Leptospirosis in Murmansk Region, 1990 - 1999
Published: 24.11.05 Updated: 21.02.2006 09:37:35
A.V. Chernev, E.A. Matsievskaya, T.M. Lisseeva
Regional State Sanitary and Epidemiological Control Centre, Murmansk, Russia
Analysis of leptospirosis morbidity is essential to study the epidemiological situation, and to analyse the effectiveness of preventive measures. In the study we used statistical and notification data from 79 epidemiological investigation-cards. We investigated the sporadic or group-character of the disease, the information about vaccination of the patients, the mode and factors of transmission of the agent and the datum of the first visit to the medical services due to leptospirosis as well as the datum of the diagnosis confirmation and an interval between laboratory analysis and the moment of the first visit, a preliminary diagnosis, forms and severity of the clinical manifestations of the disease, timeleness and quality of the epidemiological and zootological investigations.
Patients were examined serologically using microscopic agglutination test (MAT). Patients with titres higher than 1: 100 and similar clinical symptoms were observed once. Persons with clinical and epidemiological indicators with negative MAT or titres lower than 1:100 in the first sera, were observed twice in the dynamics. Totally 97% of the patients were examined with serological method, including 46% who examined twice. In two mortal cases the diagnosis was confirmed by authopsy, including one case with histological confirmation. In two patients with negative serological results, the diagnosis was confirmed by clinical and epidemiological data.
During the 10 years of observation, 79 cases of leptospirosis were registered, 4 of which with a lethal outcome (5%). A low level of severity was observed in 12.6%, medium severity in 45.6% and a heavy severity in 41.8% of the cases. 15 (18.9%) of the patients had jaundice-form, 13 (16.5%) had meningial form and 14 (17.7%) - renal lesions. The preliminary diagnosis were as follows: leptospirosis – 41%, yersiniosis - 21.5%, hepatitis in 20.2%, influenza in 20.2%, acute respiratory infections in 16.5%, meningits or encephalitis in 11.4%, renal disease in 5.1% and others in 11.4%. 58,2% of the leptospirosis cases were registered in Murmansk City. 57% of the patients were men and 43% women. 54% of the cases were registered in autumn – winter season with the peak in October – November.
Fig 1. Leptospirosis morbidity dynamics
Table 1. Leptospirosis age distribution
Table 2. Leptospirosis morbidity by patients’ occupation
Leptospira canicola predominated in the etiological structure (53.6%). L. icterohaemorrhagiae was recovered in 26.2%, L. pomona – 14.3%, L. javanica and L. tarassovi in one case. Among agricultural and subsidary workers L. icterohaemorrhagiae and L. pomona were dominant, among persons with occupations not related to risk of infection - L. canicola. None of the patients, included persons from risk-groups were vaccinated against leptospirosis. Sources of leptospirosis infection: farming animals – 19.1%, dogs – 48,1% rats – 2,5% and unknown – 30,3%.
In 74.6% of the cases, the place of infection was the city, in 22.8% - rural areas and in two cases the place of infection was not established. 8.9% of the cases were imported. Mode of transmission by contact was established in 64.4% of the cases, food-products in 5.1% and water in 3.7% of the cases. 26.6% of the cases were not determined.
Discussion and conclusion
The high incidence of leptospirosis in September 1995 – January 1996 was related to the epizootic of leptospirosis among dogs in Murmansk from September 1995 to January 1996. In 1995 – 1996 there were over 7000 dogs vaccinated against leptospirosis in Murmansk City.
Considering the topicality of the disease, its severe clinical course and high lethality, the epidemiological surveillance of leptospirosis should be continued with emphasis on investigation and vaccination of risk-groups. The common efforts with the veterinary services should be continued.