United States-U.S.S.R. medical exchange missions, 1956 : microbiology and epidemiology.

  • United States Public Health Service
Date:
1957]
Catalogue details

Licence: Public Domain Mark

Credit: United States-U.S.S.R. medical exchange missions, 1956 : microbiology and epidemiology. Source: Wellcome Collection.

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    reaction. [Neutralization reactions were performed employing human volunteers as the indicator host; they were inoculated with a mixture of 1 volume of acute virus- bearing serum and 5 volumes of convalescent immune serum (0.01-0.05 ml. acute serum and 0.05-0.25 ml. convalescent serum). The complement fixation reaction utilized the antigen present in the acute serum obtained during the first 3 days of illness.] Thus, practical diagnosis of sporadic and epidemic cases became possible, early in the disease by complement fixation tests, and retrospectively by neutralization reaction of paired serums. Special experiments, such as those with mon- keys, disclosed absence of cross-immunity between the viruses of Omsk and Crimean hemorrhagic fever as well as the virus of sandfly fever, demonstrating that these in- fections are separate entities. [These ex- periments employed rhesus monkeys. After experimental inoculation with Crimean virus, the monkeys developed low-grade fever and an intense viremia. Hence, the serum ob- tained from monkeys during the early febrile period can be successfully used as a com- plement fixation antigen. The experimentally inoculated monkeys often exhibited exan- themata of questionable significance but they did not develop syndromes suggestive of the human disease. ] We were able to show that the gravely ill cases of Crimean hemorrhagic fever can be successfully treated with serums from con- valescent patients. In conclusion, we shall briefly characterize the third type of the virus hemorrhagic fever group, namely, the Omsk hemorrhagic fever, which was distinguished as a nosologic en- tity in 1947 by M. P. Chumakov, R. M. Akhrem-Akhremovich, A. F. Bilibin, and others. The main foci of endemic disease are in the areas of the Great Barabin steppes (Omsk and Novosibirsk regions) [...an area measuring 70 « 200 km.]. The Omsk fever is characterized by fewer hemorrhagic manifestations and lesser mortality than the other two types of hemorrhagic fever. In about half the cases, there is a double- humped fever curve with an afebrile period (3-14 days) ; not rarely, there is meningis- 24. mus, but always without paralysis; jaundice or severe renal disturbances do not occur; the fever is accompanied by leukopenia, thrombocytopenia, and a shift to the left in the leukocyte count. The specific etiological agent of the Omsk hemorrhagic fever is a filtrable virus (iso- lated by M. P. Chumakov, A. P. Belyaeva, A. V. Gagarina, and N. 8S. Slavina, 1947). The virus is highly pathogenic for mice, field mice, [...including Microtus, Steno- cranius gregalis, Ondratha tibetica], mon- keys, and many other animals. The ticks Dermacentor pictus and Dermacentor mar- ginatus were shown to be the natural reser- voirs and vectors of the infection. The infection can be transmitted via the respiratory route by inhalation of infected dust particles suspended in air (for example, under laboratory conditions) and apparently also via the alimentary route. [About 20 cases of laboratory infections had occurred. It is interesting that not one of them was associated with clinical encephalitis, which is a characteristic feature of infections with Russian spring-summer encephalitis or loup- ing ill encephalomyelitis. ] It was discovered that the virus of Omsk hemorrhagic fever is antigenically related to a number of other viruses transmitted by Ixodides ticks, namely, the viruses of spring- summer tick encephalitis, louping ill ence- phalomyelitis of Scotland, and the so-called “viral milk fever with double period of py- rexia” occurring in Central Europe. [Minor but definite quantitative differences can be demonstrated by mouse neutralization tests, using human convalescent serums; mouse neutralization tests, using animal immune and hyperimmune serums; cross-immunity in vaccinated mice; and cross-relationship by complement fixation tests using immune ser- ums. This tick-borne family can be con- trasted with a family of mosquito-borne viral neurotropic infections of the Japanese B-Murray Valley encephalitis group.] Laboratory diagnosis of the Omsk disease is made by complement fixation or neutrali- zation reactions with the virus, and isola- tion of the virus from the blood stream. [Complement fixation tests employ antigens
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