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At least 19 recordsLinked to original sources
PubMed1975

Comparative pathology of Lassa virus infection in monkeys, guinea-pigs, and Mastomys natalensis.

Experimental Lassa virus infections of squirrel monkeys, guinea-pigs, and the African multimammate rat, Mastomys natalensis, were studied virologically and pathologically. In the monkeys, early viral lymphoreticulotropism, hepatotropism, nephrotropism, and viraemia were noted. At the time of death, viral titres in nearly all target organs were associated with necrotic changes: splenic lymphoid necrosis, renal tubular necrosis, myocarditis, arteritis, and hepatocytic regeneration. In convalescent monkeys, organ titres diminished slowly, and viraemia persisted at 28 days. At this time, renal and splenic regeneration was occurring and a new lesion, choriomeningitis, was present.Guinea-pigs infected with Lassa virus developed respiratory insufficiency with pulmonary oedema, alveolar hyaline membranes, myocarditis, and focal calcification of myocardial fibres and hepatocytes. Dying animals contained Lassa virus in virtually every organ tested, whereas survivors at 56 days were free of virus and had high complement-fixing antibody titres.Infection of neonatal Mastomys did not cause any clinical disease or pathological lesions despite the presence of virus in the blood, lymph nodes, liver, spleen, lung, brain, urine, and throat secretions throughout the 74-day study. Infected adult Mastomys also remained normal but had virus in many organs. In one animal, virus persisted until the termination of the study at 103 days. Several animals developed a mild meningoencephalitis. The pattern of infection and virus shedding in M. natalensis is ideal for maintenance of the virus in nature; together with the epidemiological field data this emphasizes the incidental nature of the exposure and infection of man.

Animals↗
PubMed1977

Isolation of an arenavirus closely related to Lassa virus from Mastomys natalensis in south-east Africa.

Five unidentified virus strains were recovered from the multimammate mouse ,Mastomys natalensis, during the course of studies on arbovirus infections in Mozambique. These agents were found to be morphologically and immunologically related to Lassa virus. Four of 19 sera from Mastomys captured in the study area had antibodies to both Lassa virus and one of the unidentified strains. Although not definitive, the differences noted in results of complement fixation and indirect immunofluorescent tests suggest that these viruses from south-east Africa are not identical to West African Lassa virus.

Africa, Northern↗
PubMed1979

Lassa virus antibodies in hospital personnel in western Liberia.

The sera of 844 Liberian hospital staff memebers were positive for Lassa Virus (LV) antibodies in a survey using the indirect fluorescent antibody technique (IFAT). In two hospitals in Lofa County near the Sierra Leone border, the prevalence, 15.4%, was significantly higher than the 8.4% in seven others. There were near differences between the prevalence among laboratory workers, 15.3%, and other workers, 7.7%, and between midwifery students, 21.2%, and midwives, 4.2%, suggesting their infection from patients or their blood products. However, the over-all prevalence among those with patient contacts was the same as that among those without direct patient contact; most LV infections were apparently acquired from sources other than patients in hospital. This finding, the lack of evidence of hospital outbreaks and the presence of comparable prevalences in all age groups suggest that LV infections occur on a continuing basis in this population. In one hospital the comparison of the results of IFAT and complement fixation tests revealed some who reacted by one technique and not by the other. In one person the titre by IFAT had dropped from 1:32 to undetectable levels in two years. This finding prompts caution in the interpretation of results.

Adolescent↗
PubMed1978

Biological species in Praomys (Mastomys) natalensis (Smith), a rodent carrier of Lassa virus and bubonic plague in Africa.

Plague has been known from countries surrounding Rhodesia from as early as 1935, but was first reported from Rhodesia in 1974. Part of our investigation of the complex ecosystem involving Yersinia pestis is critical assessment of the evolutionary status of natural populations belonging to formal, taxonomic species of implicated rodents. We present data on chromosomal and hemoglobin variation in sympatric populations and laboratory produced hybrids that give unequivocal evidence for at least two biologicql species in the taxon Praomys (Mastomys) natalensis. We argue for the usefulness of the biological species concept as a basis for any ecological investigation into pathogen biology.

Animals↗
PubMed1975

Indirect immunofluorescence for the diagnosis of Lassa fever infection.

The indirect immunofluorescent technique is a rapid method for identification of Lassa virus and Lassa virus antibody. In the study reported here, Lassa virus antigen was detected by this method in Vero cell cultures within 24 hours of their inoculation with an infected human blood specimen. A diagnosis could be made from field-collected specimens within 3 days of their receipt.Fluorescent antibodies against Lassa virus were detected in human serum as early as 7 to 10 days after onset of illness, and were detected as long as 61 months after infection. Complement fixing antibodies were not as long lasting.No antigenic differences were noted by the indirect immunofluorescence technique between several Lassa virus strains isolated from Nigeria, Liberia, and Sierra Leone over a 6-year period.

Animals↗
PubMed1975

Antigenic properties of the arenaviruses.

Arenaviruses are known to show antigenic relationships in the complement-fixation (CF) and fluorescent antibody tests but not in the neutralization test. The humoral response to some of the arenaviruses is characterized by a dissociation between the antibodies determined by the CF test and those determined by the neutralization test and also by its late appearance following natural infection. Investigations are reported showing that, as regards the CF test, Junin, Machupo, Amapari, and Tacaribe viruses are closely related, while LCM and Lassa viruses are distantly related to each other and to the remaining viruses in the group. Studies by agar gel diffusion and precipitation have shown complete specificity except among viruses that are very closely related in the CF test. Observations with sera from persons infected with Lassa fever virus show that CF antibodies rarely appear before the 18th day after onset; they can persist, with diminishing titres, for up to 6 years.

Animals↗
PubMed1975

The structure of rodent faunas associated with arenaviral infections.

The biogeographical examination of rodent faunas associated with arenaviruses reveals two distinct patterns. Lymphocytic choriomeningitis (LCM) virus is associated primarily with a single murid species, Mus musculus, although it is also known to cause laboratory infections in other species. On the other hand, the arenaviruses from the Western hemisphere are associated exclusively with a large and diverse group of cricetid rodents. Studies to date, although limited, have not demonstrated their association with any other rodent groups, although in South America alone at least twelve other rodent families are known. Evidence at the present time indicates that Lassa virus is only associated with a common African rodent, Mastomys natalensis. From this limited evidence it is as yet difficult to determine whether Lassa virus will follow the pattern of the South American arenaviruses, most of which are known from several species of rodents, or that of LCM virus, which appears to be associated with only a single rodent species. In this paper, the history and structure of South American, Eurasian, and African rodent faunas are described.

Africa↗
PubMed2026

Nosocomial Outbreak of Lassa Fever in Conakry, Guinea, 2022.

BACKGROUND: Lassa fever is endemic in Guinea, with high seroprevalence in the forest region. However, clinical cases have been only anecdotally reported. In August 2022, a nosocomial outbreak occurred at a private clinic in the capital, Conakry, an area previously considered low risk. METHODS: Suspected cases were confirmed by real-time reverse-transcription polymerase chain reaction within 24 hours. Viremia was monitored during hospitalization, and whole-genome sequencing was performed in-country within 13 days of outbreak detection. Outbreak investigation involved rodent testing in the home village of the suspected primary case. RESULTS: Six cases were laboratory-confirmed, 5 of which were healthcare workers of the clinic. The case fatality rate was 16.7%. Viral RNA remained detectable in blood of survivors for a median of 26 days (interquartile range, 24-41 days) post-disease onset. Epidemiological investigations identified a suspected primary case, who had died of a febrile disease compatible with Lassa fever, had contact with all secondary cases, and had a travel history from Kissidougou area. Three near-complete and 1 partial Lassa virus genomes were recovered from the secondary cases, which phylogenetically clustered with genomes from central Guinea. Consistent with a common transmission source, the 4 genomes were almost identical. Rodent testing revealed a new reservoir area in eastern-central Guinea. CONCLUSIONS: This outbreak highlights the vulnerability of healthcare settings in low-prevalence areas of West Africa to nosocomial Lassa virus transmission due to human mobility. Facilitated by capacity-building programs for viral hemorrhagic fevers, rapid diagnosis, genomic analysis, and ecological assessment enabled an efficient outbreak response and control.

Lassa Fever↗
PubMed1978

Viral haemorrhagic fevers of man.

This article reviews the current state of knowledge on the viral haemorrhagic fevers that infect man, namely smallpox, chikungunya fever, dengue fever, Rift Valley fever, yellow fever, Crimean haemorrhagic fever, Kyasanur Forest disease, Omsk haemorrhagic fever, Argentinian haemorrhagic fever (Junin virus), Bolivian haemorrhagic fever (Machupo virus), Lassa fever, haemorrhagic fever with renal syndrome, and Marburg and Ebola virus diseases.

Animals↗
PubMed1976

Failure to prove arenavirus infection among the small mammals from an endemic area of Korean hemorrhagic nephrosonephritis.

In the light of recent knowledge on a complex of diseases caused by a new group of viruses, arenaviruses, virological studies largely directed toward small field mammals were undertaken during 1973-1974 aiming at etiological clarification of Korean hemorrhagic nephrosonephritis (KHNN). Specimens were collected in an endemic area of KHNN located north to northeast of Seoul. Virus isolation tests with 299 urine specimens and 131 mite pools recovered from small mammals and 14 acute stage sera from typical cases yielded negative results. Complement-fixation (CF) tests failed to detect antibodies against the antigens of Congo, lymphocytic choriomeningitis (LCM), Tacaribe, and Pichinde viruses among 366 small mammal sera. In addition, CF tests of 59 of the above sera against Apoi and Lassa virus antigens were negative. The results do not support the likelihood of an arenavirus being transmitted among Korean small field mammals, the overwhelming majority of which were Apodemus agrarius. A hypothesis that KHNN is caused by a virus of small field mammal origin was not proved within the technical limit of relatively unsophisticated methods employed herein.

Adolescent↗
PubMed1979

Immunoglobulin M and G responses measured by immunofluorescence in patients with Lassa or Marburg virus infections.

Immunoglobulin M antibodies can be measured by indirect immunofluorescence in sera of patients suffering from Lassa fever or Marburg virus disease 4-7 days after onset of illness. Titres reach a peak 1-2 weeks later. These antibodies disappear, or titres decrease considerably, 1-2 months after onset of illness. Antiviral IgG antibodies can be detected at the same time as, or a little later than, IgM antibodies, but they persist much longer. None of the three patients discussed in this paper who died of Lassa fever developed IgG antibodies and only one developed IgM antibodies.

Animals↗