Hepatic amebiasis in spider monkeys.

In the past, investigators have been able to produce hepatic amebiasis in laboratory animals only by direct introduction of parasites into the liver or its vasculature, or by other artificial manipulations. A natural model of human visceral amebiasis has been lacking. We document an extensive outbreak of amebic dystentery which took place in a colony of spider monkeys; severe hepatic abscesses occurred in many animals. The spider monkey is highly susceptible to infection with Entamoeba histolytica and could provide a valuable model for the study of the pathogenesis of invasive amebiasis.

Sleep abnormalities with REM disorder in experimental Creutzfeldt-Jakob disease in cats: a new pathological feature.

Alterations in sleep organization were studied during the clinical phase of experimental Creutzfeldt-Jakob disease (CJD) in cats. Twenty months after intracerebral inoculation of a CJD agent, cats developed clinical signs including behavioral changes, diminished grooming activity, dysmetria, startle reflex, myoclonus, and unusual sleep abnormalities. Rapid eye movement (REM) sleep displayed a new and irreversible organization, with a continuous and constant pseudoperiodic pattern of rapid eye movements, synchronous with diffuse bursts of cortical abnormalities and with ponto-geniculo-occipital (PGO) wave activity. Computer analysis revealed a constant morphology of cortical bursts and their temporal relationship with ocular episodes. Induction of PGO wave activity with benzoquinolizine derivative Ro 4-1284 demonstrated the PGO-dependent nature of the cortical alterations. Abnormal unresponsive states were observed during REM sleep phases and arousal thresholds were increased in CJD cats during REM sleep. The percentages of wakefulness and slow-wave sleep were reversed in these animals. Preliminary neuropathological observations included discrete to minimal spongiosis of cerebral gray matter and a remarkably focalized intracytoplasmic vacuolation in neurons of the raphé system. Our findings suggest that particular neuronal systems involved in sleep regulation are impaired in CJD cats.

Serological survey of Prospect Hill virus infection in indigenous wild rodents in the USA.

We found serological evidence of infection with Prospect Hill virus, a Hantaan-like virus isolated from meadow voles (Microtus pennsylvanicus), in microtine and cricetid rodents trapped in Maryland, West Virginia, Minnesota and California, USA. Fluorescent antibodies were detected in sera from M. pennsylvanicus (74/277), M. californicus (39/185), Clethrionomys gapperi (5/51), Peromyscus maniculatus (4/22) and P. truei (1/11). Sera from seropositive P. maniculatus contained neutralizing antibodies against Prospect Hill virus, confirming that infection with Prospect Hill virus or antigenically related viruses is not restricted to microtine rodents in the USA. Despite the widespread distribution of Prospect Hill virus in indigenous rodents, the recent demonstration that American mammalogists are only rarely infected supports the view that the overall risk of Prospect Hill virus infection in man is low.

Transmission of Ehrlichia canis to dogs by ticks (Rhipicephalus sanguineus).

Two strains of Rhipicephalus sanguineus acquired Ehrlichia canis by feeding as either larvae or nymphs on acutely infected dogs and, in subsequent instars, transmitted the agent to normal dogs. Three strains of R sanguineus transmitted E canis as adults after their larval and nymphal stages fed on infected dogs. More than 400 adult female ticks were fed on infected dogs as larvae or nymphs or both, but none transmitted E canis transovarially.

Epizootiology of tropical canine pancytopenia.

Tropical canine pancytopenia (TCP) is a newly recognized infectious disease of dogs in diverse tropical and subtropical areas. The disease is characterized by hemorrhage, pancytopenia, severe emaciation and persistent infection. Dogs with TCP are often presented with epistaxis, which is the most dramatic sign of the disease; however, a large number of affected dogs develop severe pancytopenia and die without manifesting clinical signs of hemorrhage. The disease has been reported most frequently in the German Shepherd. Pathological findings consist of petechial and ecchymotic hemorrhages on serosal and mucosal surfaces of numerous organs. The most prominent histological finding is a perivascular plasma cell infiltrate in most organs. Disease, indistinguishable from the natural disease, has been produced in laboratory dogs inoculated with whole blood from affected dogs. Ehrlichia canis has been consistently recovered from all experimentally infected dogs. Attempts to transmit the disease to other laboratory animals and to propagate the agent in cell cultures and embryonating eggs have been unsuccessful. The tick is the probable vector of the disease.

Experimental infection with Puumala virus, the etiologic agent of nephropathia epidemica, in bank voles (Clethrionomys glareolus).

Subclinical chronic infections characterized by transient viremia, prolonged virus shedding in oropharyngeal secretions and feces, and virus persistence in tissues (particularly lung) developed in laboratory-bred weanling bank voles (Clethrionomys glareolus) inoculated intramuscularly with Puumala virus (strain Hällnäs), the etiologic agent of nephropathia epidemica. Viral antigen, as evidence by granular fluorescence, was detected in the lungs, liver, spleen, pancreas, salivary glands, and small intestine. Infectious virus was found in the lungs from 14 to 270 days postinoculation, and feces and urine collected 35 to 130 days postinoculation were regularly and sporadically infectious, respectively. Horizontal transmission coincided with virus shedding in oropharyngeal secretions. Suckling voles also developed asymptomatic persistent infections after intracerebral inoculation, and histopathological changes were absent despite widespread infection. Our data resemble findings in Apodemus agrarius experimentally infected with Hantaan virus, the prototype virus of hemorrhagic fever with renal syndrome, suggesting that the mechanisms of maintenance and transmission of Puumala and Hantaan viruses are similar in their respective wild-rodent hosts.

Indirect immunofluorescence tests in Korean hemorrhagic fever and epidemic (endemic) nephropathia: treatment at low pH for removal of 'nonspecific' fluorescence in tissues from immunocompetent hosts.

A 'nonspecific' fluorescence probably caused by immunocomplexes appears in the lung tissue of immunocompetent hosts infected with Korean hemorrhagic fever (KHF) or epidemic nephropathy (EN) viruses. Indirect immunofluorescence tests with such KHF- or EN-infected tissue as antigen are unsatisfactory for the detection of low-titer antibody or the reading of titer endpoints. Treatment of acetone-fixed lung sections at pH 3.0 followed by washing with 0.01 M phosphate-buffered saline and distilled water apparently dissolves the immunocomplexes, resulting in an effective removal of the 'nonspecific' fluorescence while the viral antigens are not significantly impaired. Lung sections of KHF-infected Apodemus agrarius coreae and EN-infected Clethrionomys glareolus, acetone-fixed and treated at pH 3.0, were used for the antigenic differentiation of the EN and KHF viruses.

Differential susceptibility and resistance of immunocompetent and immunodeficient mice to fatal Hantaan virus infection.

Susceptibility and resistance to fatal Hantaan virus meningoencephalitis were studied in immunocompetent (nu/+) and congenitally T-cell deficient (nu/nu) CD-1 mice of different ages. Susceptibility of nu/+ mice to fatal infection was age-dependent, as evidenced by 100 percent mortality in mice inoculated intracerebrally with Hantaan virus (strain 76-118) during the first week of life, 60 percent mortality in mice inoculated at 9 days of age, and no disease or death in mice inoculated at 14 to 42 days of age. Deaths occurred significantly earlier in nu/+ mice inoculated at 5 and 7 days of age than in nu/+ mice less than 24 hours old. Nu/nu littermates of the same age did not exhibit a similar inverse relationship between age and survival times. Moreover, nu/nu mice 14 days or older remained susceptible, albeit with delayed onset of illness and time of death. Virus titers in brain tissues of nu/+ mice inoculated at 7 days and of nu/nu mice inoculated at 7, 9 and 14 days of age were nearly identical. In older nu/+ mice, peak virus titers were comparatively lower, but they did not seem to be influenced by the magnitude of the neutralizing antibody response. The more rapidly fatal course in nu/+ mice inoculated at a week of age than at birth, and the differential resistance between weanling nu/+ and nu/nu mice to Hantaan virus meningoencephalitis suggest that cell-mediated immunity may be responsible for both enhancement of disease and recovery from infection.

Creutzfeldt-Jakob disease in mice: persistent viremia and preferential replication of virus in low-density lymphocytes.

The mode of replication of the "unconventional virus" of Creutzfeldt-Jakob disease was studied in BALB/c mice infected intracerebrally. Virus was detected in the brain, spleen, lung, thymus, liver, kidney, and blood, but not in urine, at various time intervals after inoculation. The highest infectivity was present in the spleen from the second through the ninth weeks postinfection. Density gradient separation of spleen cells with colloidal silica (Percoll) revealed that the highest concentration of virus was present in blastoid cells from lower-density (1.05 to 1.07 g/ml) fractions. These results suggest that blastoid cells play an important role as the initial replication site of virus in the pathogenesis of Creutzfeldt-Jakob disease in mice.

Oral transmission of kuru, Creutzfeldt-Jakob disease, and scrapie to nonhuman primates.

Kuru and Creutzfeldt-Jakob disease of humans and scrapie disease of sheep and goats were transmitted to squirrel monkeys (Saimiri sciureus) that were exposed to the infectious agents only by their nonforced consumption of known infectious tissues. The asymptomatic incubation period in the one monkey exposed to the virus of kuru was 36 months; that in the two monkeys exposed to the virus of Creutzfeldt-Jakob disease was 23 and 27 months, respectively; and that in the two monkeys exposed to the virus of scrapie was 25 and 32 months, respectively. Careful physical examination of the buccal cavities of all of the monkeys failed to reveal signs or oral lesions. One additional monkey similarly exposed to kuru has remained asymptomatic during the 39 months that it has been under observation.

Evidence for an unconventional virus in mouse-adapted Creutzfeldt-Jakob disease.

Homogenates of a human brain from a case of Creutzfeldt-Jakob disease and a homogenate of mouse brains from mouse passage 1 of the disease in mice contained no detectable conventional viruses. Both human material and mouse-passaged material were inoculated into nude mice, and the mouse-passaged material was also inoculated into eight different tissue culture lines. The tissue cultures showed no cytopathic changes or hemadsorption and failed to produce an increased amount of reverse transcriptase. The nude mice inoculated with human brain suspensions developed a disease identical to that in immunocompetent mice, with a nearly identical incubation period of 9 to 13 months. The incubation period of the disease in mice was under host genetic control and was, additionally, directly related to the inoculum size. The agent was resistant to 10% Formalin, 5% deoxycholate, 1% Triton X-100, and 5% glutaraldehyde; however, glutaraldehyde treatment resulted in a significant loss of infectivity. Approximately 1 log of infectivity was lost by heating brain suspensions to 80 degrees C for 15 min, with no additional loss upon further incubation up to 45 min. Heating at 100 degrees C for 15 min led to a 3-log loss of infectivity.

Low-calcium, high-aluminum diet-induced motor neuron pathology in cynomolgus monkeys.

Long-term epidemiological studies indicate that environmental factors play a causative role in high-incidence amyotrophic lateral sclerosis (ALS) and parkinsonism-dementia (PD) in the western Pacific. An increased risk for disease is acquired in youth and remains for life. The low concentrations of calcium and magnesium and high levels of aluminum in the soil and drinking water, along with the relative isolation of these populations, constitute an unusual environmental feature common to all three high-incidence foci. Studies of mineral deposition in brain tissue of Guamanian ALS and PD patients, as well as of neurologically normal Guamanians with neurofibrillary degeneration, demonstrate accumulations of calcium, aluminum and silicon in neurofibrillary tangle-bearing neurons. In an attempt to duplicate the low calcium and high aluminum and manganese in soil and drinking water in these foci, we maintained juvenile cynomolgus monkeys for 41 to 46 months on a low-calcium diet with or without supplemental aluminum and manganese. Experimental animals exhibited mild calcium and aluminum deposition and degenerative changes, compatible with those of early ALS and PD, in motor neurons of the spinal cord, brain stem, substantia nigra and cerebrum. Neuropathological findings included chromatolysis, aberrant perikaryal accumulation of phosphorylated neurofilament, neurofibrillary tangles, axonal spheroids, and basophilic and hyaline-like inclusions consisting of abnormal cytoskeletal elements by electron microscopy. The magnitude and extent of these lesions far exceeded those found in normal aged monkeys.

Experimental hantavirus infection in nonhuman primates.

Mild, transient proteinuria and azotemia were produced in three cynomolgus monkeys (Macaca fascicularis) and a chimpanzee (Pan troglodytes) following intravenous inoculation with Prospect Hill virus, a hantavirus isolated from meadow voles in the United States. This is the first demonstration of an acute nephropathy in nonhuman primates with the viruses causing hemorrhagic fever with renal syndrome.

Propagation of Korean hemorrhagic fever virus in laboratory rats.

Korean hemorrhagic fever virus (KHFV) has been adapted to the Wistar and Fisher strains of rats. Infection was detected by the appearance of specific antigen in the lung tissue of the infected rats at 14 to 64 days after inoculation and by the appearance of circulating antibodies in ther serum which reacted specifically with KHFV antigen in the lungs of infected Apodemus agrarius subsp. coreae 3 weeks after inoculation. Distribution of antigen in rat tissues as determined by immunofluorescent staining was the same as that in Apodemus mice except that antigen was present in the spleens of rats. Adaptation of KHFV to the laboratory rat provides an animal model that is free of wild rodent viruses and is readily available for use in studies on the characterization of KHFV.

Antibodies in urine of chimpanzees with chronic adenoviral viruria.

Many chimpanzees have naturally occurring chronic intermittent viruria with an adenovirus of a new type called Pan 11. Small amounts of neutralizing antibodies to Pan 11 adenovirus were found in the urine of chimpanzees. Urinary antibodies to adenovirus were mainly of the immunoglobulin G (IgG) class with some IgA antibodies also present. There was no neutralizing activity in urine against another adenovirus, Pan 9, which has been isolated from lymph nodes, but not from urine, of chimpanzees; however, sera of all chimpanzees had neutralizing antibodies to Pan 9 virus, some with titers similar to those of antibodies against Pan 11 virus. Antibodies reacting with simian cytomegalovirus by indirect immunofluorescence were found in sera of all chimpanzees tested and in two of six urines. There was no correlation between levels of antiviral IgG antibodies in serum and urine by immunofluorescence. These findings suggest that both IgG and IgA antibodies may be locally produced in response to viral infection of the urinary tract in primates.

Transmission of Creutzfeldt-Jakob disease to a chimpanzee by electrodes contaminated during neurosurgery.

Stereotactic multicontact electrodes used to probe the cerebral cortex of a middle aged woman with progressive dementia were previously implicated in the accidental transmission of Creutzfeldt-Jakob disease (CJD) to two younger patients. The diagnoses of CJD have been confirmed for all three cases. More than two years after their last use in humans, after three cleanings and repeated sterilisation in ethanol and formaldehyde vapour, the electrodes were implanted in the cortex of a chimpanzee. Eighteen months later the animal became ill with CJD. This finding serves to re-emphasise the potential danger posed by reuse of instruments contaminated with the agents of spongiform encephalopathies, even after scrupulous attempts to clean them.