Haemolytic anaemia associated with Theileria sp. in an orphaned platypus.

CASE REPORT: The clinical and laboratory findings in an orphaned juvenile female platypus (Ornithorhynchus anatinus) that presented with a severe anaemia and tick infestation are reported. The animal developed a terminal septicaemia and died. Antemortem clinical pathology, postmortem histopathology and 18S rDNA sequencing supported a diagnosis of extravascular haemolytic anaemia secondary to Theileria ornithorhynchi infection. CONCLUSION: Although T. ornithorhynchi infection is common in the platypus, this is the first case in which it has been shown to cause a haemolytic anaemia in this species and molecular characterisation of the organism has been described. A review of the previous literature concerning T. ornithorhynchi and possible treatment options for future cases are discussed.

Investigation into the characteristics, triggers and mechanism of apnoea and bradycardia in the anaesthetized platypus (Ornithorhynchus anatinus).

Health and conservation research on platypuses (Ornithorhynchus anatinus) may require anaesthesia to reduce stress and the risk of injury to both the animal and the researcher, as well as to facilitate examination and sample collection. Platypus anaesthesia can be difficult to manage, with reports of periods of apnoea and bradycardia described. This study investigated the conditions around sudden-onset apnoea and bradycardia in 163 field-anaesthetized platypuses as part of a health study. Anaesthesia was induced and maintained using isoflurane delivered in oxygen by face mask. Sudden-onset apnoea and bradycardia was observed in 19% of platypuses, occurring either at induction of anaesthesia, during recovery, or both. At induction, occurrence was more often recorded for adults (P = 0.19) and was correlated with low body temperature (P < 0.001), season (P = 0.06; greater incidence in summer) and longer pre-anaesthetic holding time (P = 0.16). At recovery, sudden-onset apnoea and bradycardia occurred only in platypuses that had been placed in dorsal recumbency as part of their examination, and correlated with poor body condition (P = 0.002), time in dorsal recumbency (P = 0.005), adults (P = 0.06), number of fieldworkers (P = 0.06) and females (P = 0.11). The sudden-onset apnoea and bradycardia we observed is likely to result from the irritant nature of isoflurane (stimulating the trigeminal nerve via nasal chemoreceptors). We propose that this mechanism is analogous to that of submersion of the face/nasal cavity in cold water during a natural dive response, but that the term 'nasopharyngeal response' would more appropriately describe the changes observed under isoflurane anaesthesia. Although we did not record any long-term adverse effects on platypuses that had undergone this response, the nasopharyngeal response could complicate the diagnosis of anaesthetic dose-dependent apnoea and bradycardia. Therefore, we suggest that these responses during anaesthesia of platypuses might be avoided by minimizing the stress around capture and handling, as well as reducing the time in dorsal recumbency.

Genotypic analysis of Mucor from the platypus in Australia.

Mucor amphibiorum is the only pathogen known to cause significant morbidity and mortality in the free-living platypus (Ornithorhynchus anatinus) in Tasmania. Infection has also been reported in free-ranging cane toads (Bufo marinus) and green tree frogs (Litoria caerulea) from mainland Australia but has not been confirmed in platypuses from the mainland. To date, there has been little genotyping specifically conducted on M. amphibiorum. A collection of 21 Mucor isolates representing isolates from the platypus, frogs and toads, and environmental samples were obtained for genotypic analysis. Internal transcribed spacer (ITS) region sequencing and GenBank comparison confirmed the identity of most of the isolates. Representative isolates from infected platypuses formed a clade containing the reference isolates of M. amphibiorum from the Centraal Bureau voor Schimmelcultures repository. The M. amphibiorum isolates showed a close sequence identity with Mucor indicus and consisted of two haplotypes, differentiated by single nucleotide polymorphisms within the ITS1 and ITS2 regions. With the exception of isolate 96-4049, all isolates from platypuses were in one haplotype. Multilocus fingerprinting via the use of intersimple sequence repeats polymerase chain reaction identified 19 genotypes. Two major clusters were evident: 1) M. amphibiorum and Mucor racemosus; and 2) Mucor circinelloides, Mucor ramosissimus, and Mucor fragilis. Seven M. amphibiorum isolates from platypuses were present in two subclusters, with isolate 96-4053 appearing genetically distinct from all other isolates. Isolates classified as M. circinelloides by sequence analysis formed a separate subcluster, distinct from other Mucor spp. The combination of sequencing and multilocus fingerprinting has the potential to provide the tools for rapid identification of M. amphibiorum. Data presented on the diversity of the pathogen and further work in linking genetic diversity to functional diversity will provide critical information for its management in Tasmanian river systems.

Infectivity and persistence of an outbreak strain of Salmonella enterica serotype Typhimurium DT160 for house sparrows (Passer domesticus) in New Zealand.

AIM: To examine the infective dose, incubation period and disease progression of an isolate of Salmonella enterica serotype Typhimurium definitive type 160 (DT160) originating from a naturally-infected house sparrow (Passer domesticus) during an outbreak of the disease in New Zealand. METHODS: Thirty-six house sparrows captured from the wild and free of Salmonella spp were divided into six groups of six birds, housed individually, and inoculated orally with phosphate buffered saline (PBS) or 10(1), 10(2), 10(3), 10(5), 2 x 10(8) colony forming units (cfu) of the outbreak strain of S. Typhimurium DT160. The birds were observed for 10 days for clinical signs and/or mortality, and faecal samples were collected to determine excretion of S. Typhimurium. The birds were euthanised 11 days post-inoculation (p.i.) and a wide range of tissue samples were collected for histopathological examination, and culture and typing of Salmonella spp. Macro-restriction profiling by pulsed-field gel electrophoresis (PFGE) using XbaI was performed for the epidemiological typing of S. Typhimurium DT160 isolates. RESULTS: Mortality in house sparrows inoculated with S. Typhimurium DT160 was dose-dependent, and 2/6 birds inoculated with 10(5) cfu and all six birds inoculated with 2 x 10(8) cfu died during the study. Infected sparrows displayed few clinical signs, apart from diarrhoea and/or polyuria, fluffed plumage, and sitting on the floor of the cage. Faecal excretion of DT160 occurred briefly in two birds inoculated with 10(2) cfu and four birds inoculated with 10(3) cfu, on most days in five birds inoculated with 10(5) cfu, and continuously in six birds inoculated with 2 x 10(8) cfu. DT160 was isolated from the livers of three birds which received 10(3) cfu, five birds dosed with 10(5) cfu, and all six birds given 2 x 10(8) cfu. Following necropsy, histopathological lesions similar to those seen in the natural disease were observed in the liver or spleen of three birds which received 10(3) cfu, and all birds dosed with > or =10(5) cfu. CONCLUSION: The results indicate that an isolate of S. Typhimurium DT60 originating from house sparrows in New Zealand is pathogenic to these birds and that the response is dose dependent. The persistence and excretion of the pathogen may last for at least 10 days. This confirms that sparrows infected with DT160 could be a source of infection to humans and other in-contact animals.

Prevalence and clonal diversity of Campylobacter jejuni from dairy farms and urban sources.

AIM: To investigate the role of free-living animals such as sparrows, rodents and flies as potential reservoirs of Campylobacter spp on a dairy farm, and to assess the genetic diversity among Campylobacter isolates from the farm and an urban source. METHODS: A total of 290 samples (bovine, passerine and rodent faeces, and whole flies) were collected from a large commercial dairy farm in the Manawatu district in New Zealand, and from faeces from urban sparrows in a nearby city. Other samples collected from the dairy farm included five from silage, two from aprons worn by workers during milking, two from workers' boots and two from water in troughs in a paddock. Isolates of thermophilic Campylobacter spp were identified morphologically and phenotypically and further characterised molecularly using pulsed-field gel electrophoresis (PFGE) and the restriction enzyme SmaI. RESULTS: Campylobacter jejuni was the only Campylobacter species isolated from all samples. The highest prevalence was found in faeces from dairy cows (54%), followed by faeces from sparrows from the urban area (40%) and the farm (38%), and from rodents (11%) and whole flies (9%). Other samples from the farm environment such as silage, trough water, and workers' aprons and boots were also positive for C. jejuni. Of the 22 restriction patterns obtained, seven were common to more than one source. CONCLUSIONS: Cattle, sparrows, rodents and flies are potential reservoirs of C. jejuni on dairy farms. Identical clones of C. jejuni carried by cattle, sparrows, flies and rodents probably indicate a common source of infection. The high level of asymptomatic carriage of C. jejuni by healthy dairy cows could be sufficient to maintain infections within the dairy farm surroundings via environmental contamination.

Serological responses against the pathogenic dimorphic fungus Mucor amphibiorum in populations of platypus (Ornithorhynchus anatinus) with and without ulcerative mycotic dermatitis.

Mucor amphibiorum, a dimorphic fungus, causes ulcerative dermatitis and systemic infections in the platypus Ornithorhynchus anatinus in some river systems in Tasmania but apparently not in other regions of Australia. As yet there are no suitable tests for population surveys, nor for detection of internal lesions in live animals. Consequently, immunoglobulins were purified from the serum of platypuses and anti-immunoglobulin antisera were prepared in rabbits in order to develop an enzyme-linked immunosorbent assay (ELISA) for anti-M. amphibiorum antibodies. Antigens from plate-grown cultures resulted in greater signal-to-noise ratios in indirect ELISA than those from broth-grown cultures. Platypuses with clinical ulcerative dermatitis had elevated anti-Mucor antibody levels compared to apparently unaffected individuals. Seroconversion was observed in one animal coincident with the development of cutaneous ulcers. The results suggested that platypuses in affected rivers were exposed to M. amphibiorum at a higher frequency than the occurrence of clinical disease. Some platypuses from New South Wales had elevated antibody levels but these increased significantly with age suggesting exposure to cross-reactive antigens, although exposure to M. amphibiorum cannot be excluded. Further studies are warranted to determine factors that result in progression from infection to disease, the occurrence of the fungus in areas where disease has not been observed and the specificity of antigen used in ELISA.

An epidemic of salmonellosis caused by Salmonella Typhimurium DT160 in wild birds and humans in New Zealand.

AIM: This study reports an outbreak of salmonellosis due to S. Typhimurium DT160 which caused extensive mortality in wild birds and enteric disease in humans in New Zealand during the winter and spring months of the year 2000. METHODS: Necropsies were performed and microbiological examinations undertaken on wild birds from populations in which mass mortality was reported, and on captive indigenous birds which died suddenly during the winter and spring of 2000. Affected tissues were examined histologically and isolates of S. Typhimurium were phage typed and examined using pulsedfield gel electrophoresis (PFGE). Isolates of S. Typhimurium obtained from cases of human enteric disease which occurred during these months were phage typed, examined using PFGE and compared with the bird isolates. RESULTS: Central and northern areas of the South Island and the southern North Island were worst affected with die-offs of several hundreds of sparrows and other birds reported in rural areas. Mortalities reached a peak in winter (July-August) 2000 and decreased to small numbers during the spring and early summer. The birds usually died of an acute septicaemia with multifocal necrotising lesions in the liver and spleen. Human cases throughout the country increased gradually over the same period. Isolates from birds, livestock and humans examined using PFGE were indistinguishable from one another. CONCLUSION: This strain of Salmonellahas emerged as a major cause of septicaemia in wild birds in New Zealand. Because of the close association between house sparrows (Passer domesticus) and humans, the organism also poses a serious zoonotic risk. The possibility that the infection may spread to involve indigenous species needs investigation.

Gross, histological and immunohistochemical features of mucormycosis in the platypus.

Nine male and five female adult free-living platypuses, obtained in a prospective capture-release study from northern Tasmania, exhibited gross features of cutaneous mycosis caused by Mucor amphibiorum. The lesions were present on the hind limbs (six cases), front limbs (four), tail (five), dorsal trunk (three) and ventral trunk (one). They varied in size, and ranged from raised red nodules or plaques, which sometimes exuded purulent material, to ulcerated lesions with central cavitation, red exuding centres and raised epidermal margins. Older lesions were covered either partly or fully by thickened and irregular epidermis. Histological examination of skin biopsies revealed discrete, poorly encapsulated granulomas, or more commonly a diffuse granulomatous or pyogranulomatous inflammation. Inflammatory cells consisted of neutrophils or eosinophils, sparse plasma cells and lymphocytes, many macrophages and occasional multinucleated giant cells. Fibrovascular tissue was diffusely and irregularly scattered in the granulomatous regions. Sphaerules characteristic of M. amphibiorum infection were observed in all lesions. The cutaneous distribution of the lesions and the natural history of the platypus indicated that entry of M. amphibiorum may have been via superficial skin wounds. T cells were the predominant infiltrating lymphoid cells in the diffuse lesions, indicating the importance of the cell-mediated response to infection.

Asymptomatic carriage of Cryptococcus neoformans in the nasal cavity of the koala (Phascolarctos cinereus).

Over a 22-month period, sequential nasal and skin swabs were obtained from 52 healthy captive koalas (Phascolarctos cinereus) from the Sydney region. Cryptococcus neoformans was isolated in 17 koalas from 64 of 262 (24%) nasal swabs and from nine of 262 (3%) skin swabs. Prevalence of nasal colonization varied seasonally from 12% (3/25) to 38% (10/26). Cryptococcus neoformans var. gattii alone was cultured from 37, var. neoformans alone from 22 and both varieties from five nasal swabs. Of 33 koalas sampled on three or more occasions, organisms were isolated persistently from six, occasionally from eight and never from 19. Two koalas were persistently and heavily (>/=100 colonies/plate) colonized by C. neoformans var. gattii and two with var. neoformans. Isolation of C. neoformans var. gattii from the skin was low grade and sporadic. No koalas from which C. neoformans was persistently isolated showed clinical signs of cryptococcosis and all except one had a negative latex cryptococcal antigen test, therefore the nasal cavity was presumed to be colonized by, rather than infected with, C. neoformans. Preliminary observations of koalas from Coffs Harbour indicated a much higher prevalence of colonization by C. neoformans, suggesting that environmental factors influenced the extent of carriage by C. neoformans.

Histological and immunohistological investigation of lymphoid tissue in the platypus (Ornithorhynchus anatinus).

The gross and histological appearance and the distribution of T and B lymphocytes and plasma cells are described for lymphoid tissues obtained from 15 platypuses. The spleen was bilobed and surrounded by a thick capsule of collagen, elastic fibres and little smooth muscle. White pulp was prominent and included germinal centres and periarterial lymphoid sheaths. Red pulp contained haematopoietic tissue. A thin lobulated thymus was located within the mediastinum overlying the heart. The cortex of lobules consisted of dense aggregates of small and medium lymphocytes, scattered macrophages and few reticular epithelial cells. In the medulla, Hassall's corpuscles were numerous, lymphocytes were small and less abundant, and reticular cells were more abundant than in the cortex. Lymphoid nodules scattered throughout loose connective tissue in cervical, pharyngeal, thoracic, mesenteric and pelvic sites measured 790 +/- 370 microm (mean +/- S.D., n = 39) in diameter, the larger of which could be observed macroscopically. These consisted of single primary or secondary follicles supported by a framework of reticular fibres. Macrophages were common in the germinal centres. The platypus had a full range of gut-associated lymphoid tissue. No tonsils were observed macroscopically but histologically they consisted of submucosal follicles and intraepithelial lymphocytes. Peyer's patches were not observed macroscopically but histologically they consisted of several prominent submucosal secondary follicles in the antimesenteric wall of the intestine. Caecal lymphoid tissue consisted of numerous secondary follicles in the submucosa and densely packed lymphocytes in the lamina propria. Bronchus-associated lymphoid tissue was not observed macroscopically but was identified in 7 of 11 platypus lungs assessed histologically. Lymphoid cells were present as primary follicles associated with bronchi, as aggregates adjacent to blood vessels and as intraepithelial lymphocytes. The distribution of T lymphocytes, identified with antihuman CD3 and CD5, and B lymphocytes and plasma cells, identified with antihuman CD79a and CD79b and antiplatypus immunoglobulin, within lymphoid tissues in the platypus was similar to that described in therian mammals except for an apparent relative paucity of B lymphocytes. This study establishes that the platypus has a well-developed lymphoid system which is comparable in histological structure to that in therian mammals. It also confirms the distinctiveness of its peripheral lymphoid tissue, namely lymphoid nodules. Platypus lymphoid tissue has all the essential cell types, namely T and B lymphocytes and plasma cells, to mount an effective immune response against foreign antigens.

Haematological, serum biochemical and serological features of platypuses with and without mycotic granulomatous dermatitis.

OBJECTIVE: To determine whether there are haematological, serum biochemical and serological differences between platypuses (Ornithorhynchus anatinus) with and without granulomatous dermatitis due to Mucor amphibiorum infection. An additional objective was to establish reference haematological and serum biochemical ranges for the species in Tasmania. DESIGN: A clinicopathological and serological study. ANIMALS: A total of 37 free-living adult platypuses captured from streams and dams in Northern Tasmania were used in the clinicopathological study. Twenty-seven were clinically normal and 10 had mycotic granulomatous dermatitis. A total of 22 platypuses (20 adult and 2 juvenile) were used for the serosurvey. Eighteen were captured from streams in Northern Tasmania, and four were submitted for necropsy. RESULTS: Platypuses with mycotic ulcerative dermatitis had significantly smaller packed red cell volumes, haemoglobin concentrations, lymphocyte counts, serum cholesterol and calcium concentrations, and higher serum globulin and potassium concentrations than clinically normal animals. The lymphopenia and hyperkalaemia were thought to be clinically significant. Numbers of Trypanosoma binneyi in blood smears were similar between the two groups. Diseased platypuses had higher concentrations of serum antibody against Mucor amphibiorum as determined by ELISA compared to clinically normal platypuses. CONCLUSION: Platypuses affected by mycotic granulomatous dermatitis showed haematological and serum biochemical changes when compared to clinically normal animals from the same Tasmanian sites. A serological survey may be a useful method for detecting the prevalence of exposure to Mucor amphibiorum and humoral immunity in platypus populations both in Tasmania and the mainland of Australia.

Diabetes mellitus in a koala (Phascolarctos cinereus).

OBJECTIVE: To describe a case of diabetes mellitus in a koala (Phascolarctos cinereus). DESIGN: A case report with controls. PROCEDURES: We describe clinical and laboratory findings in a 6-year-old, free-living, female koala presented with traumatic injury and subsequently found to have polydipsia, hyperglycaemia and glucosuria. Over a 5 week period, serum biochemical analyses, haematological examinations, urinalyses, measurement of serum insulin and fructosamine concentrations, necropsy, histopathological examination of a range of tissues and immunohistochemical examination of the pancreas for insulin-containing cells were done. For reference purposes, serum insulin and fructosamine concentrations were determined in four and two healthy koalas, respectively, and three healthy koalas' pancreases were examined histologically and immunohistochemically. RESULTS: The koala had persistent hyperglycaemia, hyperlipidaemia, hyponatraemia, hypochloraemia and glucosuria. Serum insulin concentration of the diabetic koala was only marginally smaller than that of healthy koalas, but all concentrations were smaller than reference concentrations in dogs and people. Fructosamine concentration did not allow the diabetic koala to be distinguished from healthy koalas and concentrations of all koala analytes were greater than expected for healthy dogs and people. Histopathological examination revealed extensive degeneration of pancreatic islet cells and fatty infiltration of hepatocytes. Immunoperoxidase staining revealed decreased or absent insulin in the beta calls of the affected koala. CONCLUSION: Clinical signs, clinicopathological results and histopathological changes were consistent with diabetes mellitus. The pathogenesis of the condition could not be determined but may have been related to the administration of a parenteral corticosteroid preparation, the stress of capture or tissue damage and inflammation.

Lymphoid neoplasia in the koala.

OBJECTIVE: Correlation of immunophenotype with history, anatomical and morphological features of lymphoid neoplasia in the koala. METHODS: Routine necropsies were performed on 51 koalas with suspected lymphoid neoplasia between 1986 and 1997 in New South Wales and Queensland. Immunophenotyping was by an immunoperoxidase method utilising species cross-reactive antibodies raised against human lymphocytes and an antibody raised against koala IgG. Cases were classified according to organs and tissues affected and the morphological features of neoplastic cells. RESULTS: Twenty-six (51%) of the cases were of the T cell immunophenotype, 12 (24%) were of B cell immunophenotype and 13 (25%) did not stain. The age and sex of koalas did not correlate with immunophenotype (P = 0.686 and P = 1.000, respectively). Thirty-two cases were leukaemic and 36 had multiple organ involvement, probably reflecting presentation of koalas at advanced stages of disease. Abdominal tissue involvement was most common (44 cases), followed by nodal (32), atypical (21) and cervicomediastinal (14). The T cell immunophenotype was over-represented among the leukaemic cases (P = 0.013). Generally, the T cell immunophenotype predominated except for many affected atypical tissues. Neoplastic cells were mostly of medium nuclear size with round to oval nuclei. No correlations were found for cell morphology, mitotic index and immunophenotype. CONCLUSION: The prognostic value of an immunophenotypic, anatomical and morphological basis for the classification of lymphoid neoplasia in the koala currently is limited by the need to detect these neoplasms at an early age, the requirement for freshly fixed tissues and the restricted range of available cross-reacting antibodies.

Cytochemical assay for differential respiratory activity in roots and root hairs.

The study of the underground parts of plants is often difficult, and as a result roots are often treated as homogeneous physiological entities with respect to root respiration. In this study we demonstrate a partitioning of respiration within root tissues using nitro blue tetrazolium staining and an incident light optical system that permits detailed observations of intact roots. The assay is rapid and easy to perform, and reveals that respiratory activity in roots is not uniform in space and time. The results show that root hairs in particular may be regions of enhanced respiratory activity in some species or in certain developmental or physiological states. This fact has important implications for the role of root hairs in the overall respiratory budget of roots and the energetics of nutrient assimilation. The results suggest that root respiration studies should consider differential respiratory activities of root cell types within roots.

Environmental scanning electron microscopic observation of the hyphal sheath and mycofibrils in Postia placenta.

Environmental scanning electron microscopic observations of Postia placenta grown on a defined medium and on red spruce wood allowed for the examination of the hydrated sheath of P. placenta. In the wood environment, mature hyphae that were not adhering to the substrate were observed to have a mycofibrillar morphology whereas hyphal tips and branch points had a smooth sheath morphology. A mycofibrillar adhesive matrix was observed on the hyphae growing on glass slides in the defined medium. These morphologies for hyphal sheaths in P. placenta are similar to those previously described by investigators from other laboratories who have used traditional electron microscopic preparative protocols that include dehydration steps. The potential future usefulness of environmental scanning electron microscopic technology in the study of the fine details of extracellular matrices is briefly discussed.

Prognostic value of Epstein-Barr virus serology in patients with nasopharyngeal carcinoma.

We report the results of a study which examined the prognostic value of Epstein-Barr virus (EBV) serology in patients with nasopharyngeal carcinoma (NPC). Antibody titres to EBV were estimated by indirect immunofluorescence and correlated with the stage of disease. Neither persistent high titres nor falling titres after treatment were found to be reliable indicators of relapse or survival, respectively, in individual patients. By contrast, four-fold rises in titre, particularly of antibodies to the early antigens of the virus were highly significant predictors of relapse. These increases could be seen well in advance of clinical detection of recurrence of the tumour at the primary or metastatic sites.

Enteroviruses in recreational waters of Northern Ireland.

Virus surveillance of Northern Ireland recreational waters, between April 1986 and May 1989 demonstrated widespread enteroviral contamination of coastal and inland waters. In 1986, enteroviruses were detected in 4 of 46 (8.7%) water samples, collected from 6 coastal bathing waters. In 1987, 49 of 107 (45.8%) samples, from 16 coastal bathing waters, yielded enteroviruses; 33 of the enterovirus positive samples passed one or both of the coliform standards outlined by the European Economic Community (EEC) bathing water directive (76/160/EEC). Enteroviruses were also detected in 33 of 39 (84.6%) samples tested from 3 inland recreational waters.

Hepatitis delta virus infection in Northern Ireland 1970-1989.

The incidence of hepatitis delta virus (HDV) infection in Northern Ireland (1970-1989) was tested by enzyme linked immunosorbent assay in 401 hepatitis B surface antigen (HBsAg) positive sera. Hepatitis delta antigen (HDAg) was tested in 388 patients and antibody to delta antigen (anti-HD) in 401 patients. Four patients (1.03%) were HDAg positive. Nine patients (2.24%) were positive for anti-HD and after acid pre-treatment of sera from eight of these patients, five were positive for HDAg. The overall incidence of HDV markers was 3.27%, which reflects the low incidence in HBsAg carriers in Northern Ireland (who were in high risk groups for delta hepatitis). The use of acid treatment of the sera to break up antigen/antibody complexes has been a useful technological improvement in the identification of this virus.

Human immunodeficiency virus infection in Northern Ireland 1980-1989.

To 31st December 1989, 71 persons are known to have attended medical practitioners in Northern Ireland with a diagnosis of Human Immunodeficiency Virus (HIV) infection. Twenty-one of these persons have had the diagnosis of Acquired Immune Deficiency Syndrome (AIDS) and 11 have died. The distribution of reports in the "at risk" categories of homosexual/bisexual males, injecting drug users, heterosexual males and females was significantly different (p less than 0.001) from those reported in the United Kingdom as a whole. Of tests for HIV infection carried out in patients attending the genitourinary medicine department of the Royal Victoria Hospital between 1987-1989, 0.16% have been positive. The prognostic value of the T4 lymphocyte count at presentation for the subsequent development of AIDS was significant (p = 0.0011). The commonest AIDS indicator disease diagnosed was Pneumocystis carinii pneumonia which was seen in seven of the 21 patients (33%).