Invasion of An Intermediate Host

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.

EVALUATION OF THE OPHTHALMIC DISEASE AND HISTOPATHOLOGIC EFFECTS DUE TO THE OCULAR TREMATODE PHILOPHTHALMUS ZALOPHI ON JUVENILE GALAPAGOS SEA LIONS ( ZALOPHUS WOLLEBAEKI)

The Galapagos sea lion ( Zalophus wollebaeki) is an otariid species endemic to the Galapagos archipelago and is currently listed as endangered. The ocular trematode Philophthalmus zalophi was recently reported to affect the survival of juvenile Galapagos sea lions on Santa Cruz Island, resulting in marked ophthalmic changes. This study evaluated the ophthalmic disease and histopathologic effects of P. zalophi on juvenile Galapagos sea lions in the largest rookery located on San Cristóbal Island. Twenty juvenile Galapagos sea lions (10 male and 10 female) were evaluated among five sites in the rookery El Malecón. Ophthalmic examination, including fluorescein staining and evaluation of the adnexa, cornea, and sclera, were performed on each eye. The presence, number, and location of ocular parasites were determined, and parasites were collected for identification. Conjunctival biopsy was performed on 11 animals: 2 that lacked parasites and gross lesions and 9 with both parasites and gross lesions. All parasites collected were confirmed as P. zalophi and identified in 80% (16/20) of the study animals and 70% (28/40) of the examined eyes. Philophthalmus zalophi was most frequently found attached to the nictitating membrane but also located on the palpebral conjunctiva or cornea. The most common clinical signs were varying degrees of conjunctival hyperemia (28/40 eyes), most frequently of the nictitating membrane and mucoid ocular discharge (12/40 eyes). The number of parasites was significantly associated with the degree of conjunctival hyperemia ( P < 0.001). Histopathology of conjunctival biopsies revealed organized lymphoid follicles and lymphoplasmacytic infiltrates. The histopathologic changes and gross lesions were likely due to the parasite's attachment to the conjunctiva. This study provides additional details of P. zalophi infection in juvenile Galapagos sea lions. Further research is warranted to detail the life cycle of this parasite, transmission to sea lions, and potential treatment protocols.

Ocular Trematodiasis Caused by the Avian Eye Fluke Philophthalmus in Southern Texas

A trematode identified as a Philophthalmus sp was extracted from the bulbar conjunctiva of a patient in southern Texas with short-distance travel to Mexico. This parasite is very rarely reported from humans, and species identification is challenging. Aspects of diagnosis, zoonotic transmission, and unresolved questions about Philophthalmus spp are discussed.

Experimental avian philophthalmosis: Evaluation of diagnosis and treatment of chickens infected with Philophthalmus gralli (Trematoda: Philophthalmidae)

The trematodes of the genus Philophthalmus are eye flukes that cause damage to ocular structures of animals and humans. Despite the increasing number of cases reported in birds, studies related to the diagnosis of subclinical philophthalmosis are lacking, and there are no effective therapeutic regimens available. In the present study, we evaluated the diagnosis and treatment of philophthalmosis in specific pathogen-free chickens (Gallus gallus domesticus) experimentally infected with Philophthalmus gralli. Four chickens were inoculated with metacercariae of P. gralli (20 per eye) obtained from cercariae emerged from naturally infected Melanoides tuberculata. From 90 days post-infection, the chickens were subjected to direct ophthalmic examination (DOE) and conjunctival sac lavage (CSL). The latter technique consisted of lavage of each eye with 200 μL sterile saline solution and subsequent microscopical examination of the collected fluid for the presence of eggs of P. gralli. The anthelminthic treatment protocols included praziquantel (PZQ) at 10, 50, or 100 mg/kg (single dose given intramuscularly), or fenbendazole (FBZ) at 50 mg/kg (three doses at 24 h-intervals given per os). The treatment protocols were performed at 14 day-intervals between each dosage of PZQ. Chickens developed a minimum of one to more than five adult P. gralli per eye, except for one chicken that had a single eye with one parasite. No ocular clinical signs or changes in behavior were noted in any chickens. DOE and CSL were considered techniques with similar sensitivity for the diagnosis of avian philophthalmosis. The data suggested that PZQ and FBZ, at the dosages and schedules employed, are not effective for the complete elimination of P. gralli. CSL is proposed as a complementary technique for the diagnosis and monitoring of philophthalmosis post-treatment, especially in subclinical cases. The evaluation of new protocols, routes of administration, and anthelmintic drugs are needed for successful pharmacological treatment of philophthalmosis.

Pathology and first report of natural eye infection with the trematode Philophthalmus gralli (Digenea, Philophthalmidae) in Tinamus major (Tinamiformes, Tinamidae), Costa Rica

The eye-fluke Philophthalmus gralli (Philophthalmidae Looss, 1899) was found in six birds known as great tinamous (Tinamus major) reared in a wild animal shelter located in Alajuela, Costa Rica. The birds presented conjunctival hyperemia, blepharitis, anorexia and weakness. Some of them suffered from unilateral blindness and ocular loss. After morphometric analysis, the specimens showed characteristics compatible with the digenean trematode P. gralli. The clinical signs of infection were resolved by manual removal of the adults, treatment with praziquantel and relocation into an environment without a natural water source. In order to determine if an ongoing cycle of this pathogen was present in the shelter, the habitat of the birds was inspected for the presence of infected intermediate hosts and contaminated water and objects. It was found that the snails Melanoides tuberculata acted as the intermediate host, and reared the infectious stages toward other animals, as shown by the reproduction of ocular philophthalmiasis in chickens artificially infected with excysted metacercaria. Moreover, three out of every ten snails found in the place were infected with rediae of P. gralli, raising the possibility of the dispersion of the parasite into new environments as well as the imminent zoonotic risk. The finding of P. gralli in Costa Rica is the first official report in Central America.

Melanoides tuberculata as intermediate host of Philophthalmus gralli in Brazil

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.

Human waterborne trematode and protozoan infections

Waterborne trematode and protozoan infections inflict considerable morbidity on healthy, i.e., immunocompetent people, and may cause life-threatening diseases among immunocompromised and immunosuppressed populations. These infections are common, easily transmissible, and maintain a worldwide distribution, although waterborne trematode infections remain predominantly confined to the developing countries. Waterborne transmission of trematodes is enhanced by cultural practices of eating raw or inadequately cooked food, socio-economical factors, and wide zoonotic and sylvatic reservoirs of these helminths. Waterborne protozoan infections remain common in both developed and developing countries (although better statistics exist for developed countries), and their transmission is facilitated via contacts with recreational and surface waters, or via consumption of contaminated drinking water. The transmissive stages of human protozoan parasites are small, shed in large numbers in feces of infected people or animals, resistant to environmental stressors while in the environment, and few are (e.g., Cryptosporidium oocysts) able to resist standard disinfection applied to drinking water.