Ixodidae Ticks in Tajikistan
Complex Study of Ixodidae Ticks - Tick-borne Rickettsiosis Natural Vectors and Recommendations Development on Regulation of Ticks Number in Central and Southern Tajikistan
Tech Area / Field
- ENV-EHS/Environmental Health and Safety/Environment
3 Approved without Funding
Institute of Zoology and Parasitology named after E.N.Pavlovsky, Tajikistan, Dushanbe
- Georgia Southern University / Institute of Arthropology and Parasitology, USA, GA, Statesboro\nSWORDE Teppa / Representative Office, Tajikistan, Khatlon
Project summaryTick-borne rickettsioses of man have been reviewed by Hoogstraal (1967) and acarine-borne rickettsioses of the Old world by Rehacek and Tarasevich (1988). The major rickettsial diseases which ticks transmit to man are various forms of tick typhus and, to a lesser extent, Q fever. Ticks serve as reservoirs of infection since the organisms which may be found in all the tissues are transmitted from generation to generation and transstadially. Various small and large mammals can serve as vertebrate reservoirs for these species of Rickettsia. Except for one or two infections, all the rickettsioses are zoonoses. As in the case of arboviruses and for essentially the same reasons, the tick-borne Rickettsiae occur sporadically in man. Transmission of Northern Asia or Siberian tick typhus (Rickettsia sibirica) to man is by tick bite. Transmission of Q fever (Coxiella burneti) is via tick bite or occassionally by contamination or inhalation from infected milk, urine, faeces and fetal fluids of infected animals. Tick typhus symptoms include; rash, eschar, severe irritation, severe toxicity of infection which can lead to gangrene. Q fever symptoms also include; fever, headache, chills, sweating, hepatitis, endocarditis and moderately severe pneumonia which is rarely fatal. Most patients with rickettsial infections recover with timely use of appropriate antibiotic therapy.
Diagnosis of ricketttsial disease is based on two or more of the following: 1) compatible clinical symptoms and epidemiologic history, 2) the development of specific convalescent-phase antibodies reactive with a given pathogen or antigenic group, 3) a positive PCR test result, 4) immunohistologic detection of a microorganism, or 5) isolation of a rickettsial agent. Ascertaining the place and the nature of potential exposures is particularly important for accurate diagnosis, as many rickettsial diseases have strong geographic links or are associated with exposure to specific animal reservoir species or arthropod vectors.
Tick rickettsiosis has been detected and reported in Tajikistan for some years; for example, Northern Asia tick typhus, also called Siberian tick typhus, (causative agent Rickettsia sibirica) and Q fever (causative agent Coxiella burneti). However, this data is based on old information and there has been no recent work on rickettsiosis, no diagnosis or treatment protocols and no data with health authorities on the diseases. A review of vector-borne infectious diseases in Tajikistan by Faulde included R. sibirica, and stated no epidemiological data from Tajikistan was available, but endemic in border areas of Kazakhstan, Pakistan and China. The same review also stated C. burneti status was uncertain but that there were cases of Q fever in Russian soldiers in Afghanistan and thus occurrence in Tajikistan was therefore likely.
To date, the most epizootiology and epidemiology problems of these diseases, especially in conditions of arid territories with hot continental climate; degrees of disease prevalence, rickettsia vectors and carriers, the role of livestock and wild animals as reservoirs of rickettsiosis and thus causative agents in its circulation, have not been detected. Ticks are the main vectors or rickettsiosis and able to transfer rickettsia both transphase and transovarian stages of development, which facilitates a longer period of potential infectious vectors in the natural and household foci of diseases. Ixodidae ticks have the most vital significance in rickettsiosis epizootiology and epidemiology for these reasons. Simultaneous existence of causative agents C. burneti and R. sibirica rickettsiosis in the same tick specimens is also possible in a tick population and vertebrate reservoir host animals thereby allowing combinations of natural foci of these diseases where detected. Humans can be infected by rickettsiosis during an attack of bloodsucking ticks or by contact with infected livestock, unpasteurized milk products and meat of these livestock and wild animals.
Species persity of Ixodidae ticks, existing in Tajikistan has been counted at 26 species and subspecies. The high number of these ecto-parasite vectors and their hosts create preconditions not only for existence but also for prevalence of rickettsiosis foci in Tajikistan. The main vertebrate reservoir hosts of the most zooanthroponosis are different species of rodents. 30 species of rodents (most ixodidae tick species are facultatively or obligatory parasites on them) are registered in Tajikistan. The most important causative agents for the disease circulation in the environment are mass populations of rodent species such as: Meriones libicus, Nesokia indica, Mus musculus, Apodemus sylvaticus and many others. The study of the role of livestock and rodents as a host of tick vectors and rickettsia carriers is the most important link in rickettsiosis border epizootiology and epidemiology. This role so far remains uninvestigated and therefore an urgent investigation is required.
The project will implement a multiplane, complex study of Ixodidae ticks, vectors and natural reservoir hosts of Northern Asia tick typhus (Rickettsia sibirica) and Q fever (Coxiella burneti) causative agents and determine roles of livestock and wild animals (rodents) as vertebrate reservoirs of these diseases, study biocoenosis and parasitocoenosis, rickettsiosis foci, elaboration of ecology and recommendations of control measures against Ixodidae ticks.
The project will identify the main species of Ixodidae ticks, vectors of rickettsiosis and their natural infections by rickettsiosis, as one of the main determination of disease sources. The project will also identify rickettsiosis carriers among livestock and rodents and the determination of the main rickettsiosis carriers and their role in maintenance of household and natural rickettsiosis foci in Tajikistan. Another innovation will be the study of Ixodidae ticks as possible natural, joint infections of Coxiella burneti and Rickettsia sibirica. The possible detection of joint rickettsiosis, Cb fever and Northern Asia tick typhus, as well as determining the reasons of origin, activities, and ability to irradiation of anthropogenic and natural rickettsiosis foci by constructing nosomaps, will serve as a foundation for disease predictions, rickettsiosis prophylaxis and method of control in arid regions in Tajikistan and neighbouring countries.