Histology, histochemistry and fine structure of the lacrimal gland in the one-humped camel (Camelus dromedarius).

Our research aimed to provide complete histological, histochemical and ultrastructural features of the lacrimal gland of the one-humped camel (Camelus dromedarius) as well as novel insights into its adaptability to the Egyptian desert. Our study was applied to 20 fresh lacrimal glands collected from 10 camels instantly after their slaughtering. The results revealed that the gland was a compound tubulo-acinar gland, and its acini were enclosed by a thick connective tissue capsule that was very rich in elastic and collagen fibres. The gland acini had irregular lumens and were composed of conical to pyramidal cells. The nuclei of secretory cells were found in the basal part, and the cytoplasm was eosinophilic and granular. The glandular tissue consisted of serous and mucous acini and seromucous secretory cells. Histochemically, there was a significant amount of neutral mucopolysaccharides in the acini in which mucous cells had a significant periodic acid-Schiff (PAS)-positive reaction, whereas seromucous cells had a mild PAS-positive reaction. Ultrastructurally, the lacrimal cells had numerous secretory vesicles with contents of moderately to highly electron-dense cytoplasm. The nuclear envelope consisted of two prominent membranes surrounding the peri-nuclear cisterna. The acinar cells had numerous electron-lucent and moderately electron-dense secretory granules, mainly situated on the apical surface, and secreted their contents into the lumen. The luminal surface of the mucous secretory cells represents the remains of secretory granules discharged by the merocrine mechanism. In conclusion, the mucous secretion is believed to aid in the washing and moistening of the eyeball, particularly in dry, hot and dusty environments.

Parotid salivary mucocele in a companion rabbit (Oryctolagus cuniculus): a report on the clinical and laboratory characteristics and surgical treatment - case report / [Mucocele salivar parotídea em coelho doméstico (Oryctolagus cuniculus): relato de características clínico-laboratoriais e tratamento cirúrgico - relato de caso]

The present report aimed to describe the main characteristics of the parotid salivary mucocele in an adult male rabbit, which presented with a painless fluctuating mass with fluid content. Owing to the need for repeated fluid drainage, surgical excision was the chosen mode of treatment. Preoperative evaluation included radiography and blood analysis. The patient underwent surgical excision of the affected gland. Inhalation anesthesia was maintained by means of isoflurane and the cardio-respiratory parameters were monitored throughout the surgery. A bipolar electrocautery was used to assist in the incision and polyglactin 910 and nylon were the suture materials used in the wound closure technique. Post-operative medications included analgesics, anti-inflammatory agents and antibiotics. Histopathology of the excised glandular tissue revealed a mixed inflammatory infiltrate, fibroblasts, hemorrhage and hyperemia. The observations in this case suggest that surgical excision of the affected gland is the treatment of choice for the management of mucocele in companion rabbits, which has already been identified for other animals. Periodic acid-reactive Schiff staining confirmed the diagnosis of salivary mucocele. The complementary investigations helped to rule out the differential diagnosis and indicated a favorable prognosis, in view of the fact that the case was successfully resolved without complications or recurrence.(AU)

O presente relato teve como objetivo descrever as principais características da mucocele salivar parotídea em um coelho macho adulto, que apresentou uma massa flutuante indolor e com um conteúdo líquido em seu interior. Devido à necessidade de repetidas punções deste fluido, optou-se pela excisão cirúrgica como forma de tratamento. A avaliação pré-operatória incluiu radiografias e análises sanguíneas. O paciente foi submetido ao tratamento cirúrgico com excisão da glândula afetada. A anestesia inalatória foi mantida com isoflurano e os parâmetros cardio-respiratórios foram monitorados durante a cirurgia. Um eletrocautério bipolar foi utilizado para auxiliar na incisão e os fios poliglactina 910 e nylon foram utilizados na técnica de sutura. As medicações pós-operatórias incluíram agentes analgésicos, anti-inflamatórios e antibióticos. A histopatologia do tecido glandular removido revelou infiltrado inflamatório misto, fibroblastos, hemorragia e hiperemia. As observações neste caso sugerem que a remoção cirúrgica da glândula afetada seja o tratamento de escolha no manejo da mucocele em coelhos de companhia, o que já vem sendo identificado para outros animais. A coloração do ácido periódico reativo de Schiff confirmou o diagnóstico da mucocele salivar. Os exames complementares ajudaram a excluir as doenças que fazem parte do diagnóstico diferencial e indicaram um prognóstico favorável, tendo em vista o fato que este caso foi resolvido com sucesso, sem complicações ou recorrência.(AU)

Morphological characterization of the adherence and invasion of Streptococcus agalactiae to the intestinal mucosa of tilapia Oreochromis sp.: An in vitro model.

Streptococcosis in tilapia Oreochromis sp. is possibly the most important bacterial disease for fish production worldwide. In Colombia, streptococcosis is caused by Streptococcus agalactiae (GBS), but in other countries, Streptococcus iniae is also involved. Prevention of streptococcosis is required and must be addressed for economic, social, international trade and public health reasons. This research used an in vitro culture of tilapia intestine to detail the intestinal mucosal response once the pathogen contacts the epithelium. We show that S. agalactiae sheds off its capsule to adhere to the epithelium. The bacterium adheres as a single individuum, in groups or in chains and is able to divide on the apical border of enterocytes. GBS adheres at and invades exclusively through the apical portion of the intestinal folds, using the transepithelial route. Once within the cytoplasm of enterocytes, the bacteria continue to divide. On the basolateral side of the epithelium, the microorganisms leave the cells to reach the propria and travel through the microcirculation. No evidence of an immuno-inflammatory reaction or goblet cell response in the epithelium or the lamina propria was seen during the process of adherence and invasion of the pathogen.

Comparison of goblet cell staining methods in jejunal mucosa of turkey poults.

This study compared the intestinal goblet cell density of turkey poults at 2 different ages using Alcian blue-periodic acid-Shiff (AB-PAS) and mucicarmine stains. Neutral mucins are stained with periodic acid-Shiff whereas acidic mucins are stained with Alcian blue. Mucicarmine and AB-PAS are specific to the mucins of epithelial origin. Mucicarmine has only been used for the assessment of goblet cells in human specimens, and it may have advantages for use in animals as a result of the methodological simplicity of staining as compared to AB-PAS. A mid-section of jejunum was taken from 80 turkey poults at 21 and 28 d, and fixed in 10% buffered formalin for 48 h. Each fixed tissue was dehydrated with ethanol, cleared with Sub-X, placed in paraffin wax, prepared on 2 slides, cleared and hydrated. The 2 slides were randomly assigned to 2 treatments which consisted of AB-PAS and mucicarmine stains in a completely randomized design. Goblet cell counts were taken from four villi per slide and the villus height was measured and averaged. There was no difference in the goblet cell density between the staining methods AB-PAS and mucicarmine at 21 or 28 d posthatch. These results show that both staining methods are viable for assessment of goblet cell density in turkey poults.

Oral fibrosarcoma in jararaca (Bothrops pubescens): anatomopathological and immunohistochemical aspects / Fibrossarcoma oral em jararaca (Bothrops pubescens): aspectos anatomopatológicos e imuno-histoquímicos

A 4-year-old female captive-bred snake of the genus Bothrops showed swelling on the left side of the oral cavity, suggesting the development of neoplasia. The mass was removed surgically and sent for pathological examination. Two months later a new increase in volume in the same site was observed, suggesting recurrence. The lesion was completely removed and sent for pathological analysis. Histologically, the two-samples consisted of a mass with highly-cell density composed of spindle-shaped anaplastic cells arranged in interwoven bundles, distributed throughout the tissue extension and, occasionally, polygonal cells arranged in irregular fascicles. The Masson trichrome staining showed modest amount of collagen supporting the neoplastic cells. PAS-positive content was not observed in the cytoplasm of neoplastic cells. Histological and histochemical findings indicated that it was a spindle cell neoplasm, but the classification was not possible. Immunohistochemistry was requested and performed using the streptavidin-biotin-peroxidase method. The markers used were anti-vimentin, anti-PCNA, anti-EMA, anti-melan A and anti-melanosome, anti-desmin, anti-actin, anti-CD68 and anti- S100protein. The neoplastic cells were immunoreactive for vimentin and PCNA and negative for the other antibodies. The morphology characterization, histochemical and immunohistochemical analysis of neoplastic cells allowed the definitive diagnosis of oral fibrosarcoma...

Uma serpente de cativeiro, fêmea, quatro anos de idade, do gênero Bothrops apresentou aumento de volume no lado esquerdo da cavidade oral, sugerindo tratar-se de neoplasma. A massa foi removida cirurgicamente e enviada para exame anatomopatológico. Dois meses depois foi observado novo aumento de volume no mesmo local, sugerindo recidiva. A lesão foi removida por completo e também enviada para análise. Histologicamente, as duas amostras consistiam de massa altamente celular, composta por células anaplásicas fusiformes organizadas em feixes entrelaçados e distribuídos por toda extensão tecidual e, ocasionalmente, células poligonais arranjadas em fascículos irregulares. A coloração de tricrômico de Masson apresentou quantidade modesta de colágeno sustentando as células neoplásicas. Não foi observado conteúdo PAS-positivo no citoplasma das células neoplásicas. Os achados histológicos e histoquímicos indicavam tratar-se de neoplasma de células fusiformes, porém não era possível sua classificação. A imuno-histoquímica foi requisitada e realizada pelo método streptavidina-biotina-peroxidase, utilizando os anticorpos anti-vimentina, anti-PCNA, Anti-EMA, anti-melan A, anti-HMB45, anti-desmina, anti-actina, anti-CD68 e anti-proteína S-100. As células neoplásicas foram imunorreativas para vimentina e PCNA e, negativas para os demais anticorpos. A caracterização morfológica, histoquímica e imuno-histoquímica das células neoplásicas permitiu o diagnóstico definitivo de fibrossarcoma oral...

Investigations on the endometrial response to intrauterine administration of N-acetylcysteine in oestrous mares.

In mares, mating-induced persistent endometritis contributes to low fertility. The condition is in part related to delayed clearance of mucus accumulated within the uterine lumen. The objective of this study was to investigate the endometrial response of healthy mares to intrauterine (i.u.) treatment with N-acetylcysteine (NAC). Oestrous mares (n = 12) were randomly assigned to a treatment (TM) or control (C) group and received an i.u. infusion of 5% NAC and saline (total volume 140 ml), respectively. Endometrial biopsies were collected in five of the mares 24 h after treatment, in the remaining seven mares 72 h after treatment. Endometrial biopsies were evaluated for integrity of the luminal epithelium, number of polymorphonuclear neutrophils (PMN), staining for cyclooxygenase 2 (COX2), staining with Kiel 67 antigen (Ki-67), lectins and periodic acid-Schiff (PAS). The integrity of endometrial epithelial cells was not affected by treatment (no statistical differences between groups or times). At 24 h after treatment, the mean number of PMN in endometrial biopsies from NAC- and C-mares did not differ, but at 72 h after treatment, number of PMN was significantly higher (p < 0.05) in C (3.9 ± 0.6 PMN/field) compared with NAC-treated mares (2.3 ± 0.2 PMN/field). At 72 h after treatment, the intensity of staining for COX2 was significantly higher after saline than after NAC treatment (p < 0.05). In the epithelium, no differences in staining for the proliferation marker Ki-67 were seen with respect to time and treatment. Score for the lectin wheat germ agglutinin (WGA) was slightly higher in NAC-treated mares than in C-mares 72 h after treatment (p < 0.05). Score for PAS staining of mucus in deep uterine glands differed significantly between groups at 24 h after treatment (p < 0.05). The present study demonstrates that NAC does not adversely affect the endometrial function. Moreover, an anti-inflammatory effect on the equine endometrium was observed.

Complex polysaccharide inclusions in the skeletal muscle of stranded cetaceans.

Skeletal muscle samples were examined post-mortem in 148 cetaceans over a 12-year period. Histological analysis included haematoxylin and eosin (HE) and periodic acid-Schiff (PAS) staining with and without diastase digestion. In addition, histological muscle sections were immunostained for ubiquitin and fast and slow heavy-chain myosin isoforms. PAS-positive, diastase-resistant inclusions were detected in 26 animals from 11 different species. Older cetaceans were preferentially affected. These intrafibre inclusions varied from large aggregates to multiple coarse granules and were typically associated with type II fibres. All diastase-resistant inclusions were positive for ubiquitin. These features resembled those inclusions described as complex polysaccharide in horses. Based on these histological findings and the ubiquitin staining pattern, a morphological diagnosis of complex polysaccharide storage myopathy is proposed.

Infection with the gastrointestinal nematode Ostertagia ostertagi in cattle affects mucus biosynthesis in the abomasum.

The mucus layer in the gastrointestinal (GI) tract is considered to be the first line of defense to the external environment. Alteration in mucus components has been reported to occur during intestinal nematode infection in ruminants, but the role of mucus in response to abomasal parasites remains largely unclear. The aim of the current study was to analyze the effects of an Ostertagia ostertagi infection on the abomasal mucus biosynthesis in cattle. Increased gene expression of MUC1, MUC6 and MUC20 was observed, while MUC5AC did not change during infection. Qualitative changes of mucins, related to sugar composition, were also observed. AB-PAS and HID-AB stainings highlighted a decrease in neutral and an increase in acidic mucins, throughout the infection. Several genes involved in mucin core structure synthesis, branching and oligomerization, such as GCNT3, GCNT4, A4GNT and protein disulphide isomerases were found to be upregulated. Increase in mucin fucosylation was observed using the lectin UEA-I and through the evaluation of fucosyltransferases gene expression levels. Finally, transcription levels of 2 trefoil factors, TFF1 and TFF3, which are co-expressed with mucins in the GI tract, were also found to be significantly upregulated in infected animals. Although the alterations in mucus biosynthesis started early during infection, the biggest effects were found when adult worms were present on the surface of the abomasal mucosa and are likely caused by the alterations in mucosal cell populations, characterized by hyperplasia of mucus secreting cells.

Evaluation of immunohistochemistry for the diagnosis of sporotrichosis in dogs.

The aim of this study was to apply immunohistochemistry (IHC) for the diagnosis of canine sporotrichosis and to compare this method with the Grocott's silver stain (GSS) and periodic acid Schiff (PAS) techniques. Eighty-seven dogs with sporotrichosis (group 1) and 35 with American tegumentary leishmaniosis (ATL) (group 2) were studied. The fungus was detected in group 1 by GSS, PAS and IHC. IHC was also applied to group 2 to evaluate the occurrence of cross-reactions. PAS, GSS and IHC detected yeast cells in 19.5%, 43.7% and 65.5% of the group 1 cases, respectively. The detection of intracellular antigens of Sporothrix schenckii by IHC increased the sensitivity of the histological diagnosis to 80.5%. No positive reaction was observed in ATL lesions. The results suggest that IHC may be indicated for the diagnosis of sporotrichosis because of its higher diagnostic sensitivity.

Histochemical characterisation of complex carbohydrates expressed in the alimentary tract of chickens.

This study characterised the composition of surface and secretion complex carbohydrates in the alimentary tract of organically and intensively housed chickens. Histochemical labelling was carried out on samples of oesophagus, glandular stomach and proximal duodenum using (1) alcian blue (AB) at pH 2.5 combined with neuraminidase digestion (Sial) with or without saponification (KOH), (2) AB at pH 1 and 0.5, (3) periodic acid-Schiff (PAS), (4) a combined AB-PAS stain, and (5) both low and high iron diamine stains combined with enzymatic treatments specific for glycosaminoglycans. Semi-quantitative scoring of the histochemical staining indicated abundant acidic sulfated glycoconjugates in each alimentary tract region, in addition to the presence of sialoglycoderivatives in the oesophagus. These complex carbohydrate components are likely to have various functions including the provision of a protective visco-elastic barrier and a role in the defence against specific pathogens. The findings provide a starting point for a more in-depth study of alimentary tract glycoconjugates in poultry.

Histology and mucin histochemistry of the digestive tract of yellow catfish, Pelteobagrus fulvidraco.

The histology and characteristics of mucins secreted by epithelial mucous cells of the digestive tract in yellow catfish, Pelteobagrus fulvidraco were investigated using light microscope and transmission electron microscope. The digestive tract was divided into a pharynx, oesophagus, U-shaped stomach (with a cardiac, fundic and pyloric part) and intestine, composed of anterior intestine, middle intestine and posterior intestine, which consisted of a mucosa (epithelial layer), lamina propria-submucosa, muscularis and serosa. A large number of isolated longitudinal striated muscular bundles were present in the lamina propria-submucosa of pharynx. Goblet cells were observed throughout the digestive tract, except in the stomach. In the cardiac and fundic stomach, a plenty of gastric glands were observed, whereas they were absent in the pyloric part. Numerous mitochondria and endoplasmic reticulum were observed in the columnar epithelial cells of the intestine, especially of the anterior part. The epithelial mucous cells contained neutral or other two mixtures of acid and neutral mucins, the first being the most common. The neutral mucin was the only type of mucins in the stomach, anterior intestine and middle intestine. The results of this study will be helpful for understanding the digestive physiology and diagnosing some gastrointestinal diseases in yellow catfish.

Cytochemical characterisation of the leucocytes and thrombocytes from Murray cod (Maccullochella peelii peelii, Mitchell).

Cytochemistry has proven effective in differentiating specific cell lineages and elucidating their functional properties. This study utilised a range of cytochemical techniques to further investigate the leucocyte populations from Murray cod, an iconic Australian teleost fish species. This analysis provided clear insight into the structure and function of the leucocytes from this fish, which were found to be broadly similar to those of other fish species. However, some important differences were identified in Murray cod, such as the presence of naphthol AS chloroacetate esterase activity in the heterophil population, positive staining for periodic acid Schiff's, alkaline phosphatase and Sudan black B in the lymphocyte population, and a prevalent population of myeloid precursor cells.

A case of pulmonary cryptococcosis in a free-living toad (Bufo bufo).

Pulmonary cryptococcosis was observed in a free-living adult female common toad (Bufo bufo) that was killed by a vehicle. Both lungs had various eosinophilic, monomorphic, and spherical to elliptical organisms identified as Cryptoccocus spp. The yeasts were demonstrated by Grocott's silver method and the periodic acid-Schiff reaction and the capsule was positive for mucin with a mucicarmine stain. The agent was confirmed by immunohistochemistry, using the monoclonal antibody anti-Cryptococcus neoformans, and by a polymerase chain reaction-based method using a C. neoformans-specific primer. This report, to the best of our knowledge, represents the first case of cryptococcosis in a common toad.

Cervical chondroid chordoma in a Shetland sheep dog.

A spayed female Shetland sheep dog aged 12 years was presented for examination with ataxia and hindlimb paralysis. Extradural spinal cord compression was found at the level of vertebrae C6-C7 by radiography and myelocomputed tomography. A jelly-like mass (0.6 x 1.3 cm) was removed surgically. Histopathological findings were characterized by proliferation of vacuolated polygonal cells (physaliphorous cells) in a mucinous matrix and the presence of chondroid tissue shown immunohistochemically to express S-100. The physaliphorous cells were immunolabelled strongly for vimentin and S-100, and weakly for cytokeratin. A diagnosis of canine cervical chondroid chordoma was made. This is considered to be the first report of a chondroid chordoma originating from the cervical region of the spine in the dog.

Tonsillar lymphangiomatous polyp in an adult dog.

A female spayed cocker spaniel dog, aged 8 years, developed a large, smooth pedunculated mass arising from the right palatine tonsil. Histology revealed that the mass was composed of many, variably dilated, thin-walled lymphatic channels filled with pale eosinophilic fluid lacking red blood cells and embedded in a dense, fibrovascular stroma. The dilated lymphatic channels were lined by a single layer of flattened, discontinuous endothelium with scattered intraluminal valves. Periodic acid-Schiff staining highlighted the discontinuous basement membrane and immunohistochemistry revealed strong cell membrane and cytoplasmic immunoreactivity for CD31 and von Willebrand factor, respectively. The clinical and histological findings were consistent with a tonsillar lymphangiomatous polyp - an uncommon, benign tumour of the tonsil in man that has previously been unrecognized in veterinary medicine.

A histological study of the seminal vesicle of the armoured catfish Corydoras aeneus.

Most species of Corydoras exhibited a reproductive behaviour called 'T-position', and exhibited an accessory gland in the male genital tract, called the seminal vesicle. It appeared that both the structure and the composition of the fluid varied considerably between the species investigated. Consequently, different opinions were proposed regarding the possible role of seminal vesicle on this particular reproductive behaviour. Male adults of Corydoras aeneus were collected, anaesthetized, and samples of seminal vesicle were fixed in Bouin's solution. The sections were stained with haematoxylin-eosin and periodic acid Schiff. The seminal vesicle showed a system of anastomosed secretory tubules, forming a vesicular collective network, which gave rise to the vesicular ducts. The latter fused with the testicular efferent ducts and formed the spermatic ducts. Considering this fusion, when the sperm cells reached the spermatic ducts, the fluid produced at the seminal vesicle covered them. Histochemical studies evidenced the presence of neutral and acid glycosaminoglycans in the seminal fluid. Considering the reproductive behaviour of C. aeneus, it is believed that the protection associated with the immobilization of the sperm cells assures the sperm integrity during the passage through female's intestine until fertilization.

Spontaneous subcutaneous myxosarcoma in a captive European hedgehog (Erinsceus europaeus).

A surgically excised biopsy representing a subcutaneous mass on the left side of the neck from a 3-year-old female European hedgehog (Erinsceus europaeus) was presented. Spontaneous myxosarcoma was diagnosed based on histological, immunohistochemical, and ultrastructural characteristics. The neoplasm grossly consisted of a firm, pale, multilobulated mass with a characteristic clear gelatinous fluid. Histologically, the neoplasm was nonencapsulated and composed of pleomorphic stellate or spindle-shaped vimentin and periodic acid-Schiff-positive cells arranged in loose sheets and occasionally whorls. The neoplastic cells were suspended in Alcian blue-positive stroma and contained infrequent mitotic figures. Evidence of a viral etiology was not detected using electron microscopy and polymerase chain reaction. This is the first case report of a myxosarcoma in a captive European hedgehog.

"Carry-on" dermal baggage: a nodule from a dog. Pyogranulomatous inflammation with intralesional fungal agents.

A 2-year-old intact female Australian Cattle Dog presented with a 1-cm diameter nonexudative dermal nodule on the medial aspect of the right thigh. Fine-needle aspiration revealed pyogranulomatous inflammation and many ovoid, 2-4 microm diameter, thin-capsulated, basophilic bodies that appeared to be fungal spores or yeast. Results of CBC, serum chemistry panel, lymph node palpation, and radiographs were unremarkable. Excisional biopsy and histopathology revealed pyogranulomatous folliculitis, furunculosis, and perifolliculitis. Rare fungal hyphae and spore forms were intimately associated with, and occasionally within, hair shafts. A morphologic diagnosis of dermatophytosis was made and Microsporum canis infection was confirmed by fungal culture. M canis is a common infectious agent found within the follicles and superficial keratin layers of canine skin. The kerion-type clinical presentation observed in the dog of this case is uncommonly observed with M canis. Additionally, the cytologic finding of multiple arthroconidia without hyphae is unusual. In the absence of hyphae, M canis arthroconidia may be confused with other fungal yeast bodies; therefore close scrutiny of a cytologic sample for arthroconidia associated with keratin, hair fragments, or hyphal structures is recommended.

Detection of Batrachochytrium dendrobatidis in Eleutherodactylus fitzingeri: effects of skin sample location and histologic stain.

Batrachochytrium dendrobatidis is a fungal pathogen that has been implicated in amphibian declines worldwide. Histopathologic techniques have been used to diagnose the disease, but their sensitivity has not been determined. It is also unclear whether the probability of detection varies between skin samples derived from different body parts. We examined 24 Fitzinger's rainfrogs (Eleutherodactylus fitzingeri) with chytridiomycosis. This is a common frog species with a broad range and high abundance throughout most of Costa Rica. We sampled 12 different body parts from each animal, and alternated the staining between a routinely used stain (hematoxylin and eosin [H&E]), and a more fungus-specific stain (periodic acid-Schiff [PAS]). The pelvic patch and the innermost finger of the hand were consistently the best places to detect the disease, although significant differences were found only with the gular area, the abdomen, and toes four and five. We found more positive samples using PAS than using H and E in all body parts, although significant differences were detected only in samples derived from the pelvic patch. Using the best combination of factors (stain and body part) and animals with the lightest infections (to test the sensitivity of the technique), we calculated that at least 17 sections are needed in order to reach 95% confidence that a frog is or is not infected. We conclude that the choice of stain and body part can significantly alter estimates of prevalence of B. dendrobatidis.

Cryptosporidium infection in domestic geese (Anser anser f. domestica) detected by in-situ hybridization.

An in-situ hybridization (ISH) procedure was developed for the detection of Cryptosporidium sp. in paraffin wax-embedded tissues with a digoxigenin-labelled probe targeting the 18S rRNA. This technique was used in addition to traditional methods, such as haematoxylin and eosin staining, periodic acid-Schiff reaction, transmission electron microscopy and the polymerase chain reaction, to examine the bursa of Fabricius (BF), conjunctiva and other tissues from 20 domestic geese aged 16-36 days for the presence of cryptosporidia. Positive signals were found to a moderate or marked extent in both conjunctival samples (89%) and BF samples (88%) but not in other tissues. Sequencing of the PCR amplification product revealed identity with Cryptosporidium baileyi. The infected geese showed no clinical signs and only scanty histological lesions. These results confirm reports showing that young waterfowl are especially vulnerable to cryptosporidium infection and indicate that the BF and conjunctiva are the preferred sites for the presence of the protozoon. ISH proved a good method for detecting and identifying even small numbers of cryptosporidia in tissue sections.