Lesions caused by anisakid and capillariid in Cairina moschata raised on Marajó island, state of Pará, Brazil / [Lesões por anisakideos e capillariideos em Cairina moschata criados na Ilha de Marajó, estado do Pará, Brasil]

The Muscovy duck is a commercially important bird on the island of Marajó usually raised in a peculiar system that includes supplying fish viscera to the birds under semi-extensive farming conditions. This enables a risk of contamination and losses in the production of these birds, resulting from injuries caused by helminth infections, especially nematodes. The objective of this study was to evaluate the histopathological changes caused by nematodes of the genera: Eucoleus, Anisakis and Contracaecum. Thirty-three ducks with lesions in the esophagus and ventricle were analyzed. Histopathological exams showed a mild inflammatory infiltrate in the submucosa of the esophagus caused by the fixation of E. contortus and third stage larvae of Anisakis sp., and we recorded third stage larvae of Contracaecum sp. parasitizing the ventricle, this being the first record of this parasite in ducks in Brazil.(AU)

O pato doméstico é uma ave amplamente comercializada na Ilha de Marajó, com um peculiar manejo que inclui a oferta de vísceras de peixes aos animais em criações semiextensivas, propiciando, assim, risco de contaminação e perdas na produção dessas aves decorrentes de lesões oriundas de infecções por helmintos, especialmente os nematódeos. Nesse sentido, objetivou-se avaliar as alterações histopatológicas causadas por nematódeos dos gêneros: Eucoleus, Anisakis e Contracaecum. Foram analisados 33 patos, e três exemplares apresentaram lesões no esôfago e no ventrículo. Exames histopatológicos demonstraram discreto infiltrado inflamatório na submucosa do esôfago ocasionado pela fixação de E. contortus e larvas de terceiro estágio de Anisakis sp., bem como foram registradas larvas de terceiro estágio de Contracaecum sp. parasitando o ventrículo, sendo esse o primeiro registro desse parasito em patos no Brasil.(AU)

First case of Plasmodium relictum lineage pGRW11 infection in a captive-bred common eider (Somateria Mollissima) in Europe.

A 4-year-old, female common Eider (Somateria mollissima) was presented for mild lethargy with no previous medical history. Numerous intraerythrocytic, round-shaped inclusions were visualized on blood smears, later morphologically identified as Plasmodium relictum parasites. Despite oral doxycycline treatment, clinical condition declined 48 h later. Supportive care was initiated, but the bird died rapidly. Necropsy revealed acute, internal hemorrhages (lungs, air sacs) and subcutaneous, diffuse cervical hematoma, associated with resuscitation attempts. Marked, multicentric amyloidosis (kidney, liver, spleen) was the main histological finding. Molecular analysis identified lineage pGRW11 of P. relictum. This is the first reported case of P. relictum lineage pGRW11 infection in a common Eider. This report describes the clinical features, diagnosis, treatment and associated pathological findings of infection by P. relictum lineage pGRW11 in a common Eider.

Helminths of the mallard Anas platyrhynchos Linnaeus, 1758 from Austria, with emphasis on the morphological variability of Polymorphus minutus Goeze, 1782.

The mallard Anas platyrhynchos is the most abundant water bird species in Austria, but there is no record of its helminth community. Therefore, this work aimed to close that gap by recording and analysing the parasite community of a large number of birds from Austria for the first time. A total of 60 specimens shot by hunters in autumn were examined for intestinal parasites. The following taxa were recovered (prevalence given in parentheses): Cestoda: Diorchis sp. (31.7%) and Fimbriarioides intermedia (1.7%); Acanthocephala: Filicollis anatis (5%), Polymorphus minutus (30%) and one cystacanth unidentified (1.7%); Trematoda: Apatemon gracilis (3.3%), Echinostoma grandis (6.7%), Echinostoma revolutum (6.7%) and Notocotylus attenuatus (23.3%); Nematoda: Porrocaecum crassum (1.7%) and one not identified (1.7%). The frequency distribution of parasites showed a typical pattern in which 39 birds (65%) were either not parasitized or were harbouring up to five worms, whereas more intense infestations occurred in a lesser number of hosts. Compared to other studies from central and eastern Europe, an extremely depauperate helminth community, particularly of the cestodes and nematodes, was found. Polymorphus minutus was observed as having highly variable morphology and, therefore, molecular genetic characterization by DNA barcoding was carried out. Species identification was confirmed by comparing data with the reference cytochrome c oxidase subunit 1 gene sequence from P. minutus available in GenBank.

It is marine: distinguishing a new species of Catatropis (Digenea: Notocotylidae) from its freshwater twin.

The morphology of sexual adults is the cornerstone of digenean systematics. In addition, life cycle data have always been significant. The integration of these approaches, supplemented with molecular data, has allowed us to detect a new species that many researchers may have previously seen, but not recognized. Sexual adults from common eiders that we found in northern European seas were extremely similar to other notocotylids, but the discovery of their intermediate host, a marine snail, revealed the true nature of this material. Here we describe sexual adults, rediae and cercariae of Catatropis onobae sp. nov. We discuss how 'Catatropis verrucosa' should be regarded, justify designation of the new species C. onobae for our material and explain why it can be considered a cryptic species. The phylogenetic position of C. onobae within Notocotylidae, along with other evidence, highlights the challenges for the taxonomy of the family, for which two major genera appear to be polyphyletic and life cycle data likely undervalued.

Morphological comparison of genetically differentiated Polymorphus cf. minutus types.

In the present study, we analyzed the morphology of three genetic types of the bird-infecting acanthocephalan Polymorphus cf. minutus (PspT1, PspT2, PspT3), mainly based on the cystacanth-stage obtained from amphipods (Gammarus fossarum, Gammarus pulex, Gammarus roeselii, Echinogammarus spp.). Males and females were pooled as there was no considerable difference between the sexes concerning the hook measurements. Additionally, we conducted a laboratory infection of one domestic duck for each Polymorphus type, to compare their performance and localization in this host species, and to obtain adult specimens for morphological comparison. The recovery rate from the ducks 4 weeks after infection was 16% for PspT1, 23.8% for PspT2, and 25% for PspT3. The adult worms were gravid, and the females contained mature eggs. Hook size did not differ considerably between cystacanths and adults of the respective type. The three Polymorphus types could be distinguished based on the cystacanth stage by a linear discriminant analysis that included hook measurements, proboscis length, proboscis width, and number of longitudinal hook rows and hooks per row. Furthermore, PspT3 was more different from PspT1 and PspT2 than the latter types from each other. Mainly the number of longitudinal hook rows differed in PspT3 from the existing descriptions of P. minutus (mainly 14 vs. mainly 16 rows). Potentially, PspT3 could be a non-indigenous parasite that was introduced with G. roeselii and that adapted to use the indigenous G. pulex as a host, while PspT2 might have been introduced to central Europe together with Echinogammarus spp.

First report of Anisakis sp. (Nematoda: Anisakidae) parasitizing Muscovy duck in Marajó Island, state of Pará, Brazil / Primeiro relato de Anisakis sp. (Nematoda: Anisakidae) parasitando pato doméstico na Ilha de Marajó, estado do Pará, Brasil

Abstract Among the avian used for human consumption, the Muscovy duck is well adapted to various climatic conditions and its breeding is widespread due to its easy handling, and its meat is widely consumed and appreciated, especially in the cuisine of northern Brazil. The present study aimed to report and identify taxonomically the nematodes found in the esophagus of Muscovy ducks reared and marketed in the municipality of Soure, Marajó Island, state of Pará, Brazil, and discuss its zoonotic potential to human. The samples consisted of 30 specimens of Cairina moschata domestica analyzed. A total of 258 nematodes were recovered, which were strongly fixed in the esophageal mucosa of hosts. The morphological and morphometric characteristics were compatible with Anisakis third-stage larvae.

Resumo Entre as aves utilizadas para consumo humano, o pato doméstico está bem adaptado às várias condições climáticas. Sua criação é muito difundida devido ao seu fácil manejo. E sua carne é amplamente consumida e apreciada, principalmente na culinária do norte do Brasil. O presente estudo teve como objetivo relatar e identificar taxonomicamente os nematódeos encontrados no esôfago de patos domésticos, criados e comercializados no município de Soure, Ilha de Marajó, estado do Pará, Brasil. E também discutir o seu potencial zoonótico para o homem. As amostras consistiram em 30 espécimes de Cairina moschata domestica analisados. Um total de 258 nematódeos foram recuperados, fortemente fixados na mucosa esofágica dos hospedeiros. As características morfológicas e morfométricas foram compatíveis com as larvas de terceiro estágio de Anisakis.

The potential for dispersal of microalgal resting cysts by migratory birds.

Most microalgal species are geographically widespread, but little is known about how they are dispersed. One potential mechanism for long-distance dispersal is through birds, which may transport cells internally (endozoochory) and deposit them during, or in-between, their migratory stopovers. We hypothesize that dinoflagellates, in particular resting stages, can tolerate bird digestion; that bird temperature, acidity, and retention time negatively affect dinoflagellate viability; and that recovered cysts can germinate after passage through the birds' gut, contributing to species-specific dispersal of the dinoflagellates across scales. Tolerance of two dinoflagellate species (Peridiniopsis borgei, a warm-water species and Apocalathium malmogiense, a cold-water species) to Mallard gut passage was investigated using in vitro experiments simulating the gizzard and caeca conditions. The effect of in vitro digestion and retention time on cell integrity, cell viability, and germination capacity of the dinoflagellate species was examined targeting both their vegetative and resting stages. Resting stages (cysts) of both species were able to survive simulated bird gut passage, even if their survival rate and germination were negatively affected by exposure to acidic condition and bird internal temperature. Cysts of A. malmogiense were more sensitive than P. borgei to treatments and to the presence of digestive enzymes. Vegetative cells did not survive conditions of bird internal temperature and formed pellicle cysts when exposed to gizzard-like acid conditions. We show that dinoflagellate resting cysts serve as dispersal propagules through migratory birds. Assuming a retention time of viable cysts of 2-12 h to duck stomach conditions, cysts could be dispersed 150-800 km and beyond.

Neospora caninum in Wild Waterfowl: Occurrence of Parasite DNA and Low Antibody Titers.

Thirty-five adult waterfowl (14 males and 21 females) representing various orders and species were sampled during the hunting season from 2015 to 2016. Antibodies to Neospora caninum were detected by IFAT on blood samples, while heart and brain were subjected to molecular analysis for the detection of Neospora caninum DNA. Twelve birds (34.3%) (6 Anas crecca , 3 Anas platyrhynchos , 2 Anas penelope , 1 Anas acuta ) showed antibodies versus N. caninum , while 10 animals out of 35 (4 A. crecca , 2 A. platyrhynchos , 2 A. penelope , 1 A. acuta , and 1 Vanellus vanellus ) scored positive for at least 1 DNA sample, with an overall prevalence of 28.6%. The present report shows for the first time the occurrence of antibodies and N. caninum DNA in waterfowl. The avian species investigated in the present report, which feed directly from the soil and/or water, would be able to ingest oocysts excreted by final canid hosts and could contribute to parasite transmission in the sylvatic cycle. To achieve a definitive result about the role of these avian species in the epidemiology of this protozoan, the presence of viable parasites should be demonstrated by bioassay and/or culture, as well as histological evidence of N. caninum cysts in avian tissues.

Trichodinosis associated with pathology of the reproductive tract in waterfowl.

Trichodinid ciliophorans are opportunistic parasites of many species of fish, amphibians, and molluscs, but yet never reported in association with lesions in birds. Postmortem and histopathological evaluation of a commercial adult Toulouse gander and female goose, and a wild Mallard drake revealed the presence of severe pathological parasitic colonization of their reproductive tracts. Histopathological findings included moderate to severe granulocytic inflammation, acanthosis, accentuation of the rete pegs, and proliferative hyperplastic squamous metaplasia of the mucosa of the ejaculatory ducts and groove, sulcus spermaticus, glandular part of the phallus (cavum penis), and oviduct in association with large numbers of ciliated protozoa anchored to the tissues or free in the lumen. These protozoa had characteristic morphological features analogous to the family of Trichodinidae. The source of this parasitism could not be determined. To our knowledge, this is the first report of trichodinosis associated with pathology in birds.

Identification and intraspecific genetic diversity of Sarcocystis rileyi from ducks, Anas spp., in Lithuania and Finland.

Macroscopic Sarcocystis cysts were detected in the muscles of 28 Mallards ( Anas platyrhynchos ), 1 Eurasian Wigeon ( Anas penelope ), and 1 Common Teal ( Anas crecca ) hunted in Lithuania and Finland. According to the sequences of the 18S rRNA gene, 28S rRNA gene, and ITS-1 region, the macrocysts examined from all 30 ducks belonged to Sarcocystis rileyi. This parasite was found in the Eurasian Wigeon and the Common Teal for the first time. All S. rileyi isolates examined were identical to each other and differed from 2 S. rileyi isolates previously reported from 2 Mallards from the United States only by 1 nucleotide substitution within the ITS-1 region.

Infections with Sarcocystis wenzeli are prevalent in the chickens of Yunnan Province, China, but not in the flocks of domesticated pigeons or ducks.

The distribution and prevalence of infections with species of Sarcocystis in domestic fowl in Asia are poorly known. Here, ducks, pigeons, and chickens from Yunnan Province, China were examined for evidence of parasitic infection with Sarcocystis spp. One hundred and ninety one chickens, 514 ducks, and nine pigeons were investigated. Whereas the ducks and pigeons lacked tissue cysts in their muscle, brain or peripheral nervous system, cysts of Sarcocystis wenzeli were identified in 17 of 191 chickens (8.9%). Morphologically, the cysts were thread-like, ranging in size from 334-3169 × 41-117 µm (mean 1093 × 65 µm). Cysts were septate with dense, short finger-like protrusions which appeared radially striated. The cyst wall was 1.4-3.5 µm (mean 2.4 µm) thick. The bradyzoites were lancet shaped and measured 12.2-17.7 × 1.8-2.9 µm (mean 14.6 × 2.5 µm). Ultrastucturally, the primary sarcocyst wall had stubby villar protrusions, corresponding to the 'type 9' class previously designated. The protrusions measured 0.87-1.89 × 0.47-0.91 µm (mean 1.27 × 0.59 µm; n = 57). These findings confirm previous work from the vicinity of Kunming concerning the occurrence of S. wenzeli in chickens, and its use of both cats and dogs as definitive hosts, but indicate that corresponding infections may not occur in the regional domestic flocks of other types of fowl.

Identification of Sarcocystis rileyi from the mallard duck (Anas platyrhynchos) in Europe: cyst morphology and results of DNA analysis.

Macroscopic cysts of Sarcocystis in ducks were recorded in Europe, but they were not investigated in more detail. Results of light and electron microscopy as well as 18S rDNA, 28S rDNA and ITS-1 region sequences of Sarcocystis macrocysts isolated from naturally infected mallard duck (Anas platyrhynchos) from Lithuania are presented in this paper. According to ultrastructure results, macrocysts examined corresponds to S. rileyi. Phylogenetic investigation showed S. rileyi to be the most closely related to two unnamed Sarcocystis species from anseriforms and to the S. mucosa. This is the first well-documented case of S. rileyi in Europe.

The role of aquatic birds in the environmental dissemination of human pathogenic Giardia duodenalis cysts and Cryptosporidium oocysts in Hungary.

Fecal samples were taken from 132 (103 wild and 29 domestic) aquatic birds on selected areas in Hungary from February 2008 to March 2008. Cryptosporidium oocysts and Giardia cysts were purified from the samples and were viewed via fluorescent antibody staining. Molecular detection tools, such as PCR-sequencing and Loop mediated isothermal amplification (LAMP) were used in order to determine the Cryptosporidium species and Giardia duodenalis assemblages present. All together 6 (5.8%) and 6 (5.8%) samples out of the 103 wild bird samples and 4 (13%) and 7 (24%) samples out of the 29 domestic bird samples have been found to be Cryptosporidium and G. duodenalis positive respectively. The results of this study indicate that aquatic ducks, geese, coot and cormorant can play role in the environmental dissemination of human pathogenic Giardia cysts and Cryptosporidium oocysts in Hungary. To our knowledge, this is the first description of Cryptosporidium sp. in Anser fabalis and Anser anser, furthermore Giardia sp. in Fulica atra, A. fabalis and P. carbo and the first PCR-sequence confirmed detection of C. parvum in A. platyrhynchos and F. atra, G. duodenalis Assemblage A in A. strepera and G. duodenalis Assemblage B in A. anser.

Prevalência de helmintos em patos domésticos Cairina moschatadom. (Linné) (Anseriformes, Anatidae, Cairinini, Cairina) provenientesde criações extensivas no estado do Rio de Janeiro, Brasil / Prevalence of helmintos in domestic ducks Cairina moschata dom. (Linné)

De março a agosto de 2002 foi realizado um levantamento de parasitos em trinta patos domésticos criados extensivamenteoriundos de seis municípios do estado do Rio de Janeiro, através de exames clínicos, necropsias e amostras de tecidosafetados. Dezessete aves estavam parasitadas por oito diferentes espécies de helmintos. A prevalência e a intensidade médiade infecção entre as aves parasitadas foram registradas. O presente trabalho registra, pela primeira vez no Brasil, nematóides da espécie Capillaria phasianina nestes hospedeiros.

From March to August 2002 a survey concerning the parasites of the muscovy ducks ( Cairina moschata dom.) was carried out.These waterfowls were originated from six counties of Rio de Janeiro state and were bred in free-range system. This researchwas based in clinic examination, necropsies and tissue samples collection for histopathology of 30 waterfowls. Birds wereclassified in to two-aged groups: young ones (3 – 5 months, n = 10) and adult ones (5,5 – 36 months, n = 20). Seventeen ducks.

Terminal phase of bird schistosomiasis caused by Trichobilharzia regenti (Schistosomatidae) in ducks (Anas platyrhynchos f. domestica).

The terminal phase of the migration of Trichobilharzia regenti Horák, Kolárová et Dvorák, 1998 in the definitive host (Anas platyrhynchos f. domestica) was studied 12-27 days post infection (p.i.). Brain meninges were the last part of the nervous system where the worms were detected before their occurrence in the nasal cavity. In meninges, the parasites started to feed on red blood cells. Then the worms occurred in the nasal mucosa 14-25 days p.i. and the first immature eggs appeared 15 days p.i. The fully developed miracidia were recorded in the eggs from 17 days p.i. and freely in the nasal mucosa 19 days p.i. Infiltrates of lymphocytes, later also eosinophils and heterophils around the eggs and free miracidia, were observed from 15 and 19 days p.i., respectively. The haemorrhages occurring from 17 days p.i., and the granulomas with lymphocytes, eosinophils and heterophils forming around the eggs from 22 days p.i. were the most apparent pathological changes of nasal tissue.

Endemic echinostome infections of candidate hosts.

Wild Lymnaea tomentosa snails, recovered from Lake Wanaka, New Zealand, were established in the laboratory. Wild snails, naturally infected with echinostomes, provided metacercariae for infection of laboratory maintained snails. Metacercarial cysts from wild and laboratory snails were then used to attempt infection of definitive host candidates. Laboratory snails provided convenient packaging of known numbers of cysts. Metacercariae excysted in the small intestines of ducklings to mature in 6 days. Worms were expelled as they became gravid. Attempts to establish infections in experimental hosts other than ducklings were not successful. No worms were recovered from mice, white rats, guinea pigs, hamsters or immunosuppressed white rats.

Trichobilharzia regenti: the developmental differences in natural and abnormal hosts.

Trichobilharzia regenti is a bird nasal parasite causing human cercarial dermatitis. Schistosomula are able to migrate via the bird nervous system and then, they mature and lay eggs in the nasal cavity. To some extent they can also migrate and develop in mammals. The present study has shown the developmental differences of T. regenti in the natural (ducks) and the abnormal (mice; inbred strains BALB/c, SCID) hosts. The study describes the following parameters of developing worms: length and width of the body, length and content of the intestine, development of the reproductive organs and characterization of surface and intestinal epithelium by lectin probes. The differences in length and width of schistosomula localized in the spinal cord of various hosts cannot be simply explained and may depend on yet unknown host factors. Moreover, there must be several physiological changes during the migration through the skin, the nervous tissue and the nasal cavity, enabling uptake and digestion of different host components. For example the intestine of schistosomula was mostly filled with light-brown pigmented granules until 6 days p.i. (probably of nervous tissue origin) while the older schistosomula and adult intestine was mostly full of dark-brown pigment (probably of blood origin). Reproductive organs were observed from day 9 p.i. in worms from ducks. Whereas ConA and PSA specifically bound to the surface and intestinal epithelium of schistosomula and adults, only the labelled UEA-I lectin could be used as a surface marker of cercaria-schistosomulum transformation. The results confirmed retarded development of parasites in abnormal hosts; the factor responsible for this phenomenon should be clarified in the future.

Mortality in Laysan ducks (Anas laysanensis) by emaciation complicated by Echinuria uncinata on Laysan Island, Hawaii, 1993.

In November 1993, unusual mortality occurred among endangered Laysan ducks on Laysan Island, one of the remote refugia of the Northwestern Hawaiian Islands National Wildlife Refuge (USA). Ten live ducks were emaciated, and blood samples documented anemia, heterophilia, and eosinophilia. Pathology in 13 duck carcasses revealed emaciation, marked thickening of the proventricular wall, abundant mucus, and nodules in the gastrointestinal tract. Histology revealed granulomata associated with nematodes in the proventriculus, small intestines, and body walls of nine of 10 ducks examined on histology. We suspect that low rainfall and low food abundance that year contributed to enhanced pathogenicity of parasite infection, either through increased exposure or decreased host resistance. Because the Laysan duck is found only on Laysan island and is critically endangered, translocation of this species to other islands is being considered. Given that we have not seen pathology associated with Echinuria spp. in native waterfowl on other Hawaiian Islands and given the parasite's potential to cause significant lesions in Laysan ducks, it will be important to prevent the translocation of Echinuria spp.

Redescription of the sarcocysts of Sarcocystis rileyi (Apicomplexa: Sarcocystidae).

The intermediate hosts for Sarcocystis rileyi (Stiles 1893) Minchin 1913 are ducks (Anas spp.), and the striped skunk (Mephitis mephitis) is its definitive host. The structure of sarcocysts from an experimentally infected shoveler duck (Anas cylpeata) fed sporocysts from an experimentally-infected M. mephitis was studied and compared with type specimens from a naturally infected duck. The experimentally infected duck was killed 154 d after feeding sporocysts. By light microscopy the sarcocyst wall was 3-5 microm thick with indistinct villar protrusions. Ultrastructurally, the sarcocyst wall was a type-23 cyst wall with anastomosing villar protrusions that were up to 7.5 microm long. The villar projections contained filamentous structures. The bradyzoites were 12-14 microm long. Structurally, the sarcocyst from the naturally infected and experimentally infected ducks appeared similar.

[Visceral lesions in mammals and birds exposed to agents of human cercarial dermatitis]. / Lésions viscérales de mammifères et oiseaux, exposés aux agents de dermatite cercarienne humaine.

Over the past few years, the cercarial dermatitis has become a new problem of public health, obviously linked to the prolonged stay of migrant birds on our territory. This is a skin affection characterized by pruriginous and papulous eruptions caused by penetration of avian bilharzian larvae under the skin. These larvae are emitted by molluscs, mostly limneids. In aquatic birds, especially in migrating Anatidae, these larvae reach the visceral vessels, become adults in a few weeks, lay eggs, then degenerate. Corresponding miracidia contaminate new limneids. Since 1993, the total number of annual cases of cercarial dermatitis has increased from only ten to thousands in France and the affection rages in pools where limneids, migrating water birds and swimmers gather together. Fever, respiratory and/or digestive allergic symptoms appear in some cases. This clinical pattern has encouraged to undertake research on the future of these bilharzian larvae in mammals organism. A preliminary investigation on a rodent model showed that, once the skin barrier had been crossed, the schistosomulae migrated into the lungs of the host; there they survived a week and induced lesions. The goal of this study is to carry on the research, over a longer period, after exposure to cercariae, simultaneously in mammals and birds, with two species of bilharziae present in France. The selected models are the gerbil Meriones unguiculatus for mammals, and the ducks Anas platyrhynchos and Cairina moschata, for birds. 5 M. unguiculatus and 2 A. platyrhynchos were exposed to cercariae emitted by Radix auricularia; 2 gerbils and 5 A. platyryhnchos to larvae of R. peregra, 3 C. moschata to larvae emitted by two species of molluscs: 70-230 from R. auricularia and 330-585 from R. peregra. 5 gerbils died between 2 and 5 weeks after exposure, 2 gerbils sacrificed early, served as control animals for skin manifestations. Eight ducks were sacrificed between 2 and 4 weeks after; the 2 last ones, exposed several times, were sacrificed respectively 7 and 13 weeks after the first exposure. Visceral and skin samples were submitted to histological study. The control gerbils developed skin dermatitis. In ducks, R. auricularia was the vector of Trichobilharzia franki, whose selective dwelling site was the mesentery; R. peregra was the vector of an indeterminate species found in the lungs and nose. This species is called Bilharzia sp. in this study. The ducks, exposed to two kinds of larvae, displayed worms in these two main locations. In gerbils, T. franki induced lesions in the mesenteric veins and the peritoneum. Bilharzia sp. gave rise to lesions in lung arteries, pleura and liver veins. Vascular changes encompassed endothelitis and lymphocytic vasculitis, while serosa displayed mesothelial hyperplasia. The types of lesions observed in gerbils were noticed in ducks, and, according to the species of bilharzia, in the homologous viscera. Additional foreign body granulomas centred on worm's debris or their eggs, and vascular thromboses were present, too. In addition, ducks displayed lesions involving several other viscera including the intestine, the kidneys and the peripheral nerves. These changes were multiple and diffuse in C. moschata exposed to two species of bilharziae. They were observed mainly in mesenteric and intestinal vessels, pulmonary arteries and hepatic veins. In gerbils, the lesions persisted 2 to 5 weeks after exposure, but worms were not identified in the neighbouring tissues near the damaged vessels. In ducks, lesions were important between 2 and 7 weeks after exposure; they co-existed with live or dead worms, sometimes paired, with or without eggs. The hepatic lesions regressed 13 weeks, after exposure. In mammals and birds, young worms could migrate into the same visceral vessels, and stimulating formation of persistent lesions. In individuals exposed to the same cercariae, development of similar lesions would be probable.