Rapid diagnosis of viral infections in the central nervous system

Rapid diagnosis of viral infections in the central nervous system has become increasingly important. Antiviral treatment, prevention of spread of disease and differentiation from infections caused by agents sensitive to antibiotics may be the important consequences of a virus specific diagnosis gained early in the disease. The diagnosis can be obtained by detection of virus or viral antigen in the human specimen: herpes simplex virus by electron microscopy, immunofluorescence or immunosorbent assays in brain biopsies; rabies virus by immunofluorescence in corneal cells or skin and mucous membranes. The presence of measles or influenza antigens in nasopharyngeal secretions, shown by immunofluorescence or enzyme immunoassays, may diagnose an encephalitis caused by either of these viruses. Where suitable material is not available the detection of virus-specific IgM in a single serum specimen may be used for diagnosis. Mumps specific IgM activity is detected by enzyme-linked immunosorbent assay (ELISA) or indirect immunofluorescence techniques; tick-borne encephalitis (TBE) specific IgM by immunosorbent assays or by reduction of hemagglutination-inhibition (HI) titer by 2-mercaptoethanol treatment of serum. Reports have been given on the detection of IgM activity by ELISA also in other arboviral infections such as Japanese and LaCrosse encephalitis. The demonstration of an intrathecal production of virus-specific immunoglobulins may reveal the type of virus causing the infection in the central nervous system.

[Outbreak of arbovirus infection in the Tadzhik SSR due to the Issyk-Kul virus (Issyk-Kul fever)]

An outbreak of the disease caused by Issyk-Kul virus was observed in March-August, 1982, in southern Tajikistan. The virus is ecologically associated with bats and Argasid ticks parasitising on them. The role of birds and mosquitoes in the virus ecology is discussed, and the data on the population immunity patterns to the virus among humans, domestic and wild animals in the Kirghiz SSR, the Tajik SSR, and the Turkmen SSR are analysed. The data on the distribution area of the causative agent in the Central Asia are presented.

Detection of viruses in spinal fluid

Among the confirmed cases of viral meningitis and encephalitis, the most commonly diagnosed agents are enteroviruses, arboviruses, and herpes simplex virus. Definitive diagnosis of a viral infection often affects patient management, length of hospitalization, and antibiotic use. Laboratory diagnostic methods include microscopic examination of clinical specimens, virus culture, serologic studies, and immunologic detection of virus or viral antigens. Microscopic examination of cerebrospinal fluid is nonproductive, and, except for enteroviruses, culture almost always gives negative results. Viral culture of the cerebrospinal fluid, throat, and feces is the diagnostic method of choice for enteroviruses. Definitive diagnosis of herpes simplex virus encephalitis must be based on virus isolation from brain biopsy material. Arbovirus infection is diagnosed serologically. Although none of the newer rapid immunologic techniques is commercially available, some do hold great promise. These include measurement of virus-specific immunoglobulin M (IgM) and detection of viral antigens by enzyme or radioimmunoassay. A sensitive and specific procedure for early detection of herpes simplex virus antigens in cerebrospinal fluid would be of great benefit.

Serologic evidence of arbovirus infections in humans and wild animals in Alaska

Blood samples were collected from humans and several species of free-ranging wild animals in Alaska. Sera were tested for antibody to Jamestown Canyon (JC), snowshoe hare (SSH), Northway (NOR), Klamath (KLA), Sakhalin (SAK), Great Island (GI), and Silverwater (SIL) virus. JC antibody was found in 54% of 121 human, 89% of 97 bison (Bison bison), 51% of 84 Dall sheep (Ovis dalli), 43% of 68 snowshoe hare (Lepus americanus), and 3% of 33 arctic fox (Alopex lagopus) sera. SSH antibody was found in 42% of 121 human, 89% of 97 bison, 41% of 84 Dall sheep, and 65% of 68 snowshoe hare sera. NOR antibody was found in 14% of 121 human, 94% of 97 bison, 84% of 84 Dall sheep, 43% of 69 caribou (Rangifer tarandus), 3% of 68 snowshoe hare, 48% of 64 grizzly bear (Ursus arctos), 3% of 33 arctic fox, and 78% of 27 moose (Alces alces) sera. KLA antibody was found in 5% of 121 human and 40% of 97 bison sera. SAK antibody was found in 2% of 97 bison and 3% of 33 arctic fox sera. GI antibody was found in 1% of 97 bison sera. No SIL antibody was found in any sera tested. Thus the natural host ranges of JC, SSH, NOR, and KLA viruses have been extended by inference from the occurrence of antibody.

[Etiology of Karelia fever--a new arbovirus infection]

In August-September 1981, in some areas of Karelia (on the border of northern and middle taiga) there occurred diseases with signs of fever, rash, and arthralgia developing in some patients into a chronic condition. Examinations of paired sera from patients with the acute disease and from convalescents using a set of Toga- and Bunya-viruses showed the etiology of the disease to be associated with a virus from the Togaviridae family, genus Alphavirus, of the antigenic Sindbis complex.

[Standardization of preparations intended for the serodiagnosis of arboviruses]

As the result of our research work, 3 reference preparations have been first obtained and studied in accordance with all requirements of biological standardization. These preparations are the national standard of yellow fever antiserum and immune ascitic fluids (IAF) used as reference reagents: IAF to tick-borne encephalitis virus and IAF to Japanese encephalitis virus. The new preparations are stable, possess sufficient specific activity and can be used as standard preparations for the identification of the above-mentioned viruses.

Arthritides caused by mosquito-borne viruses

Five different mosquito-borne viruses (chikungunya, o'nyong-nyong, Mayaro, Ross River, and Sindbis) have been associated with arthritis in humans. These agents occur most commonly in the tropics and subtropics. The symptoms they produce are similar and typically consist of fever, arthralgia, and rash. In general, the symptoms are of short duration (less than one week) and recovery is complete, although some patients have recurrent episodes of joint swelling and tenderness for months after infection. Treatment is symptomatic. There are no vaccines currently available; the best prevention is to avoid mosquito bites when traveling or living in areas where these diseases occur.

Early diagnosis of viraemia in some experimental arbovirus infections in mice

Viraemia was demonstrated by the indirect haemagglutination (IHA) test in newborn white mice infected with dengue type 1 and 2 and Japanese encephalitis viruses but not with Chikungunya virus. The IHA allowed the detection of viraemia in the flavivirus infections before the appearance of clinical symptoms of the disease and was strictly specific.

[Arbovirosis from Central African Republic: incidence, diagnosis in human pathology (author's transl)]

The authors report results obtained about human arboviroses studied in the laboratory of Institut Pasteur of Bangui from 1966 to 1979 in Central African Republic. 74 cases are described; 36 strains from different serological Casal groups have been isolated and, in 38 cases, a serological conversion have allowed a diagnosis. The peculiar conditions of virological and clinical diagnosis are discussed.

[Minor arboviral diseases in Central and West Africa (author's transl)]

Many arboviruses can cause febrile illness in man, with or without rash, quite apart from yellow fever and the aetiological agents of haemorrhagic fevers. Exanthema are one of the commonest signs. Neuro-vascular attacks frequently occur and in some cases meningitic complications can happen. Diagnosis is often difficult: viraemia is of short duration and complement fixing antibodies do not appear consistently in convalescent serum. In Central and West Africa, 19 different arboviruses have been implicated either by isolation or by serological conversion. Some were isolated from man for the first time.

[Tick-borne viruses in tropical area (author's transl)]

Arboviruses, transmitted by ticks and pathogenic to man in tropical areas, are discussed. They are considered according to, first the faunal region in which they can be found, then the type of syndrome they cause. The greater part is of little medical importance, some are noxious but of a rare occurrence (Thogoto, Wanowrie, Langat) or geographically restrained (Kyasanur forest disease), so the Crimean-Congo hemorrhagic fever is the only infection to show a notorius importance. As severe in the tropics of the oriental faunal region (Pakistan, India) as it is Europe, it seems to be of little importance in the afrotropical faunal region. Nevertheless, its severity remains to be ascertained by the means of extensive serological surveys and by taking in account this virus in presence of every hemorrhagic syndrome.

Comparison of haemagglutination inhibition (HI) and indirect fluorescent antibody (IFA) techniques for the serological diagnosis of certain flavivirus infections

Paired serum samples from 25 patients having clinical evidence of arboviral infections and 15 controls were examined for antibodies against dengue, Japanese encephalitis and West nile viruses by haemagglutination inhibition (HI) and indirect fluorescent antibody (IFA) methods. The two tests were comparable in specificity but the IFA test was found to be more sensitive than the HI test. Like the HI test, the antibodies detected by IFA test cross-reacted within the flavivirus group under test. Use of IFA test is recommended to detect flavivirus infections as the test is simple, sensitive and can be carried out rapidly.

Epidemic polyarthritis acquired in Fiji

Four cases of epidemic polyarthritis which was acquired in Fiji between April and July of 1979 are described. The manifestations of the illness were similar to those of the disease in Australia. Knowledge of the geographic distribution of this disease can be valuable in diagnosis, but it is likely that its range is not yet fully known.