Spontaneous and experimental infections in scid and scid/beige mice

Severe combined immunodeficient (scid) mice are valuable animals to study a variety of physiologic and disease processes. Their capacity to support multiple tissue xenografts permits these mice to be used as intermediate models for host-specific, fastidious organisms for which a small animal model has not been available previously. However, because they are unable to mount a normal immune response, they are very susceptible to a variety of primary and opportunistic microbial pathogens. Fatal, naturally occurring infections with bacteria such as Proteus mirabilis, Streptococcus viridans, and Escherichia coli have been observed. In addition, based on observations after experimental or naturally occurring viral infections, scid and scid/beige mice have been shown to be very susceptible to infections with viruses such as mouse hepatitis virus, Sendai virus, and murine respiratory virus, with resulting mortality. Of the parasitic infections, Pneumocystis carinii is a relatively common contaminant of the respiratory tracts of scid mice and may complicate research projects, particularly experimental respiratory tract infections. In view of the enhanced susceptibility of these mice to infections of this type, it is essential that they be housed under optimal conditions, which include implementing stringent management practices and a functional barrier system.

[Eosinophilic response in parasitic diseases]

The increase of eosinophiles in peripheral blood and in the lesion is characteristic feature of many parasitic diseases. Those parasites which invade host organs generally cause eosinophilia of high degree. Thus, zoonotic parasites belonging to genuses gnathostoma, paragonimus and angiostrongylus etc. bring about continuous hypereosinophilic response due to lasting larval migration, but in contrast, those which migrate temporarily during the developmental stage in the host, cause transient eosinophilia, as in Loeffler's syndrome, due to round worms. In contrast, those parasites which live in the luminal organ and never invade tissues, may not cause eosinophilia. The variety of patterns in eosinophile response is outlined together with some clinical data.

[The role of eosinophil chemotactic factor in localized tissue eosinophilia by parasitic infection]

Eosinophil chemotactic factors (ECFs) are thought to play an important role in the recruitment of eosinophils to parasitic inflammatory regions. ECF-A derived from mast cells, lymphokines from lymphocytes and ECFs from complements are well known as host-derived ECFs. On the other hand, ECF from parasites (ECF-P) and cytokines such as ESP (eosinophil stimulation promoter) and interleukin-5 are reported to be responsible for the eosinophil accumulation in parasitic inflammatory regions. In a series of our experiments using Anisakis larvae, we discovered a mechanism of eosinophil recruitment which could be accelerated by priming with ECF-P in parasite infected eosinophil phlegmon.

A survey and review of hepatobiliary lesions in Australian macropods

This report presents information on the range of diseases and lesions that occurred in sections of livers of macropods held in the Non-Domestic Animal Registry at Taronga Zoo. Of 142 affected livers, 52 were due to parasites, 24 to bacteria, nine to Macropod Herpesvirus, four to fungal agents and ten to tumours. In addition, 17 livers had acute degenerative or necrotic lesions, 22 were affected by fibrosis or other chronic lesions and four had miscellaneous degenerative lesions. Common parasitic diseases included toxoplasmosis, coccidial cholangitis, cestode cholangitis (Progamotaenia sp.), fascioliasis and capillarial hepatitis. Bacterial diseases were varied but lesions due to anaerobic bacteria or Mycobacteria spp. were most common. Many of the acute degenerative lesions were associated with cardio-respiratory disease. Chronic lesions were often of unknown origin, although it was speculated that parasitic and bacterial organisms contributed to the aetiology. There were four primary and six metastatic tumours.

Pathological findings in the Hawaiian monk seal

Postmortem examinations were performed on 45 Hawaiian monk seals (Monachus schauinslandi) collected during field research on the beaches of the Northwestern Hawaiian Islands (USA) from 1981 to 1985. Both males and females of all age groups, perinatal through adult, were examined. Frequent findings included parasites, trauma, cardiovascular disease (congenital and acquired), and respiratory infections. Emaciation was a common condition. All animals except neonates were infected with parasites; infection was severe in several cases. Splenic hematopoiesis was a universal histopathologic finding. Some cases exhibited lesions consistent with renal, gastrointestinal, and toxic disorders; ectopic tissue calcification; gallstones; and ophthalmologic and dental problems.

Sudden death due to disseminated porocephalosis--a case history

An 18-year-old Nigerian girl died suddenly and unexpectedly from disseminated porocephalosis. The patient was hospitalised complaining of fever, dizziness, weakness and jaundice. Clinical examination revealed a restless, confused and hypotensive patient. She died within two hours of admission. Autopsy revealed disseminated Porocephalus armilatus infestation involving the thoracic and abdominal linings and their internal organs. The relationship between the disseminated parasitic involvement and the death of this girl is discussed.

Liesegang rings in a needle aspirate from a breast cyst

Ringlike structures of various sizes, resembling Liesegang rings (LRs), were found in the needle aspirate from a breast cyst in an elderly woman. They were characterized by a double-layer outer wall with striations and an amorphous central nidus. Immunohistochemical stains for calcium, iron, mucus, glycogen, amyloid, cytokeratin and epithelial membrane antigen yielded negative results. Since LRs can be mistaken for ova, larvae or parasites, it is important that cytologists be aware of their occurrence, albeit infrequent, in aspirated material to avoid a misdiagnosis.

[The neuropathology of martens]

The present knowledge about the neuropathologic findings and postmortem investigation methods in neurologic diseases of martens is reviewed. Following diseases are discussed: encephalitis due to viruses (rabies, distemper), bacteria (streptococcus, staphylococcus), and parasites (toxoplasmosis, hepatozoonosis, nematodes); furthermore, metabolic disorders (amyloidosis, congophilic angiopathy, calcinosis), and congenital malformations.

Pentastomiasis in Canada

We report a case of human pentastomiasis in a 28-year-old man who emigrated to Canada from Nigeria in 1982 and died as a result of a motor vehicle accident in 1989. At autopsy, in addition to trauma, numerous small cystic nodules (3 to 9 mm in diameter) were discovered in the liver, pleura, lungs, and mesentery and under the intestinal and parietal peritoneum. The parasites were diagnosed as well-preserved, encysted Armillifer armillatus nymphs. Neither degenerative nor inflammatory granulomatous reactions were observed in the adjacent tissue. To our knowledge, this is the first reported case of human infection with encysted nymphs of A armillatus and the eighth reported case of pentastomiasis in North America.

Larval parasites in lymph nodes of slaughter cattle

Between 1977 and 1989, evidence of parasitic infection was found in lymph node sections of twelve cattle (0.5 per cent of lymph nodes) submitted by Canadian federal meat inspectors under the tuberculosis eradication program. Macroscopically, all lesions were green foci of various sizes; microscopically, parasitic larvae were surrounded by a wide zone of eosinophils. Nine larval parasites were identified in mesenteric and one parasite in an unidentified lymph node(s). Although rare, such lesions must be defined in order to differentiate them from other aetiologies such as mycobacterial and sarcocystic granulomas.

Dermatological signs of nasopharyngeal linguatulosis (halzoun, Marrara syndrome)--the possible role of major basic protein

Two hours after ingestion of improperly cooked meat a German tourist in Tunisia showed coughing, hoarseness, dysphagia, anosmia, frontal headache and epistaxis. At the same time a papular non-itching exanthema developed. The nasal discharge contained nymphs of Linguatula serrata. Histological examination of the papules revealed tissue eosinophilia and 'flame figures'. Nasopharyngeal and skin signs subsided spontaneously within 10 days. The possible role of major basic protein in the pathogenesis of nasopharyngeal linguatulosis is discussed.

Early alteration of bioprosthetic cardiac valves in sheep: influence of the immunological status

Ten Pericarbon valve bioprostheses were examined after being implanted in tricuspid position in two different groups of animals: group I sheep with increased immunoglobulins, plasma levels, and eosinophilis count of more than 10%, due to parasitic infection, and group II sheep without any parasitic infection, i.e. with normal blood data. The explanted valve follow up was between 60-95 hours in both groups. Microscopic observation of group I valves revealed a massive blood cell (lymphocytes, eosinophilis and large mononuclear cells) infiltration especially around the natural pericardial blood vessels in the region of flexion and attachment. The epipericardial surface was covered by fibrin sheath, and immunofluorescence studies showed a strongly positive reaction for immunoglobulins (IgG and IgE) on leaflet surfaces and lamellar stratification into the fibrosa. Microcalcifications were detected around pericardial blood vessels in the same zones where infiltrated blood cells were found. In group II valves cell infiltration was absent with no signs of calcification and immunofluorescence was negative. Our data suggest that immunoglobulins adherence followed by blood cell infiltration may be one of the early causes of tissue leaflet degeneration and there is a parallel trend between plasma immunoglobulin levels and the early tissue alteration. Our data show that the experimental model for testing bioprostheses in sheep is influenced by the pre-immunological status and it is important to control it before surgery.

Pathology of pleural infections

The pleura is protected by several tissue boundaries of differing degrees of strength. Penetration of the pleural space by mediastinal infection occurs more easily than from the lung, which in turn occurs more easily than through the diaphragm or chest wall. Infectious organisms of all classes, including bacteria, viruses, fungi, and protozoa are capable of causing pleural infection. The basic tissue response in the pleura is similar to that seen in other tissues but is modified by the peculiar anatomy of the pleura, flat serosal surfaces in constant motion against each other. Most pleural infections are initiated in the lung. Some of the most spectacular pathologic lesions are caused by aspergillus where vasculoinvasive fungi cause infected infarcts that result in round visceral pleural lesions. These in turn result in "kissing lesions" of the parietal diaphragmatic surfaces which are of the same size and shape as the visceral pleural lesions, indicating attachment and splinting of the pleural surfaces in these loci. Studies in rabbit demonstrate rapid resolution of experimental empyema with a standardized series of pathologic responses. In uncomplicated empyema, the end result is an extremely thin, almost undetectable scar. Thick fibrotic pleural lesions suggest a complicated course with continuing infection.

Light microscope observations of granulomatous reactions against developing Porocephalus crotali (Pentastomida: Porocephalida) in mouse and rat

The development of granulomatous reactions against moulting nymphal pentastomids (Porocephalus crotali) in the tissues of rat and mouse intermediate hosts is described. Adipose tissue and lungs are favoured sites for encystment accounting for 70% of larvae. Six moults separate the primary larva from the final infective stage which first appears about 80 days post-infection (p.i.) and is fully infective by day 120. Larvae, and particularly their cast cuticles, are the foci of granulomatous reactions characterized by an intense eosinophilia. During ecdysis, large numbers of eosinophils permeate the entire lesion but, significantly, degranulation is limited to the underside of cast cuticles where the resultant debris is endocytosed by macrophage/epithelioid cells. A pronounced asymmetry in the granulomatous lesion, evident even in the earliest cysts, results from the accumulation of individual epithelioid granulomas associated with cuticle fragments close to the ventral side of the developing parasite; each is circumscribed by fibrosis. External to this region are extensive tracts of tissue composed of mature plasma cells. Particularly in rats, large numbers of partially degranulated mast cells (= globule leucocytes) also surround cuticle granulomas, and mast cell granules can accumulate within macrophages and fibroblasts. Inflammation slowly subsides once the infective stage is attained. This 1 cm-long larva resides in a thin, fibrotic, C-shaped cyst and can remain viable for years: uniquely this instar retains its last moulted cuticle as a protective sheath. Nymphal instars II-VI feed predominantly upon eosinophils but we do not yet know whether this requirement is obligate.

Tissue parasitic diseases in Korea

Parasitic disease is still important subject in the field of infectious diseases in Korea considering it's number and morbidity. Recently there was conspicuous reduction of parasitic disease in terms of soil-transmitted nematodiasis, but parasitism affecting organs other than intestinal tract is still a considerable problem. This survey covers the parasitic diseases cross-sectioned at a pathology laboratory of a referral hospital, trying to elucidate the significance of its relative frequency and also to describe some histopathological changes made by different parasites. Entire pathological materials of parasitic diseases, that were referred, examined and confirmed at the Department of Pathology, Seoul National University Hospital from 1968 to 1987, were used for the study. There was a total of 594 cases of tissue parasitic diseases. This number accounted for 0.33 per cent of total accessions of surgical pathology. There occurred average 30 cases of tissue parasitic disease each year at this Hospital. Protozoal diseases were constituted of 15 cases of amebiasis, 7 cases of leishmaniasis (imported) and 5 cases of Pneumocystis carinii infections. Among helminthic infections cysticercosis was the most common (425 cases), and was followed by paragonimiasis (35 cases), sparganosis (31 cases), clonorchiasis (32 cases) and ascariasis (16 cases). In addition there were 4 cases of anisakiasis, 2 cases of fascioliasis, 2 cases of echinococcosis (imported) and a case of strongyloidiasis and a case of metagonimiasis respectively. It is emphasized that imported parasitic diseases such as leishmaniasis and hydatid disease become steadily found nowadays. Schistosomiasis is another possible imported disease, but not found in this series. And certain cestodiasis particularly cysticercosis and sparganosis should be the subjects of epidemiologic re-evaluation in view of steady occurrence of their morbidity.

Pseudoparasitic Liesegang structures in perirenal hemorrhagic cysts

Periodic structures with equally spaced radial striations identified as Liesegang-like rings were seen in two male patients' hemorrhagic perirenal cysts. The patients, one 48 and the other 60 years old, had acute right-flank pain and anemia; both had nephrectomy. The rings, initially believed to represent parasites (Dioctophyma renale), were from 8 to 500 micron in diameter and had uniform, pink-tan, radially striated double walls. Multiple small rings within a larger ring predominated in one case. Morphologically, the rings differed from D. renale when compared with specimens from animals infected naturally or experimentally with the giant kidney worm. Histochemical and immunoperoxidase tests for iron, calcium, mucopolysaccharides, amyloid, keratin, and hemoglobin had negative results. Energy-dispersive x-ray elemental analysis demonstrated no detectable elements; ultrastructurally, however, the rings displayed a fine fibrillary composition with a concentric and radial pattern. These rings are believed to be an end product of a phenomenon resembling or are, in fact, the Liesegang phenomenon. Because these Liesegang-like structures may be mistaken for parasites on fine-needle aspiration or surgical specimens of hemorrhagic areas, pathologists should be aware of them.

Pathology of pentastomid infections (Sebekia mississippiensis) in fish

Differential pathogenesis was observed in two species of fish naturally infected with the pentastome Sebekia mississippiensis. Mosquitofish (Gambusia affinis) showed a mild inflammatory response to developing nymphs, whereas swordtails (Xiphophorus helleri) had an extensive granulomatous inflammatory reaction with accompanying hemorrhage, myositis, and myodegeneration. This suggested that certain species of tropical fish reared in the southeastern United States may be at risk to potentially harmful infections with this parasite.

Inflammatory responses to parasites

The patients we are concerned about in tropical medicine are unfortunately affected by a wide range of conditions, not only those seen and studied extensively in the West, such as cancer, cardiovascular diseases and viral or bacterial infections, but also the major protozoan and metazoan conditions – the parasitic diseases. It is with this spectrum of pathophysiological changes that occurs in this last group that we are presently concerned and this communication is intended to present an overview of the subject.