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PubMed1975

Problems of rodent control in rural tropical areas.

Rodent control strategies, techniques, and research needs in rural tropical environments are reviewed and discussed with special reference to Mastomys natalensis, the possible reservoir of Lassa fever in West Africa.Public health rodent problems are far more serious and widespread in rural tropical areas than in developed countries. In the latter, only the commensal rodents constitute a major problem, whereas in rural tropical areas, native semidomestic species also serve as disease reservoirs and sources of infection to man. The success of rodent control programmes in developed countries depends in large part on the willingness and ability of people and governments to spend relatively large sums on research and control, on an acquired intolerance of people to rats and disease, and on a substantial economic base. These prerequisites are not usually to be found in rural tropical areas. Consequently, the rodent control techniques and programme organizations of developed countries are not directly applicable to such areas, even though the principles are the same. For this reason, it is suggested that a well-funded, integrated research and control programme should be undertaken in a known Lassa fever area, stressing public education, personnel training, and environmental management as well as rodenticidal approaches.

Africa, Western↗
PubMed2006

Reverse ELISA for IgG and IgM antibodies to detect Lassa virus infections in Africa.

BACKGROUND: Anti-Lassa antibodies are detected by indirect immunofluorescence assay (IFA) or by enzyme-immunoassay (ELISA). Both methods have problems to detect low amounts of specific antibodies. OBJECTIVES: We report here highly sensitive and specific reverse ELISAs to detect Lassa virus IgG and IgM antibodies. Due to the reverse techniques, serum samples could be applied at dilutions of 1:10 without increasing non-specific background reactions. STUDY DESIGN: For IgM antibody detection microtiter plates were coated with anti-IgM antibodies and for IgG antibody detection with rheumatoid factor (RF) (Sachers M, Emmerich P, Mohr H, Schmitz H. Simple detection of antibodies to different viruses using rheumatoid factor and enzyme-labelled antigen (ELA). J Virol Methods 1985;10:99-110). In both assays a tissue culture antigen was used in combination with a labeled anti-Lassa monoclonal antibody (Hufert FT, Ludke W, Schmitz H. Epitope mapping of the Lassa virus nucleoprotein using monoclonal anti-nucleocapsid antibodies. Arch Virol 1989;106(3-4):201-12). RESULTS: The reverse ELISA turned out to detect virus-specific IgG and IgM antibody in all 20 samples of West African patients collected 2-8 weeks after onset of Lassa fever. Moreover, both IFA and reverse ELISA found IgG antibodies in 53 out of 643 samples of healthy West Africans (sensitivity of 100%). Six of the 643 samples were positive by reverse IgG ELISA only. Thus, the specificity compared to IIF was 99.0%, but it may be even higher, because compared to IFA the IgG ELISA was clearly more sensitive in detecting low antibody titers. CONCLUSIONS: In Ghana 3% seropositives were found by IFA, but 4% by the reverse ELISA. The reverse ELISAs can be performed with high sensitivity and specificity under field conditions in Africa.

Africa↗
PubMed1996

Imported vector- and rodent-borne virus infections--an introduction.

Travel is a potent force in the emergence of virus infections. Migration of humans and animals has been the pathway for disseminating virus diseases throughout history. In recent years, dengue virus has been identified as the most important travel-related, vector-borne virus disease. Other vector-borne virus infections, such as sandfly fever, Rift Valley fever, chikungunya fever and Japanese encephalitis, have been diagnosed in travelers returning from endemic areas. Crimean-Congo haemorrhagic fever may not only be imported by infected live stock, but also by travelers. Of rodent-borne virus infections, Lassa fever has been diagnosed occasionally in travelers returning from endemic areas. The potential impact of imported filoviruses is currently discussed.

Animals↗
PubMedDate not supplied

Exotic viral diseases.

Marburg virus disease, Lassa fever, monkeypox, and Ebola virus diseases of humans have all been recognized since 1967. These are examples of some of the exotic virus diseases which through importation may present a potential public health problem in the United States. Some of these viruses are also highly hazardous to laboratory and medical personnel. This paper is a review of the general characteristics, the epidemiology, and laboratory diagnosis of the exotic viruses which have been described during the last 25 years.

Animals↗
PubMed1991

Venezuelan haemorrhagic fever.

An outbreak of severe haemorrhagic illness began in the municipality of Guanarito, Portuguesa State, Venezuela, in September, 1989. Subsequent detailed study of 15 cases confirmed the presence of a new viral disease, designated Venezuelan haemorrhagic fever. Characteristic features are fever, toxicity, headache, arthralgia, diarrhoea, conjunctivitis, pharyngitis, leucopenia, thrombocytopenia, and haemorrhagic manifestations. Other features include facial oedema, cervical lymphadenopathy, nausea/vomiting, cough, chest or abdominal pain, and convulsions. The patients ranged in age from 6 to 54 years; all were residents of rural areas in central Venezuela, and 9 died. Infection with Guanarito virus, a newly recognised arenavirus, was shown by direct culture or by serological confirmation in all cases. Epidemiological studies suggest that the disease is endemic in some rural areas of central Venezuela and that it is rodent-borne. Venezuelan haemorrhagic fever has many similarities to Lassa fever and to the arenavirus haemorrhagic fevers that occur in Argentina and Bolivia.

Acute Disease↗
PubMed1978

Wild rodents as laboratory models and their part in the study of diseases.

The paper describes the use of 14 South African wild rodent species as experimental models and demonstrates the proven value of many of these as laboratory animals in research on bacterial infections (plague, relapsing fever), rickettsial infections (tickbite fever, louse typhus), viral infections (poliomyelitis. Rift-Valley fever and other arbovirus infections, Lassa fever), fungal infections (histoplasmosis), parasitic infections (schistosomiasis) and in diabetes mellitus and cancer research.

Animal Husbandry↗
PubMed2005

Arenavirus extinction through lethal mutagenesis.

Viral hemorrhagic fevers represent serious human public health problems causing devastating and often lethal disease. Several hemorrhagic fevers are caused by arenaviruses including Lassa fever virus (LFV) and the South American viral hemorrhagic fevers (SAHF). In recent years, increased air travel between Africa and other areas has led to the importation of LFV into the US, Europe, Japan, and Canada. This has raised awareness about arenaviruses as potential emerging viruses. Moreover, because of its severe morbidity and high mortality, and transmissibility from human to human, weaponized forms of LFV poses a real threat as agent of bioterrorism. No licensed vaccine is available in the US, and currently there is not efficacious therapy to treat these infections. Therefore, the importance of developing novel effective antiviral drugs to combat HF arenaviruses, for which the prototypic Arenavirus lymphocytic choriomeningitis virus (LCMV) provides us with an excellent model system. Recent findings have shown that LCMV multiplication both in cultured cells and in vivo is highly susceptible to the mutagenic agent 5-fluorouracil (FU). FU-mediated extinction of LCMV was associated with only modest increases in virus mutation frequencies, but did not significantly affect virus replication and transcription, or virus particle formation. These findings indicate that, as with other riboviruses, lethal mutagenesis is effective also against LCMV raising the possibility of using this novel antiviral strategy to combat pathogenic arenaviruses.

Animals↗
PubMed1982

Spondweni virus infection in a foreign resident of Upper Volta.

Spondweni virus is a mosquito-borne flavivirus previously reported to cause human disease in Southern and West Africa. A serologically confirmed case of Spondweni virus infection in a U.S. citizen residing in Upper Volta is reported. Symptoms included fever, chills, headache, myalgia, nausea, and rash. A greyish mucoid lining was present on the posterior pharynx. The differential diagnosis included rickettsial infection, leptospirosis, typhoid fever, and numerous viral illnesses including Lassa fever. Evidence of Spondweni virus infection was also found in two other U.S. citizens residing in Gabon and Cameroon. Spondweni virus might be a cause of acute febrile illness throughout West Africa, and its presence should be considered in the differential diagnosis of febrile illness and in antibody surveys in that region.

Adult↗
PubMed1996

Viral haemorrhagic fevers: current status, future threats.

In developing countries, the major outbreaks of viral haemorrhagic fevers such as Marburg, Ebola and Lassa fever viruses have been nosocomially spread. The high mortality and absence of specific treatment have had a devastating effect. Epidemics of this highly contagious disease remain a constant threat to Australia and, as a result, carefully planned laboratory and public health strategies and clinical infection control measures have been instituted for the management of suspected cases.

Animals↗
PubMed1983

Case-control study of Mastomys natalensis and humans in Lassa virus-infected households in Sierra Leone.

Lassa virus infection and antibodies were studied in households where Lassa fever cases occurred, and compared to those in nearest neighbor houses and "far" houses located across the village from case houses. Seventy-nine percent of all rodents caught in the houses were Mastomys, the natural reservoir of Lassa virus. Rodent infection was not randomly distributed, but rather focal. Thirty-nine percent of the Mastomys in case houses were viremic, compared to 3.7% in control houses. Human antibody prevalence in case houses was 30%, compared to 20% in non-case houses (P less than 0.05, chi-square test, df = 2). Neither seroconversions nor antibody prevalence rates were associated with household size or number of persons per room. Trapping of rodents in half of the case and control houses resulted in a Mastomys reduction ranging from 2.2- to 3.3-fold. This reduction failed to significantly reduce the seroconversion rate to Lassa virus in the people of trapped houses compared to those in untrapped ones. More complete trapping will be needed in order to better evaluate this procedure as a means of interruption of Lassa virus transmission in endemic villages.

Animals↗
PubMed1986

Hemorrhagic fever virus infections in an isolated rainforest area of central Liberia. Limitations of the indirect immunofluorescence slide test for antibody screening in Africa.

Serum samples from 119 healthy individuals and 106 epilepsy patients inhabiting Grand Bassa County, Liberia, were tested for antibodies to hemorrhagic fever viruses (HFV) by indirect immunofluorescence. E6 Vero cells infected with Lassa fever virus (LAS), Rift Valley Fever virus (RVF), Congo Hemorrhagic Fever virus (CON), Marburg virus (MBG) and the Ebola (EBO) virus strains Mayinga (May) and Boniface (Bon) were used as antigen. To obtain reproducible and specific test results sera had to be absorbed extensively with uninfected E6 Vero cells, tested for reactivity to both virus infected and uninfected E6 Vero cells and read "blindly" by two independent observers. Antibodies to EBO were shown to be highly prevalent (13.4%) in the population of this rainforest area, while prevalences of antibodies to LAS (1.3%), RVF (0.4%) and MBG (1.3%) were much lower. No correlation between past HFV infection and post-encephalitic epilepsy or other reported febrile illnesses could be established.

Adolescent↗
PubMed2005

Examples of tropical disease control in the humanitarian medical programmes of MSF and Merlin.

Humanitarian medical programmes in the tropics have the opportunity to provide beacons of good practice. The use of modern drugs and diagnostics, a lack of bureaucracy, adequate budgets, motivated staff and well-functioning supply lines all contribute to the success of this approach. At a joint meeting of the Royal Society of Tropical Medicine, the London School of Hygiene and Tropical Medicine, Médecins Sans Frontières and Merlin, new data were presented on the outcomes of recent humanitarian programmes to control malaria (Ethiopia), human African trypanosomiasis (south Sudan), Lassa fever (Sierra Leone) and tuberculosis (Tomsk, former USSR).

Antimalarials↗
PubMedDate not supplied

[Study of certain indicators of immunity upon infecting CBA/Calac line mice with Lassa virus].

Some immunity parameters (interferon, tumor necrosis factor, interleukin 1, etc.) were studied in CBA/Calac mice infected with Lassa virus. The results permit a hypothesis that a pathologic inflammatory reaction is responsible for the death of animals in experimental Lassa fever. One of the components of this reaction is endogenous shock involving a manifest production of immune response mediators, such as interferon, interleukin 1. and tumor necrosis factor.

Animals↗
PubMedDate not supplied

Evaluation of infection control practices during an AE.

The broadening global commitment of UK military personnel since the end of the Cold War has brought them into contact with a plethora of tropical diseases, some of which require isolation and air transfer to a UK medical facility. This presents a number of challenges to the safe repatriation of patients and attending medical and flight crews. During a recent repatriation of a patient with suspected Lassa fever from West Africa, the team's practices were evaluated and recommendations were made for improvements to future transfers by the deployable air isolator team. Valuable lessons were learned by the team, most notably the need to practice safe isolation procedures in a real working environment. In addition, the team should work on exercises together, thus aiding cohesion prior to deployment.

Aerospace Medicine↗
PubMed1986

Ribavirin: a clinical overview.

Ribavirin, a broad spectrum, non-interferon-inducing virustatic chemotherapeutic agent, demonstrates activity against a wide range of RNA and DNA viruses, including the retrovirus known to cause the acquired immune deficiency syndrome. The drug's proposed mechanism of action, as well as pharmacokinetics are discussed, and preclinical toxicity, safety and clinical efficacy studies are presented. To date, the best success has occurred in the use of ribavirin to treat respiratory syncytial virus infection in infants and young children and to treat influenza A and B virus infections in young adults. Viral infections, particularly viral pneumonia, are often life-threatening in infants with severe combined immunodeficiency disease (SCID), and ribavirin aerosol has been used successfully to treat respiratory syncytial virus and parainfluenza virus infection of immunodeficient children. Special note is taken of ribavirin's clinical benefit in treating severe and life-threatening infections caused by the Lassa fever virus and the significant improvement over either the use of immune plasma or supportive therapy alone. Indeed, ribavirin thus emerges as the first antiviral drug that is able to reduce mortality in a highly lethal systemic disease by more than 90%. Additional studies demonstrate the drug's efficacy in acute viral hepatitis, herpesvirus infections, and measles. Controlled clinical trials are underway to test the drug in patients infected with the AIDS virus.

Clinical Trials as Topic↗
PubMed2000

Zoonotic infections in Nigeria: overview from a medical perspective.

Infections of domestic and wild animals that are transmitted directly or by an arthropod vector to humans are a major cause of morbidity and mortality worldwide and particularly in Nigeria. With a population of over 100 million and the need for improved health care delivery, Nigerians are at considerable risk considering the seriousness of these infections. Zoonotic infections that are endemic in Nigeria include tuberculosis, trypanosomiasis, toxoplasmosis, taeniasis, rabies, lassa fever and yellow fever. Zoonotic food-borne infections (caused by Campylobacter, Salmonella and Escherichia coli O157:H7) and cryptosporidiosis are emerging. Sporadic cases such as strongyloidiasis, ascariasis, leptospirosis, scabies, pentastomiasis and African histoplasmosis have been reported. There is a need to determine the prevalence of tick-borne zoonoses. Prevention and control of zoonoses in humans is by vaccination, treatment and health education. As a first measure to improve control, the link between veterinary and medical officers, which is presently very weak, needs to be strengthened. Furthermore, regional multidisciplinary approaches to the control of zoonotic infections should be adopted in West Africa, which take into consideration the huge inter-border traffic.

Animals↗
PubMedDate not supplied

Hemorrhagic fevers, with special reference to recent outbreaks in southern Africa.

In considering the diagnosis of a patient admitted to the Johannesburg Hospital, suffering from an illness characterized by high fever and complicated by a hemorrhagic state from which he died, a list of possible causes of his illness was drawn up. This list included the arthropodborne viral infections prevalent in southern Africa, namely, chikungunya fever, Sindbis fever, West Nile fever, yellow fever, and Rift Valley fever; viral infections associated with rodents, such as Lassa fever; the viral infection associated with monkeys, Marburg virus disease; the rickettsial infections; tick-bite fever (the variety of spotted fever of tick typhus occurring in southern Africa) and Q fever; the bacterial infections, especially the coccal infections, plague septicemia, and meningococcal, staphylococcal, and streptococcal septicemia; and the blood protozoal infections malaria and trypanosomiasis. In addition, rubella, Gasser's syndrome, Henoch-Schönlein purpura, and viperine snakebite were briefly described in this review. All of these conditions may be complicated by the development of a hemorrhagic state. The circulation of large numbers of infecting organisms, by they viruses, rickettsiae, bacteria, or protozoa, may initiate the coagulation cascade, the formation of fibrin and its deposition in the finer blood vessels, and the aggregation and entanglement of platelets resulting in marked thrombocytopenia and bleeding. This bleeding tendency is greatly aggravated when the infection specifically involves the parenchymal cells of the liver; such a condition results in defective formation of coagulation factors such as prothrombin. The proper care of patients in whom a hemorrhagic state has developed requires urgent and accurate diagnosis followed by immediate and appropriate treatment that will combat the infection and alleviate the hemorrhagic state and liver disorder. If the hemorrhagic state is due to one of the dangerous infectious fevers, adequate protection of the medical, nursing, and laboratory staff concerned is also vital.

Adolescent↗