Cutaneous and Pulmonary Mucormycosis in Rag1- and Il2rg-deficient Rats

Immunodeficient rats are valuable in transplantation studies, but are vulnerable to infection from opportunistic organisms such as fungi. Immunodeficient Rag1- and Il2rg-deficient (RRG) rats housed at our institution presented with dark, proliferative, keratinized dermal growths. Histologic and PCR results indicated that the predominant organism associated with these lesions was fungus from the family Mucoraceae, mostly of the genus Rhizopus. The Mucoraceae family of fungi are environmental saprophytes and are often found in rodent bedding. These fungi can cause invasive opportunistic infections in immunosuppressed humans and animals. We discuss husbandry practices for immunosuppressed rodents with a focus on controlling fungal contaminants.

The determination of the infectious status and prevalence of motile Aeromonas species isolated from disease cases in rainbow trout (Oncorhynchus mykiss) and aquarium fish

The aims of this study were to determine the prevalence and phylogenetic relationship of motile Aeromonas spp. that might be pathogenic species for rainbow trout in infected/mix infection cases (based upon different outbreaks on fish farms). A total of 99 motile Aeromonas isolates (and three reference strains) were analysed that were isolated from four different fish species in different sizes of fish (0.1-3,000 g), different months and water temperatures (6.1-21.2°C). The biochemical characteristics of the isolates were determined using conventional tests and a rapid test kit. Additionally, molecular identification was performed using the gyrB housekeeping gene region and with glycerophospholipid-cholesterol acyltransferase polymerase chain reaction (GCAT-PCR). The sequencing results obtained from the gyrB gene region were deposited in the GenBank database, and phylogenetic relationships were determined with the BioNumerics 7.6 database. Nearly half of the Aeromonas isolates that were isolated from rainbow trout showing signs of disease were determined to be possible infectious agents. Aeromonas species exhibit biochemical variability for many characters, so some Aeromonas species tested negative for GCAT-PCR despite that this test was created especially for Aeromonas identification. The phylogenetic tree based upon gyrB contained 10 different phylogroups that were based on 96% cut-off value in gyrB gene region.

Characterization of Demodex musculi Infestation, Associated Comorbidities, and Topographic Distribution in a Mouse Strain with Defective Adaptive Immunity

A colony of B6.Cg-Rag1tm1Mom Tyrp1B-w Tg(Tcra,Tcrb)9Rest (TRP1/TCR) mice presented with ocular lesions and ulcerative dermatitis. Histopathology, skin scrapes, and fur plucks confirmed the presence of Demodex spp. in all clinically affected and subclinical TRP1/TCR mice examined (n = 48). Pasteurella pneumotropica and Corynebacterium bovis, both opportunistic pathogens, were cultured from the ocular lesions and skin, respectively, and bacteria were observed microscopically in abscesses at various anatomic locations (including retroorbital sites, tympanic bullae, lymph nodes, and reproductive organs) as well as the affected epidermis. The mites were identified as Demodex musculi using the skin fragment digestion technique. Topographic analysis of the skin revealed mites in almost all areas of densely haired skin, indicating a generalized demodecosis. The percentage of infested follicles in 8- to 10-wk-old mice ranged from 0% to 21%, and the number of mites per millimeter of skin ranged from 0 to 3.7. The head, interscapular region, and middorsum had the highest proportions of infested follicles, ranging from 2.3% to 21.1% (median, 4.9%), 2.0% to 16.6% (8.1%), and 0% to 17% (7.6%), respectively. The pinnae and tail skin had few or no mites, with the proportion of follicles infested ranging from 0% to 3.3% (0%) and 0% to 1.4% (0%), respectively. The number of mites per millimeter was strongly correlated with the percentage of infested follicles. After administration of amoxicillin-impregnated feed (0.12%), suppurative infections were eliminated, and the incidence of ulcerative dermatitis was dramatically reduced. We hypothesize that the Rag1-null component of the genotype makes TRP1/TCR mice susceptible to various opportunistic infestations and infections, including Demodex mites, P. pneumotropica, and C. bovis. Therefore, Rag1-null mice may serve as a useful model to study human and canine demodecosis. D. musculi should be ruled out as a contributing factor in immunocompromised mouse strains with dermatologic manifestations.

Severe Dermatitis Associated with Spontaneous Staphylococcus xylosus Infection in Rag-/-Tpl2-/- Mice

Staphylococcus xylosus is a commensal bacterium found on the skin and mucosal surfaces of SPF mice. S. xylosus is rarely pathogenic, most often causing skin lesions and dermatitis in immunocompromised mice, particularly those with impaired NADPH oxidase function. Here we report spontaneous infection with S. xylosus in Rag1-/-Tpl2-/- mice. Infection was characterized by the presence of alopecia, crusts, and scaly skin. S. xylosus was detected in the feces, skin, lymph nodes, and lungs of Rag1-/-Tpl2-/- mice and led to mortality or euthanasia due to humane endpoints. C57BL/6 mice were culture-positive for S. xylosus on the skin, and Rag1-/- and Tpl2-/- mice were culture-positive on the skin and occasionally in the feces. However, S. xylosus did not cause clinical symptoms in C57BL/6, Rag1-/-, or Tpl2-/- mice. Compared with those in Rag1-/- mice, relative concentrations of circulating monocytes, but not neutrophils or lymphocytes, were increased in Rag1-/-Tpl2-/- mice, consistent with their increased incidence of clinical symptoms. Overall, this case study suggests a novel role for Tpl2 in T-cell-independent host resistance to the otherwise commensal organism S. xylosus.

Food safety in scavenger conservation: Diet-associated exposure to livestock pharmaceuticals and opportunist mycoses in threatened Cinereous and Egyptian vultures

Pharmaceuticals from veterinary treatments may enter terrestrial food webs when medicated livestock are available to wildlife in supplementary feeding stations aimed at the conservation of endangered scavengers. Here, we hypothesized that the exposure risk to livestock fluoroquinolones, as indicators of pharmaceutical burden in food, is related to the variable reliance of scavengers on domestic versus wild animal carcasses. Since the misuse of broad-spectrum antibiotics is a major predisposing factor for opportunistic mycoses, we evaluated disease signs potentially associated with diet-dependent drug exposure in nestlings of two threatened vultures. A greater occurrence (100%, n=14) and concentration of fluoroquinolones (mean±SD=73.0±27.5µgL^-1, range=33.2-132.7), mostly enrofloxacin, were found in Cinereous vultures, Aegypius monachus, due to their greater dependence on livestock carcasses than Egyptian vultures, Neophron percnopterus (fluoroquinolones occurrence: 44%, n=16, concentration: 37.9±16.6µgL^-1, range=11.5-55.9), which rely much more on carcasses of wild animals (42% of remains vs. 23% in the cinereous vulture). The chaotic, chronic and pulsed ingestion of these drugs throughout nestling development is proposed as one of the most plausible explanations for the high occurrence and intensity of oral Candida-like lesions in nestling vultures. The high occurrence of fluoroquinolone residues and disease hindered the probing of a cause-effect relationship between both factors in individual vultures. This relationship could be evaluated through a population-based approach by sampling vultures not exposed to these drugs. The high dependence of vultures on domestic animals today compared to past decades and the growing intensification of livestock farming, imply an expected increase in the impact of pharmaceuticals on scavenger populations. This requires further evaluation due to potential consequences in biodiversity conservation and environmental health. We encourage the prioritization of efforts to promote the use of less medicated free-ranging livestock carcasses left in the countryside, rather than stabled stocks made available in vulture restaurants. Additionally, attention should be paid to the population recovery of wild species that dominated scavenger diets in the past.

Frequency, Body Distribution, and Population Size of Malassezia Species in Healthy Dogs and in Dogs with Localized Cutaneous Lesions

Malassezia species are commensal organisms of human and animal skin that occasionally act as opportunistic pathogens. The lipid-dependent species are associated with human skin disorders, whereas the non–lipid-dependent species ( Malassezia pachydermatis) is considered as an opportunistic secondary pathogen affecting the canine skin surface and ear canal. This study evaluated the relationship between Malassezia yeasts, their population size, and the occurrence of skin lesions from healthy and skin-diseased dogs. The efficiency of cytological examination and fungal culture for Malassezia detection was also evaluated. From March 2002 to July 2003, 33 healthy dogs and 54 dogs with pruritic localized skin diseases were examined; skin swabs (1218) were collected from 7 anatomical sites for culture and cytological examination. Malassezia prevalence according to anatomical site and the agreement between cytological results and fungal cultures were statistically analyzed. Differences in mean colony forming unit counts between positive healthy and diseased dogs were evaluated using the Bonferroni test for post hoc pair-wise comparisons. In healthy dogs, Malassezia yeasts were most frequently isolated in the perianal and perioral areas. The frequency of isolation and population size of Malassezia species were higher in dogs with localized dermatitis, especially in affected areas, indicating a role for Malassezia in the occurrence of skin lesions. Malassezia pachydermatis was the species most commonly cultured from the skin and external ear canal of healthy and diseased dogs; isolation of lipid-dependent yeasts from healthy dogs was less frequent. Using fungal culture as the gold standard, cytological examination showed good relative specificity (95%) but very low relative sensitivity (30%).

Spontaneous bacterial and fungal infections in genetically engineered mice: Is Escherichia coli an emerging pathogen in laboratory mouse?

The impact of particular microbes on genetically engineered mice depends on the genotype and the environment. Infections resulting in clinical disease have an obvious impact on animal welfare and experimentation. In this study, we investigated the bacterial and fungal aetiology of spontaneous clinical disease of infectious origin among the genetically engineered mice from our institution in relation to their genotype. A total of 63 mice belonging to 33 different mice strains, from severe immunodeficient to wild-type, were found to display infections as the primary cause leading to their euthanasia. The necropsies revealed abscesses localized subcutaneously as well as in the kidney, preputial glands, seminal vesicles, in the uterus, umbilicus or in the lung. In addition, pneumonia, endometritis and septicaemia cases were recorded. Escherichia coli was involved in 21 of 44 (47.72%) of the lesions of bacterial origin, whereas [Pasteurella] pneumotropica was isolated from 19 of 44 (43.18%) cases. The infections with the two agents mentioned above included three cases of mixed infection with both pathogens. Staphylococcus aureus was considered responsible for five of 44 (11.36%) cases whereas Enterobacter cloacae was found to cause lesions in two of 44 (4.54%) mice. Overall, 16 of the 44 (36.36%) cases of bacterial aetiology affected genetically engineered mice without any explicit immunodeficiency or wild-type strains. The remaining 19 cases of interstitial pneumonia were caused by Pneumocystis murina. In conclusion, the susceptibility of genetically modified mice to opportunistic infections has to be regarded with precaution, regardless of the type of genetic modification performed. Beside the classical opportunists, such as [Pasteurella] pneumotropica and Staphylococcus aureus, Escherichia coli should as well be closely monitored to evaluate whether it represents an emerging pathogen in the laboratory mouse.

Fungal colonization - an additional risk factor for diseased dogs and cats?

The aim of the presented mini-review is to review the literature data referring to opportunistic mycoses in pet dogs and cats suffering from other concurrent diseases, comparable to human medical disorders with high risk of secondary mycoses. This review also presents the preliminary results of a project aimed at understanding the fungal colonization and occurrence of secondary mycoses in pets suffering from metabolic disorders, neoplasms and viral infections. The incidence of opportunistic mycoses is higher in such individuals, mostly because of their impaired immunity. The main risk factors are primary and secondary types of immunodeficiency connected with anti-cancer treatment or neoplastic disease itself. Moreover, literature data and the results of our investigations show that Candida yeasts are prevalent among diabetic animals and indicate that these fungi are the main etiological agents of secondary infections of the oral cavity, GI and urogenital tracts. Other important conditions possibly favoring the development of mycoses are concurrent infections of cats with FeLV and FIV viruses. Thus, in all cases of the mentioned underlying diseases, animals should be carefully monitored by repeated mycological examination, together with inspection of other parameters. Also, the prophylaxis of opportunistic mycoses should be carefully considered alike other factors influencing the prognosis and the outcome of primary diseases.

Mesenchymoproliferative enteropathy associated with dual simian polyomavirus and rhesus cytomegalovirus infection in a simian immunodeficiency virus-infected rhesus macaque (Macaca mulatta)

Opportunistic viral infections are common in simian immunodeficiency virus-infected rhesus macaques and include simian polyomavirus 40 (SV40), which causes interstitial nephritis, pneumonia, meningoencephalitis, and progressive multifocal leukoencephalopathy and rhesus cytomegalovirus (Macacine herpesvirus-3), which is associated with many pathologic manifestations, including the formation of neutrophil-rich gastrointestinal masses. Herein we report the findings of a simian immunodeficiency virus-infected rhesus macaque that presented to necropsy with multiple nodular masses restricted to the proximal jejunum. Histologically, the masses within the lamina propria were composed of abundant, loosely organized, mesenchymal tissue forming broad interlacing whorls and sheets admixed with variable numbers of neutrophils. Cells within the mesenchymoproliferative nodules contained numerous basophilic, intranuclear inclusion bodies with only scattered cytomegalic cells. Immunohistochemistry for rhesus cytomegalovirus and SV40 demonstrated variable numbers of immunopositive cells within the affected nodules. This report is the first description of SV40-associated pathology in the small intestine of a rhesus macaque and highlights the role that opportunistic viral infections can have on gastrointestinal pathology in immunosuppressed rhesus macaques.

[Pharmacologically immunosuppressed mice as a model for study of opportunistic parasite infections]

Immunodeficient animals are important research models for studies in parasitology, oncology and immunology. Immunosuppressive drugs have been experimentally used to obtain a state of immunodeficiency in mice. This investigation aimed to quantify the circulating T and B cells of mice treated with the immunosuppressive agents dexamethasone (Dx), cyclosporine (CsA) and cyclophosphamide (CY), as well as to observe the behaviour of lymphocytic populations in the spleen of these animals. Blood samples were collected for counting the total peripheral blood leukocytes and T and B lymphocytes using flow cytometry. Total leukocytes of mice treated with the three drugs during all study showed a significant decrease when compared to the results of the control group. The proportion of B and T lymphocytes from the treated animals also decreased significantly. Spleen sections revealed a moderate decrease in the cellularity of the white pulp and the development of lymphocyte apoptosis in mice from groups treated with CY and Dx. Results showed that the proposed experimental models demonstrated to be suitable for studies of murine immunodeficiency.

Free-living, amphizoic and opportunistic amebas

Amebas belonging to the genera Naegleria, Acanthamoeba and Balamuthia are free-living, amphizoic and opportunistic protozoa that are ubiquitous in nature. These amebas are found in soil, water and air samples from all over the world. Human infection due to these amebas involving brain, skin, lung and eyes has increased significantly during the last 10 years. The epidemiology, immunology, protozoology, pathology, and clinical features of the infections produced by these protozoa differ strikingly. Infection by the pathogenic Naegleria fowleri is acquired by exposure to polluted water in ponds, swimming pools and man-made lakes. Raised temperatures during the hot summer months or warm water from power plants facilitate the growth of N. fowleri. N. fowleri is a thermophilic ameba that grows well in tropical and subtropical climates. The CNS infection, called Primary Amebic Meningoencephalitis (PAM), produced by N. fowleri is characterized by an acute fulminant meningoencephalitis leading to death 3-7 days after exposure. Victims are healthy, young individuals with a history of recent water-related sport activities. The portal of entry is the olfactory neuroepithelium. The pathologic changes are an acute hemorrhagic necrotizing meningoencephalitis with modest purulent exudate, mainly at the base of the brain, brain-stem and cerebellum. Trophozoites can be seen within the CNS lesions located mainly around blood vessels. Thus far 179 cases have been reported; 81 in the USA alone. Balamuthia mandrillaris and several species of Acanthamoeba are pathogenic "opportunistic" free-living amebas which cause Granulomatous Amebic Encephalitis (GAE) in humans and animals. GAE is an infection, usually seen in debilitated, malnourished individuals, in patients undergoing immunosuppressive therapy for organ transplants and in Acquired Immunodeficiency Syndrome (AIDS). The granulomatous component is negligible, particularly in immunocompromised individuals. Pathologically these amebas produce a patchy, chronic or subacute granulomatous encephalitis with the presence of trophozoites and cysts. The portal of entry is probably through the respiratory tract or an ulceration of the skin reaching the CNS by hematogenous spread. As of October 1, 1996, 166 cases (103 due to Acanthamoeba and 63 due to Balamuthia) of GAE have been reported from around the world. Of these 103 cases due to Acanthamoeba (72 have been reported in the USA alone, > 50 in AIDS). It is well known that several species of Acanthamoeba can also produce, chronic sight threatening ulceration of the cornea called Acanthamoeba keratitis (AK), mostly in contact lens wearers or in individuals with minor corneal abrasions. Hundreds of cases of AK have been documented world wide.

Studies on the evolution, pathology, and immunity of commercial fattening rabbits affected with epizootic outbreaks of diarrhoeas in Mexico: a case report

Epizootic outbreaks of diarrhoeas have emerged and disseminated in different rabbit farms in Mexico causing great economical losses, during the past years. Seven, 5-weeks-old New Zealand White (NZW) rabbits chosen at random from 35 ill animals that were remitted for postmortem, histopathology, and ultrastructural examinations were studied. Bacteriological and parasitological studies were carried out in three additional ill rabbits of same age. In a field trail 45, 5-weeks-old apparently healthy NZW rabbits were observed daily for sanitary status for a 5-week period. Some of the rabbits did not response to the preventive drug treatment and were therefore, used to study the development of the disease. Clinical signs, gross lesions, and mortality throughout the fattening period were recorded. Eight, 8-weeks-old NZW rabbits who survived an outbreak were assessed for gamma-globulins in serum of the total protein fraction during a 3-week period. Gamma-globulins were also measured in eight free-disease healthy rabbits of same breed and age. Lesions of the small intestine consisted of mucoid enteropathy, lymphocytic plasmocytic enteritis with atrophy and fusion of villi, and hyperplasia of globet cells. Serosal edema was present. Ultrastructural examinations of jejunum and ileum from 3/7 diseased rabbits, revealed enterocytes in apoptosis, mixed with degenerative and/or necrotic changes together with infiltration of lymphocytes, macrophages, neutrophils, and loss of microvillus. There were electron dense structures suggestive of virus particles inside the nuclei and cytoplasm of some enterocytes. There was lymphoid spleen atrophy and proliferation of reticuloendothelial cells in 7/7 rabbits. Interstitial pneumonia in 4/7 rabbits was found. Encephalitozoon cuniculi was detected in the brain of 1/7 rabbits. Escherichia coli were detected in 3/3 cases and Eimeria spp. in 2/3 cases. Mortality rate in the field study was 51.1% and the spread of the disease occur in 9/9 cages. The proportion of gamma-globulins in rabbits who survive an outbreak was much lower (P=0.0001) than free-disease healthy rabbits (8.1+/-1.0 and 14.0+/-1.0, respectively). The disease was multifactorial and consisted of sub-acute mucoid enteropathy probably induced by viral infection and aggravated by the proliferation of opportunistic pathogens common to rabbits. This may explain the severe degenerative and necrotic changes observed in the small intestine of diarrhoeic rabbits.

A link between ectoparasite infection and susceptibility to bacterial disease in rainbow trout

Rainbow trout, Oncorhynchus mykiss, were infected concomitantly with Argulus coregoni and Flavobacterium columnare and their survival was compared with that of fish infected with either the parasite or the bacterium alone. The mortality of fish challenged with A. coregoni was negligible while infection with F. columnare alone led to significantly lower survival. However, compared with single infections, the mortality was significantly higher and the onset of disease condition was earlier among fish, which were concomitantly infected by A. coregoni and F. columnare. This data presents, for the first time, experimental support for the hypothesis that an ectoparasite infection increases susceptibility of fish to a bacterial pathogen.

Arcanobacterium pyogenes: molecular pathogenesis of an animal opportunist

Arcanobacterium pyogenes is a commensal and an opportunistic pathogen of economically important livestock, causing diseases as diverse as mastitis, liver abscessation and pneumonia. This organism possesses a number of virulence factors that contribute to its pathogenic potential. A. pyogenes expresses a cholesterol-dependent cytolysin, pyolysin, which is a haemolysin and is cytolytic for immune cells, including macrophages. Expression of pyolysin is required for virulence and this molecule is the most promising vaccine candidate identified to date. A. pyogenes also possesses a number of adherence mechanisms, including two neuraminidases, the action of which are required for full adhesion to epithelial cells, and several extracellular matrix-binding proteins, including a collagen-binding protein, which may be required for adhesion to collagen-rich tissue. A. pyogenes also expresses fimbriae, which are similar to the type 2 fimbriae of Actinomyces naeslundii, and forms biofilms. However, the role of these factors in the pathogenesis of A. pyogenes infections remains to be elucidated. A. pyogenes also invades and survives within epithelial cells and can survive within J774A.1 macrophages for up to 72 h, suggesting an important role for A. pyogenes interaction with host cells during pathogenesis. The two component regulatory system, PloSR, up-regulates pyolysin expression and biofilm formation but down-regulates expression of proteases, suggesting that it may act as a global regulator of A. pyogenes virulence. A. pyogenes is a versatile pathogen, with an arsenal of virulence determinants. However, most aspects of the pathogenesis of infection caused by this important opportunistic pathogen remain poorly characterized.

Disseminated Mycobacterium avium infection in young cats: overrepresentation of Abyssinian cats

Disseminated Mycobacterium avium-intracellulare complex (MAC) infection was diagnosed in 10 young cats (1-5 years of age) from Australia or North America between 1995 and 2004. A further two cats with disseminated mycobacteriosis (precise agent not identified) were recognised during this period. Of the 12, 10 were Abyssinian cats, one was a Somali cat and one was a domestic shorthair cat. None of the cats tested positive for either FeLV antigen or FIV antibody. The clinical course of these infections was indolent, with cats typically presenting for weight loss, initially in the face of polyphagia, with a chronicity of up to several months. Additional clinical features included lower respiratory tract signs and peripheral lymphadenomegaly. A marked diffuse interstitial pattern was evident in thoracic radiographs, even in cats without overt respiratory involvement. Hair clipped to perform diagnostic procedures tended to regrow slowly, if at all. Diagnosis was generally made by obtaining representative tissue specimens from mesenteric lymph nodes, liver or kidney at laparotomy, or from a popliteal lymph node. The primary antecedent event was most likely colonisation of either the alimentary or respiratory tract, followed by local invasion and eventual lymphatic and haematogenous dissemination. Nine cases were treated using combination therapy with agents effective for MAC infection in human patients. Two cats are still undergoing initial therapy and have responded. Of the remaining seven, all responded during long courses (5-14 months) of clarithromycin combined with either clofazimine or rifampicin, and a fluoroquinolone or doxycycline. Of these, three cats remain well (with durations between 2 months and 2 years following therapy); two developed recurrent disease (at 3 months and 2 years, respectively, following therapy) and have restarted therapy. The remaining two cats improved 1 year and 5 months, respectively, after diagnosis but ultimately succumbed. The two cats in which therapy was restarted have improved dramatically. Certain lines of Abyssinian and Somali cats likely suffer from a familial immunodeficiency that predisposes them to infection with slow-growing mycobacteria such as MAC.

Pyogranuloma caused by Mycobacterium asiaticum infection in a steer

In 2003, a steer carcass was condemned at a Central Queensland abattoir because of metastatic tumors. In addition, a granulomatous lesion was found in the mediastinal lymph node. Histological examination showed this to be a pyogranuloma, typically associated with Rhodococcus or the Nocardia/Streptomyces group. However, in this case, the only etiological agent was an acid-fast bacillus, which would normally be associated with a more fibrous lesion. A number of nucleic acid-based techniques were used, and the isolate was identified as Mycobacterium asiaticum. This organism is a rarely encountered opportunistic pathogen of humans, associated with subtropical climates. This is the first report of this organism causing infection in cattle. The similarities between this case and cases of human disease are discussed.

Infection of lung epithelial cells and induction of pulmonary adenocarcinoma is not the most common outcome of naturally occurring JSRV infection during the commercial lifespan of sheep

Jaagsiekte sheep retrovirus (JSRV) is the causative agent of ovine pulmonary adenocarcinoma (OPA). In this study, we followed over a 31-month period the natural transmission of JSRV in adult sheep and in their offspring. We established groups derived from flocks with either a high or low incidence of OPA and monitored virus transmission, clinical disease and macroscopic/microscopic lung lesions at necropsy. Results obtained show that (i) JSRV infection can occur perinatally or in the first few months of life in lambs and in adult sheep; (ii) only a minority of JSRV-infected animals develop clinical disease during their commercial lifespan; and (iii) JSRV is more readily detectable in peripheral blood leucocytes and lymphoid organs than in the lungs. These data support a model of opportunistic JSRV infection and tumorigenic conversion of type II pneumocytes/Clara cells in the lungs, while lymphoreticular cells serve as the principal virus reservoir.

[Pathological findings in pigs affected by the postweaning multisystemic wasting syndrome in Argentina]

Postweaning multisystemic wasting syndrome was first described in Canada in 1991 and at present an increasing number of cases has been diagnosed worldwide. In Argentina the first cases of PMWS were reported recently. Forty eight 5 to 12 week old pigs with signs characteristic of PMWS from 19 farms were studied. Although the real distribution of the virus in our country is not known it was observed an increasing number of farms with PMWS distributed in the major producing provinces. The histopathology was an important tool in diagnosis of suspicious cases of PMWS with the observation of different degrees of lesion. In the studied animals, the secondary infections, either by opportunistic pathogens or secondary bacteria could be important.

Systemic candidiasis in a dog

Candida albicans is a common cause of nosocomial infections in humans, but there are few reports of systemic candidiasis in dogs. This report describes an 11-year-old spayed female Scottish Terrier with systemic candidiasis. The diagnosis was made on the basis of results of microbiologic culture of specimens from urine and venous catheters and histologic examination of tissues obtained post mortem. Factors that predisposed the dog of this report to systemic candidiasis included diabetes mellitus, corticosteroid and broad-spectrum antimicrobial administration, venous and urinary catheterization, and administration of nutrition parenterally. The development of pyrexia and leukocytosis in dogs with risk factors that predispose to Candida spp infections warrants evaluation via microbial culture of specimens from urine and vascular catheters used in those dogs.

Molecular phylogenetics and diagnosis of soil and clinical isolates of Halicephalobus gingivalis (Nematoda: Cephalobina: Panagrolaimoidea), an opportunistic pathogen of horses

Phylogenetic relationships among six isolates of Halicephalobus gingivalis (Stefanski, 1954), a species with pathogenic potential in horses and humans, were evaluated using DNA sequences from the nuclear large-subunit ribosomal RNA (LSU rDNA) gene. Sequences from nematodes obtained from in vitro cultures (soil or clinical sources), or isolated from infected horse tissues, were compared. Gene sequences from a fatal equine clinical case from southern California and a free-living isolate recovered from southern California soil showed no fixed differences. Sequences from isolates representing two fatal equine cases from North America, one from Ontario, Canada and another from Tennessee also showed no fixed differences. In contrast, two equine cases from Tennessee had 18 fixed differences for this LSU region, the greatest observed among isolates from horses. Phylogenetic analysis of six Halicephalobus sequences and four outgroup taxa by maximum parsimony yielded one tree with five well-supported clades. This phylogeny did not group isolates of Halicephalobus strictly by region of geographic isolation or source of sample, and depicted one clinical and one soil isolate as sister taxa. These results confirm that free-living environmental isolates are potential sources of infection for horses. The phylogeny also reveals that diverse isolates can cause infections in horses within a relatively limited geographic region, and conversely that genetically similar sister taxa can be recovered from geographically distant localities. PCR primers that selectively amplify Halicephalobus DNA were designed and tested based on comparison of closely related nematodes as inferred from phylogenetic analysis.

Latent infection as a source of disseminated disease caused by organisms of the Mycobacterium avium complex in simian immunodeficiency virus-infected rhesus macaques

Whether infection with Mycobacterium avium complex (MAC) among patients with acquired immune deficiency syndrome results from recent exposure to virulent strains or reactivation of latent infection acquired years earlier is unknown. To address this question, tissue samples from 47 simian immunodeficiency virus (SIV)-infected and 63 SIV-uninfected rhesus macaques were cultured. MAC was cultured from 14 SIV-uninfected macaques (22.2%) and 32 SIV-infected macaques (68.1%); median bacterial burdens were 33.3 and 998.7 cfu/g, respectively. Genetically distinct strains of MAC were identified for 13 SIV-uninfected macaques (20.6%) and 15 SIV-infected macaques (31.9%). A genetically identical MAC strain (K128A) was identified for 25 SIV-infected macaques (53.2%) and 1 SIV-uninfected macaque (1.6%). Multivariate analysis identified infection with SIV/Delta(B670), diagnosis of an SIV-related tumor or opportunistic infection, and birth on site as risks for MAC infection. SIV-uninfected and SIV-infected macaques yielding unique strains of MAC were considered to have latent and reactivation infection, respectively, whereas animals infected with strain K128A were considered to have recent infection, demonstrating that both mechanisms occur among rhesus macaques.

Disseminated Mycobacterium avium complex infection following renal transplantation in a cat

An 11-year-old cat with a history of renal transplantation and treatment with cyclosporine and prednisolone was examined because of vomiting, diarrhea, inappetence, lethargy, and weight loss. Abdominal ultrasonography revealed 2 large heteroechoic masses thought to be mesenteric lymph nodes. Ultrasound-guided biopsy was performed, and histologic examination of biopsy specimens revealed granulomatous inflammation of presumptive lymph node tissue. Examination of sections stained with acid-fast stains revealed innumerable acid-fast bacilli within histiocytes, and a presumptive diagnosis of mycobacteriosis was made. The cat's clinical condition deteriorated, and euthanasia was elected. At necropsy, granulomatous inflammation was present within the mesenteric lymph nodes, spleen, liver, small and large intestines, lungs, and bone marrow. Bacterial culture yielded Mycobacterium avium, a slow-growing, opportunistic, saprophytic mycobacterium that can cause tuberculous lesions that are clinically indistinguishable from those associated with classic tuberculosis. It is a rare cause of disseminated mycobacteriosis in human transplant recipients. To our knowledge, this is the first report of disseminated M avium complex infection in a feline transplant recipient.

Equine pyoderma associated with malnutrition and unhygienic conditions due to neglect in a herd

Twelve horses kept at a riding club suffered from pyoderma. All the horses displayed crusting, scaling and alopecia. The lesions were distributed in the chest, back, rump and limbs. Some of the horse patients also showed epilation with an attached crust similar to a 'paintbrush lesion' of dermatophilosis, but normal skin flora or opportunistic pathogenic bacteria were only isolated from the lesions. Some patients clearly showed weight loss, anemia and low levels of serum protein and cholesterol. General condition and skin lesions of the patients were improved gradually with improvement of feed and environment after being moved to new stables. Malnutrition under conditions of poor hygiene and poor management due to neglect might be associated with these equine cases of pyoderma in the herd.

Opportunistic mycobacterial granuloma in a cat associated with a member of the Mycobacterium terrae complex

An 18-month-old domestic short-haired neutered male cat presented with a nodular dermal thickening on a digit. Biopsy demonstrated pyogranulomatous inflammation with moderately frequent acid-fast bacilli. A member of theMycobacterium terrae complex was isolated. There was no evidence of systemic involvement. Treatment was initiated with enrofloxacin, rifampicin and clarithromycin. After 2 months there was no longer any clinically apparent dermal thickening. Treatment was continued for a further 3 months using enrofloxacin and rifampicin.

Natural bovine lentivirus type 1 infection in Holstein dairy cattle. II. Lymphoid tissue lesions

Bovine immunodeficiency virus (BIV) in Holstein cows was associated with morphologic evidence of lymphoid organ deficiency. Cows were subjected to normal management practices including parturition and lactation without adverse environmental stresses. During the clinical disease process there was marked weight loss and wasting with frequent and severe concurrent infections. Lymphoid follicular hyperplasia and dysplasia in lymph nodes, and hypertrophy and hyperplasia in hemal lymph nodes were characteristics of the lymphoid tissues. Atrophy of lymphoid cell compartments with depletion of lymphocytes and a lymphocytic lymphoid folliculitis were components of the lymphoid system pathology. The nodal tissue lesions resembled those observed in feline, simian, and human lentiviral disease. A functional correlation with immune system deficiency was the development of multiple bacterial infections which failed to resolve after appropriate therapy. The BIV-associated disease syndrome in dairy cows may be useful as a model system for investigation of the pathogenesis of the lymphoid organ changes that occur in humans and animals with lentiviral infection.

Neuroendocrine-immune system interactions in amphibians: implications for understanding global amphibian declines

Amphibians are ancient creatures valued by biologists and naturalists around the world. They share with all other vertebrates a complex neuroendocrine system that enables them to flourish in a variety of aquatic and semiaquatic environments. Studies from a number of laboratories have demonstrated that the immune system of amphibian species is nearly as complex as that of mammals. Yet for reasons that are not well understood, amphibian species are facing greater survival challenges than in the recent past. This article will review our current understanding of the neuroendocrine immune system interactions in amphibians and address the question of whether environmental stressors may contribute to immunosuppression and amphibian declines.

Hypercapnic hypoxia compromises bactericidal activity of fish anterior kidney cells against opportunistic environmental pathogens

Acute hypoxia can cause massive fish and shellfish mortality. Less clear is the role that chronic sublethal hypoxia might play in aquatic animal health. This study tested whether production of reactive oxygen species (ROS) and bactericidal activity of fish phagocytic cells are suppressed under the conditions of decreased oxygen and pH and increased carbon dioxide which occur in the blood and tissue of animals exposed to sublethal hypoxia. Anterior head kidney (AHK) cells of the mummichog, Fundulus heteroclitus, were exposed in parallel to normoxic (pO2=45 torr, pCO2=3.8 torr, pH=7.6) or hypoxic (pO2=15 torr, pCO2=8.0 torr, pH=7.0) conditions and stimulated with a yeast cell wall extract, zymosan. or live Vibrio parahaemolyticus. Hypercapnic hypoxia suppressed zymosan-stimulated ROS production by 76.0% as measured in the chemiluminescence assay and by 58.5% in the nitroblue tetrazolium (NBT) assay. The low O2, high CO2 and low pH conditions also suppressed superoxide production by 75.0 and 47.3% as measured by the NBT assay at two different challenge ratios of cells:bacteria (1:1 and 1:10, respectively). In addition to its effects on ROS production, hypercapnic hypoxia also reduced bactericidal activity by 23.6 and 72.5% at the 1:1 and 1:10 challenge ratios, respectively. Low oxygen levels alone (pO2=15 torr, pCO2=0.76 torr, pH=7.6) did not significantly compromise the killing activity of cells challenged with equal numbers of V. parahaemolyticus. At the higher 1:10 AHK:bacteria challenge ratio, low oxygen caused a small (26.3%) but significant suppression of bactericidal activity as compared to aerial conditions (pO2=155 torr, pCO2=0.76 torr, pH=7.6). This study demonstrates that while hypoxia alone has detrimental effects on immune function, suppression of phagocytic cell activity is compounded by naturally occurring conditions of hypercapnia and low pH, creating conditions that might be exploited by opportunistic pathogens. These results indicate that the adverse health effects of chronic hypercapnic hypoxia might greatly exceed the effects of low oxygen alone.

Parasitism by the protozoan Perkinsus atlanticus favours the development of opportunistic infections

It has been suggested that opportunistic pathogens could contribute to the mortality of Perkinsus atlanticus-infected clams. Examination of Tapes semidecussatus clams from the northern Mediterranean coast of Spain revealed that while 86% of the clams heavily infected with P. atlanticus were co-infected by bacteria and/or viruses, neither non-infected nor lightly P. atlanticus-infected specimens had bacterial or viral infections. The bacteria, which had a Gram-negative cell wall, were always located in the apical pole of gill epithelial cells and enclosed within membranous compartments. Bacteria-containing cells were hypertrophied and showed dysplasia with loss of cilia and microvilli. The viruses shared ultrastructural, morphologic and cytopathic characteristics of a polyomavirus. Viral particles with icosahedral symmetry were found in both the cytoplasm and the nucleus of numerous cell types. Virus-infected cells showed severe alterations, including hypertrophy, reduction of the intracellular compartments and extrusion of the nuclear envelope. Moreover, gill epithelial cells showed disorganization and swelling of the apical region, which affected the ciliary structure. Our findings show that P. atlanticus parasitism favours the development of opportunistic infections which have detrimental effects in this clam population.

High mortality in a large-scale zebrafish colony (Brachydanio rerio Hamilton & Buchanan, 1822) associated with Lecythophora mutabilis (van Beyma) W. Gams & McGinnis

Zebrafish (Brachydanio rerio) have become an important model system for studying vertebrate embryonic development and gene function through manipulation of genotype and characterization of resultant phenotypes. An established research zebrafish colony without substantial disease problems for more than 7 years of operation began experiencing appreciable mortalities in November of 1997. Young fish (fry), from five to 24 days after hatching, spontaneously developed elongate strands of organic material protruding from the mouth, operculum, and anal pore, leading workers in the laboratory to describe the infected fish as "bearded." Unlike typical freshwater fish fungal infections, the skin surface did not have evidence of fungal colonization. The disease was associated with progressive lethargy, reduced feeding, and subsequent mortality. From 10 to 100% of the fry in a given tank were affected. Initial examination indicated that the biofilm around the head of affected fry consisted of bundles of septate fungal hyphae, large numbers of mixed bacterial populations, and protozoans. Environmental samples of air and water in the laboratory were obtained to ascertain the source of the infective agent and to isolate and identify the fungus. A fungus identified as Lecythophora mutabilis was isolated repeatedly from infected fish and water samples from infected fish tanks, and from the main laboratory water supply tanks, but not from laboratory air. Some biofilm beards on fish were found to consist of relatively pure bacterial populations, and beards on occasional fish examined in the later part of the study consisted of hyphae and spores of the oomycete genus Aphanomyces. Lecythophora mutabilis did not invade tissues; however, elimination of the epizootic correlated with reduction in the number of L. mutabilis conidia in the water following modification of the laboratory water system by use of new filtration and sterilization systems. We conclude that the dense hyphal strands of L. mutabilis composing the predominant biofilm type, along with mixed bacteria and protozoa, contributed to the die-off in young fry by occluding the oral cavity and/or gills, leading to starvation and/or asphyxiation.

Attachment of Malassezia pachydermatis to the ear dermal cells in canine otitis externa

To investigate the predominance of Malassezia pachydermatis (M. pachydermatis) as a causative agent of canine otitis externa, ear cerumen samples were observed for adhesion of M. pachydermatis to the cornified epithelial cells by light and electron microscopes. The yeasts appeared not to adhere to the cornified epithelial cells directly, but they seemed to exist in the proximity of the epithelial cells with an electron opaque halo-like space around them. Polysaccharide and lipid staining techniques were conducted to identify the substances existing in that space. Lipid substances, not saccharides, were observed around the yeasts and the cornified epithelial cells. These results suggested that in the canine ear canal malassezia yeast attachment to the cornified epithelial cells is mediated by lipids.

Detection of the Cryptosporidium parvum "human" genotype in a dugong (Dugong dugon)

The Cryptosporidium "human" genotype was identified in a paraffin-embedded tissue section from a dugong (Dugong dugon) by 2 independent laboratories. DNA sequencing and polymerase chain reaction/restriction fragment length polymorphism analysis of the 18S ribosomal RNA gene and the acetyl CoA synthethase gene clearly identified the genotype as that of the Cryptosporidium variant that infects humans. This is the first report of the human Cryptosporidium genotype in a nonprimate host.

Ornithobacterium rhinotracheale, a primary pathogen in broilers

Field strains of Ornithobacterium rhinotracheale were tested on their virulence in different chicken breeds. Ornithobacterium rhinotracheale was able to induce lesions after aerosol challenge without a previous priming with virus, and thus O. rhinotracheale was proven to be a primary pathogen. The virulence of Dutch strains, isolated between 1995 and 1998, did not increase, but the Dutch isolates and a South African strain were more pathogenic compared with an American strain of O. rhinotracheale. White specific-pathogen-free leghorns were less susceptible to O. rhinotracheale infection than broilers, whereas there was no difference in susceptibility between commercial broilers and specific-pathogen-free broilers.

Anaemia, diarrhoea and opportunistic infections in Fell ponies

This report summarises clinical and pathological observations on Fell pony foals with a range of signs that included ill thrift, anaemia, respiratory infection, glossal hyperkeratosis and diarrhoea. Some of the foals had normochromic, normocytic anaemia and some had low levels of plasma proteins, including immunoglobulin G. Antibiotic and supportive treatment was ineffective and all affected foals died or were killed on humane grounds. Postmortem examination of 12 foals and tissues from 2 other foals revealed a range of lesions that included glossal hyperkeratosis, typhlocolitis, intestinal cryptosporidiosis, granulomatous enteritis, proliferative and necrotising bronchiolitis consistent with adenovirus infection; lesions similar to those in the respiratory tract were present in the salivary gland and pancreas of individual foals. Lymphoid tissue was judged to be smaller than expected. These observations suggest the possibility of opportunistic infections secondary to some form of undefined immunocompromised state.

Isolation of Candida rugosa from turkeys

The present study describes the isolation of Candida rugosa from young turkeys that died 10 days after the end of a therapeutic treatment for a recent outbreak of coccidiosis. Candida rugosa was isolated from the digestive tract of all the birds examined. This isolation is the first in turkeys and corroborates the fact that C. rugosa is an opportunistic yeast which circumvents host defences when other predisposing factors are present.

Cryptosporidium serpentis oocysts and microsporidian spores in feces of captive snakes

Fecal smears of 90 snakes, 29 lizards, and 8 turtles and tortoises were tested for Cryptosporidium spp. oocysts and microsporidian spores. Microsporidian spores measured mean = 3.7 microm in length and mean = 2.3 microm in width and were present in feces of 19 snakes and 1 lizard (16%); 13 of these snakes also shed Cryptosporidium serpentis oocysts. The oocysts were numerous in all positive samples, whereas microsporidian spores were always sparse, irrespective if whether fecal samples contained the oocysts. Retrospective examination of reptile clinical records revealed that all animals shedding microsporidian spores died naturally due to diseases, pathologic conditions, and clinical problems or were killed due to severe cryptosporidiosis. The present study indicates that microsporidian infections in reptiles have the features of an opportunistic infection.

Outbreak of Pasteurella pneumotropica in a closed colony of STOCK-Cd28(tm1Mak) mice

Fifteen mice with Pasteurella pneumotropica orbital abscesses were noted in mice that were homozygous for a targeted Cd28 gene mutation. Only one mouse heterozygous for the Cd28 mutation was affected. According to phenotypic reactions and 16S rDNA sequencing, the isolates were most similar to biotype Heyl. This article provides evidence for an immunologic basis of susceptibility to P. pneumotropica infection. Fifteen mice with Pasteurella pneumotropica orbital abscesses were noted in mice that were homozygous for a targeted Cd28 gene mutation. Only one mouse heterozygous for the Cd28 mutation was affected. According to phenotypic reactions and 16S rDNA sequencing, the isolates were most similar to biotype Heyl. This article provides evidence for an immunologic basis of susceptibility to P. pneumotropica infection.

Opportunistic Pneumocystis carinii infection in red-bellied tamarins (Saguinus labiatus)

P. carinii infection in red-bellied tamarins (Saguinus labiatus), born and maintained in a laboratory breeding colony, was examined by histopathologic examination postmortem. P. carinii cysts were detected in 6 of 10 red-bellied tamarins examined, by using Grocott's, toluidine blue O and immunostaining with avidin-biotin complex using antisera for rat-, simian-, and human-P. carinii. The results obtained from the present studies imply that P. carinii may be an important pathogen in this species.

Systemic candidiasis in a cheetah (Acinonyx jubatus)

Systemic candidiasis, with involvement of the spleen, liver, kidneys, and lymph nodes, was diagnosed in a geriatric captive cheetah (Acinonyx jubatus). The animal had a long clinical history of intermittent chronic gastritis associated with Helicobacter acinonyx and chronic renal failure, both of which were repeatedly treated with broad-spectrum antimicrobial therapy. Following euthanasia, a postmortem examination showed numerous microabscesses and granulomas composed of degenerate eosinophils and containing asteroids or Splendore-Hoeppli material throughout the body. Yeast, pseudohyphae, and infrequently branching septate hyphae, demonstrated with special stains, were identified as a Candida sp. by fluorescent antibody testing. Low genetic variation in cheetahs may increase their susceptibility to infectious agents. Additional factors contributing to the overgrowth and dissemination of Candida sp. in this case may have included changes in the bacterial flora of the alimentary tract as a result of repeated antimicrobial therapy and alterations in the topography of the alimentary mucosa caused by chronic gastritis.

Acute stress causes skin ulceration in striped bass and hybrid bass (Morone)

Exposure of striped bass (Morone saxatilis) and hybrid bass (M. saxatilis female x Morone chrysops male) to an acute (2-hour) confinement stress caused skin ulceration on the fins but not on the body of all confined fish. Striped bass displayed more severe lesions than did hybrid bass. Histologically, lesions had varying degrees of epithelial erosion and ulceration, which was most severe at the distal portion of the fins. Ulceration was associated with dermal and hypodermal edema and necrosis of the remaining stromal tissue and tips of bone in the fin rays. No hemorrhage or thrombosis was present to suggest any obvious vascular derangement. No evidence was found for either trauma or an infectious agent initiating the lesions. Injecting fish with epinephrine caused a similar response, although the degree of ulceration was less severe. These findings may explain why many opportunistic skin pathogens can rapidly develop into serious infections in fish.

Cutaneous hyalohyphomycosis caused by Fusarium solani in a loggerhead sea turtle (Caretta caretta L.)

Fusarium solani was reported as the agent of a cutaneous infection in an injured sea turtle collected in the Mediterranean Sea. The turtle was treated with both a topical 10% solution of iodine in alcohol and ketoconazole. The source of the causal agent was traced to the sand in the tank in which the turtle was maintained. The strain was only sensitive in vitro to amphotericin B and was resistant to 5-fluorocytosine, fluconazole, itraconazole, and ketoconazole.

Intestinal manifestations of experimental SIV-infection in rhesus monkeys (Macaca mulatta): a histological and ultrastructural study

Intestinal lesions were studied in 32 rhesus monkeys experimentally infected with different strains of simian immunodeficiency virus SIVmac (251/32H, 251/32H-SPL and 251/MPBL) by light microscopy, transmission and scanning electron microscopy. A spectrum of primary and secondary manifestations of SIV-infection were detected. Primary changes included 'SIV-enteropathy' in 12 monkeys and virus-induced syncytial giant cell formation (GCF) of the intestine in two animals. A primary virus-induced enteropathy occurred both as only histologically visible 'SIV-enteropathy' and as 'AIDS-enteropathy' accompanied by clinical signs of enteritis. Secondary opportunistic infections (Balantidium coli, Cryptosporidium, Trichuris, Trichomonas, Spironucleus, Mycobacteria and Cytomegalovirus) were identified in 27 animals and three monkeys developed malignant lymphomas involving the intestinal tract. Compared to intestinal lesions in HIV-infected patients, differences were found concerning the incidence of GCF and the range of opportunistic infections, with cryptosporidium, cytomegalovirus and mycobacteria occurring in both SIV-infected macaques and AIDS patients. The present observations revealed that SIV-infected rhesus monkeys provide an excellent model both for studies on the pathogenesis of HIV-enteropathy and opportunistic infections and for the development of therapies against cryptosporidial, cytomegalovirus and mycobacteria infection. Comparison of three SIV-strains revealed differences in primary and secondary lesions observed: SIVmac251/MPBL was correlated with severe primary SIV-induced pathologic changes and SIVmac251-SPL-infected animals showed a higher incidence of malignant lymphomas.

Fungus Paecilomyces: a new agent in laboratory animals

The fungus Paecilomyces has not yet been considered a health problem in laboratory animals. However, this agent known as a 'spoiler' of fruit beverages and other foodstuffs is an opportunistic pathogen especially in immunocompromised humans. Since 1985, we have isolated Paecilomyces, most probably P. variotti, from six laboratory animal species, mainly rats. In about 90% of cases the organism was localized in the respiratory tract and there are some other findings favouring the hypothesis of an airborne infection. During this long observation period no consequences for the health of rats in one closed 'infected' SPF breeding unit (A) could be observed. In a controlled histological study on five infected rats, no lesions attributable to this mycotic agent could be detected. However, a self-limiting spontaneous outbreak of papular skin lesions associated with Paecilomyces was observed in a breeding colony (F) of hairless mice. The role of this fungus in an acute outbreak of respiratory signs in another colony of conventional rats (B) was considered to be secondary. Bearing in mind its occasionally harmful role in humans, relatively high resistance to disinfectants and toxigenicity, this new agent should be monitored and considered a potential health risk for laboratory animals.

Two related strains of feline infectious peritonitis virus isolated from immunocompromised cats infected with a feline enteric coronavirus

Two groups of cats were experimentally infected orally with the cat-passaged RM strain of feline enteric coronavirus (FECV-RM). One group of cats (n = 19) had been chronically infected with feline immunodeficiency virus (FIV) for over 6 years, while a second control group (n = 20) consisted of FIV-naive siblings. Fecal virus shedding of FECV occurred in both groups starting on day 3 postinfection, nearly ceased by 4 weeks in FIV-uninfected cats, but remained at high levels in FIV-infected animals. FIV-infected cats shed virus for a longer period of time and at levels 10 to 100 times greater than those for FIV-uninfected cats. The coronavirus antibody response of the FIV-infected cats was delayed and of reduced titer compared with that of the FIV-uninfected animals. Cats in both groups remained asymptomatic for the first two months following FECV-RM infection; however, 8 to 10 weeks postinfection two cats in the FIV-infected group developed feline infectious peritonitis (FIP). The FIP viruses (designated FIPV-UCD9 and -UCD10) isolated from these two cats had almost complete genetic homology to each other and to the infecting FECV-RM. However, unlike FECV-RM, they readily induced FIP when inoculated intraperitoneally into specific-pathogen-free cats. This study confirms that FIPVs are frequently and rapidly arising mutants of FECV. Immunosuppression caused by chronic FIV infection may have enhanced the creation and selection of FIPV mutants by increasing the rate of FECV replication in the bowel and inhibiting the host's ability to combat the mutant viruses once they occurred.

Cryptosporidiosis of the conjunctiva in SIV-infected rhesus monkeys

Cryptosporidium was found on the conjunctiva of 6 SIV-infected immunodeficient rhesus monkeys. Some affected membranes were inflamed. The conjunctiva is a newly recognized site for disseminated Cryptosporidium infection in spontaneously infected immuno-deficient mammals, and clinicians and investigators should be aware of its possible presence in immunodeficient patients with disseminated cryptosporidiosis.

Mycotic dermatitis in an Atlantic white-sided dolphin, a pygmy sperm whale, and two harbor seals

An Atlantic white-sided dolphin (Lagenorhynchus acutus), a pygmy sperm whale (Kogia breviceps), 2 harbor seals (Phoca vitulina) developed raised, firm, erythematous, cutaneous nodules that were most prominent on their heads, trunks, and on the caudal portions of their bodies. Prior to the onset of the condition, all 4 animals may have been stressed by factors such as being stranded on a beach, being transported long distances, or being relocated locally. Microbial culturing of the lesions on multiple media yielded fungal isolates containing conidia characteristic of Fusarium spp. Hyphae consistent with those of an ascomycete were evident on histologic examination of lesions. In each treated animal, the dermatitis resolved 3 to 4 weeks after completing treatment with ketoconazole. Fusarium spp may be opportunistic invaders of the skin of marine mammals that have decreased immunocompetence or integumentary compromise.

The pathogenesis of necrotic proliferative colitis in swine is linked to whipworm induced suppression of mucosal immunity to resident bacteria

Mucohemorrhagic enteritis syndrome in swine has a complex etiology with largely unknown pathogenesis. We have observed that inoculation of pigs with swine whipworm, Trichuris suis, initiates an interaction with resident bacterial flora to induce mucohemorrhagic enteritis. The role of bacteria in this mixed infection was demonstrated using 4 treatment groups. One group of pigs was inoculated with 2500 embryonated T. suis eggs alone, while a second group received T. suis eggs along with broad spectrum antibiotic treatment. Two other control groups of pigs were uninoculated and were either treated with antibiotic or untreated. Pigs inoculated with T. suis eggs exhibited diarrhea, mucosal edema, inflammatory cell infiltration, bacterial accumulation at the site of worm attachment in the proximal colon, and intestinal adenomatosis associated with the intracellular Ileal symbiont intracellularis bacteria. In addition, enlarged lymphoglandular complexes (LGCs) containing numerous extracellular bacteria, eosinophils, lymphocytes, macrophages, and neutrophils were observed in the distal colon. The other group of pigs that was inoculated with T. suis but treated with antibiotics had lesions localized to the site of worm attachment and histologically normal LGCs with no invasive bacteria in the distal colon. The groups of uninoculated pigs, with or without antibiotic treatment, exhibited no pathology or bacterial invasion. It appears that the complex pathogenesis of necrotic proliferative colitis in pigs may be linked to worm induced suppression of mucosal immunity to resident bacteria. Further, the association between bacteria,lymphocytes and macrophages in the LGCs of pigs infected with T. suis suggests an antigen-processing role for these structures in the colon. Further, the complex pathogenesis of necrotic proliferative colitis in pigs may be linked to worm induced suppression of mucosal immunity to resident bacteria.

Encephalitis, lymphoid tissue depletion and secondary diseases associated with bovine immunodeficiency virus in a dairy herd

Encephalitis, lymphoid tissue depletion and secondary infections occurred over a 5-yr-period in Holstein cows infected with bovine immunodeficiency virus (BIV). There were 59 cattle studied, the majority during 1991, when a severe environmental stress occurred, each with one or more primary causes of death, natural or by euthanasia, and most with several secondary diseases. The encephalitis was characterized by meningeal, perivascular and parenchymal infiltration with lymphocytes, occasional plasma cells and macrophages with perivascular edema in some cows. Affected areas included the cerebrum, cerebellum, and spinal cord with no particular distribution pattern recognized. The lymphoid depletion was primarily an absence of follicular development in nodes draining regions with secondary infections such as chronic mastitis and chronic suppurative pododermatitis. Paucity of lymphocytes in thymic-dependent regions of lymph nodes and the spleen suggested a primary depletion of T cells. Secondary infections were often multiple with each cow having several minor conditions, usually considered short-term and treatable. These included mastitis and pododermatitis, with many cows having non-responding abscesses, cellulitis and myositis attributed to injection site infections. A large number of the cattle had parturition difficulties such as dystocia, obturator paralysis, and metritis. Pulmonary, cardiovascular, and intestinal disease were recognized as both primary and secondary disease conditions. There was a high level of infection with bovine leukemia virus with 4 of the 59 cattle having lymphosarcoma. Under practical conditions, the infection with BIV has a different effect on the host than has been observed under experimental conditions. The presence of BIV combined with the stresses associated with parturition and a modern dairy production system were considered causal for the development of untreatable secondary diseases in immunocompromised cattle. The peak incidence in 1991 was attributed to increased environmental stress during renovation of the barn facility. During this time the cattle were kept on open pasture, exposed to an extremely wet winter, and spring weather conditions. The effect of co-infection with bovine leukemia virus, the influence of immunocompromise on the chronicity of mastitis, the relationship with laminitis and pododermatitis, and several questions related to viral transmission, complementarism with bovine leukemia virus, viral reactivation and immunoprophylaxis all remain as viable avenues for future investigations.