Hemorrhagic Fevers

Hemorrhagic Fevers 

a group of natural-focus viral diseases transmitted from animals to man. Hemorrhagic fevers have common clinical symptoms—elevated temperature (fever), and subcutaneous and internal hemorrhages. Several kinds are distinguished according to the pathogen and the way in which the infection is spread.

Hemorrhagic fever with renal syndrome (hemorrhagic nephrosonephritis) occurs in Europe and Asia in the form of epidemics and sporadic (isolated) cases. The mechanism of transmission is not wholly clear. However, one possibility is that the disease is transmitted by gamasid ticks. Natural foci can be formed in different landscapes (forest, steppe, or tundra). Several species of mouselike rodents are reservoirs of the infection. The incubation period is 11-24 days.

Crimean hemorrhagic fever occurs in the form of sporadic cases in the southern steppe regions of the USSR (the Crimea, Taman’ Peninsula, Rostov Oblast in the RSFSR, southern Kazakhstan, Uzbek SSR, Kirghiz SSR, Turkmen SSR, and Tadzhik SSR) as well as in Bulgaria—that is, wherever ixodid ticks (Hyalomma) are prevalent. The disease spreads in the spring and summer. Its incubation period is two to seven days. The pathogen remains in the patient’s blood throughout the febrile period. The blood serum of a convalescent possesses specific antiviral properties.

Omsk hemorrhagic fever develops in people living in Siberian villages situated near lakes, in hunters and members of their families, and in the Barabinsk Steppe (in nonvacci-nated individuals). Outbreaks associated with epizootics among game animals occur in the fall and winter. Ixodid ticks (Dermacentor) are the carriers of the disease, which has an incubation period of three to seven days. The virus is found in man throughout the febrile period.

Tickborne Indian fever (Kyasanur Forest disease) is caused by a virus similar to the pathogen of Omsk hemorrhagic fever. Sporadic cases occur in the spring and summer. The incubation period is four to eight days. The virus is isolated from sick persons, monkeys, several species of forest rodents and birds, and from ixodid and gamasid ticks.

Argentine or Bolivian hemorrhagic fever occurs mainly in agricultural workers and members of their families when corn is harvested. The virus is isolated from persons, field rodents, and gamasid ticks (Haemophysalis) that infest them. The incubation period is two to 11 days.

Mosquito fevers, which occur in some countries of Asia, Africa, and Oceania, are similar to hemorrhagic fevers. However, they differ from them slightly in the course of the disease. In all probability, they are also transmitted to man from animals, but the natural reservoirs of the infection have not yet been discovered. The pathogen (virus) is transmitted by mosquitoes. Mosquito fever virus is isolated from sick persons (in the early stages of the disease) and from mosquitoes.

Hemorrhagic fevers generally have an acute onset: chills, fever (in cases of Omsk, Indian, and sometimes mosquito fevers), headache, and pronounced weakness. Hemorrhages (nasal, gastric, intestinal, uterine, renal, cavitary, from the gums, subcutaneous) or hemorrhagic rashes appear on the skin and mucous membranes. Changes take place in the blood (leukopenia and, in hemorrhagic fever with renal syndrome, leukocytosis) and in the internal organs. (Hemorrhagic fever with renal syndrome results in kidney lesions, which are manifested by sharp pain in the small of the back and sometimes, because of changes in the renal tubules, by cessation of urination.) There may also be changes in the nervous system. (Hemorrhagic fever with renal syndrome and Crimean, Argentine, and mosquito fevers often result in collapse and shock.) Those recovering from the disease are permanently immune to it.

Symptomatic treatment involves maintenance of cardiac activity and control of bleeding. In Argentine and hemorrhagic fever with renal syndrome, dehydration must be controlled by injection of large amounts of normal blood plasma and electrolytes and hormonal preparations, such as corticosteroids. In cases of Crimean hemorrhagic fever, administration of specific serum is beneficial.

Preventive measures include eradication of ticks and rodents and use of insect repellents (acaricides). The specific vaccine used against Omsk hemorrhagic fever results in prolonged and stable immunity.

REFERENCES

Smorodintsev, A. A., L. I. Kazbintsev, and V. G. Chudakov. Virusnye gemorragicheskie likhoradki. Leningrad, 1963.
Ugriumov, B. L. Klinika gemorragicheskikh likhoradok. Kiev, 1961. (Bibliography.)
Mnogotomnoe rukovodstvo po mikrobiologii, klinike i epidemiologii infektsionnykh boleznei, vol. 8. Edited by N. N. Zhukov-Verezhnikov. Moscow, 1966. Chapters 11 and 13.